CA1297711C - Clear holographic helmet visor - Google Patents
Clear holographic helmet visorInfo
- Publication number
- CA1297711C CA1297711C CA000564759A CA564759A CA1297711C CA 1297711 C CA1297711 C CA 1297711C CA 000564759 A CA000564759 A CA 000564759A CA 564759 A CA564759 A CA 564759A CA 1297711 C CA1297711 C CA 1297711C
- Authority
- CA
- Canada
- Prior art keywords
- plate
- holographic
- hologram
- spherical
- approximately
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
- G02B27/0103—Head-up displays characterised by optical features comprising holographic elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/017—Head mounted
- G02B27/0172—Head mounted characterised by optical features
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
- G02B27/0103—Head-up displays characterised by optical features comprising holographic elements
- G02B2027/0105—Holograms with particular structures
- G02B2027/0107—Holograms with particular structures with optical power
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
- G02B27/0103—Head-up displays characterised by optical features comprising holographic elements
- G02B2027/0109—Head-up displays characterised by optical features comprising holographic elements comprising details concerning the making of holograms
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
- G02B2027/0145—Head-up displays characterised by optical features creating an intermediate image
Abstract
ABSTRACT OF THE DISCLOSURE
The visor can be readily mounted on a helmet by virtue of the fact that it dispenses with the need for any optical relay system. Provision is made for a light image generator, an optical combining and collim-ating assembly in which a holographic flat plate and a holographic spherical plate are grouped together so as to provide a view of the collimated image superimposed on the landscape. The holographic spherical plate is employed off the axis and produces collimation in a pupil zone placed substantially at the focal distance of the apex of the spherical mirror. The hologram of the spherical plate is recorded by means of a digital hologram in order to minimize aberrations. The flat plate can be fairly steeply inclined with respect to the sighting axis and so designed as to reduce the ratio of parasitic reflection of the imaging channel.
The visor can be readily mounted on a helmet by virtue of the fact that it dispenses with the need for any optical relay system. Provision is made for a light image generator, an optical combining and collim-ating assembly in which a holographic flat plate and a holographic spherical plate are grouped together so as to provide a view of the collimated image superimposed on the landscape. The holographic spherical plate is employed off the axis and produces collimation in a pupil zone placed substantially at the focal distance of the apex of the spherical mirror. The hologram of the spherical plate is recorded by means of a digital hologram in order to minimize aberrations. The flat plate can be fairly steeply inclined with respect to the sighting axis and so designed as to reduce the ratio of parasitic reflection of the imaging channel.
Description
~2~771~
A CLEAR HOLOGRAPHIC HELMET VISOR
BACKGROUND OF THE INVENTION
The present invention relates to a clear holographic visor which serves to constitute a helmet-mounted head-up navigational collimator. By means of this collimator, an aircraft pilot can view an image which is reflected at infinity and superimposed on his vision of the surrounding landscape. Depending on requirements, this light image can consist of navigation data, a sighting reticle or a synthetic image produced by a generator or an associated sensor such as an infrared sensor, for example.
As a general rule, the light image to be collimated is first formed on the screen of a cathode-ray tube or of a liquid crystal matrix, then directed to a first conventional optical system or so-called optical relay which converts it to an intermediate image. The intermediate image is collimated by means of a partially reflecting optical system which can be composed of a flat plate and a spherical plateutilized on the axis. The two plates are treated in order to produce partial reflection of the rays received from the screen while partially transmitting those which originate from the landscape. This results in loss of information on both channels, namely on the imager ; ~
~, 12~7711 channel and on the external landscape viewing channel.
- Moreover, the treatments employed are such that parasitic images such as! for example, reflections from the rear face of the flat plate, still remain and are liable to hinder the observer. A further drawback is that these collimators have a limited optical field and are too cumbersome to be mounted on a helmet.
In accordance with techniques which offer higher performances, the off-axis arrangement is adopted and the plates are subjected to holographic treatments for obtaining collimation with enhanced photometric efficiency by diffraction as well as improved trans-mission o~ the landscape channel. Solutions of this type are described in the article by J.R. Banbury published in the April 1983 issue of "Displays" and entitled "Wide field-of-view head-up displays".
Particularly worthy of note in this article is the solution illustrated in FIG. 8C on page 95. This figure shows a head-up structure equipped with a reversing mirror and an optical relay system, the dimensions of which can be made compatible with the equipment by virtue of the fact that the observer's eye is placed at a sufficient distance from the combining and collimating assembly constituted by the flat plate and the spherical plate. In a system of this type, the observation pupil is accordingly placed ,, 771~
in proximity to the center of the spherical mirror.
The optical relay system serves to form the intermediate image as well as to correct aberrations of the holo-graphic plates. By reason of the position o~ the pupil (at the center of the spherical mirror~, this system cannot be perfectly optimized for anti-reflection treat-ments on the flat plate, with the result that it pro-duces substantial parasitic images. Moreover, the use of an optical relay system is always penalized by the weight and bulk of the visor.
The object of the invention is to overcome these disadvantages by constructing a clear holographic visor of the type aforesaid having a wide field without any optical relay system, which can be mounted on a helmet, and which offers a very good photometric balance with a minimized proportion of parasitic images. Its limited overall size also makes it easier to mount on a helmet or within a cockpit.
SUMMARY OF THE INVENTION
In accordance with the invention, this object is achieved with a clear holographic visor comprising a generator for producing a light image to be collimated, an optical collimating and combining assembly in which are grouped together a flat holographic plate and a spherical holographic plate for providing a view of the collimated image superimposed on the landscape, the lZ977~ 1 radiation of the light image being reflected from the flat plate to the spherical plate which is employed off the axis and the hologram of which produces collimation of the image at infinity. In accordance with the distinctive feature of the invention, the hologram of the spherical plate is determined by means of a computer and recorded by making use of a digital hologram in order to minimize aberrations and to produce for the field of utilization which is contemplated an observ-ation pupil at a distance substantially equal to thefocal distance with respect to the apex of the spherical mirror.
BRIEF DESCRIPTION OF T~E DRAWINGS
FIG. l is a simplified diagram of a clear visor in accordance with the invention.
FIG. 2 is a diagram of construction of the optical collimating and combining assembly.
FIG. 2A is a detail diagram of the holographic flat plate of FIG. 2.
20FIG. 3 is a diagram illustrating the optical collimation path.
FIG. 4 is a diagram of an application in which the visor is mounted on a helmet.
DEI'AILED DESCRIPTION OF THE INVENTION
25Reference being made to FIG. 1, the visor is constituted by a light image generator represented in a .. ..
12~771~
simplified manner by its screen 1. In the majority of instances, said generator is formed by means of a cathode-ray tube or a liquid crystal matrix and the screen on which is formed the light image to be collim-ated is usually flat as shown.
The screen 1 is located at the focus of a holographic mirror 3 formed on a spherical support and employed off the axis. The light image is reflected to said mirror by means of a flat holographic plate 2 which forms a deviating mirror. As shown in the figure, this collimating assembly is so determined that, starting from each point M of the light image in the case of the field beam shown, there is formed an emergent beam of parallel rays which pass through an observation pupil P1.
This pupil is located at a distance SP from the apex of the spherical mirror 3 which is substantially equal to its focal distance, that is, to R/2, where R is the radius of curvature of said mirror. The point C re-presents the center of curvature, the axis Z1 is the central axis of said mirror, the axis Z0 represents the direction of reflection corresponding to the normal direction of vision of the observer and the angle ~
between these two axes represents the angular deviation from the utilization axis. The pupil P1 has a diameter 01.
The optical collimation path is shown in ~2977~L
greater detail in FIG. 3 in the case of three points M1, M2, M3 of the light image, Ml being the central point on the axis and M2, M3 being end points. It is apparent that the collimated beams converge in the pupil zone P1.
The optical path first involves a reflection from the first hologram H1 carried by the flat plate 2. The radiation is reflected by diffraction toward the spherical mirror 3 at which a second hologram H2 pro-duces collimation, whereupon the collimated rays have an incidence such that they pass through the hologram H1 without being diffracted. The radiation received from the exterior passes successively through the holo-grams H2 and Hl carried by the plates 3 and 2. The pupil P1, or eye-box, represents the zone in which the eye is capable of displacement. By way of example, the diameter of the pupil can be of the order of 15 milli-meters.
Off-axis utilization of the hologram H2 on a spherical support 3 introduces a variation of incidence of the rays on the plate 2 before and after reflection from the hologram H2. This makes it possible to employ the flat plate 2 with the hologram 1 in such a manner as to produce selective reflection of the light rays as a function of their incidence. The flat plate 2 produces practically total reflection of the radiation received from the screen 1 and permits practically total trans-, . . .
~771~
mission of said radiation after reflection from thehologram H2. The off-axis position permits angular separation of the rays to be reflected from those to be transmitted. The flat holographic plate 2 permits a high photometric gain for transmission on the imager channel. This gain is further enhanced by the use of the hologram H2 on the spherical support 3 which also permits achievement of reflection efficiencies of 100 %
on the imager channel. Generally speaking, the use of the two holograms H1 and H2 makes it possible to obtain a transmission in the vicinity of 100 % on the landscape channel throughout the spectrum with the exception of the wavelength (or narrow band) of effective reflection corresponding to the emission band of the imager 1, and also of the order of 100 ~ on the imager channel in the case of the selected wavelength (or narrow wavelength spectrum) corresponding to the radiation emitted by said image generator.
FIG. 2 illustrates in greater detail a mode of construction of the optical combining and collimating assembly, that is to say of the elements 2 and 3. Each element is made up of a hologram Hl and H2 respectively which are sandwiched between two transparent plates of glass, for example. The hologram H1 is placed between the flat plates 21 and 22 whilst the hologram H2 is placed between the spherical plates 31 and 32 having the 12~7~1~
same curvature.
FIG. 2A relates to an enlarged detail of the plate 2 and points up a particular feature of the assembly which permits an increase in photometric gain by reduction of the parasitic image ratio. The plate 22 serves to support the hologram H1 and the plate 21 con-stitutes a sealing plate. The thickness chosen for the sealinq plate is very small and may thus be one-tenth of a millimeter, for example. In consequence, the useful radiation RU diffracted by reflection from the hologram H1 is very close to the parasitic radiation RP reflected from the front face of the sealing plate 21. In the case of a conventional plate which is treated so as to be partially transparent, the useful radiation RU is reflected from the front face and the parasitic-radia-tion RP is produced by reflection from the untreated rear face of the flat plate. This radiation RP is fairly distant from the main reflection RU, the more so as the flat plate is of substantial thickness. Further-more, if K designates the reflection factor of thetreated face, it can be demonstrated that the ratio T of parasitic images is substantially equal to 1.6 K in the case of a treated flat plate and equal to K in the case of the holographic plate 2. There is therefore gained a factor of 1.6 in parasitic light, which is very significant in the case of visors of this type.
lZ~77~
g Moreover, since the eye is located substantial-ly in the focal plane of the hologram H2, the incidences of the rays to be reflected from the flat plate are little different from each other. ~n fact, the rays issuing from the imager 1 must arrive collimated on the eye pupil Pl. Since this pupil is of small size (01) with respect to the overall dimensions of the assembly and is located at the image focal point of the hologram H2, this means that the rays must arrive in practically parallel relation on the hologram H2 and therefore also on the hologram Hl of the plate 2. This makes it possible to provide an anti-reflection treatment of very good quality both on this plate and on the sealing plate 21 of the plate 2. With this anti-reflection treatment resulting from the particular location of the pupil Pl, the parasitic image ratio may accordingly be reduced even further.
The use of the curved holographic plate 3 makes it possible to correct aberrations of the system in holographic reflection. In order to obtain this result, there is employed a hologram H2 recorded with two complex waves, at least one of which is produced by means of a digital hologram. This latter is computed beforehand by means of a computer and then integrated on the recording bench.
The principle of digital holography consists ~771~
in making use of a mathematical expression with co-efficients or parameters which are variable in order to represent the optical formula. As a function of the choice of parameters, the aberrations exhibited by this optical formula are computed. The values of the para-meters are then modified, and consecutively the optical formula, so as to reduce the aberrations by wavefront deformations. With the aid of numerical calculations, there is thus progressively obtained an optimized optical formula with minimized or very slight aberra-tions. These calculations are made while taking into account the total useful field desired for the system and serve in the final analysis to define a holo-graphic optical system 3 which makes it possible to dispense with any image-reforming optical relay system.
The digital holography technique employed permits an increase both in field and in resolution while achieving a reduction in overall size.
Another point worthy of note is the advantage of off-axis utilization from an ergonomic standpoint.
In fact, the angle of slope of the flat plate 2 with respect to the axis Z0 can be increased and may exceed the value of 45~ which is usually adopted in conven-tional solutions with partially transparent treated plates. The structure proposed is therefore less aggressive and becomes easier to mount on a helmet.
~7'711 In the case of a potential application which consists in making use of a head-up visor for a heli-copter, the angle of slope of the flat plate can be maintained at 45, thus making it possible to displace S the screen l to the rear and to increase the field of the system without bringing the tube (CRT) into contact with the transparent wall of the cockpit.
By way of example of construction, the angles indicated can have the following values :
- off-axis angle a of the order of 15 ;
- angle of inclination of the plate 2 to the axis z0 corresponding to the normal direction of vision : of the order of 70 ;
- angle between the axis Z1 and the plate 2 : approx-imately 55 ;
- radius R : 160 mm ;
- field of utilization of the collimated vision :
circular field attaining a value of over 40.
The clear holographic visor hereinabove - 20 described accordingly offers many different advantages including high photometric efficiency, low parasitic image ratio, increased field and resolution, smaller bulk owing to suppression of an image-reforming optical system, improved ergonomy by increased inclination of ~he flat plate.
One example of application is given in FIG. 4 ~$771~
in regard to a helmet-mounted visor involving the use of a liquid-crystal matrix 1 illuminated by means of a light source (not shown in the drawings but either external or carried by the helmet~. ~ bundle of fibers 11 transmits the light radiation from the source to the rear of the matrix after reflection from a reflecting mirror 10.
This assembly can be transposed to a heli-copter cabin or cockpit with, if necessary, a steeper inclination of the flat plate 2 in order to facilitate installation of a large-size imager.
A CLEAR HOLOGRAPHIC HELMET VISOR
BACKGROUND OF THE INVENTION
The present invention relates to a clear holographic visor which serves to constitute a helmet-mounted head-up navigational collimator. By means of this collimator, an aircraft pilot can view an image which is reflected at infinity and superimposed on his vision of the surrounding landscape. Depending on requirements, this light image can consist of navigation data, a sighting reticle or a synthetic image produced by a generator or an associated sensor such as an infrared sensor, for example.
As a general rule, the light image to be collimated is first formed on the screen of a cathode-ray tube or of a liquid crystal matrix, then directed to a first conventional optical system or so-called optical relay which converts it to an intermediate image. The intermediate image is collimated by means of a partially reflecting optical system which can be composed of a flat plate and a spherical plateutilized on the axis. The two plates are treated in order to produce partial reflection of the rays received from the screen while partially transmitting those which originate from the landscape. This results in loss of information on both channels, namely on the imager ; ~
~, 12~7711 channel and on the external landscape viewing channel.
- Moreover, the treatments employed are such that parasitic images such as! for example, reflections from the rear face of the flat plate, still remain and are liable to hinder the observer. A further drawback is that these collimators have a limited optical field and are too cumbersome to be mounted on a helmet.
In accordance with techniques which offer higher performances, the off-axis arrangement is adopted and the plates are subjected to holographic treatments for obtaining collimation with enhanced photometric efficiency by diffraction as well as improved trans-mission o~ the landscape channel. Solutions of this type are described in the article by J.R. Banbury published in the April 1983 issue of "Displays" and entitled "Wide field-of-view head-up displays".
Particularly worthy of note in this article is the solution illustrated in FIG. 8C on page 95. This figure shows a head-up structure equipped with a reversing mirror and an optical relay system, the dimensions of which can be made compatible with the equipment by virtue of the fact that the observer's eye is placed at a sufficient distance from the combining and collimating assembly constituted by the flat plate and the spherical plate. In a system of this type, the observation pupil is accordingly placed ,, 771~
in proximity to the center of the spherical mirror.
The optical relay system serves to form the intermediate image as well as to correct aberrations of the holo-graphic plates. By reason of the position o~ the pupil (at the center of the spherical mirror~, this system cannot be perfectly optimized for anti-reflection treat-ments on the flat plate, with the result that it pro-duces substantial parasitic images. Moreover, the use of an optical relay system is always penalized by the weight and bulk of the visor.
The object of the invention is to overcome these disadvantages by constructing a clear holographic visor of the type aforesaid having a wide field without any optical relay system, which can be mounted on a helmet, and which offers a very good photometric balance with a minimized proportion of parasitic images. Its limited overall size also makes it easier to mount on a helmet or within a cockpit.
SUMMARY OF THE INVENTION
In accordance with the invention, this object is achieved with a clear holographic visor comprising a generator for producing a light image to be collimated, an optical collimating and combining assembly in which are grouped together a flat holographic plate and a spherical holographic plate for providing a view of the collimated image superimposed on the landscape, the lZ977~ 1 radiation of the light image being reflected from the flat plate to the spherical plate which is employed off the axis and the hologram of which produces collimation of the image at infinity. In accordance with the distinctive feature of the invention, the hologram of the spherical plate is determined by means of a computer and recorded by making use of a digital hologram in order to minimize aberrations and to produce for the field of utilization which is contemplated an observ-ation pupil at a distance substantially equal to thefocal distance with respect to the apex of the spherical mirror.
BRIEF DESCRIPTION OF T~E DRAWINGS
FIG. l is a simplified diagram of a clear visor in accordance with the invention.
FIG. 2 is a diagram of construction of the optical collimating and combining assembly.
FIG. 2A is a detail diagram of the holographic flat plate of FIG. 2.
20FIG. 3 is a diagram illustrating the optical collimation path.
FIG. 4 is a diagram of an application in which the visor is mounted on a helmet.
DEI'AILED DESCRIPTION OF THE INVENTION
25Reference being made to FIG. 1, the visor is constituted by a light image generator represented in a .. ..
12~771~
simplified manner by its screen 1. In the majority of instances, said generator is formed by means of a cathode-ray tube or a liquid crystal matrix and the screen on which is formed the light image to be collim-ated is usually flat as shown.
The screen 1 is located at the focus of a holographic mirror 3 formed on a spherical support and employed off the axis. The light image is reflected to said mirror by means of a flat holographic plate 2 which forms a deviating mirror. As shown in the figure, this collimating assembly is so determined that, starting from each point M of the light image in the case of the field beam shown, there is formed an emergent beam of parallel rays which pass through an observation pupil P1.
This pupil is located at a distance SP from the apex of the spherical mirror 3 which is substantially equal to its focal distance, that is, to R/2, where R is the radius of curvature of said mirror. The point C re-presents the center of curvature, the axis Z1 is the central axis of said mirror, the axis Z0 represents the direction of reflection corresponding to the normal direction of vision of the observer and the angle ~
between these two axes represents the angular deviation from the utilization axis. The pupil P1 has a diameter 01.
The optical collimation path is shown in ~2977~L
greater detail in FIG. 3 in the case of three points M1, M2, M3 of the light image, Ml being the central point on the axis and M2, M3 being end points. It is apparent that the collimated beams converge in the pupil zone P1.
The optical path first involves a reflection from the first hologram H1 carried by the flat plate 2. The radiation is reflected by diffraction toward the spherical mirror 3 at which a second hologram H2 pro-duces collimation, whereupon the collimated rays have an incidence such that they pass through the hologram H1 without being diffracted. The radiation received from the exterior passes successively through the holo-grams H2 and Hl carried by the plates 3 and 2. The pupil P1, or eye-box, represents the zone in which the eye is capable of displacement. By way of example, the diameter of the pupil can be of the order of 15 milli-meters.
Off-axis utilization of the hologram H2 on a spherical support 3 introduces a variation of incidence of the rays on the plate 2 before and after reflection from the hologram H2. This makes it possible to employ the flat plate 2 with the hologram 1 in such a manner as to produce selective reflection of the light rays as a function of their incidence. The flat plate 2 produces practically total reflection of the radiation received from the screen 1 and permits practically total trans-, . . .
~771~
mission of said radiation after reflection from thehologram H2. The off-axis position permits angular separation of the rays to be reflected from those to be transmitted. The flat holographic plate 2 permits a high photometric gain for transmission on the imager channel. This gain is further enhanced by the use of the hologram H2 on the spherical support 3 which also permits achievement of reflection efficiencies of 100 %
on the imager channel. Generally speaking, the use of the two holograms H1 and H2 makes it possible to obtain a transmission in the vicinity of 100 % on the landscape channel throughout the spectrum with the exception of the wavelength (or narrow band) of effective reflection corresponding to the emission band of the imager 1, and also of the order of 100 ~ on the imager channel in the case of the selected wavelength (or narrow wavelength spectrum) corresponding to the radiation emitted by said image generator.
FIG. 2 illustrates in greater detail a mode of construction of the optical combining and collimating assembly, that is to say of the elements 2 and 3. Each element is made up of a hologram Hl and H2 respectively which are sandwiched between two transparent plates of glass, for example. The hologram H1 is placed between the flat plates 21 and 22 whilst the hologram H2 is placed between the spherical plates 31 and 32 having the 12~7~1~
same curvature.
FIG. 2A relates to an enlarged detail of the plate 2 and points up a particular feature of the assembly which permits an increase in photometric gain by reduction of the parasitic image ratio. The plate 22 serves to support the hologram H1 and the plate 21 con-stitutes a sealing plate. The thickness chosen for the sealinq plate is very small and may thus be one-tenth of a millimeter, for example. In consequence, the useful radiation RU diffracted by reflection from the hologram H1 is very close to the parasitic radiation RP reflected from the front face of the sealing plate 21. In the case of a conventional plate which is treated so as to be partially transparent, the useful radiation RU is reflected from the front face and the parasitic-radia-tion RP is produced by reflection from the untreated rear face of the flat plate. This radiation RP is fairly distant from the main reflection RU, the more so as the flat plate is of substantial thickness. Further-more, if K designates the reflection factor of thetreated face, it can be demonstrated that the ratio T of parasitic images is substantially equal to 1.6 K in the case of a treated flat plate and equal to K in the case of the holographic plate 2. There is therefore gained a factor of 1.6 in parasitic light, which is very significant in the case of visors of this type.
lZ~77~
g Moreover, since the eye is located substantial-ly in the focal plane of the hologram H2, the incidences of the rays to be reflected from the flat plate are little different from each other. ~n fact, the rays issuing from the imager 1 must arrive collimated on the eye pupil Pl. Since this pupil is of small size (01) with respect to the overall dimensions of the assembly and is located at the image focal point of the hologram H2, this means that the rays must arrive in practically parallel relation on the hologram H2 and therefore also on the hologram Hl of the plate 2. This makes it possible to provide an anti-reflection treatment of very good quality both on this plate and on the sealing plate 21 of the plate 2. With this anti-reflection treatment resulting from the particular location of the pupil Pl, the parasitic image ratio may accordingly be reduced even further.
The use of the curved holographic plate 3 makes it possible to correct aberrations of the system in holographic reflection. In order to obtain this result, there is employed a hologram H2 recorded with two complex waves, at least one of which is produced by means of a digital hologram. This latter is computed beforehand by means of a computer and then integrated on the recording bench.
The principle of digital holography consists ~771~
in making use of a mathematical expression with co-efficients or parameters which are variable in order to represent the optical formula. As a function of the choice of parameters, the aberrations exhibited by this optical formula are computed. The values of the para-meters are then modified, and consecutively the optical formula, so as to reduce the aberrations by wavefront deformations. With the aid of numerical calculations, there is thus progressively obtained an optimized optical formula with minimized or very slight aberra-tions. These calculations are made while taking into account the total useful field desired for the system and serve in the final analysis to define a holo-graphic optical system 3 which makes it possible to dispense with any image-reforming optical relay system.
The digital holography technique employed permits an increase both in field and in resolution while achieving a reduction in overall size.
Another point worthy of note is the advantage of off-axis utilization from an ergonomic standpoint.
In fact, the angle of slope of the flat plate 2 with respect to the axis Z0 can be increased and may exceed the value of 45~ which is usually adopted in conven-tional solutions with partially transparent treated plates. The structure proposed is therefore less aggressive and becomes easier to mount on a helmet.
~7'711 In the case of a potential application which consists in making use of a head-up visor for a heli-copter, the angle of slope of the flat plate can be maintained at 45, thus making it possible to displace S the screen l to the rear and to increase the field of the system without bringing the tube (CRT) into contact with the transparent wall of the cockpit.
By way of example of construction, the angles indicated can have the following values :
- off-axis angle a of the order of 15 ;
- angle of inclination of the plate 2 to the axis z0 corresponding to the normal direction of vision : of the order of 70 ;
- angle between the axis Z1 and the plate 2 : approx-imately 55 ;
- radius R : 160 mm ;
- field of utilization of the collimated vision :
circular field attaining a value of over 40.
The clear holographic visor hereinabove - 20 described accordingly offers many different advantages including high photometric efficiency, low parasitic image ratio, increased field and resolution, smaller bulk owing to suppression of an image-reforming optical system, improved ergonomy by increased inclination of ~he flat plate.
One example of application is given in FIG. 4 ~$771~
in regard to a helmet-mounted visor involving the use of a liquid-crystal matrix 1 illuminated by means of a light source (not shown in the drawings but either external or carried by the helmet~. ~ bundle of fibers 11 transmits the light radiation from the source to the rear of the matrix after reflection from a reflecting mirror 10.
This assembly can be transposed to a heli-copter cabin or cockpit with, if necessary, a steeper inclination of the flat plate 2 in order to facilitate installation of a large-size imager.
Claims (10)
1. A clear holographic visor comprising a generator for producing a light image to be collimated, an optical collimating and combining assembly in which are grouped together a flat holographic plate and a spherical holographic plate for providing a view of the collimated image superimposed on the landscape, the radiation of the light image being reflected from the flat plate to the spherical plate which is employed off the axis and the hologram of which produces collimation of the image at infinity, the hologram of the spherical plate being determined by means of a computer and recorded by making use of a digital hologram in order to minimize aberrations and to produce for the field of utilization which is contemplated an observation pupil at a distance substantially equal to the focal distance with respect to the apex of the spherical mirror.
2. A visor according to claim 1, wherein the holographic flat plate is made up of a hologram between a support plate and a sealing plate, said sealing plate being of small thickness in order to obtain parasitic reflection from the front face of said sealing plate which is very close to the useful radiation diffracted by the hologram.
3. A visor according to claim 1, wherein the holographic spherical mirror has a radius of curvature of the order of 160 millimeters and produces collimation in a pupil zone having a diameter of approximately 15 mm.
4. A visor according to claim 2, wherein the holographic spherical mirror has a radius of curvature of the order of 160 mm and produces collimation in a pupil zone having a diameter of approximately 15 mm.
5. A visor according to claim 1, wherein the spherical mirror is located off-axis at an angular distance of approximately 15°.
6. A visor according to claim 2, wherein the off-axis angular distance of the spherical mirror is approximately 15°.
7. A visor according to claim 3, wherein said field of utilization corresponding to a view of the collimated image is circular and approximately ? 20°.
8. A visor according to claim 7, wherein the off-axis angular distance of the spherical mirror is approximately 15°.
9. A visor according to claim 4, wherein said field of utilization corresponding to a view of the collimated image is circular and approximately ? 20°.
10. A visor according to claim 9, wherein the off-axis angular distance of the spherical mirror is approximately 15°.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8705702 | 1987-04-22 | ||
| FR8705702A FR2614434B1 (en) | 1987-04-22 | 1987-04-22 | HELMET-MOUNTED CLEAR VIEWFINDER |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1297711C true CA1297711C (en) | 1992-03-24 |
Family
ID=9350376
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000564759A Expired - Lifetime CA1297711C (en) | 1987-04-22 | 1988-04-21 | Clear holographic helmet visor |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4874214A (en) |
| EP (1) | EP0288365B1 (en) |
| CA (1) | CA1297711C (en) |
| DE (1) | DE3878581T2 (en) |
| FR (1) | FR2614434B1 (en) |
Families Citing this family (71)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IL86001A0 (en) * | 1988-04-07 | 1988-09-30 | Yonatan Gerlitz | Motorcycle data display apparatus |
| EP0365406B1 (en) * | 1988-10-21 | 1993-09-29 | Thomson-Csf | Optical collimating system for a helmet visual |
| FR2648573B1 (en) * | 1989-06-14 | 1991-08-30 | Thomson Csf | VISUALIZATION DEVICE FOR A VIEW OF AN ERGONOMIC HELMET WITH A LARGE FIELD OF OBSERVATION |
| GB8924831D0 (en) * | 1989-11-03 | 1990-04-25 | Marconi Gec Ltd | Helmet mounted display |
| US5071210A (en) * | 1989-12-28 | 1991-12-10 | Apa Optics, Inc. | Sandwich reflection hologram |
| WO1992016867A1 (en) * | 1991-03-12 | 1992-10-01 | B.V. Optische Industrie 'de Oude Delft' | Helmet mountable display system and helmet provided with such a display system |
| FR2675911B1 (en) * | 1991-04-25 | 1994-04-29 | Sextant Avionique | OPTICAL MIXER FOR HELMET VISUAL. |
| US5257094A (en) * | 1991-07-30 | 1993-10-26 | Larussa Joseph | Helmet mounted display system |
| US5303085A (en) * | 1992-02-07 | 1994-04-12 | Rallison Richard D | Optically corrected helmet mounted display |
| US5864326A (en) * | 1992-02-07 | 1999-01-26 | I-O Display Systems Llc | Depixelated visual display |
| US6097543A (en) | 1992-02-07 | 2000-08-01 | I-O Display Systems Llc | Personal visual display |
| GB9213603D0 (en) * | 1992-06-26 | 1992-10-07 | Marconi Gec Ltd | Helmet mounted display systems |
| JP3262287B2 (en) * | 1992-07-24 | 2002-03-04 | 日本フィリップス株式会社 | Display system |
| DE69332090T2 (en) * | 1992-09-03 | 2002-10-17 | Denso Corp | holography |
| US5526022A (en) | 1993-01-06 | 1996-06-11 | Virtual I/O, Inc. | Sourceless orientation sensor |
| US5537253A (en) * | 1993-02-01 | 1996-07-16 | Honeywell Inc. | Head mounted display utilizing diffractive optical elements |
| US5539578A (en) * | 1993-03-02 | 1996-07-23 | Olympus Optical Co., Ltd. | Image display apparatus |
| FR2709854B1 (en) * | 1993-09-07 | 1995-10-06 | Sextant Avionique | Visualization device with optimized colors. |
| JP3382683B2 (en) * | 1993-10-22 | 2003-03-04 | オリンパス光学工業株式会社 | Concentric optical system |
| US5991087A (en) * | 1993-11-12 | 1999-11-23 | I-O Display System Llc | Non-orthogonal plate in a virtual reality or heads up display |
| WO1995021395A1 (en) * | 1994-02-07 | 1995-08-10 | Virtual I/O, Inc. | Personal visual display system |
| US6160666A (en) * | 1994-02-07 | 2000-12-12 | I-O Display Systems Llc | Personal visual display system |
| US5734505A (en) * | 1994-05-27 | 1998-03-31 | Olympus Optical Co., Ltd. | Visual display apparatus |
| US7262919B1 (en) | 1994-06-13 | 2007-08-28 | Canon Kabushiki Kaisha | Head-up display device with curved optical surface having total reflection |
| NL9401110A (en) * | 1994-07-01 | 1996-02-01 | Optische Ind Oede Oude Delftoe | Display system designed to superimpose three images to obtain a mixed image. |
| NL9401109A (en) * | 1994-07-01 | 1996-02-01 | Optische Ind Oede Oude Delftoe | Display system intended for mounting on the head or on a helmet and a helmet provided with such a display system. |
| US5903395A (en) * | 1994-08-31 | 1999-05-11 | I-O Display Systems Llc | Personal visual display system |
| JP3486468B2 (en) * | 1994-10-21 | 2004-01-13 | オリンパス株式会社 | Prism optical system |
| JPH08122642A (en) * | 1994-10-26 | 1996-05-17 | Olympus Optical Co Ltd | Optical system |
| US6008947A (en) * | 1994-10-26 | 1999-12-28 | Olympus Optical Co., Ltd. | Optical system comprising a prism having a combined transmission and reflection action, and device therefor |
| JPH08146341A (en) * | 1994-11-25 | 1996-06-07 | Olympus Optical Co Ltd | Image display device |
| FR2730320B1 (en) * | 1995-02-07 | 1997-03-14 | Sextant Avionique | DEVICE FOR FOLDING THE OPTICAL TRACKS OF TWO RIGHT AND LEFT IMAGE PROJECTORS OF A BINOCULAR HELMET VIEWER WITH VISOR PROJECTION |
| US5991085A (en) | 1995-04-21 | 1999-11-23 | I-O Display Systems Llc | Head-mounted personal visual display apparatus with image generator and holder |
| JP3599828B2 (en) | 1995-05-18 | 2004-12-08 | オリンパス株式会社 | Optical device |
| WO1997009652A1 (en) * | 1995-09-06 | 1997-03-13 | B.V. Optische Industrie 'de Oude Delft' | Display system intended to be attached to the head or to a helmet, and a helmet provided with such a display system |
| FR2745917B1 (en) * | 1996-03-08 | 1998-04-03 | Sextant Avionique | VISUALIZATION DEVICE FOR HELMET VIEWFINDER |
| JPH09274144A (en) | 1996-04-02 | 1997-10-21 | Canon Inc | Image display device |
| WO1998021612A1 (en) * | 1996-11-12 | 1998-05-22 | Planop - Planar Optics Ltd | Optical system for alternative or simultaneous direction of light originating from two scenes to the eye of a viewer |
| US6034823A (en) * | 1997-02-07 | 2000-03-07 | Olympus Optical Co., Ltd. | Decentered prism optical system |
| US6266473B1 (en) | 1997-02-07 | 2001-07-24 | Alliedsignal Inc. | Reflective display |
| US5903396A (en) * | 1997-10-17 | 1999-05-11 | I/O Display Systems, Llc | Intensified visual display |
| US6191759B1 (en) * | 1997-12-02 | 2001-02-20 | Gregory J. Kintz | Virtual reality system with a static light emitting surface and magnifying optical system |
| JP2000098293A (en) | 1998-06-19 | 2000-04-07 | Canon Inc | Image observing device |
| FR2784201B1 (en) * | 1998-10-06 | 2003-01-31 | Sextant Avionique | OPTICAL DEVICE FOR A HELMET SIGHT COMPRISING A DIFFRACTIVE MIRROR |
| JP4691744B2 (en) * | 1999-06-11 | 2011-06-01 | コニカミノルタホールディングス株式会社 | Video display device |
| JP4341108B2 (en) * | 1999-07-14 | 2009-10-07 | ソニー株式会社 | Virtual image observation optical device |
| US6490095B2 (en) | 2000-03-23 | 2002-12-03 | Canon Kabushiki Kaisha | Image display apparatus |
| JP4387554B2 (en) | 2000-04-28 | 2009-12-16 | キヤノン株式会社 | Image display device and image display system |
| JP2001311904A (en) | 2000-04-28 | 2001-11-09 | Canon Inc | Device and system for image display |
| JP4194218B2 (en) | 2000-04-28 | 2008-12-10 | キヤノン株式会社 | Image display device and image display system |
| JP4604379B2 (en) * | 2000-09-11 | 2011-01-05 | コニカミノルタホールディングス株式会社 | Video display device |
| JP4583569B2 (en) * | 2000-09-22 | 2010-11-17 | オリンパス株式会社 | Observation optical system and imaging optical system |
| JP2002122783A (en) | 2000-10-13 | 2002-04-26 | Olympus Optical Co Ltd | Observation optical system, image pickup optical system and device using those |
| JP4812181B2 (en) | 2001-04-20 | 2011-11-09 | オリンパス株式会社 | Observation optical system, imaging optical system, and apparatus using the same |
| JP4751532B2 (en) | 2001-07-03 | 2011-08-17 | 大日本印刷株式会社 | Optical system and apparatus using the same |
| US7019909B2 (en) * | 2001-11-14 | 2006-03-28 | Canon Kabushiki Kaisha | Optical system, image display apparatus, and image taking apparatus |
| US7012756B2 (en) * | 2001-11-14 | 2006-03-14 | Canon Kabushiki Kaisha | Display optical system, image display apparatus, image taking optical system, and image taking apparatus |
| JP4039045B2 (en) * | 2001-11-26 | 2008-01-30 | コニカミノルタホールディングス株式会社 | BANDPASS FILTER AND VIDEO DISPLAY DEVICE |
| FR2858068A1 (en) * | 2003-07-25 | 2005-01-28 | Thales Sa | Head-up display visor has image source comprising imager, optical projection and diffusing screen |
| US7150531B2 (en) * | 2003-08-26 | 2006-12-19 | The Regents Of The University Of California | Autostereoscopic projection viewer |
| US7133207B2 (en) * | 2004-02-18 | 2006-11-07 | Icuiti Corporation | Micro-display engine |
| GB2415266A (en) * | 2004-06-19 | 2005-12-21 | Francis * Snape Richard | Head up display |
| ES2386724T3 (en) | 2005-12-15 | 2012-08-28 | Saab Ab | High head display |
| WO2009077803A1 (en) * | 2007-12-17 | 2009-06-25 | Nokia Corporation | Exit pupil expanders with spherical and aspheric substrates |
| US8371705B2 (en) * | 2008-03-11 | 2013-02-12 | The United States Of America As Represented By The Secretary Of The Army | Mirrors and methods of making same |
| FR3028325B1 (en) * | 2014-11-06 | 2016-12-02 | Thales Sa | CROSS OPTICAL HEAD VISUALIZATION SYSTEM |
| US10802190B2 (en) * | 2015-12-17 | 2020-10-13 | Covestro Llc | Systems, devices, and methods for curved holographic optical elements |
| JP7375374B2 (en) * | 2019-08-28 | 2023-11-08 | セイコーエプソン株式会社 | Virtual image display device and light guide device |
| PL241407B1 (en) | 2019-10-16 | 2022-09-26 | Seemore Spółka Z Ograniczoną Odpowiedzialnością | Helmet or headpiece visor |
| CN115616788A (en) * | 2022-12-02 | 2023-01-17 | 杭州光粒科技有限公司 | Holographic optical module, near-to-eye display system and augmented reality wearing equipment |
| CN115542558B (en) * | 2022-12-02 | 2024-01-26 | 杭州光粒科技有限公司 | Holographic polarization optical module, near-to-eye display system and augmented reality wearing equipment |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3940204A (en) * | 1975-01-23 | 1976-02-24 | Hughes Aircraft Company | Optical display systems utilizing holographic lenses |
| US4245882A (en) * | 1977-11-04 | 1981-01-20 | Environmental Research Institute Of Michigan | Doubly modulated on-axis thick hologram optical element |
| US4218111A (en) * | 1978-07-10 | 1980-08-19 | Hughes Aircraft Company | Holographic head-up displays |
| IN152994B (en) * | 1978-09-15 | 1984-05-19 | Elliott Brothers London Ltd | |
| FR2526553B1 (en) * | 1980-01-22 | 1987-01-30 | Elliott Brothers London Ltd | DISPLAY DEVICE FOR HIGH HEAD PILOT COLLIMATOR |
| US4530564A (en) * | 1980-08-18 | 1985-07-23 | Hughes Aircraft Company | Method and apparatus for production of holographic optical elements |
| US4412719A (en) * | 1981-04-10 | 1983-11-01 | Environmental Research Institute Of Michigan | Method and article having predetermined net reflectance characteristics |
| US4458978A (en) * | 1981-06-01 | 1984-07-10 | Hughes Aircraft Company | Double beam systems for forming improved holograms |
| US4458977A (en) * | 1981-06-01 | 1984-07-10 | Hughes Aircraft Company | Systems for forming improved reflection holograms with a single beam |
| US4456328A (en) * | 1981-06-01 | 1984-06-26 | Hughes Aircraft Company | Systems for forming improved diffusion holograms |
| US4582389A (en) * | 1982-02-18 | 1986-04-15 | Flight Dynamics, Inc. | Holographic device |
| US4447128A (en) * | 1982-12-03 | 1984-05-08 | Hughes Aircraft Company | Diffraction head up display solar radiation filter |
| US4497534A (en) * | 1983-02-28 | 1985-02-05 | International Business Machines Corporation | Holographic optical head |
| US4669810A (en) * | 1984-02-03 | 1987-06-02 | Flight Dynamics, Inc. | Head up display system |
| IL79391A (en) * | 1985-08-14 | 1994-06-24 | Hughes Aircraft Co | Graded index aspheric combiners and display system utilizing same |
| DE3532120A1 (en) * | 1985-09-10 | 1987-03-19 | Ver Glaswerke Gmbh | WINDSHIELD WITH A REFLECTIVE DEVICE FOR MIRRORING OPTICAL SIGNALS INTO THE FIELD OF THE DRIVER |
-
1987
- 1987-04-22 FR FR8705702A patent/FR2614434B1/en not_active Expired
-
1988
- 1988-04-15 DE DE8888400917T patent/DE3878581T2/en not_active Expired - Fee Related
- 1988-04-15 EP EP88400917A patent/EP0288365B1/en not_active Expired - Lifetime
- 1988-04-18 US US07/182,448 patent/US4874214A/en not_active Expired - Lifetime
- 1988-04-21 CA CA000564759A patent/CA1297711C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0288365B1 (en) | 1993-02-24 |
| DE3878581T2 (en) | 1993-06-09 |
| EP0288365A1 (en) | 1988-10-26 |
| FR2614434A1 (en) | 1988-10-28 |
| DE3878581D1 (en) | 1993-04-01 |
| US4874214A (en) | 1989-10-17 |
| FR2614434B1 (en) | 1989-06-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1297711C (en) | Clear holographic helmet visor | |
| US5124821A (en) | Large-field holographic binocular helmet visor | |
| US4830464A (en) | Wide field high optical efficiency display device | |
| JP2746697B2 (en) | Collimating optical system, especially for helmet display devices | |
| US5576887A (en) | Head gear display system using off-axis image sources | |
| US5537253A (en) | Head mounted display utilizing diffractive optical elements | |
| US5050962A (en) | Display device for ergonomic sights with a large field of observation | |
| EP0298119B1 (en) | Coma-control plate in relay lens | |
| US4582389A (en) | Holographic device | |
| US5257094A (en) | Helmet mounted display system | |
| EP0650605B1 (en) | Helmet-mounted optical systems | |
| EP0284389B1 (en) | Helmet mounted display systems | |
| US6236511B1 (en) | Beam combining optical element | |
| US5673151A (en) | Image correction in virtual reality and heads up displays | |
| US6788442B1 (en) | Optical device for helmet visor comprising a diffractive mirror | |
| US4763990A (en) | Head up display system | |
| US4669810A (en) | Head up display system | |
| US3940204A (en) | Optical display systems utilizing holographic lenses | |
| EP0305096B1 (en) | Optical system for head-up displays | |
| US5684634A (en) | Head-up displays | |
| GB2161615A (en) | A holographic display system | |
| EP1619536A1 (en) | Image combiner and image display | |
| US4993788A (en) | Head-up display systems | |
| GB2123974A (en) | Improvements in or relating to head-up displays | |
| US4730912A (en) | Distortionless sight utilizing holographic components |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |