Calibration device and calibration method for image brightness meter

Abstract

The application discloses a kind of image brightness meter's calibration device and calibration method.The calibration device includes light source module, feedback module and processing module.Light source module is as the standard light source of image brightness meter, can output adjustable light.Feedback module is used to obtain the standard chroma value and standard brightness value of LED light source in light source module.Processing module generates brightness calibration file, chroma calibration file and automatic calibration identification factor using calibration method, and then calibrates image brightness meter.Through calibration method, the three-channel gray value, brightness and chroma of image brightness meter can be calibrated, and the measurement error of image brightness meter can be effectively reduced when testing LED light source after calibration, the measurement accuracy of image brightness meter is guaranteed, so that the accurate measurement of image brightness meter to LED light source is realized.

Description

Technical Field

[0001] This application relates to the field of optical technology, and in particular to a calibration device and calibration method for an image luminance meter. Background Technology

[0002] Image luminance meters typically use area array devices such as area array CCD or CMOS as receiving devices, thus featuring large area array and high resolution. They can quickly obtain the luminance and chromaticity distribution of the light source and are currently widely used in the rapid testing of large area array light sources.

[0003] In related technologies, a standard A-light and D-light source combination color chart is typically used to calibrate an image luminance meter. The calibrated image luminance meter is then used to test the luminance and chromaticity of the light source under test. However, when using an image luminance meter calibrated with a standard A-light source to measure LED light sources, significant errors often occur. This is because standard A-light and D-light sources are continuous-spectrum light sources, while LEDs are narrow-spectrum light sources. The spectrum of the light from the standard A-light source after passing through the color chart differs greatly from that of the LED. Therefore, image luminance meters calibrated using traditional methods introduce significant errors when measuring LED light sources, failing to meet the high-precision testing requirements of image luminance meters.

[0004] It is necessary to propose a technical solution to address the problem of large errors in image luminance meters when testing LED light sources in related technologies. Summary of the Invention

[0005] The purpose of this application is to provide a technical solution to solve the problem of large errors in the testing of LED light sources by image luminance meters in related technologies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A calibration method for an image luminance meter, the image luminance meter including a filter unit and a photosensitive array, wherein in response to the image luminance meter receiving light, any photosensitive unit in the photosensitive array outputs a set of three-channel grayscale signals.

[0008] Furthermore, the method includes the following steps:

[0009] A wavelength-tunable LED light source is used as the calibration light source for the image brightness meter. The light emitted by the LED light source is filtered by the light filtering unit to form monochromatic light, which is received by the image brightness meter.

[0010] Set the exposure time for the image luminance meter, acquire multiple sets of three-channel grayscale signals output by each photosensitive unit when the image luminance meter receives monochromatic light, compare each set of three-channel grayscale signals to obtain a non-uniform calibration coefficient, and use the non-uniform calibration coefficient to calibrate each set of three-channel grayscale signals so that the deviation of each set of three-channel grayscale signals after calibration is within a preset range.

[0011] Acquire the calibrated three-channel grayscale signal and the standard brightness value of the LED light source. Based on the calibrated three-channel grayscale signal and the standard brightness value, obtain the brightness response function of the photosensitive unit for the monochromatic light. Combine the brightness response functions of each photosensitive unit for the monochromatic light to generate a brightness calibration file of the image luminance meter for the monochromatic light.

[0012] Obtain the standard chromaticity value of the LED light source. Based on the calibrated three-channel grayscale signal, the standard luminance value and standard chromaticity value of the LED light source, obtain the chromaticity response value of the photosensitive unit for the monochromatic light. Combine the chromaticity response values ​​of each photosensitive unit for the monochromatic light to generate the chromaticity calibration file of the image luminance meter for the monochromatic light.

[0013] Automatic calibration identification factors are generated based on the proportional relationship of the three-channel grayscale signals of monochromatic light, and these automatic calibration identification factors are associated with the luminance calibration file and the chrominance calibration file.

[0014] Furthermore, the calibration of each group of three-channel grayscale signals includes the following steps:

[0015] The photosensitive array of the image luminance meter is divided into regions. Based on the multiple sets of three-channel grayscale signals output by each photosensitive unit in each region, the average grayscale signal of any channel in that region is obtained.

[0016] Calculate the ratio of the mean grayscale signal of any channel in the remaining regions to the mean grayscale signal of the corresponding channel in the central region of the photosensitive array, to obtain the non-uniform calibration coefficient of any channel in each region.

[0017] Using the average grayscale signal of each channel in the central region of the photosensitive array as the standard grayscale data, the offset of each channel grayscale signal data of each photosensitive unit in the other regions after calibration by the non-uniform calibration coefficient relative to the standard grayscale data is calculated. When the offset is greater than the preset threshold, the photosensitive array is re-divided into regions until the offset is less than the preset threshold.

[0018] Furthermore, obtaining the brightness response function of the image luminance meter for this monochromatic light includes the following steps:

[0019] Obtain the standard brightness value of the LED light source, the exposure time of the image luminance meter, and the average value of the three-channel grayscale signal in the central region of the photosensitive array;

[0020] The average value of the three channels per unit time is obtained based on the exposure time of the image luminance meter and the average value of the three-channel grayscale signal in the central region of the photosensitive array.

[0021] Calculate the average brightness response value of the image luminance meter per unit time based on the average value of the three channels per unit time.

[0022] By fitting the standard luminance value and the average luminance response value per unit time, the luminance response function of monochromatic light is obtained.

[0023] Furthermore, when the filter unit is an RGB filter unit, the average brightness response value per unit time is calculated according to the following formula:

[0024] DN = 0.299R + 0.587G + 0.114B

[0025] In the formula, DN represents the average brightness response value per unit time, R represents the average value of channel R per unit time, G represents the average value of channel G per unit time, and B represents the average value of channel B per unit time.

[0026] Furthermore, when the filter unit is an XYZ filter unit, the average brightness response value per unit time is calculated according to the following formula:

[0027] DN = G,

[0028] In the formula, DN represents the average brightness response value per unit time, and G represents the average value of G channels per unit time.

[0029] Furthermore, the method also includes adjusting the brightness of the LED light source to obtain the brightness response function of each photosensitive unit for the monochromatic light under different brightness levels, so as to generate a brightness calibration file of the image luminance meter for the monochromatic light under different brightness levels.

[0030] Furthermore, when the filter unit is an RGB filter unit, obtaining the chromaticity response value of the image luminance meter for the monochromatic light includes the following steps:

[0031] Obtain the standard brightness value of the LED light source, the standard colorimetric value of the LED light source, and the exposure time of the image luminance meter;

[0032] Tristimulus values ​​are obtained based on standard chromaticity and standard luminance values;

[0033] Convert the tristimulus values ​​to RGB values;

[0034] The three-channel grayscale signal of the central region of the calibrated photosensitive array is obtained. Based on the three-channel grayscale signal of the central region of the calibrated photosensitive array and the exposure time of the image luminance meter, the average value of the three channels per unit time is obtained.

[0035] By comparing the average value of the three channels per unit time with the RGB values ​​converted from the tristimulus values, the chromaticity response value of each channel grayscale signal is obtained, so as to generate the chromaticity calibration file of the monochromatic light.

[0036] Furthermore, when the filter unit is an XYZ filter unit, obtaining the chromaticity response value of the image luminance meter for this monochromatic light includes the following steps:

[0037] Obtain the standard brightness value of the LED light source, the standard colorimetric value of the LED light source, and the exposure time of the image luminance meter;

[0038] Tristimulus values ​​are obtained based on standard chromaticity and standard luminance values;

[0039] The three-channel grayscale signal of the central region of the calibrated photosensitive array is obtained. Based on the three-channel grayscale signal of the central region of the calibrated photosensitive array and the exposure time of the image luminance meter, the average value of the three channels per unit time is obtained.

[0040] By comparing the average value of the three channels with the tristimulus value within a unit time, the chromaticity response value of the grayscale signal of each channel is obtained, so as to generate the chromaticity calibration file of the monochromatic light.

[0041] This application also provides a calibration device for an image luminance meter, the image luminance meter including a photosensitive array, in response to the image luminance meter receiving light, any photosensitive unit in the photosensitive array outputs a three-channel grayscale signal, the calibration device is used to calibrate the image luminance meter.

[0042] Furthermore, the calibration device includes: a light source module, which serves as the calibration light source for the image luminance meter, the light source module including an integrating sphere and a wavelength-tunable LED light source disposed within the integrating sphere; a feedback module for monitoring the LED light source and obtaining the standard luminance and chromaticity values ​​of the LED light source; and a processing module for generating a luminance calibration file, a chromaticity calibration file, and an automatic calibration recognition factor using the image luminance meter calibration method as described in any one of claims 1 to 8.

[0043] This application also provides an image brightness measurement system, including:

[0044] An image luminance meter is used to detect the brightness and chromaticity of a target. The image luminance meter includes a photosensitive array. In response to the light received by the image luminance meter, any photosensitive unit in the photosensitive array outputs a set of three-channel grayscale signals. A processing module receives the three-channel grayscale signals output by the image luminance meter.

[0045] Furthermore, the processing module stores a luminance calibration file, a chromaticity calibration file, and an automatic calibration recognition factor generated using the calibration method of the image luminance meter as described in any one of claims 1 to 8;

[0046] The processing module calculates the automatic calibration recognition factor based on the three-channel grayscale signal output by the image luminance meter, and calls the corresponding luminance calibration file and chrominance calibration file according to the automatic calibration recognition factor;

[0047] The processing module combines the three-channel grayscale signals output by the image luminance meter with the called luminance calibration file and chrominance calibration file respectively to obtain the luminance measurement value and chrominance measurement value of the target under test by the image luminance meter.

[0048] In summary, the image luminance meter was calibrated using the calibration method described above. The calibrated image luminance meter effectively reduces measurement errors when testing LED light sources, ensuring its measurement accuracy and thus enabling precise measurement of LED light sources. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the image luminance meter and calibration device in the embodiments of this application;

[0050] Figure 2 This is a schematic diagram of the calibration device in the embodiments of this application;

[0051] Figure 3 This is a flowchart illustrating the calibration process of the image luminance meter in the embodiments of this application;

[0052] Figure 4 This is a flowchart illustrating the three-channel grayscale signal calibration of the image luminance meter in the embodiments of this application;

[0053] Figure 5 This is a flowchart illustrating the brightness calibration process of the image luminance meter in the embodiments of this application;

[0054] Figure 6 This is a flowchart illustrating the colorimetric calibration process of an image luminance meter in an embodiment of this application. Detailed Implementation

[0055] The present application will be described in detail below with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application. Any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the protection scope of the present application.

[0056] like Figure 1 and Figure 2As shown, this application provides a calibration device 200 for an image luminance meter 100. The image luminance meter 100 includes a photosensitive array 11 and a filter unit 12. The filter unit 12 can be an RGB filter unit or an XYZ filter unit. The photosensitive array 11 includes at least one photosensitive unit 111. The photosensitive array 11 is responsive to the image luminance meter 100 receiving light, and any photosensitive unit 111 in the photosensitive array 11 can output a three-channel grayscale signal.

[0057] As one implementation, the calibration device 200 is used to calibrate the image luminance meter 100. The calibration device 200 includes a light source module 21, a feedback module 23, and a processing module 24.

[0058] The light source module 21 serves as the calibration light source for the image luminance meter 100, and is capable of outputting light to the image luminance meter 100. The light source module 21 includes an integrating sphere 211 and an LED light source 212, wherein the LED light source 212 is disposed within the integrating sphere 211 and the wavelength of the output light can be adjusted.

[0059] Feedback module 23 is connected to light source module 21 and can monitor LED light source 212 within light source module 21. When light source module 21 outputs light, feedback module 23 can acquire the standard luminance value L and standard chromaticity value S of LED light source 212 within light source module 21. Processing module 24 is connected to feedback module 23 and also to image luminance meter 100. During the calibration process of image luminance meter 100, processing module 24 can generate luminance calibration file, chromaticity calibration file, and automatic calibration recognition factor, thereby achieving the calibration of image luminance meter.

[0060] As an optional implementation, the feedback module 23 can be a spectroradiometer. Specifically, a small hole can be made in the side wall of the integrating sphere 211, and the light inside the integrating sphere 211 can be transmitted to the feedback module 23 through an optical fiber, so that the standard luminance value L and standard chromaticity value S of the LED light source 212 can be fed back synchronously when calibrating the image luminance meter 100.

[0061] Understandably, calibrating the image luminance meter 100 using the calibration device 200 can reduce the error of the image luminance meter 100 when testing the LED light source 212 and ensure the accuracy of the image luminance meter 100 when measuring the LED light source 212.

[0062] like Figure 3 As shown, as one implementation, this application also provides a calibration method for an image luminance meter 100, used to calibrate the image luminance meter 100. The calibration method includes the following steps:

[0063] S1. A wavelength-tunable LED light source 212 is used as the calibration light source for the image luminance meter 100. The light emitted by the LED light source 212 is filtered by the light filtering unit 12 to form monochromatic light, which is received by the image luminance meter 100.

[0064] S2. Set the exposure time T for the image luminance meter 100, acquire multiple sets of three-channel grayscale signals RGB output by each photosensitive unit 111 when the image luminance meter 100 receives monochromatic light, compare each set of three-channel grayscale signals RGB, obtain the non-uniform calibration coefficient K, and use the non-uniform calibration coefficient K to calibrate each set of three-channel grayscale signals RGB so that the deviation of each set of three-channel grayscale signals R1G1B1 after calibration is within a preset range.

[0065] S3. Acquire the calibrated three-channel grayscale signal R1G1B1 and the standard brightness value L of the LED light source 212. Based on the calibrated three-channel grayscale signal R1G1B1 and the standard brightness value L, obtain the brightness response function of the photosensitive unit 111 for the monochromatic light. Combine the brightness response functions of each photosensitive unit 111 for the monochromatic light to generate the brightness calibration file of the image luminance meter 100 for the monochromatic light.

[0066] S4. Obtain the standard chromaticity value S of the LED light source 212. Based on the calibrated three-channel grayscale signal R1G1B1, the standard luminance value L of the LED light source 212, and the standard chromaticity value S, obtain the chromaticity response value of the photosensitive unit 111 to the monochromatic light. Combine the chromaticity response values ​​of each photosensitive unit 111 to the monochromatic light to generate the chromaticity calibration file of the image luminance meter 100 for the monochromatic light.

[0067] S5. Generate an automatic calibration recognition factor based on the proportional relationship of the three-channel grayscale signals of monochromatic light, and associate the automatic calibration recognition factor with the luminance calibration file and the chrominance calibration file.

[0068] S6. Change the monochromatic light received by the image luminance meter 100, and repeat S2 to S5 until the automatic calibration identification factor of all monochromatic light is obtained, and associate the automatic calibration identification factor with the luminance calibration file and the chromaticity calibration file.

[0069] Specifically, the LED light source 212 inside the light source module 21 is activated, enabling the light source module 21 to output light to the image luminance meter 100. The positions of the light source module 21 and the image luminance meter 100 are adjusted so that the center of the image luminance meter 100 is aligned with the center of the light source module 21, ensuring that the light output by the light source module 21 can clearly illuminate the image luminance meter 100.

[0070] Furthermore, the image luminance meter 100 is activated, and the processing module 24 acquires the three-channel grayscale signals RGB of each photosensitive unit 111 when the photosensitive array 11 receives monochromatic light. The processing module 24 compares the three-channel grayscale signals RGB of each photosensitive unit 111 to obtain a non-uniformity coefficient K. The processing module 24 uses the non-uniformity coefficient K to calibrate the three-channel grayscale signals RGB of each photosensitive unit 111, ensuring that the deviation between the three-channel grayscale signals R1G1B1 of each photosensitive unit 111 is within a preset range after calibration. This achieves the calibration of the three-channel grayscale signals RGB of the photosensitive array 11.

[0071] Furthermore, when the light source module 21 outputs light, the feedback module 23 acquires the standard brightness value L of the LED light source 212 at this time and sends the standard brightness value L to the processing module 24. The processing module 24 obtains the brightness response function of each photosensitive unit 111 for the monochromatic light based on the calibrated three-channel grayscale signal R1G1B1 of each photosensitive unit 111 and the standard brightness value L of the LED light source 212. The processing module 24 integrates the brightness response functions of each photosensitive unit 111 to obtain the brightness calibration file of the image luminance meter 100 for the monochromatic light.

[0072] Furthermore, when the light source module 21 outputs light, the feedback module 23 acquires the standard chromaticity value S of the LED light source 212 at this time and sends the standard chromaticity value S to the processing module 24. The processing module 24 calculates the chromaticity response value of each photosensitive unit 111 based on the calibrated three-channel grayscale signal R1G1B1 of each photosensitive unit 111, the standard luminance value L of the LED light source 212, and the standard chromaticity value S of the LED light source 212, thereby obtaining the chromaticity response value of each photosensitive unit 111. The processing module 24 processes the chromaticity response value of each photosensitive unit 111 to obtain the chromaticity calibration file of the image luminance meter 100 for the monochromatic light.

[0073] Further, the processing module 24 calculates the ratio of the three-channel grayscale signals R1G1B1 of the calibrated monochromatic light to obtain the proportional relationship of the three-channel grayscale signals. This proportional relationship is the automatic calibration recognition factor of the monochromatic light. The processing unit associates the automatic calibration recognition factor of the monochromatic light, the brightness calibration file of the monochromatic light, and the chromaticity calibration file of the monochromatic light to achieve the calibration of the monochromatic light by the image luminance meter 100.

[0074] Understandably, by changing the monochromatic light output by the light source module 21, the image luminance meter 100 can receive different monochromatic lights. By calibrating each monochromatic light, the three-channel grayscale signal, luminance, and chromaticity of the image luminance meter 100 can be calibrated, thereby reducing the error of the image luminance meter 100 when testing the LED light source 212 and ensuring the accuracy of the image luminance meter 100 when measuring the LED light source 212.

[0075] like Figure 4 As shown, as one implementation method, calibrating the three-channel grayscale signal of the photosensitive array 11 includes the following steps:

[0076] S21. Divide the photosensitive array 11 of the image luminance meter 100 into regions, and obtain the average gray value of any channel in each region based on the multiple sets of three-channel gray signals output by each photosensitive unit 111 in each region.

[0077] S22. Calculate the ratio of the average grayscale signal of any channel in the remaining areas to the average grayscale signal of the corresponding channel in the central area of ​​the photosensitive array 11, so as to obtain the non-uniform calibration coefficient K of any channel in each area.

[0078] S23. Using the average grayscale signal of each channel in the central region of the photosensitive array 11 as the standard grayscale data, calculate the offset of each channel grayscale signal data of each photosensitive unit 111 in the other regions after calibration by the non-uniform calibration coefficient relative to the standard grayscale data.

[0079] S24. Determine whether the offset is greater than a preset threshold. If the offset is greater than the preset threshold, re-divide the photosensitive array 11 into regions and recalibrate the three-channel grayscale signals of the photosensitive array. Calculate the offset of the photosensitive array after calibration.

[0080] S25, until the offset of the photosensitive array is less than the preset threshold, then the calibration of the three-channel grayscale values ​​of the photosensitive array is completed.

[0081] Specifically, the processing module 24 divides the photosensitive array 11 of the image luminance meter 100 into multiple regions. When the image luminance meter 100 receives light, the processing module 24 acquires the R-channel grayscale value of each photosensitive unit 111 and calculates the average value R of the R-channel grayscale value of the photosensitive units 111 in each region.

[0082] Further, processing module 24 calculates the average R value of the R channel grayscale value in the intermediate region. a The non-uniformity coefficient K of the R-channel grayscale value for each region can be obtained by comparing it with the average value R of the R-channel grayscale value for all regions. R .

[0083] Understandably, processing module 24 repeats the above operation to obtain the non-uniformity coefficient K of the G channel grayscale value for each region. G The non-uniformity coefficient K of the B channel grayscale value B Processing module 24 calculates the aforementioned non-uniformity coefficient K. R K G and K BThe product of the grayscale value of the corresponding channel in each region is used to scale the three-channel grayscale signal of each region proportionally, thereby achieving calibration of the three-channel grayscale signal of each region.

[0084] Furthermore, the processing module 24 reacquires the three-channel grayscale signals RGB of the photosensitive unit 111 in each region after calibration, and obtains the average value of the three-channel grayscale signals in each region. Processing module 24 calculates the average value R of the three-channel grayscale signal in the central region. a G a B a With each

[0085] Average value of three-channel grayscale signal in the region The difference C is calculated. When the difference C is greater than a preset threshold, the processing module 24 re-divides the photosensitive array 11 into regions and recalibrates the three-channel grayscale signal values ​​of each region after division. The processing module 24 calculates the average value R of the three-channel grayscale signal in the central region after recalibration. a G a B a Average of the three-channel grayscale signal in each region The difference is calculated until the difference C is less than the preset threshold, at which point the calibration of the three-channel grayscale values ​​RGB of the photosensitive array 11 is completed.

[0086] When measuring LED light sources, the image luminance meter 100 suffers from a strong vignetting effect on the image plane due to the short focal length imaging objective lens. This causes pixel response values ​​to attenuate radially from the detector center, resulting in non-uniform responses in pixel areas far from the optical axis center of the photosensitive array target surface. Furthermore, the individual photosensitive units 111 within the photosensitive array may exhibit inconsistent responsivity to uniform light sources. This application calibrates the three-channel grayscale values ​​(RGB) of the photosensitive array 11 in the image luminance meter 100, overcoming the problem of non-uniform response to uniform light sources. This avoids affecting luminance and chromaticity measurements and improves measurement accuracy.

[0087] like Figure 5 As shown, as one implementation method, obtaining the brightness response function of the image luminance meter 100 to monochromatic light includes the following steps:

[0088] S31. Obtain the standard brightness value L of LED light source 212, the exposure time T of image luminance meter 100, and the average value R of the three-channel grayscale signal in the central region of photosensitive array 11. a G a B a .

[0089] S32. Based on the exposure time T of the image luminance meter 100 and the average value R of the three-channel grayscale signal in the central region of the photosensitive array 11... a G a B a Obtain the average value R of the three-channel grayscale signal per unit time. T G T B T .

[0090] S33. Based on the average value R of the three-channel grayscale signals per unit time. T G T B T Calculate the average brightness response value of the image luminance meter over 100 units of time.

[0091] S34. Fit the standard luminance value L and the average luminance response value per unit time to obtain the luminance response function of monochromatic light.

[0092] Specifically, when the image luminance meter 100 is turned on, the exposure time T of the image luminance meter 100 by the light source module 21 is set, and the processing module 24 acquires this exposure time T. The processing module 24 acquires the three-channel grayscale signal value R of the central region of the calibrated photosensitive array 11. a G a B a The ratio of the average value R of the three-channel grayscale signal per unit time is obtained by comparing it with the exposure time T. T G T B T .

[0093] Furthermore, the processing unit calculates the average value R of the three channels per unit time. T G T B T The average brightness response value per unit time is obtained. Specifically, when the filter unit 12 is an RGB filter unit, the processing module 24 calculates the average brightness response value per unit time using the following formula:

[0094] DN = 0.299R + 0.587G + 0.114B

[0095] In the formula, DN represents the average brightness response value per unit time, R represents the average value of channel R per unit time, G represents the average value of channel G per unit time, and B represents the average value of channel B per unit time.

[0096] Furthermore, when the filter unit 12 is an XYZ filter unit, the processing module 24 calculates the average brightness response per unit time using the following formula:

[0097] DN=G

[0098] In the formula, DN represents the average brightness response value per unit time, and G represents the average value of G channels per unit time.

[0099] Furthermore, the feedback module 23 acquires the standard brightness value L of the LED light source 212 within the light source module 21 and transmits this standard brightness value L to the processing module 24. The processing module 24 fits the standard brightness value L of the LED light source 212 with the average brightness response value DN per unit time to obtain the brightness response function of the image luminance meter 100 for this monochromatic light. The standard brightness value and the average brightness response value per unit time can be fitted using MATLAB. To ensure accuracy and reduce computational load, a piecewise fitting method can be employed.

[0100] As one implementation, by adjusting the brightness of the LED light source 212 within the light source module 21, the processing module 24 can obtain the brightness response function of the image luminance meter 100 for the monochromatic light under different brightness levels. The processing module 24 integrates the brightness response functions of the monochromatic light under different brightness levels to obtain a brightness calibration file for the monochromatic light by the image luminance meter 100, thereby achieving brightness calibration of the monochromatic light by the image luminance meter 100.

[0101] Understandably, by changing the monochromatic light output by the light source module 21, the monochromatic light received by the image luminance meter 100 can be changed. Through the above steps, the processing module 24 can obtain the luminance calibration file of the image luminance meter 100 under different monochromatic lights, thereby realizing the luminance calibration of the image luminance meter 100. When the image luminance meter 100 tests the LED light source 212, the luminance error when the image luminance meter 100 tests the LED light source 212 is effectively reduced, ensuring the accuracy of the image luminance meter 100 in measuring the LED light source 212.

[0102] like Figure 6 As shown, in one implementation, when the filter unit 12 is an RGB filter unit, obtaining the chromaticity response value of the image luminance meter 100 to monochromatic light includes the following steps:

[0103] S41. Obtain the standard luminance value L of LED light source 212, the standard chromaticity value S of LED light source 212, and the exposure time T of image luminance meter 100.

[0104] S42. Obtain the tristimulus values ​​based on the standard chromaticity value S and the standard luminance value L.

[0105] S43. Obtain the three-channel grayscale signal value R of the central region of the calibrated photosensitive array 11. a G a B a Based on the three-channel grayscale signal R of the central region of the calibrated photosensitive array 11 a G a Ba The exposure time T of the image luminance meter 100 is used to obtain the average value R of the three channels per unit time. T G T B T .

[0106] S44. Based on the average value of the three channels per unit time, R T G T B T By comparing the values ​​with the tristimulus values, the chromaticity response values ​​of each channel grayscale signal are obtained to generate the chromaticity calibration file of the monochromatic light.

[0107] Specifically, the image luminance meter 100 is turned on, and the exposure time T of the light source module 21 to the image luminance meter 100 is set. The processing module 24 obtains this exposure time T. When the filter unit 12 is an RGB filter unit, the feedback module 23 obtains the standard luminance value L and the standard chromaticity value S of the LED light source 212 in the light source module 21 at this time, and sends them to the processing module 24.

[0108] Furthermore, the processing module 24 calculates the tristimulus value X based on the standard luminance value L and the standard chromaticity value S of the LED light source 212 using the following formula. i Y i Z i The calculation formula is:

[0109]

[0110] In the formula x i y i z i The standard chromaticity values ​​S and Y of LED light source 212 are... i Let L be the standard luminance value of LED light source 212. X can be calculated using the above formula. i With Z i This leads to the tristimulus value X. i Y i Z i .

[0111] Furthermore, processing module 24 calculates the tristimulus value X. i Y i Z i The product of the tristimulus values ​​X and the matrix coefficients A can be used to transform the tristimulus values ​​X. i Y i Z i Converted to tristimulus value R i G i B i The matrix coefficients A are represented as follows:

[0112]

[0113] Furthermore, the processing module 24 acquires the three-channel grayscale signal value R of the central region of the calibrated photosensitive array 11. a G a B a And calculate the grayscale signal value R of the three channels. a G a B a The ratio of the exposure time T to the average value R of the three channels per unit time is obtained. T G T B T Processing module 24 processes the tristimulus values ​​R... i G i B i R, the average value of three channels per unit time T G T B T The monochromatic light chromaticity response value K is calculated using the following formula. rr K rg K rb The calculation formula is as follows:

[0114]

[0115] It should be noted that when the filter unit 12 is an XYZ filter, the processing module 24 calculates the tristimulus value X based on the standard luminance value L and the standard chromaticity value S of the LED light source 212. i Y i Z i Processing module 24 processes the tristimulus value X... i Y i Z i R, the average value of three channels per unit time T G T B T The monochromatic light chromaticity response value K is calculated using the following formula. rr K rg K rb The calculation formula is as follows:

[0116]

[0117] Processing module 24 integrates the chromaticity response values ​​K of each channel under the monochromatic light. rr K rg K rb This allows us to obtain the chromaticity calibration file of the image luminance meter 100 for the monochromatic light.

[0118] Understandably, by changing the monochromatic light output by the light source module 21, the monochromatic light received by the image luminance meter 100 is also changed. Through the above operations, the processing module 24 can obtain chromaticity calibration files for different monochromatic lights, thereby calibrating the chromaticity of the image luminance meter 100. When the image luminance meter 100 tests the LED light source 212, this effectively reduces the chromaticity error during testing, ensuring the accuracy of the image luminance meter 100 in measuring the LED light source 212.

[0119] This application also provides an image brightness measurement system, including an image brightness meter 100 and a processing module 24. The image brightness meter 100 is used to detect the brightness and chromaticity of the target. The image brightness meter 100 includes a photosensitive array 11. In response to the image brightness meter 100 receiving light, any photosensitive unit 111 in the photosensitive array 11 outputs a set of three-channel grayscale signals. The processing module 24 receives the three-channel grayscale signals output by the image brightness meter 100.

[0120] In one implementation, processing module 24 stores a luminance calibration file, a chrominance calibration file, and an automatic calibration recognition factor. When the image luminance meter 100 tests the LED light source 212 under test, processing module 24 obtains the three-channel grayscale signals under test through the image luminance meter 100. Processing module 24 calculates the ratio between the three-channel grayscale signals under test to obtain the proportional relationship between them. Processing module 24 obtains the automatic calibration recognition factor stored in its own memory through this proportional relationship, and then calls the luminance calibration file and chrominance calibration file associated with the automatic calibration recognition factor.

[0121] Furthermore, the processing module 24 combines the three-channel grayscale signal with the luminance calibration file called by the processing module 24, and at the same time, the processing module 24 combines the three-channel grayscale signal with the chromaticity calibration file called by the processing module 24 to obtain the luminance measurement value and chromaticity measurement value of the LED light source 212 under test, effectively reducing the error of the image luminance meter 100 when testing the LED light source 212 and ensuring the accuracy of the image luminance meter 100 when measuring the LED light source 212.

[0122] This application embodiment uses a calibrated image luminance meter 100 to measure the chromaticity of red light, green light, and blue light at different brightness levels, obtaining the following three-color luminance and chromaticity measurement table:

[0123]

[0124]

[0125] In this embodiment, a calibrated image luminance meter 100 is used to measure the white light generated by the combination, thereby obtaining the following luminance and chromaticity measurement table:

[0126]

[0127] Wherein, standard x and standard y are the standard chromaticity coordinates of the light ray, and measured x and measured x are the measured chromaticity coordinates of the light ray. It can be understood that the calibrated image luminance meter 100 can accurately measure the luminance and chromaticity of the light ray under test. It should be noted that the above luminance and chromaticity measurement table only describes the measurement results of the luminance and chromaticity of the light ray in this embodiment of the application and is not intended to limit this application.

[0128] In summary, the image luminance meter 100 was calibrated using the calibration method described above. The calibrated image luminance meter 100 effectively reduces measurement errors and ensures measurement accuracy when testing the LED light source 212, thus achieving precise measurement of the LED light source 212 by the image luminance meter 100.

[0129] The above-disclosed embodiments are merely preferred embodiments of this application, but are not intended to limit the scope of this application. Those skilled in the art will understand that any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and scope of this application and the appended claims are equivalent substitutions and still fall within the scope of the invention.

Claims

1. A calibration method for an image luminance meter, the image luminance meter comprising a filter unit and a photosensitive array, wherein, in response to the image luminance meter receiving light, any photosensitive unit in the photosensitive array outputs a set of three-channel grayscale signals, characterized in that, The method includes the following steps: A wavelength-tunable LED light source is used as the calibration light source for the image brightness meter. The light emitted by the LED light source is filtered by the filter unit to form monochromatic light, which is received by the image brightness meter. The exposure time of the image luminance meter is set, and multiple sets of three-channel grayscale signals output by each of the photosensitive units when the image luminance meter receives the monochromatic light are obtained. The sets of three-channel grayscale signals are compared to obtain a non-uniform calibration coefficient. The non-uniform calibration coefficient is used to calibrate each set of three-channel grayscale signals so that the deviation of each set of three-channel grayscale signals after calibration is within a preset range. The calibrated three-channel grayscale signal is acquired, and the standard brightness value of the LED light source is acquired. Based on the calibrated three-channel grayscale signal and the standard brightness value, the brightness response function of the photosensitive unit for the monochromatic light is obtained. The brightness response functions of each photosensitive unit for the monochromatic light are combined to generate the brightness calibration file of the image luminance meter for the monochromatic light. Obtain the standard chromaticity value of the LED light source. Based on the calibrated three-channel grayscale signal, the standard luminance value and standard chromaticity value of the LED light source, obtain the chromaticity response value of the photosensitive unit for the monochromatic light. Combine the chromaticity response values ​​of each photosensitive unit for the monochromatic light to generate the chromaticity calibration file of the image luminance meter for the monochromatic light. An automatic calibration recognition factor is generated based on the proportional relationship of the three-channel grayscale signals of the monochromatic light, and the automatic calibration recognition factor is associated with the luminance calibration file and the chrominance calibration file; The calibration of the three-channel grayscale signals in each group includes the following steps: The photosensitive array of the image luminance meter is divided into regions. Based on the multiple sets of three-channel grayscale signals output by each photosensitive unit in each region, the average grayscale signal of any channel in that region is obtained. Calculate the ratio of the mean grayscale signal of any channel in the remaining regions to the mean grayscale signal of the corresponding channel in the central region of the photosensitive array, to obtain the non-uniform calibration coefficient of any channel in each region. Using the average grayscale signal of each channel in the central region of the photosensitive array as the standard grayscale data, the offset of each channel grayscale signal data of each photosensitive unit in the remaining regions after calibration by the non-uniform calibration coefficient relative to the standard grayscale data is calculated. When the offset is greater than a preset threshold, the photosensitive array is re-divided into regions until the offset is less than the preset threshold.

2. The calibration method according to claim 1, characterized in that, Obtaining the luminance response function of the image luminance meter to monochromatic light includes the following steps: Obtain the standard brightness value of the LED light source, the exposure time of the image luminance meter, and the average value of the three-channel grayscale signal in the central region of the photosensitive array; The average value of the three channels per unit time is obtained based on the exposure time of the image luminance meter and the average value of the three-channel grayscale signal in the central region of the photosensitive array. Calculate the average brightness response value of the image luminance meter per unit time based on the average value of the three channels per unit time. The brightness response function of the monochromatic light is obtained by fitting the standard brightness value and the average brightness response value per unit time.

3. The calibration method according to claim 2, characterized in that, When the filter unit is an RGB filter unit, the average brightness response value per unit time is calculated according to the following formula: DN = 0.299R + 0.587G + 0.114B In the formula, DN represents the average brightness response value per unit time, R represents the average value of channel R per unit time, G represents the average value of channel G per unit time, and B represents the average value of channel B per unit time.

4. The calibration method according to claim 2, characterized in that, When the filter unit is an XYZ filter unit, the average brightness response value per unit time is calculated according to the following formula: DN=G, In the formula, DN represents the average brightness response value per unit time, and G represents the average value of G channels per unit time.

5. The calibration method according to claim 2, characterized in that, The method further includes: The brightness of the LED light source is adjusted to obtain the brightness response function of each photosensitive unit for the monochromatic light under different brightness levels, so as to generate a brightness calibration file of the image luminance meter for the monochromatic light under different brightness levels.

6. The calibration method according to claim 1, characterized in that, When the filter unit is an RGB filter unit, obtaining the chromaticity response value of the image luminance meter to the monochromatic light includes the following steps: Obtain the standard brightness value of the LED light source, the standard chromaticity value of the LED light source, and the exposure time of the image luminance meter; The tristimulus values ​​are obtained based on the standard chromaticity values ​​and the standard luminance values; Convert the tristimulus values ​​to RGB values; The three-channel grayscale signal of the central region of the calibrated photosensitive array is obtained, and the average value of the three channels per unit time is obtained based on the three-channel grayscale signal of the central region of the calibrated photosensitive array and the exposure time of the image luminance meter. By comparing the average value of the three channels within the unit time with the RGB value converted from the tristimulus value, the chromaticity response value of the grayscale signal of each channel is obtained, so as to generate the chromaticity calibration file of the monochromatic light.

7. The calibration method according to claim 1, characterized in that, When the filter unit is an XYZ filter unit, obtaining the chromaticity response value of the image luminance meter to the monochromatic light includes the following steps: Obtain the standard brightness value of the LED light source, the standard chromaticity value of the LED light source, and the exposure time of the image luminance meter; The tristimulus values ​​are obtained based on the standard chromaticity values ​​and the standard luminance values; The three-channel grayscale signal of the central region of the calibrated photosensitive array is obtained, and the average value of the three channels per unit time is obtained based on the three-channel grayscale signal of the central region of the calibrated photosensitive array and the exposure time of the image luminance meter. By comparing the average value of the three channels within the unit time with the tristimulus value, the chromaticity response value of the grayscale signal of each channel is obtained, so as to generate the chromaticity calibration file of the monochromatic light.

8. A calibration device for an image luminance meter, the image luminance meter comprising a photosensitive array, wherein, in response to the image luminance meter receiving light, any photosensitive unit in the photosensitive array outputs a three-channel grayscale signal, the calibration device being used to calibrate the image luminance meter, characterized in that, The calibration device includes: A light source module, which serves as the calibration light source for the image luminance meter, includes an integrating sphere and a wavelength-tunable LED light source disposed within the integrating sphere. The feedback module is used to monitor the LED light source and obtain the standard brightness and chromaticity values ​​of the LED light source; The processing module uses the image luminance meter calibration method as described in any one of claims 1 to 7 to generate a luminance calibration file, a chromaticity calibration file, and an automatic calibration recognition factor.

9. An image brightness measurement system, comprising: An image luminance meter is used to detect the luminance and chromaticity of a target. The image luminance meter includes a photosensitive array. In response to receiving light, any photosensitive unit in the photosensitive array outputs a set of three-channel grayscale signals. The processing module receives the three-channel grayscale signal output by the image luminance meter; Its features are, The processing module stores a luminance calibration file, a chromaticity calibration file, and an automatic calibration recognition factor generated using the image luminance meter calibration method described in any one of claims 1 to 7. The processing module calculates the automatic calibration recognition factor based on the three-channel grayscale signal output by the image luminance meter, and calls the corresponding luminance calibration file and chrominance calibration file based on the automatic calibration recognition factor; The processing module combines the three-channel grayscale signal output by the image luminance meter with the called luminance calibration file and chrominance calibration file respectively to obtain the luminance measurement value and chrominance measurement value of the target to be measured by the image luminance meter.

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