Non-contact glossiness measuring device and method based on imaging technology

Abstract

The invention provides a non-contact glossiness measuring device based on an imaging technology, and the device comprises a housing, a top cover of the housing is provided with a measuring window, and a measuring region is located above the measuring window; the illumination light source is arranged in the shell, is positioned on one side of the measurement window, and is used for irradiating the measurement area at an incident angle theta 1; the gray level camera is installed in the shell, located on the other side of the measurement window and used for receiving light reflected from the measurement area at a reflection angle theta 2 for gray level imaging and obtaining a glossiness value according to a gray level value; the incidence field angle of the illumination light source in the measurement plane relative to the center of the measurement area is alpha '1, the incidence field angle perpendicular to the measurement plane is beta' 1, the reflection field angle of the gray scale camera in the measurement plane relative to the center of the measurement area is alpha '2, the reflection field angle perpendicular to the measurement plane is beta' 2, theta 1 = theta 2, and theta 1 = theta 2. Alpha '1gt; alpha '2, beta' 1gt; beta '2.

Description

Technical Field

[0001] This application relates to the field of optical detection technology, and specifically relates to a non-contact gloss measurement device based on imaging technology. Background Art

[0002] A glossmeter, also called a gloss meter, is a measurement device used to measure the gloss of the surfaces of materials such as ceramics, paints, inks, plastics, marble, aluminum, electroplating, and hardware.

[0003] Traditional gloss measurement devices measure the gloss of a sample using the principle of light reflection, that is, irradiating the sample under the conditions of a specified incident angle and a specified light beam to obtain a light beam in the direction of the specular reflection angle. A glossmeter usually consists of a light source, a lens, a receiver, a display instrument, etc.

[0004] However, most of the gloss measurement devices for measuring the gloss of products on the market currently are contact type, and for some special scenarios, contact measurement is not applicable and will cause damage to the product. At the same time, due to the limitation of the size of the measurement spot, the measurement area covers at least several square millimeters, and it is impossible to measure the gloss of samples smaller than the size of the spot.

[0005] To solve the above problems, this application designs a non-contact gloss measurement device and method based on imaging technology. Summary of the Invention

[0006] Aiming at the deficiencies in the prior art, the purpose of this application is to provide a non-contact gloss measurement device and method based on imaging technology, which can realize non-contact measurement of the gloss of a sample and can also realize measurement of small-sized samples.

[0007] The first aspect of this application discloses a non-contact gloss measurement device based on imaging technology, including: a housing, a measurement window is opened on the top cover of the housing, and the measurement area is located above the measurement window; an illumination light source, the illumination light source is installed inside the housing, on one side of the measurement window, and is used to irradiate the measurement area at an incident angle θ 1 ; a grayscale camera, the grayscale camera is installed inside the housing, on the other side of the measurement window, and is used to receive the light reflected from the measurement area for grayscale imaging, measure the grayscale value, and obtain the gloss value according to the grayscale value; the optical axis of the illumination light source and the optical axis of the grayscale camera intersect at the center of the measurement area, and the incident angular spread of the illumination light source relative to the center of the measurement area in the measurement plane is α′ 2 ; the incident angular spread perpendicular to the measurement plane is β′ 1 ; the reflected angular spread of the grayscale camera relative to the center of the measurement area in the measurement plane is α′ 1 ​2 The reflection opening angle perpendicular to the measurement plane is β′ 2 , where θ 1 = θ 2 , α′ 1 > α′ 2 , β′ 1 > β′ 2 .

[0008] According to the glossiness measurement device of the present application, the measurement area is located above the measurement window, enabling non-contact measurement of the sample to be measured, avoiding contact between the surface of the sample to be measured and the measurement device, and thus preventing damage to the surface of the sample to be measured. In addition, based on imaging technology for glossiness measurement, the gray value of each pixel can be calculated one by one through a grayscale camera. In theory, the glossiness of an area corresponding to the size of one pixel can be measured, enabling measurement of small-sized samples. Moreover, according to the technical solution of the present application, the incident opening angle of the illumination light source is greater than the reflection opening angle of the grayscale camera. On the one hand, it increases the illumination solid angle of the illumination light source, enabling glossiness measurement over a larger range. On the other hand, it reduces the reflection opening angle of the grayscale camera, enabling the use of a photosensitive device with a smaller photosensitive area for grayscale imaging, which can reduce costs.

[0009] In the first aspect of the present application, α′ 1 , α′ 2 , β′ 1 and β′ 2 are set such that the measurement optical path of the glossiness measurement device is a reverse optical path conforming to the international standard ISO2813:2014. According to the principle of reversibility of the optical path, the glossiness measurement device of the present application still meets the measurement requirements of the international standard ISO2813:2014, has a very high degree of matching with the international standard, high glossiness measurement accuracy, and good consistency.

[0010] In the first aspect of the present application, the illumination light source is a uniform illumination system. The light exit of the uniform illumination system is rectangular, and the size of the light exit and the distance from the light exit to the center of the measurement area are set such that the incident opening angle of the illumination light source relative to the center of the measurement area in the measurement plane is α′ 1 and the incident opening angle perpendicular to the measurement plane is β′ 1 .

[0011] In the first aspect of the present application, the uniform illumination system is an integrating sphere light source.

[0012] In the first aspect of the present application, the light-emitting element of the uniform illumination system is any one or a combination of a xenon lamp, a halogen lamp, a white LED, or a color LED.

[0013] The uniform lighting system can provide uniform lighting within the entire illuminated area, thereby improving the accuracy of gloss measurement.

[0014] In the first aspect of the present application, the light-emitting element of the uniform lighting system is a white LED whose spectral power distribution conforms to the international standard ISO2813:2014.

[0015] In the first aspect of the present application, the grayscale camera has a field stop, and the size of the field stop and the distance from the field stop to the center of the measurement area are set such that the reflection angle of the grayscale camera with respect to the center of the measurement area in the measurement plane is α′ 2 and the reflection angle perpendicular to the measurement plane is β′ 2 .

[0016] In the first aspect of the present application, the gloss measurement device further includes a filter, which is disposed in the measurement optical path of the gloss measurement device and is used to trim the spectral power distribution to conform to the international standard ISO2813:2014.

[0017] By using a light-emitting element whose spectral power distribution conforms to the international standard, or by using a filter in the measurement optical path to trim the spectral power distribution to conform to the international standard, the measurement device can be made to match the international standard, improving the accuracy and consistency of gloss measurement.

[0018] In the first aspect of the present application, a grayscale monitoring board is provided on at least one side of the measurement window, at least a part of the grayscale monitoring board is located within the shooting area of the grayscale camera, and the grayscale monitoring board is used to monitor and calibrate the measured grayscale value. The grayscale monitoring board can be used to monitor in real time the change in the measured value caused by the jitter of the illumination light source and perform real-time calibration, thereby improving the accuracy of gloss measurement.

[0019] In the first aspect of the present application, θ 1 = θ 2 = 20°, or θ 1 = θ 2 = 60°, or θ 1 = θ 2 = 85°. The gloss measurement device of the present application can adjust the angles of the incident angle and the reflection angle, thereby realizing the gloss measurement of different samples such as high gloss, medium gloss, and low gloss.

[0020] The second aspect of the present application provides a non-contact gloss measurement method based on imaging technology, which is measured by using the gloss measurement device described above. At least one target sub-region is selected within the measurement region through the control software, and the average gloss value of the target sub-region is calculated according to the gray value of each pixel within the target sub-region.

[0021] In the second aspect of the present application, the gloss measurement method further includes monitoring and calibrating the measured gray value by using a gray monitoring board.

[0022] The non-contact gloss measurement device and method based on imaging technology of the present application can obtain the gloss measurement of each pixel of the complete whole picture. At the same time, by adjusting multiple groups of illumination light sources and gray cameras, the gloss measurement of the sample at multiple angles can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram for gloss measurement of different types of samples to be measured with high gloss, medium gloss and low gloss at different incident angles according to the international standard ISO 2813:2014;

[0024] Figure 2 It is a schematic structural diagram of an embodiment of the gloss measurement device according to the present application;

[0025] Figure 3 It is a schematic diagram of the gloss measurement principle of the convergent light path according to the international standard;

[0026] Figure 4 It is a user interface of the control software of the gloss measurement device according to the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The following further describes the present application in conjunction with specific embodiments and the accompanying drawings. It can be understood that the illustrative embodiments of the present disclosure are only for explaining the present application, rather than limiting the present application. In addition, for the convenience of description, only the parts related to the present application rather than all the structures or processes are shown in the drawings.

[0028] The following specific embodiments illustrate the implementation manners of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Although the description of the present application will be introduced in conjunction with preferred embodiments, this does not mean that the features of this invention are limited to this implementation manner. On the contrary, the purpose of introducing the invention in conjunction with the implementation manner is to cover other alternatives or modifications that may be extended based on the claims of the present application. In order to provide a deep understanding of the present application, many specific details will be included in the following description. The present application may also be implemented without using these details. In addition, in order to avoid confusing or obscuring the key points of the present application, some specific details will be omitted in the description. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0029] Unless otherwise specified in the context, the terms "comprise", "have" and "include" are synonyms. The phrase "A / B" means "A or B". The phrase "A and / or B" means "(A and B) or (A or B)".

[0030] It should be understood that although the terms "first", "second", etc. may be used herein to describe various components, units or data, these components, units or data should not be limited by these terms. These terms are only used to distinguish one feature from another. For example, without departing from the scope of the exemplary embodiments, the first feature may be referred to as the second feature, and similarly the second feature may be referred to as the first feature.

[0031] It should be understood that although the directional terms such as "upper", "lower", "left", "right", etc. may be used herein to describe the positional relationship between various components, these directional terms are only for convenience of understanding to represent the directions in the drawings and cannot be used to limit the protection scope of the present application.

[0032] It should be noted that in this specification, similar reference numerals and letters indicate similar items in the drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0033] To make the purpose, technical solutions and advantages of the present application clearer, the implementation manners of the present application will be further described in detail below with reference to the drawings.

[0034] Such as Figure 1As shown, according to the international standard ISO 2813:2014 for measuring glossiness, the illumination light source of the glossiness measuring device measures the glossiness of different types of samples to be measured with high glossiness, medium glossiness, and low glossiness at different incident angles. Among them, when the incident angle is 20°, it is used to measure the glossiness of the high-glossiness sample to be measured; when the incident angle is 60°, it is used to measure the glossiness of the medium-glossiness sample to be measured; when the incident angle is 85°, it is used to measure the glossiness of the low-glossiness sample to be measured.

[0035] Figure 2 FIG. is a schematic structural diagram of an embodiment of the glossiness measuring device according to the present application, where Figure 2 the upper figure in FIG. is the front view of the glossiness measuring device with the front cover of the housing removed, Figure 2 and the lower figure in FIG. is the side view of the glossiness measuring device.

[0036] As Figure 2 shown, the glossiness measuring device includes a housing 1, an illumination light source 2, and a grayscale camera 3. A sample placement area for placing the sample to be measured 4 is provided on the upper surface of the housing 1, and a measurement window 5 is opened on the top cover of the housing 1. The measurement area (not shown) is located above the measurement window 5, and the optical axes of the illumination light source 2 and the grayscale camera 3 intersect at the center of the measurement area. Here, the measurement area being located above the measurement window 5 means that the measurement area can be understood as a planar area, the plane where it is located is above the measurement window 5 and parallel to the plane where the measurement window 5 is located, and the optical axes of the illumination light source 2 and the grayscale camera 3 intersect at the center of the measurement area, so as to achieve the non-contact measurement specifically described below. Although the measurement area can be understood as a planar area, those skilled in the art should be able to easily understand that the grayscale camera 3 has a certain depth of field, so within the depth of field of the grayscale camera 3, clear grayscale imaging can be performed.

[0037] The illumination light source 2 is installed inside the housing 1, on the left side of the measurement window 5, and is used to irradiate the measurement area at an incident angle θ 1 (not shown), where the incident angle θ 1 is the angle between the optical axis direction of the illumination light source 2 and the normal direction of the plane where the measurement window 5 is located.

[0038] The grayscale camera 3 is installed inside the housing 1, on the right side of the measurement window 5, and is used to receive the light reflected from the measurement area at a reflection angle θ 2 (not shown) for grayscale imaging, measure the grayscale value, and obtain the glossiness value according to the grayscale value, where the reflection angle θ 2 is the angle between the optical axis direction of the grayscale camera 3 and the plane where the measurement window 5 is located. According to the principle of optical specular reflection, it can be known that θ 1 =θ2 。

[0039] This application provides a non-contact glossiness measurement device based on imaging technology. In the art, if the distance between the surface of the sample to be measured and the surface of the measurement device is 0, it is a contact measurement. If the distance between the surface of the sample to be measured and the surface of the measurement device is greater than 0, that is, the sample to be measured can be separated from the surface of the measurement device, it is a non-contact measurement. Since in the industrial production process, contact measurement may cause wear on the surface of the sample to be measured, non-contact measurement is more preferable. However, when the glossiness measurement device uses integral measurement or in the case of a relatively large measurement range, when using non-contact measurement, the ambient light will leak into or contaminate the measurement range, resulting in deviation of the glossiness measurement result. As Figure 2 shown, this application adopts a non-contact technical solution based on imaging technology. The optical axis of the illumination light source 2 intersects with the optical axis of the grayscale camera 3 at a position 0-10 mm above the measurement window 5, preferably at 2 mm, so as to realize non-contact measurement. According to the non-contact glossiness measurement device based on imaging technology of this application, even if there is light source leakage in the non-measurement area, it will not affect the numerical value in the measurement area. Moreover, the glossiness measurement technical solution based on imaging technology is not limited by the spot size of the measurement beam, and can measure the glossiness of the sample surface area much smaller than the spot size.

[0040] The glossiness of the surface of the sample to be measured will directly affect the intensity of its reflected light. When the glossiness of the surface of the sample to be measured is high, it means that its light reflection ability is strong, and a higher grayscale value will be presented on the image. This is because a high-gloss surface can more effectively reflect the incident light into the camera or imaging device, thus forming a brighter area in the image. On the contrary, the surface with low glossiness has a weak ability to reflect light, and the grayscale value in the image is relatively low.

[0041] In an ideal situation, it can be assumed that there is a simple linear relationship between the glossiness value G and the image grayscale value I, that is, G = k × I, where k is a proportionality coefficient. This coefficient k can be determined by calibrating a standard sample with a known glossiness. For example, a standard sample with a known glossiness value can be used, its image can be taken and the corresponding grayscale value can be obtained, and then the value of k can be calculated through the above linear formula. After that, for other samples to be measured, this k value can be used to convert their image grayscale values into glossiness values. However, in practical applications, due to the influence of factors such as the roughness, color, and ambient light of the surface of the sample to be measured, the relationship between the grayscale value and the glossiness may be non-linear.

[0042] In this application, the grayscale value is converted into the glossiness value according to the following calibration method. With the incident angle and the reflection angle θ 1 = θ 2Taking 60° as an example, at least three standard samples are obtained. The glossiness values of these standard samples at an incident angle of 60° are known. For example, the three standard samples have high glossiness, medium glossiness, and low glossiness respectively. Set the incident angle θ of the illumination light source 2 of the glossiness measuring device of the present application 1 and the reflection angle θ of the grayscale camera 3 2 to 60°. Use the glossiness measuring device to image the three standard samples respectively to obtain the corresponding grayscale values. For a 12-bit grayscale camera, the range of its grayscale values is 0 to 4095. As shown in Table 1 below: Standard sample 1 is a low-glossiness sample, and its known glossiness value I is 12.4. The grayscale value G obtained by imaging it with the glossiness measuring device is 257.439; Standard sample 2 is a medium-glossiness sample, and its known glossiness value I is 57.2. The grayscale value G obtained by imaging it with the glossiness measuring device is 1130.09; Standard sample 3 is a high-glossiness sample, and its known glossiness value I is 97.7. The grayscale value G obtained by imaging it with the glossiness measuring device is 1990.32.

[0043] Table 1

[0044] Gray value G Glossiness value I Standard sample 1 257.439 12.4 Standard sample 2 1130.09 57.2 Standard sample 3 1990.32 97.7

[0045] Using the above data, through the fitting method, the grayscale value and the glossiness value can form a mapping relationship, thereby completing the calibration of the glossiness measuring device. In addition, more data can be used to obtain a more accurate mapping relationship. For example, more standard samples can be used, such as four, five, six, or more. The fitting methods can include linear regression method, polynomial regression method, piecewise linear regression method, spline interpolation method, locally weighted regression method, etc. For example, when the data shows a single linear trend, the linear regression method can be used, and the obtained mapping relationship is I = aG + b, where a is the proportional coefficient and b is the bias constant; when the data shows a non-linear but smooth change trend (such as quadratic, cubic curves), the polynomial regression method can be used, and the obtained mapping relationship is I = a 0 + a 1 G + a 2 G 2 + … + a n G n where a nDenote the n-th order coefficient; when the data shows different linear trends in different intervals (such as different change rates in low / high gloss regions), the piecewise linear regression method can be used to divide the data into multiple intervals, and an independent linear model is fitted for each interval; if a continuous and smooth curve is required to avoid the mutation of piecewise linearity, the spline interpolation method can be used, using piecewise polynomials and keeping smooth and continuous at the nodes; when the data shows a complex non-linear relationship, local weighted regression can be used to perform local polynomial fitting on each data point, and the weight decays with distance.

[0046] In addition, the above describes the calibration process of the gloss measurement device with the incident angle and the reflection angle θ 1 = θ 2 = 60° as an example. Those skilled in the art can easily think of calibrating the gloss measurement device accordingly by using the known gloss values of the standard sample at an incident angle of 20° or 85°.

[0047] Since during the use of the gloss measurement device, the measured gray value G will change with the aging of the measurement device, it is necessary to regularly calibrate the gloss measurement device at regular intervals during daily use, such as every day, every two days or every week. A black optical glass with high uniformity and high gloss is used as the high-gloss calibration plate, and the factory G-I numerical pair of this high-gloss calibration plate is known. When calibrating, use the gloss measurement device to measure the high-gloss calibration plate to obtain the gray value G 1 , according to the factory gray value G of this high-gloss calibration plate 0 , the calibration coefficient K = G 0 / G 1 can be calculated. Then, within this calibration period, all the measured gray values need to be multiplied by this calibration coefficient K to obtain a calibrated gray value.

[0048] Preferably, in addition to the high-gloss calibration plate, a medium-gloss calibration plate and a low-gloss calibration plate can also be used to calibrate the gray value of the measurement device.

[0049] During the calibration period, the measured gray value may also be subject to measurement deviations due to reasons such as the jitter of the illumination light source, such as the decrease in light intensity caused by the thermal effect as the temperature rises. To eliminate these measurement deviations, as Figure 2 shown, gray value monitoring plates 6 are also provided on the left and right sides of the measurement window 5 in the gloss measurement device. At least a part of the gray value monitoring plates 6 is located within the shooting area of the gray value camera 3 and can be gray-imaged by the gray value camera 3 and its gray value can be measured. The gray value monitoring plates 6 are optical black glasses with high uniformity and high gloss. At the time points of the above regular calibration, while calibrating with the standard plate, the gray value G of the gray value monitoring plates 6 at this moment is also recorded.0 ', and within this calibration period, during each measurement or at regular intervals (such as every 1 minute, every 5 minutes, or every 10 minutes, etc.), the grayscale camera 3 measures the grayscale value of the grayscale monitoring board 6 to obtain the grayscale value G 1 ', and uses the linear coefficient K' = G 0 ' / G 1 ' to perform real-time correction on the measured grayscale value of the sample to be measured. The grayscale monitoring board 6 is arranged on the inner wall of the top cover of the housing 1, around the measurement window 5. It should be noted that Figure 2 the grayscale monitoring board 6 shown in [reference] is only an example with an exaggerated thickness for easy understanding and identification, and it will not block the optical axes of the illumination light source 2 and the grayscale camera 3 in the actual measurement device. Additionally, in Figure 2 there are two grayscale monitoring boards 6, respectively arranged on the left and right sides of the measurement window 5, but the present invention is not limited thereto. The two grayscale monitoring boards 6 can also be arranged on the front and rear sides of the measurement window 5, or only one grayscale monitoring board 6 can be arranged on any one of the front, rear, left, and right sides of the measurement window, as long as at least a part of the grayscale monitoring board 6 is within the shooting area of the grayscale camera 3, so that the grayscale camera 3 can perform grayscale imaging on at least a part of it to obtain its grayscale value. Here, the shooting area of the grayscale camera 3 refers to the range within which the grayscale camera 3 can perform grayscale imaging, and the area of the shooting area should be larger than the area of the measurement window 5.

[0050] It is easy to understand that although the above processes of regular calibration and real-time monitoring are both carried out using the measured grayscale values, the present invention is not limited thereto. The glossiness value can also be obtained through a mapping relationship to calculate the corresponding linear coefficient, thereby completing regular calibration and real-time monitoring.

[0051] Figure 3 is a schematic diagram of the glossiness measurement principle of the convergent optical path according to international standards. In Figure 3 , θ 1 is the incident angle, θ 2 is the reflection angle, α 1 is the incident divergence angle in the measurement plane, α 2 is the reflection divergence angle in the measurement plane, β 1 is the incident divergence angle perpendicular to the measurement plane, β 2 is the reflection divergence angle perpendicular to the measurement plane, S 1 is the incident field stop, S 2 is the reflection field stop, S 3 is the aperture stop, where the measurement plane refers to the plane formed by the incident optical axis and the reflection optical axis.

[0052] Table 2 below shows the angular requirements for the incident opening angle and the reflected opening angle when measuring glossiness at different incident angles according to the international standard ISO 2813:2014. It can be seen from Table 2 that the reflected opening angle is greater than the incident opening angle. Especially when the incident angle is 60°, the reflected opening angle β perpendicular to the measurement plane 2 is 11.7° ± 0.2°. Therefore, when measuring glossiness based on this international standard, a detection device with a larger receiving area is required, resulting in a higher cost.

[0053] Table 2

[0054] θ <![CDATA[α 1 > <![CDATA[β 1 > <![CDATA[α 2 > <![CDATA[β 2 > Measurement object 20° 0.75°±0.1° 2.5°±0.1° 1.80°±0.05° 3.6°±0.1° High gloss 60° 0.75°±0.1° 2.5°±0.1° 4.4°±0.1° 11.7°±0.2° Medium gloss 85° 0.75°±0.1° 2.5°±0.1° 4.0°±0.3° 6.0°±0.3° Low gloss

[0055] According to an embodiment of the glossiness measurement device of the present application, the incident opening angle of the illumination light source 2 relative to the center of the measurement area in the measurement plane is α′ 1 and the incident opening angle perpendicular to the measurement plane is β′ 1 . The reflected opening angle of the grayscale camera 3 relative to the center of the measurement area in the measurement plane is α′ 2 and the reflected opening angle perpendicular to the measurement plane is β′ 2 , where α′ 1 >α′ 2 , β′ 1 >β′ 2 . According to the technical solution of the present application, the incident opening angle is greater than the reflected opening angle, that is, the illumination solid angle of the illumination light source 2 is increased, enabling glossiness measurement over a larger range. On the other hand, the field of view of the grayscale camera 3 can be smaller, reducing the requirements for the field of view of the detection device and thus reducing costs. Moreover, according to the technical solution of the present application, grayscale imaging is performed using the grayscale camera, and the corresponding glossiness value is obtained through the grayscale value. In this way, within the incident opening angle range of the illumination light source, the glossiness value at the corresponding position of each pixel of the grayscale camera can be measured, that is, the glossiness of a very small area can be measured.

[0056] According to another embodiment of the present application, α′ 1 , α′ 2 , β′ 1 and β′ 2 are set such that the measurement optical path of the glossiness measurement device is a reverse optical path conforming to the international standard ISO2813:2014. Here, the reverse optical path conforming to the international standard ISO2813:2014 means that the optical path of the glossiness measurement device of the present application is the reverse optical path of the optical path of the international standard ISO2813:2014, that is, as shown in Table 3, α′ 1 =α 2 , α′ 2 =α 1 , β′ 1 =β 2 , β′2 = β 1 According to the principle of reversibility of light path, the glossiness measuring device of the present application still meets the measurement requirements of the international standard ISO2813:2014, has a very high degree of matching with the international standard, high glossiness measurement accuracy, and good consistency.

[0057] Table 3

[0058] θ <![CDATA[α′ 1 > <![CDATA[β′ 1 > <![CDATA[α′ 2 > <![CDATA[β′ 2 > Measurement object 20° 1.80°±0.05° 3.6°±0.1° 0.75°±0.1° 2.5°±0.1° High gloss 60° 4.4°±0.1° 11.7°±0.2° 0.75°±0.1° 2.5°±0.1° Medium gloss 85° 4.0°±0.3° 6.0°±0.3° 0.75°±0.1° 2.5°±0.1° Low gloss

[0059] According to another embodiment of the present application, the illumination light source 2 of the glossiness measuring device is a uniform illumination system. The light outlet of the uniform illumination system is rectangular, and the size of the light outlet and the distance from the light outlet to the measurement area are set such that the incident opening angle of the illumination light source 2 relative to the center of the measurement area in the measurement plane is α′ 1 , and the incident opening angle perpendicular to the measurement plane is β′ 1 ′ . The uniform illumination system can be realized by means of an integrating sphere, ground glass, opal glass, Köhler illumination, fly-eye lens, or optical fiber, etc. Among them, the uniform illumination system is preferably an integrating sphere light source.

[0060] According to another embodiment of the present application, the light-emitting element of the uniform illumination system of the glossiness measuring device is any one or a combination of a xenon lamp, a halogen lamp, a white LED, or a color LED. Among them, the color LED refers to a monochromatic LED with a certain wavelength width, such as a green LED with a peak value of 550 nm and a full width at half maximum of 20 nm. The required spectrum can be combined by multiple color LEDs.

[0061] According to another embodiment of the present application, the light-emitting element of the uniform illumination system of the glossiness measuring device is a white LED whose spectral power distribution conforms to the international standard ISO2813:2014.

[0062] According to another embodiment of the present application, the grayscale camera 3 of the glossiness measuring device has a field stop. The size of the field stop and the distance from the field stop to the center of the measurement area are set such that the reflection opening angle of the grayscale camera 3 relative to the center of the measurement area in the measurement plane is α′ 2 , and the reflection opening angle perpendicular to the measurement plane is β′ 2 .

[0063] According to another embodiment of the present application, the glossiness measurement device further includes a filter, which is disposed in the measurement optical path of the glossiness measurement device and is used to trim the spectral power distribution to conform to the international standard ISO2813:2014. The filter being disposed in the measurement optical path means that the filter can be disposed at any position between the illumination light source 2 and the grayscale camera 3. Preferably, the filter can be disposed at the light outlet of the illumination light source 2 or at the lens of the grayscale camera 3.

[0064] For the glossiness measurement device provided by the present application, based on the international standard ISO2813:2014, the incident angle of the illumination light source 2 and the reflection angle of the grayscale camera 3 can be set to θ 1 = θ 2 = 20°, or can be set to θ 1 = θ 2 = 60°, or can be set to θ 1 = θ 2 = 85° to measure samples to be measured with different glossiness.

[0065] The present application also provides a non-contact glossiness measurement method based on imaging technology. Using the glossiness measurement device described above for measurement, at least one target sub-region is selected within the measurement region through the control software, and the average glossiness value of the target sub-region is calculated according to the grayscale values of each pixel within the target sub-region.

[0066] Figure 4 This is the user interface of the control software for the glossiness measurement device according to the present application. Figure 4 The left part shows the grayscale image obtained by imaging the sample to be measured within the measurement region using the glossiness measurement device. Multiple target sub-regions can be selected within the measurement region through the user interface of the control software for glossiness measurement respectively. The target sub-region can be rectangular, square, circular, oval, or any other arbitrary closed shape. Figure 4 The right part shows the calculated glossiness value. The control software obtains the grayscale value of each pixel within the target sub-region, averages the grayscale values of all pixels to obtain the average grayscale value of the target sub-region, and then calculates the average glossiness value of the target sub-region according to the mapping relationship between the calibrated grayscale value and the glossiness value described in the present application. It is also possible to first calculate the glossiness value of each pixel according to the calibrated mapping relationship, and then average the glossiness values of all pixels within the target sub-region to obtain the average glossiness value of the target sub-region.

[0067] The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can think of changes or substitutions that should be covered within the protection scope of the present application; without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A non-contact gloss measurement device based on imaging technology, characterized in that: include: A housing, wherein a measuring window is provided on a top cover of the housing, and a measuring area is located above the measuring window; An illumination light source is installed inside the housing and located on one side of the measurement window, and is used to illuminate the measurement area at an incident angle θ1; A grayscale camera is installed inside the housing and located on the other side of the measuring window, and is used to receive light reflected from the measuring area at a reflection angle θ2 for grayscale imaging, measure grayscale values, and obtain glossiness values ​​according to the grayscale values; The optical axis of the illumination light source and the optical axis of the grayscale camera intersect at the center of the measurement area, and the incident angle of the illumination light source in the measurement plane relative to the center of the measurement area is α ′ 1. The incident angle perpendicular to the measuring plane is β1 ′ , the reflection angle of the grayscale camera relative to the center of the measurement area in the measurement plane is α ′ 2. The reflection angle perpendicular to the measurement plane is β2 ′ , where θ1 = θ2, α ′ 1>α ′ 2, β1 ′ >β2 ′ .

2. The gloss measuring device according to claim 1, characterized in that: α ′ 1. Alpha ′ 2. β1 ′ and β2 ′ The device is configured such that the measuring optical path of the gloss measuring device is a reverse optical path that complies with the international standard ISO2813:2014.

3. The gloss measuring device according to claim 1, characterized in that: The illumination light source is a uniform light illumination system, the light outlet of the uniform light illumination system is rectangular, and the size of the light outlet and the distance from the light outlet to the center of the measurement area are set so that the incident angle of the illumination light source relative to the center of the measurement area in the measurement plane is α ′ 1. The incident angle perpendicular to the measuring plane is β1 ′ .

4. The gloss measuring device according to claim 3, characterized in that: The uniform light illumination system is an integrating sphere light source.

5. The gloss measuring device according to claim 3, characterized in that: The light emitting element of the uniform light illumination system is any one of a xenon lamp, a halogen lamp, a white light LED, or a color LED, or a combination thereof.

6. The gloss measuring device according to claim 3, characterized in that: The light emitting element of the uniform light illumination system is a white light LED whose spectral power distribution complies with the international standard ISO2813:2014.

7. The gloss measuring device according to claim 1, characterized in that: The grayscale camera has a field stop, and the size of the field stop and the distance from the field stop to the center of the measurement area are set so that the reflection angle of the grayscale camera relative to the center of the measurement area in the measurement plane is α ′ 2. The reflection angle perpendicular to the measurement plane is β2 ′ .

8. The gloss measuring device according to claim 1, characterized in that: It also includes a filter, which is arranged in the measuring light path of the gloss measuring device and is used to trim the spectral power distribution to comply with the international standard ISO2813:2014.

9. The gloss measuring device according to claim 1, characterized in that: A grayscale monitoring board is arranged on at least one side of the measuring window, at least a part of the grayscale monitoring board is located in the shooting area of ​​the grayscale camera, and the grayscale monitoring board is used to monitor and calibrate the measured grayscale value.

10. The gloss measuring device according to any one of claims 1 to 9, characterized in that: θ1=θ2=20°, or θ1=θ2=60°, or θ1=θ2=85°.

11. A non-contact gloss measurement method based on imaging technology, characterized in that: The gloss measuring device according to any one of claims 1 to 9 is used for measurement, at least one target sub-area is selected in the measurement area through control software, and the average gloss value of the target sub-area is calculated according to the gray value of each pixel in the target sub-area.

12. The gloss measurement method according to claim 11, characterized in that: It also includes monitoring and calibrating the measured grayscale value using a grayscale monitoring board.

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