A measuring device and method for high dynamic range of camera images

Abstract

The application discloses a kind of measuring camera image high dynamic range device and method, it is provided with optical darkroom, wide dynamic light source, lens and host computer, wherein lens is installed at the opening of optical darkroom, wide dynamic light source is installed in optical darkroom inside facing lens, and wide dynamic light source includes LED lamp group and time sequence control circuit module;The target surface of the scientific camera to be measured is connected with lens, and host computer is connected with the scientific camera to be measured to establish control connection and data connection;Host computer starts the scientific camera to be measured and sends measurement start instruction to time sequence control circuit module in wide dynamic light source, time sequence control circuit module starts LED lamp group and controls the light-emitting duration of each LED lamp, after the image is photographed to the scientific camera to be measured, it is uploaded to host computer, and host computer obtains the dynamic range of the scientific camera to be measured by detecting the number of LED light spot in image.This application obtains dynamic range by analyzing the image that the scientific camera to be measured is photographed to wide dynamic light source, effectively improves dynamic ratio measurement range.

Description

Technical Field

[0001] This invention belongs to the field of scientific camera technology, and more specifically, relates to a device and method for measuring the high dynamic range of camera images. Background Technology

[0002] The "dynamic range" of an image sensor or camera characterizes the camera's ability to distinguish different levels of light; simply put, it's the ratio between the highest and lowest brightness levels. A larger dynamic range results in clearer image details. For example, a camera with a small dynamic range will result in an overexposed image in well-lit conditions and a dark image in poorly lit conditions, both of which will prevent clear observation of image details.

[0003] Currently, there are test charts available on the market for testing the dynamic range of cameras. These charts use multi-level grayscale color blocks, which the camera images through its lens. With constant incident light energy, the grayscale (i.e., brightness) of each color block is also constant. The camera's ability to resolve these color blocks represents its dynamic range. Due to technological limitations, dynamic range test charts using grayscale color block images can generally only test a dynamic range of no more than 300:1. Since the dynamic range of ordinary consumer cameras is generally between 100 and 200, this is sufficient for general photography and videography. However, for scientific cameras used in professional fields, their dynamic range is extremely wide, ranging from 2000 to 100000 times. Therefore, ordinary test charts cannot meet the testing and calibration requirements for the dynamic range of scientific cameras. Dynamic range is one of the core indicators of scientific cameras, and there are three ways and units to represent this indicator (dynamic ratio – x times: 1; dynamic range – in dB; dynamic bit depth – in bits). In industry standards, the quantitative camera testing standard EMVA1288 (see EMVA1288 Chinese version.pdf) proposes a test method for high image dynamic range. However, this method involves many measurement steps, has stringent optical requirements, and is relatively complex in calculation. For non-professionals, this method is complicated to implement and difficult to understand. Therefore, it is necessary to design a device or method for quickly and easily measuring the high dynamic range of camera images. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a device and method for measuring the high dynamic range of camera images. By designing a wide dynamic range light source and coordinating timing control, the dynamic range is obtained by analyzing the images captured by the scientific camera under test from the wide dynamic range light source, thereby effectively improving the measurement range of the dynamic ratio of scientific camera images.

[0005] To achieve the above-mentioned objective, the device for measuring the high dynamic range of camera images of the present invention includes an optical darkroom, a wide dynamic range light source, a lens, and a host computer, wherein the lens is installed at the opening of the optical darkroom, and the wide dynamic range light source is installed inside the optical darkroom facing the lens; the target surface of the scientific camera under test is connected to the lens, and the host computer establishes a control connection and a data connection with the scientific camera under test.

[0006] The wide dynamic range light source includes an LED lamp assembly and a timing control circuit module, wherein the LED lamp assembly includes... Each LED light, and the timing control circuit module is used to control the LED light under the control of the host computer. Each LED illuminates, and the control method is as follows: after receiving the measurement start command from the host computer, the timing control circuit module starts the LED group and controls the illumination duration of each LED, where the first LED... The duration of light emission of each LED light ,in , This indicates the preset emission duration base;

[0007] The host computer is used to start the scientific camera under test and set its exposure time. The exposure time setting needs to ensure that the grayscale value of the brightest spot in the image captured by the scientific camera under test is more than 90% of the full grayscale value of the scientific camera under test. Then, the host computer sends a measurement start command to the timing control circuit module of the wide dynamic range light source, and then receives the image fed back by the scientific camera under test to detect the number of LED light spots in the image. The dynamic ratio of the scientific camera under test was calculated to be: Then, the dynamic range of the scientific camera under test was calculated as follows: .

[0008] Furthermore, the optical darkroom adopts a cuboid structure.

[0009] Furthermore, the inner walls of the optical darkroom are lined with black matte velvet.

[0010] Furthermore, a guide rail perpendicular to the lens is installed in the optical darkroom, and a wide dynamic range light source is slidably fixed on the guide rail facing the lens.

[0011] Furthermore, the wide dynamic range light source includes a front cover, an LED lamp assembly, a timing control circuit module, and a rear cover. The timing control circuit module is implemented by arranging circuits on a substrate. The LED lamp assembly is fixed on the substrate of the timing control circuit module. The front cover and the rear cover cover the timing control circuit module from the front and rear directions. An opening is provided on the front cover so that the LED lamp assembly can extend out of the front cover.

[0012] Furthermore, in LED light groups The LEDs are arranged in a spiral pattern.

[0013] Furthermore, the lens employs four groups of high-transmittance coated fixed-focus optical lenses.

[0014] Furthermore, the host computer uses the following LED light spot detection algorithm to detect LED light spots:

[0015] 1) The images captured by the scientific camera under test are subjected to contrast stretching at several scaling factors. The contrast-stretched images and the original images are combined to form an image set. Let the i-th image be the i-th image set. The image is ,in , Indicates the number of images in the image set;

[0016] 2) For each image Wavelet transform was used to denoise the images, resulting in the images. ;

[0017] 3) For each image For each pixel, determine whether its pixel value is greater than a preset threshold. If so, the pixel is determined to be a pixel at the edge of the light spot; otherwise, it is not a pixel at the edge of the light spot. Threshold An adaptive threshold is used, and its calculation formula is as follows:

[0018] ,

[0019] in, Represents the wavelet transform coefficients. , , This represents the size of the wavelet transform coefficient matrix. This represents the preset initial threshold value. Indicates the preset coefficient;

[0020] 4) For each image Each light spot is determined based on the detected light spot edge, and the size of each light spot is calculated using the second-order moment method. If the light spot size is within the preset light spot size range... If the light spot is within the range, it is considered a valid light spot, and the light spot data is retained; otherwise, it is not considered a valid light spot, and the light spot data is deleted.

[0021] 5) Image All retained spots constitute a candidate spot set. The centroid coordinates of each spot in the candidate spot set are calculated, and then the distance between the centroid coordinates of each pair is calculated. If the distance between the centroid coordinates of two spots is less than a preset threshold, they are determined to belong to the same spot, and only one spot is retained. Otherwise, they are not the same spot, and no operation is performed. The last retained spot set is taken as the spot detection result.

[0022] Furthermore, the present invention also provides a method for measuring the high dynamic range of camera images, comprising the following steps:

[0023] S1: Set up an optical darkroom, place a lens at the opening of the darkroom, and place a wide dynamic range (WDR) light source inside the darkroom facing the lens. The WDR light source includes an LED light assembly and a timing control circuit module. The LED light assembly includes... Each LED light, and the timing control circuit module is used to control the LED light under the control of the host computer. One LED light is emitted; the target surface of the scientific camera under test is connected to the lens, and then the host computer establishes a control connection and a data connection with the scientific camera under test;

[0024] S2: The host computer starts the scientific camera under test and sets its exposure time. The exposure time setting needs to ensure that the gray value of the brightest spot in the image captured by the scientific camera under test is more than 90% of the full gray value of the scientific camera under test.

[0025] S3: The host computer sends a measurement start command to the timing control circuit module of the wide dynamic range light source. After receiving the measurement start command from the host computer, the timing control circuit module starts the LED light group and controls the illumination duration of each LED, where the first... The duration of light emission of each LED light ,in , This indicates the preset emission duration base;

[0026] S4: The scientific camera under test obtains an image after the exposure time ends and uploads it to the host computer;

[0027] S5: The host computer receives the image fed back by the scientific camera under test and detects the number of LED light spots in the image. The dynamic ratio of the scientific camera under test was calculated to be: Then, the dynamic range of the scientific camera under test was calculated as follows: .

[0028] Furthermore, 1) the images captured by the scientific camera under test are contrast-stretched using several stretching factors, and the contrast-stretched images and the original images are combined to form an image set, denoted as the i-th... The image is ,in , Indicates the number of images in the image set;

[0029] 2) For each image Wavelet transform was used to denoise the images, resulting in the images. ;

[0030] 3) For each image For each pixel, determine whether its pixel value is greater than a preset threshold. If so, the pixel is determined to be a pixel at the edge of the light spot; otherwise, it is not a pixel at the edge of the light spot. Threshold An adaptive threshold is used, and its calculation formula is as follows:

[0031] ,

[0032] in, Represents the wavelet transform coefficients. , , This represents the size of the wavelet transform coefficient matrix. This represents the preset initial threshold value. Indicates the preset coefficient;

[0033] 4) For each image Each light spot is determined based on the detected light spot edge, and the size of each light spot is calculated using the second-order moment method. If the light spot size is within the preset light spot size range... If the light spot is within the range, it is considered a valid light spot, and the light spot data is retained; otherwise, it is not considered a valid light spot, and the light spot data is deleted.

[0034] 5) Image All retained spots constitute a candidate spot set. The centroid coordinates of each spot in the candidate spot set are calculated, and then the distance between the centroid coordinates of each pair is calculated. If the distance between the centroid coordinates of two spots is less than a preset threshold, they are determined to belong to the same spot, and only one spot is retained. Otherwise, they are not the same spot, and no operation is performed. The last retained spot set is taken as the spot detection result.

[0035] This invention discloses an apparatus and method for measuring the high dynamic range of camera images. The apparatus includes an optical darkroom, a wide dynamic range light source, a lens, and a host computer. The lens is mounted at the opening of the optical darkroom, and the wide dynamic range light source is mounted inside the darkroom facing the lens. The wide dynamic range light source includes an LED light group and a timing control circuit module. The target surface of the scientific camera under test is connected to the lens. The host computer establishes control and data connections with the scientific camera under test. The host computer starts the scientific camera under test and sends a measurement start command to the timing control circuit module in the wide dynamic range light source. The timing control circuit module starts the LED light group and controls the illumination duration of each LED. After the scientific camera under test captures an image, it uploads it to the host computer. The host computer calculates the dynamic range of the scientific camera under test by detecting the number of LED light spots in the image.

[0036] This invention designs a wide dynamic range light source and a timing control method for it. By observing the number of LED light groups captured by the camera, the dynamic range of the scientific camera under test can be quickly determined. This breaks through the measurement range limitations of the test cards currently used in the industry, simplifies the testing process of image dynamic range, reduces the operating difficulty for non-professionals, and effectively improves work efficiency. Attached Figure Description

[0037] Figure 1 This is a structural diagram of a specific embodiment of the camera image high dynamic range measurement device of the present invention;

[0038] Figure 2 This is a structural diagram of the wide dynamic range light source in this embodiment;

[0039] Figure 3 This is a flowchart of the method for measuring the high dynamic range of camera images in this embodiment;

[0040] Figure 4 This is an example diagram of the timing control of the LED light group in this embodiment;

[0041] Figure 5 This is the original image captured by the scientific camera under test in this embodiment;

[0042] Figure 6 These are images after contrast stretching using different stretching ratios. Detailed Implementation

[0043] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0044] Example

[0045] Figure 1 This is a structural diagram illustrating a specific embodiment of the camera image high dynamic range measurement device of the present invention. To better illustrate the internal structure, Figure 1 The optical darkroom 1 is drawn as partially transparent. (Example) Figure 1 As shown, the high dynamic range measurement device for camera images of the present invention includes an optical darkroom 1, a wide dynamic range light source 2, a lens 3, and a host computer 4. The lens 3 is installed at the opening of the optical darkroom 1, and the wide dynamic range light source 2 is installed inside the optical darkroom 1 facing the lens 3. The target surface of the scientific camera under test is connected to the lens 3, and the host computer 4 establishes a control connection and a data connection with the scientific camera under test.

[0046] The wide dynamic range light source 2 in this invention includes an LED lamp group and a timing control circuit module, wherein the LED lamp group includes... Each LED light, and the timing control circuit module is used to control the LED light under the control of the host computer 4. Each LED light illuminates, and the control method is as follows: after receiving the measurement start command from the host computer 4, the timing control circuit module starts the LED light group and controls the illumination duration of each LED light, where the first LED light... The duration of light emission of each LED light ,in , This indicates the preset emission duration base.

[0047] The host computer 4 is used to start the scientific camera under test and set its exposure time. The exposure time needs to be set so that the grayscale value of the brightest spot in the image captured by the scientific camera under test is more than 90% of the full grayscale value of the scientific camera under test. In practical applications, the appropriate exposure time can be determined experimentally. Then, the host computer 4 sends a measurement start command to the timing control circuit module of the wide dynamic range light source 2, and then receives the image fed back by the scientific camera under test, detecting the number of LED light spots in the image. The dynamic ratio of the scientific camera under test was calculated to be: Then, the dynamic range of the scientific camera under test was calculated as follows: .

[0048] Because of the LED light emission duration setting in this invention, the light spots of the LED lights in the images obtained by the scientific camera under test have a difference in brightness, which is a power of 2. Therefore, the dynamic range of the scientific camera under test can be obtained by counting the number of LED light spots.

[0049] like Figure 1 As shown, in this embodiment, the optical darkroom 1 adopts a cuboid structure. In practical applications, other suitable shapes can also be adopted according to the actual situation. In this embodiment, the inner wall of the optical darkroom 1 is covered with black matte velvet, which can effectively absorb stray light from the LED lamp and reduce the number of reflections of stray light in the optical darkroom, thereby reducing the impact of LED stray light on the image quality of the scientific camera under test, ensuring the authenticity of the image, and thus ensuring the accuracy of dynamic range measurement.

[0050] Furthermore, to facilitate flexible adjustment of the wide dynamic range light source 2, a guide rail 5 perpendicular to the lens 3 is provided in the optical darkroom 1 in this embodiment. The wide dynamic range light source 2 is slidably fixed on the guide rail 5 facing the lens 3. In this way, the distance between the wide dynamic range light source 2 and the lens 3 can be adjusted according to actual needs, and the wide dynamic range light source and the lens 3 always maintain a parallel state. Moving the wide dynamic range light source back and forth will not cause it to be misaligned with the position of the camera target surface.

[0051] In order to achieve better optical performance for the wide dynamic range light source 2, the LED lamp group and timing control circuit module are encapsulated in this embodiment. Figure 2 This is a structural diagram of the wide dynamic range light source in this embodiment. For example... Figure 2 As shown, exploded views from two directions are presented to better illustrate the structure of the wide dynamic range light source 2. In this embodiment, the wide dynamic range light source 2 includes a front cover 201, an LED lamp assembly 202, a timing control circuit module 203, and a rear cover 204. The timing control circuit module 203 is implemented by arranging circuitry on a substrate. The LED lamp assembly 202 is fixed to the substrate of the timing control circuit module 203. The front cover 201 and the rear cover 204 cover the timing control circuit module 203 from both directions. An opening is provided in the front cover 201 to allow the LED lamp assembly to extend out. This recessed design effectively avoids light interference between LEDs caused by light scattering.

[0052] In this embodiment, the LED light group 202 The LEDs are arranged in a spiral pattern, which effectively avoids strong light interfering with weak light.

[0053] To further reduce mutual interference between LEDs, the front cover 201, the substrate of the timing control circuit module 203, and the rear cover 204 are all made of light-absorbing materials.

[0054] To facilitate the control of the wide dynamic range light source, this embodiment integrates a power interface 205, a programming download interface 206, an external trigger input interface 207, an external trigger output interface 208, a power adjustment interface 209, and a mode selection interface 210 on the timing control circuit module 203, wherein:

[0055] Power interface 205 is used to connect an external power source;

[0056] The programming download interface 206 is used to connect to the host computer to set the parameters of timing control;

[0057] External trigger input interface 207 and external trigger output interface 208 are used for the measurement start triggering of the four pairs of timing control circuit modules 203 of the host computer;

[0058] The power adjustment interface 209 is used to connect to the host computer to realize the power adjustment of the LED light;

[0059] The mode selection interface 210 is used to connect to the host computer to implement the pulse mode conditions of the LED light. In this embodiment, it includes four adjustable modes: 1) gradual pulse light; 2) multiplied pulse light; 3) constant pulse light; 4) continuous light. Dynamic range: 6dB-144dB.

[0060] Regarding lens 3, in order to improve the image quality captured by the scientific camera under test, lens 3 in this embodiment employs four sets of high-transmittance coated fixed-focus optical lenses. Firstly, fixed-focus lenses offer superior imaging performance compared to zoom lenses because they have fewer optical lenses. Therefore, fixed-focus lenses exhibit less chromatic aberration and image distortion, resulting in better image quality. Secondly, the high-transmittance coating significantly reduces the reflectivity of incident light from the internal optical lenses. Finally, minimizing the number of optical lenses also reduces the number of reflections between the lenses, thereby increasing light transmittance and improving image quality.

[0061] Regarding the host computer 4, LED light spot detection has a significant impact on the final detection result. In practical applications, the light spot detection algorithm can be selected according to needs. To improve the accuracy of the detection results, this embodiment proposes an LED light spot detection algorithm, the specific method of which is as follows:

[0062] 1) Image contrast stretching:

[0063] Since this invention obtains the dynamic range of the scientific camera under test by counting the number of LED light spots, and the identification of light spots with weak gray values ​​is difficult, this embodiment first performs contrast stretching on the images captured by the scientific camera under test using several stretching factors. The contrast-stretched images and the original images are then combined to form an image set, denoted as the first... The image is ,in , This indicates the number of images in the image set. Generally, in addition to the original image, 1-4 contrast-stretched images are sufficient; the specific number can be set according to actual needs.

[0064] 2) Image denoising:

[0065] Generally, light spots in an image consist of two parts: one is the actual light spot produced by the light emitted by the LED light, and the other is the background noise caused by other external light sources, environmental radiation, or sensor noise itself. There are various methods for image denoising, such as subtracting background noise or averaging adjacent pixel values. These methods have a significant noise reduction effect on images, but they are far from sufficient for tiny signals submerged in noise. Since the images captured by the scientific camera under test typically have the edge positions of the light spots defined by weak signals, and some weak light spot signals also exist, this embodiment, for each image... Wavelet transform was used to denoise the images, resulting in the images. This method extracts useful weak signals, reduces measurement errors, and effectively solves the problems of edge definition and noise removal in light spot images.

[0066] 3) Spot edge recognition:

[0067] For each image For each pixel, determine whether its pixel value is greater than a preset threshold. If so, the pixel is determined to be a pixel at the edge of the light spot; otherwise, it is not a pixel at the edge of the light spot. The threshold in this embodiment... An adaptive threshold is used, and its calculation formula is as follows:

[0068] ,

[0069] in, Represents the wavelet transform coefficients. , , This represents the size of the wavelet transform coefficient matrix. This represents the preset initial threshold value. This indicates the preset coefficient.

[0070] 4) Spot selection:

[0071] For each image Each light spot is determined based on the detected light spot edge, and the size of each light spot is calculated using the second-order moment method. If the light spot size is within the preset light spot size range... If the light spot is within the range specified, it is considered a valid light spot, and its data is retained; otherwise, it is not considered a valid light spot, and its data is deleted. By filtering the light spot size, interference from suspected small light spots caused by noise can be removed, and the situation where two or more light spots merge into one large light spot after contrast stretching can also be ruled out.

[0072] 5) Integration of spot detection results:

[0073] Will Image All retained spots form a candidate spot set. The centroid coordinates of each spot in the candidate spot set are calculated, and then the distance between the centroid coordinates of each pair of spots is calculated. If the distance between the centroid coordinates of two spots is less than a preset threshold, they are determined to belong to the same spot, and only one of the spots is retained. Otherwise, they are not considered to be the same spot, and no operation is performed. The final set of retained spots is taken as the spot detection result.

[0074] Based on the above-mentioned device for measuring the high dynamic range of camera images, this invention also proposes a method for measuring the high dynamic range of camera images. Figure 3 This is a flowchart of the method for measuring the high dynamic range of camera images in this embodiment. For example... Figure 3 As shown, the specific steps of the method for measuring the high dynamic range of camera images in this embodiment include:

[0075] S301: Configure the test environment:

[0076] An optical darkroom is set up, with a lens positioned at the opening. A wide dynamic range (WDR) light source is positioned inside the darkroom, facing the lens. The WDR light source includes an LED light assembly and a timing control circuit module. The LED light assembly includes... Each LED light, and the timing control circuit module is used to control the LED light under the control of the host computer. One LED light illuminates. The target surface of the scientific camera under test is connected to the lens, and then the host computer establishes a control connection and a data connection with the scientific camera under test.

[0077] S302: Determine the exposure time of the camera under test:

[0078] The host computer starts the scientific camera under test and sets its exposure time. The exposure time setting needs to ensure that the gray value of the brightest spot in the image captured by the scientific camera under test is more than 90% of the full gray value of the scientific camera under test.

[0079] S303: Timing control of wide dynamic range light sources:

[0080] The host computer sends a measurement start command to the timing control circuit module of the wide dynamic range light source. After receiving the measurement start command from the host computer, the timing control circuit module starts the LED light group and controls the illumination duration of each LED, where the first... The duration of light emission of each LED light ,in , This indicates the preset emission duration base.

[0081] S304: Upload test image:

[0082] The scientific camera under test obtains an image after the exposure time ends and uploads it to the host computer.

[0083] S305: Determine the dynamic range measurement results:

[0084] The host computer receives images from the scientific camera under test and detects the number of LED light spots in the images. The dynamic ratio of the scientific camera under test was calculated to be: Then, the dynamic range of the scientific camera under test was calculated as follows: .

[0085] As described above, this invention involves timing control of LEDs in a wide dynamic range light source. By setting the LED's emission time, the luminous energy is controlled, thereby enabling dynamic range measurement for a scientific camera. This is because the ratio between LED luminous energy and emission time is strictly proportional. Assuming the LED emits one unit of light energy per 1 microsecond (µs), the emission time is used to calculate... The timing design can realize the light energy ratio of LED1 light energy 1, LED2 light energy 2, LED3 light energy 4, ... and so on, thereby forming a brightness difference in the image captured by the scientific camera under test, so as to measure the dynamic range.

[0086] Figure 4 This is an example diagram of the timing control of the LED light group in this embodiment. For example... Figure 4 As shown, in this embodiment, the LED light group contains 24 LEDs. The host computer 4 first sends a trigger pulse signal, Trig_out, to the scientific camera under test to trigger its operation. Upon receiving the trigger signal, the scientific camera under test takes pictures according to the set exposure time. Then, the host computer 4 sends a measurement start command to the timing control circuit module. A certain interval needs to be set between the trigger pulse signal and the measurement start command to allow the scientific camera under test to complete the setup. This interval can be set according to actual needs. The timing control circuit module sends... Each LED receives a light-emitting enable pulse to control its illumination. In this embodiment, each measurement cycle is 3 seconds, and the camera's trigger pulse signal width is 10µs (t1=10µs), which precedes the LED pulse signal by 500µs (t2=500µs). The light pulse signals for all 24 LEDs are emitted simultaneously to ensure that all LEDs are lit at the same time. The width of each trigger pulse signal is determined according to... The relationship increases, causing the light output of each LED to increase exponentially.

[0087] In this embodiment, the scientific camera under test is a high dynamic range photonic camera. Figure 5 This is the original image captured by the scientific camera under test in this embodiment. For example... Figure 5 As shown, the original images captured by the scientific camera under test have low contrast, making them difficult to detect and observe. In practical applications, contrast stretching can be performed according to actual needs. Figure 6 These are images after contrast stretching using different stretching factors. According to... Figure 6 It can be detected that 17 LED light spots were captured in this embodiment, so the dynamic range of the test camera is 17 bits, and the dynamic ratio of the image is 2. 17 The multiple is 131072 times, then the dynamic comparison multiple is substituted in. The formula yields a dynamic range of 103.35 dB for the high dynamic range photonic camera. For comparison, this embodiment uses the current EMVA1288 standard to measure the dynamic range of the high dynamic range photonic camera, obtaining a dynamic range of 106 dB. Comparing the two test results shows an error of only 0.025, indicating that this invention can quickly obtain the camera's dynamic range using a wide dynamic range light source, effectively improving testing efficiency, reducing the difficulty of dynamic range testing, and helping users quickly determine the camera's dynamic range. Furthermore, testing revealed that this invention can achieve dynamic range measurements within the range of 6 dB to 144 dB, demonstrating its ability to measure high dynamic range.

[0088] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A device for measuring the high dynamic range of camera images, characterized in that, It includes an optical darkroom (1), a wide dynamic range light source (2), a lens (3), and a host computer (4). The lens (3) is installed at the opening of the optical darkroom (1), and the wide dynamic range light source (2) is installed inside the optical darkroom (1) facing the lens (3). The target surface of the scientific camera under test is connected to the lens (3), and the host computer (4) establishes a control connection and a data connection with the scientific camera under test. The wide dynamic range light source (2) includes an LED lamp group and a timing control circuit module, wherein the LED lamp group includes Each LED light, the timing control circuit module is used to control the upper computer (4) under the control of the host computer (4). Each LED light illuminates, and the control method is as follows: After receiving the measurement start command from the host computer (4), the timing control circuit module starts the LED light group and controls the illumination duration of each LED light, where the first LED light illuminates the first LED light. The duration of light emission of each LED light ,in , This indicates the preset emission duration base; The host computer (4) is used to start the scientific camera under test and set its exposure time. The exposure time setting needs to meet the requirement that the gray value of the brightest spot in the image captured by the scientific camera under test is more than 90% of the full gray value of the scientific camera under test. Then the host computer (4) sends a measurement start command to the timing control circuit module of the wide dynamic range light source (2), and then receives the image fed back by the scientific camera under test to detect the number of LED light spots in the image. The dynamic ratio of the scientific camera under test was calculated to be: Then, the dynamic range of the scientific camera under test was calculated as follows: .

2. The apparatus for measuring the high dynamic range of camera images according to claim 1, characterized in that, The optical darkroom (1) adopts a cuboid structure.

3. The apparatus for measuring the high dynamic range of camera images according to claim 1, characterized in that, The inner wall of the optical darkroom (1) is covered with black matte velvet.

4. The apparatus for measuring the high dynamic range of camera images according to claim 1, characterized in that, The optical darkroom (1) is equipped with a guide rail (5) perpendicular to the lens (3), and the wide dynamic range light source (2) is slidably fixed on the guide rail (5) facing the lens (3).

5. The apparatus for measuring the high dynamic range of camera images according to claim 1, characterized in that, The wide dynamic range light source (2) includes a front cover (201), an LED lamp group (202), a timing control circuit module (203), and a rear cover (204). The timing control circuit module (203) is implemented by arranging circuits on a substrate. The LED lamp group (202) is fixed on the substrate of the timing control circuit module (203). The front cover (201) and the rear cover (204) cover the timing control circuit module (203) from the front and rear directions. An opening is provided on the front cover (201) so that the LED lamp group can extend out from the front cover (201).

6. The apparatus for measuring the high dynamic range of camera images according to claim 5, characterized in that, The LED light group (202) The LEDs are arranged in a spiral pattern.

7. The apparatus for measuring the high dynamic range of camera images according to claim 1, characterized in that, The lens (3) uses four sets of high transmittance coated fixed-focus optical lenses.

8. The apparatus for measuring the high dynamic range of camera images according to claim 1, characterized in that, The host computer (4) uses the following LED light spot detection algorithm to detect LED light spots: 1) The images captured by the scientific camera under test are subjected to contrast stretching at several scaling factors. The contrast-stretched images and the original images are combined to form an image set. Let the i-th image be the i-th image set. The image is ,in , Indicates the number of images in the image set; 2) For each image Wavelet transform was used to denoise the images, resulting in the images. ; 3) For each image For each pixel, determine whether its pixel value is greater than a preset threshold. If so, the pixel is determined to be a pixel at the edge of the light spot; otherwise, it is not a pixel at the edge of the light spot. Threshold An adaptive threshold is used, and its calculation formula is as follows: ， in, Represents the wavelet transform coefficients. , , This represents the size of the wavelet transform coefficient matrix. This represents the preset initial threshold value. Indicates the preset coefficient; 4) For each image Each light spot is determined based on the detected light spot edge, and the size of each light spot is calculated using the second-order moment method. If the light spot size is within the preset light spot size range... If the light spot is within the range of valid light spots, its data is retained; otherwise, it is not considered a valid light spot and its data is deleted. 5) Image All retained spots constitute a candidate spot set. The centroid coordinates of each spot in the candidate spot set are calculated, and then the distance between the centroid coordinates of each pair is calculated. If the distance between the centroid coordinates of two spots is less than a preset threshold, they are determined to belong to the same spot, and only one spot is retained. Otherwise, they are not the same spot, and no operation is performed. The last retained spot set is taken as the spot detection result.

9. A method for measuring the high dynamic range of camera images, characterized in that, Includes the following steps: S1: Set up an optical darkroom, place a lens at the opening of the darkroom, and place a wide dynamic range (WDR) light source inside the darkroom facing the lens. The WDR light source includes an LED light assembly and a timing control circuit module. The LED light assembly includes... Each LED light, and the timing control circuit module is used to control the LED light under the control of the host computer. One LED light is emitted; the target surface of the scientific camera under test is connected to the lens, and then the host computer establishes a control connection and a data connection with the scientific camera under test; S2: The host computer starts the scientific camera under test and sets its exposure time. The exposure time setting needs to ensure that the gray value of the brightest spot in the image captured by the scientific camera under test is more than 90% of the full gray value of the scientific camera under test. S3: The host computer sends a measurement start command to the timing control circuit module of the wide dynamic range light source. After receiving the measurement start command from the host computer, the timing control circuit module starts the LED light group and controls the illumination duration of each LED, where the first... The duration of light emission of each LED light ,in , This indicates the preset emission duration base; S4: The scientific camera under test obtains an image after the exposure time ends and uploads it to the host computer; S5: The host computer receives the image fed back by the scientific camera under test and detects the number of LED light spots in the image. The dynamic ratio of the scientific camera under test was calculated to be: Then, the dynamic range of the scientific camera under test was calculated as follows: .

10. The method for measuring the high dynamic range of camera images according to claim 9, characterized in that, The host computer (4) uses the following LED light spot detection algorithm to detect LED light spots: 1) The images captured by the scientific camera under test are subjected to contrast stretching at several scaling factors. The contrast-stretched images and the original images are combined to form an image set. Let the i-th image be the i-th image set. The image is ,in , Indicates the number of images in the image set; 2) For each image Wavelet transform was used to denoise the images, resulting in the images. ; 3) For each image For each pixel, determine whether its pixel value is greater than a preset threshold. If so, the pixel is determined to be a pixel at the edge of the light spot; otherwise, it is not a pixel at the edge of the light spot. Threshold An adaptive threshold is used, and its calculation formula is as follows: ， in, Represents the wavelet transform coefficients. , , This represents the size of the wavelet transform coefficient matrix. This represents the preset initial threshold value. Indicates the preset coefficient; 4) For each image Each light spot is determined based on the detected light spot edge, and the size of each light spot is calculated using the second-order moment method. If the light spot size is within the preset light spot size range... If the light spot is within the range of valid light spots, its data is retained; otherwise, it is not considered a valid light spot and its data is deleted. 5) Image All retained spots constitute a candidate spot set. The centroid coordinates of each spot in the candidate spot set are calculated, and then the distance between the centroid coordinates of each pair is calculated. If the distance between the centroid coordinates of two spots is less than a preset threshold, they are determined to belong to the same spot, and only one spot is retained. Otherwise, they are not the same spot, and no operation is performed. The last retained spot set is taken as the spot detection result.

Images