Uniform light source platform for camera calibration, non-uniformity measurement, correction method

Abstract

The present invention provides a uniform light source platform, non-uniformity measurement and correction method for camera calibration, wherein the uniform light source platform includes an integrating sphere and a light shielding box; the light outlet of the integrating sphere is connected to the light inlet of the light shielding box, the detection port of the integrating sphere is connected to an illumination sensor, a plurality of baffles are arranged in the light shielding box, and the plurality of baffles in the light shielding box are respectively parallel to the light inlet and the light outlet of the light shielding box; the camera to be tested is located at the light outlet of the light shielding box, and the light outlet of the light shielding box matches the maximum photosensitive surface size of the camera to be tested. The uniform light source device provided by the present invention has a simple structure and low cost. Through the design of special baffles, the problem of light reflected from the inner wall of the light shielding box is solved, and the uniformity of the light source is achieved. The camera flat field correction method provided by the present invention, combined with the uniform light source device, realizes the correction of the response consistency of each pixel.

Description

Technical Field

[0001] The present invention relates to the technical field of camera calibration, and in particular to a uniform light source platform for camera calibration and a non-uniformity measurement method and correction method. Background Art

[0002] Due to process reasons, the original image output by the camera's image sensor usually contains some defects, such as bad pixels, clusters, horizontal and vertical stripes, etc. The original image also usually shows spatial non-uniformity. These problems can be solved by calibrating under a uniform light source. In addition, the cleanliness of stains and dust on the surface of the image sensor also needs to be judged by imaging under a uniform light source. Therefore, a uniform light source device is very important for the factory calibration of the camera.

[0003] The most critical parameters of a uniform light source device are uniformity and brightness, and uniformity is reflected in spatial uniformity and temporal uniformity. The present invention can meet the requirements of ultra-large format cameras for uniform light sources.

[0004] The prior art usually uses a fiber optic light source or an LED light source, which irradiates the camera's photosensitive surface after passing through an integrating sphere. In order to ensure the uniformity of the irradiation, the integrating sphere and the camera's photosensitive surface need to be separated by a certain distance. If no light shield is added in between, the entire device needs to be installed in a dark room. Even in a dark room, if multiple sets of uniform light source devices are to be installed at the same time, the devices will interfere with each other, causing reflected light to enter the camera. In addition, tables, walls, etc. will also cause reflections, ultimately resulting in uneven irradiation received by the camera. If a light shield is added between the integrating sphere and the camera, the inner wall of the light shield will have diffuse reflections that will be received by the camera. Light-absorbing velvet cloth can avoid the problem of inner wall reflections, but long-term use will cause hair loss, which may fall onto the camera's photosensitive surface and affect camera imaging. Summary of the invention

[0005] The present invention provides a uniform light source platform for camera calibration and a method for measuring and correcting non-uniformity, which can solve the above technical problems.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A uniform light source platform for camera calibration, comprising an integrating sphere and a light shielding box, wherein a light outlet of the integrating sphere is connected to the light shielding box, a plurality of baffles are arranged in the light shielding box, and the plurality of baffles in the light shielding box are respectively parallel to a light inlet of the light shielding box and a light outlet of the light shielding box;

[0008] The camera under test is located at the light outlet of the light shielding box, and the light outlet of the light shielding box matches the maximum photosensitive surface size of the camera under test.

[0009] Furthermore, the baffle is provided with a through hole, which is circular in shape, and the central axis of the through hole coincides with the central axis of the light outlet of the integrating sphere, the central axis of the light inlet of the shading box, and the central axis of the light outlet of the shading box.

[0010] Furthermore, a light blocking sheet is arranged on the through hole of the baffle plate, and the light blocking sheet is arranged on the baffle plate facing the light entrance of the shading box body, and the light blocking sheet includes a plurality of blades distributed in a rotational stack along the outer edge of the through hole.

[0011] Furthermore, the color of the outer side of the light shielding sheet is black, and the light shielding sheet is formed by fixing a blade on the baffle plate by adhesive or black screws.

[0012] Furthermore, the platform also includes a light source, which is fixed on the side wall of the integrating sphere, and the light emitting direction of the light source is toward the inside of the integrating sphere; inside the integrating sphere, a baffle is arranged in front of the light source to prevent the light source from directly emitting light from the light outlet.

[0013] Furthermore, the diameter d of the baffle through hole is n Satisfied with

[0014]

[0015] The center diameter of the light outlet of the integrating sphere is D, the diagonal of the light outlet of the shading box is d, and the distances of the baffle plate from the light outlet of the integrating sphere and the light outlet of the shading box are x n1 、x n2 .

[0016] Furthermore, the material of the light-shielding box body is one of a black matte acrylic plate and a blackened metal plate with a sandblasted surface, and two cross beams are respectively installed on the upper and lower parts of the light-shielding box body.

[0017] Furthermore, the relationship between the camera size, uniformity and integrating sphere distance is as follows:

[0018]

[0019] E0 is the illumination at the center of the camera’s photosensitive surface, E e is the illumination at the edge of the camera’s photosensitive surface, the diameter of the integrating sphere’s light outlet is D, The angle is defined as the angle between the line from the edge of the camera's photosensitive surface to the center of the light outlet and the horizontal line.

[0020] On the other hand, the present invention discloses a method for measuring light source non-uniformity, based on the above-mentioned uniform light source platform for camera calibration, the camera to be measured is installed on a camera mounting frame, and the camera mounting frame can be adjusted to include an X-axis displacement mechanism and a Y-axis displacement mechanism, comprising the following steps:

[0021] Step 1: Fix a high-speed linear array camera in the middle of the X-axis displacement mechanism, and then fix the device at the light outlet of the light shielding box to ensure that when the scale is at zero scale, the central pixel of the linear array camera is in the middle of the light outlet of the light shielding box;

[0022] Step 2: Adjust the displacement mechanism in the horizontal and vertical directions respectively, collect M lines of data at each position, take the fixed pixel in the middle of the image, and calculate the average value of 1000 lines of data;

[0023] Step 3: Draw two curves based on the average values ​​of fixed pixels recorded during the horizontal and vertical scanning process to represent the uniformity of the light source in the horizontal and vertical directions. The curves are high in the middle and low on both sides. The highest point is the center of the light source. Divide all the data in each direction by the highest point to obtain the ratio of the light source brightness attenuation, which is the non-uniformity of the light source.

[0024] Step 4: According to the center position of the light source measured in step 3, adjust the horizontal and vertical positions of the light shielding box in opposite directions, and then re-execute steps 2 and 3.

[0025] In another aspect, the present invention further discloses a camera flat field correction method, based on the above-mentioned uniform light source platform for camera calibration, comprising the following steps:

[0026] S1: Fix the camera under test at the light outlet of the light shielding box;

[0027] S2: Adjust the height of the camera to be tested so that the center of the camera's photosensitive surface is aligned with the center of the light outlet of the light shielding box;

[0028] S3: Extraction of bad pixels in dark field; that is, turn off the light source, and the camera continuously collects several pictures, performs 5*5 median filtering on each picture, and then subtracts the filtered picture from the original picture to calculate the absolute value, set a reasonable threshold, extract all bad pixel coordinates, and merge the bad pixel coordinates of all dark field pictures together and sort them;

[0029] S4: bright field bad pixel extraction; that is, turn on the light source, adjust the light source brightness and exposure time so that the brightness of the camera captured image is 70% of the full brightness, repeat step S3, merge the extracted dark field bad pixels and bright field bad pixels together and sort them to obtain a final bad pixel list; wherein, the process of step S3 includes: the camera continuously captures a number of pictures, performs a 5*5 median filter on each picture, then subtracts the filtered picture from the original picture, calculates the absolute value, sets a reasonable threshold, and extracts the coordinates of all bad pixels;

[0030] S5: Bad pixel correction: According to the bad pixel list, all the bad pixels in the image are replaced with the nearest non-bad pixel pixels;

[0031] S6: Dark field non-uniformity calibration; that is, turn off the light source, the camera continuously collects several pictures, calculates the average value of each pixel in all pictures, and obtains an average image I B , remove the influence of image noise;

[0032] S7: Bright field non-uniformity calibration; that is, turn on the light source, adjust the light source brightness and exposure time so that the camera captures the image brightness at 70% of the full brightness, repeat S6 step to obtain an average image I W , assuming I W The maximum value is I W_MAX , calculate K W =I W_MAX -I W ; Wherein, the process of step S6 includes: the camera continuously collects a number of pictures and calculates the average value of each pixel in all pictures;

[0033] S8: Non-uniformity correction; ie, calculation of I'=I*K W +I B .

[0034] It can be seen from the above technical solutions that the uniform light source platform and method for camera calibration of the present invention have the following beneficial effects:

[0035] The uniform light source device provided by the present invention has a simple structure and low cost. The distance between the camera photosensitive surface and the integrating sphere is accurately calculated by a formula, and the theoretical value of the uniformity of the light source is calculated. The problem of light reflected from the inner wall of the light shielding box is solved by installing a special baffle inside the light shielding box, and the uniformity of the light source is achieved without the need for a darkroom environment. The uniformity of the uniform light source device can be periodically measured by the light source uniformity detection device. The camera flat field correction method provided by the present invention, combined with the uniform light source device, realizes the correction of the response consistency of each pixel. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 and Figure 2 It is a schematic diagram of the overall structure of the device according to the embodiment of the present invention;

[0037] Figure 3 is a schematic structural diagram of a light-shielding box according to an embodiment of the present invention;

[0038] Figure 4 is a schematic diagram of the structure of a baffle, a through hole and a light blocking sheet according to an embodiment of the present invention;

[0039] Figure 5 is a schematic diagram of the structure of a light blocking sheet with a through hole in an embodiment of the present invention;

[0040] Figure 6 is a schematic diagram of the integrating sphere structure of an embodiment of the present invention;

[0041] Figure 7 It is a schematic diagram of the camera frame structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0043] A first aspect of an embodiment of the present invention provides a uniform light source device for camera calibration, which can provide a large-format uniform light source with adjustable brightness, which is used to detect image sensor defects and dust conditions, and calibrate each pixel to be equal or nearly equal, meeting the camera factory calibration requirements.

[0044] Uniform light source device such as Figures 1 to 6 As shown, it includes an integrating sphere 1, a light shielding box 2, a camera to be tested 3, a light source 4, an illumination sensor 5, a baffle 23, and a light source controller 6.

[0045] The integrating sphere 1 is used to convert the light source into a uniform light source, and includes an integrating sphere light inlet, an integrating sphere light outlet, and a plurality of integrating sphere detection ports. The integrating sphere light inlet is connected to the light source 4, the integrating sphere 1 light outlet is connected to the light inlet of the light shielding box 2, the integrating sphere 1 detection port is connected to the illumination sensor 5, and the other detection ports of the integrating sphere 1 are used to install photoelectric sensors or color sensors. In order to prevent the light source from directly hitting the camera, a small baffle is installed in front of the light source, that is, the light source is installed toward the inside of the integrating sphere, and a small baffle is installed in front of the light source on the inside of the integrating sphere to prevent the light source from directly hitting the light outlet. Specifically, the light source is fixed to the side wall of the integrating sphere, and the light outlet direction of the light source is toward the inside of the integrating sphere; inside the integrating sphere, a baffle is set in front of the light source to prevent the light source from directly hitting the light outlet.

[0046] The light shielding box 2 is used to shield the ambient light outside the light shielding box 2, prevent the ambient light from entering the photosensitive surface of the camera 3 under test, and ensure the uniformity of the light source 4. The light shielding box 2 is provided with a light inlet 21, a light shielding box light outlet 22, and a baffle 23 on both sides. A plurality of baffles 23 are provided inside the light shielding box 2, and the plurality of baffles 23 are parallel to the light inlet 21 and the light outlet 22 of the light shielding box; being parallel to each other can ensure that the light outlet of the integrating sphere, the light inlet of the light shielding box, the light outlets of each baffle, and the light outlet of the light shielding box are all on the same horizontal line, thereby ensuring that the photosensitive surface of the camera is located at the center of the optical axis and ensuring the uniformity of the illumination of the photosensitive surface of the camera.

[0047] The material of the light shielding box 2 is one of a black matte acrylic plate and a black metal plate with sandblasted surface, which minimizes surface reflection. The acrylic plate material is relatively soft, and the light shielding box 2 made of acrylic plate is respectively installed with two cross beams on the upper and lower parts to increase the structural strength and avoid deformation; the light inlet 21 of the light shielding box is circular, with the same outer diameter as the light outlet of the integrating sphere, and the opening of the integrating sphere is usually circular. The light inlet of the light shielding box is consistent with the light outlet of the integrating sphere in shape and similar in size, so the gap between the two can be reduced during installation, thereby avoiding light leakage and the entry of ambient light.

[0048] The light shielding box 2 and the integrating sphere 1 are connected to the light outlet of the integrating sphere through the light shielding box light inlet 21. The light outlet 22 of the light shielding box is rectangular, and the rectangle matches the maximum photosensitive surface size of the camera 3 under test. The rectangle is mainly used for the convenience of processing and installation. For example, aluminum alloy or acrylic plate material is used, and each surface is processed into a plate to form a light shielding box structure. A flip cover structure can be designed on the side to facilitate the installation of a fixed baffle. At the same time, the rectangle is easier to fix than a cylindrical structure.

[0049] The camera 3 under test is located at the light outlet 22 of the light shielding box 2. A camera mounting bracket 8 is installed below the camera 3. The position of the camera 3 under test is adjusted by the camera mounting bracket 8 so that the photosensitive surface of the camera 3 under test is located in the middle of the light outlet 22 of the light shielding box.

[0050] The light source 4 is one of an LED light source or a halogen light source; the LED light source is one of an RGB three-color light source, a white light source, and an infrared light source;

[0051] The light source controller 6 is connected to the light source 4 ; the light source controller 6 is a DC power supply with adjustable current, and operates in a constant current mode.

[0052] The integrating sphere is a Lambertian radiator, and its radiation brightness remains constant in any emitting direction. Figure 6 As shown, E0 is the illumination at the center of the camera’s photosensitive surface, E e is the illumination at the edge of the camera photosensitive surface, the distance between the light outlet of the integrating sphere and the center of the camera photosensitive surface is x, and the diameter of the light outlet of the integrating sphere is D; the illumination of E0 is proportional to the solid angle corresponding to the light outlet at E0, that is, proportional to the square of sinθ, so the condition is satisfied:

[0053]

[0054] Take a small surface element dS0 at the light outlet of the integrating sphere. Angular projection area dS p for:

[0055]

[0056] along The angular radiance depends only on the projected area, so:

[0057]

[0058] along Angular projection area dS p The area dS of the camera's photosensitive surface irradiated by the emitted light e for:

[0059]

[0060] along The radiation brightness received by the camera photosensitive surface in the angular direction is:

[0061] E e =E p dS p / dS e (5)

[0062] Substituting formula (3) and formula (4) into formula (5):

[0063]

[0064] According to formula (6), the farther the camera is from the integrating sphere, the smaller the angle of the emitted light corresponding to the edge of the camera's photosensitive surface, and the more uniform the illumination. According to formula (1), the farther the camera is from the integrating sphere, the lower the brightness. The larger the light outlet of the integrating sphere, the higher the brightness. However, the more complete the integrating sphere is, the closer it is to the ideal integrating sphere. When the light outlet is too large, the integrity of the integrating sphere will be destroyed, resulting in uneven light source. Usually, the diameter of the light outlet does not exceed 1 / 3 of the diameter of the integrating sphere. According to formula (6), the relationship between the camera format size, uniformity and the distance from the integrating sphere can be calculated, thereby determining the length of the light shielding box. Assuming that the uniformity of the camera's photosensitive surface is required to be above 98%, that is, the brightness difference between the corner and center of the camera is within 2%, according to formula (6) it can be obtained Thus, we can calculate according to Figure 6 , given d and We can find x.

[0065] The baffles 23 are arranged at three or four positions of 1 / 2, 1 / 4, 1 / 8, and 1 / 16 on the side of the light inlet 21 of the light shielding box body in the direction of the light shielding box body 2. The baffles 23 reduce the light reflected from the inner wall of the light shielding box body 2 from entering the camera photosensitive surface.

[0066] The baffle 23 is provided with a through hole 24, which is circular in shape, and the central axis of the through hole 24 coincides with the central axis of the integrating sphere light outlet of the integrating sphere 1, the central axis of the light shielding box light inlet 21 of the light shielding box 6, and the central axis of the light shielding box light outlet 22;

[0067] The through hole 24 of the baffle plate 23 is provided with a light blocking sheet 25, the inner end of the light blocking sheet 25 completely covers the baffle plate 23 at the edge of the through hole 24, and the light blocking sheet 25 is composed of a plurality of blades distributed in a rotating stack along the outer edge of the through hole 24; the light blocking sheet 25 is located on the baffle plate 23 on one side of the light inlet 21 of the light shielding box body;

[0068] The outer side of the light shielding sheet 25 is black, one side of the light shielding sheet is fixed to the baffle, and the other side is exposed to the outside, which is the outer side. The black color is used to absorb light, which can be achieved by sticking black tape on the surface;

[0069] The blade of the light blocking sheet 25 is a double-sided razor blade; the razor has a through hole in the middle, is light in weight, can be easily fixed, has a sharp edge, reduces the edge reflective area, and is a civilian standard product with a low cost, and other structures with sharp edges can be used as a substitute.

[0070] The light blocking sheet 25 is formed by a blade fixed on the baffle 23 by adhesive or black screws;

[0071] The diameter d of the through hole of the baffle 23 is n Satisfied with

[0072]

[0073] The center diameter of the light outlet of the integrating sphere is D, the diagonal of the light outlet 22 of the shading box is d, and the distances of the baffle plate from the light outlet of the integrating sphere and the light outlet 22 of the shading box are x n1 、x n2 ;

[0074] Light directly emitted from the light outlet of the integrating sphere can pass through the through hole 24 in the light-shielding box 2 without any obstruction and enter the photosensitive surface of the camera 3 under test; while the light irradiated on the inner wall of the light-shielding box cannot be reflected to the photosensitive surface of the camera 3 under test, and the edge of the through hole 24 is completely covered by the rotating blade stack to form a light-blocking plate 25, and the center thickness of the inner diameter of the light-blocking plate 25 is much thinner than the thickness of the baffle 23, which effectively reduces the thickness of the baffle 23 at the side edge of the through hole 24, and avoids the light passing through the through hole 24 on the baffle 23 from being reflected from the edge of the through hole 24 into the photosensitive surface of the camera 3 under test, thereby maximizing the uniformity of the light source; looking inward from the direction of the light outlet 22 of the light-shielding box, the complete light outlet of the integrating sphere can be seen, and only the light outlet of the integrating sphere is bright, while other areas are dark, indicating that the light-shielding box has successfully suppressed the reflected light.

[0075] like Figure 7 As shown, a camera mounting frame 7 is used to measure the light source non-uniformity. The camera mounting frame 7 includes an X-axis displacement mechanism 71 and a Y-axis displacement mechanism 72. Each displacement direction has a scale 74, and the scale is a center scale. The method for measuring the light source non-uniformity is as follows:

[0076] Step 1: Fix a high-speed linear array camera on the middle camera mounting block 74 of the X-axis displacement mechanism 71, and then fix the device at the light outlet 22 of the shading box to ensure that when the scale is at zero scale, the center pixel of the linear array camera is in the middle of the light outlet 22 of the shading box.

[0077] Step 2: Adjust the displacement mechanism in the horizontal and vertical directions respectively, collect several lines of data at each position. In this embodiment, 1000 lines are collected continuously, and a fixed pixel in the middle of the image is taken to calculate the average value of the 1000 lines of data.

[0078] Step 3: Draw two curves based on the average values ​​of fixed pixels recorded during the horizontal and vertical scanning process to represent the uniformity of the light source in the horizontal and vertical directions. The curves should be high in the middle and low on both sides, with the highest point being the center of the light source. Dividing all the data in each direction by the highest point will give the ratio of the light source brightness attenuation, which is the unevenness of the light source.

[0079] Step 4: According to the center position of the light source measured in the previous step, adjust the horizontal and vertical positions of the light shielding box in opposite directions, and then re-execute steps 2 and 3.

[0080] A second aspect of the present invention provides a camera flat field correction method, the specific steps are as follows:

[0081] S1: Fix the camera to be tested at the light outlet 22 of the light shielding box.

[0082] S2: Adjust the height of the camera to be tested so that the center of the camera's photosensitive surface is aligned with the center of the light outlet 22 of the light shielding box.

[0083] S3: Extraction of bad pixels in dark field. Turn off the light source, and the camera continuously collects several pictures. In this embodiment, 20 dark field pictures are collected continuously. Multiple collections can prevent flickering of some bad pixels. Perform 5*5 median filtering on each picture, subtract the filtered picture from the original picture, calculate the absolute value, set a reasonable threshold, extract all bad pixel coordinates, merge the bad pixel coordinates of all dark field pictures together and sort them.

[0084] S4: Bright field bad pixel extraction. Turn on the light source, adjust the light source brightness and exposure time so that the brightness of the camera image is about 70% of the full brightness, repeat the previous step, merge the extracted dark field bad pixels and bright field bad pixels together and sort them to obtain the final bad pixel list.

[0085] S5: Bad pixel correction. According to the bad pixel list, all bad pixels in the image are replaced with the nearest non-bad pixel pixels. The replacement function can be integrated into the camera or implemented in the image post-processing process.

[0086] S6: Dark field non-uniformity calibration. Turn off the light source, and the camera continuously collects several pictures. In this embodiment, 100 dark field pictures are continuously collected, and the average value of each pixel in all pictures is calculated to obtain an average image I. B , which can effectively remove the influence of image noise.

[0087] S7: Bright field non-uniformity calibration. Turn on the light source, adjust the light source brightness and exposure time so that the brightness of the camera image is about 70% of the full brightness, and the camera continuously collects several pictures. In this embodiment, 100 bright field pictures are collected continuously, and the average value of each pixel in all pictures is calculated to obtain an average image I. W , calculate I' W =I W -I B To remove the average image of the bright field after dark field removal, let I' W The maximum value is I' W_MAX , calculate K W (i,j)=I' W_MAX / (I' W_MAX -I' W (i,j)), where K W (i,j) is the multiplicative coefficient for each pixel.

[0088] S8: Non-uniformity correction. Calculate I' = (II B )*K W , where I is the original image captured and I' is the corrected image. This calculation process can be completed inside the camera or during image post-processing.

[0089] In summary, the uniform light source device provided by the present invention has a simple structure and low cost. Through the design of a special baffle, the problem of light reflected from the inner wall of the light-shielding box is solved, the uniformity of the light source is achieved, and a darkroom environment is not required. The camera flat field correction method provided by the present invention, combined with the uniform light source device, realizes the correction of the response consistency of each pixel.

[0090] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0091] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A uniform light source platform for camera calibration, comprising an integrating sphere and a light shielding box, wherein the light outlet of the integrating sphere is connected to the light shielding box, and characterized in that: A plurality of baffles are arranged in the light-shielding box body, and the plurality of baffles in the light-shielding box body are parallel to the light inlet of the light-shielding box body and the light outlet of the light-shielding box body respectively; The camera under test is located at the light outlet of the light shielding box, and the light outlet of the light shielding box matches the maximum photosensitive surface size of the camera under test; The baffle is provided with a through hole, the shape of the through hole is circular, and the central axis of the through hole coincides with the central axis of the integrating sphere light outlet of the integrating sphere, the central axis of the light inlet of the light shielding box, and the central axis of the light outlet of the light shielding box; The baffles are arranged at three or four positions of 1 / 2, 1 / 4, 1 / 8, and 1 / 16 on one side of the light entrance of the light shielding box body in the direction of the light shielding box body; The diameter d of the through hole n Satisfied with The center diameter of the light outlet of the integrating sphere is D, the diagonal of the light outlet of the shading box is d, and the distances of the baffle plate from the light outlet of the integrating sphere and the light outlet of the shading box are x n1 、x n2 ; The through hole of the baffle is provided with a light blocking sheet, which is arranged on the baffle facing the light entrance of the light shielding box, and includes a plurality of blades which are distributed in a rotating stack along the outer edge of the through hole; The color of the outer side of the light shielding sheet is black, and the light shielding sheet is formed by fixing a blade on a baffle plate through adhesive or black screws.

2. The uniform light source platform for camera calibration according to claim 1, characterized in that: The platform also includes a light source, which is fixed on the side wall of the integrating sphere, and the light emitting direction of the light source is toward the inside of the integrating sphere; inside the integrating sphere, a baffle is arranged in front of the light source to prevent the light source from directly emitting light from the light outlet.

3. The uniform light source platform for camera calibration according to claim 1, characterized in that: The material of the shading box is one of a black matte acrylic plate and a black metal plate with a sandblasted surface; two beams are respectively installed in the upper and lower parts of the shading box.

4. The uniform light source platform for camera calibration according to claim 1, characterized in that: The size, uniformity and distance of the integrating sphere of the camera under test satisfy the following relationship: E0 is the illumination at the center of the photosensitive surface of the camera under test, E e is the illumination at the edge of the photosensitive surface of the camera being tested, the diameter of the light outlet of the integrating sphere is D, The angle is defined as the angle between the line from the edge of the photosensitive surface of the camera under test to the center of the light outlet and the horizontal line.

5. A method for measuring light source non-uniformity, based on the uniform light source platform for camera calibration according to any one of claims 1 to 4, characterized in that: The camera under test is mounted on a camera mounting frame, and the camera mounting frame is adjustable and includes an X-axis displacement mechanism and a Y-axis displacement mechanism, including the following steps: Step 1: Fix a high-speed linear array camera in the middle of the X-axis displacement mechanism, and then fix the device at the light outlet of the light shielding box to ensure that when the scale is at zero scale, the central pixel of the linear array camera is in the middle of the light outlet of the light shielding box; Step 2: Adjust the displacement mechanism in the horizontal and vertical directions respectively, collect M lines of data at each position, take the fixed pixel in the middle of the image, and calculate the average value of 1000 lines of data; Step 3: Draw two curves based on the average values ​​of fixed pixels recorded during the horizontal and vertical scanning process to represent the uniformity of the light source in the horizontal and vertical directions. The curves are high in the middle and low on both sides. The highest point is the center of the light source. Divide all the data in each direction by the highest point to obtain the ratio of the light source brightness attenuation, which is the non-uniformity of the light source. Step 4: According to the center position of the light source measured in step 3, adjust the horizontal and vertical positions of the light shielding box in opposite directions, and then re-execute steps 2 and 3.

Images