Infrared imaging signal processing method based on digital detector

Abstract

The invention relates to an infrared imaging signal processing method based on a digital detector, and the method comprises the following steps: carrying out the parallel data of four channels of an upper half part and four channels of a lower half part, carrying out the independent sampling of each channel, after the verification is passed, writing the data into an independent channel cache, reading the pixel data from the cache in sequence, forming an image line data stream, and carrying out the image line data stream; reading the mean value result of the previous frame from the time domain compensation cache, carrying out time domain accumulation operation based on the mean value result of the previous frame, writing the result of the time domain accumulation operation into the time domain compensation cache, reading the time domain compensation information of the current frame from the time domain compensation cache, and carrying out correction compensation on the infrared image. And writing the compensated and corrected infrared image data of the upper half part and the lower half part into a cache, splicing and combining, and outputting a 2048 * 2048 infrared original image, so that the sampling stability of the 2K digital detector can be improved, the non-uniformity of a reading circuit of the 2K digital detector is weakened, and the method has a very good popularization space.

Description

Technical Field

[0001] The invention belongs to the field of infrared imaging image processing of aviation aircraft, and relates to an infrared imaging signal processing method based on a digital detector. Background Art

[0002] Infrared technology has a history of more than 200 years since its origin. In 1800, the British Herbert Hirth used a mercury thermometer to discover infrared radiation. In 1821, thermocouples and thermopiles began to be used in infrared detectors. In 1859, Kirchhoff proposed the law of the relationship between the absorption and emission of thermal radiation of objects. In 1900, Planck published the energy quantum model and the blackbody radiation law, and derived the relationship between the blackbody spectral radiation emittance and temperature and wavelength. The above work has laid a solid theoretical foundation for the development of infrared technology. In the decade from 1910 to 1920, infrared devices for detecting targets such as ships, aircraft, artillery positions and icebergs appeared, and communication, security, infrared temperature measurement and other equipment were developed. In 1952-1953, the United States developed the world's earliest thermal imager.

[0003] At present, the column-level digital readout circuit of the digital detector based on infrared technology integrates the analog-to-digital converter (ADC) into the readout circuit. The circuit is suitable for N-on-P type mercury cadmium telluride detectors. The exposure mode of the detector is snapshot mode, and it adopts the integration-while-reading working mode. It has two LVDS digital outputs and a unique SPI serial port control function. These readout circuits adopt a column-level ADC digital readout architecture. A total of 4096 ADCs are integrated on the chip, divided into two 2048×1 arrays, which are placed on the upper and lower sides of the pixel array respectively. The upper 2048 ADCs are connected to the outputs of the upper half of the column pixels in the pixel array, and the lower 2048 ADCs are connected to the outputs of the upper half of the column pixels in the pixel array. 2048 ADCs are connected to the outputs of the lower column pixels in the pixel array. The ADC outputs are cached and selected by the multiplexer and finally sent to the outside of the chip by the high-speed LVDS interface. A total of eight data output channels are configured, which are used to transmit data of the upper column pixels and the lower column pixels respectively. Therefore, the existing digital detectors can directly output digital signals and directly perform digital image processing. At the same time, it can also improve system integration, reduce system power consumption, and improve system electromagnetic compatibility. It is the most advanced new generation 2K infrared focal plane detection technology in the world. The use of digital detectors has enabled the development of infrared imaging sensors to enter the processing system of the full digital domain.

[0004] However, due to the characteristics of the 2K digital readout circuit, when the detector outputs a total of 8 channels of data in the upper and lower halves in parallel, the readout circuit has different relative output delays among different channels in the 8 channels due to process differences. Therefore, when the detector is in high frame rate working mode and uses a high-speed clock to sample the 8-channel data in parallel, it cannot guarantee that the 8 channels are stably and correctly sampled at the same clock edge for verification data, resulting in unstable and flickering image sampling. Secondly, due to the characteristics of the parallel output of the ADCs in the upper and lower parts of the detector readout circuit, after the detector is calibrated at two points, as the power-on time passes, non-uniform vertical bars gradually appear in the upper and lower halves of the 2K infrared image, and a more obvious stratification boundary appears in the middle of the 2K image, which significantly reduces the overall quality and performance of the infrared image.

[0005] Therefore, it is necessary to design an infrared imaging signal processing method based on a digital detector to solve the above technical problems. Summary of the invention

[0006] In view of this, the present invention proposes an infrared imaging signal processing method based on a digital detector, which can read out two images with a resolution of 2048×1024 in a sorted manner through multi-channel automatic sampling cache, and perform time domain non-uniformity compensation on the two images respectively to reduce the non-uniform drift of the infrared image caused by the power-on time. Finally, the two images are spliced ​​in the cache to form an infrared image with a resolution of 2048×2048, which effectively solves the existing technical problems of poor sampling stability, obvious stratification boundaries and poor infrared image quality.

[0007] In order to achieve the above technical objectives, the specific technical solutions adopted by the present invention are:

[0008] A method for processing infrared imaging signals based on a digital detector comprises the following steps:

[0009] S1, control the infrared imaging component to power on;

[0010] S2, divided into 4 channels in the upper half and 4 channels in the lower half, parallel data, each channel is sampled independently;

[0011] S3, after verification, write to the independent channel cache;

[0012] S4, the buffer reads out pixel data in sequence to form an image row data stream;

[0013] S5, find the average value of the coordinate data corresponding to the first two rows of the current frame, the formula is as follows;

[0014]

[0015] Where 0, 1, 2…2047;

[0016] Then read the average result of the previous frame from the time domain compensation buffer, the expression is

[0017] S6. Perform a time domain accumulation operation based on the average result of the previous frame to obtain a result of the time domain accumulation operation. The formula is as follows:

[0018]

[0019] Among them, j=0,1,2…2047, α+β=1;

[0020] and writing the result of the time domain accumulation operation into the time domain compensation buffer for updating the time domain compensation information;

[0021] S7, read the time domain compensation information of the current frame from the time domain compensation buffer, the expression is

[0022] The infrared image is corrected and compensated, and the formula is as follows:

[0023]

[0024] Where i = 2, 3, 4…1025; 0, 1, 2…2047, δ is the compensation parameter, bias is a constant used to offset the weakening of gray value response after compensation, f cur (i, j) is the infrared image data information when data is read out from the channel buffer to the third row.

[0025] S8, writing the compensated and corrected upper and lower parts of the infrared image data into a cache, and splicing and combining them to form a 2048×2048 infrared image;

[0026] S9, finally outputting a 2048×2048 infrared original image.

[0027] Furthermore, in step S1, when the infrared imaging component is powered on, the infrared detector movement is cooled to temperature, the global reset of the infrared detector is completed, the detector parameters and integration time registers are configured through SPI, and a periodic frame trigger signal is generated.

[0028] Furthermore, in step S2, each channel uses an independent clock, and each channel is checked using a row check word.

[0029] Furthermore, in step S9, a two-point correction is performed on the 2048×2048 infrared image formed in step S8, and a corrected 2048×2048 infrared image is output.

[0030] Furthermore, in step S7, when the data is read out from the channel buffer and the infrared image data information starts from the third row, the time domain compensation information of the current frame is read out from the time domain compensation buffer to correct and compensate the infrared image.

[0031] Furthermore, the digital detector integrates an analog-to-digital converter (ADC) into the readout circuit, which is suitable for N-on-P type mercury cadmium telluride detectors. The exposure mode of the detector is snapshot mode, and it adopts an integration-while-readout working mode. It has two LVDS digital outputs and a unique SPI serial port control function.

[0032] Furthermore, the readout circuit in the digital detector adopts a column-level ADC digital readout architecture. A total of 4096 ADCs are integrated on the chip, divided into two 2048×1 arrays, placed on the upper and lower sides of the pixel array respectively. The upper 2048 ADCs are connected to the outputs of the upper half of the column pixels in the pixel array, and the lower 2048 ADCs are connected to the outputs of the lower column pixels in the pixel array. The outputs of the ADCs in the digital detector are cached and selected by the multiplexer and finally sent to the outside of the chip by the high-speed LVDS interface.

[0033] By adopting the above technical solution, the present invention can also bring the following beneficial effects:

[0034] 1. The present invention mentions an infrared imaging signal processing method based on a digital detector. By independently sampling 8 channels, the digital signals of 8 channels are processed separately, which can improve the image sampling stability of the digital detector under high frame rate and high-speed clock conditions, and at the same time improve the compatibility of the infrared imaging circuit with devices produced by different detector process flows. It has the advantages of strong versatility, strong compatibility with clock frequency and frame rate, complete module packaging, and can be quickly transplanted.

[0035] 2. The present invention mentions an infrared imaging signal processing method based on a digital detector, which utilizes time domain compensation for non-uniformity compensation, thereby correcting the non-uniform drift of the original infrared image caused by the change in the reference voltage amplitude, and weakening the edge traces formed by the different non-uniformities when the upper and lower halves are spliced ​​together due to the characteristics of the readout circuit. The method has strong portability, stable effect, and avoids the influence of the column-level digital readout circuit on the non-uniformity of the digital detector from the source, and has a very good application space. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 The present invention discloses a flow chart of an infrared imaging signal processing method based on a digital detector. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0039] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0040] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present invention, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0041] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention. The drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0042] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0043] Example 1

[0044] In one embodiment of the present invention, see Figure 1, an infrared imaging signal processing method based on a digital detector, comprising the following steps:

[0045] S1, control the infrared imaging component to power on;

[0046] When cooled to temperature, the infrared imaging circuit controls the detector to power on, resets the whole system, configures the detector parameters and integration time registers through SPI, and generates a periodic frame trigger signal.

[0047] S2, divided into 4 channels in the upper half and 4 channels in the lower half, parallel data, each channel is sampled independently;

[0048] The parallel data is sampled through 8 channels using a high-speed clock through the infrared imaging circuit.

[0049] S3, after verification, write to the independent channel cache;

[0050] The verification is performed by judging the row verification.

[0051] S4, the buffer reads out pixel data in sequence to form an image row data stream;

[0052] When the 8 buffers have enough data for one row in each of the upper and lower halves, they can be read out in sequence from the 8 channel buffers to form an image row data stream. This operation can improve the stability of detector sampling at high frame rates and high-speed clocks.

[0053] S5, find the average value of the coordinate data corresponding to the first two rows of the current frame, the formula is as follows;

[0054]

[0055] Where 0, 1, 2…2047;

[0056] Then read the average result of the previous frame from the time domain compensation buffer, the expression is

[0057] The ADCs in the upper and lower parts of the detector output 1026 lines of data respectively, the first 2 lines are reference voltage data information, and the last 1024 lines are image data information.

[0058] S6. Perform a time domain accumulation operation based on the average result of the previous frame to obtain a result of the time domain accumulation operation. The formula is as follows:

[0059]

[0060] Among them, j=0,1,2…2047, α+β=1;

[0061] The result of the time domain accumulation operation is written into the time domain compensation cache for updating the time domain compensation information. The time domain variation introduced by the compensation effect due to the change in the amplitude difference between the current frame voltage and the previous frame voltage can be weakened through time domain iteration.

[0062] S7. When the data is read out from the channel buffer to the third line, the infrared image data information is , read the time domain compensation information of the current frame from the time domain compensation buffer, the expression is

[0063] The infrared image is corrected and compensated, and the formula is as follows:

[0064]

[0065] Where i = 2, 3, 4...1025; 0, 1, 2...2047, δ is the compensation parameter, bias is a constant, which is used to offset the weakening of the gray value response after compensation. Through time domain compensation, the non-uniform drift of the infrared image caused by the time domain and spatial domain changes of the reference voltage can be corrected in real time, thereby improving the quality and performance of the original infrared image.

[0066] S8, writing the compensated and corrected upper and lower parts of the infrared image data into a cache, and splicing and combining them to form a 2048×2048 infrared image;

[0067] S9. Perform two-point correction on the compensated 2K original infrared image, and finally output the corrected 2048×2048 original infrared image, so that the effect of the optimization method can be observed.

[0068] The digital detector integrates the analog-to-digital converter (ADC) into the readout circuit. The circuit is suitable for N-on-P type HgCdTe detectors. The exposure mode of the detector is snapshot mode. It adopts the integration-while-readout working mode, has two LVDS digital outputs, and a unique SPI serial port control function.

[0069] The readout circuit in the digital detector adopts a column-level ADC digital readout architecture. A total of 4096 ADCs are integrated on the chip, divided into two 2048×1 arrays, placed on the upper and lower sides of the pixel array respectively. The upper 2048 ADCs are connected to the outputs of the upper half of the pixel array, and the lower 2048 ADCs are connected to the outputs of the lower column of pixels in the pixel array. The outputs of the ADCs in the digital detector are cached, selected by the multiplexer, and finally sent to the outside of the chip by the high-speed LVDS interface.

[0070] In summary, the present invention can improve the sampling stability of the 2K digital detector and reduce the different non-uniformities of the upper and lower parts caused by the output characteristics of the 2K digital detector readout circuit, thereby avoiding the influence of the column-level digital readout circuit on the non-uniformity of the digital detector from the source, and has very good promotion space.

[0071] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for processing infrared imaging signals based on a digital detector, characterized in that: The following steps are involved: S1, control the infrared imaging component to power on; S2, divided into 4 channels in the upper half and 4 channels in the lower half, parallel data, each channel is sampled independently; S3, after verification, write to the independent channel cache; S4, the buffer reads out pixel data in sequence to form an image row data stream; S5, find the average value of the coordinate data corresponding to the first two rows of the current frame, the formula is as follows; Where 0, 1, 2…2047; Then read the average result of the previous frame from the time domain compensation buffer, the expression is S6. Perform a time domain accumulation operation based on the average result of the previous frame to obtain a result of the time domain accumulation operation. The formula is as follows: Among them, j=0,1,2…2047, α+β=1; and writing the result of the time domain accumulation operation into the time domain compensation buffer for updating the time domain compensation information; S7, read the time domain compensation information of the current frame from the time domain compensation buffer, the expression is The infrared image is corrected and compensated, and the formula is as follows: Where i = 2, 3, 4…1025; 0, 1, 2…2047, δ is the compensation parameter, bias is a constant used to offset the weakening of gray value response after compensation, f cur (i, j) is the infrared image data information when data is read out from the channel buffer to the third row. S8, writing the compensated and corrected upper and lower parts of the infrared image data into a cache, and splicing and combining them to form a 2048×2048 infrared image; S9, finally outputting a 2048×2048 infrared original image.

2. The infrared imaging signal processing method based on a digital detector according to claim 1, characterized in that: In step S1, when the infrared imaging component is powered on, the infrared detector movement is cooled to temperature, the global reset of the infrared detector is completed, the detector parameters and integration time register are configured through SPI, and a periodic frame trigger signal is generated.

3. The infrared imaging signal processing method based on a digital detector according to claim 2, characterized in that: In step S2, each channel uses an independent clock, and each channel is checked using a row check word.

4. The infrared imaging signal processing method based on a digital detector as claimed in claim 3, characterized in that: In step S9, a two-point correction is performed on the 2048×2048 infrared image formed in step S8, and a corrected 2048×2048 infrared image is output.

5. The infrared imaging signal processing method based on a digital detector according to claim 4, characterized in that: In step S7, when the data is read out from the channel buffer and the third row is infrared image data information, the time domain compensation information of the current frame is read out from the time domain compensation buffer to correct and compensate the infrared image.

6. The infrared imaging signal processing method based on a digital detector according to claim 5, characterized in that: The digital detector integrates an analog-to-digital converter (ADC) into a readout circuit. The circuit is suitable for an N-on-P type mercury cadmium telluride detector. The exposure mode of the detector is a snapshot mode. It adopts an integration-while-readout working mode, has two LVDS digital outputs, and a unique SPI serial port control function.

7. The infrared imaging signal processing method based on a digital detector according to claim 6, characterized in that: The readout circuit in the digital detector adopts a column-level ADC digital readout architecture, with a total of 4096 ADCs integrated on the chip, divided into two 2048×1 arrays, placed on the upper and lower sides of the pixel array respectively, the upper 2048 ADCs are connected to the outputs of the upper half of the column pixels in the pixel array, and the lower 2048 ADCs are connected to the outputs of the lower column pixels in the pixel array. The outputs of the ADCs in the digital detector are cached and selected by a multiplexer and finally sent to the outside of the chip by a high-speed LVDS interface.

Images