US20150115032A1 - Decoding dpm indicia with polarized illumination - Google Patents
Decoding dpm indicia with polarized illumination Download PDFInfo
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- US20150115032A1 US20150115032A1 US14/064,115 US201314064115A US2015115032A1 US 20150115032 A1 US20150115032 A1 US 20150115032A1 US 201314064115 A US201314064115 A US 201314064115A US 2015115032 A1 US2015115032 A1 US 2015115032A1
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- light
- dpm
- linear polarizer
- indicia
- lens arrangement
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
- G06K7/10821—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices
- G06K7/10831—Arrangement of optical elements, e.g. lenses, mirrors, prisms
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
- G06K7/10712—Fixed beam scanning
- G06K7/10722—Photodetector array or CCD scanning
- G06K7/10732—Light sources
Definitions
- the present disclosure relates generally to imaging-based barcode scanners.
- a barcode is a coded pattern of graphical indicia comprised of a series of bars and spaces of varying widths. In a barcode, the bars and spaces have different light reflecting characteristics. Some of the barcodes have a one-dimensional structure in which bars and spaces are spaced apart in one direction to form a row of patterns. Examples of one-dimensional barcodes include Uniform Product Code (UPC), which is typically used in retail store sales. Some of the barcodes have a two-dimensional structure in which multiple rows of bar and space patterns are vertically stacked to form a single barcode. Examples of two-dimensional barcodes include Code 49 and PDF417.
- UPC Uniform Product Code
- imaging-based barcode readers systems that use one or more imaging sensors for reading and decoding barcodes are typically referred to as imaging-based barcode readers, imaging scanners, or imaging readers.
- a imaging sensor generally includes a plurality of photosensitive elements or pixels aligned in one or more arrays. Examples of imaging sensors include charged coupled devices (CCD) or complementary metal oxide semiconductor (CMOS) imaging chips.
- CCD charged coupled devices
- CMOS complementary metal oxide semiconductor
- FIG. 1 shows an imaging scanner in accordance with some embodiments.
- FIG. 2 is a schematic of an imaging scanner in accordance with some embodiments.
- FIG. 3 is a schematic of an imaging scanner 50 that is capable to decode the DPM indicia in accordance with some embodiments.
- a method of decoding a Direct Part Marking (DPM) indicia on a target object includes the following: (1) generating a polarized illumination light by passing light from an illumination light source through a first linear polarizer; (2) illuminating the DPM indicia on the target object with the polarized illumination; (3) detecting light scattered from the DPM indicia through a second linear polarizer with photosensitive elements in an imaging sensor during a time period when the target object is illuminated by the polarized illumination to capture an image of the DPM indicia though an imaging lens arrangement while preventing at least 80% of onetime scattered light caused by the target object from entering the imaging lens arrangement; and (4) processing the image of the DPM indicia to decode the DPM indicia.
- DPM Direct Part Marking
- FIG. 1 shows an imaging scanner 50 in accordance with some embodiments.
- the imaging scanner 50 has a window 56 and a housing 58 with a handle.
- the imaging scanner 50 also has a base 52 for supporting itself on a countertop.
- the imaging scanner 50 can be used in a hands-free mode as a stationary workstation when it is placed on the countertop.
- the imaging scanner 50 can also be used in a handheld mode when it is picked up off the countertop and held in an operator's hand.
- products can be slid, swiped past, or presented to the window 56 .
- the imaging scanner 50 In the handheld mode, the imaging scanner 50 can be moved towards a barcode on a product, and a trigger 54 can be manually depressed to initiate imaging of the barcode.
- the base 52 can be omitted, and the housing 58 can also be in other shapes.
- a cable is also connected to the base 52 .
- the imaging scanner 50 can be powered by an on-board battery and it can communicate with a remote host by a wireless link.
- FIG. 2 is a schematic of an imaging scanner 50 in accordance with some embodiments.
- the imaging scanner 50 in FIG. 2 includes the following components: (1) an imaging sensor 62 positioned behind an imaging lens arrangement 60 ; (2) an illuminating lens arrangement 70 positioned in front of an illumination source 72 ; (3) an aiming lens arrangement 80 positioned in front of an aiming light source 82 ; and (4) a controller 90 .
- the imaging lens arrangement 60 , the illuminating lens arrangement 70 , and the aiming lens arrangement 80 are positioned behind the window 56 .
- the imaging sensor 62 is mounted on a printed circuit board 91 in the imaging scanner.
- the imaging sensor 62 can be a CCD or a CMOS imaging device.
- the imaging sensor 62 generally includes multiple pixel elements. These multiple pixel elements can be formed by a one-dimensional array of photosensitive elements arranged linearly in a single row. These multiple pixel elements can also be formed by a two-dimensional array of photosensitive elements arranged in mutually orthogonal rows and columns.
- the imaging sensor 62 is operative to detect light captured by an imaging lens arrangement 60 along an optical path or axis 61 through the window 56 .
- the imaging sensor 62 and the imaging lens arrangement 60 are designed to operate together for capturing light scattered or reflected from a barcode 40 as pixel data over a two-dimensional field of view (FOV).
- FOV two-dimensional field of view
- the barcode 40 generally can be located anywhere in a working range of distances between a close-in working distance (WD1) and a far-out working distance (WD2). In one specific implementation, WD1 is in a close proximity to the window 56 , and WD2 is about a couple of feet from the window 56 .
- the illuminating lens arrangement 70 and the illumination source 72 are designed to operate together for generating an illuminating light towards the barcode 40 during an illumination time period.
- the illumination source 72 can include one or more light emitting diodes (LED).
- the illumination source 72 can also include a laser or other kind of light sources.
- the aiming lens arrangement 80 and the aiming light source 82 are designed to operate together for generating a visible aiming light pattern towards the barcode 40 .
- the aiming light source 82 can include one or more light emitting diodes (LED).
- the aiming light source 82 can also include a laser, LED, or other kind of light sources.
- the controller 90 such as a microprocessor, is operatively connected to the imaging sensor 62 , the illumination source 72 , and the aiming light source 82 for controlling the operation of these components.
- the controller 90 can also be used to control other devices in the imaging scanner.
- the imaging scanner 50 includes a memory 94 that can be accessible by the controller 90 for storing and retrieving data.
- the controller 90 also includes a decoder for decoding one or more barcodes that are within the field of view (FOV) of the imaging scanner 50 .
- the barcode 40 can be decoded by digitally processing a captured image of the barcode with a microprocessor.
- the controller 90 sends a command signal to energize the illumination source 72 for a predetermined illumination time period.
- the controller 90 then exposes the imaging sensor 62 to capture an image of the barcode 40 .
- the captured image of the barcode 40 is transferred to the controller 90 as pixel data.
- Such pixel data is digitally processed by the decoder in the controller 90 to decode the barcode.
- the information obtained from decoding the barcode 40 is then stored in the memory 94 or sent to other devices for further processing.
- DPM Direct Part Marking
- An important class of substrates is shiny (mirrored or mirror-like) surfaces, especially on metals, because these are notorious difficult to read with a scanner.
- DPM on shiny surfaces some of the scanners are created with a large featureless and diffusive surface facing the front, and illuminated evenly with light, so that the part bearing the DPM can reflect a part of this surface back to the imager in the scanner which can in turn image it with some contrast.
- the extent of this diffusive surface is what makes the scanner operate with ease; the larger the extent, the easier it is to aim the scanner. It is for this reason these DPM scanners are rather large, especially in the front. It is desirable to reduce the size of DPM scanners and desirable to reduce the size of DPM scan-engines.
- FIG. 3 is a schematic of an imaging scanner 50 that is capable to decode the DPM indicia in accordance with some embodiments.
- the DPM indicia to be decoded can be a DPM code 44 formed on a mental surface 48 .
- the imaging scanner 50 includes an imaging lens arrangement 60 having an optical axis 61 , a first linear polarizer 110 , and an illumination light source 72 configured to generate a polarized illumination light 150 by passing light from the illumination light source through the first linear polarizer 110 .
- FIG. 1 is a schematic of an imaging scanner 50 that is capable to decode the DPM indicia in accordance with some embodiments.
- the DPM indicia to be decoded can be a DPM code 44 formed on a mental surface 48 .
- the imaging scanner 50 includes an imaging lens arrangement 60 having an optical axis 61 , a first linear polarizer 110 , and an illumination light source 72 configured to generate a polarized illumination light 150 by passing light from the illumination light source
- the angular distribution of the polarized illumination light 150 are designed in such a way to prevent at least 80% of the polarized illumination light 150 from entering the imaging lens arrangement 60 even if the DPM code 44 and the mental surface 48 are illuminated with almost all of the polarized illumination light projected out of the imaging scanner under the condition that the mental surface 48 is perpendicular the optical axis 61 of the imaging lens arrangement 60 .
- at least 90% of the polarized illumination light 150 can be prevented from entering the imaging lens arrangement 60 .
- at least 95% of the polarized illumination light 150 can be prevented from entering the imaging lens arrangement 60 .
- the imaging scanner also includes a second linear polarizer 120 , an imaging sensor 62 having photosensitive elements configured to detect light (e.g., 171 , 172 , 173 , . . . ) scattered from the DPM indicia 44 through the second linear polarizer 120 during a time period when the target object is illuminated by the polarized illumination 150 to capture an image of the DPM indicia 44 though the imaging lens arrangement 60 .
- the imaging scanner often has a controller that is operative for controlling both the illumination light source 72 and the imaging sensor 62 , and is operative for processing the captured image of the DPM indicia to decode the DPM indicia 44 .
- the first linear polarizer 110 is configured for generating the polarized illumination light 150 as p-wave illumination light; additionally, the second linear polarizer 120 is configured to cause light 172 scattered from the DPM indicia 44 to pass through the second linear polarizer 120 as s-wave light.
- the polarized illumination light can have polarization other than p-wave
- the light passing through the second linear polarizer can have polarization other than s-wave.
- the first linear polarizer can be configured for blocking light with polarization perpendicular to a first polarization direction
- the second linear polarizer can be configured for blocking light with polarization perpendicular to a second polarization direction.
- the first polarization direction and the second polarization direction can be substantially perpendicular to each other; for example, the angle between the first polarization direction and the second polarization direction can be within 20 degrees from 90 degree angle.
- the imaging lens arrangement 60 is positioned between the second linear polarizer 120 and the imaging sensor 62 .
- the second linear polarizer 120 can be positioned between the imaging lens arrangement 60 and the imaging sensor 62 .
- the second linear polarizer 120 can be positioned between the optical components (e.g., lens, aperture, and filters) within the imaging lens arrangement 60 .
- the p-wave illumination 150 are designed to illuminate of the DPM indicia 44 with an incident angle that is sufficiently large with respect to the optical axis 61 of the imaging lens arrangement 60 to prevent at least 80% of onetime scattered light 160 caused by the target object 48 from entering the imaging lens arrangement 60 .
- the onetime scattered light 160 caused by the target object 48 can include light directly reflected by the target object 48 and light scattered only once by the surface of the DPM indicia 44 .
- more than 90% of onetime scattered light 160 caused by the target object 48 can be prevented from entering the imaging lens arrangement 60 .
- more than 95% of onetime scattered light 160 caused by the target object 48 can be prevented from entering the imaging lens arrangement 60 .
- a significant portion of reflected (or weakly scattered) light on metal has the same polarization of incident light.
- a strongly scattered light by barcodes can include near 50% of cross polarized light (S-polarized).
- P-polarized light is filtered out by a polarizer 120 before imaging lens 60 . So at the imaging sensor 62 , the P-polarized specular light is significantly reduced. With this method, the incident light can be close to metal surface and a traditional diffuser in DPM barcode illumination design can be avoided.
- a includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element.
- the terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein.
- the terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%.
- the term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically.
- a device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
- processors such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein.
- processors or “processing devices” such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein.
- FPGAs field programmable gate arrays
- unique stored program instructions including both software and firmware
- an embodiment can be implemented as a computer-readable storage medium having computer readable code stored thereon for programming a computer (e.g., comprising a processor) to perform a method as described and claimed herein.
- Examples of such computer-readable storage mediums include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory.
Abstract
Description
- The present disclosure relates generally to imaging-based barcode scanners.
- Various electro-optical systems have been developed for reading optical indicia, such as barcodes. A barcode is a coded pattern of graphical indicia comprised of a series of bars and spaces of varying widths. In a barcode, the bars and spaces have different light reflecting characteristics. Some of the barcodes have a one-dimensional structure in which bars and spaces are spaced apart in one direction to form a row of patterns. Examples of one-dimensional barcodes include Uniform Product Code (UPC), which is typically used in retail store sales. Some of the barcodes have a two-dimensional structure in which multiple rows of bar and space patterns are vertically stacked to form a single barcode. Examples of two-dimensional barcodes include Code 49 and PDF417.
- Systems that use one or more imaging sensors for reading and decoding barcodes are typically referred to as imaging-based barcode readers, imaging scanners, or imaging readers. A imaging sensor generally includes a plurality of photosensitive elements or pixels aligned in one or more arrays. Examples of imaging sensors include charged coupled devices (CCD) or complementary metal oxide semiconductor (CMOS) imaging chips.
- The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments of concepts that include the claimed invention, and explain various principles and advantages of those embodiments.
-
FIG. 1 shows an imaging scanner in accordance with some embodiments. -
FIG. 2 is a schematic of an imaging scanner in accordance with some embodiments. -
FIG. 3 is a schematic of animaging scanner 50 that is capable to decode the DPM indicia in accordance with some embodiments. - Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
- The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
- A method of decoding a Direct Part Marking (DPM) indicia on a target object. The method includes the following: (1) generating a polarized illumination light by passing light from an illumination light source through a first linear polarizer; (2) illuminating the DPM indicia on the target object with the polarized illumination; (3) detecting light scattered from the DPM indicia through a second linear polarizer with photosensitive elements in an imaging sensor during a time period when the target object is illuminated by the polarized illumination to capture an image of the DPM indicia though an imaging lens arrangement while preventing at least 80% of onetime scattered light caused by the target object from entering the imaging lens arrangement; and (4) processing the image of the DPM indicia to decode the DPM indicia.
-
FIG. 1 shows animaging scanner 50 in accordance with some embodiments. Theimaging scanner 50 has awindow 56 and ahousing 58 with a handle. Theimaging scanner 50 also has abase 52 for supporting itself on a countertop. Theimaging scanner 50 can be used in a hands-free mode as a stationary workstation when it is placed on the countertop. Theimaging scanner 50 can also be used in a handheld mode when it is picked up off the countertop and held in an operator's hand. In the hands-free mode, products can be slid, swiped past, or presented to thewindow 56. In the handheld mode, theimaging scanner 50 can be moved towards a barcode on a product, and atrigger 54 can be manually depressed to initiate imaging of the barcode. In some implementations, thebase 52 can be omitted, and thehousing 58 can also be in other shapes. InFIG. 1 , a cable is also connected to thebase 52. In other implementations, when the cable connected to thebase 52 is omitted, theimaging scanner 50 can be powered by an on-board battery and it can communicate with a remote host by a wireless link. -
FIG. 2 is a schematic of animaging scanner 50 in accordance with some embodiments. Theimaging scanner 50 inFIG. 2 includes the following components: (1) animaging sensor 62 positioned behind animaging lens arrangement 60; (2) anilluminating lens arrangement 70 positioned in front of anillumination source 72; (3) an aiminglens arrangement 80 positioned in front of an aiminglight source 82; and (4) acontroller 90. InFIG. 2 , theimaging lens arrangement 60, theilluminating lens arrangement 70, and the aiminglens arrangement 80 are positioned behind thewindow 56. Theimaging sensor 62 is mounted on a printedcircuit board 91 in the imaging scanner. - The
imaging sensor 62 can be a CCD or a CMOS imaging device. Theimaging sensor 62 generally includes multiple pixel elements. These multiple pixel elements can be formed by a one-dimensional array of photosensitive elements arranged linearly in a single row. These multiple pixel elements can also be formed by a two-dimensional array of photosensitive elements arranged in mutually orthogonal rows and columns. Theimaging sensor 62 is operative to detect light captured by animaging lens arrangement 60 along an optical path oraxis 61 through thewindow 56. Generally, theimaging sensor 62 and theimaging lens arrangement 60 are designed to operate together for capturing light scattered or reflected from abarcode 40 as pixel data over a two-dimensional field of view (FOV). - The
barcode 40 generally can be located anywhere in a working range of distances between a close-in working distance (WD1) and a far-out working distance (WD2). In one specific implementation, WD1 is in a close proximity to thewindow 56, and WD2 is about a couple of feet from thewindow 56. InFIG. 2 , theilluminating lens arrangement 70 and theillumination source 72 are designed to operate together for generating an illuminating light towards thebarcode 40 during an illumination time period. Theillumination source 72 can include one or more light emitting diodes (LED). Theillumination source 72 can also include a laser or other kind of light sources. The aiminglens arrangement 80 and the aiminglight source 82 are designed to operate together for generating a visible aiming light pattern towards thebarcode 40. Such aiming pattern can be used by the operator to accurately aim the imaging scanner at the barcode. The aiminglight source 82 can include one or more light emitting diodes (LED). The aiminglight source 82 can also include a laser, LED, or other kind of light sources. - In
FIG. 2 , thecontroller 90, such as a microprocessor, is operatively connected to theimaging sensor 62, theillumination source 72, and the aiminglight source 82 for controlling the operation of these components. Thecontroller 90 can also be used to control other devices in the imaging scanner. Theimaging scanner 50 includes amemory 94 that can be accessible by thecontroller 90 for storing and retrieving data. In many embodiments, thecontroller 90 also includes a decoder for decoding one or more barcodes that are within the field of view (FOV) of theimaging scanner 50. In some implementations, thebarcode 40 can be decoded by digitally processing a captured image of the barcode with a microprocessor. - In operation, in accordance with some embodiments, the
controller 90 sends a command signal to energize theillumination source 72 for a predetermined illumination time period. Thecontroller 90 then exposes theimaging sensor 62 to capture an image of thebarcode 40. The captured image of thebarcode 40 is transferred to thecontroller 90 as pixel data. Such pixel data is digitally processed by the decoder in thecontroller 90 to decode the barcode. The information obtained from decoding thebarcode 40 is then stored in thememory 94 or sent to other devices for further processing. - The imaging scanners are often used in applications involving Direct Part Marking (DPM). DPM refers to making permanent, machine readable marks in a variety of physical substrates. An important class of substrates is shiny (mirrored or mirror-like) surfaces, especially on metals, because these are notorious difficult to read with a scanner. To make DPM on shiny surfaces easier to read, some of the scanners are created with a large featureless and diffusive surface facing the front, and illuminated evenly with light, so that the part bearing the DPM can reflect a part of this surface back to the imager in the scanner which can in turn image it with some contrast. The extent of this diffusive surface is what makes the scanner operate with ease; the larger the extent, the easier it is to aim the scanner. It is for this reason these DPM scanners are rather large, especially in the front. It is desirable to reduce the size of DPM scanners and desirable to reduce the size of DPM scan-engines.
-
FIG. 3 is a schematic of animaging scanner 50 that is capable to decode the DPM indicia in accordance with some embodiments. As shown inFIG. 3 , the DPM indicia to be decoded can be aDPM code 44 formed on amental surface 48. Theimaging scanner 50 includes animaging lens arrangement 60 having anoptical axis 61, a firstlinear polarizer 110, and anillumination light source 72 configured to generate a polarized illumination light 150 by passing light from the illumination light source through the firstlinear polarizer 110. In the embodiment as shown inFIG. 3 , the angular distribution of the polarized illumination light 150 are designed in such a way to prevent at least 80% of the polarized illumination light 150 from entering theimaging lens arrangement 60 even if theDPM code 44 and themental surface 48 are illuminated with almost all of the polarized illumination light projected out of the imaging scanner under the condition that themental surface 48 is perpendicular theoptical axis 61 of theimaging lens arrangement 60. Under similar condition and in other implementations, at least 90% of the polarized illumination light 150 can be prevented from entering theimaging lens arrangement 60. Under similar condition and in still other implementations, at least 95% of the polarized illumination light 150 can be prevented from entering theimaging lens arrangement 60. - The imaging scanner also includes a second
linear polarizer 120, animaging sensor 62 having photosensitive elements configured to detect light (e.g., 171, 172, 173, . . . ) scattered from theDPM indicia 44 through the secondlinear polarizer 120 during a time period when the target object is illuminated by thepolarized illumination 150 to capture an image of theDPM indicia 44 though theimaging lens arrangement 60. The imaging scanner often has a controller that is operative for controlling both theillumination light source 72 and theimaging sensor 62, and is operative for processing the captured image of the DPM indicia to decode theDPM indicia 44. - In the implementation as shown in
FIG. 3 , the firstlinear polarizer 110 is configured for generating the polarized illumination light 150 as p-wave illumination light; additionally, the secondlinear polarizer 120 is configured to cause light 172 scattered from theDPM indicia 44 to pass through the secondlinear polarizer 120 as s-wave light. In other implementations, the polarized illumination light can have polarization other than p-wave, and the light passing through the second linear polarizer can have polarization other than s-wave. In general, the first linear polarizer can be configured for blocking light with polarization perpendicular to a first polarization direction, and the second linear polarizer can be configured for blocking light with polarization perpendicular to a second polarization direction. The first polarization direction and the second polarization direction can be substantially perpendicular to each other; for example, the angle between the first polarization direction and the second polarization direction can be within 20 degrees from 90 degree angle. - In the implementation as shown in
FIG. 3 , theimaging lens arrangement 60 is positioned between the secondlinear polarizer 120 and theimaging sensor 62. In other implementations, the secondlinear polarizer 120 can be positioned between theimaging lens arrangement 60 and theimaging sensor 62. In still other implementations, the secondlinear polarizer 120 can be positioned between the optical components (e.g., lens, aperture, and filters) within theimaging lens arrangement 60. - In the embodiment as shown in
FIG. 3 , the p-wave illumination 150 are designed to illuminate of theDPM indicia 44 with an incident angle that is sufficiently large with respect to theoptical axis 61 of theimaging lens arrangement 60 to prevent at least 80% of onetime scattered light 160 caused by thetarget object 48 from entering theimaging lens arrangement 60. The onetime scattered light 160 caused by thetarget object 48 can include light directly reflected by thetarget object 48 and light scattered only once by the surface of theDPM indicia 44. In other implementations, more than 90% of onetime scattered light 160 caused by thetarget object 48 can be prevented from entering theimaging lens arrangement 60. In still other implementations, more than 95% of onetime scattered light 160 caused by thetarget object 48 can be prevented from entering theimaging lens arrangement 60. - In
FIG. 3 , a significant portion of reflected (or weakly scattered) light on metal has the same polarization of incident light. But a strongly scattered light by barcodes can include near 50% of cross polarized light (S-polarized). P-polarized light is filtered out by apolarizer 120 before imaginglens 60. So at theimaging sensor 62, the P-polarized specular light is significantly reduced. With this method, the incident light can be close to metal surface and a traditional diffuser in DPM barcode illumination design can be avoided. - In the foregoing specification, specific embodiments have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.
- The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
- Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “has”, “having,” “includes”, “including,” “contains”, “containing” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
- It will be appreciated that some embodiments may be comprised of one or more generic or specialized processors (or “processing devices”) such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used.
- Moreover, an embodiment can be implemented as a computer-readable storage medium having computer readable code stored thereon for programming a computer (e.g., comprising a processor) to perform a method as described and claimed herein. Examples of such computer-readable storage mediums include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.
- The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.
Claims (20)
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