EP4453522A2 - Procédé et système de colorimétrie - Google Patents

Procédé et système de colorimétrie

Info

Publication number
EP4453522A2
EP4453522A2 EP22843783.6A EP22843783A EP4453522A2 EP 4453522 A2 EP4453522 A2 EP 4453522A2 EP 22843783 A EP22843783 A EP 22843783A EP 4453522 A2 EP4453522 A2 EP 4453522A2
Authority
EP
European Patent Office
Prior art keywords
measuring
measurement
image
color coordinates
spots
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22843783.6A
Other languages
German (de)
English (en)
Inventor
Elisabeth BOTHSCHAFTER
Ferdinand DEGER
Markus Estermann
Reto HÄRING
Christoph Kappel
Jürgen Neumeier
Roland Schanz
Christof Thalhammer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Instrument Systems GmbH
Original Assignee
Instrument Systems GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Instrument Systems GmbH filed Critical Instrument Systems GmbH
Publication of EP4453522A2 publication Critical patent/EP4453522A2/fr
Pending legal-status Critical Current

Links

Classifications

    • 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
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • 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
    • G01J3/506—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors measuring the colour produced by screens, monitors, displays or CRTs
    • 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
    • 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
    • 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
    • G01J3/0229—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
    • 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
    • G01J3/12—Generating the spectrum; Monochromators
    • G01J3/14—Generating the spectrum; Monochromators using refracting elements, e.g. prisms
    • 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
    • G01J3/2823—Imaging spectrometer
    • 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
    • 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
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/251—Colorimeters; Construction thereof
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/90—Determination of colour characteristics
    • 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
    • G01N2201/06—Illumination; Optics
    • 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
    • G01N2201/06—Illumination; Optics
    • G01N2201/063—Illuminating optical parts
    • G01N2201/0634—Diffuse illumination
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10024—Color image
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/20—Special algorithmic details
    • G06T2207/20021—Dividing image into blocks, subimages or windows

Definitions

  • the invention relates to an imaging system that is designed for the two-dimensional, spatially resolved measurement of radiometric and/or photometric measurement variables, in particular the color coordinates of light emitted by a test object.
  • the invention also relates to a method for the two-dimensional, spatially resolved measurement of radiometric and/or photometric measurement variables, in particular the color coordinates of light.
  • the invention lies in the field of imaging color measurement devices, such as those used for quality assurance in the display manufacturing industry.
  • test applications include the color matrix displays of smartphones, tablets, laptops, monitors, TVs, etc. as test objects.
  • imaging colorimeters color measurement devices
  • Powerful imaging colorimeters can measure the color and luminance (brightness) of individual pixels on a screen, as well as the Accurately measure the overall screen uniformity using a color image of the test object captured by an image sensor.
  • the visual performance of a display is checked by automated inspection systems using such imaging colorimeters. This has several advantages. A quantitative evaluation of display defects is possible, a higher test speed can be achieved, and above all a simultaneous evaluation of the overall display quality, i. H. of uniformity and color accuracy.
  • spectrometers or filter colorimeters are used to measure color coordinates (usually in the CIE standard valence system).
  • Filter colorimeters are equipped with optical filters that correspond to the tristimulus values (XYZ coordinates) of the CIE standard valence system and measure chromaticity and luminance by detecting the intensity of light passing through the optical filters.
  • a spectrometer measures the color coordinates by splitting the light from the test object into wavelength components, e.g. B. by means of a prism, a diffraction grating or a spectral filter, and detects the intensity of each primary wavelength element. The measured spectrum is then converted into color coordinates according to the sensitivity curves of the CIE standard valence system.
  • a spectrometer is therefore able to precisely measure the absolute color and luminance.
  • spectrometers tend not to be suitable as imaging test devices.
  • An imaging colorimetry system is known for example from US 5,432,609.
  • an optical filter which only lets through certain wavelengths, is located in front of a monochrome CCD image sensor, which receives the light from the test object.
  • the color coordinates at the different points of the test object are measured with spatial resolution by a simple method based on the same principle as that of a filter colorimeter.
  • a spectrometer is also provided, which receives the light from a predetermined measurement spot on the test object, ie without spatial resolution.
  • the color coordinates are precisely measured at the one measuring spot.
  • the results of the spatially resolved measurement output from the CCD image sensor are finally corrected based on the accurate but not spatially resolved spectral measurement.
  • EP 3 054 273 A1 describes a colorimetric system for testing displays, in which an RGB image sensor is used for spatially resolved measurement of the color coordinates. This enables quick and cost-effective testing in the production of matrix displays.
  • the RGB image sensor assigns a set of RGB color values to each pixel of the color image recorded by the test object.
  • the spectral channels (red, green, blue) of the RGB image sensor are very far from the XYZ color coordinates of the CIE standard valence system (CIE1931 standard), which must be determined in order to make the test object's visual performance consistent with human perception accurate assessment of brightness and color. Therefore, the RGB color values of the pixels of the recorded image are transformed into color coordinates.
  • RGB color values into XYZ color coordinates are not possible because the XYZ color coordinates depend on the spectrum of the measured light in a different way from the sensitivities of the RGB spectral channels, but the spectral information is no longer present in the RGB color image .
  • a (linear) transformation can be found to convert the RGB color values into XYZ color coordinates. Any remaining deviation of the color coordinates obtained in this way is then corrected by again measuring a second part of the emitted light from a measuring spot on the test object, ie without spatial resolution, using a spectrometer parallel to the measurement using the RGB image sensor.
  • the true color coordinates are derived from the spectrum measured for the measurement spot. Finally, on this basis, the color coordinates obtained by transforming the color image of the RGB image sensor are corrected accordingly for each pixel.
  • the resulting image of the corrected XYZ color coordinates is of sufficient accuracy for a number of applications, even if the "true" color coordinates are not measured with spatial resolution. In practice, however, the known approach described above reaches its limits if the spectral properties of the light emission are not homogeneous across the display surface.
  • the object of the invention to provide a system which is improved over the prior art and a corresponding method.
  • the determination of the color coordinates when measuring displays with spatially inhomogeneous spectral emission should be more precise and/or expanded compared to the prior art.
  • the measuring unit of the system includes an imaging spectrometer and each measuring spot/measuring angle is assigned to a different image area of the imaging spectrometer, so that the imaging spectrometer is able to determine the measured variables separately for each measuring spot/measuring angle.
  • two or more measuring units can be provided, with each measuring spot/measuring angle being assigned a measuring unit.
  • the measurement unit or units can be one or more colorimeters.
  • a measurement spot is a limited area on the light-emitting surface of the test object.
  • a measurement angle is an angle in three-dimensional space (specified e.g. by polar angle and azimuth) at which the light is emitted from the surface of the test object, e.g. with respect to a surface normal of the test object or with respect to an optical axis of the system.
  • a transformation is any type of conversion or correction of the image values (i.e. the numerical values that describe the intensity with which the pixels of the image sensor are hit by the first part of the light, such as R, G and B values of a RGB image sensor), such as the conversion of RGB values into color coordinates according to the CIE standard valence system or the correction of color coordinates recorded using an imaging filter wheel colorimeter based on the (precise) measured variables recorded using the measuring unit or units.
  • the image values i.e. the numerical values that describe the intensity with which the pixels of the image sensor are hit by the first part of the light, such as R, G and B values of a RGB image sensor
  • the invention proposes a method according to claim 10 for the two-dimensional, spatially resolved measurement of radiometric and/or photometric measurement variables, in particular the color coordinates of light emitted by a test object.
  • the method uses the imaging system previously identified.
  • the splitting optics can comprise a beam splitter or else a movable mirror.
  • the beam splitter ensures that the first and second parts of the light are recorded simultaneously by the image sensor or by the measuring unit/colorimeter. If a movable mirror is used (eg by a controllable actuator), the light is recorded sequentially or alternately by an image sensor or by a colorimeter. The mirror alternately directs the incident light onto the image sensor (first part) and the colorimeter (second part).
  • the system comprises an imaging spectrometer (e.g.
  • each measuring spot or measuring angle being assigned to a different image area of the imaging spectrometer, so that the spectrometer is able to simultaneously record for each measuring spot or Measuring angle separately to record a spectrum and to determine the measured variables.
  • the imaging spectrometer has an entrance slit, with two or more optical fibers being provided, each of which is assigned to a different measurement spot or measurement angle and the light emitted by the respective measurement spot or at the respective measurement angle to a different position leads to the entrance slit.
  • the imaging spectrometer can include a dispersive optical element, e.g. a grating or a prism, and an additional image sensor.
  • the further image sensor can have a matrix-like configuration with a number of image lines, with the supply of the light from the individual measuring spots/measuring angles to different positions on the entrance slit having the effect that one or more image lines are assigned as an image area to a measuring spot/measuring angle, with the Spectrum, i.e. the wavelength or frequency dimension, is resolved by the dispersive optical element along the image lines.
  • the spectrometer is able to determine a separate spectrum for each measuring spot/measuring angle and (using a computing unit) thus determine the color coordinates.
  • a perforated mask is provided which is arranged in the beam path of the second part of the incident light and defines the measuring spots/measuring angles.
  • the shadow mask is arranged, for example, in a collimated beam of the second part of the incident light, with each of a plurality of holes of the shadow mask corresponding to a measuring spot/measuring angle.
  • the dispersive element causes a spatial separation of the Wavelength components on the image sensor for each measurement spot/angle. That is, by analyzing the output of the image sensor, a spectrum can be recorded for each measuring spot/measuring angle. The color coordinates for each measuring spot/measuring angle can then in turn be derived from this by means of the computing unit.
  • the incident light from the test object is split (by splitting optics), with part of the light being supplied to the image sensor and the other part being supplied to the measuring unit, e.g.
  • the image values of the image supplied by the image sensor are transformed, e.g. converted into color coordinates, by means of a computing unit (e.g. computer).
  • the radiometric, photometric or colorimetric measurement is not carried out for just one measuring spot on the test object, as in the prior art, but for several measuring spots located at different positions on the test object, or for several measuring angles.
  • the measurement variables e.g. the "true" color coordinates for the light emitted by the measuring spot/measuring angle, are measured separately for each measuring spot/measuring angle.
  • An individual set of precise measurement variables e.g. color coordinates
  • is therefore available for each measuring spot/measuring angle which are taken into account in the transformation of the image values obtained by means of the image sensor. Consequently, spectral properties of the light emission that vary across the surface of the test object—unlike in the prior art—can be taken into account in the transformation.
  • the color coordinates obtained are correspondingly more precise, in particular less subject to systematic errors dependent on the beam angle.
  • the color coordinates are preferably XYZ color coordinates (tristimulus values) in the CIE standard valence system or coordinates derived therefrom, such as the xy color locus coordinates or Lu'v' coordinates in the CIE LUV color space system.
  • the specification of the so-called dominant wavelength or the color temperature can also be included in the color coordinates.
  • the concept of color coordinates stands for colorimetric data for the quantification of physiological color perception, while the concept of color values of the Image sensor for information in a different color system according to the spectral properties (spectral channels) of the image sensor (eg RGB).
  • the color coordinates are the relevant variables for assessing the quality of the test objects (e.g. matrix displays).
  • the system has conoscopic optics that are designed to image the light emitted from an area on the test object at different angles onto the image sensor in such a way that a different emission angle is assigned to each pixel of the two-dimensional digital image.
  • the second part of the light can be received by the measuring unit or units in a particularly simple manner in that the radiometric and/or photometric measured variables, in particular the color coordinates of the emitted light, are recorded for individual measuring angles.
  • the transformation of the image values into color coordinates takes place in two steps: i) transformation of the image values into color coordinates on the basis of a transformation rule determined in advance by calibration, ii) correction of the color coordinates obtained in step i), the correction being based on a comparison of the Step i) obtained color coordinates are derived with the color coordinates recorded for the measuring spots.
  • a transformation rule is determined in advance by calibration, e.g. by measuring a number of reference objects, e.g. in the form of a transformation matrix, which calculates the color value vector for each pixel of the image of the image sensor into a vector of color coordinates.
  • the image values of the image generated by the image sensor are first transformed into color coordinates on the basis of the transformation matrix. These "raw values" are then corrected on the basis of the color coordinates recorded parallel to the test object for the measuring spots/measuring angles.
  • the correction is based not only on the color coordinates recorded for one measurement spot, but also on the basis of color coordinates recorded for two or more measurement spots at different positions on the test object or at different measurement angles. This reduces the errors that previously occurred due to a spatially inhomogeneous emission.
  • the correction includes dividing the image into spatially separate zones, with each zone being assigned a measuring spot/measuring angle and the correction for each zone being based on a comparison of the color coordinates within this zone obtained in step i) with those for this Zone associated measurement spot / measurement angle detected color coordinates is derived.
  • the correction resulting from this measuring spot/measuring angle is applied specifically to those pixels that are in the same zone, i.e. near the relevant measuring spot/measuring angle. This directly takes into account the spatial deviations of the light emission, assuming that the variation of the light emission is spatially continuous, e.g. in the form of a spectral shift that increases continuously with increasing distance from the optical axis.
  • the correction of the color coordinates applies an interpolation according to the positions of the measuring spots/measuring angles within the image.
  • the interpolation eg linear or cubic
  • the model can then be parameterized on the basis of the color coordinates recorded for the measuring spots/measuring angles and used to correct the color coordinates for all pixels obtained by means of the transformation rule.
  • the image values of the image of the image sensor are transformed on the basis of a transformation rule that is derived from the image values of the digital image captured by the test object and the color coordinates captured by the same test object for the measuring spots/measuring angles.
  • This procedure does not require a calibration carried out beforehand, because the transformation rule is calculated “in situ”, so to speak, using the image values recorded simultaneously by the image sensor for the measurement spots/measurement angles (in the color system of the image recorded by the image sensor) and color coordinates recorded by the colorimeter (in the desired color system, eg in the CIE standard valence system) can be determined.
  • the number of measuring spots/measuring angles should be at least equal to the number of spectral channels of the image sensor used. This is not possible with only one measuring spot (as in the prior art).
  • This configuration is particularly advantageous because it does not require (time-consuming) prior calibration and because it simultaneously takes into account the inhomogeneous emission properties of the test object and thus ensures improved precision of the determined color coordinates compared to the prior art. This configuration is, so to speak, “self-calibrating”.
  • the image comprises at least three, preferably at least five, particularly preferably at least nine image values for each pixel.
  • three spectral channels of a common RGB image sensor prove to be insufficient for some applications in order to enable precise conversion of the image values into color coordinates. The reason for this is simply that with only three color channels too much spectral information is lost. With more spectral channels, the precision can be significantly improved.
  • An image sensor (such as a multispectral camera) with nine (or more) spectral channels has proven to be particularly suitable.
  • the measurement spots on the test object are at different radial distances from the recording axis of the image sensor.
  • This arrangement of the measuring spots takes into account the fact that with some display types that come into question as test objects (e.g. OLED displays), the spectral shift of the emission depends on the viewing angle, i.e. on the distance of the emission point from the center of the display, where the recording axis of the image sensor is the display surface intersects, depends.
  • Figure 1 schematic representation of a first
  • Figure 2 schematic representation of a second
  • FIG. 3 Illustration of the spectral detection of measurement spots in the second exemplary embodiment using GRISM;
  • Figure 4 schematic representation of a third
  • FIG. 5 Illustration of the assignment of zones to measurement spots when correcting color coordinates
  • FIG. 6 Illustration of the determination of color coordinates by means of an image sensor of a multispectral camera using a plurality of measurement spots recorded colorimetrically.
  • the imaging system 1 of FIG. 1 comprises an objective 3, which collimates the light emitted by a test object, namely a matrix display 2 (eg OLED display).
  • a beam splitter 4 is arranged downstream of the lens 3 in the beam path as splitting optics. The beam splitter 4 divides the light coming from the matrix display 3 into a first part 5 and a second part 6 .
  • the image output by the image sensor 7 is displayed transmitted to a computer (not shown) connected to the image sensor 7.
  • Two coupling units 9, 10 of light-conducting fibers 11 and 12, respectively, are arranged in a common plane 8 within the beam cross-section of the second part 6 of the light.
  • the light is correspondingly coupled into the fibers 11 and 12 at the positions at which the two coupling units are located. In this way it is achieved that the light propagating in the fiber 11 comes from a first measuring spot 13 and the light propagating in the fiber 12 comes from a second measuring spot 14 on the matrix display 2 .
  • the positions of the coupling units 9, 10 in the plane 8 determine the positions of the measuring spots 13, 14 on the matrix display 2. As can be seen clearly in FIG light emitted by the corresponding positions on the matrix display 2 is detected by the lens 3 .
  • An imaging spectrometer 17 (hyperspectral camera) is used as the measuring unit (colorimeter).
  • the two fibers 11, 12 lead to different (vertical) positions on the entrance slit of the imaging spectrometer 17, so that each measurement spot 13, 14 is associated with a different image area of the imaging spectrometer.
  • the spectrometer 17 (or the computer connected to it) is able to record a spectrum separately for each measuring spot 13, 14 and to determine the color coordinates from this.
  • the imaging spectrometer 17 is also connected to the computer.
  • the computer is programmed by which the image values of the pixels of the image output by the image sensor 7 are displayed in color coordinates be transformed in the CIE standard valence system. The color coordinates precisely recorded by means of the spectrometer for the measuring spots 13, 14 are taken into account as a reference.
  • a further image sensor 21 comprises.
  • Each of the holes in the perforated mask corresponds to a measurement spot 13, 14.
  • the spatial arrangement of the holes determines the positions of the measurement spots 13, 14 on the matrix display 2.
  • Figure 3 illustrates the functional principle of the colorimeter 19.
  • Figure 22 in Figure 3 shows an example hole pattern the perforated mask 18.
  • the dispersive element 20 brings about a spatial separation of the wavelength components on the image sensor 21 for each measurement spot, as illustrated in figure 23 in FIG.
  • the spatial separation of the wavelength components is marked at 24 as an example for the extreme right measuring spot.
  • a spectrum as shown in Figure 25 can be acquired accordingly for each measurement spot. From this, the color coordinates for the measuring spot in question can then in turn be derived by means of the computer.
  • the light emitted by the measuring spots 13, 14 via the two fibers 11, 12 is supplied to two separate colorimeters 15, 16, for example conventional filter colorimeters, as measuring units. Accordingly, the colorimeters 15, 16 detect the color coordinates of the emitted light separately for each of the two measurement spots 13, 14.
  • the two colorimeters 15, 16 are connected to the computer.
  • the computer is programmed by which the image values of the pixels of the image output by the image sensor 7 are transformed into color coordinates in the CIE standard valence system.
  • the color coordinates precisely recorded by means of the colorimeters 15, 16 for the measuring spots 13, 14 are taken into account as a reference. It should be pointed out that the exemplary embodiments in FIGS.
  • FIG. 3 illustrates, likewise only by way of example, an embodiment with a total of 36 measurement spots.
  • the lens 3 can be a conoscopic lens that is designed to be of a limited (possibly approximately punctiform) area on the test object 2 at different angles project the emitted light onto the image sensor 7 in such a way that a spatial emission angle (e.g. given by the polar angle and the azimuth of the emission) is assigned to each pixel of the two-dimensional digital image. This makes it possible to measure the angle-dependent emission characteristics of the test object 2 precisely.
  • a spatial emission angle e.g. given by the polar angle and the azimuth of the emission
  • the spatial arrangement of the holes in the perforated mask 18 determines the (here two) measuring angles.
  • the image values of the image sensor 7 can be transformed into CIE color coordinates on the basis of a previously performed calibration with subsequent correction based on the color coordinates determined for the measuring spots 13, 14, similarly to the cited EP 3 054 273 A1.
  • a transformation rule is determined once beforehand by calibration, for example in the form of a transformation matrix, which converts the image value vector for each pixel of the image of the image sensor 7 into a vector of the color coordinates.
  • the image values of the image generated by the image sensor 7 are first transformed into color coordinates on the basis of the Transformation matrix, ie based on the calibration that has taken place.
  • FIG. 5 illustrates that the correction can provide for a subdivision of the image 28 into spatially separate zones (zone 1, zone 2), with each zone being assigned a measurement spot 13, 14.
  • the correction is derived for each zone from a comparison of the color coordinates within this zone, previously obtained by transformation on the basis of the calibration, with the color coordinates recorded for the measuring spot 13, 14 assigned to this zone.
  • the correction can be, for example, a simple scaling of the individual color coordinates X, Y and Z, corresponding to the ratio of the color coordinates initially obtained by transformation matrix for the positions of the measuring spots 13, 14 and the colorimeters 15, 16, 17, 19 for the respectively corresponding measuring spot 13, 14 precisely recorded color coordinates. This correction is then applied to all transformed color coordinates within the zone in question.
  • FIG. 5 shows two possible variants for subdividing into zones. The subdivision is expediently chosen according to the course of change in the light emission over the surface of the matrix display 2 .
  • the image values of the image from the image sensor 7 can be transformed on the basis of a transformation rule which is derived from the image values of the digital image captured by the matrix display 2 and from the same matrix display 2 (in parallel or sequentially) for the measurement spots 13, 14 is derived from the color coordinates detected by the colorimeter 15, 16, 17, 19.
  • the transformation rule is determined “in situ”, so to speak, using the image values recorded for the measurement spots 13 , 14 by the image sensor 7 and also the color coordinates recorded by the colorimeter 15 , 16 , 17 , 19 .
  • Diagram 29 illustrates the sensitivities of the nine spectral channels of image sensor 7.
  • Figure 30 shows a plan view of matrix display 2 to be measured with a number of nine measurement spots located thereon at nine different distances R1-R9 from the Center of the matrix display 2.
  • the colorimeter 15, 16, 17, 19 is used to precisely record the XYZ color coordinates of the light emission for all of the measurement spots, either in parallel or sequentially.
  • Diagram 31 shows the spectra of the light emission at the various measurement spots with increasing distance (arrow direction) from the center of matrix display 2. The distance-dependent shift in the emission spectrum can be clearly seen. This results in nine sets of XYZ color coordinates for the nine measurement spots:
  • the measurement using the multispectral image sensor 7 results in nine image values for each of the nine measuring spots corresponding to the nine spectral channels of the image sensor 7:
  • matrix CCM The 9x3 matrix of the XYZ color coordinates is linked to the 9x9 matrix of the image values via the required transformation rule (hereinafter referred to as matrix CCM):
  • the transformation rule CCM can be determined in real time by numerically solving the inverse problem using the computer (for example based on the known method of minimizing the squared deviations or using other known algorithms). With a sufficient number of measurement spots (here at least nine, corresponding to the number of spectral channels of the image sensor 7), it can be ensured that there is sufficient data for solving the inverse problem for finding the correct transformation rule CCM.
  • This approach to the Transformation of the image values of the image sensor 7 into CIE color coordinates, taking into account the color coordinates directly colorimetrically recorded for the measuring spots, is particularly advantageous because it does not require calibration to be carried out beforehand and also automatically takes inhomogeneous emission properties of the measured matrix display 2 into account.
  • the procedure described with reference to FIG. 6 does not depend on the use of a multispectral image sensor 7 .
  • the same method can also be used analogously, e.g. with an RGB image sensor 7 or an imaging filter wheel colorimeter with a monochrome image sensor, which has only three spectral channels.
  • a minimum of three measurement spots is then sufficient to determine the transformation rule CCM.
  • a number of measurement spots that is even larger than the number of spectral channels can be advantageous in order to determine the transformation rule CC/W numerically with greater accuracy.
  • the inverse problem to be solved is then overdetermined.
  • a transformation rule can be derived for different spatial areas of the test object, i.e. the matrix display 2, without prior calibration.
  • a transformation rule CCM1 can be derived from the measurement spots at the distances Ri, R2, R3, a transformation rule CCM2 from the measurement spots at the distances R2, R3, R4, a transformation rule CCM3 from the measurement spots at the distances R3, R4, Rs, etc.
  • These transformation rules are then used to transform the RGB image values into color coordinates for the pixels in the various areas, i.e. here in the ring-shaped areas determined by the corresponding distances Ri to R9 from the center.

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Abstract

L'invention concerne un système d'imagerie conçu pour la mesure bidimensionnelle, à résolution spatiale de grandeurs de mesure radiométriques et/ou photométriques, en particulier des coordonnées chromatiques de la lumière émise par un objet à tester (2). Un capteur d'image (7) reçoit une première partie (6) de la lumière et génère une image numérique bidimensionnelle de l'émission lumineuse de l'objet à tester (2). Une unité de mesure (15, 16, 17, 19) reçoit une deuxième partie (6) de la lumière et détecte des grandeurs de mesure radiométriques et/ou photométriques pour différents points de mesure (13, 14) ou angles de mesure. Une unité de calcul transforme les valeurs d'image d'au moins quelques points d'image de l'image générée, la transformation tenant compte des grandeurs de mesure détectées pour les points de mesure (13, 14) ou les angles de mesure. Cette invention a pour but de développer un système amélioré par rapport à l'état de la technique. En particulier, la détermination des coordonnées chromatiques lors de la mesure d'affichages avec une émission spectrale spatialement non homogène doit être plus précise par rapport à l'état de la technique. Pour obtenir ce résultat, l'invention propose que l'unité de mesure (15, 16, 17, 19) comprenne un spectromètre d'imagerie qui peut déterminer séparément les grandeurs de mesure pour chaque point de mesure (13, 14) ou angle de mesure. En variante, deux ou plusieurs unités de mesure (15, 16, 17, 19) peuvent être utilisées, une unité de mesure (15, 16, 17, 19) étant associée à chaque point de mesure (13, 14) ou angle de mesure. L'invention concerne également un procédé de mesure bidimensionnelle, à résolution spatiale de grandeurs de mesure radiométriques et/ou photométriques, en particulier des coordonnées chromatiques de la lumière qui utilise un tel système d'imagerie (1).
EP22843783.6A 2021-12-23 2022-12-22 Procédé et système de colorimétrie Pending EP4453522A2 (fr)

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CN119779486B (zh) * 2025-03-10 2025-12-09 上海唯视锐光电技术有限公司 一种成像色度测量方法及基于该测量方法的测量装置

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US6051835A (en) * 1998-01-07 2000-04-18 Bio-Rad Laboratories, Inc. Spectral imaging apparatus and methodology
JP2007158700A (ja) 2005-12-05 2007-06-21 National Univ Corp Shizuoka Univ 色忠実カメラ
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JP2010271246A (ja) 2009-05-22 2010-12-02 Sony Corp 色彩輝度測定装置及び色彩輝度測定方法
WO2015117000A1 (fr) * 2014-01-30 2015-08-06 Horiba Instruments Incorporated Système et procédé de cartographie spectroscopique
DE102014106974A1 (de) * 2014-05-16 2015-11-19 Cubert GmbH Räumlich und spektral auflösende Hyperspektralkamera und Verfahren
CN106461465B (zh) * 2014-05-29 2018-05-25 柯尼卡美能达株式会社 光学特性测定装置以及光学特性测定方法
EP3054273B8 (fr) 2015-02-09 2019-09-11 Instrument Systems Optische Messtechnik GmbH Système de colorimétrie pour test d'affichage
US11627259B2 (en) * 2019-10-24 2023-04-11 Sony Corporation Device, method and computer program
WO2023283742A1 (fr) * 2021-07-14 2023-01-19 Westboro Photonics Inc. Imageur et échantillonneur de spot à étage de translation
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