Device and method for testing light field distribution of point light source

Abstract

The invention provides a point light source light field distribution testing device and method, and the device comprises a daylighting part, a diffusion sheet and a photographing device, a point light source part is conveyed to a testing station through a conveying device, the testing station is located below the daylighting part, the daylighting part is close to the point light source part, the diffusion sheet is arranged at the top of the daylighting part, and the photographing device is located below the diffusion sheet. The light collecting piece is arranged above the spot light source, the shooting device is arranged above the diffusion sheet, the light collecting piece collects light rays emitted by the spot light source at different angles, the light rays are scattered at the diffusion sheet, and the shooting device collects images on the diffusion sheet. According to the scheme, color testing of the light source and light field distribution are combined together, collection of all light emitting information of a point light source material can be completed through one-time testing, and the requirement for automatic testing of the LED light field is met.

Description

Technical Field

[0001] The present invention belongs to the field of LED light source detection, and particularly relates to a test device and a test method for the light field distribution of a point light source. Background Art

[0002] In various fields such as lighting and display, each lighting device often uses multiple LEDs integrated. If there is a defective product among them, it will ultimately lead to the defect of the entire lighting module, resulting in further expansion of losses. Currently, in the commonly used LED light color test technology, on the instruments for batch detection by automated equipment, an integrating sphere is generally used to collect the light emitted by the LED. The integrating sphere is fixed on the test station, and each LED is sequentially conveyed to the test station through a transmission device to be lit and then test the optical characteristics. The light emitted by the LED enters the integrating sphere and undergoes multiple diffuse reflections, and finally, from the light outlet on the right side, it is introduced into a spectrometer through an optical fiber to perform a single-point test on the light color of the LED. Since the light has undergone countless diffuse reflections, the intensity and color distribution information at different angles has been lost. Once the light color of the LED is uniform at different angles, there is no effective detection method.

[0003] For the existing light emission angle detection technology, its structure is to drive the LED to rotate by plus or minus 90 degrees through a rotating device, and then detect and record the light intensity of the LED at the current angle through a fixed photometric probe. Finally, the light emission curve of the light source is restored through data integration. However, this method has many application defects. It can only test the light intensity distribution and cannot test the color distribution and color difference; since it is still a single-point test, a rotating device is required to rotate the light source to be tested, and the test speed is slow, with each test taking between several seconds and dozens of seconds; the test data is limited, and it can only test the light field distribution on a certain axial plane of the light source to be tested, and cannot test the light field distribution of all other axial planes; the instrument is expensive, occupies a large area, and has a long test time. In practical applications, it can only be used as a sampling inspection method and cannot achieve batch testing of the light source to be tested. Summary of the Invention

[0004] The purpose of the present invention is to provide a test device and a test method for the light field distribution of a point light source, aiming to solve the problems existing in the above-mentioned existing test means.

[0005] The present invention is realized as follows. A test device for the light field distribution of a point light source includes a light collection member, a diffuser, and a photographing device. The point light source member is conveyed to the test station by a conveying device. The test station is located below the light collection member. The light collection member is disposed close to the point light source member. The diffuser is disposed on the top of the light collection member. The photographing device is disposed above the diffuser. The light collection member collects the light at different angles emitted by the point light source, and scattering occurs at the diffuser. The photographing device collects the image on the diffuser.

[0006] A further technical solution of the present invention is that: the light collecting member adopts a fiber optic bundle prism, and a plurality of regularly arranged capillary fiber arrays are arranged in the fiber optic bundle prism. The light emitted by the point light source member enters from one end of the capillary fiber array, is conducted along the vertical direction of the capillary fiber array, and finally exits from the plane at the top of the fiber optic bundle prism to the diffusion sheet.

[0007] A further technical solution of the present invention is that: the angular range of the light emitted by the point light source member collected by the fiber optic bundle prism is ±75 to 85 degrees.

[0008] A further technical solution of the present invention is that: the light collecting member adopts a convex lens group, and the convex lens group includes a plurality of stacked convex lenses. The light at different angles emitted by the point light source member enters the lowermost convex lens, is refracted by a plurality of the convex lenses, and exits from the uppermost convex lens to the diffusion sheet. When exiting, the light beam is narrowed within the range of plus or minus 45 degrees.

[0009] A further technical solution of the present invention is that: the angular range of the light emitted by the point light source member collected by the convex lens group is ±75 to 85 degrees.

[0010] A further technical solution of the present invention is that: at least two convex lenses are included in the convex lens group.

[0011] A further technical solution of the present invention is that: the photographing device includes a camera and a lens. The lens is arranged at the bottom of the camera, the lens faces the diffusion sheet, and the image of the diffusion sheet is imaged onto the sensor chip of the camera through the lens.

[0012] A further technical solution of the present invention is that: the point light source member, the light collecting member, the diffusion sheet and the photographing device are located on the same vertical line.

[0013] Another object of the present invention is to provide a detection method for a point light source light field distribution testing device. If the light collecting member is a fiber optic beam prism, the photographing device collects the image on the diffusion sheet, obtains the color and brightness of each pixel point on the image corresponding to the color and intensity of the light emitted by the point light source member at each azimuth angle, and through calculation, where θv is the angle between the light ray and the vertical normal, θh is the horizontal plane angle of the light ray, x is the physical coordinate of the light ray projected on the diffusion sheet, x = sinθ h ·A, y is the physical coordinate of the light ray projected on the diffusion sheet, y = cosθ h·A, where r is the radius of the concave surface at the bottom of the light beam prism, h is the height of the measured point light source from the center of the concave surface at the bottom of the fiber optic bundle prism, and A is the arm length between the projection point and the center point of the light on the diffuser. The pixel position of the light source at each azimuth angle in the captured photo is obtained. The color attribute of each point of the point light source part is obtained from the RGB pixel value of each pixel point, and the light intensity attribute of the point light source part is obtained by weighted summation of the RGB pixel values of each pixel point. The RGB array value is obtained and the point cloud data of the light field distribution is formed. According to the light field distribution and characteristics of different measured light sources, their light emission characteristics are analyzed, and it is judged whether they meet the test standards;

[0014] If the light collecting part is a convex lens group, due to the different wavelengths of different colors of light, the refractive indices in the convex lens group are different, and finally different-sized light spot distributions are formed on the diffuser. The red, green, and blue layers of the image are separated, and each light path with a different azimuth angle is calibrated. Through the coordinates of the laser light spots in the image obtained by lasers with different azimuths and colors, the corresponding relationship between the light color of each point and the coordinate points in the image is deduced. According to the light spot distribution of different layers, the pixel points of the corresponding color are obtained. The color attribute of each point of the point light source part is obtained from the RGB pixel value of each pixel point, and the light intensity attribute of the point light source part is obtained by weighted summation of the RGB pixel values of each pixel point. The RGB array value is obtained and the point cloud data of the light field distribution is formed. According to the light field distribution and characteristics of different measured light sources, their light emission characteristics are analyzed, and it is judged whether they meet the test standards.

[0015] A further technical solution of the present invention is: design a standard light source. Since the color and intensity of each azimuth angle of the standard light source are known, by testing the standard light source, the compensation coefficient of each azimuth angle is calculated, and the value of each pixel point after compensation is the actual value of the measured light source.

[0016] The beneficial effect of the present invention is: this solution combines the color test of the light source with the light field distribution, realizes the acquisition of all the light emission information of the point light source material in one test, and meets the requirements of the automatic test of the LED light field. Description of the Drawings

[0017] Figure 1 is a schematic diagram of the light collecting part of the present invention using a fiber optic bundle prism;

[0018] Figure 2 is a schematic diagram inside the fiber optic bundle prism of the present invention;

[0019] Figure 3 is a schematic diagram of the light collecting part of the present invention using a convex lens group;

[0020] Figure 4 is a schematic diagram of the image parameters on the diffuser of the present invention;

[0021] Figure 5 It is the original data distribution diagram of the Lambert source in the present invention;

[0022] Figure 6 It is the data distribution diagram of the Lambert source after calibration in the present invention.

[0023] Reference numerals in the drawings: 1 - point light source component, 2 - fiber bundle prism, 3 - diffusion sheet, 4 - lens, 5 - camera, 6 - convex lens, 7 - capillary fiber array. Specific embodiments

[0024] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the terms "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the drawings, and the terms "bottom surface" and "top surface", "inner" and "outer" refer to the directions towards or away from the geometric center of a specific component respectively.

[0025] A point light source light field distribution test device provided by the present invention includes a light collecting component, a diffusion sheet 3 and a photographing device. The point light source component 1 is delivered to the test station by a conveying device. The test station is located below the light collecting component. The light collecting component is arranged close to the point light source component 1. The diffusion sheet 3 is arranged on the top of the light collecting component. The photographing device is arranged above the diffusion sheet 3. The light collecting component collects light rays emitted by the point light source at different angles, and scattering occurs at the diffusion sheet 3. The photographing device collects the image on the diffusion sheet 3.

[0026] The present invention combines the color test of the light source with the light field distribution by adopting two new schemes, realizes the collection of all the light emission information of the point light source material in one test, and meets the requirements for the automatic test of the LED light field.

[0027] The first scheme adopts a fiber bundle prism 2 device with a semi-circular arc surface at the bottom. Light rays emitted from the light source in different directions enter from the ends of each capillary fiber array 7 on the arc surface of the prism, then are conducted along the vertical direction of the optical fiber, and finally are emitted from the upper plane of the fiber bundle prism 2, so as to guide the light from different angles of the light source to the same imaging plane, which is convenient for further image data collection and makes it possible to collect the entire light field.

[0028] The first scheme uses the fiber bundle prism 2 as the main light collecting device. The inside of the fiber bundle prism 2 is a large number of regularly arranged capillary fiber arrays 7, which can transmit the light color of each point at one end to the other end. The advantage of this scheme is that there is only a single light collecting component, and the requirement for the accuracy of structural positioning is low, which is suitable for testing light sources with small sizes.

[0029] The point light source component 1 is located at the bottom of the device. In order to collect as much light emitted by the point light source component 1 as possible, it should be as close as possible to the fiber optic bundle prism 2. When it is a manual instrument, the point light source component 1 can be completely close to the fiber optic bundle prism 2, so that the fiber optic bundle prism 2 can collect all the light rays emitted from the point light source component 1; when it is an on-line automated instrument, the point light source component 1 is about 1-2 mm away from the bottom of the fiber optic bundle prism 2. Because during on-line testing, the point light source component 1 passes horizontally under the fiber optic bundle prism 2 one by one through the conveying device. In order to avoid collision with the fiber optic bundle prism 2, enough safety distance needs to be left. The conveying device can adopt a conveyor belt. At this time, the fiber optic bundle prism 2 can approximately collect the light within plus or minus 75 to 85 degrees of the point light source component 1. However, considering that the point light source component 1 is usually Lambertian light and the light rays at the edge angles are already very weak, it actually has little impact on collecting most of the light of the point light source component 1.

[0030] The light emitted from the LED enters the fiber optic bundle prism 2. Inside the prism, there is the capillary fiber array 7 made of quartz material arranged vertically in a dense manner. The number of capillary fibers in the capillary fiber array 7 can reach the million level, and each light ray incident on the bottom arc surface of the fiber optic bundle prism 2 is vertically led out one by one to the plane at the top of the fiber optic bundle prism 2. A diffusion sheet 3 is covered on the top of the fiber optic bundle prism 2, so that the light rays emerging from the upper part of the fiber optic bundle prism 2 are scattered on the diffusion sheet 3. In this way, a light color distribution image is formed on the diffusion sheet 3. Each point on this image corresponds to the light color emitted by the light source from different angles, that is, the light field emitted by the light source is projected onto a plane. Here, it should be noted that as shown in the appendix Figure 1 As shown, there is a gap between the fiber optic bundle prism 2 and the diffusion sheet 3. In actual application, the fiber optic bundle prism 2 and the diffusion sheet 3 are in a close contact relationship. The image on the diffusion sheet 3 is imaged onto the sensor chip of the camera 5 after passing through the lens 4, and the image on the diffusion sheet 3 is collected by taking a picture with the camera 5. The camera 5 here can adopt an industrial camera.

[0031] The second solution uses a device with multiple arc convex lens groups. The light from the light source in different directions enters the convex lens 6. After multiple refractions by the convex lens 6, the traveling direction of the light source is changed, and the original emission angle of plus or minus 90 degrees is narrowed to an angle of plus or minus 45 degrees or less. Then, a diffusion sheet 3 is placed at the upper end of the convex lens group, and the light can be projected onto the same imaging plane at different angles, which is convenient for further image data collection.

[0032] Using the convex lens group as the main light collection device, the convex lens group is composed of 2-3 convex lenses 6. Since the large-sized fiber optic bundle prism 2 is costly and difficult to manufacture, when the light source to be measured is relatively large, it is more suitable to use the convex lens group.

[0033] The point light source component 1 is located at the bottom of the device. To collect as much light emitted by the point light source component 1 as possible, it should be as close as possible to the convex lens group. When it is a manual instrument, the point light source component 1 can be completely close to the convex lens group, so that the convex lens group can collect all the light rays emitted from the point light source component 1; when it is an online automated instrument, the point light source component 1 is about 1 - 2 mm away from the bottom of the convex lens group. Because during online testing, the point light source component 1 passes horizontally one by one under the convex lens group through the conveying device. To avoid collision with the convex lens group, enough safety distance needs to be left. At this time, the convex lens group can approximately collect the light within plus or minus 75 - 85 degrees of the point light source component 1.

[0034] The light emitted from the point light source component 1 enters the convex lens group, and the emission angle of the light source is gradually narrowed through several convex lenses 6. A diffuser 3 is covered on the top of the convex lens group, so that the light emerging from the upper part of the convex lens group forms scattering on the diffuser 3. In this way, a light color distribution image is formed on the diffuser 3. Each point position on this image corresponds to the light color emitted by the light source from different angles, that is, the light field emitted by the light source is projected onto a plane. The image on the diffuser 3 is imaged onto the sensor chip of the camera 5 after passing through the lens 4, and the image on the diffuser is collected by taking a picture with the camera 5.

[0035] The test method of this solution is as follows:

[0036] Data acquisition and processing. The image of the diffuser 3 is collected by an industrial camera placed above the diffuser 3. The color and brightness of each pixel position on the image correspond to the color and intensity of the light emitted by the light source at each azimuth angle. That is to say, this image contains all the light field information of the light source. The color attributes are obtained through the RGB pixel values of each point position obtained by photographing with the photographing device, and the weighted sum of the RGB pixel values of each point position obtained by photographing with the photographing device is the light intensity value of each point position of the point light source component.

[0037] In the first solution, it is necessary to obtain the pixel point coordinates of the captured image corresponding to each azimuth angle of the light source. It is necessary to calculate the physical coordinates x, y of the light rays at each different vertical inclination angle and horizontal rotation angle on the diffuser 3. The following are the corresponding calculation formulas:

[0038] θv: The angle between the light ray and the vertical normal;

[0039] θh: The angle between the light ray and the horizontal plane;

[0040] x: The physical coordinate x of the projection of the light ray on the diffuser 3;

[0041] y: The physical coordinate y of the projection of the light ray on the diffuser 3;

[0042] r: Radius of the concave surface at the bottom of the light beam prism;

[0043] h: Height of the light source under test from the center of the concave surface at the bottom of the light beam prism;

[0044] A: Arm length between the projection point and the center point of the light on the diffuser 3;

[0045]

[0046] x = sinθ h ·A

[0047] y = cosθ h ·A.

[0048] In the second solution, since the color camera captures the red, green, and blue images on the diffuser 3, and lights of different colors have different refractive indices in the lens group due to different wavelengths, and finally form spot distributions of different sizes on the diffuser 3. Therefore, it is necessary to separate the red, green, and blue layers of the image, and obtain the corresponding color pixel points according to the spot distributions of different layers. Calibrate each optical path with different azimuth angles, and through the lasers with different azimuths and colors and the laser spot coordinates in the captured image, inversely deduce the corresponding relationship between the light color of each point and the coordinate points in the image. Obtain the corresponding color pixel points according to the spot distributions of different layers. The color attribute of each point of the point light source component is obtained from the RGB pixel values of each pixel point, and the light intensity attribute of the point light source component is obtained by weighted summation of the RGB pixel values of each pixel point, obtain the RGB array value and form the point cloud data of the light field distribution. According to the light field distributions and characteristics of different light sources under test, analyze their light emission characteristics and determine whether they meet the test standards.

[0049] The difference between the second solution and the first solution is only the different ways of light propagation and collection. Finally, the shooting device is also used for shooting, so the software level for analyzing whether the parameters are qualified is the same. However, in the problem of obtaining the corresponding screen coordinates for each light-emitting point, due to the complexity of the lens optical path and considering the refractive index differences of the three primary colors, lasers of red, green, and blue will be used respectively to calibrate each optical path with different azimuth angles. Through the lasers with different azimuths and colors and the laser spot coordinates in the captured image, inversely deduce the corresponding relationship between the light color of each point and the coordinate points in the image, and fit the series equation formula of the azimuth angle and the coordinate position.

[0050] In the first solution, since the angles at which the light rays emitted from different azimuth angles of the light source under test enter the fiber bundle prism 2 are different, there are differences in the coupling efficiency. Coupled with factors such as the diffusion plate and the image distortion of the camera lens, the intensity distribution of each pixel of the image finally captured by the camera 5 does not exactly equal the light intensity emitted from each azimuth angle of the light source under test. However, the intensity of each pixel point is proportional to the theoretical value. Similarly, in the second solution, due to the refractive index differences of the convex lenses, the intensity distribution of each pixel of the image finally captured by the camera 5 does not exactly equal the light intensity emitted from each azimuth angle of the light source under test. Therefore, a standard light source can be designed. The RGB values of the pixel positions obtained by the imaging device are only the original values captured by the camera. Since attenuation occurs through the optical path, intensity calibration must be performed. The optical path is irradiated with a standard Lambertian light. By calculating the division of the theoretical value by the original value captured, the correction coefficient for each point is obtained. Place a Lambertian light at the sample collection position of this device and turn it on. Assume that the RGB pixel values captured by the camera are I R 、I G 、I B , the angle between the light ray and the vertical normal is θv, and the top light intensity of the Lambertian light is It. The formula is calculated as follows:

[0051] The intensity value of the Lambertian light at a certain azimuth angle:

[0052] I s =I t ·cosθv

[0053] The correction coefficient of each pixel RGB value:

[0054]

[0055] Since the color and intensity of each azimuth angle of the standard light source are known, by testing the standard light source, the compensation coefficient for each azimuth angle is calculated. The numerical value of each pixel point after compensation is the actual value of the light source under test. The RGB array values after coefficient correction constitute the point cloud data of the light field distribution. According to the light field distribution and characteristics of different light sources under test, corresponding algorithms are written to analyze their light emission characteristics and determine whether they meet the test standards.

[0056] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A test device for the light field distribution of a point light source, characterized in that, It includes a light collecting component, a diffuser, and a photographing device. The point light source component is delivered to the test station by a conveying device. The test station is located below the light collecting component. The light collecting component is arranged close to the point light source component. The diffuser is arranged on the top of the light collecting component. The photographing device is arranged above the diffuser. The light collecting component collects the light emitted by the point light source at different angles, and scattering occurs at the diffuser. The photographing device collects the image on the diffuser.

2. The point light source light field distribution testing device according to claim 1, characterized in that, The light collecting component adopts a fiber optic bundle prism. A number of regularly arranged capillary fiber arrays are arranged inside the fiber optic bundle prism. The light emitted by the point light source component enters from one end of the capillary fiber array and is conducted along the vertical direction of the capillary fiber array, and finally exits from the plane at the top of the fiber optic bundle prism to the diffuser.

3. The point light source light field distribution testing device according to claim 2, wherein The angular range of the light emitted by the point light source component collected by the fiber optic bundle prism is ±75 - 85 degrees.

4. The point light source light field distribution testing device according to claim 1, characterized in that The light collecting component adopts a convex lens group. The convex lens group includes a number of stacked convex lenses. The light at different angles emitted from the point light source component enters the lowermost convex lens, and after being refracted by a number of the convex lenses, it exits from the uppermost convex lens to the diffuser. When exiting, the light beam narrows within the range of plus and minus 45 degrees.

5. The point light source light field distribution testing device according to claim 4, wherein The angular range of the light emitted by the point light source component collected by the convex lens group is ±75 - 85 degrees.

6. The point light source light field distribution testing device according to claim 4, wherein, The convex lens group includes at least two convex lenses.

7. The point light source light field distribution testing device according to claim 1, wherein The photographing device includes a camera and a lens. The lens is arranged at the bottom of the camera. The lens faces the diffuser. The image of the diffuser is imaged onto the sensor chip of the camera through the lens.

8. The test device for the light field distribution of a point light source according to claim 1, characterized in that, The point light source component, the light collecting component, the diffuser, and the photographing device are located on the same vertical line.

9. A detection method for a point light source light field distribution test device according to any one of claims 1-8, characterized in that, If the lighting component is a light beam prism, the imaging device acquires the image on the diffuser, obtains the color and brightness of each pixel position on the image corresponding to the color and intensity of the light emitted by the point light source component at each azimuth angle, and through calculation, where θv is the angle between the light and the vertical normal, θh is the angle of the light with the horizontal plane, x is the physical coordinate of the projection of the light on the diffuser, x = sinθ h ·A, y is the physical coordinate of the projection of the light on the diffuser, y = cosθ h ·A, r is the radius of the bottom concave surface of the light beam prism, h is the height of the measured point light source from the center of the bottom concave surface of the fiber optic beam prism, A is the arm length between the projection point of the light on the diffuser and the center point, to obtain the pixel position of the light source at each azimuth angle in the captured photo. The color attribute of each point position of the point light source component is obtained from the RGB pixel value of each pixel position, and the light intensity attribute of the point light source component is obtained by weighted addition of the RGB pixel values of each pixel position, to obtain the RGB array value and form the point cloud data of the light field distribution. According to the light field distribution and characteristics of different measured light sources, analyze their light emission characteristics And determine whether it meets the test standard; If the light collecting component is a convex lens group, due to the different wavelengths of different colors of light, the refractive indices in the convex lens group are different, and finally different-sized spot distributions are formed on the diffuser. The red, green, and blue layers of the image are separated. Each optical path with a different azimuth angle is calibrated. Through the coordinates of the laser spots in the image obtained by lasers with different azimuths and colors, the corresponding relationship between the light color at each point and the coordinate points in the image is deduced inversely. The pixel points of the corresponding color are obtained according to the spot distribution of different layers. The color attribute of each point of the point light source component is obtained from the RGB pixel values of each pixel point. The light intensity attribute of the point light source component is obtained by weighted addition of the RGB pixel values of each pixel point. The RGB array values are obtained and the point cloud data of the light field distribution is formed. According to the light field distribution and characteristics of different light sources to be measured, its light emission characteristics are analyzed, and it is determined whether it meets the test standard.

10. The testing method of a testing device for the light field distribution of a point light source according to claim 9, characterized in that, Design a standard light source. Since the color and intensity of each azimuth angle of the standard light source are known, through the test of the standard light source, the compensation coefficient of each azimuth angle is calculated, and the numerical value of each pixel point after compensation is the actual value of the light source to be measured.

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