CA2348383A1 - Method and device for the colorimetric measurement of a coloured surface - Google Patents
Method and device for the colorimetric measurement of a coloured surface Download PDFInfo
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- CA2348383A1 CA2348383A1 CA002348383A CA2348383A CA2348383A1 CA 2348383 A1 CA2348383 A1 CA 2348383A1 CA 002348383 A CA002348383 A CA 002348383A CA 2348383 A CA2348383 A CA 2348383A CA 2348383 A1 CA2348383 A1 CA 2348383A1
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- 238000005259 measurement Methods 0.000 title claims abstract description 46
- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000012545 processing Methods 0.000 claims description 10
- 230000002093 peripheral effect Effects 0.000 claims description 5
- 230000003595 spectral effect Effects 0.000 claims description 2
- 239000011159 matrix material Substances 0.000 description 5
- 238000012546 transfer Methods 0.000 description 4
- 239000000758 substrate Substances 0.000 description 3
- 239000003086 colorant Substances 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000004737 colorimetric analysis Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000003702 image correction Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
- 230000000007 visual effect Effects 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
- G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
-
- 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
- G01J3/52—Measurement of colour; Colour measuring devices, e.g. colorimeters using colour charts
- G01J3/524—Calibration of colorimeters
-
- 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
- G01J3/0272—Handheld
Abstract
The present invention relates to a method for the colorimetric measurement of a defined region on an image representing a surface, characterized in that the said image of the said surface is taken using a colour camera, in that the analogue information measured on the said surface is transformed and converted into digital form, in that the said defined region on the said image is delimited and in that the measurement of the chromatic values R, G, B is carried out for this region.
Description
METHOD AND DEVICE FOR THE COLORIMETRIC MEASUREMENT OF A
COLOURED SURFACE
Subject of the invention The present invention relates first of all to a process which allows the colorimetric and possibly dimensional measurement of a coloured surface and to the processing of the information measured on the said surface or on part of the latter.
The present invention also relates to the device for the colorimetric measurement of the said surface .
D r , i.. w. T ~ i-Many colorimetric measurement-taking devices are known which make it possible to give, by tristimulus measurement, values of the three chromatic parameters, R_ (red), G (green) and B (blue), of a colorimetric measurement. For this purpose, an illuminant is used so as to illuminate a surface on which the measurement will be taken. It should be pointed out that this measurement is normally a measurement of the average chromatic values of the illuminated surface.
Patent Application FR-A-2,749,077 has proposed a method and a device for measuring the colour by calculating the trichromatic components with respect to a colorimetric reference system. This calculation is made using a matrix for transferring the colorimetric system associated with the data acquisition system to the colorimetric reference system. The said transfer matrix is calculated by an iterative procedure based on the trichromatic components measured by the colorimetric reference system of the three primary colours. However, it is found that the measurements are taken using a tri-CCD camera having three CCD ' sensors - one CCD sensor for each of the three trichromatic components. The cost of this camera is relatively high. Furthermore, it is found that the illuminant is placed outside the acquisition system including the camera. This means that perturbations due to the surrounding (ambient) illumination will be picked up during measurement by the acquisition system.
Furthermore, it is found that no dimensional or spatial processing of the image is possible with the system described in this publication.
Document US-A-5,724,259 describes a method for monitoring the colour of a printed image an a substrate, which makes it possible, using a camera, to measure the light reflected from the said printed image onto the substrate, to transform this measurement into a signal sent to a computer and to use the information emanating from this signal to correct the effects of scattered light reflected from the printed image. The main use of this method is therefore to check the ink thickness in the case of applications of printing machines such as printers. For this purpose, the optical density defined by the logarithm to the base 10 of the reflectance, this being a percentage of the scattering of the incident light, is more specifically measured. For this purpose, a reference surface not incorporated into the apparatus is placed beside the printed image to be measured. This also means that the measurement is not a contact measurement but indeed a remote measurement.
Document EP-A-0,491,131 describes an apparatus for monitoring and calibrating the spectrum emitted by a coloured object using the dispersion of the wavelength provided by a variable filter. This is a calibrating apparatus working directly as a colorimeter. However, in the present case, because of the presence of a diffuser and a variable filter between the one-dimensional sensor and the object itself, it is estimated that no spatial information could be obtained by the use of such a device.
Document EP-A-0,314,312 describes a method and an apparatus making it possible to detect the presence of ink on a substrate using several light-emitting diodes (LEDs} of different wavelengths which are switched on and off independently of each other.
Document US-A-3,597,094 describes a portable device allowing colour identification, which works directly with visual observation. This device comprises a plurality of filters positioned between a light source and the coloured surface.
Objects of the Invention One object of the present invention is to propose an improved method and an improved device which make it possible to obtain a colorimetric and dimensional (or spatial) measurement of a defined region on an image of a surface, which is possibly inhomogeneous, such as dot-matrix printing or a defect appearing on a captured surf ace.
This will allow a reproducible and reliable measurement of the chromatic parameters of the said defined region to be obtained.
The object of the present invention is also to propose a device and a method which make it possible to take stabilized measurements with respect to a reference standard.
The obj ect of the present invention is also to allow the use of this information for medical, industrial, cosmetic and food applications or else in any other application using the technique of colorimetry.
Main characteristic elements of the invention The present invention relates first of all to a method for the colorimetric and possibly dimensional measurement of a defined region on an image representing a surface. The method consists in taking an image of the said surface using a colour camera, in ~ .
transforming and converting the analogue information measured on the said surface into digital form, preferably using a processing unit on. board of the colour camera or in a computer, in delimiting the said defined region on the said image and in carrying out the measurement of the chromatic values R, G, B for this region.
The term "surface" should be understood to mean the surface for which it is desired to obtain colorimetric-type and/or dimensional-type information.
The term "image" should be understood to mean a group of pixels which represents the captured surface and which may be directly transmitted to a monitor such as a screen or a printer.
The term "region" should be understood to mean that part of the said image for which the colorimetric and/or dimensional measurement is carried out.
Optionally, the method also consists in measuring the distance between two pixels of the said image or in delimiting the included area during peripheral tracing of a region of the said image.
The definition of the said region may be carried out either manually by peripheral tracing, or automatically by scanning the various pixels of the image for which the chromatic parameters fall within a predetermined window or interval.
The present invention also relates to the device for implementing the said method, comprising a sensor provided with a colour camera and with an illuminant which are placed within the same enclosure associated with an analogue information acquisition system, the information being measured using the said sensor and being converted into digital form by a processing unit.
Preferably, the colour camera is a mono-CCD or mono-CMOS camera.
Preferably, the illuminant will be produced using a single, white or colour, diode or several 5 identical, white or colour, diodes having the same spectral distribution.
According to a preferred embodiment, the sensor furthermore includes, within the same enclosure of the sensor, a reference standard placed in the field of view of the said camera. This makes it possible to stabilize each measurement.
According to a preferred embodiment, the information converted by the processing unit is transmitted to a monitor which may be a screen or a printer and which gives a precise display of the image.
Optionally, using this monitor, the image may also be processed so as to measure the distance between two specific points or pixels, to measure the area of the said region, etc.
The data will be obtained by a tristimulus measurement of the R, G, B parameters, preferably by matrix computation.
Brief description of the figures Figure 1 shows an overall schematic view of the information -acquisition system according to the invention.
Figure 2 shows an exploded view of the measurement sensor used in the acquisition system shown in Figure 1.
Figure 3 shows the flow chart for the processing method for the measurement carried out on the image to be analyzed.
Detailed description of one embodiment of the present invention Figure z shows an overall schematic view of the acquisition system of analogue information relating to the measured chromatic values. The analogue information will be converted into digital form by the electronics.
This acquisition system firstly comprises a sensor 100 which will be described in greater detail below and a processing unit 200 which processes the information captured by the camera and transmits them to a monitor 300. The processing unit is composed of a camera card 210 and a CPU card 220. The information is transmitted . between the two cards digitally. The measurement head or sensor 100 is linked by a low-voltage flex to the camera card. This sensor essentially comprises, held within a single enclosure, a colour camera 150, preferably a mono-CCD or mono-CMOS camera, and an illuminant 120 which may consist of light-emitting diodes, these being, for example, white or other 15- colours. The fact of integrating the illuminant into the actual measurement head makes it possible to get round the problem of environmental perturbations, given that the camera will be sensitive only to the image illuminated by the illuminant and not to the external (ambient) environment.
Figure 2 shows this sensor in greater detail.
Conventionally, it comprises an optional window 1 which may also protect the camera and the source from the external environment. The sensor will be placed directly on the surface of the specimen to be analyzed.
Provision is -made for the latter to be at the object distance from the objective, thus allowing a sharp image to be transmitted to the screen. The illuminant preferably consists of diodes geometrically integrated into the sensor in order to generate, possibly using a diffuser 6, light which is perfectly homogeneous over the entire surface to be measured. Homogenization of the illuminant may furthermore be achieved using an integrating sphere. The stability of the illuminant is guaranteed by controlling the current through the diodes. The optical barrel 3 of the camera is provided with a combination of lenses as well as with a diaphragm of well-defined dimensions, which allow the resolution of the sensor of the CCD colour camera 5 to be fully exploited.
Particularly advantageously, provision is also made to place, possibly in the internal field of view of the camera, such as for example on the internal or external face of the window, a well-defined colour reference standard so that the values measured while taking a measurement can always be measured with reference to the reference standard 7 during each measurement_..Thus, the data obtained, including for the reference standard, will make it possible, at each measurement taken, to stabilize, that is to say to determine and evaluate, Vany drift in the sensor assembly and to take this into account during processing of the information and of the measured chromatic values.
The measurement is based on the tristimulus (R, G, B) method already mentioned above, the stability of which is ensured by the use of a stable reference surface. The interpretation of the measurements is performed, as required, in the various chromatic co-ordinate systems (xyY, Lab, etc.), depending on the choice of the user. The calculation of the co-ordinates is mainly performed by matrix calculation based on the RGB chromatic values measured by the sensor. Absolute or relative .measurements may be obtained, for example by measuring the deviation from one colour with respect to another. The precision of the measurement will depend on the number of pixels selected (and therefore on the number of bits per pixel) for the measurement, possibly allowing interpretation of the image obtained on the screen of the monitor.
Particularly advantageously, not only the average chromatic value measured for a group of pixels but also the entire image may thus be transmitted, which may be stored, compared or transmitted to the outside. This technique furthermore allows very precise positioning of the sensor as well as repeated repositioning. It is found that the measurement time is of the order of one second and that the chromatic values are displayed almost instantaneously on a display and possibly simultaneously on the monitor interpreting the image.
Figure 3 shows the flow chart for the measurement. A surface Sm to be measured, illuminated by a source S, gives an image I exploitable by the sensor.
The colour camera possesses three types of pixels, representative of red, green and blue. The analogue information per pixel Ra(i, j), Ga(i, j), Bali, j) (for all the pixels) will be converted into digital form by the electronics E into Rn(i, j), Gn(i, j), Bn(i, j) (for all the pixels). In order to correct the imperfection in the homogeneity of the sensor and of the illuminant, an image correction function Fc gives, from Rn(i, j), Gn(i, j), Bn(i, j) (for all the pixels), corrected values Rc(i, j), Gc(i, j), Bc(i, j) (for all the pixels). This correc-tion function per pixel is established by placing the sensor on homogeneous surfaces. These corrected values are then transferred by a video transfer function Fv in order to be able to display the image of Rv (i, j), Gv(i, j), Bv(i, j) (for all the pixels) which is closest to reality, possibly taking into account the response of the monitor.
From the corrected values Rc(i, j), Gc(i, j), Bc(i, j) (for all the pixels), a reference region Rr (i, j), Gr(i, j), Br(i, j) (composed of a group of pixels Npr) is imposed and another measurement reg ion Rm(i, j), Gm(i, j), Bm(i, j) (composed of a group of pixels Np) is chosen using a selection function Fs el.
The number of pixels Np may be obtained from Rm(i, j), Gm(i, j), Bm(i, j) and from a dimensional measurem ent function Fd, making it possible to obtain distance or area metrology M. These measurements may be displa yed on the monitor.' Being in possession of the reference Rr(i, j), Gr(i, j), Br(i, j) (for a group of pixels Npr), it is possible, using an integration function Fi, to find the values Rr, Gr, Br. The measurement of Rm(i, j), Gm(i, j ) , Bm(i, j ) for a number of pixels Np gives Rm, Gm, Bm by integration.
With Rr, Gr, Br and Rm, Gm, Bm, it is possible to use a stabilization function Fstab (which eliminates the influence of the sensor on the temperature, etc.), giving R, G, B specif is to the system.
In order to be able to give the chromatic values in a CIE reference system XYZ, a transfer function Ft is used, which gives XYZ from RGB. This XYZ
system is not the only reference system. Consequently, by means of a colorimetric function Fchr, is possible to obtain and display the measured colour CM in xyY, Lab, LCH, etc.
Several peripheral devices can be used to transfer this data, such as a connection to another computer, to a printer, to a network, etc.
COLOURED SURFACE
Subject of the invention The present invention relates first of all to a process which allows the colorimetric and possibly dimensional measurement of a coloured surface and to the processing of the information measured on the said surface or on part of the latter.
The present invention also relates to the device for the colorimetric measurement of the said surface .
D r , i.. w. T ~ i-Many colorimetric measurement-taking devices are known which make it possible to give, by tristimulus measurement, values of the three chromatic parameters, R_ (red), G (green) and B (blue), of a colorimetric measurement. For this purpose, an illuminant is used so as to illuminate a surface on which the measurement will be taken. It should be pointed out that this measurement is normally a measurement of the average chromatic values of the illuminated surface.
Patent Application FR-A-2,749,077 has proposed a method and a device for measuring the colour by calculating the trichromatic components with respect to a colorimetric reference system. This calculation is made using a matrix for transferring the colorimetric system associated with the data acquisition system to the colorimetric reference system. The said transfer matrix is calculated by an iterative procedure based on the trichromatic components measured by the colorimetric reference system of the three primary colours. However, it is found that the measurements are taken using a tri-CCD camera having three CCD ' sensors - one CCD sensor for each of the three trichromatic components. The cost of this camera is relatively high. Furthermore, it is found that the illuminant is placed outside the acquisition system including the camera. This means that perturbations due to the surrounding (ambient) illumination will be picked up during measurement by the acquisition system.
Furthermore, it is found that no dimensional or spatial processing of the image is possible with the system described in this publication.
Document US-A-5,724,259 describes a method for monitoring the colour of a printed image an a substrate, which makes it possible, using a camera, to measure the light reflected from the said printed image onto the substrate, to transform this measurement into a signal sent to a computer and to use the information emanating from this signal to correct the effects of scattered light reflected from the printed image. The main use of this method is therefore to check the ink thickness in the case of applications of printing machines such as printers. For this purpose, the optical density defined by the logarithm to the base 10 of the reflectance, this being a percentage of the scattering of the incident light, is more specifically measured. For this purpose, a reference surface not incorporated into the apparatus is placed beside the printed image to be measured. This also means that the measurement is not a contact measurement but indeed a remote measurement.
Document EP-A-0,491,131 describes an apparatus for monitoring and calibrating the spectrum emitted by a coloured object using the dispersion of the wavelength provided by a variable filter. This is a calibrating apparatus working directly as a colorimeter. However, in the present case, because of the presence of a diffuser and a variable filter between the one-dimensional sensor and the object itself, it is estimated that no spatial information could be obtained by the use of such a device.
Document EP-A-0,314,312 describes a method and an apparatus making it possible to detect the presence of ink on a substrate using several light-emitting diodes (LEDs} of different wavelengths which are switched on and off independently of each other.
Document US-A-3,597,094 describes a portable device allowing colour identification, which works directly with visual observation. This device comprises a plurality of filters positioned between a light source and the coloured surface.
Objects of the Invention One object of the present invention is to propose an improved method and an improved device which make it possible to obtain a colorimetric and dimensional (or spatial) measurement of a defined region on an image of a surface, which is possibly inhomogeneous, such as dot-matrix printing or a defect appearing on a captured surf ace.
This will allow a reproducible and reliable measurement of the chromatic parameters of the said defined region to be obtained.
The object of the present invention is also to propose a device and a method which make it possible to take stabilized measurements with respect to a reference standard.
The obj ect of the present invention is also to allow the use of this information for medical, industrial, cosmetic and food applications or else in any other application using the technique of colorimetry.
Main characteristic elements of the invention The present invention relates first of all to a method for the colorimetric and possibly dimensional measurement of a defined region on an image representing a surface. The method consists in taking an image of the said surface using a colour camera, in ~ .
transforming and converting the analogue information measured on the said surface into digital form, preferably using a processing unit on. board of the colour camera or in a computer, in delimiting the said defined region on the said image and in carrying out the measurement of the chromatic values R, G, B for this region.
The term "surface" should be understood to mean the surface for which it is desired to obtain colorimetric-type and/or dimensional-type information.
The term "image" should be understood to mean a group of pixels which represents the captured surface and which may be directly transmitted to a monitor such as a screen or a printer.
The term "region" should be understood to mean that part of the said image for which the colorimetric and/or dimensional measurement is carried out.
Optionally, the method also consists in measuring the distance between two pixels of the said image or in delimiting the included area during peripheral tracing of a region of the said image.
The definition of the said region may be carried out either manually by peripheral tracing, or automatically by scanning the various pixels of the image for which the chromatic parameters fall within a predetermined window or interval.
The present invention also relates to the device for implementing the said method, comprising a sensor provided with a colour camera and with an illuminant which are placed within the same enclosure associated with an analogue information acquisition system, the information being measured using the said sensor and being converted into digital form by a processing unit.
Preferably, the colour camera is a mono-CCD or mono-CMOS camera.
Preferably, the illuminant will be produced using a single, white or colour, diode or several 5 identical, white or colour, diodes having the same spectral distribution.
According to a preferred embodiment, the sensor furthermore includes, within the same enclosure of the sensor, a reference standard placed in the field of view of the said camera. This makes it possible to stabilize each measurement.
According to a preferred embodiment, the information converted by the processing unit is transmitted to a monitor which may be a screen or a printer and which gives a precise display of the image.
Optionally, using this monitor, the image may also be processed so as to measure the distance between two specific points or pixels, to measure the area of the said region, etc.
The data will be obtained by a tristimulus measurement of the R, G, B parameters, preferably by matrix computation.
Brief description of the figures Figure 1 shows an overall schematic view of the information -acquisition system according to the invention.
Figure 2 shows an exploded view of the measurement sensor used in the acquisition system shown in Figure 1.
Figure 3 shows the flow chart for the processing method for the measurement carried out on the image to be analyzed.
Detailed description of one embodiment of the present invention Figure z shows an overall schematic view of the acquisition system of analogue information relating to the measured chromatic values. The analogue information will be converted into digital form by the electronics.
This acquisition system firstly comprises a sensor 100 which will be described in greater detail below and a processing unit 200 which processes the information captured by the camera and transmits them to a monitor 300. The processing unit is composed of a camera card 210 and a CPU card 220. The information is transmitted . between the two cards digitally. The measurement head or sensor 100 is linked by a low-voltage flex to the camera card. This sensor essentially comprises, held within a single enclosure, a colour camera 150, preferably a mono-CCD or mono-CMOS camera, and an illuminant 120 which may consist of light-emitting diodes, these being, for example, white or other 15- colours. The fact of integrating the illuminant into the actual measurement head makes it possible to get round the problem of environmental perturbations, given that the camera will be sensitive only to the image illuminated by the illuminant and not to the external (ambient) environment.
Figure 2 shows this sensor in greater detail.
Conventionally, it comprises an optional window 1 which may also protect the camera and the source from the external environment. The sensor will be placed directly on the surface of the specimen to be analyzed.
Provision is -made for the latter to be at the object distance from the objective, thus allowing a sharp image to be transmitted to the screen. The illuminant preferably consists of diodes geometrically integrated into the sensor in order to generate, possibly using a diffuser 6, light which is perfectly homogeneous over the entire surface to be measured. Homogenization of the illuminant may furthermore be achieved using an integrating sphere. The stability of the illuminant is guaranteed by controlling the current through the diodes. The optical barrel 3 of the camera is provided with a combination of lenses as well as with a diaphragm of well-defined dimensions, which allow the resolution of the sensor of the CCD colour camera 5 to be fully exploited.
Particularly advantageously, provision is also made to place, possibly in the internal field of view of the camera, such as for example on the internal or external face of the window, a well-defined colour reference standard so that the values measured while taking a measurement can always be measured with reference to the reference standard 7 during each measurement_..Thus, the data obtained, including for the reference standard, will make it possible, at each measurement taken, to stabilize, that is to say to determine and evaluate, Vany drift in the sensor assembly and to take this into account during processing of the information and of the measured chromatic values.
The measurement is based on the tristimulus (R, G, B) method already mentioned above, the stability of which is ensured by the use of a stable reference surface. The interpretation of the measurements is performed, as required, in the various chromatic co-ordinate systems (xyY, Lab, etc.), depending on the choice of the user. The calculation of the co-ordinates is mainly performed by matrix calculation based on the RGB chromatic values measured by the sensor. Absolute or relative .measurements may be obtained, for example by measuring the deviation from one colour with respect to another. The precision of the measurement will depend on the number of pixels selected (and therefore on the number of bits per pixel) for the measurement, possibly allowing interpretation of the image obtained on the screen of the monitor.
Particularly advantageously, not only the average chromatic value measured for a group of pixels but also the entire image may thus be transmitted, which may be stored, compared or transmitted to the outside. This technique furthermore allows very precise positioning of the sensor as well as repeated repositioning. It is found that the measurement time is of the order of one second and that the chromatic values are displayed almost instantaneously on a display and possibly simultaneously on the monitor interpreting the image.
Figure 3 shows the flow chart for the measurement. A surface Sm to be measured, illuminated by a source S, gives an image I exploitable by the sensor.
The colour camera possesses three types of pixels, representative of red, green and blue. The analogue information per pixel Ra(i, j), Ga(i, j), Bali, j) (for all the pixels) will be converted into digital form by the electronics E into Rn(i, j), Gn(i, j), Bn(i, j) (for all the pixels). In order to correct the imperfection in the homogeneity of the sensor and of the illuminant, an image correction function Fc gives, from Rn(i, j), Gn(i, j), Bn(i, j) (for all the pixels), corrected values Rc(i, j), Gc(i, j), Bc(i, j) (for all the pixels). This correc-tion function per pixel is established by placing the sensor on homogeneous surfaces. These corrected values are then transferred by a video transfer function Fv in order to be able to display the image of Rv (i, j), Gv(i, j), Bv(i, j) (for all the pixels) which is closest to reality, possibly taking into account the response of the monitor.
From the corrected values Rc(i, j), Gc(i, j), Bc(i, j) (for all the pixels), a reference region Rr (i, j), Gr(i, j), Br(i, j) (composed of a group of pixels Npr) is imposed and another measurement reg ion Rm(i, j), Gm(i, j), Bm(i, j) (composed of a group of pixels Np) is chosen using a selection function Fs el.
The number of pixels Np may be obtained from Rm(i, j), Gm(i, j), Bm(i, j) and from a dimensional measurem ent function Fd, making it possible to obtain distance or area metrology M. These measurements may be displa yed on the monitor.' Being in possession of the reference Rr(i, j), Gr(i, j), Br(i, j) (for a group of pixels Npr), it is possible, using an integration function Fi, to find the values Rr, Gr, Br. The measurement of Rm(i, j), Gm(i, j ) , Bm(i, j ) for a number of pixels Np gives Rm, Gm, Bm by integration.
With Rr, Gr, Br and Rm, Gm, Bm, it is possible to use a stabilization function Fstab (which eliminates the influence of the sensor on the temperature, etc.), giving R, G, B specif is to the system.
In order to be able to give the chromatic values in a CIE reference system XYZ, a transfer function Ft is used, which gives XYZ from RGB. This XYZ
system is not the only reference system. Consequently, by means of a colorimetric function Fchr, is possible to obtain and display the measured colour CM in xyY, Lab, LCH, etc.
Several peripheral devices can be used to transfer this data, such as a connection to another computer, to a printer, to a network, etc.
Claims (9)
1. Method for the colorimetric measurement of a defined region on an image representing a surface, said image of the said surface being taken using a colour camera, the analogue information measured on the said surface being transformed and converted into digital form, characterized in that a colorimetric measurement of a reference, said reference not being on said surface, is made during each measurement of said image.
2. Method according to Claim 1, characterized in that a dimensional measurement of the defined region is carried out.
3. Method according to Claim 1, characterized in that the region is defined during manual selection by peripheral tracing.
4. Method according to Claim 1 or 2, characterized in that the region to be measured is selected automatically by scanning the pixels which have chromatic values lying within a predetermined interval.
5. Device for implementing the method according to any one of the preceding claims, comprising a sensor (100), consisting of a box (or enclosure) which contains a camera (150) and an illuminant (120), an analogue information acquisition system and a reference (7) of a defined colour, placed in the field of view of the camera (5), the information being measured using the sensor (100) and being converted into digital form by a processing unit (200), the said processing unit also making it possible for the defined region, the chromatic parameters of which it is desired to know, to be precisely delimited.
6. Device according to Claim 5, characterized, in that the camera (150) is a CCD colour camera or a GMOS
colour camera.
colour camera.
7. Device according to Claim 5 or 6, characterized in that the illuminant (120) is produced using a single, white or colour, light-emitting diode or using several identical, white or colour, light-emitting diodes having the same spectral distribution.
8. Device according to Claim 5, characterized in that said reference (7) is placed on a window (1) which allows the internal part of the sensor (100) to be protected.
9. Device according to any one of Claims 5 to 8, characterized in that the information is transmitted to a peripheral device (300), such as a screen or a printer.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| BE9800814A BE1012272A5 (en) | 1998-11-06 | 1998-11-06 | Device and method for measuring image colored. |
| BE9800814 | 1998-11-06 | ||
| PCT/BE1999/000141 WO2000028289A1 (en) | 1998-11-06 | 1999-11-05 | Method and device for the colorimetric measurement of a coloured surface |
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| CA002348383A Abandoned CA2348383A1 (en) | 1998-11-06 | 1999-11-05 | Method and device for the colorimetric measurement of a coloured surface |
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| EP (1) | EP1127251A1 (en) |
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| BE (1) | BE1012272A5 (en) |
| CA (1) | CA2348383A1 (en) |
| WO (1) | WO2000028289A1 (en) |
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| EP1170576A1 (en) * | 2000-07-07 | 2002-01-09 | Christian Stapfer | Chromatometric spectra and cages, their utilization and how to elaborate them |
| ES2214927B1 (en) * | 2001-11-20 | 2005-12-16 | Universitat Politecnica De Catalunya | DEVICE FOR COLOR MEASUREMENT BASED ON A CONVENTIONAL CCD-RGB CAMERA. |
| ES2208076B1 (en) * | 2002-04-26 | 2005-09-01 | Universitat Politecnica De Catalunya | COMPUTER VISION DEVICE AND PROCEDURES FOR THE MEASUREMENT AND CHARACTERIZATION OF COLOR DISTRIBUTION IN A SAMPLE. |
| JP2004245931A (en) * | 2003-02-12 | 2004-09-02 | Canon Inc | Color image forming apparatus, color measurement control method for the apparatus, and computer readable storage medium and program |
| US20040160595A1 (en) * | 2003-02-14 | 2004-08-19 | Lafarge Road Marking, Inc. | Road marking evaluation and measurement system |
| US20040196461A1 (en) * | 2003-04-04 | 2004-10-07 | Clariant International Ltd. | Process advancement in color management |
| US7262779B1 (en) | 2003-04-10 | 2007-08-28 | Applied Vision Company, Llc | Differential imaging colorimeter |
| JP2007515640A (en) * | 2003-12-19 | 2007-06-14 | データカラー ホールディング アーゲー | Spectrophotometer with digital camera |
| US20050286753A1 (en) * | 2004-06-25 | 2005-12-29 | Triant Technologies Inc. | Automated inspection systems and methods |
| US7351245B2 (en) * | 2004-09-21 | 2008-04-01 | Bernice Joy Rozinsky | Apparatus and method for dislodging object from throat |
| US8605141B2 (en) | 2010-02-24 | 2013-12-10 | Nant Holdings Ip, Llc | Augmented reality panorama supporting visually impaired individuals |
| US9569858B2 (en) | 2014-02-13 | 2017-02-14 | James Bennett Babcock | Cloud-based system for water analysis |
| CN104764697B (en) * | 2015-04-16 | 2017-12-19 | 浙江工商大学 | A kind of method for judging peeled shrimp vacuum freeze drying degree |
| CN106257269B (en) * | 2016-02-26 | 2019-04-02 | 深圳市华盛昌科技实业股份有限公司 | A kind of liquid detecting method and device |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3597094A (en) * | 1967-08-11 | 1971-08-03 | David G Goldwasser | Portable color identification device |
| IT1172646B (en) | 1983-09-21 | 1987-06-18 | M S Sistemi Automatici Srl | APPARATUS TO DETECT THE COLORING OF FLAT BODIES IN MOVEMENT AND SUITABLE FOR PROCESSING ELECTRIC SIGNALS THAT VARY ACCORDING TO THE COLOR QUALITY OF THE SAID BODIES APPARATUS PARTICULARLY SUITABLE FOR AUTOMATING THE CHOICE OF CERAMIC TILES AT THE PRODUCTION |
| DE3626373A1 (en) * | 1986-08-05 | 1988-02-18 | Fritz Kurandt | DEVICE FOR QUICK COLOR MEASUREMENT ON DIFFERENT SAMPLES |
| JPS63145926A (en) * | 1986-12-10 | 1988-06-18 | Hoya Corp | Color sensor |
| GB8725034D0 (en) * | 1987-10-26 | 1987-12-02 | De La Rue Syst | Detecting inks |
| DE3830731A1 (en) * | 1988-09-09 | 1990-03-22 | Heidelberger Druckmasch Ag | DEVICE FOR COLOR MEASUREMENT |
| US5272518A (en) * | 1990-12-17 | 1993-12-21 | Hewlett-Packard Company | Colorimeter and calibration system |
| US5159185A (en) | 1991-10-01 | 1992-10-27 | Armstrong World Industries, Inc. | Precise color analysis apparatus using color standard |
| US5724259A (en) * | 1995-05-04 | 1998-03-03 | Quad/Tech, Inc. | System and method for monitoring color in a printing press |
| US5706083A (en) | 1995-12-21 | 1998-01-06 | Shimadzu Corporation | Spectrophotometer and its application to a colorimeter |
| US5911003A (en) | 1996-04-26 | 1999-06-08 | Pressco Technology Inc. | Color pattern evaluation system for randomly oriented articles |
| US5892585A (en) * | 1996-05-05 | 1999-04-06 | Sequel Imaging | Colorimeter for measurement of temporally variant light sources |
| FR2749077B1 (en) * | 1996-05-23 | 1999-08-06 | Oreal | COLOR MEASURING METHOD AND DEVICE |
| US6301004B1 (en) * | 2000-05-31 | 2001-10-09 | Lj Laboratories, L.L.C. | Apparatus and method for measuring optical characteristics of an object |
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1998
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- 1999-11-05 US US09/831,294 patent/US6614530B1/en not_active Expired - Fee Related
- 1999-11-05 AU AU13674/00A patent/AU768141B2/en not_active Ceased
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| JP2002529727A (en) | 2002-09-10 |
| WO2000028289A1 (en) | 2000-05-18 |
| BE1012272A5 (en) | 2000-08-01 |
| AU1367400A (en) | 2000-05-29 |
| US6614530B1 (en) | 2003-09-02 |
| AU768141B2 (en) | 2003-12-04 |
| EP1127251A1 (en) | 2001-08-29 |
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