An image correction coefficient generation and update method

Abstract

The application relates to an image correction coefficient generation and updating method, and relates to the technical field of image correction coefficient processing, and solves the problem that, when gain parameter values, integral stage values, pixel sizes and push scanning directions of a detector are mapped in four dimensions, correction coefficients are huge and difficult to store. According to a solidified storage area and forward and reverse scanning dimensions, the method divides a limited storage area into four uniform sub-areas; determines the number of correction coefficients that can be stored in a single sub-area; and determines the number of selectable gain grades and TDI integral stages. In the method, the gain and integral stage in the current storage area are updated by uploading, the mapping relationship between each gain grade and gain value is changed, the mapping relationship between each gain grade and stage value is changed, the number of stage grades under the gain grade and the corresponding stage values, and each gain value and each stage value can be changed by uploading. The method meets various application requirements.

Description

Technical Field

[0001] This invention relates to the field of image correction coefficient processing technology, specifically to a method for generating and updating image correction coefficients based on fine correction applications. Background Technology

[0002] Because changing the detector gain alters the detector's response curve, the non-uniformity correction coefficients of TDI cameras typically vary with the gain parameter value. Changes in detector pixel size also lead to changes in response characteristics, requiring corresponding adjustments to the correction coefficients. However, changes in the integration level and sweep direction do not affect the correction coefficients. For fine-grained correction applications, the number of photosensitive pixel rows applied by a TDI detector varies with different integration levels; even with the same integration level, the applied photosensitive pixel row area differs under different scanning directions, resulting in subtle differences in response. Mapping the detector's gain parameter value, integration level value, pixel size, and sweep direction along four dimensions results in a massive number of correction coefficients, posing a significant storage challenge. Summary of the Invention

[0003] This invention provides a method for generating and updating image correction coefficients, which solves the problem in the prior art that when mapping the detector gain parameter value, integral level value, pixel size, and push-broom direction in four dimensions, the correction coefficients are huge and difficult to store.

[0004] A method for generating and updating image correction coefficients, the specific implementation process of which is as follows:

[0005] Based on the solidified storage area and the forward and reverse scan dimensions, the storage area in MRAM is divided into four uniform sub-regions;

[0006] The number of correction coefficient groups stored in a single sub-region is determined based on the number of pixels and the bit width of the correction data in different spectral bands and operating modes of the detector.

[0007] The number of selectable gain levels and the number of TDI integration stages are determined based on the number of correction coefficient groups stored in a single sub-region;

[0008] The above update the gain and TDI integral level in the current storage area, changes the mapping relationship between each gain level and gain value, and changes the mapping relationship between each gain level and level value.

[0009] The beneficial effects of this invention are:

[0010] 1. In the method described in this invention, the limited storage area is divided into 4 uniform sub-regions according to the solidified storage area and the forward and reverse scan dimensions, covering operations that include forward and reverse scans in actual applications, as well as parameter areas where the state remains unchanged and areas that are adjusted according to application requirements.

[0011] 2. The present invention determines the number of correction coefficient groups that can be stored in a single sub-region based on the number of pixels and correction data bit width in different working modes and spectral bands. This is conducive to maximizing the number of correction coefficient groups and achieving a fine correction effect.

[0012] 3. In this method, the number of selectable gain levels and the number of TDI integration stages are determined based on the number of correction coefficient groups that can be stored in a single sub-region, so as to minimize the dynamic range loss caused by non-uniform correction while prioritizing the image signal-to-noise ratio.

[0013] 4. In this method, based on application requirements, the gain and integral levels in the current storage area are updated via betting, changing the mapping relationship between each gain level and gain value, and changing the mapping relationship between each gain level and level value. The number of level levels and corresponding level values ​​under each gain level can be changed in real time via betting; the values ​​of each level can also be changed via betting. In this way, multiple working modes and application scenarios can be switched using limited storage resources to meet various application requirements. Attached Figure Description

[0014] Figure 1 This is a block diagram of the imaging system of the detector described in this invention.

[0015] Figure 2 This is a schematic diagram of the gain settings.

[0016] Figure 3 The diagram shows the corresponding principle of the integral series levels. Detailed Implementation

[0017] Combination Figures 1 to 3 This embodiment describes an image correction coefficient generation and update method, which is implemented through the imaging system of the detector. The imaging system includes a camera controller, an imaging controller power supply chip, an imaging controller, a detector power supply chip, a multi-band detector, erasable main and backup flash memory, PROM, MRAM, a cameralink chip, a cameralink connector, a 2711 chip, and a 2711 connector.

[0018] The camera controller receives a primary power supply from an external source and generates the necessary power supplies. It also receives a second pulse from an external source and communicates with the outside world via a 1553 bus. The camera controller communicates with the imaging controller via a 422 communication signal and provides the imaging controller with the second pulse, supplying power to the imaging controller through its power supply chip. The imaging controller provides drive control signals to the multispectral detector and supplies power to the multispectral detector through its detector power supply chip, receiving serial image data output from the multispectral detector. The imaging controller is connected to both a configuration data source PROM and erasable primary / backup flash memory, and is also connected to MRAM for updating correction coefficients and loading correction coefficients before each image capture. The imaging controller can output image data either via a CameraLink chip and CameraLink connector, or via a 2711 chip and 2711 connector, depending on the desired method.

[0019] The specific process of this method is as follows:

[0020] 1. Based on the fixed storage area and the forward and reverse scan dimensions, the finite storage area in MRAM is divided into four uniform sub-regions;

[0021] 2. Based on the number of pixels β in different spectral bands and different working modes τυ The number of correction coefficient sets α that can be stored in a single sub-region is determined by the correction data bit width δ; the formula is:

[0022]

[0023] In the formula, This refers to the size of the storage area in MRAM; τυ This represents different working modes. For example, a value of 0 represents the maximum number of pixels, and a value of 1 represents half of the maximum number of pixels.

[0024] 3. Determine the selectable gain level n and the number of TDI integration stages m based on the number of correction coefficient groups that can be stored in a single sub-region;

[0025] The method for determining the TDI integral level range is based on the low-end conditions, typical conditions, and high-end conditions determined according to the integral level range.

[0026] In this embodiment, the low-end condition is: satisfying the minimum signal-to-noise ratio (SNR) of the specified reflectivity target. 低端 The requirements are that the image of the high-reflectivity target and surrounding objects should not be saturated; under the condition of minimizing the minimum gain value and integral series allowed by the detector manual, the image grayscale values ​​of the high-reflectivity target and surrounding objects should be specified as DN. 指定 and DN 环境Therefore, the integral series allowed under low-end conditions must satisfy the following formula constraint, where m is the number of quantization bits and γ is the conversion coefficient from electron to DN value. The DN value under low-end conditions is DN. 低端 The image grayscale value DN of the target with a specified reflectivity must be less than or equal to that of the target. 指定 ,

[0027]

[0028] Typical conditions: Meet the specified normal signal-to-noise ratio (SNR) 典型 The requirements are that the image grayscale value does not exceed 1 / 4 of the maximum DN value; under the condition of minimizing the minimum gain value and integration series allowed by the detector manual, the typical image grayscale value is DN. 典型 ;

[0029]

[0030] High-end requirements: Meet the specified maximum signal-to-noise ratio (SNR) 高端 Requirements: Under the condition of minimizing the minimum gain value and integration series allowed by the detector manual, the image grayscale value under high-end conditions should be DN. 高端 ;

[0031]

[0032] In this embodiment, the primary function of the gain is to adjust the response differences between the various detectors, thereby compensating for the gaps in adjustment capability between different levels of the integration stage.

[0033] The ratio factor for each gain level = the gain value of that level / the minimum gain value allowed by the detector manual;

[0034] The ratio of adjacent integral stages = the integral stage value one level larger than the divisor / the minimum integral stage value determined based on the incident light energy or an integral stage value larger than the minimum integral stage value; for example, the ratio has many values, such as ratio 1, ratio 2, ratio 3, etc.;

[0035] The ratio of adjacent TDI integration stages is 1 = the TDI integration stage value that is one step larger than the divisor (the smallest integration stage value determined based on the incident light energy) / the smallest integration stage value determined based on the incident light energy.

[0036] The ratio of adjacent TDI integration stages is 2 = the TDI integration stage value that is one stage larger than the divisor (the integration stage value that is one stage larger than the "minimum integration stage value determined based on incident light energy") / the integration stage value that is one stage larger than the "minimum integration stage value determined based on incident light energy".

[0037] The ratio of adjacent TDI integration stages is 3 = the TDI integration stage value that is one stage larger than the divisor (the integration stage value that is two stages larger than the "minimum integration stage value determined based on incident light energy") / the integration stage value that is two stages larger than the "minimum integration stage value determined based on incident light energy".

[0038] The ratio of adjacent TDI integration stages is 4 = the TDI integration stage value that is one stage larger than the divisor (the integration stage value that is three stages larger than the "minimum integration stage value determined based on incident light energy") / the integration stage value that is three stages larger than the "minimum integration stage value determined based on incident light energy".

[0039] In this embodiment, the selectable gain level n is determined based on the ratio coefficient of each gain level and the ratio of adjacent integral stages, requiring that the ratio coefficient of each gain level is less than or equal to the maximum value of the ratio of adjacent integral stages.

[0040] like Figure 2 and Figure 3 As shown, in this embodiment, according to application requirements, updating the gain and integral levels in the current storage area, changing the mapping relationship between each gain level and gain value, and changing the mapping relationship between each gain level and level value are implemented in two steps.

[0041] Step 1: Select the gain level n, the specific gain value within the gain level, and the number of levels mi within the gain level, i = 1...n.

[0042] Step 2: Input the mi integral stage values ​​corresponding to each gain level.

[0043] The gain level (mi) and its corresponding level value are specified for this gain level. The level values ​​can be changed via the above method. The minimum value of mi is 0, meaning that the gain level is not used. Figure 3 The number of corresponding integral stages is 1m1+2m2+…+nmn; for gain stage 1, the stages within this stage are 11…1m1, and each stage corresponds to an integral stage value; for gain stage 2, the stages within this stage are 21…2m2, and each stage corresponds to an integral stage value; for gain stage n, the stages within this stage are n1…nmn, and each stage corresponds to an integral stage value.

[0044] In this embodiment, the imaging controller power supply chip uses the 510 DCDC module; the multispectral detector uses the area array detector from Changguang Chenxin Company; the camera controller mainly uses a DSP chip; the imaging controller mainly uses the imaging controller and refresh chip from Shanghai Fudan Microelectronics Company; the detector power supply chip mainly uses the LDO from TI Company; the 2711 chip uses the TLK2711 chip; the 2711 connector uses the micro coaxial connector from Sichuan Huafeng; the cameralink chip uses the DS90CR287; the cameralink connector uses the MDR26 connector from 3M Company; the erasable main and backup flash memory uses products from Fudan Microelectronics; the PROM uses products from Xilinx Company; and the MRAM uses products from the 771 Institute.

Claims

1. A method for generating and updating image correction coefficients, characterized in that: The implementation process of this method is as follows: based on the solidified storage area and the forward and reverse scan dimensions, the storage area in the MRAM is divided into four uniform sub-regions; The number of correction coefficient groups stored in a single sub-region is determined based on the number of pixels and the bit width of the correction data in different spectral bands and operating modes of the detector. The number of selectable gain levels and the number of TDI integration stages are determined based on the number of correction coefficient groups stored in a single sub-region; The above update the gain and TDI integral level in the current storage area, changes the mapping relationship between each gain level and gain value, and changes the mapping relationship between each gain level and level value.

2. The method for generating and updating image correction coefficients according to claim 1, characterized in that: Determine the TDI integration stage range: Based on the integration stage range, determine the permissible integration stages for low-end, typical, and high-end conditions; The low-end condition: satisfying the minimum signal-to-noise ratio (SNR) for a specified reflectivity target. 低端 The requirements are that the image of the high-reflectivity target and surrounding objects should not be saturated; under the condition of minimizing the minimum gain value and integral series allowed by the detector manual, the image grayscale values ​​of the high-reflectivity target and surrounding objects should be specified as DN. 指定 and DN 环境 DN value at the low end 低端 The image grayscale value DN of the target with a specified reflectivity must be less than or equal to that of the target. 指定 Then, the number of integral series allowed under low-end conditions is: In the formula, λ is the number of quantization bits, and γ is the conversion coefficient from the number of electron cores to the DN value; The typical condition is: satisfying the conventional signal-to-noise ratio (SNR). 典型 The requirement is that the image grayscale value does not exceed 1 / 4 of the maximum DN value; Under the condition of minimizing the minimum gain value and integration series allowed by the detector manual, the typical image grayscale value is DN. 典型 Under typical conditions, the permissible integral series is: The high-end condition: meets the specified maximum signal-to-noise ratio (SNR). 高端 The requirement is that, under the condition of minimizing the minimum gain value and integration series allowed by the detector manual, the image grayscale value under high-end conditions should be DN. 高端 The number of integral stages allowed under high-end conditions is:

3. The method for generating and updating image correction coefficients according to claim 1, characterized in that: Based on the number of pixels β in different spectral bands and different operating modes of the detector τυ The number of correction coefficient sets α that can be stored in a single sub-region is determined by the correction data bit width δ, and is expressed by the following formula: In the formula, The size of the storage area; τυ For different work modes.

4. The method for generating and updating image correction coefficients according to claim 1, characterized in that: The ratio factor for each gain level = the gain value of that level / the minimum gain value allowed by the detector manual; The ratio of adjacent TDI integration stages = TDI integration stage value one level larger than the divisor / minimum integration stage value determined based on incident light energy or TDI integration stage value larger than the minimum integration stage value; The selectable gain level n is determined by the ratio factor of each gain level and the ratio of adjacent TDI integration stages. It is required that the ratio factor of each gain level is less than or equal to the maximum value of the ratio of adjacent TDI integration stages.

5. The method for generating and updating image correction coefficients according to claim 1, characterized in that: The process of updating the gain and integral levels in the current storage area, changing the mapping relationship between each gain level and gain value, and changing the mapping relationship between each gain level and level value is achieved in two steps. Step 1: Add the gain level n, the specific gain value within the gain level, and the number of levels within the gain level as mi, i = 1...n; Step 2: Add the values ​​of mi TDI integral stages corresponding to the n-level gain. The number of stages mi under this gain level and the corresponding stage values ​​are changed by adding the values ​​of each stage.

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