CA1316022C - Real-time color comparator - Google Patents
Real-time color comparatorInfo
- Publication number
- CA1316022C CA1316022C CA000582489A CA582489A CA1316022C CA 1316022 C CA1316022 C CA 1316022C CA 000582489 A CA000582489 A CA 000582489A CA 582489 A CA582489 A CA 582489A CA 1316022 C CA1316022 C CA 1316022C
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- Prior art keywords
- sample
- array
- color
- photodetectors
- linear array
- Prior art date
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- Expired - Fee Related
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- 230000003595 spectral effect Effects 0.000 claims abstract description 56
- 230000003287 optical effect Effects 0.000 claims abstract description 45
- 239000000835 fiber Substances 0.000 claims description 27
- 238000009826 distribution Methods 0.000 claims description 13
- 239000013307 optical fiber Substances 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 8
- 239000006185 dispersion Substances 0.000 claims description 7
- 238000003384 imaging method Methods 0.000 claims description 6
- 239000000470 constituent Substances 0.000 abstract description 2
- 230000009977 dual effect Effects 0.000 abstract 1
- 239000003086 colorant Substances 0.000 description 7
- 238000005286 illumination Methods 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000004456 color vision Effects 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
- G01J3/0218—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using optical fibers
- G01J3/0221—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using optical fibers the fibers defining an entry slit
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/2803—Investigating the spectrum using photoelectric array detector
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
- G01J3/502—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors using a dispersive element, e.g. grating, prism
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J2003/466—Coded colour; Recognition of predetermined colour; Determining proximity to predetermined colour
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
- G01J3/463—Colour matching
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N2021/1748—Comparative step being essential in the method
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/08—Optical fibres; light guides
Abstract
ABSTRACT
A real-time color comparator which performs color comparisons of sample objects to a reference color for the purpose of identification, sorting or matching. Two optical paths are positioned to collect the light from a reference object and a sample object and the light outputs from the two paths are directed onto a spectral dispersive element shown in the form of a concave diffraction grating that decomposes each light signal into its spectral constituents which are imaged on a dual photodetector array. The color signature from the reference and the color signature from the sample are compared.
A real-time color comparator which performs color comparisons of sample objects to a reference color for the purpose of identification, sorting or matching. Two optical paths are positioned to collect the light from a reference object and a sample object and the light outputs from the two paths are directed onto a spectral dispersive element shown in the form of a concave diffraction grating that decomposes each light signal into its spectral constituents which are imaged on a dual photodetector array. The color signature from the reference and the color signature from the sample are compared.
Description
~ 3 ~ 2 REAL-TIME COLOR COMPARATOR
This invention is directed to the field of real-time color comparators which performs color 5comparison of sample objects to reference colors for the purpose of identification, sorting or matching.
Manufacturing and process `- automation sometimes require the determination of whether a coloreù sample matches that of a colored reference.
lOFor example~ if the reference color represents the desired output characteristic o~ a continuous process ~e~g., paint mixing, chemical reactions, bakingJ, the real-time color comparator can be used as an endpoint detector for the process.
15In the present invention use is made of spectral reflectance distributions of sample versus~
; reference colors, that is, the colors per se are compared indirectly. In the present invention a reference color obiect and a sample object are 20similarly illuminated. Two optical paths are positioned to observ~ the reference object and the sample object; in the embodiment disclosed separate optical flbers are utilized, a reference fiber to observe the reference object and a sample fiber to 25observe the sample~objeot. The outputs from the two .
<~
.
1311 ~022 fibers are directed onto a spectral dispersive element shown in the form of a concave diffraction grating that decomposes each light signal into its spectral constituents which are imaged on a photodetector array. Photodiodes in the array generate an analogue signal which represents the color signature of the object. The color signature from the reference and the color signature from the sample are compared.
In accordance with the present invention there is provided input mechanism to a color comparator apparatus lo comprising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an output end, said input end being adapted to collect and trans-mit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors;
spectral dispersive element means for imaging and spectral dispersion of the output end color emanations of said first and second optical paths onto said photodetector array;
means positioning said first optical path means output end to direct reference light emanating therefrom to said spectral dispersive element means;
means positioning said second optical path means output end to direct sample light emanating therefrom to said spectral dispersive element means;
the reference diffracted light from said spectral disper-sive element means being directed onto s-aid reference linear array of photodetectors and the sample diffracted light Erom said spectral dispersive element means being directed onto said sample linear array of photodetectors, said reference array and :~31~2~
2a 64159-1037 sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color; and comparator means for s.imultaneously receiving the plural-ity of light intensity signals from the reference linear array and from the sample linear array and subtracting said signals to get a difference between reference and sample for direct spectral component comparison.
In accordance with the present invention there is further provided input mechanism to a color comparator appara-tus comprising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical pat~ means having an input end and an out-put endl =aid input end being adapt=d to collect and transmit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors, said photodetector array also having a plurality of linear apertures with one of said reference photo- .
detector= and one of said sample photodetectors of said reference linear array and of said sample linear array behind each aperture;
spectral dispersive element means for imaging and spectral dispersion of the output end color emanations of said firs~ and second optical paths onto said photodetector array;
means positioning said first optical path means output end to direct reference light emanating therefrom to said spectral dispersive element means;
means positioning said second optical path means output end to direct sample light emanating therefrom to said spectral dispersive element means; and i .,~
~ 3 ~ 2 2b 64159-1037 the reference dif~racted light from sald spectral dlsper-slve element means belng dlrected onto sald reference llnear array of photodetectors and the sample dlffracted llght from said spectral disperslve element means belng directed onto said sample llnear array of photodetectors, said reference array and sample array of photodetectors produclng a plurality of llght lntensity slgnals representative of the spectral distrlbution o~ the re~erence ob~ect color and the sample ob~ect color.
In accordance wlth the present inventlon there is further provlded lnput mechanlsm to a color comparator appara-tus comprlslng:
~ irst optlcal path means havlng an lnput end and an output end, sald lnput end being adapted to collect and tran~mlt the color o~ a reference ob~ect to sald output end~
second optlcal path means havlng an lnput end and an out-put end, said lnput end being adaptsd to collect and transmlt : the color of a sample ob~ect to said output end, a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array o~ photodetectors;
spectral disperslve element means for imaglng and spectral dispersion of the output end color emanations of sald flrst and second optical paths onto said photodetector array, sald spec-tral dlsperslve element means being ln the form of a single concave dlffraction grating which has a reference area and a qample area separated from one another on the concave dlffrac-tion grating~
means posltloning sald first optical path means output end to direct reference llght emanating therefrom to said gratlng reference areal mean~ posltloning said second optical path means output en~ to direct sample li~ht emanatlng therefrom to sail~ ~ratlng sample area) and ,(~
2c 64159-1037 the reference diffracted light from said grating reference area being directed onto said reference linear array of photo-detectors from a first solid angle and the sample diffracted light from said grating sample area being directed onto said sample linear array of photodetectors from a different solid angle, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample ob~ect color.
In accordance with the present invention there is further provided input mechanism to a color comparator appara-tus comprising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
sscond optical path means having an input end and an out-put end, said input end being adapted to~collect and transmit the color of a sample object to said output end;
spectral dispersive element means in the form of a single concave diffraction grating, said grating including a reference area and a sample area which are spatially separated one from the o$her on said concave diffraction grating;
means positioning said first optical path means output end to direct reference light emanating therefrom to the reference area on said concave diffraction grating;
means positioning said second optical path means output end to direct sample light emanating therefrom to the sample area on said concave diffraction grating;
a photodetector array, said photodetector array having a reference linear array of photodetectors and adjacent thereto a sample linear array of photodetectors;
means directing diffracted light from said reference area onto said reference linear array of photodetectors from a first ~3~22 2d 64159-1037 solid angle and directing diffracted light from said sample area onto said sample linear array of photodetectors from a different solid angle, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the referencP
object color and the sample object color.
In accordance with the present invention there is further provided real-time color comparator apparatus compri-sing:
a reference optical fiber having an input end and an out-put end, said inpuk end being adapted to observe and transmit the color of a reference object;
a sample optical fiber ha~ing an input end and an output end, said input end being adapted to observe and transmit the color of a sample object;
a single concave diffraction grating;
means positioning said reference fiber output end to direct light emanating from the output end of said reference optical fiber to a first reference area on said concave dif-0 fractive grating;
means positioning said sample ~iber output end to direc~
sample light emanating therefrom to a second sample area on :
said concave diffraction grating, the second sample area being spatially separated from said first reference area on said con-cave grating;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample Iinear array of photodetectors;
means focusing diffracted light from said first reference area onto said reference linear array of photodetectors ancl focusing dif~racted light from said second sample area onto said sample linear array of photodetectors, said re~erenc~
array and sample array of photodetectors producing a plurality 2 ~
2e 64159-1037 of light intensity signals represen$ative of the spectral distribution of the reference object color and the sample object color.
BRIEF DESCRIPTION OF T~E DRAW;[NGS
Figure 1 of the drawing is a diagrammatic presenta-tion of an embodiment of the invention.
Figure 2 shows an enlargement of the optical fibers at the output end where the end faces are flat and orthogonal to their axes.
Figure 3 is like Figure 2 for another embodiment of the invention where the end faces are flat and nonor$hogonal.
Figure 4 shows an enlargement of a portion of the sensor structure of Figure 1.
Figure 5 shows an enlargement of a portion of Figure 4.
Figure 6 shows another embodiment of the real-time color comparator.
Figure 7 shows an enlargement of the sensor aperture cf the embodiment of Figure 6.
This invention is directed to the field of real-time color comparators which performs color 5comparison of sample objects to reference colors for the purpose of identification, sorting or matching.
Manufacturing and process `- automation sometimes require the determination of whether a coloreù sample matches that of a colored reference.
lOFor example~ if the reference color represents the desired output characteristic o~ a continuous process ~e~g., paint mixing, chemical reactions, bakingJ, the real-time color comparator can be used as an endpoint detector for the process.
15In the present invention use is made of spectral reflectance distributions of sample versus~
; reference colors, that is, the colors per se are compared indirectly. In the present invention a reference color obiect and a sample object are 20similarly illuminated. Two optical paths are positioned to observ~ the reference object and the sample object; in the embodiment disclosed separate optical flbers are utilized, a reference fiber to observe the reference object and a sample fiber to 25observe the sample~objeot. The outputs from the two .
<~
.
1311 ~022 fibers are directed onto a spectral dispersive element shown in the form of a concave diffraction grating that decomposes each light signal into its spectral constituents which are imaged on a photodetector array. Photodiodes in the array generate an analogue signal which represents the color signature of the object. The color signature from the reference and the color signature from the sample are compared.
In accordance with the present invention there is provided input mechanism to a color comparator apparatus lo comprising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an output end, said input end being adapted to collect and trans-mit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors;
spectral dispersive element means for imaging and spectral dispersion of the output end color emanations of said first and second optical paths onto said photodetector array;
means positioning said first optical path means output end to direct reference light emanating therefrom to said spectral dispersive element means;
means positioning said second optical path means output end to direct sample light emanating therefrom to said spectral dispersive element means;
the reference diffracted light from said spectral disper-sive element means being directed onto s-aid reference linear array of photodetectors and the sample diffracted light Erom said spectral dispersive element means being directed onto said sample linear array of photodetectors, said reference array and :~31~2~
2a 64159-1037 sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color; and comparator means for s.imultaneously receiving the plural-ity of light intensity signals from the reference linear array and from the sample linear array and subtracting said signals to get a difference between reference and sample for direct spectral component comparison.
In accordance with the present invention there is further provided input mechanism to a color comparator appara-tus comprising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical pat~ means having an input end and an out-put endl =aid input end being adapt=d to collect and transmit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors, said photodetector array also having a plurality of linear apertures with one of said reference photo- .
detector= and one of said sample photodetectors of said reference linear array and of said sample linear array behind each aperture;
spectral dispersive element means for imaging and spectral dispersion of the output end color emanations of said firs~ and second optical paths onto said photodetector array;
means positioning said first optical path means output end to direct reference light emanating therefrom to said spectral dispersive element means;
means positioning said second optical path means output end to direct sample light emanating therefrom to said spectral dispersive element means; and i .,~
~ 3 ~ 2 2b 64159-1037 the reference dif~racted light from sald spectral dlsper-slve element means belng dlrected onto sald reference llnear array of photodetectors and the sample dlffracted llght from said spectral disperslve element means belng directed onto said sample llnear array of photodetectors, said reference array and sample array of photodetectors produclng a plurality of llght lntensity slgnals representative of the spectral distrlbution o~ the re~erence ob~ect color and the sample ob~ect color.
In accordance wlth the present inventlon there is further provlded lnput mechanlsm to a color comparator appara-tus comprlslng:
~ irst optlcal path means havlng an lnput end and an output end, sald lnput end being adapted to collect and tran~mlt the color o~ a reference ob~ect to sald output end~
second optlcal path means havlng an lnput end and an out-put end, said lnput end being adaptsd to collect and transmlt : the color of a sample ob~ect to said output end, a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array o~ photodetectors;
spectral disperslve element means for imaglng and spectral dispersion of the output end color emanations of sald flrst and second optical paths onto said photodetector array, sald spec-tral dlsperslve element means being ln the form of a single concave dlffraction grating which has a reference area and a qample area separated from one another on the concave dlffrac-tion grating~
means posltloning sald first optical path means output end to direct reference llght emanating therefrom to said gratlng reference areal mean~ posltloning said second optical path means output en~ to direct sample li~ht emanatlng therefrom to sail~ ~ratlng sample area) and ,(~
2c 64159-1037 the reference diffracted light from said grating reference area being directed onto said reference linear array of photo-detectors from a first solid angle and the sample diffracted light from said grating sample area being directed onto said sample linear array of photodetectors from a different solid angle, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample ob~ect color.
In accordance with the present invention there is further provided input mechanism to a color comparator appara-tus comprising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
sscond optical path means having an input end and an out-put end, said input end being adapted to~collect and transmit the color of a sample object to said output end;
spectral dispersive element means in the form of a single concave diffraction grating, said grating including a reference area and a sample area which are spatially separated one from the o$her on said concave diffraction grating;
means positioning said first optical path means output end to direct reference light emanating therefrom to the reference area on said concave diffraction grating;
means positioning said second optical path means output end to direct sample light emanating therefrom to the sample area on said concave diffraction grating;
a photodetector array, said photodetector array having a reference linear array of photodetectors and adjacent thereto a sample linear array of photodetectors;
means directing diffracted light from said reference area onto said reference linear array of photodetectors from a first ~3~22 2d 64159-1037 solid angle and directing diffracted light from said sample area onto said sample linear array of photodetectors from a different solid angle, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the referencP
object color and the sample object color.
In accordance with the present invention there is further provided real-time color comparator apparatus compri-sing:
a reference optical fiber having an input end and an out-put end, said inpuk end being adapted to observe and transmit the color of a reference object;
a sample optical fiber ha~ing an input end and an output end, said input end being adapted to observe and transmit the color of a sample object;
a single concave diffraction grating;
means positioning said reference fiber output end to direct light emanating from the output end of said reference optical fiber to a first reference area on said concave dif-0 fractive grating;
means positioning said sample ~iber output end to direc~
sample light emanating therefrom to a second sample area on :
said concave diffraction grating, the second sample area being spatially separated from said first reference area on said con-cave grating;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample Iinear array of photodetectors;
means focusing diffracted light from said first reference area onto said reference linear array of photodetectors ancl focusing dif~racted light from said second sample area onto said sample linear array of photodetectors, said re~erenc~
array and sample array of photodetectors producing a plurality 2 ~
2e 64159-1037 of light intensity signals represen$ative of the spectral distribution of the reference object color and the sample object color.
BRIEF DESCRIPTION OF T~E DRAW;[NGS
Figure 1 of the drawing is a diagrammatic presenta-tion of an embodiment of the invention.
Figure 2 shows an enlargement of the optical fibers at the output end where the end faces are flat and orthogonal to their axes.
Figure 3 is like Figure 2 for another embodiment of the invention where the end faces are flat and nonor$hogonal.
Figure 4 shows an enlargement of a portion of the sensor structure of Figure 1.
Figure 5 shows an enlargement of a portion of Figure 4.
Figure 6 shows another embodiment of the real-time color comparator.
Figure 7 shows an enlargement of the sensor aperture cf the embodiment of Figure 6.
-3~ 2 DESCRIPTION
Referring now to the drawing there is shown generally at 10 a color signature sensor in which it is desired to compare the color of a sample object 11 5with the color of a reference object 12. The objects 11 and 12 are given illumination which is similar.
Color perception depends on the spectral energy density of the illumination source, the spectral reflectance distr1bution of the objec~, and the 10spectral responsivity characteristics of the signal acquisition system. This invention deals only with the signal acquisition system and presupposes suitable illumination of both a reference object and a sample object.
15Collecting the light signals 13 and 14 from ; ob~ects 11 and 12 are two essentially identical optical fibers (a sample fiber 15 and a~ reference :~ fiber 16) which route the light signals to a spectral :dispersive element 20, here shovn in the form of a 20:concave diffraction qrating. The concave diffraction grating is used to produce a focussed light spectrum on the input face of a detector array 30, that is, the : focussed light is dispersed spectrally over the spatial extent of the acceptance aperture o~ array~30.
25~Referring back to the sample and reference fibers 15 and 16, the output ends of both fibers are placed in closF proximity to each other such that:
~4 ~ 3~22 (1) referring now to Figure 2 for flat, orthogonal end-faces, the axis nR Of the radiation pattern of the reference fiber 16 coincides with the physical axis of 16 and is oriented at an angle ~ with respect to the axis ns of the radiation pattern of the sample fiber 15 (coinciding with the physical axis of 15) such that ~>2~, where ~ is the far-field half angle encompassing the cone of light radiating symmetrically about each fiber axis, or (2) referring now to Figure 3 fox flat, nonorthogonal end-faces, both fiber physical axes are parallel, but each end-face is oriented (via rotation about the fiber physical axis) in the opposite sense, such that each cone of light described by the radiation pattern axes nR and ns radiates on different sides of their common axis. With this arrangement the emerging cone of light 21 from the sample fiber 15 impinges concave diffraction grating 20 over the area from 22 to 23, and the emerging cone of light 24 from reference fiber 16 impinges the grating over the area from 25 to 26. The concave diffraction grating 20 images each fiber end-face spot to a sensor 30 output spot P lfor monochromatic light) and spectrally disperses it across the length of the sensor input lfor polychromatic light). Thus for the monochromatic light shown in Figure 1, the light 21 from the sample -5~ 2 fiber which impinges on grating 20 is diffracted back 27 to point P on the sensor 30 and similarly the light 24 from the reference fiber which impinges on grating 20 i5 diffracted back 28 to point P on the sensor 30.
The total integrated light intensity at any point P at the sensor input plane is given as L(P)=LS(P)~LR(P), where the spectrally dispersed light signal Ls from 11 arrives at an angle 3<0 (referenced to the sensor normal axis nD) and the spectrally dispersed light signal LR from 12 arrives at an angle ~>0 as shown.
The sensor compares the light intensity versus space distribution (i.e., also spectrally dispersed) of L(~>0)=LR to L(a<0)=Ls and outputs a voltage related to their similarityO An example of such a distri.buted sensor which outputs a measure of similarity is the Honeywell Through-the-Camera-Lens (TCL) chip ; (disclosed in such U.S. Patent documents as 4,333,007 6/S2 Langlais et al; 4,254,330 3/81 Stauffer et al; 4,250,376 2/81 Joseph et al; 4,249,073 2/81 Stauffer et al, 4,230,941 10/80 Stauffer, and~
4,185,191 1/80 Stauffer, all assigned to the same assignee as the present invention). In the case of the TCL chip, as disclosed and used in the named .
patents, the measure of similarity is the normal autofocus output signal which indicates the amount of lens movement necesæary to produce a proper focus :
-6- ~3~ 2 condition; no lens movement is requir~d when the similarity condition is established by prior lens movements~ In this present invention the output signal indicating similarity can be used rather for the purpose of color matching. Explicitly, when Ls(~) and LR~) are determined by the sensor to be sufficiently similar~ the sample and reference colors are said to match. Similarly, when Ls(~) and LR(~) are determined by the sensor to be sufficiently dissimilar, the sample and reference colors are said to not match. Since both Ls(~) and LR(~) are characteristic light distributions from illuminated, colored objects, the sensor compares two object colors in real-time. This color comparison is indirect since the object colors per se are not determined in any case; however, this color ~omparison is correct and sufficient, limited primarlly by the physical structure and precision of the sensor.
Referring now to Figure 4, which is an exemplary embodiment of the TCL chip there is shown in more detail the nature of three sensors of the sensor array 30. The light 27 and 28 from the grating 20 falls on the surface 4~0 of the sensor array chlp. On this surface are tiny: microlenses 41, 42 and 43.
Associated with each of the microlenses are two detectors. Each lens projects an image of the ~7~ 2 received light on two of the detector layers 50-55 in which detectors 50, 52 and 54 are identified as R
sensors (that is reference sensors) and in which detectors 51, 53 and 55 are identified as S sensors (that is sample sensors). Each of the R sensors receives light from the 25,26 sector of grating 20 and each of the S sensors receives light Erom the 22,23 sector of the grating. In all there are 24 - microlenses and 24 pairs of detectors in a linear array about 5 millimeters long. Unwanted light is precluded by an aperture mask above the lenslet array.
In Figure 5 is shown a cutaway of the sensor chip previously described showing one pair of detectors, such as 50 and 51, and the shift register circuitry which transfers charge packets from the detectors to output circuitry. A sensor array of this type is also described in greater detail in an article by Norm Stauf~er and Denny Wilwerdin~ enti~led ~Electronic Pocus for Camerasn, Scientific Honeyweller, Volume 3, Number 1, March l9a2, pages 1-13 from which Figure 5 is taken.
Referring now to Figure 6 there is shown an alternative embodiment of Figure 1 that is produced by requiring ~ =0 in Figure 1. In terms of the descriptors of Figure 1, Figure 6 requires that the arer. of impingement from 22 to 23 of the sample core ~ .
-8- ~ 2~
of light 21 is essentially identical to the area of impingement f rom 26 to 25 of the reference core of light 24. In this embodiment, the sample fiber 15 and the reference fiber 16 have flat, orthogonal end-faces that are placed in close proximity in such a way their physical axes are parallel to one another. Since the physical axes of the sample fiber 15 and the reference fiber 16 are not coincident, they appear as distinct disks of light that are imaged by the concave diffraction grating 20 into distinct disks of light on the input face of the sensor. The physical separation of the focussed light signals on the sensor face permits at least two different ways of acquiring the spectrally and spatially dispersed light distr1butions.
Referring now to Figure 7 there is shown in more detail the sensor aperture that can detect the ; physically separated, spectrally and spatially dispersed light distri~utions Ls(x) and LR(x). In Figure 7 apertures 70-75 can be considered for si~plicity to represent detectors as well. The spectrally dispersed light signal LR(x) is an output of A series of detectoes exemplified by 70, 71 and 72 and interconnected by the appropriate circuitry and wiring 80~ Similarly, the spectrally dispersed light signal Ls(x) is an output of another series of .
~ 3 ~
detectors exemplified by 73, 74 and 75 and interconnected by the appropriate circuitry and wiring 81. The physical arrangement to produce orderly imaging and spectral dispersion in the sensor plane of Figure 7 is such that the adjacent detector pairs (70~
73), (71,74) and (72,75) have adjacent, quasimonochromatic light impinging on them, but both elements of every pair experience and detect precisely the same wavelength bands. The signal outputs from 80 and 81 can be processed in real-time in any appropriate manner to obtain a measure of similarity between L~(x~ and Ls(x).
~xample measures of similarity are signature cross-correlation and mean-value difference as disclosed by Sullivan in the co-pending Canadian Application filed on November 8, 1988 and assigned to the presentapplicank.
Alternatively, the exemplary circuitry and wiring 82, 83 and 84 can be configured to obtain a measure o~ similarity between 70 and 73, 71 and 74, and 72 and 75, respectively. A
simple example of similarity between these successive detector pairs is an element-by-element subtraction to obtain a new signal LR S(X) that represents effectively a color signature differenceO
This simultaneous, two-dimensional sensing of spatially dispersed light distributions can be extended to include several reference signals and/or several sample signals for color matching or sorting purposes.
-10~ 2~
The two fibers 15 and 16 have been shown without any auxiliary input or output lenses.
Additional optical lenses may ba optionally used such as positioned between object and fiber to affect collection efficiency, angle of view and the like.
~; :
.
. :
:
, :
;: : :
Referring now to the drawing there is shown generally at 10 a color signature sensor in which it is desired to compare the color of a sample object 11 5with the color of a reference object 12. The objects 11 and 12 are given illumination which is similar.
Color perception depends on the spectral energy density of the illumination source, the spectral reflectance distr1bution of the objec~, and the 10spectral responsivity characteristics of the signal acquisition system. This invention deals only with the signal acquisition system and presupposes suitable illumination of both a reference object and a sample object.
15Collecting the light signals 13 and 14 from ; ob~ects 11 and 12 are two essentially identical optical fibers (a sample fiber 15 and a~ reference :~ fiber 16) which route the light signals to a spectral :dispersive element 20, here shovn in the form of a 20:concave diffraction qrating. The concave diffraction grating is used to produce a focussed light spectrum on the input face of a detector array 30, that is, the : focussed light is dispersed spectrally over the spatial extent of the acceptance aperture o~ array~30.
25~Referring back to the sample and reference fibers 15 and 16, the output ends of both fibers are placed in closF proximity to each other such that:
~4 ~ 3~22 (1) referring now to Figure 2 for flat, orthogonal end-faces, the axis nR Of the radiation pattern of the reference fiber 16 coincides with the physical axis of 16 and is oriented at an angle ~ with respect to the axis ns of the radiation pattern of the sample fiber 15 (coinciding with the physical axis of 15) such that ~>2~, where ~ is the far-field half angle encompassing the cone of light radiating symmetrically about each fiber axis, or (2) referring now to Figure 3 fox flat, nonorthogonal end-faces, both fiber physical axes are parallel, but each end-face is oriented (via rotation about the fiber physical axis) in the opposite sense, such that each cone of light described by the radiation pattern axes nR and ns radiates on different sides of their common axis. With this arrangement the emerging cone of light 21 from the sample fiber 15 impinges concave diffraction grating 20 over the area from 22 to 23, and the emerging cone of light 24 from reference fiber 16 impinges the grating over the area from 25 to 26. The concave diffraction grating 20 images each fiber end-face spot to a sensor 30 output spot P lfor monochromatic light) and spectrally disperses it across the length of the sensor input lfor polychromatic light). Thus for the monochromatic light shown in Figure 1, the light 21 from the sample -5~ 2 fiber which impinges on grating 20 is diffracted back 27 to point P on the sensor 30 and similarly the light 24 from the reference fiber which impinges on grating 20 i5 diffracted back 28 to point P on the sensor 30.
The total integrated light intensity at any point P at the sensor input plane is given as L(P)=LS(P)~LR(P), where the spectrally dispersed light signal Ls from 11 arrives at an angle 3<0 (referenced to the sensor normal axis nD) and the spectrally dispersed light signal LR from 12 arrives at an angle ~>0 as shown.
The sensor compares the light intensity versus space distribution (i.e., also spectrally dispersed) of L(~>0)=LR to L(a<0)=Ls and outputs a voltage related to their similarityO An example of such a distri.buted sensor which outputs a measure of similarity is the Honeywell Through-the-Camera-Lens (TCL) chip ; (disclosed in such U.S. Patent documents as 4,333,007 6/S2 Langlais et al; 4,254,330 3/81 Stauffer et al; 4,250,376 2/81 Joseph et al; 4,249,073 2/81 Stauffer et al, 4,230,941 10/80 Stauffer, and~
4,185,191 1/80 Stauffer, all assigned to the same assignee as the present invention). In the case of the TCL chip, as disclosed and used in the named .
patents, the measure of similarity is the normal autofocus output signal which indicates the amount of lens movement necesæary to produce a proper focus :
-6- ~3~ 2 condition; no lens movement is requir~d when the similarity condition is established by prior lens movements~ In this present invention the output signal indicating similarity can be used rather for the purpose of color matching. Explicitly, when Ls(~) and LR~) are determined by the sensor to be sufficiently similar~ the sample and reference colors are said to match. Similarly, when Ls(~) and LR(~) are determined by the sensor to be sufficiently dissimilar, the sample and reference colors are said to not match. Since both Ls(~) and LR(~) are characteristic light distributions from illuminated, colored objects, the sensor compares two object colors in real-time. This color comparison is indirect since the object colors per se are not determined in any case; however, this color ~omparison is correct and sufficient, limited primarlly by the physical structure and precision of the sensor.
Referring now to Figure 4, which is an exemplary embodiment of the TCL chip there is shown in more detail the nature of three sensors of the sensor array 30. The light 27 and 28 from the grating 20 falls on the surface 4~0 of the sensor array chlp. On this surface are tiny: microlenses 41, 42 and 43.
Associated with each of the microlenses are two detectors. Each lens projects an image of the ~7~ 2 received light on two of the detector layers 50-55 in which detectors 50, 52 and 54 are identified as R
sensors (that is reference sensors) and in which detectors 51, 53 and 55 are identified as S sensors (that is sample sensors). Each of the R sensors receives light from the 25,26 sector of grating 20 and each of the S sensors receives light Erom the 22,23 sector of the grating. In all there are 24 - microlenses and 24 pairs of detectors in a linear array about 5 millimeters long. Unwanted light is precluded by an aperture mask above the lenslet array.
In Figure 5 is shown a cutaway of the sensor chip previously described showing one pair of detectors, such as 50 and 51, and the shift register circuitry which transfers charge packets from the detectors to output circuitry. A sensor array of this type is also described in greater detail in an article by Norm Stauf~er and Denny Wilwerdin~ enti~led ~Electronic Pocus for Camerasn, Scientific Honeyweller, Volume 3, Number 1, March l9a2, pages 1-13 from which Figure 5 is taken.
Referring now to Figure 6 there is shown an alternative embodiment of Figure 1 that is produced by requiring ~ =0 in Figure 1. In terms of the descriptors of Figure 1, Figure 6 requires that the arer. of impingement from 22 to 23 of the sample core ~ .
-8- ~ 2~
of light 21 is essentially identical to the area of impingement f rom 26 to 25 of the reference core of light 24. In this embodiment, the sample fiber 15 and the reference fiber 16 have flat, orthogonal end-faces that are placed in close proximity in such a way their physical axes are parallel to one another. Since the physical axes of the sample fiber 15 and the reference fiber 16 are not coincident, they appear as distinct disks of light that are imaged by the concave diffraction grating 20 into distinct disks of light on the input face of the sensor. The physical separation of the focussed light signals on the sensor face permits at least two different ways of acquiring the spectrally and spatially dispersed light distr1butions.
Referring now to Figure 7 there is shown in more detail the sensor aperture that can detect the ; physically separated, spectrally and spatially dispersed light distri~utions Ls(x) and LR(x). In Figure 7 apertures 70-75 can be considered for si~plicity to represent detectors as well. The spectrally dispersed light signal LR(x) is an output of A series of detectoes exemplified by 70, 71 and 72 and interconnected by the appropriate circuitry and wiring 80~ Similarly, the spectrally dispersed light signal Ls(x) is an output of another series of .
~ 3 ~
detectors exemplified by 73, 74 and 75 and interconnected by the appropriate circuitry and wiring 81. The physical arrangement to produce orderly imaging and spectral dispersion in the sensor plane of Figure 7 is such that the adjacent detector pairs (70~
73), (71,74) and (72,75) have adjacent, quasimonochromatic light impinging on them, but both elements of every pair experience and detect precisely the same wavelength bands. The signal outputs from 80 and 81 can be processed in real-time in any appropriate manner to obtain a measure of similarity between L~(x~ and Ls(x).
~xample measures of similarity are signature cross-correlation and mean-value difference as disclosed by Sullivan in the co-pending Canadian Application filed on November 8, 1988 and assigned to the presentapplicank.
Alternatively, the exemplary circuitry and wiring 82, 83 and 84 can be configured to obtain a measure o~ similarity between 70 and 73, 71 and 74, and 72 and 75, respectively. A
simple example of similarity between these successive detector pairs is an element-by-element subtraction to obtain a new signal LR S(X) that represents effectively a color signature differenceO
This simultaneous, two-dimensional sensing of spatially dispersed light distributions can be extended to include several reference signals and/or several sample signals for color matching or sorting purposes.
-10~ 2~
The two fibers 15 and 16 have been shown without any auxiliary input or output lenses.
Additional optical lenses may ba optionally used such as positioned between object and fiber to affect collection efficiency, angle of view and the like.
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Claims (13)
1. Input mechanism to a color comparator apparatus com-prising:
first optical path means having an input end and an out-put end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an out-put end, said input end being adapted to collect and transmit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors;
spectral dispersive element means for imaging and spec-tral dispersion of the output end color emanations of said first and second optical paths onto said photodetector array;
means positioning said first optical path means output end to direct reference light emanating therefrom to said spec-tral dispersive element means;
means positioning said second optical path means out-put end to direct sample light emanating therefrom to said spec-tral dispersive element means;
the reference diffracted light from said spectral dis-persive element means being directed onto said reference linear array of photodetectors and the sample diffracted light from said spectral dispersive element means being directed onto said sample linear array of photodetectors, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color; and comparator means for simultaneously receiving the plurality of light intensity signals from the reference linear array and from the sample linear array and subtracting said sig-nals to get a difference between reference and sample for direct spectral component comparison.
first optical path means having an input end and an out-put end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an out-put end, said input end being adapted to collect and transmit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors;
spectral dispersive element means for imaging and spec-tral dispersion of the output end color emanations of said first and second optical paths onto said photodetector array;
means positioning said first optical path means output end to direct reference light emanating therefrom to said spec-tral dispersive element means;
means positioning said second optical path means out-put end to direct sample light emanating therefrom to said spec-tral dispersive element means;
the reference diffracted light from said spectral dis-persive element means being directed onto said reference linear array of photodetectors and the sample diffracted light from said spectral dispersive element means being directed onto said sample linear array of photodetectors, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color; and comparator means for simultaneously receiving the plurality of light intensity signals from the reference linear array and from the sample linear array and subtracting said sig-nals to get a difference between reference and sample for direct spectral component comparison.
2. Input mechanism to a color comparator apparatus com-prising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors, said photodetector array also having a plural-ity of linear apertures with one of said reference photodetectors and one of said sample photodetectors of said reference linear array and of said sample linear array behind each aperture;
spectral dispersive element means for imaging and spectral dispersion of the output end color emanations of said first and second optical paths onto said photodetector array;
means positioning said first optical path means output end to direct reference light emanating therefrom to said spectral dispersive element means;
means positioning said second optical path means output end to direct sample light emanating therefrom to said spectral dispersive element means; and the reference diffracted light from said spectral dis-persive element means being directed onto said reference linear array of photodetectors and the sample diffracted light from said spectral dispersive element means being directed onto said sample linear array of photodetectors, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference ob-ject color and the sample object color.
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors, said photodetector array also having a plural-ity of linear apertures with one of said reference photodetectors and one of said sample photodetectors of said reference linear array and of said sample linear array behind each aperture;
spectral dispersive element means for imaging and spectral dispersion of the output end color emanations of said first and second optical paths onto said photodetector array;
means positioning said first optical path means output end to direct reference light emanating therefrom to said spectral dispersive element means;
means positioning said second optical path means output end to direct sample light emanating therefrom to said spectral dispersive element means; and the reference diffracted light from said spectral dis-persive element means being directed onto said reference linear array of photodetectors and the sample diffracted light from said spectral dispersive element means being directed onto said sample linear array of photodetectors, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference ob-ject color and the sample object color.
3. Input mechanism to a color comparator apparatus com-prising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors;
spectral dispersive element means for imaging and spectral dispersion of the output end color emanations of said first and second optical paths onto said photodetector array, said spectral dispersive element means being in the form of a single concave diffraction grating which has a reference area and a sample area separated from one another on the concave diffrac-tion grating;
means positioning said first optical path means output end to direct reference light emanating therefrom to said grating reference area;
means positioning said second optical path means out-put end to direct sample light emanating therefrom to said grating sample area; and the reference diffracted light from said grating refer-ence area being directed onto said reference linear array of photodetectors from a first solid angle and the sample diffracted light from said grating sample area being directed onto said sample linear array of photodetectors from a different solid angle, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color.
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a sample object to said output end;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of photodetectors;
spectral dispersive element means for imaging and spectral dispersion of the output end color emanations of said first and second optical paths onto said photodetector array, said spectral dispersive element means being in the form of a single concave diffraction grating which has a reference area and a sample area separated from one another on the concave diffrac-tion grating;
means positioning said first optical path means output end to direct reference light emanating therefrom to said grating reference area;
means positioning said second optical path means out-put end to direct sample light emanating therefrom to said grating sample area; and the reference diffracted light from said grating refer-ence area being directed onto said reference linear array of photodetectors from a first solid angle and the sample diffracted light from said grating sample area being directed onto said sample linear array of photodetectors from a different solid angle, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color.
4. The apparatus according to claim 1 in which said first and second optical path means comprise first and second optical fibers respectively.
5. Input mechanism to a color comparator apparatus com-prising:
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a sample object to said output end;
spectral dispersive element means in the form of a single concave diffraction grating, said grating including a reference area and a sample area which are spatially separated one from the other on said concave diffraction grating;
means positioning said first optical path means output end to direct reference light emanating therefrom to the reference area on said concave diffraction grating;
means positioning said second optical path means output end to direct sample light emanating therefrom to the sample area on said concave diffraction grating;
a photodetector array, said photodetector array having a reference linear array of photodetectors and adjacent thereto a sample linear array of photodetectors;
means directing diffracted light from said reference area onto said reference linear array of photodetectors from a first solid angle and directing diffracted light from said sample area onto said sample linear array of photodetectors from a different solid angle, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color.
first optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a reference object to said output end;
second optical path means having an input end and an output end, said input end being adapted to collect and transmit the color of a sample object to said output end;
spectral dispersive element means in the form of a single concave diffraction grating, said grating including a reference area and a sample area which are spatially separated one from the other on said concave diffraction grating;
means positioning said first optical path means output end to direct reference light emanating therefrom to the reference area on said concave diffraction grating;
means positioning said second optical path means output end to direct sample light emanating therefrom to the sample area on said concave diffraction grating;
a photodetector array, said photodetector array having a reference linear array of photodetectors and adjacent thereto a sample linear array of photodetectors;
means directing diffracted light from said reference area onto said reference linear array of photodetectors from a first solid angle and directing diffracted light from said sample area onto said sample linear array of photodetectors from a different solid angle, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color.
6. The apparatus according to claim 5 and further compri-sing comparator means for simultaneously receiving the plurality of light intensity signals from the reference linear array and from the sample linear array and subtracting said signals for direct spectral component comparison.
7. The apparatus according to claim 5 in which said first and second optical path means comprise first and second optical fibers respectively.
8. The apparatus according to claim 5 in which said means directing diffracted light from said reference area onto said reference linear array and directing diffracted light from said sample area onto said sample linear array comprises a plurality of linear apertures with one of said reference photodetectors and one of said sample photodetectors of said reference linear array and of said sample linear array behind each aperture.
9. The apparatus according to claim 8 and further compri-sing comparator means for simultaneously receiving the plurality of light intensity signals from the reference linear array and from the sample linear array and subtracting said signals for direct spectral component comparison
10. The apparatus according to claim 5 in which said means positioning comprise the output ends of said first and second optical path means being placed in close proximity to each other and oriented such that the axis nR of the light cone emanating from the first optical path means is oriented at an angle with respect to the axis nS of the light cone emanating from the second optical path means such that ??>2.PHI., where .PHI. is the far-field half-angle emcompassing the cone of light diffracting about each axis nR and nS.
11. Real-time color comparator apparatus comprising:
a reference optical fiber having an input end and an output end, said input end being adapted to observe and transmit the color of a reference object;
a sample optical fiber having an input end and an out-put end, said input end being adapted to observe and transmit the color of a sample object;
a single concave diffraction grating;
means positioning said reference fiber output end to direct light emanating from the output end of said reference op-tical fiber to a first reference area on said concave diffractive grating;
means positioning said sample fiber output end to al-rect sample light emanating therefrom to a second sample area on said concave diffraction grating, the second sample area being spatially separated from said first reference area on said con-cave grating;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of phototdetectors;
means focussing diffracted light from said first reference area onto said reference linear array of photodetectors and focussing diffracted light from said second sample area onto said sample linear array of photodetectors, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color.
a reference optical fiber having an input end and an output end, said input end being adapted to observe and transmit the color of a reference object;
a sample optical fiber having an input end and an out-put end, said input end being adapted to observe and transmit the color of a sample object;
a single concave diffraction grating;
means positioning said reference fiber output end to direct light emanating from the output end of said reference op-tical fiber to a first reference area on said concave diffractive grating;
means positioning said sample fiber output end to al-rect sample light emanating therefrom to a second sample area on said concave diffraction grating, the second sample area being spatially separated from said first reference area on said con-cave grating;
a photodetector array, said photodetector array having a reference linear array of photodetectors and a sample linear array of phototdetectors;
means focussing diffracted light from said first reference area onto said reference linear array of photodetectors and focussing diffracted light from said second sample area onto said sample linear array of photodetectors, said reference array and sample array of photodetectors producing a plurality of light intensity signals representative of the spectral distribution of the reference object color and the sample object color.
12. The apparatus according to claim 11 and further compri-sing comparator means for simultaneously receiving the plurality of light intensity signals from the reference linear array and from the sample linear array and subtracting said signals to get a difference between reference and sample for direct spectral component comparison.
13. The apparatus according to claim 11 in which said photodetector array has a plurality of linear apertures with one reference photodetector and one sample photodetector of said reference linear array and of said sample linear array behind each aperture.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/118,587 | 1987-11-09 | ||
| US07/118,587 US4841140A (en) | 1987-11-09 | 1987-11-09 | Real-time color comparator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1316022C true CA1316022C (en) | 1993-04-13 |
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ID=22379529
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000582489A Expired - Fee Related CA1316022C (en) | 1987-11-09 | 1988-11-08 | Real-time color comparator |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4841140A (en) |
| EP (1) | EP0315938A3 (en) |
| CA (1) | CA1316022C (en) |
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| US2046958A (en) * | 1935-03-21 | 1936-07-07 | Gen Electric | Colorimeter |
| US3690771A (en) * | 1970-04-07 | 1972-09-12 | Du Pont | Method and apparatus for instrumentally shading metallic paints |
| DE2141364C3 (en) * | 1971-08-18 | 1981-02-19 | Sulzer Morat Gmbh, 7024 Filderstadt | Method and device for recognizing the color of an original |
| GB1521585A (en) * | 1975-09-09 | 1978-08-16 | Perkin Elmer Corp | Spectrophotometers |
| JPS5933204B2 (en) * | 1976-01-30 | 1984-08-14 | 株式会社日立製作所 | Two-beam spectrophotometer |
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| DE2918384C2 (en) * | 1979-05-08 | 1984-03-22 | Krautkrämer GmbH, 5000 Köln | Method for the optical reception of ultrasonic waves |
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| DE3526553A1 (en) * | 1985-07-25 | 1987-01-29 | Zeiss Carl Fa | REMISSION MEASURING DEVICE FOR CONTACTLESS MEASUREMENT |
| US4718764A (en) * | 1986-01-27 | 1988-01-12 | Hughes Aircraft Company | Frequency agile spectrometer |
| JPS63145926A (en) * | 1986-12-10 | 1988-06-18 | Hoya Corp | Color sensor |
-
1987
- 1987-11-09 US US07/118,587 patent/US4841140A/en not_active Expired - Lifetime
-
1988
- 1988-11-08 EP EP88118544A patent/EP0315938A3/en not_active Withdrawn
- 1988-11-08 CA CA000582489A patent/CA1316022C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0315938A3 (en) | 1990-08-22 |
| US4841140A (en) | 1989-06-20 |
| EP0315938A2 (en) | 1989-05-17 |
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