DE102013019660A1 - Sensor system for optical measurement of biometric parameters of animal or plant or human, has first transmitter, second transmitter and receiver, where first transmitter is operated with first feed signal of signal generator - Google Patents

Abstract

The sensor system has a first transmitter (H1), a second transmitter and a receiver (D1). The first transmitter is operated with a first feed signal of a signal generator (G1). The second transmitter is operated with a second feed signal. A course of intermediate signal (S4) is evaluated such that the biometric parameter of the signal is extracted.

Description

introduction

The pulse-oximetric measurement of biometric parameters is a well-known method to measure the heart rate of patients and the oxygen content of the blood as well as other parameters that can be detected by the skin spectroscopy.

The method is based on the measurement of light absorption or light remission in a percutaneous transillumination of the skin at different spectral wavelengths to capture various parameters.

In 1935 K. Matthes described such a measurement on the human earlobe without reaching the status of applicability. Takuo Aoyagi realized the first usable device and method. The method was first published by Christian-Peter Bernhardt in 1978 under the name of photoplethysmography.

According to this prior art is measured with a saturation (clip or adhesive sensor) on an easily accessible body part, preferably on a finger, toe, on the earlobe or in premature infants also on the ball of the foot or wrist.

The method uses a device, the two in a defined (infrared) red area (see below) glowing transmitter on one side of the DUT, typically the said fingers, earlobes, etc., and on the other side of the DUT a receiver, typically having a photodiode. The hemoglobin has a different absorption spectrum depending on the degree of oxygen saturation. This oxygen saturation dependent spectrum changes the relative absorption of the two frequency bands radiated by the two said LEDs. At the same time, the absorption also depends on the perfusion of the irradiated tissue. In addition to saturation, the pulse in the smallest blood vessels (capillaries) is therefore recorded via the clip or adhesive sensor.

Typically, the absorption of the light is measured with one LED at 660 nm, a second LED at 940 nm. In addition, the light radiation is measured and subtracted by the ambient light.

One possible application is the use of this technique as a driver condition monitor in automobiles. Even in the field of mountain climbing, pulse oximeters are being used more and more frequently in order to obtain early indications of an impending altitude sickness.

Known measuring errors

With painted fingernails, light is absorbed by the paint and reaches the photocell only attenuated.

Artificial fingernails made of acrylic also lead to measurement errors depending on the pulse oximeter.

In patients with reduced peripheral capillary blood flow (for example, shock and hypothermia), false readings may be displayed or pulse oximetry may not be possible.

In mechanical shock, z. B. when driving over uneven terrain, errors occur by changing the measuring arrangement and change the ambient light.

This problem is solved by the device according to the invention.

Disclosed prior art

Such a system was used for example in the DE3135802A1 disclosed.

The DE3135802A1 claims a pulse monitoring system for detecting and displaying the blood pressure pulses produced by the heartbeats, characterized by a sensor device that can be positioned in contact with body tissue to respond to changes in blood volume, the sensor device including a detector device and at least two light emitters, one of which is a light transmission emitter arranged to radiate light through the body tissue to the detection means, and the other is a light reflection emitter arranged to reflect light therefrom to the detection means, said detector means detecting changes in the transmitted and reflected light resulting from changes in tissue perfusion and producing an electrical signal in response to said changes, and signal processing means for converting said electrical signals into the pulse rate l. An important point is that the sensor device must be in contact with the tissue, since the scattered light would otherwise cause too low a signal to noise ratio. It is thus ambient light dependent.

The DE3405444A1 claims a pulse sensor with an optoelectronic pulse pickup, containing a light source and a photosensitive device, which are optically coupled together via a beam path in which a sufficiently translucent, perfused body part can be arranged, so that the photosensitive device provides an output signal of its irradiance and thus by light transmission of the body part Is characterized in that the light source, the photosensitive device and the optical path coupling them are in a control loop, which strives to keep the illuminance of the photosensitive device constant, but has such a large time constant that it changes the illuminance caused by Pulse-related circulatory fluctuations of the body part are caused, not able to correct.

An essential point of this system is that the sensor device must be in contact with the tissue, since the scattered light would otherwise cause too low a signal to noise ratio. In contrast to the previously discussed system, however, the illuminance is readjusted here. This readjustment takes place electronically. Sensor drift or sensor contamination can not be compensated.

The revelation DE69113785T2 claims a monitor having an optical sensor for determining the pulse rate by photoplethysmographic (PPG) measurement of the blood circulation of a subject, such as a human or animal body part, with a light source, preferably a laser diode or a light emitting diode (LED), a detector unit, which determines the AC component or AC component, of a generated PPG signal to determine the heart rate of the subject, an electronic amplifier unit, a presentation unit, for example an oscilloscope, a display unit or a printer, by a Means for separating a signal component from the determined PPG signal indicating the respiratory rate of the subject.

This system also requires that the sensor device must be in contact with the tissue, since the scattered light would otherwise cause too low a signal to noise ratio.

The publication DE69122637T2 describes with the help of the 2 B this document DE69122637T2 on their page 6 is a schematic representation of a conventional pulse oximeter. The finger of a patient is surrounded on said figure by a finger cuff comprising a red LED and a near infrared LED (NIR LED) and a detector. The LEDs and the detector are coupled by lines to a processing and control circuit that measures blood pressure based on the amount of red and NIR radiation detected by the detector.

This system is thus very similar to the origin disclosure DE3135802A1 and has all its major drawbacks.

The font DE102008022920A1 claims a device for detecting lifelessness of a person on the basis of pulse measurement and / or movement, wherein at least one optical sensor consisting of an emitter for emitting light to a skin tissue and a detector for receiving the remit of the skin tissue light and an evaluation unit are provided wherein light emitted by the emitter of the optical sensor with a wavelength from a predetermined range of 520 nm to 600 nm and wherein a light emitting diode with a dominant wavelength from the predetermined range and as a detector, a photodiode or a phototransistor are provided as emitter and wherein the emitter and the detector are arranged directly next to each other.

Also, this system is very similar to the origin disclosure DE3135802A1 and has all its major drawbacks. However, in contrast to the previous systems, it refers to a measurement of the reflected light.

The US American font US4,258,719 claims a pulse rate measuring system that, during the measuring pulse intervals, receives a pulsed photocurrent signal containing an ambient light-induced signal component and the pulsed photocurrent portion of a carrier signal whose amplitude has been modulated by the cardiac blood pressure signal to provide said cardiac blood pressure signal via an output unit; wherein the pulse rate measurement system comprises a sensor having a pulsed light source and a photodiode having an anode and a cathode, the cathode coupled to a first reference potential and the anode providing said pulsed photocurrent and a cancellation signal for eliminating the ambient light signal within the pulsed photocurrent directly into the anode during which the pulse interval is coupled and has a first integrator coupled to said ambient light compensation and receiving and integrating the pulsed photocurrent during the measurement pulse intervals chert, and has a feedback loop which lies between the output of said integrator and the anode of the photodiode. (Text shortened)

In contrast to the previous writings, the ambient light is taken into account here. The compensation is done electronically directly at the anode of the photodiode by an electronic generated signal. A drift compensation of the sensor does not take place.

The publication US4,260,951 claims a pulse rate measurement system for receiving a pulsed photocurrent during a measurement pulse interval. The pulsed photocurrent contains an ambient light signal and a reflected light signal. The reflected light signal is amplitude modulated by the cardiac blood pressure. The pulse rate measurement system includes a signal processing unit that processes the said photocurrent signal and includes a second order feedback loop. This feedback loop contains a first differentiator. This has a transfer function which has a high pass pole at a first frequency. An erasure is generated by generating a zero at said first frequency to cancel the high-pass pole of said transfer function. The feedback loop further includes a second differentiator coupled to said cancellation by forming a high pass pole at a second frequency. In addition, the measuring rate system has an additional pulse shaping and output of a pulsed photocurrent signal by coupling to the said second differentiator by means of the measuring pulse intervals.

Essentially, this document again describes a system accordingly DE3135802A1 with all the major disadvantages

All systems have in common that they are sensitive to extraneous light. The only exception is the US4,258,719 , However, it has an electronic compensation that does not suppress the drift of the sensor due to soiling, aging, humidity and temperature.

Finally, to call the US5,774,213 , This describes in 4 of the US5,774,213 a compensated system. This solves many of the problems of the previous systems. However, this happens only imperfectly. In particular, it is not a linear system with corresponding consequences. The system of US5,774,213 works only because a bandpass is inserted in the feedback branch. This reduces the signal components of the receiver signal to the frequency components which correspond in frequency to the frequency of the transmitted signal. This is followed by a mix with the transmit signal, at which, as the authors rightly noted, an equal value, but, and this is not noted in the application and discloses quite essential, just typically also twice the frequency of the transmit signal frequency in the mixer output signal arises. This parasitic component of double frequency is amplified in an amplifier as well as the DC component and then logically multiplied the transmission signal. Thus, the signal routed to the transmit diodes includes transmit signal frequency portions which are proportional to the mixer output signal balance, and parasitic portions, also at transmit signal frequency, which are proportional to half the value of the mixer output signal portions and which are twice the transmit frequency. In addition, this signal contains shares at three times the transmission signal frequency. This last point is irrelevant because the bandpass filter eliminates this signal component. Without the bandpass filter, this proportion would lead to any problems, leading to complete uselessness. The parasitic components with transmission signal frequency in the signal fed to the transmitting diode lead to disturbances of the measurement result. The inserted bandpass is thus ultimately only a stopgap. In the context of the conception of the method according to the invention, it was therefore recognized how a correctly functioning system, in contrast to the system of the US5,774,213 must be structured. This is described below.

These parasitic components with transmission signal frequency represent the essential problem of US5,774,213 which is, however, solved by the device according to the invention.

The through the device of US5,774,213 Realized link between transmit signal and received signal is just not a linear form but corresponds to a cubic polynomial. The basic signals of US5,774,213 thus do not form an orthogonal basis. A superposition of different channels is therefore not possible even at different frequencies without mutual interference. Therefore, a technical solution according to the US5,774,213 sensitive to a DC signal (extraneous light), albeit to a lesser extent.

Due to the external light sensitivity, all systems have mechanical devices which are intended to shield this extraneous light and provide for direct mechanical contact between the measuring system and a body part, typically a finger.

For many applications, however, it is advantageous if such shielding of the extraneous light would not be required. The housing shapes would then be freely selectable. Such a sensor could then be installed, for example, in a mobile phone or other electronic device.

Also, the use in the form of flat measuring heads is not readily possible, which could be used in places other than the human finger.

The absence of extraneous light robustness thus determines as an essential form of the mechanical construction for devices of the prior art, that of a tube or at least the two more or less half-shell-shaped clamps. The sensors are arranged radiating inwardly on the resulting during closing of the clip tubular object inside. For some applications, however, it would also be useful to be able to attach the sensors radiating outward. This is not possible due to the lack of extraneous light robustness.

The present invention relates to a sensor system having at least one transmitter and one receiver for measuring the transmission properties of a transmission path between a transmitter and the receiver for determining at least one biometric parameter. The transmitter sends a transmission signal in the transmission path, which is detected after passing through at least a part of the first transmission path from the receiver. The receiver receives the transmission signal and, in particular by forming a linear form, forms a receiver output signal which is processed further in a processing unit. Information about the properties of the first transmission path and thus about biometric parameters of a measurement object is obtained from the receiver output signal. For example, the presence of an object or certain, in particular biometric properties of an object can be detected.

Such optical sensor systems can be disturbed by interference radiators, such as fluorescent tubes or the sun. These narrowband interferers can falsify the measurement results if their interference is in the range of the transmission signal. If the interferer and its interfering radiation are known, an attempt can be made to place the operating frequency of the transmission signal outside the range of the interferers. If this is not possible because the interferer is not known or appears only sporadically, it will be possible to try to search for a working frequency by means of so-called frequency hopping, in which undisturbed operation of the sensor system is possible. However, these methods are not or only insufficiently suitable for some fields of application.

Object of the invention

It is the object of the invention to enable an external light-independent measurement of the heart rate and other biometric parameters, such as the blood oxygen content by measuring spectral properties by means of radiation or reflection without body contact between the measuring instrument and the body is required and at the same time a greater variability of the housing enable and compensate for sensor drift or contamination. At the same time, the device according to the invention should have the highest possible linearity and disturbances optimally, in particular better than those in the US5,774,213 Suppress compensation described.

This is achieved with a device according to claim 1 or 2.

Disclosure of the invention

Through the use of two compensation transmitters, the receiver, typically a photodiode, is held in its operating point by two regulators which use a linear form. Furthermore, it makes sense to prevent an override of the recipient. This can be done for example by a gyrator.

In the context of the invention, it has been recognized that, to date, a modulated signal has generally been used to measure the transmission characteristics of a transmission path. The modulated signal comprises a generally optical carrier wave with two carrier frequencies which are undefined, but in any case broadband. A feed signal of one or more transmitters is then modulated onto these optical carrier signals. The feed signal forms the envelope of the respective modulated transmit signals. It has been recognized that in the prior art exclusively feed signals are used which are narrow-band or monofrequent. Thus, the envelope of the transmitted signal results from the narrowband or monofrequent feed signal. The modulation frequency is therefore also narrowband or monofrequent.

The sensor system according to the invention selects a completely different approach. A transmitter according to the preamble of claim 1 emits at least a portion of a spectrum of electromagnetic radiation in at least two predetermined wavelength subregions. The emission of the electromagnetic radiation takes place in each case as a carrier wave. In this case, the emission intensity of the at least two wavelength subregions is regulated by means of a signal. The emission intensities of the wavelength subregions are controlled in opposite directions such that at least radiation of one of the at least two wavelength subregions can be emitted. In particular, predominantly radiation is emitted in each case in only one of the at least two wavelength subregions. It is therefore preferable to switch between the two wavelength subregions. Particularly preferably, the wavelength subregions each correspond to a spectral region, in particular a color, preferably in the optically visible range or in the non-visible range z. B. in the infrared or UV range. It is thus transmitted with at least two different carrier signals, each having a different wavelength subrange. If we speak of a color in the following and here, it means a single spectral emphasis. This can also be outside the visible spectral range.

The receiver of the sensor system according to the invention is so sensitive that it can receive the intensity of the electromagnetic radiation in at least the at least two wavelength subregions of interest. The processing unit further processes the receiver output signals based on the at least two wavelength subregions and derives therefrom information about the transmission characteristics.

The present invention also makes it possible to perform frequency hopping. However, the frequency hopping does not take place in relation to the modulation frequency, but to the carrier frequency. In the concrete example, this means that it is possible to switch back and forth between the two different wavelength subareas. Thus, the optical carrier frequency of the transmitted signal is changed.

In a preferred embodiment, the transmitter emits electromagnetic radiation in exactly two wavelength subregions. For example, you can switch between two different colors here. The emitted electromagnetic radiation thus has two different carrier wavelengths, which may be visible, for example, as red or green light. Supply signals can be modulated onto these light signals.

More preferably, more than two wavelength subregions can be emitted, for example four, six or eight. The emission of the electromagnetic radiation preferably takes place in the wavelength subregions having a wavelength subrange of specifically controllable intensity.

As already known from the prior art, for example, two LEDs with 660 nm and 940 nm emission center are suitable for pulse oximetry.

In an equally preferred embodiment, the wavelength subregions each correspond to one color. It is also of interest to measure the color of the skin in different wavelength ranges. For example, it is of interest to a physician to be able to detect the color of the tissue under the skin independently of the individual pigmentation. As a result, for example, moles of melanoma can be distinguished. This is possible to some extent by using different colors or spectral focuses of the transmitters. The transmitter then emits two separate color signals (spectrally different signals), wherein by means of a switch between the two color signals is switched, so that, for example, only one color signal is emitted at any time. The receiver is designed in this case exactly for the detection of the intensity of the two color signals. The processing unit then processes the receiver output signals based on the two color signals and obtains information about the transmission properties of the transmission path or of the object to be measured.

As an alternative to a changeover switch, which switches the sections back and forth, a controller or a control circuit can also be used. This additionally or alternatively allows the adjustment of the intensity in the individual wavelength subregions. The control circuit may be integrated in the transmitter, z. B. in an ASIC or the board for the transmitter control and / or supply. The control circuit can also be a separate unit or integrated into a generator.

Preferably, the transmitter comprises at least two transmitting elements, each of which emits a signal with a specific wavelength. The emitted carrier signal is particularly preferably a color signal whose wavelength lies in the optically visible, infrared or UV range. The two transmission elements are typically alternately active, wherein the transmission elements can be, for example, light-emitting diodes (LED).

In a preferred embodiment, the transmitting elements of the transmitter for each wavelength range, preferably for each color signal, send out a total of constant luminous flux. The emission takes place in such a way that the imitated energy quantity is substantially equal to the sum of the radiation of all the transmission elements or that the sum of the receiver signal amplitudes which are based on the respective transmission elements is essentially the same. Thus, the signal components in each wavelength sub-range can be controlled so that the receiver results in a constant receiver signal, preferably the receiver signal can be controlled to zero or to a constant level, especially if the signal components in one of the two wavelength subregions inverted to the other signal component are.

In a further preferred embodiment, transmitting elements transmit different Transmission wavelength, which together form the transmitter, for each wavelength range, preferably for each color signal, a modulated with a first feed signal luminous flux. The emission takes place in such a way that the emitted energy quantity of the sum of the radiation of all these transmission elements is essentially modulated with the said first supply signal. The ratio of the amounts of energy emitted by these transmitting elements to each other is determined by a second feed signal. Thus, the signal components in each wavelength subregion can be controlled such that a receiver signal modulated with the first supply signal results in a receiver which is equally sensitive to all wavelengths. By means of a compensation transmitter which likewise comprises compensation transmission elements corresponding to transmission wavelengths, the receiver signal can preferably be regulated to zero. This is the case in particular when the compensation signal components of the compensation transmitter in one of the two wavelength subregions are inverted to the corresponding other signal component of the transmitter.

In a preferred embodiment, the transmitter comprises a multi-wavelength LED which emits electromagnetic radiation in at least two different wavelength subregions. Preferably, the multi-wavelength LED is controllable, in particular controllable so that the individual wavelength subregions can be controlled separately and that preferably their intensity can be controlled.

Thus, the sensor system according to the invention performs, as it were, a two-dimensional spectral analysis, which makes it possible to separate the sensor system from the surrounding interference radiators. If the spectral analysis is extended by a pulse-code modulation, there is a significantly good separation of surrounding interference radiators. This has been made clear in the context of the invention.

In a preferred embodiment of the sensor system according to the invention, the receiver comprises at least two, preferably at least four receiving elements, of which at least two, preferably a plurality, each have a different spectral sensitivity profile. The receiving elements are therefore sensitive to a particular spectral range, thus for a particular wavelength subrange. Preferably, the receiving elements are photodiodes or other diodes. They are particularly preferably receiving elements spectrally different sensitive photodiodes.

The receiver elements of the receiver can, for example, also form a receiver element array, for example a receiver spectrometer. It is also possible to use a spectrometer based on a CMOS technology. In this case, the receiving elements are formed in CMOS technology. This is done for example by a metalloptic filter.

Particularly preferred is the receiver or its receiving elements, which is made of silicon together with an evaluation circuit, for example in CMOS technology.

Therefore, a receiver is preferred which is sensitive in the range of visible and / or infrared radiation and / or UV radiation. The preferred wavelength subregions in this case are between a wavelength λ of approximately 300 nm to 790 nm and / or up to 1100 nm and / or of 100 nm. Each of the wavelength subregions preferably corresponds to one color, including infrared and UV.

If other wavelength ranges are to be used, a material other than silicon must typically be used for the receivers. The use of other wavelength ranges is therefore possible. Such materials may be III / V compounds and II / VI compounds or other materials of the 4th main group.

In a preferred embodiment, the sensor system can be designed as a compensating measuring system in which the actual transmission signal is superimposed on a compensating signal at the receiver so that the sensor or receiver receives a nearly constant signal in total. Preferably, the sensor system comprises a compensation element, for. B. a compensation transmitter, which transmits a compensation signal in a second transmission link, which is detected by the receiver after passing through the second transmission link. The compensation transmission element may preferably be one of the transmission elements of the transmitter. The compensation transmission element may be, for example, an LED and is then referred to as a compensation LED or compensator.

The receiver receives the transmit signal of the transmitter and the compensation signal and superimposed on them, preferably linear and / or summing. From this, the receiver output signal is formed, which is further processed in the processing unit to a Kompensatorspeisesignal. The compensator feed signal is supplied to the compensation transmitter for feedback control of the receiver output signal so as to convey information about the transmission characteristics of the transmission path.

Of course, it is also possible that the second transmission link, in which the Compensation transmitter sends the compensation signal corresponding to the first transmission path. Thus, the first and second transmission paths are the same.

An essential distinguishing criterion of the present invention with respect to the optical measuring methods known in the prior art is that the optical carrier frequency of the carrier wave is preferably narrowband. Optionally, it is composed of several narrowband frequencies. The modulation frequency can be arbitrary; it is preferably narrowband. But it can also be broadband.

This results in different configurations between transmitter and receiver. For example, the modulation frequency of the modulated signal of the transmitter may be broadband. In this case, the receiver can be made narrowband so that it receives on certain, narrowband wavelength subregions. The receiver is thus sensitive in a narrowband region of the carrier wave, for example, precisely for a particular color, e.g. B. for green.

In addition, the modulation frequency of the transmitter may be narrowband, as well as the optical carrier frequency. The receiver can then also be narrow-band sensitive. Alternatively, it is possible that the receiver is broadband sensitive. The narrowband and broadband sensitivity always refers to the carrier wave of the transmitted signal, to which the feed signal of the transmitter is modulated.

In a preferred embodiment, the transmitted signal, to which the transmission signal is modulated, is in the optically visible range. The carrier light wavelength is then approximately between 380 nm and 790 nm. This corresponds to an optical carrier frequency in the range of 3.8 × 10 ¹⁴ Hz to about 8 × 10 ¹⁴ Hz. When using infrared radiation, the frequency range expands to approx. 3 × 10 ¹⁴ Hz. With UV radiation, the frequency range expands to 3 × 10 ¹⁵ Hz

An essential difference from the prior art, in which only one measured value is always determined, is that in the method according to the invention or in the method implemented in the device according to the invention, amplitude and color angle can be detected and regulated separately. In contrast, the devices in the prior art rely on the maintenance of a well-defined distance and a given geometry, as they are not able to do so. In contrast to the prior art, a device such as the device according to the invention can thus regulate and measure amplitude and color angle separately. In a mechanical disorder, as may occur, for example, in the transport of patients by impact, therefore, the amplitude is readjusted, but not the color angle. The color angle signal typically remains trouble-free. Also, the device can be used in mobile phones without a defined distance to the object. It no longer necessarily requires a mechanical clip for stable attachment of the measuring device, for example on a finger. Prior art devices are therefore not suitable for use in mobile systems such as mobile phones.

The method according to the invention is a method for measuring the transmission characteristics of a first transmission path of a feedback system based on a compensation system or sensor system between at least one transmitter and at least one receiver for determining a biometric parameter has a transmitter, which transmits a signal in the transmission path after passage is detected by at least a part of the first transmission path from the receiver. A compensation transmitter sends a compensation signal into a second transmission path which is detected by the receiver after passing through the second transmission link. In the receiver, the transmission signal and the compensation signal overlap linearly, in particular summing. From this, a receiver output signal is formed, which is further processed to a Kompensatorspeisesignal for feeding the compensation transmitter. The compensator feed signal is supplied to the compensation transmitter for feedback control of the receiver output signal.

The method according to the invention comprises the following steps: First, at least part of the spectrum of electromagnetic radiation is emitted in at least two predetermined wavelength subregions by means of the transmitter. In accordance with a method step, the transmission intensity in the at least two wavelength subareas is regulated by means of at least one signal (control signal) in such a way that, in particular, it is also possible to control in opposite directions. In this way, radiation of one of the at least two wavelength subregions can be emitted. The subareas can z. B. be individual colors. It can then be switched back and forth between the subregions by means of a regulator or a switch. A further method step comprises receiving at least the intensity of the electromagnetic radiation in the at least two wavelength subregions of interest. This is preferably done by means of the receiver, which is sensitive at least for the two wavelength subregions of interest. Furthermore, receiver output signals are formed which are applied to the at least two wavelength subregions are based. The receiver output signals are further processed to a Kompensatorspeisesignal in a next step using a linear form and obtained from the receiver output signals information about the transmission characteristics of the transmission path in particular a biometric parameter.

Particularly preferably, the further processing of the receiver output signal to the compensator supply signal by means of a linear form comprises multiplying the receiver output signal by the feed signal and forming a detection signal, which is filtered in a further step in a filter, so that a projection image signal is generated as a filtered filter output signal. Here, the signal is transformed into a new signal in a Hilbert space (forward transformation). The steps of forming an output signal based on the projection image signal and performing at least partial inverse transformation of the output signal with the feed signal such that a pre-signal is formed, follow. The inverse transformation is preferably carried out as a multiplication with the feed signal. From the presignal, the compensator supply signal is then generated, with which the compensation transmitter is fed for feedback control.

In this case too, electromagnetic radiation is preferably emitted in exactly two, more preferably in more than two different wavelength subareas, which may have a specific controllable intensity. The wavelength subregions preferably correspond to one color, wherein preferably two separate color signals are emitted. The regulation of the transmission intensity of the two wavelength subregions represents a switching between the two color signals, which preferably takes place by means of a changeover switch. At that time, preferably only one color signal is emitted. The intensity of the two color signals is detected in the receiver and the color signals based receiver output signals are further processed.

Preferably, the method is carried out by means of multi-wavelength LEDs or by means of two transmitting elements of a transmitter, wherein the transmitting elements each emit a color signal and are alternately active. The transmitting elements are preferably light-emitting diodes. Of course, it is also possible to form one of the transmitting elements as a compensator, in particular if the transmitting elements are LEDs. The compensation LED may be one of the transmission elements, while the transmission LED or the transmission LEDs are the other or the other transmission elements. Different colors can also be used for transmission here.

The invention will be explained in more detail with reference to specific embodiments shown schematically in the figures. The peculiarities illustrated therein may be used alone or in combination to provide preferred embodiments of the invention. The described embodiments do not limit the invention defined by the claims in their generality. The figures are only schematically executed so far that a person skilled in the art can grasp the basic idea.

Show it:

1 the block diagram of a single channel to explain the scheme;

2 Parts of the system 1 and the controller CT with its typical components to explain the control algorithm in reflection measurement on the object;

3 an alternative embodiment of a sensor system as in 2 but now with a radiation of the object;

4 The complete system consisting of measuring head 1 , Generator G1, controller CT and evaluation 2 The measured value A is output.

5 An exemplary case

6 an exemplary housing from above

7 an exemplary housing from the side

8th exemplary signals, here for a heart rate measurement

9 single-channel system whereby the object is also passed through the compensation beam S23 (as opposed to 3 )

10 Inventive system as an example of how individual channels are combined to form a system according to the invention. Here a system with a transmitter ( 200 ) consisting of several sub-stations ( 201 . 202 )

11 Inventive system with two transmitters H1 and H2 at different wavelengths and two photoreceivers D1, D2, also at different wavelengths and two associated compensation transmitters K1, K2, wherein by a Koordinatenhin and -rücktransformation Amplitude and color angle can be controlled separately and measured.

1 shows the simplest exemplary embodiment of the system of a single channel. The drawing serves to illustrate the basic principle. For a system according to the invention, at least two channels are required. This will be described later in more detail. A generator G1 generates a feed signal S5. With this a transmitter H1, typically an LED, is controlled. This radiates into a first transmission link I1. At the end of this transmission link I1 is the object T1. This is typically an exposed skin area of the patient. This reflects the light coming from the transmitter H1 via a second transmission path I2 to the receiver D1. This converts the signal modified by the two transmission links (I1, I2) and the object (T1) into the receiver output signal S0. Typically, this signal corresponds to the voltage dropped across a photodiode. The receiver output signal S0 is transformed by a controller CT into the compensator feed signal S3 and the output signal S4. With the Kompensatorspeisesignal S3, the compensation transmitter K1 is fed, which also radiates over a defined and typically unchangeable, so stable, third transmission path I3 in the receiver D1. In this case, the radiation component of the transmitter H1 and the compensation transmitter K1 in the receiver D1 preferably superimposed linearly. The transmitter H1 radiates as exclusively indirectly as possible into the receiver D1, while the compensation transmitter K1 radiates as directly as possible and as far as possible does not interact with the object O1. The controller CT1 is in this case configured so that a fluctuation of the radiation component attributable to the transmitter H1, which strikes the receiver D1, is compensated by an opposite variation of the radiation component of the compensation transmitter K1. The receiver D1 therefore typically receives only a DC signal at such a closed loop. This is a significant difference to US5,774,213 , which, as described above, just not only generates a DC signal as a control signal, but also generates control signal components with a double transmission frequency.

Deviations arise in the system according to the invention in contrast only by the system noise and any control errors. The internal control signal S4 represents an intermediate signal, from which a biometric parameter, for example the pulse frequency, can be obtained.

2 shows a typical and exemplary embodiment of a controller CT. This is shown in dashed lines. The receiver output signal S0 is optionally amplified to the amplified receiver output signal S1. The gain can therefore be 1 here. The signal S1 is multiplied by the feed signal S5. As a result, all DC interfering signals in the frequency spectrum are shifted to the S5 signal frequency by adding the S5 signal frequency.

The signal components of the amplified receiver output signal S1, which correlate with the feed signal S5, are shifted to f = 0 Hz. However, they are also found at the double S5 signal frequency. Subsequent low-pass filtering removes all higher frequency components, but in particular the transmission frequency itself and twice the transmission frequency. It is particularly favorable, but not absolutely necessary, when the filter signal allows all frequencies below half the feed signal frequency to pass through and blocks all overlying signals. Other cut-off frequencies are conceivable.

This is the main structural difference to US5,774,213 , which instead of this low-pass has a bandpass at another point in the control loop and as discussed therefore has a lower system performance. This deficiency was recognized in the course of concept development of the device according to the invention.

Mathematically, the signal processing according to the invention corresponds to a linear form, specifically a scalar product between the signal S5 and the amplified receiver output signal S1 and thus the receiver output signal S0. Other linear forms are also possible.

By this operation, a so-called Hilbert projection of the amplified receiver output signal S1 to the feed signal S5 by means of a linear form and in particular by means of a scalar product by signal multiplication to the detection signal S10 and low-pass filtering to the signal S9, quasi the Fourier coefficient of the feed signal S5 in the amplified receiver output signal S1 determines. It is thus a transformation of a part of the receiver output signal S0 into the feed signal space or S5 space. Other filters are possible. It is important that the filter used is linear and does not let through the transmission frequencies and their doublings.

This filter output signal S9 is then amplified by the amplifier V1 to the output signal S4. Typically, the gain v of the amplifier V1 is chosen to be relatively high. The sign of the gain v is chosen so that the control loop is stable later. The output signal simultaneously represents the intermediate signal S4, the for example, for the determination of the heart rate or other biometric parameters is evaluated.

The thus obtained amplifier output signal or intermediate signal S4 is transformed back into the original space by multiplication with the S5 supply signal. The result is the advance signal S6. This is optionally provided with an optional offset B1 by addition to Kompensatorspeisesignal S3. This feeds the compensation transmitter K1, which, as already described, due to the parameterization of this control loop compensates for fluctuations in the radiation component of the transmitter H1 when it is received by the receiver D1.

By means of this method, with the aid of a linear form, increased extraneous light robustness is achieved. This is a significant difference to all prior art documents. This extraneous light robustness is further improved in the case of a photodiode by using a gyrator for operating point adjustment of the photodiode.

3 shows another exemplary embodiment of a channel of the invention. In contrast to 1 the object, for example a finger, is now irradiated.

4 schematically shows the exemplary overall system of the invention. The exemplary measuring head ( 1 ) contains the said photodiodes (D1) and the LEDs (H1). Through an optical window, the radiation can enter and exit. The controller CT generates the intermediate signal S4 from the supply signal S5 of the generator G1. This is stored in the processing unit ( 2 ) to a measured value A, for example, of the heart rate or another boiometric parameter. One way of processing, for example, to determine the heart rate is that the unit ( 2 ) sets a cutting level in the signal S4 and measures the time between two pulses of the signal thus determined and outputs digitally or analogously - discretely or continuously.

5 shows a suitable exemplary mechanical embodiment of a measuring head of the device according to the invention.

In a lower housing shell ( 11 ) is a PCB ( 14 ) brought in. There are four LEDs on this PCB in this example ( 9 . 12 . 15 . 17 ) symmetrical about the exemplary photodiode ( 13 ) are mounted around. The LEDs ( 9 . 12 . 15 . 17 ) operate as a transmitter (H1) The LEDs can be operated simultaneously - synchronously or in frequency multiplexing - or sequentially. A fifth LED ( 8th ) is via an optical waveguide ( 10 ) with the photodiode ( 13 ) coupled. This photodiode ( 13 ), which forms the receiver (D1), is located in the center or symmetry point of the LED positions ( 9 . 12 . 15 . 17 ). The fifth LED ( 8th ) serves as compensation transmitter (K1). The PCB is with a lip ( 16 ) to which a ribbon cable for connection to the controller (CT) can be connected by means of a suitable plug and exposed lines on the PCB. On the PCB is a structured sunscreen ( 19 ). This has an inner ring ( 20 ) of the photodiode ( 13 ) optically from the LEDs ( 9 . 12 . 15 . 17 ) decoupled. The ring ( 20 ) prevents direct irradiation of the LEDs ( 9 . 12 . 15 . 17 ) into the photodiode ( 13 ). In contrast, the ring ( 20 ) a recess ( 7 ) for the light guide ( 10 ), which is the fifth LED ( 8th ) with the photodiode ( 13 ) optically coupled. In contrast, the other four LEDs ( 9 . 12 . 15 . 17 ) indirectly via the object (O) with the receiver, the photodiode ( 13 ) coupled.

Between this inner ring ( 20 ) and the outer ring of the sunscreen ( 19 ) are webs ( 18 ), which provides a direct optical coupling between the LEDs ( 9 . 12 . 15 . 17 ) to prevent over-radiation. The bridges ( 18 ) are simultaneously shaped so that they do not hinder optical coupling with the object to be measured. The whole thing comes with an optical window ( 5 ), which in its peripheral area ( 6 ) is shaped so that it rests light-tight on the ring. Preferably, the optical window ( 5 ) on the inside towards the LEDs to minimize the coupling. The inner surface of the window ( 5 ) is shaped so that the light of the transmitting LEDs ( 9 . 12 . 15 . 17 ) if at all possible then not to the recipient ( 13 ) is scattered. The window ( 5 ) is chosen so that it is in the spectral region of interest for the electromagnetic radiation of the LEDs ( 9 . 12 . 15 . 17 ) is permeable. Through a fixing ring ( 4 ), which has a circumferential lip ( 3 ), optical windows ( 5 ), Sunscreen ( 19 ), PCB ( 14 ) with the components and the housing lower shell ( 11 ) held together. The mechanical connection can be done for example via a snap closure. The lip ( 3 ) lies on the contact surface ( 5 ) light-tight.

6 shows the exemplary arrangement with the cover removed ( 4 . 5 ) from above. Between sunscreen ( 19 ) and the wall of the housing lower part ( 11 ) there is typically still a free space ( 21 ).

7 shows an exemplary cross section through the exemplary measuring head. A laying on of a finger ( 22 ) produces a changed reflection, here from the LED 9 to the photodiode. So that the photodiode covers the entire surface of the optical window ( 5 ) "Sees" is the sunscreen ( 19 ) is not pulled up to the optical window. This leaves a gap between the optical window ( 5 ) and sunscreen ( 19 ), which is so large that light from the edge of the optical window ( 5 ) can reach the photodiode. First As a result, the arrangement according to the invention is corresponding 1 possible.

8th shows an exemplary S4 signal ( 23 ) of a device according to the invention. It shows the heart rate. This signal is sent by the processing unit ( 2 ) into a switching signal ( 25 ) transformed. For this, the S4 signal ( 23 ) with a cutting level ( 24 ) compared. This conversion typically takes place in the processing unit ( 2 . 2 ) instead of. A different transformation than the 1-bit ADC conversion described here is of course possible depending on the application. The processing unit then measures the period and determines the heart rate.

Of course, the controller (CT) and the processing device ( 2 ) can also be realized by a DSP device with ADCs and DACs or PWMs. The compensator supply signal S3 can in particular also be a PWM-modulated signal, wherein different amplitudes are realized by different fact ratios. The inertia of the LED and parasitic capacitances, if properly designed, provide for smoothing. The frequency of the S5 supply signal should be much lower than the PWM frequency to allow safe filtering of the PWM frequency by the low-pass filter F.

In the context of the invention, as mentioned, it has been recognized that both a transmission measurement and a reflection measurement can be carried out with the method according to the invention. These can also be used, for example, in absorption spectroscopy. In various applications, such as chemical analysis, this type of spectroscopy is used. By the devices, such methods can be used in diagnostics, in crop cultivation and livestock.

For example, this applies to gas analysis, solid-state analysis and fluid analysis. In this case, the transmission spectrum is measured in comparison to the spectrum irradiated on a sample. Alternatively, the reflected spectrum is detected in comparison to them. It is of course conceivable to perform absorption measurements and transmission measurements in parallel. The transmission measurement provides an absorption spectrum which is characteristic of the physico-chemical conditions, for example in a tissue or material. The reflection measurement allows, for example, statements about the spectrum of near-surface skin and tissue layers of a human or animal.

It was, as mentioned, recognized that the sensor system according to the invention can also be used for transmission measurements. The transmitter, which is preferably a "sharp" wavelength LED, ie narrowband, generates a signal which is modified by an object in the transmission link, typically the patient, in the beam path of the transmitter. Typically, the wavelength, ie the optical carrier frequency of the transmitter is selected so that an optimal interaction between the object or the component to be determined takes place in the object in the transmission path and the transmission signal.

9 shows a measuring circuit with which, for example, the concentration of a gas -. B. Breathing air -, a fluid (eg., Blood) or a solid (eg., A finger) can be determined in a given measuring space. The measuring space with object corresponds to the transmission path T1 between the transmitter H1 and the receiver D1 according to FIG 1 ,

In the context of the invention it has been recognized that, as already mentioned, a transmission measurement can be carried out with the method according to the invention. For example, the concentration of a gas, a fluid or a solid in a given measuring space can be determined. The measuring space with sample corresponds to the transmission path T1 between the transmitter H1 and the receiver D1 according to FIG 1 ,

According to the invention, the transmitter 200 or the transmitting element 201 typically as a transmitting diode 203 , For example, transmission LED, formed with sharp wavelength. The transmitting diode 203 generates a signal which is modified by an object T1 in the beam path of the transmitting diode. Typically, the wavelength, ie the optical carrier frequency of the signal that the transmitter 200 emits, so chosen that an optimal interaction between the object T1 and the transmission signal S25 takes place. Such an embodiment of a single-channel gas sensor or diode spectrometer is in 9 shown. A device according to the invention requires at least two channels.

If, for example, the concentration of CO2 gas in the respiratory air is to be detected, the carrier wavelength of the transmitting diode must be 203 an absorption line of the CO2 molecule in the carrier medium (eg, air in the measuring chamber) correspond. In this case, the measuring space T1 filled with the gas sample would be the light of the transmitting diode 203 depending on the CO2 concentration. The particular problem of such a measurement is usually that very small attenuations and only very small concentrations are to be determined.

The receiver (receiver diode 204 ) 204 then converts the received light signal Transmission through the sample path, which corresponds to the transmission path, ie the measuring space T1, again into an electrical signal. A sensor system with a compensating controlled system now controls a second transmission element, which is the compensation diode, in such a way that its light is also received by the receiving diode 204 is received and the receiver output signal S1 of the receiver readjusted so that this results in a substantially constant value.

However, it is essential that this compensation transmitter (compensation diode 205 ) on a different carrier wavelength than the transmitting diode 203 is operated.

According to the invention, the carrier wavelength of the transmission signal S23 of the compensation diode 205 chosen so that by the transmission path alone, so no sample to be examined, no impairment takes place, which is substantially different than the impairment, that of the transmitter diode 203 emitted transmission signal S25 also through the transmission path alone, so without a sample to be examined learns. The impairments due to the transmission path include the carrier medium itself, for example air, or optical devices in the beam path between the compensation diode 205 and the receiving diode 204 such as lenses, fiber optic cables, mirrors or optical windows for beam steering. The only exception is the impairment of the object to be measured or the substance to be measured, as in the above example of the CO2 gas. The carrier wavelength of Kompensatorspeisesignals S23 is selected so that the sample as possible no interaction or at least a much lower interaction may take place. That of the compensation diode 205 emitted signal S23 thus experiences a significantly lower attenuation or stronger modification than the transmission signal S25.

As a result, the reference beam of the second transmitter, so the compensation diode 106 205 travel the same signal and only then in the receiver, here the receiving diode 204 , received.

Essential in this procedure is that the receiver 204 is sensitive to both carrier wavelengths, so for a sensitive to the carrier wavelength of the transmitting diode 203 as well as for the second carrier wavelength of the compensation diode 205 ,

One of the essential features of this embodiment of the invention is therefore that the Kompensatorspeisesignal the compensation diode 205 in its properties is chosen so that its interaction with the measured properties of the transmission path T1 is minimized. Consequently, the interaction with the sample to be measured, for example the CO2 gas, becomes as small as possible. The interactions with the other properties of the transmission path T1, so the measuring space, mirror, the lenses or other devices in the beam path are as identical as possible to those of the actual measuring section. In addition, a compensation effect must be at the receiving diode 204 be possible, which is usually given.

The further processing of the receiver output signal S1 takes place in the processing unit 120 in the known manner. The processing unit 120 For this purpose, preferably again includes an optional amplifier 107 , a multiplier 208 , a filter 209 and another amplifier 211 , at whose output the signal S4 is applied. This signal is preferably also at the output of the processing unit 300 , In the multiplier 212 For example, the output signal S4 is typically multiplied by the supply signal S5, thus providing an advance signal 56 is formed that adds in a summer with a bias value, which is preferably generated by a bias generator B1. From this, the compensator supply signal S3 is formed, which is the compensation transmitter 205 is supplied.

Of course, this method can also be combined with other concepts. For example, the possibility of a narrow-band feed signal is given in such a way, in addition, the modulation signal is narrowband, so the modulation frequency is in a narrow band range and spread-Spectra method-based control possible or an optical "time-off-flight measurement". Such an optical time-of-flight measurement can be achieved, for example, by delaying the compensation signal as a function of a presignal. In particular, the feed signals need not be monofrequent. What is important is that any two different feed signals are orthogonal with respect to the scalar product. This means that the filtering of the product of two of these feed signals by the filter F must be zero.

In addition to the pulse oximetry, the heart rate measurement, CO2 content measurement in the breath or other gas analysis, the system can be used in many areas. For example, it is possible to monitor the growth of plants in a greenhouse. It is also possible to measure the concentration of fluorescent drugs in skin and tissue layers.

Tumor tissue can be distinguished from harmless blemishes. Out US5306144 is known to be an identification of carious sites on teeth by means of a spectral analysis is possible. Here, the use of the wavelengths 550 nm, 636 nm, 673 nm and possibly 770 nm or nearby wavelengths would make sense. The other applications are so varied that they can not be listed here. Reference should be made here to the literature of the life sciences (in particular biology, medicine and medical technology) in connection with the spectral properties of living substances and systems.

While the 9 shows a gas sensor or pulse sensor by transmission, which is designed as a single-channel diode spectrometer (a device according to the invention requires two channels) and in which the transmitter both a transmitting diode 203 as well as a compensation diode 205 includes 10 a dual-channel biometric sensor. In this diode spectrometer the transmitter comprises 200 a first transmitting diode 201 and a second transmitting diode 202 , The two transmitting diodes 201 . 202 are preferably formed as laser diodes, which operate with two different wavelength subregions, wherein the two wavelength subregions are predominantly narrowband. In a particular embodiment, they comprise exactly the wavelengths λ ₁ and λ ₂ . These two wavelengths correspond to the absorption wavelengths of the components to be measured in a medium (eg gas) or, for example, in the hemoglobin of a screened finger (T1). It is possible to determine two components at the same time.

That from the transmitter 200 emitted transmission signal S200, which consists of the transmission signals S201 and S202 of the transmission elements 201 . 202 composed, passes through a measuring path or transmission path T1, for example, through a measuring space 210 can be formed. In the measuring room 210 is the object to be examined. The transmission signal S200 is then received by a receiver, which is a receiving diode 204 is, which is sensitive to the two wavelengths λ ₁ and λ ₂ . The receiving diode 204 either can be designed to be quite narrow-band sensitive to precisely the wavelengths of interest λ ₁ , λ ₂ . However, it can also be sensitive in a broadband range of wavelengths, so that in any case the two wavelengths λ ₁ , λ ₂ are included.

The compensation diode 205 can either be an independent compensation transmitter 106 or part of the sender 200 , z. B. a transmitting element, be. The embodiment in which the compensation diode 205 a transmitting element of the transmitter 200 is, is in 10 shown in dashed lines. This is a preferred variant as only one transmitter 200 must be present. The transmitter 200 can of course also be designed as a single multi-wavelength diode or LED, the functions of the transmitting elements 201 . 202 or the transmitting diode 203 and compensation diode 205 includes. The radiated carrier wavelength of the compensation diode 205 In any case, it is chosen such that it lies next to the two absorption wavelengths λ ₁ and λ ₂ . Consequently, there is no overlapping region between the compensation carrier wavelength λ _k and the two transmitter wavelengths λ ₁ , λ ₂ .

The processing path behind the receiving diode 204 corresponds to the known signal processing lines, which are carried out in duplicate. In the demodulators 208a . 208b In each case, the amplified receiver output signal S1 multiplied by the respective supply signals S5a and S5b. The subsequent processing is analogous to the single-channel pulse sensor ( 9 ). At the output of the amplifier 211 and 211b are the signals S4a and S4b, which can be output (output 300a . 300b ) in order to be further processed and evaluated in another processing unit.

The output signals S4a and S4b are each in a further multiplier 212a respectively. 212b multiplied by the feed signals S5a and S5b, respectively, whereby the pre-signals S6a and S6b are formed. These signals are summed and added as a sum bias signal S6 with a bias value b1 from a bias generator B1 before the addition signal as Kompensatorspeisesignal S3 the compensation transmitter, a Kopensationsdiode 205 , is supplied.

The feed signals S5a and S5b are, as already mentioned above, preferably chosen orthogonal. This means that the signal components attributable to the supply signal S5a are projected onto the signal components of the supply signal S5b and result in zero

To feed the two transmission elements 201 and 202 the transmitter 200 For example, one or more signal generators G1 and / or G2 may be used. In the embodiment shown, the two transmitting elements 201 . 202 the transmitter 200 each fed with its own generator. Of course it is also possible to use only one generator. Anyway, in the transmitter 200 between the two wavelength subregions on the transmitting elements 201 and 202 switched. Only the orthogonality of the two feed signals S5a and S5b must be achieved. Also, the feed signals should be band limited to allow for filtering.

11 shows an alternative embodiment with a color and amplitude modulated transmitter, a color and amplitude modulated Compensation transmitter and two spectrally different sensitive receivers. This system is the more general case of the system used in 1 is shown as a special case for a channel.

The transmitter consists of two transmission elements H1 and H2. The transmitting element H1 is assigned the wavelength λ ₁ , which may correspond to the color red, for example. The transmission element H2 is associated with the wavelength λ ₂ , which may correspond, for example, to the color blue. Of course, analog systems with more than two transmitting elements and / or wavelengths are conceivable. However, the example shown here is completely sufficient for understanding.

Each of the transmission elements H1 and H2 has its own supply signal S51 and S52, ie it is supplied with its own supply signal S51 or S52. These feed signals are fed by two signal generators G1 and G2, which generate the feed signals S5φ and S5a. Typically, the feed signals are selected orthogonal to each other as described above. With the feed signal S5a, the common amplitude of the signals S51 and S52 is to be modulated, with the feed signal S5φ the intensity ratio of the two signals S51 and S51 to each other. This results in the following relationships: S51 = S5a + S5φ S52 = S5a - S5φ S51 + S52 = S5a

If S5a and S5φ are mutually orthogonal, so are S51 and S52. For this reason, a coordinate transformation between the two signals S5φ and S5a in the coordinate system referred to below as "φ-a coordinate system" is required in the signals S51 and S52 in the coordinate system, hereinafter referred to as the "1-2 coordinate system" ,

Here, this is done by a matrix multiplication with the matrix M1.

So it's a twist.

Before transmission, it is usually necessary to optimize the operating point of transmitters H1 and H2 by adding bias values B21 and B22.

The transmitters H1 and H2 now transmit in a first transmission path I1. As is known, the light of these transmitters is modified by the properties of the transmission path T1. This modification can in turn be effected by the transmission medium itself or objects in the transmission path or the internal structure of the transmission path.

The transmission signal of the transmitters H1 and H2 is received by spectrally different sensitive receivers D1 and D2 after passing through the second transmission link I2. This is a significant difference from the prior art. In this case, for example, D1 should be more sensitive to the wavelength λ ₁ than to be more sensitive to the wavelength λ ₂ and D ₂ for the wavelength λ ₂ than to the wavelength λ ₁ . By suitable processing (for example amplification and prefiltering) one obtains the two amplified receiver output signals S11 and S12. In the present exemplary case, preference is now given to a coordinate inverse transformation of the amplified receiver output signals S11 and S12 from the "1-2 coordinate system" into the "φ-a coordinate system" with the corresponding amplified receiver output signals S1a and S1φ. This is done in the present example by a renewed matrix multiplication with the matrix M2.

So this matrix is the transpose to M1 (M2 = M1 ^T ). The multiplication of all amplitudes with the factor 2 occurring in this case is not relevant in practice, because later on an amplification by a factor v takes place anyway.

Hereinafter, by forming a scalar product as described above, the proportion of the feed signal S5a in the retransformed amplified receiver output signal S1a is again determined. For this purpose, for example, this signal S1a is first multiplied by the feed signal S5a to the detection signal S10a and then filtered to the projection image signal S9a = F _a [S10a], wherein the filter F, for example, again a linear low-pass filter, that only those close to the modulation frequency f = 0 Hz Lets through signal components. The thus obtained projection image signal S9a = F _a [S10a] is amplified to the amplitude output signal S4a. This amplitude output signal S4a is one of the measured values of the system and reflects the wavelength independent attenuation of the total amplitude in the transmission channel T1. It is formed from the sum of the transmission parameters (attenuation) t ₁₁ and t ₁₂ (matrix M1) and is preferably at the output 300a at.

By forming a scalar product, the proportion of the signal S5φ in the retransformed receiver output signal S1φ is likewise determined. For this purpose, analogously to the above-described treatment of the signal S1a, this signal S1φ is first multiplied by the associated supply signal S5φ to the signal S10φ and then filtered to the signal Fφ [S10φ], the filter again being a linear low-pass filter, for example, only that close to the modulation frequency f = 0 Hz passes signal components. The thus obtained filter output signal Fφ [S10φ] is amplified to the signal S4φ. However, in contrast to the amplitude output signal S4a, here the filter output before amplification is the second measurement of the system and reflects the relative wavelength dependent attenuation in the transmission channel. Again, this is a significant difference from the prior art, where the disclosed devices and methods are typically only capable of measuring two amplitudes. The signal is formed from the difference of the transmission parameters (attenuation) t ₁₁ and t ₁₂ (of the matrix M2) (= t11 - t12). It is preferably located at an exit 300c at.

The use of other scalar products is particularly useful if the application system enforces the use of other filters F due to special requirements. It will not be difficult for a person skilled in the art to open up other applications by changing the definition of the scalar product of two signals. At this point, reference is made to the very extensive signal and control technical literature.

If the supply signals S5a and S5φ were sinusoidal and / or cosine signals, the signals S4a and S4φ would correspond to the associated closed-loop Fourier coefficients. The methodology described here thus provides a transformation into the dual space of the S5x signals, where x stands for a and φ in this example. For a better understanding, we speak here of this transformation of a "Fourier transformation" and put it in quotation marks to show that it is not the same but only an analogue.

Now follows the "Fourier inverse transformation" and the coordinate inverse transformation into the "1-2-coordinate system".

multipliziert werden. Es gilt dabei die folgende Zuordnung: S61 = S6a + S6φ S62 = S6a – S6φ S61 + S62 = S6a For the "Fourier inverse transformation", the thus determined amplitude and phase signals S4a and S4φ are multiplied by their corresponding supply signals S5a and S5φ to the presignal S6a and S6φ. For inverse transformation into the "1-2 coordinate system", the two signals are provided with the same transformation as the feed signals S5a and S5φ. This means in the concrete example that they are compatible with the matrix M1

be multiplied. The following assignment applies: S61 = S6a + S6φ S62 = S6a - S6φ S61 + S62 = S6a

The back-transformed forward signals S61 and S62 thus obtained are provided with bias values B11, B12 for setting the operating point of the compensation transmission elements K1 and K2. The associated compensator feed signals are designated S31 and S32.

In the present example, the compensation transmission element K1 is intended to transmit predominantly the wavelength λ ₁ corresponding to the transmission element H1 and the compensation transmission element K2 to emit predominantly the wavelength λ ₂ corresponding to the transmission element H2.

The signal of the compensation transmission elements K1 and K2 is typically linearly superimposed in the receiver elements D1 and D2 in each case summing. The compensation transmission elements K1 and K2 in this case transmit into a second transmission path which either does not influence their signal or in a predetermined manner before it strikes the reception elements D1 and D2.

It can be shown that for the example described above, with a suitable choice of the gains, the filters and the signal properties of the signals S5a and S5φ, the attenuation t ₁₁ in the first transmission channel at the wavelength λ ₁ and the attenuation t ₁₂ in the first transmission channel at the wavelength λ ₂ in the following relationship with the output values S9φ = Fφ [S10φ] and S4a of the system are:

It is thus possible to separate the amplitude change t ₁₁ from the color change. This is a significant difference from the prior art. Only this transformation enables integration into mobile devices such. As mobile phones, since distance fluctuations are compensated by the manual handling of the mobile device. The signal S4a represents the change in amplitude as it passes through the medium T1; the signal S9φ = Fφ [S10φ] is the change in the composition of the signal (in particular of the light) by λ ₁ and λ ₂ again. For example, the system is suitable as a skin color sensor in a disturbed environment. The individual losses can also be determined, for. B. by coordinate transformation.

12 shows another form of the system according to the invention.

A first generator Ga generates a feed signal S5a, with which the amplitude of the n feed signals S5v1 to S5vn is multiplied by amplitude modulation by multiplication with the signals S51 to S5n. These are typically provided with an offset b1 to bn. Likewise, these offsets are typically identical. The offsets b1 to bn serve to enable the control of LEDs as transmitters H1 to Hn. The transmitters H1 to Hn now each transmit a signal S51 to S5n with said offset into the transmission path. Typically, the spectral focuses of the radiated electromagnetic radiation of the transmitters H1 to Hn are different. In the transmission path is, for example, the object to be measured O. This is irradiated in this example. The radiation thus modified when the object is irradiated is picked up by a detector D1 and converted into the receiver output signal S0. Typically, the detector is sensitive to all electromagnetic waves radiated from the various transmitters H1 to Hn.

This receiver output signal S0 is amplified to the amplified receiver output signal S1. The gain can be 1 or complex and / or be provided with a frequency response.

The thus prepared receiver output signal is now distributed to n + 1 controller.

Each k-th channel controller k is again composed of a multiplier unit in which the amplified receiver output signal S1 is multiplied by a base signal S5k to the signal S10k, followed by a low pass F which reliably suppresses the base signal frequencies and overlying frequencies, followed by boosting of the thus generated DC signal S9k by a factor v, where v is chosen so that the resulting later control loop is stable. The thus generated amplifier output signal S4k is converted in a further multiplication with the associated base signal S5k to the specific Kompensatorvorsignal S6vk.

At the same time the amplitude is measured. For this purpose, an analog controller structure is used. Instead of the respective base signal S5k, however, the amplitude modulation signal S5a is now used.

The n S6k compensator biases are summed together and this sum multiplied by the output S6a of the amplitude measurement regulator. The result is the compensator bias signal S6.

This is converted to the compensator supply signal S3 by adding an offset B11, which may also be zero. This feeds the compensator, which also radiates into the receiver D1, typically linearly superimposed.

The n individual output signals S4k (where 0 <k <n + 1) represent the measured values of the individual assigned transmitter / diode pairs.

The signal S4a represents a measured value for the amplitude.

The k generator signals S5v1 to S5vn are intended to be orthogonal with respect to the Skalar products represented by the multipliers and filters.

The particular advantage of this system is that a spectrum can be obtained from the S41 to S4n signals by a main axis transformation that does not depend on the distance between the measuring system and the object as long as the object is within the measuring range of the system.

14 shows the exemplary spectrum of a healthy tooth (A) and a carious tooth (B)

A detection of a carious tooth can thus, for example, by means of a system accordingly 12 respectively. The spectrum of the tooth is segmented into different spectral segments corresponding to the number n of transmitters H1 to Hn.

In the Gengensatz to US5306144 , in which no compensation by a compensation transmitter K1 (see 12 ) takes place, the device according to the invention by the compensation K1 is much more robust against extraneous light and able to determine the relative spectrum regardless of the amplitude and thus the distance measuring instrument <-> tooth.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3135802 A1 [0013, 0014, 0020, 0022, 0026]
• DE 3405444 A1 [0015]
• DE 69113785 T2 [0017]
• DE 69122637 T2 [0019, 0019]
• DE 102008022920 A1 [0021]
• US 258719 [0023]
• US 4260951 [0025]
• US 4258719 [0027]
• US 5774213 [0028, 0028, 0028, 0028, 0029, 0030, 0030, 0030, 0037, 0085, 0089]
• US 5306144 [0120, 0163]

Claims (13)

Sensor system for the optical measurement of biometric parameters of an animal or a plant or a human comprising at least a first transmitter (H1) and at least one second transmitter (H2) and at least one receiver (D1), - wherein the device has at least one further transmitter (K1) and - wherein at least one first transmitter (H1) is operated with a supply signal (S5a) of a signal generator (G1) and - wherein at least one second transmitter (H2) is operated with a supply signal (S5b) and - whereby the output from the first transmitter ( H1) and the electromagnetic radiation emitted by the second transmitter (H2) fall onto the measurement object T1 and are reflected by it onto at least one receiver (D1) and / or penetrate the measurement object (T1) and fall on at least one receiver (D1), and wherein at least one control circuit (CT) at least one Kompensatorspeisesignal (S3) from at least one receiver output signal (S0) of one of said Empfä (D1) generated and - wherein said control circuit (CT) by a respective linear form the receiver output signal (S0) at least one feed signal (S5a) and at least one other feed signal (S5b) linked and - the Kompensatorspeisesignal (S3), apart from an optimal offset, linearly proportional to the sum of the respective amplified results of these linear forms, the magnitude of the gain 1 and - wherein at least one Kompensatorspeisesignal (S3) a compensation transmitter (K1) is fed and - said controller (CT) the Kompensatorspeisesignal (S3) corrects so that the said receiver output signal (S0) except for control error and system noise no Share of the transmission signals (S5a) and (S5b) more and - wherein the controller (CT) at least one internal control signal (S4) outputs as an intermediate signal and - the course of this intermediate signal (S4) is evaluated so that at least one biometric parameter that Signal is extracted. Sensor system for the optical measurement of biometric parameters of an animal, a plant or a human, comprising at least one first transmitter (H1) and at least two receivers (D1) and (D2), - Wherein the device per receiver (D1, D2) has at least one each further transmitter (K1, K2) and - Wherein at least a first transmitter (H1) with a feed signal (S5) of a signal generator (G1) is operated and Wherein at least the electromagnetic radiation emitted by a first transmitter (H1) is incident on the measuring object T1 and is reflected by it onto at least two receivers (D1, D2) and / or passes through the measuring object (T1) and is transmitted to at least two receivers (D1, D1). D2) falls and - wherein at least one control circuit (CT) generates at least two compensator supply signals (S31, S32) from at least two receiver output signals (S01, S02) of said receivers (D1, D2) and - Wherein said control circuit (CT) by a respective linear form the receiver output signals (S01, S02) at least with a feed signal (S5) linked and - wherein the Kompensatorspeisesignale (S31, S32), apart from an optimal offset, are linearly proportional to the results of these linear forms and - Wherein at least one Kompensatorspeisesignal (S31, S32) each one of the compensation transmitter (K1, K2) is fed and - said controller (CT) compensating the compensator feed signals (S31, S32) such that said receiver output signals (S01, S02) each have no part of the supply signal (S5), except for control errors and system noise - Wherein the controller (CT) at least two internal control signals, in particular (S4a, S9φ), outputs as intermediate signals and - Wherein the course of at least one of these intermediate signals, in particular (S4a, S9φ), is evaluated so that at least one biometric parameter is extracted at least from this signal. Device according to one of the preceding claims, - wherein the biometric parameter is the heart rate or the blood oxygen content or the chlorophyll content of plants or the concentration of a drug in a tissue or the CO ₂ content in the exhaled air. Device according to one or more of the preceding claims, - at least one transmitter having an LED (H1, H2, ... Hn, 9 . 12 . 15 . 17 ) or at least one receiver is a photodiode, a photoresistor or a phototransistor. Device according to one or more of the preceding claims, - wherein at least one controller (CT) as linear form a scalar product between at least one feed signal (S5a, S5b, S5, S5φ) and at least one receiver output signal (S0, S01, S02), in particular by Multiplication and subsequent low-pass filtering, to a projection image signal (S9, S9a, S9b, S9φ) and transforms a thus formed projection image signal (S9, S9a, S9b, S9φ) with at least one Speisesssignal (S5a, S5b, S5, S5φ), in particular multiplied by an optional amplification to a presignal (S6, S61, S62) - and thus adding a preliminary signal formed (S6, S61, S62) with an optional bias value and so on a Kompensatorspeisesignal (S3, S31, S32) forms - a Kompensatorspeisesignal (S3, S31, S32) thus formed a compensation transmitter (K1, K2, 8th . 205 ) feeds. Sensor system for the optical measurement of biometric parameters of an animal, a plant or a human with at least one transmitter ( 200 , H1) and a receiver ( 204 , D1) for measuring the transmission characteristics of a first transmission path between a transmitter ( 200 , H1) and the receiver ( 204 , D1), where - the transmitter ( 200 , H1) is designed and set up to send a transmission signal (S25) into the first transmission path which, after passing through at least part of the first transmission path, is transmitted from the receiver (S25). 204 , D1) is detected, - the receiver ( 204 , D1) is designed and configured to receive the transmission signal (S25) and to form therefrom a receiver output signal (S0) and, - a processing unit ( 120 , CT) adapted and arranged to further process the receiver output signal (S0) and obtain information of the characteristics of the first transmission link, such as detecting the presence or characteristics of an object; characterized in that - the transmitter ( 200 , H) can emit at least a part of the spectrum of electromagnetic radiation in at least two predetermined wavelength subregions, in particular with at least two colors, wherein the emission intensity of the at least two wavelength ranges can be regulated in particular in opposite directions with the aid of at least one signal, so that the Radiation of one of the at least two wavelength sub-ranges can be emitted in a predetermined by the regulation ratio and - the receiver ( 204 , D1) is sensitive enough to receive the intensity of electromagnetic radiation at least in the two wavelength ranges of interest, and - the processing unit ( 120 , CT) further processes the receiver output signals (S0) based on the at least two wavelength ranges and obtains therefrom information about the transmission characteristics. Sensor system according to one or more of the preceding claims, characterized in that - at least one transmitter ( 202 . 200 , H1) can emit at least a part of the spectrum of electromagnetic radiation in at least two predetermined wavelength subregions, in particular with at least two colors, wherein preferably the emission intensity of the at least two wavelength ranges can be regulated with the aid of at least one further signal, in particular in the same direction, so that the radiation of the at least two wavelength subregions can be emitted with an overall intensity predetermined by the regulation. Sensor system according to one of the preceding claims, characterized in that at least one transmitter ( 202 . 200 , H1) emits electromagnetic radiation in exactly two or preferably in more than two wavelength subregions. Sensor system according to claim 8, characterized in that at least one transmitter ( 202 . 200 , H1) emits electromagnetic radiation with wavelength range-specific controllable intensity. Sensor system according to one of the preceding claims, characterized in that the transmitter ( 200 ) at least two transmitting elements ( 201 . 202 , H1, H2) which each emit a signal (S201, S202) each having a specific wavelength, in particular a color signal, and which are alternately active, the transmitting elements ( 201 . 202 , H1, H2) are preferably light-emitting diodes (LED). Sensor system according to the preceding claim, characterized in that the transmitting elements ( 201 . 202 , H1, H2) of the transmitter ( 200 ) emits a constant luminous flux for each wavelength range, in particular each color signal, such that the amount of energy emitted is substantially equal to the sum of the radiation of all the transmission elements or that the sum of the receiver signal amplitudes is substantially the same. Sensor system according to one of the preceding claims, characterized in that the receiver ( 204 ) comprises at least two, preferably at least four receiving elements, each having a different spectral sensitivity profile, wherein the receiving elements are preferably spectrally different sensitive. Sensor system according to one of the preceding claims, characterized in that - a compensation transmitter ( 205 , K1, K2) sends a compensation signal (S23) into a second transmission path which is transmitted by the receiver ( 204 , D1, D2) is detected after passing through the second transmission path, - the recipient ( 204 , D1, D2) receives the transmission signal (S25) and the compensation signal (S23) superimposed, in particular linearly and / or summing, and from this at least one receiver output signal (S0) and / or an amplified receiver output signal (S1) is formed, - the processing unit ( CT, 120 ) the receiver output signal (S0) or the amplified receiver output signal (S1) is further processed into a compensator supply signal (S3), and the compensating transmitter (S) ( 205 , K1, K2) for feedback control of the receiver output signal (S0) or the amplified receiver output signal S1, so as to obtain information about the transmission characteristics of the transmission path and at least one biometric parameter.

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