System and method for measuring color of sample regions

Abstract

A system and method of measuring a color of a sample region. The system comprises: a light source; the first optical device is used for partially scanning the sample areas one by one; a second optical device including a second optical device and an optical element for collecting light scattered from the sample; the spectrograph is used for receiving the collected scattered light and measuring the spectrum of each part; and a computing device. The system is configured to synchronize the scanning of the region with the recording of the spectrum of the portions of the region. The second optical device is configured to change and dynamically adjust a propagation direction of the redirected scattered light in synchronization with the first optical device. The computing device determines color coordinates, computes and analyzes the overall spectrum, and computes XYZ tristimulus values.

Description

Technical Field

[0001] The present invention relates generally to color measurement. In particular, the present invention relates to a system and method for measuring the color of a sample area. Background Art

[0002] Some of the most demanding color measurement applications require systems and methods that can provide accurate color measurements at high speed and low cost. Some more demanding applications also require measuring the color of an object at a distance and being able to be combined with other parallel processes (such as processes performed on a factory production line). Most of the existing technologies in the field of color measurement cannot meet the above requirements because the systems and methods involved require the use of complex and expensive equipment and special conditions in order to achieve accurate and fast measurements. Special conditions are, for example, zero ambient lighting or very low ambient lighting, and / or placing the sample in a special housing or in contact with a special housing, and / or contacting the sample with a color measurement device. The special conditions are incompatible with the environment in which the color measurement must be performed. Similarly, accurately determining the color of a sample usually requires accurate multi-angle measurement of the sample, but it is challenging to perform the multi-angle measurement from a distance and under strong light exposure to the sample in the environment.

[0003] Patent application document US2018 / 0180480A1 describes a multi-angle colorimeter, which includes a light illumination and receiving optical system, a spectrum block, a control unit and a housing, and also describes that the color of a sample can be measured, and the observed color of the sample changes according to the colorimetric observation direction of each of multiple light receiving angles. However, US2018 / 0180480A1 also describes that when measuring the color, the pressing part of the housing is pressed against the sample.

[0004] Similarly, patent application document US2006 / 0109474A1 describes a multi-angle colorimeter for measuring an object, and the colorimeter includes an illumination system, a ring mirror, a light detection system, a controller / computer, and a housing having a measurement opening, wherein the measurement opening faces the surface of the object and has a perimeter for defining a predetermined measurement area on the surface of the object.

[0005] As can be appreciated from the above, there is a need for methods and systems for accurately measuring sample color from a distance and capable of providing multi-angle measurements simultaneously. In addition, there is a need for methods and systems that ensure or are intended to not require or be necessary to reposition the illumination source and / or spectrometer during measurement, or to use multiple illumination sources and / or spectrometers, for the purpose of accurately measuring color, particularly during the multi-angle measurements. Summary of the invention

[0006] The present invention provides a system and method for measuring color, wherein the color is measured remotely, online or offline, in real time, and the measurement is not affected by ambient lighting. The system and method are non-invasive: after analysis, the sample under investigation remains undamaged and unchanged (for example, no need to cut a piece of the sample to measure its color). The present invention is applicable to measuring the color of various materials, such as textiles, polymers, organic materials, plastics, glass, metals, wood, ceramics, and pigments (natural or synthetic) used for painting or dyeing, etc. The present invention allows advanced color measurement in or near existing production lines or other complex settings. The present invention provides a system that is easily expandable, rugged, and can be made compact and has a small form factor to achieve multi-functionality and portability. The present invention does not require the use of very expensive equipment. The present invention allows measurement of areas of different sizes and shapes. The present invention allows color mapping to be performed with high resolution. Very importantly, the present invention allows multi-angle color measurement to be performed without the need to reposition the illumination source and / or spectrometer during measurement, and without the need to use multiple illumination sources and / or spectrometers.

[0007] To this end, an embodiment of the present invention discloses a system for measuring the color of a sample area, comprising: a light source configured to emit light to illuminate a sample; a first optical device configured to receive the light to output a collimated beam of the light and direct it to the surface of the sample located at a given distance, the first optical device comprising a first optical device configured to change and dynamically direct the direction of the collimated beam toward the sample, thereby scanning the sample area section by section; a second optical device configured to collect light scattered from the sample when illuminating the sample with the collimated beam; a spectrometer configured to receive the collected scattered light (i.e., the scattered light collected by the second optical device) and record the spectrum of the collected scattered light for each (scanned) section; and a computing device operably connected to the spectrometer. Section by section can be row by row, point by point, or spot by spot. Preferably, the area is scanned by illuminating each row of the area, that is, scanning the area row by row. The scattered light received by the spectrometer can be or include backscattered light, i.e., light backscattered from the sample when illuminating the sample with the collimated beam.

[0008] The second optical arrangement includes a second optical device and an optical element. The second optical device is configured to receive light scattered by the sample, and when the collimated light beam is incident on the surface of the sample, the scattered light is scattered at an observation angle α relative to the direction of the specular reflection component reflected from the sample. In addition, the second optical device is also configured to redirect the received scattered light to the optical element.

[0009] Furthermore, during scanning of the sample area, the second optical device is further configured to synchronously change and dynamically adjust the propagation direction of the redirected scattered light with the first optical device, so that the propagation direction of the redirected scattered light remains unchanged (ie the same) relative to the optical element.

[0010] In the proposed system, the light emitted by the light source includes a spectrum of wavelengths emitted simultaneously, and the spectrum continuously covers at least one wavelength band from a first wavelength to a second wavelength in the visible light range. In addition, the light emitted by the light source is spatially coherent, at least for all wavelength bands from the first wavelength to the second wavelength. The spectrum is most preferably a wide spectrum, such as a spectrum with a width exceeding 10 nanometers, 50 nanometers, or 100 nanometers.

[0011] Furthermore, the system is configured to synchronize the scanning of the region with the recording of spectra of portions of the region by the spectrometer as the first optical device scans the region. Likewise, the system is configured to record the spectrum of each portion (each scanned portion) for a spectral integration time equal to the duration of the scanning of the portion by the first optical device.

[0012] The first optical device for outputting a collimated light beam is configured to maintain the collimated spatially coherent light if or when the spatially coherent light is collimated; and / or the optical device further comprises a collimator to perform collimation of the spatially coherent light. Preferably, the collimator is located at a specific distance from one end of the light source.

[0013] Thus, the spatially coherent light emitted by the light source may or may not be collimated when leaving the light source. Likewise, the light may or may not be collimated before being received by the first optical device. The latter may maintain the collimation of the light by having optical elements that do not destroy the collimation. Likewise, the first optical device may include a collimator as described above to cause or improve the collimation of the light. Likewise, optionally, the system may include a collimator between the light source and the first optical device for collimating the light from the light source to the first optical device.

[0014] According to the above, it can be imagined that the first optical device has a collimator (such as a collimator lens or a collimator mirror) located at a certain distance (corresponding to the focal length of the collimator) from one end of the light source to convert the spatially coherent light into a collimated beam.

[0015] The computing device is configured to calculate an overall spectrum by performing statistical calculations on all or some spectra corresponding to all or some scanned portions of the region, and to determine the color coordinates of the sample region in a given color space by analyzing the overall spectrum, wherein the analysis includes calculating XYZ tristimulus values ​​corresponding to the overall spectrum. It can be clearly understood that calculating the overall spectrum requires performing the statistical calculations, i.e., calculating the overall spectrum includes or is completed by (with the aid of) performing the statistical calculations.

[0016] The overall spectrum may optionally be a statistical average (mean), median or mode of all or some spectra corresponding to all or some scanned portions of the region, as well as other advantageous statistics. Preferably, the overall spectrum is an average (mean) spectrum, calculated from all spectra corresponding to all scanned portions of the region.

[0017] In a preferred embodiment, the propagation direction of the redirected scattered light is parallel to the main optical axis of the optical element. Also, preferably, the optical element is an off-axis parabolic mirror. Thus, the system can benefit from an optical design that is both well-functioning and easy to implement.

[0018] In a preferred embodiment, the observation angle α is about 45 degrees, and the first optical device is further configured to change and dynamically adjust the direction of the collimated light beam to be oriented around a central direction perpendicular to the sample surface during the portion-by-portion scanning of the sample area. Thus, the system can optionally provide CIE 0 / 45 (i.e., 0° / 45°) color measurement to meet the requirements for standardization purposes in many industrial applications.

[0019] In a preferred embodiment, the first optical device and the second optical device include respective galvanometer mirrors. The use of galvanometer mirrors, in particular commercially available galvanometer mirrors, can advantageously simplify the overall optical design of the system. In addition, optionally and preferably, the second optical device also includes an optical fiber optically coupled to the spectrometer. Optically coupling (i.e., connecting) the spectrometer to the second optical device using an optical fiber can advantageously help to reduce the form factor of the system and / or make the system portable. In addition, in a preferred embodiment, the optical element is configured to receive scattered light redirected by the optical element and further redirect the light to the input end of the aforementioned optional optical fiber.

[0020] In a preferred embodiment, the optical element of the system is an off-axis parabolic mirror with a through hole, and the system further comprises a laser configured to emit a laser through the hole to the second optical device. Thus, the second optical device can further redirect the laser to the sample surface. Using the position of the laser and the collimated light beam to illuminate the sample, the first optical device and the second optical device can be optically aligned before the color measurement is performed. The optical alignment can be used to make the laser and the collimated light beam coincide on the sample surface, which is used to ensure that the second optical device correctly redirects the scattered light to be parallel to the optical axis of the off-axis parabolic mirror. In this way, the collection of the scattered light by the second optical device can be advantageously optimized.

[0021] Optionally and preferably, the spatially coherent light source is or includes a supercontinuum light source. Optionally, the light source, such as the optional supercontinuum light source, includes a nonlinear optical fiber or an optical fiber configured to be excited by light and emit a supercontinuum spectrum. Advantageously, this selection can further make the system compact, durable and portable.

[0022] In one embodiment, the first wavelength is included in the range between 370nm and 460nm, and the second wavelength is included in the range between 620nm and 780nm. In a specific embodiment, the first wavelength is 430nm. In another specific embodiment, the second wavelength is 750nm. In another specific embodiment, the first wavelength is 400nm. In another specific embodiment, the second wavelength is 780nm. In another specific embodiment, the first wavelength is 380nm and the second wavelength is 750nm. Optionally, controlling the first wavelength and the second wavelength can improve the accuracy of the measurement and / or allow the system to be adjusted according to the expected color of the sample.

[0023] In one embodiment, the collimated light beam has a maximum full-angle divergence angle of 0.46 degrees or less for all wavelengths from the first wavelength to the second wavelength. Optionally and preferably, the maximum full-angle divergence angle is between 0.01 and 0.20 degrees for all wavelengths from the first wavelength to the second wavelength. This option can allow control of the direction and diameter of the light beam and can facilitate accurate measurement of samples at different distances from the system.

[0024] In one embodiment, the first optical device comprises a collimator, preferably a collimating lens, and the first optical device is at a distance from the collimator, the distance corresponding to the focal length of the collimator, and for all wavelengths from the first wavelength to the second wavelength, the diameter of the cross section of the collimated light beam is 5 mm or less, in particular less than 2.15 mm, the diameter being considered to be 1 / e 2 Width. This choice helps to achieve high spatial resolution and good signal-to-noise ratio during the measurement.

[0025] In one embodiment, for all wavelengths from the first wavelength to the second wavelength, the diameter of the cross-section of the collimated light beam is 10 mm or less at any distance from a point 1 m or less from the first optical device, and / or the diameter is 100 mm or less at any distance from a point 10 m or less from the first optical device, which diameter is considered to be 1 / e 2 Preferably, when (if) the first optical device comprises said collimator, said point is at the collimator. Likewise, optionally, said point is located at the optical exit of the first optical device, said optical exit being an optical port, aperture, material or gap from which the light beam leaves the first optical device.

[0026] Likewise, optionally, the point is located at a first optical device that changes and dynamically adjusts the direction of the light. These options help improve the performance of measurements of samples at different distances with good resolution, even when the sample receives a lot of other light from the environment.

[0027] In one embodiment, for all wavelengths from the first wavelength to the second wavelength, the beam quality factor M of the collimated beam is 2 The quality factor M ranges from 1.0 to 2.0. In certain embodiments, the quality factor M 2 Below 1.4. This option helps control and optimize the system's illumination of the sample.

[0028] In one embodiment, the brightness of the collimated light beam composed of all wavelengths from the first wavelength to the second wavelength is 1 mW / cm at any distance of 1 m from the first optical device or less. 2 Or higher; Optionally or additionally, at any distance of 10m or less from the first optical device, the brightness is 0.01mW / cm 2 or higher, wherein when (if) the first optical device comprises said collimator, said point is preferably at the collimator. In a specific embodiment, the brightness is 136 mW / cm at a distance of 1 m from the collimating lens. 2 , 2.8mW / cm at a distance of 10m from the collimating lens 2 . These options help optimize the accuracy of your measurements.

[0029] An embodiment of the present invention also discloses a method for measuring the color of a sample area. The method includes emitting light with a light source to illuminate a sample located at a given distance from the light source, the light including a wavelength spectrum emitted simultaneously, the spectrum at least continuously covering a wavelength band from a first wavelength to a second wavelength in the visible light range, and the light is spatially coherent at least at all wavelengths from the first wavelength to the second wavelength; receiving the spatially coherent light at a first optical device at a certain distance from one end of the light source; at the first optical device, if the spatially coherent light is collimated, maintaining the collimated spatially coherent light, and / or collimating the spatially coherent light with a collimator; outputting and guiding the collimated beam of the spatially coherent light to the sample surface at a given distance from the first optical device through the first optical device; scanning the sample area part by part; changing and dynamically adjusting the collimation through the first optical device of the first optical device. direction of the light beam; collecting light scattered from the sample by a second optical device, the second optical device comprising a second optical apparatus and an optical element; recording by a spectrometer the spectrum of the scattered light collected by the second optical device from each (scanned) portion of the sample; synchronizing the scanning of the area with the recording of the spectra of the portions of the area by the spectrometer, wherein the spectrum integration time for recording the spectrum of each portion is equal to the duration of the optical device scanning the portion; and calculating an overall spectrum by performing statistical calculations on all or some of the spectra corresponding to all or some of the scanned portions of the area through a computing device operably connected to the spectrometer, and measuring the color coordinates of the sample area in a given color space by analyzing the overall spectrum, the analysis comprising calculating XYZ tristimulus values ​​corresponding to the overall spectrum. In the method according to the present invention, collecting scattered light through a second optical device includes: receiving light scattered by a sample through a second optical device, when a collimated light beam is incident on the sample surface (i.e., because the collimated light beam is incident on the sample surface), the scattered light is scattered at an observation angle relative to the direction of a specular reflection component reflected from the sample; redirecting the received scattered light to an optical element through the second optical device; and during scanning of the sample area, changing and dynamically adjusting the propagation direction of the redirected scattered light synchronously with the first optical device through the second optical device, so that the propagation direction of the redirected scattered light remains unchanged relative to the optical element.

[0030] In the method, optionally and preferably, the sample is located at a given distance of 0.5 m or more from the first optical device. Optionally, the method comprises providing the sample at the given distance.

[0031] In one embodiment, the synchronization is performed using a time-dependent voltage signal. Preferably, the voltage signal is square.

[0032] In one embodiment, the sample, while being illuminated by the collimated light beam, also receives additional light from the environment.

[0033] In one embodiment, the spectral integration time is determined by continuously scanning a portion of the area of ​​the white reference object by the first optical device; while scanning the portion, recording spectra with different spectral integration times by the spectrometer, the spectral integration times increasing gradually and discretely with a certain constant time difference; and selecting the maximum spectral integration time of the spectrum that is not saturated at any wavelength as the spectral integration time. Optionally and preferably, the portion is the periphery of the area of ​​the white reference object.

[0034] In one embodiment, calculating the XYZ tristimulus values ​​includes: calculating a reflectance curve using the overall spectrum of the sample area, the overall spectrum of the white reference, and the background spectrum, preferably "overall" is "average"; multiplying the calculated reflectance curve by the CIE standard light source spectrum curve, the CIE standard observer spectrum curve, and a normalization constant. It should be noted that the CIE standard observer is described by 3 different spectral curves (functions), namely, three CIE standard observer spectrum curves (functions), each curve is used to calculate X, Y, and Z respectively [Reference 4, Reference 5].

[0035] Other embodiments of the present invention disclosed herein also include software programs to perform the method embodiment steps and operations summarized above and disclosed in detail below. More specifically, a computer program product is an embodiment having a computer readable medium, the computer readable medium including computer program instructions encoded thereon, which, when executed on at least one processor in a computer system, causes the processor to perform the operations shown herein as embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The foregoing and other advantages and features will be more fully understood from the following detailed description of embodiments, with reference to the accompanying drawings, which must be considered in an illustrative and non-limiting manner, in which:

[0037] Figure 1 A system for measuring the color of a sample area according to an embodiment of the present invention is schematically shown.

[0038] Figure 2A A diagram showing the spatiotemporal synchronization process between sample scanning and spectral recording is shown.

[0039] Figure 2B An exemplary oscilloscope trace of a voltage signal used for synchronization between a galvanometer mirror scanner and a spectrometer is shown.

[0040] Figure 3A-3C and Figure 4 A picture showing a sample illumination step similar to some embodiments of the method according to the invention.

[0041] Figure 5 Describes a situation in which the perception of color depends on the relative orientation of the illuminating source, the specimen, and the observer. Figure 5 Also shown are the reflection angle θ of the specular reflection component and the observation angle α relative to the direction of the specular reflection component.

[0042] Fig. 6A An embodiment of a system according to the invention is schematically shown.

[0043] Figure 6B An embodiment of a system according to the invention is schematically shown.

[0044] Fig. 7A An embodiment of a system according to the invention is schematically shown.

[0045] Figure 7B An embodiment of a system according to the invention is schematically shown.

[0046] Figure 8 Shown is a reflectance spectrum of a coated aluminum sample measured using an embodiment of the system and method of the present invention. Figure 8 Also shown are the theoretical reflectance spectra provided by the sample manufacturer. DETAILED DESCRIPTION

[0047] Figure 1 An embodiment of the proposed system is shown for measuring the regional color of a sample 300. Some non-limiting examples of said samples are: textiles, polymers, organic materials, plastics, glass, metals, wood, ceramics, pigments (natural or synthetic), etc. Figure 1 In an embodiment of the present invention, the system includes a light source 100; a first optical device 200; a second optical device 500; a spectrometer 400 and a computing device (not shown) having one or more processors and at least one memory operably connected to the spectrometer 400.

[0048] The light emitted by the light source 100 includes a spectrum of wavelengths emitted simultaneously. Figure 1 In the embodiment of the present invention, the spectrum at least continuously covers a wavelength band from a first wavelength (370-460 nm) to a second wavelength (620-780 nm) in the visible light range.

[0049] The light emitted by the light source 100 is spatially coherent, at least for all wavelengths from the first wavelength to the second wavelength. Preferably, the spatially coherent light propagates in the form of a collimated light beam, at least for all wavelengths from the first wavelength to the second wavelength. According to known definitions, spatially coherent light should be understood as light with a certain beam profile, wherein the electric fields at different positions on the beam profile have a fixed phase relationship, and thus the electric fields are correlated. The spatial coherence of the light allows the light used to be highly directional, which helps to minimize the optical losses of the system and allows robust color measurement and possible high-resolution color mapping of the sample even when the sample is far away from the system or receives a lot of ambient light.

[0050] Spatially coherent light may preferably have a high degree of spatial coherence. The degree of spatial coherence may be determined, for example, by modulating the complex coherence between a pair of points (point 1 and point 2) on the beam cross section. To determine [reference 1], and for example measured by a fiber interferometer or Young's double slit method, as shown in [reference 1, reference 2]. For spatially coherent light in the system, at least for all wavelengths from the first wavelength (370-460nm) to the second wavelength (620-780nm), the coefficient of the complex coherence degree may preferably be in the range of, for example, between 0.5 and 1.0, preferably in the range of between 0.8 and 1.0.

[0051] In a preferred embodiment, and in Figure 1 In the embodiment of the invention, the light source 100 is a fiber supercontinuum light source, wherein the supercontinuum light is generated in an optical fiber and is transmitted to the end of the light source through the optical fiber 101 or through another optical fiber 101. In such an embodiment, the end of the light source is the end of the optical fiber 101 used to transmit the light of the supercontinuum light source. In the preferred embodiment, the light is emitted from the end to the free space (e.g., air), and the end is the interface between the optical fiber and the free space (e.g., air), which can be in the form of a transversely polished interface (e.g., an ultra-physical contact connector UPC) or an angled polished interface (e.g., an angled polished connector APC), etc.

[0052] In the preferred embodiment, the spectrum of the supercontinuum light continuously covers at least the wavelength band from the first wavelength (370-460nm) to the second wavelength (620-780nm). In the preferred embodiment, all of these wavelengths propagate only in the fundamental transverse mode of the optical fiber used to transmit the supercontinuum light to the end of the light source. Therefore, the light emitted by the light source of this embodiment is spatially coherent, at least for all wavelengths from the first wavelength (370-460nm) to the second wavelength (620-780nm). From the end of the light source, all of these wavelengths can be emitted into free space simultaneously.

[0053] Other non-limiting examples of light sources that can be used in the proposed system include:

[0054] - Light source, including mode-locked laser, such as titanium-sapphire mode-locked laser, or Yb 3+ Mode-locked laser, or Er 3+ A mode-locked laser, etc., and further comprising a nonlinear crystal or a nonlinear optical fiber, which is used to double or triple the frequency of the infrared emission light of the optical radiation emitted by the mode-locked laser. The light emitted by the nonlinear crystal or the nonlinear optical fiber can be spatially coherent light.

[0055] - Light sources, including spatially coherent superluminescent diodes, called SLDs or SLEDs.

[0056] - A light source, comprising a broadband light source, such as an incandescent lamp, a halogen lamp or a white light emitting diode, etc., wherein the broadband light source is configured to emit spatially incoherent light, and the light source also comprises a pinhole, which is used to spatially filter the spatially incoherent light and convert it into spatially coherent light.

[0057] - A light source, comprising a broadband light source, such as an incandescent lamp, a halogen lamp or a white light emitting diode, etc., wherein the broadband light source is configured to emit spatially incoherent light, and the light source also comprises a single-mode optical fiber, wherein the single-mode optical fiber is used to convert the spatially incoherent light into spatially coherent light, and the broadband light source is coupled into the single-mode optical fiber.

[0058] - A light source comprising a nonlinear crystal for generating supercontinuum light.

[0059] All of the above light sources may be spatially coherent in a broad band of wavelengths in the visible range and emit these wavelengths simultaneously. The light emitted by these light sources may naturally propagate in the form of a collimated beam or may be converted into a collimated beam by a collimator, for example consisting of a collimating mirror or a collimating lens or a set of collimating lenses. The light source may optionally include a collimator.

[0060] Alternatively, for situations where the light source does not naturally emit in the form of a collimated beam, such as Figure 1 In the case of an embodiment of the present invention, the first optical device 200 comprises a collimator 205, which is suitable for converting spatially coherent light into a collimated light beam. In one embodiment, the first optical device has a collimator, which is placed at a distance from the end of the light source, the distance corresponding to the focal length of the collimator. In a preferred embodiment where the light source is a fiber supercontinuum light source, such a collimator is placed at a distance from the end of the light source, the distance corresponding to the focal length of the collimator, the distance being measured in the direction of the propagation axis of the optical fiber that transmits the supercontinuum light to the end of the light source.

[0061] The collimated light beam may have a full-angle divergence of 0.46 degrees or less for all wavelengths from the first wavelength to the second wavelength. In a particular embodiment, the full-angle divergence is quoted between 0.01 and 0.20 degrees for all wavelengths from 430 to 780 nm. Also, optionally, the cross-section of the collimated light beam may have a diameter of 5 mm or less at a distance from the collimator 205 corresponding to the focal length of the collimator 205 for all wavelengths from the first wavelength to the second wavelength, and wherein the diameter is considered to be 1 / e of the beam width 2 , that is, the distance between a side point in the beam cross section and the central point of maximum light intensity in the beam cross section, where the light intensity is 1 / e of the maximum light intensity 2 In a particular embodiment, the diameter cited is between 2.1 mm and 2.15 mm at a distance from the collimator 205 corresponding to the focal length of the collimator 205 for all wavelengths from 430 to 780 nm.

[0062] Additionally or alternatively, for all wavelengths from the first wavelength to the second wavelength, the diameter of the cross-section of the collimated light beam may be 10 mm or less at any distance of 1 m or less from the first optical device 200, and / or may be 100 mm or less at any distance of 10 m or less from the first optical device 200, wherein when / if the first optical device 200 comprises the collimator 205, the point at the first optical device is preferably at the collimator 205, and wherein the diameter is considered to be 1 / e of the beam width 2 , that is, the distance between a side point in the beam cross section and the central point of maximum light intensity in the beam cross section, where the light intensity is 1 / e of the maximum light intensity 2 In a specific embodiment where the first optical arrangement comprises a collimator 205, the diameter quoted is between 2.1 mm and 5.3 mm at a distance of 1 m from the collimator for all wavelengths from 430 to 780 nm, and between 5 mm and 37 mm at a distance of 10 m from the collimator for all wavelengths from 430 to 780 nm.

[0063] Thus, in a particular embodiment where the system includes a collimator, the beam cross section incident on a sample at a distance of 1 m or less from the collimator is within 1 / e 2 The diameter at the width is 10 mm or less, and the beam incident on the sample at a distance of 10 m or less from the collimator is within 1 / e for all wavelengths from the first wavelength to the second wavelength. 2The diameter at the width is 100mm or less. In a specific embodiment where the system includes a collimator, preferably for all wavelengths from 430nm to 780nm, at a distance of 1m from the collimator 205, the quoted diameter is between 2.1mm and 5.3mm; and preferably for all wavelengths from 430nm to 780nm, at a distance of 10m from the collimator 205, the quoted diameter is between 5mm and 37mm. For illustration purposes, Figure 4 A picture of light scattered by a textile sample when illuminated by a collimated beam of a supercontinuum light source is shown in an embodiment similar to the present invention. Figure 4 In the example related to the figure, for all wavelengths from 430 to 780 nm, the diameter of the cross section of the beam incident on the sample (in 1 / e 2 The distance between the sample and the collimating lens was between 0.95 and 1 m for all positions of the beam in each sample.

[0064] The spatial resolution of the system, understood as the smallest area of ​​the sample for which the system can provide color coordinates and distinguish them from the color coordinates of neighboring areas of the same size, can be assumed to correspond to a beam diameter in the range of 1 / e 2 The spatial resolution is therefore 78.6 mm for any sample placed at a point 1 m from or within the first optical device or less. 2 or less, or for any sample placed at a distance of 10 m or less from or within the first optical device, the spatial resolution may be 78.6 cm 2 In a specific embodiment in which the first optical device has a collimator, the spatial resolution is 22.1 mm at a distance of 1 m from the collimator. 2 ; When the distance from the collimator is 10m, the spatial resolution is 10.7cm 2 .

[0065] The full divergence angle and the diameter of a collimated light beam may have different values ​​if measured in different directions in the plane of the beam cross section. This may be the case, for example, for a light beam with an elliptical cross section. Therefore, in the present invention, preferably, the full divergence angle of the light beam is the maximum full divergence angle among the full divergence angles of the light beam measured in all directions of the beam cross section. Likewise, in the present invention, preferably, the diameter of the light beam is the maximum diameter among the beam diameters measured in all directions of the beam cross section. In the optional and preferred case of a light beam with a circular cross section, the divergence angle and the diameter of the light beam are equal in all directions of the beam cross section.

[0066] Alternatively, according to ISO Standard 11146 (2005) [Reference 3], for all wavelengths from the first wavelength to the second wavelength, the beam quality factor M of the collimated beam is 2 The range is between 1.0 and 2.0, with 1.0 being the M of a diffraction-limited Gaussian beam. 2 value, and is M 2 Preferably, for all wavelengths from the first wavelength to the second wavelength, the quality factor M 2 Optionally and preferably, the brightness of the collimated light beam consisting of all wavelengths from the first wavelength to the second wavelength is 1 mW / cm at any distance of 1 m or less from the first optical device. 2 or higher, and / or 0.01 mW / cm at any distance of 10 m or less from said point at the first optical device 2 or higher, when the first optical device comprises said collimator, said point is preferably at the collimator. In a specific embodiment in which the first optical device comprises a collimator, such brightness is 136 mW / cm at a distance of 1 m from the collimating lens 2 , 2.8mW / cm at a distance of 10m from the collimating lens 2 .

[0067] At the same time that the sample 300 is illuminated by the collimated light beam, the sample 300 may be illuminated by ambient light, or not illuminated by ambient light at all. Unlike conventional systems configured to measure the color of an area using an optical spectrometer (spectrophotometer), in which ambient light must be avoided to obtain correct color measurements, in the system of the present invention, the measurement of color is not affected by simultaneous illumination from ambient light (thus, the measurement can be performed in a space open to ambient lighting). One reason for this is that the light beam incident on the sample can be selected to have a higher brightness, typically much higher than the brightness of the ambient lighting incident on the sample.

[0068] refer to Figure 1 In an embodiment of the present invention, the first optical device 200 further comprises a first optical device 203, such as an XY galvanometer mirror, configured to change and dynamically adjust the direction of the collimated light beam toward the sample 300, and perform a portion-by-portion scan of an area of ​​the sample 300.

[0069] As described above, a region of the sample 300 is preferably scanned line by line. In one embodiment, a more complete description of the line by line scanning process is as follows: Figure 2A As shown in the figure (right side), the collimated beam is dynamically directed using optical device 203 to sequentially illuminate different points on the sample. Figure 2A(right side of the figure), the positions of the points on the sample are represented by their corresponding coordinates (x, y). 0 ,y 0 ) is oriented to position (x 0 +L x ,y 0 ). This is understood to mean that the scan length is L x Next, the beam is moved from position (x 0 ,y 1 ) is oriented to the position (x 0 +L x ,y 1 ), perform the scan of the second row. Continue this process, using other rows (each row is an arbitrary number n) from position (x 0 ,y n ) to position (x 0 +L x ,y n ) Scan the sample step by step until the edge length L is scanned x and L y The complete area of ​​the sample.

[0070] Alternatively, the scanning of the area may be performed by scanning only a single line. In practice, scanning a line may illuminate a single point or spot of the sample, since the beam cross section or spot has a finite size. Therefore, the smallest area that can be scanned may be the area of ​​the cross section of the beam incident on the sample, which will correspond to the spatial resolution of the system as described above.

[0071] Reference Figure 1 , the second optical device 500 is configured to collect light scattered from the sample when the sample is illuminated with a collimated light beam. In order to collect the scattered light, the second optical device 500 includes a second optical device 503 and an optical element 504, which are configured as follows: the second optical device 503 is configured to receive light scattered by the sample, and when the collimated light beam is incident on the sample surface, the scattered light is scattered at an observation angle relative to the direction of the specular reflection component reflected from the sample. The second optical device 503 is also configured to redirect the received scattered light to the optical element 504. In addition, the second optical device 503 is configured to change and dynamically adjust the propagation direction of the redirected scattered light synchronously with the first optical device 203, so that during the scanning of the area of ​​the sample 300, the propagation direction of the redirected scattered light remains constant relative to the optical element 504. Figure 1 In a preferred embodiment, the optical element 504 is an off-axis parabolic mirror and the second optical device 503 comprises a galvanometer mirror.

[0072] The spectrometer 400 is configured to measure the spectrum of the collected scattered light (i.e. the scattered light collected by the second optical device 500) for each scanned portion of the area. Figure 1 In a preferred embodiment, the optical element 504 is configured to receive the scattered light redirected by the first optical device 503 and further redirect it to the input end of the spectrometer 400.

[0073] The computing device runs / implements one or more algorithms to determine the color coordinates of the sample 300 region in a given color space by calculating the overall spectrum (preferably the average spectrum). To this end, preferably, all spectra of all scanned portions are averaged and XYZ tristimulus values ​​are calculated relative to the average spectrum. Alternatively, the system can determine the color coordinates from a single scan or illuminated portion of the sample.

[0074] Thus, the proposed system measures color using a collimated spatially coherent illumination source that allows for localized illumination at a distance by directing (or guiding) the illumination light using a first optical device 203, which in a particular embodiment consists of a pair of x,y movable galvanometer mirrors, but can also be a rotating polygon mirror based on light propagation in a nonlinear crystal, an acousto-optic deflector, or an electro-optic deflector, etc. Thus, a large area of ​​the sample 300 can be scanned quickly with the first optical device 203. In the proposed system, such an area can be, for example, 22 mm 2 Up to 2.25m 2 The total scanning time of such an area can be, for example, in the range of 0.1 ms to 1000 s.

[0075] In order to measure the color of a given area of ​​the sample 300, the scanning of the area is synchronized with the recording of the spectra of multiple parts of the area by the spectrometer 400, and the spectrum recording of each part lasts for a spectrum integration time equal to the scanning duration of the first optical device 203 of the part. As described above, the area is scanned part by part. For each part, the spectrometer 400 records a spectrum corresponding to the scattered light collected by the first optical device 203 during the time of scanning the part (that is, the spectrometer integration time of recording the spectrum matches the scanning time of the part). Preferably, the spectrometer 400 remains passive during the time (called the flight time) when the first optical device 203 moves to the first point of the next part to be scanned. When scanning the next part, the spectrometer 400 records a new spectrum, and so on, until each part of the scanned area has a corresponding spectrum recorded by the spectrometer 400.

[0076] Figure 2AA non-limiting example of the synchronization process between sample scanning and spectrum recording in an embodiment of the progressive scanning area is shown and is as follows: a square voltage signal (in Figure 2A The left side (upper) of the figure is represented as a time function) for synchronous scanning and spectrum recording time. The voltage signal is fed to the synchronization input port of the first optical device 203 and the synchronization input port of the spectrometer 400 at the same time. When the signal changes from the low state voltage V L becomes a high voltage V H When the rising trigger event occurs at time t, the first optical device 203 starts scanning and spectrum recording for one row at the same time. For each scanning row of any number n (from n=0 to n=N), the rising trigger event occurs at time t n During the high state of the signal (integration time T H ), the first optical device 203 is from point (x 0 ,y n ) to point (x 0 +L x ,y n ) scans a line on the sample, and the spectrometer 400 records the spectrum n, and the second optical device 500 is integrated for the time T H The light detection signal generated by all scattered light collected during the period is integrated. When the signal changes from a high voltage state to a low voltage state (falling trigger event), the first optical device 203 starts to move to translate the collimated light beam to the first point of the next row, and the spectrometer 400 stops spectrum recording. During the low state of the signal (flight time T L ), the first optical device 203 translates the collimated light beam to the first point of the next row, and the spectrometer 400 remains in a passive state. This process is repeated in sequence until all rows of the area from n=0 to n=N are scanned, and the spectrum n of each row n is recorded. A computing device operably connected to the spectrometer performs statistical calculations to calculate the overall spectrum using all or part of the spectra corresponding to all rows, and preferably, the computing device calculates an average spectrum by averaging all spectra corresponding to all rows.

[0077] Figure 2B An exemplary oscilloscope trace of a voltage signal used for synchronization between a galvanometer scanner and a spectrometer in an embodiment of the present invention is shown, where the integration time T H is 11.93 milliseconds, the flight time T L It is 571.3 microseconds.

[0078] In one embodiment, in order to calculate the color of the sample 300, it is necessary to measure: the spectrum of the scattered light from the sample 300, and the spectrum of the scattered light from the white reference. Therefore, in one embodiment, the above process is performed to obtain the average spectrum of the scattered light of an area of ​​the sample 300, and also to obtain the average spectrum of the scattered light of the white reference. Most preferably, the white reference is placed at the same distance from the system as the sample 300. Likewise, most preferably, the scanning area of ​​the white reference is the same size as the scanning area of ​​the sample. Preferably, the white reference is measured before measuring the sample.

[0079] Advantageously, the best accuracy of the color determination can be obtained in the preferred case of utilizing the full dynamic range of the spectrometer 400 when recording the spectra of the white reference and the sample 300. Such a full dynamic range can be obtained when the integration time of the spectrometer recording the spectrum is set equal to the maximum spectral integration time for which the spectrometer response and therefore the recorded spectrum is not saturated at any wavelength. In one embodiment of the proposed method, the maximum spectral integration time is determined before saturation as follows: The first optical device 203 is configured / programmed to continuously scan a portion of the area of ​​the white reference, preferably the periphery, similar to Figure 3A As shown. At the same time, the spectrometer 400 is configured / programmed to record spectra with different integration times, and the integration time increases gradually and discretely with a certain constant time difference. The maximum value among these integration times, that is, the corresponding recorded spectrum is not saturated at any wavelength, is set as the integration time for recording the reference spectrum and the sample spectrum, and is correspondingly set as the time of the synchronization signal between the scanner and the spectrometer at the high state voltage (integration time T H ), as described above and in Figure 2A Shown in.

[0080] This determination of the integration time is performed using a white reference object because the white reference object will scatter a higher proportion of the light intensity than the sample 300. Therefore, if the spectrometer 400 is not saturated by the scattered light from the white reference object, then the spectrometer 400 will not be saturated by the scattered light from the sample 300, provided that the integration time is the same in both cases.

[0081] The required integration time T is determined as described above H can be reduced with the brightness of the collimated beam. For example, the integration time T H It may be inversely proportional to the brightness of the collimated beam. For example, in one embodiment, for 1 mW / cm 2 The brightness of the collimated beam (the brightness consists of all wavelengths from 430 to 780 nm and is measured at a distance of 1 m from the collimator 205), the integration time T His 1622.48ms, for 136mW / cm 2 The brightness value, the integration time T H It is 11.93ms.

[0082] In one embodiment, the XYZ tristimulus values ​​are calculated by performing the following steps:

[0083] Step 1, measure the spectrum:

[0084] Measure the spectrum of the white reference area and obtain it through the above synchronization process.

[0085] Measure the spectrum of the background, at the integration time T determined as described above H The background is the noise recorded by the spectrometer, which is generated by the detected ambient light and / or the intrinsic electrical noise of the spectrometer. The background spectrum is recorded with the illumination collimated beam being turned off or blocked (e.g., using an optional electromechanical shutter in the system) at the point of the light source, or at a point between the light source and the sample, or at a point between the first optical device 203 and the light source.

[0086] The spectrum of the sample 300 area is measured and obtained by the above synchronization process. The area of ​​the sample and the white reference are equal and are placed at the same distance from the end of the light source.

[0087] Step 2, calculate the reflectivity curve of the sample 300 area: Here, the reflectivity curve R(λ) is considered as a spectrum, which represents the amount of light reflected by the sample 300 area at each wavelength λ in percentage (%), and the reflected light includes scattered light from the sample area and a specular reflection component reflected from the sample area (if / when the specular reflection component exists). The reflectivity curve of the sample 300 area is calculated by the computing device as follows:

[0088]

[0089] Wherein, W(λ) is the spectrum of the white reference area, I(λ) is the spectrum of the sample area, and B(λ) is the spectrum of the background. The measurement method is as described above and is expressed in the same units (e.g., spectrometer counts, optical power, or spectral power density, etc.).

[0090] Step 3: Calculate tristimulus values ​​X, Y, Z: Based on the reflectance curve of the area of ​​sample 300, the tristimulus values ​​X, Y and Z of the area of ​​sample 300 are calculated by a computing device using the following standard expressions established by CIE - International Commission on Illumination [Reference 4, Reference 5]:

[0091]

[0092] Wherein, S(λ) is the normalized spectrum of the CIE standard illuminant (ie, the theoretical spectrum of the standard illuminant type established by the CIE). Examples of the CIE standard illuminants include A-incandescent lamp, D65-daylight, and F2-fluorescent lamp. is the tristimulus spectral response of the CIE standard observer, representing the colors that ordinary people see in the visible spectrum. The different CIE standard responses are called 2° observer (CIE 1931) and 10° observer (CIE 1964). 1 and λ 2 They correspond to the first wavelength (preferably ranging from 370 to 460 nm) and the second wavelength (preferably ranging from 620 to 780 nm), respectively. k is a normalization constant.

[0093] The X, Y, and Z values ​​associated with the reflectivity of the white reference area (named X n , Y n , Z n ) is also calculated by the above equation using the same CIE standard illuminant and the same CIE standard observer, or can also be regarded as a given or predetermined property of a white reference object.

[0094] Step 4: Calculate the color coordinates in a color space, such as CIEXYZ, CIE L*a*b*; CIE L*Ch or HUNTER Lab, etc. For example, in the case where the space is CIE L*a*b*, the coordinates L*, a* and b* of the sample area are calculated by the computing device using the following expressions:

[0095] L * =116(Y / Y n ) 1 / 3 -16 (Equation 4a)

[0096] a * =500[(X / X n ) 1 / 3 -(Y / Y n ) 1 / 3 ](Equation 4b)

[0097] b * =200[(Y / Y n ) 1 / 3 -(Z / Z n ) 1 / 3 ](Equation 4c)

[0098] Some details of the example of the above-mentioned process of obtaining color coordinates of a textile sample area are as follows: The example relates to an embodiment in which the first optical device includes a collimator, a galvanometer mirror and an electromechanical shutter. In the example, the sample is illuminated by a collimated beam of a fiber supercontinuum light source, which simultaneously emits a wavelength band from 430 to 780 nm in the visible light range. In the example, the spectrum is recorded by a commercial spectrometer model OCEAN-HDX-VIS-NIR from OceanInsight. The following parameters are considered in the example: Area of ​​the sample: 10x10cm 2 ; Distance of sample from collimating lens: in the range of 0.95 to 1 m for all positions of the beam within the sample area; Visible spectrum range: 430-780 nm; Brightness of the collimated beam (composed of all wavelengths from 430 to 780 nm) at 1 m from the collimating lens: 136 mW / cm 2 ; Spectral integration time T H :11.93ms; Flight time T L : 0.57ms; number of scan lines: 50; total area scan time: 0.62s. In the same example, the computing device is configured to determine the color coordinates of the sample area for CIE standard illuminants A, B, D50, D65, F2; CIE standard 2° observer and 10° observer; standard color coordinate spaces CIEXYZ, CIEL*ab, CIEL*Ch, HUNTERLab; and determine the standard ASTM E313 whiteness and yellowness index;

[0099] In the example described, first, something like Figure 3A The perimeter of the white reference area of ​​the illuminated textile is shown in FIG. 1 and is used to determine the spectral integration time T. H , the value obtained is T H = 11.93ms. Next, in the same example, the area of ​​the white reference object is scanned line by line, similar to Figure 3B , where 7 of the total 50 rows are shown. The time to perform a complete scan of each row corresponds to an integration time T of 11.93 ms. H , and the flight time T L (The time it takes for the scanning galvanometer mirror to translate the collimated beam from the last point of one line to the first point of the next line) is 0.57ms. At the same time, in the same example, the spectrometer records the spectrum of each scanned line. Next, in this example, the illumination beam is blocked with an electromechanical shutter placed between the collimator and the galvanometer mirror, and a background spectrum is recorded. Next, similar to Figure 3C As shown, the area of ​​the textile sample for which color coordinates need to be acquired is scanned line by line.

[0100] In this example, the integration time TH , flight time T L The conditions of , number of rows, sample area and position of the sample relative to the end of the collimator and the galvanometer reflector are the same as those in the previous scanning process of the white reference. At the same time, in this example, the spectrometer records the spectrum of each scanned row. Next, in this example, the computing device calculates the average spectrum of 50 rows of the white reference and the average spectrum of 50 rows of the textile sample. Finally, according to the above equations 1 to 4a, 4b, 4c, in this example, the computing device calculates the reflectance curve and calculates the color coordinates of the sample area based on the reflectance curve.

[0101] In order to further evaluate the utility of the present invention for determining the color coordinates of a sample area made of arbitrary materials, the above procedure has been followed to calculate the color coordinates of a sample of an aluminum plate coated with a paint pigment, which is manufactured, for example, by coil coating technology. As an example, an aluminum plate coated with a green paint pigment was studied using the same measurement procedure as described above for the textile sample. In the example described for the aluminum sample, the following parameters were present: Sample area: 13x13mm 2 ; Distance between sample and collimating lens: in the range of 0.95 to 1 m for all positions of the beam within the sample area; Visible spectrum range: 420-750 nm; Spectral integration time T H :1.55ms; Flight time T L : 0.07ms; Number of rows: 6; Total area scanning time: 9.72ms. In this example, the first optical device and the second optical device of an embodiment of the present invention are galvanometer mirrors. The first galvanometer mirror (first optical device) scans the sample area by changing and dynamically adjusting the direction of the collimated light beam so that it scans the sample area around a central direction perpendicular to the sample surface (the incident angle θ is approximately 0°). The second galvanometer mirror (second optical device) receives scattered light from the surface at an observation angle α of approximately 45°, and, in synchronization with the first galvanometer mirror, redirects the received scattered light, and changes and dynamically adjusts the propagation direction of the redirected scattered light so that the propagation direction remains constant and parallel to the flat surface of the sample during scanning of the sample area. The redirected light is received by an off-axis parabolic mirror and focused into a multimode optical fiber, which guides the light to the input end of a spectrometer (similar to Fig. 7A and Figure 7B shown). Figure 8 The reflectance spectrum obtained from the process for measuring the coated aluminum sample is shown (curve A), and the theoretical reflectance spectrum provided by the sample manufacturer for an incident angle θ=0° and an observation angle α=45° (the standard geometry for measuring color, referred to in the art as 0 / 45) is also shown (curve B). Figure 8 In the figure, the reflectivity R (%) is shown as a function of the wavelength λ (nm). Figure 8As shown, the subsequent experimental process correctly measured the expected reflection spectrum of the sample with geometry 0 / 45. From the obtained reflection spectrum, the color coordinates of the aluminum sample area under investigation were calculated to be L*=37.88, a*=-53.39, b*=20.71 in the CI EL*a*b* color space for illuminant D50, 2° observer.

[0102] In some embodiments, the reference object spectrum can be a reference object overall spectrum. The latter is preferably calculated in a similar manner to the calculation method of the sample overall spectrum. Therefore, in one embodiment, the method for calculating the overall spectrum of the sample area is applied to the reference object sample, such as a white reference object sample, to calculate the overall reference object spectrum.

[0103] The practical method of the present invention for measuring the color of a sample area can be applied for a variety of purposes, such as quality inspection in a manufacturing process, development of coating materials, industrial sorting, inspection of materials for recycling or classification, etc. In a non-limiting example, the present invention is used to distinguish samples based on color differences. In the latter example, the color coordinates of two samples can be calculated in CI EL*a*b*, CI EL*Ch, and HUNTER Lab. The ASTM E313 yellowness parameters of two samples can also be calculated.

[0104] In particular, their color coordinates calculated in the CI EL*ab space can be located in a graphical representation of the CI EL*ab space (L*, a, b axes). In this example, the color difference between two samples can be represented by the values ​​of ΔL, Δa, Δb, and ΔE, where It should be clarified that the symbols of the parameters L*, a*, b* and ΔE* throughout this document may be equivalently referred to as L, a, b and ΔE, respectively (without the symbol *).

[0105] Figure 4 Figure 1 shows a graph of light scattered by a textile sample when the textile sample is illuminated by a collimated beam of a supercontinuum light source, similar to an embodiment of the present invention in which the first optical device comprises a collimator and the beam cross-sectional diameter (1 / e ) on the sample is 1 / 20 nm for all wavelengths from 430 to 780 nm. 2 ) is between 2.1 and 5.3 mm. In the same embodiment, for all positions of the light beam in the sample, the distance between the sample and the collimating lens is between 0.95 and 1 m.

[0106] exist Figure 4 From left to right in the figure: 1) The light beam is statically incident on a white reference textile sample; 2) The light beam is dynamically incident on the same white reference textile sample, at a time of 11.93ms (integration time T H) scans a line of 10 cm in length within the test area; 3) the light beam is statically incident on the textile sample under test (to obtain its color coordinates); 4) the light beam is dynamically incident on the same textile sample under test, within a time of 11.93 ms (integration time T H ) to scan a line 10 cm long.

[0107] about Figure 5 , which shows the working principles of many color measurement systems. It is well known that the color of a sample perceived by an observer may depend on the relative orientation between the illuminating light source, the sample, and the observer. The same sample illuminated by the same light source and viewed by the same observer may be perceived as a different color from one viewing to another if the angle of incidence and / or the angle of observation from a direction perpendicular to the sample changes from one viewing to another. This effect may be particularly valuable in the case of partially reflective samples, as the specular component of the light reflected by the sample may obscure the "true" color of the sample. Figure 5 This effect is illustrated by , where θ is the angle of incidence of the light (i.e. the angle formed between the propagation direction of the illumination light and the normal direction of the sample plane). The reflection angle of the specular component is equal to θ, while the scattered light from the sample propagates in all directions. The "true" color information of the sample is carried by the scattered light. Therefore, in order to perceive the "true" color of the sample, the observer should preferably move away from the direction of θ and move to an angle α (the observation angle relative to the direction of the specular component). The larger α is, the smaller the light intensity of the specular component received by the observer.

[0108] In previously known standard systems for measuring color, the illumination source and the observer are located at θ=0° and α=45°, respectively (0 / 45 configuration), in order to minimize the influence of the specular component. However, these previously known systems ignore important information about the color values ​​perceived at other observation angles, which is of great importance in different industrial fields (such as automotive). Systems that are able to measure color at different observation angles are called "multi-angle". In known multi-angle systems for measuring color, the number of observation angles is discrete and limited, and they require multiple illumination sources placed at different positions and multiple receivers placed at different positions. In addition, the illuminated area in known systems is only a few square centimeters.

[0109] Fig. 6A An embodiment of the present invention is shown for illustrative purposes. Fig. 6A In FIG. 5 , the first optical device 203 and the second optical device 503 are both galvanometer mirrors (galvanometers), and their rotation axes are parallel to each other. Therefore, the propagation direction of the collimated light beam and the propagation direction of the scattered light received by the optical element 504 are located on the same plane. Fig. 6AIn the embodiment of the present invention, the surface of the sample 300 is flat and parallel to the straight line between the rotation axes of the galvanometer mirrors. Fig. 6A , the propagation direction of the redirected scattered light received by the optical element 504 from the second galvanometer mirror 503 is parallel to the sample surface (sample plane). The present invention can achieve that this direction remains constant when the first galvanometer 203 scans the sample. Therefore, when the first galvanometer rotates to scan the sample, the second galvanometer can rotate to keep the direction constant. Fig. 6A The relative angle geometry between the mirrors is shown to keep the direction constant and parallel to the sample surface. Figure 5 As shown, θ is the incident angle of the light, which is determined by the rotation angle of the first galvanometer mirror. The reflection angle of the specular component is equal to θ, and α is the observation angle relative to the direction of the specular component. When θ changes, the illumination point in the sample also changes. Therefore, α, which is determined by the fixed position of the second mirror, changes accordingly. Fig. 6A , if γ is the rotation angle of the second galvanometer relative to the straight line between the rotation axes of the plurality of galvanometer mirrors, then, in order to keep the propagation direction of the redirected scattered light received by the optical element parallel to the surface, θ, α and γ should maintain the following angular relationship: θ+α+2γ=90°. Fig. 6A In an embodiment, the second galvanometer mirror is synchronized with the first galvanometer mirror to maintain the angular relationship during scanning of the sample area to measure its color coordinates.

[0110] Figure 6B Shown with Fig. 6A An embodiment similar to the embodiment of Figure 6B In the figure, the incident angle θ of the light is 0°, and the observation angle relative to the direction of the specular reflection component α is 45°. Figure 6B The embodiment of is a preferred embodiment because using it, the color coordinates of the sample area can be calculated according to a geometric configuration called 0 / 45, which is a standard geometric configuration widely accepted by the industry and users of color measurement instruments.

[0111] like Fig. 6A and Figure 6B As shown, compared with the prior art instruments for measuring the color of the sample area, the present invention brings the advantage that the observer (spectrometer) can be kept in a fixed position relative to the position of the optical element and the position of the light source output when the illumination angle θ and the observer angle α vary over time. Remaining in the fixed position, the observer (spectrometer) can always receive the scattered light from the sample in the same receiving direction. Therefore, the scattered light received by the observer / spectrometer to determine the color of the sample can always be received by the observer / spectrometer in the same receiving direction.

[0112] Therefore, the system of the present invention for measuring the color of a sample area can advantageously be a multi-angle system that can provide a large number of illumination angles and observation angles, preferably the angles vary continuously, and more preferably use a single illumination light source placed at a fixed single position and a single receiver (preferably a spectrometer) placed at a fixed single position.

[0113] Fig. 7A Another preferred embodiment is shown, which is similar to Fig. 6A In the embodiment of Fig. 7A In the embodiment of , the optical element 504 is an off-axis parabolic mirror, and the propagation direction of the scattered light redirected by the second galvanometer reflector is parallel to the main optical axis of the off-axis parabolic mirror. In addition, the scattered light received by the off-axis parabolic mirror is focused by the off-axis parabolic mirror to the input end of the optical fiber 600, and the optical fiber 600 can preferably be a multimode optical fiber. Fig. 7A In the embodiment of the present invention, the optical fiber 600 is fixed at a specific position, and the specific position does not need to be changed when the illumination angle θ and the observation angle α change. The optical fiber 600 transmits the focused light to the input end of the spectrometer 400. In a non-limiting example, the system is similar to Fig. 7A The system shown, and some details of the example are as follows: the optical element is a 90° off-axis parabolic mirror MPD149-M01 from Thor l abs GmbH, with a diameter of 25.4 mm and a reflection focal length of 101.6 mm; the optical fiber is a multimode optical fiber QP600-2-VIS-NI R from Ocean Optics Inc, with a core diameter of 600 um; the spectrometer is an OCEAN-HDX-VIS-NI R spectrometer from Ocean Optics Inc; the galvanometer mirror is a galvanometer mirror of the SCANLAB 7mm Scan Kit AIO model from SCANLAB GmbH, with a scanning range of ±0.42 rad.

[0114] Figure 7B Shows Fig. 7A A variation of the configuration of the embodiment. Figure 7B In the embodiment of the invention, the off-axis parabolic mirror has a through hole coaxial with the main optical axis of the parabolic mirror and includes a laser pointer 700 therein. Figure 7B In an embodiment of the present invention, the light beam of the laser pointer 700 propagates through the coaxial hole in a direction opposite to the propagation direction of the scattered light redirected by the second galvanometer. Figure 7B In the embodiment of the invention, the function of the laser pointer is to control the rotation angle γ of the second galvanometer reflector so as to achieve the condition that the scattered light redirected by the second galvanometer is always parallel to the main optical axis of the off-axis parabolic mirror. Figure 7BAs shown, since the beam of the laser pointer propagates through the same optical path as the redirected scattered light, but in the opposite direction, the condition occurs when the beam of the laser pointer points to the incident point of the collimated beam of the light source on the sample. In a non-limiting example, the off-axis parabolic mirror is a 90° off-axis parabolic mirror MPD249H-M01 from Sorebo LLC, with a diameter of 50.8 mm and a reflection focal length of 101.6 mm.

[0115] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.

[0116] For example, other aspects may be implemented by hardware or software or a combination of hardware and software.

[0117] In addition, the software program included as part of the present invention may be embodied in a computer program product, which includes a computer-readable medium, such as a readable storage device having computer-readable program code segments stored thereon, such as a hard drive device, a flash memory device, a CD-ROM, a DVD / ROM, or a computer disk.

[0118] The computer readable medium may also include an optical, wired or wireless communication link on which the program code segments are carried as digital or analog signals.

[0119] The scope of the invention is defined in the appended claims.

[0120] Non-patent references:

[0121] [Reference 1] CK Hitzenberger, M. Danner, W. Drexler and AF Ferrcher, "Measurement of spatial coherence of superluminescent diodes," Journal of Modern Optics, 46:12, 1763-1774 (1999).

[0122] [Reference 2] K. Saastamoinen, J. Tervo, J. Turunen, P. Vahimaa, and A.T. Friberg, “Spatial coherence measurement of polychromatic light using a modified Young interferometer,” Optics Express, 21: 4, 4061-4071 (2013).

[0123] [Reference 3] ISO Standard 11146, “Laser and laser-related equipment – ​​Test methods for laser beam width, divergence angle and beam spread ratio” (2005).

[0124] [Reference 4] Retrieved from the website: http: / / cie.co.at / publications / colorimetry-part-3-cie-tr is imu l us-va l ues-2 , Colorimetry - Part 3: CIE tristimulus values, ISO / CIE 11664-3:2019(E).

[0125] [Reference 5] Excerpted from the website: https: / / en.wikipedia.org / wiki / CI E_1931_co lor_ space , CI E1931 color space, article in Wikipedia.

Claims

1. A system for measuring the color of a sample area, comprising: a light source (100) configured to emit light to illuminate the sample (300); a first optical device (200) configured to receive the light to output a collimated beam of the light and direct it to a surface of the sample (300) located at a given distance, the first optical device (200) comprising a first optical device (203) configured to change and dynamically adjust the direction of the collimated beam toward the sample (300) so as to scan an area of ​​the sample (300) part by part; a second optical device (500) configured to collect light scattered from the sample when the collimated light beam is irradiated on the sample, the second optical device (500) comprising a second optical apparatus (503) and an optical element (504), wherein the second optical apparatus (503) is configured to receive light scattered by the sample, the scattered light being scattered at an observation angle α relative to a direction of a specular reflection component reflected from the sample when the collimated light beam is incident on a surface of the sample, and the second optical apparatus (503) is further configured to redirect the received scattered light to the optical element (504), and wherein the second optical device (503) is further configured to synchronously change and dynamically adjust the propagation direction of the redirected scattered light with the first optical device (203), so that during scanning of an area of ​​the sample (300), the propagation direction of the redirected scattered light remains unchanged relative to the optical element (504); a spectrometer (400) configured to receive the scattered light collected by the second optical device (500) and record a spectrum of the scattered light collected by each portion; and a computing device operably connected to the spectrometer (400); in: The light emitted by the light source (100) includes a spectrum of wavelengths emitted simultaneously, and the spectrum continuously covers at least one wavelength band from a first wavelength to a second wavelength in the visible light range; The light emitted by the light source (100) is spatially coherent at least for all wavelength bands from the first wavelength to the second wavelength; The first optical device (200) for outputting the collimated light beam is configured to maintain the spatially coherent light in collimated form if the spatially coherent light is collimated, or the optical device (200) further comprises a collimator (205) for performing collimation of the spatially coherent light; The system is configured to synchronize the scanning of the region with the recording of the spectrum of each portion of the region by the spectrometer (400) when the first optical device (203) scans the region, and the spectrum integration time for recording the spectrum of each portion is equal to the duration of the scanning of the portion by the first optical device (203); The computing device is configured to calculate an overall spectrum by statistically calculating all or some of the spectra corresponding to all or some of the scanned portions of the region, and to determine the color coordinates of the sample (300) region in a given color space by analyzing the overall spectrum, wherein the analysis includes calculating XYZ tristimulus values ​​corresponding to the overall spectrum; And wherein the first wavelength is included in the range between 370nm and 460nm, and the second wavelength is included in the range between 620nm and 780nm.

2. The system according to claim 1, wherein: The propagation direction of the redirected scattered light is parallel to the main optical axis of the optical element (504). Preferably, the optical element (504) is an off-axis parabolic mirror.

3. A system according to any one of the preceding claims, wherein: The observation angle α is approximately 45 degrees, and wherein the first optical device (203) is further configured to change and dynamically adjust the direction of the collimated light beam during a portion-by-portion scan of the sample area so that it is oriented around a central direction perpendicular to the surface of the sample.

4. A system according to any one of the preceding claims, wherein: The first optical device (203) and the second optical device (503) include respective galvanometer mirrors; the second optical device also includes an optical fiber optically coupled to the spectrometer (400); and the optical element (504) is configured to receive scattered light redirected by the first optical device (503) and further redirect it to the input end of the optical fiber.

5. A system according to any one of the preceding claims, wherein: The optical element (504) is an off-axis parabolic mirror with a through hole, and the system further comprises a laser configured to emit laser light through the hole toward the second optical device (503).

6. A system according to any one of the preceding claims, wherein: The light source is a supercontinuum light source.

7. A system according to any one of the preceding claims, wherein: For all wavelengths from the first wavelength to the second wavelength, the diameter of the cross section of the collimated light beam is 10 mm or less at any distance of 1 m or less from the first optical device (200), or 100 mm or less at any distance of 10 m or less from the first optical device (200), the diameter being considered to be 1 / e 2 width, when the first optical device (200) includes the collimator (205), the point is preferably located at the collimator (205).

8. A system according to any one of the preceding claims, wherein: The brightness of the collimated light beam composed of all wavelengths from the first wavelength to the second wavelength is 1 mW / cm at any distance of 1 m from the first optical device (200) or less. 2 or higher, or 0.01 mW / cm at any distance of 10 m or less from the first optical device (200) 2 Or higher, when the first optical device (200) comprises the collimator (205), the point is preferably located at the collimator (205).

9. A method for measuring the color of a sample area, comprising: emitting light using a light source for illuminating a sample located at a given distance from the light source, the light comprising a spectrum of wavelengths emitted simultaneously, wherein the spectrum continuously covers at least a wavelength band from a first wavelength to a second wavelength in the visible light range, the light is spatially coherent at least at all wavelengths from the first wavelength to the second wavelength, and wherein the first wavelength is contained in a range between 370 nm and 460 nm, and the second wavelength is contained in a range between 620 nm and 780 nm; receiving spatially coherent light at a first optical device at a distance from one end of the light source; At the first optical device, if the spatially coherent light is collimated, maintaining the spatially coherent light in collimated form, or collimating the spatially coherent light with a collimator; Outputting and directing the collimated beam of spatially coherent light to the surface of the sample at a given distance from the first optical device through the first optical device, the distance preferably being 0.5 m or more; scanning the sample area section by section through the first optical device of the first optical device, changing and dynamically adjusting the direction of the collimated beam; collecting light scattered from the sample by a second optical arrangement, the second optical arrangement comprising a second optical device and an optical element, wherein light scattered by the sample is received by the second optical device, the scattered light being scattered at an observation angle relative to a direction of a specular reflection component reflected from the sample when the collimated light beam is incident on a surface of the sample, and redirecting the received scattered light to the optical element by the second optical device, and changing and dynamically directing a propagation direction of the redirected scattered light during scanning of the sample area by the second optical device in synchronization with the first optical device, such that the propagation direction of the redirected scattered light remains unchanged relative to the optical element; recording, by a spectrometer, a spectrum of scattered light collected from each portion of the sample; synchronizing the scanning of the area with the recording of spectra of portions of the area by the spectrometer, wherein the spectrum of each portion is recorded for a spectral integration time equal to the duration of the scanning of the portion by the first optical device; and The color coordinates of the sample area in a given color space are measured by calculating an overall spectrum by performing statistical calculations on all or some of the spectra corresponding to all or some of the scanned portions of the area through a computing device operably connected to the spectrometer, and by analyzing the overall spectrum, wherein the analysis includes calculating XYZ tristimulus values ​​corresponding to the overall spectrum.

10. The method according to claim 9, wherein: The synchronization is performed using a time-dependent voltage signal.

11. The method according to claim 9 or 10, wherein: When the sample is illuminated with the collimated light beam, the sample also receives other light from the environment.

12. The method according to any one of the preceding claims 9 to 11, wherein: The collimated light beam has a maximum full-angle divergence angle of 0.46 degrees or less, preferably between 0.01 and 0.20 degrees, for all wavelengths from the first wavelength to the second wavelength; or For all wavelengths from the first wavelength to the second wavelength, the diameter of the cross section of the collimated beam is 10 mm or less at any distance from a point 1 m or less from the first optical device, or is 100 mm or less at any distance from a point 10 m or less from the first optical device, the diameter being considered to be 1 / e 2 width; or For all wavelengths from the first wavelength to the second wavelength, the beam quality factor M of the collimated beam is 2 is between 1.0 and 2.0; or The brightness of the collimated light beam composed of all wavelengths from the first wavelength to the second wavelength is 1 mW / cm at any distance of 1 m from the first optical device or less. 2 or higher, or 0.01 mW / cm at any distance of 10 m or less from the first optical device (200) 2 or higher; And wherein, when the first optical device includes the collimator, the point on the first optical device is located at the collimator.

13. The method according to any one of the preceding claims 9 to 12, wherein: The spectral integration time is determined by performing the following steps: continuously scanning a portion of the area, preferably the periphery, of the white reference object by means of said first optical device; While scanning the portion, recording, by a spectrometer, spectra with different spectral integration times, the spectral integration times increasing gradually and discretely with a certain constant time difference; and The maximum spectral integration time for which the spectrum is not saturated at any wavelength recording is selected as the spectral integration time.

14. A method according to any one of the preceding claims 9 to 13, wherein: The XYZ tristimulus values ​​are calculated in the following way: calculating a reflectance curve using an overall spectrum of the sample area, an overall spectrum of a reference object of a white reference object, and a background spectrum; The calculated reflectance curve is multiplied by the CIE standard illuminant spectral curve, the CIE standard observer spectral curve and a normalization constant.

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