An Infrared Imaging Signal Processing Method Based on a Digital Detector

Abstract

The present invention relates to an infrared imaging signal processing method based on a digital detector, comprising the following steps: dividing parallel data into an upper half of 4 channels and a lower half of 4 channels, performing independent sampling on each channel, writing the data into an independent channel cache after verification, sequentially reading pixel data from the cache to form an image row data stream, reading an average result of a previous frame from the time domain compensation cache, performing a time domain accumulation operation based on the average result of the previous frame, writing the result of the time domain accumulation operation into the time domain compensation cache, reading time domain compensation information of the current frame from the time domain compensation cache, correcting and compensating the infrared image, writing the compensated and corrected infrared image data of the upper and lower halves into the cache, performing splicing and combination, and outputting a 2048×2048 infrared original image. In short, the present invention can improve the sampling stability of a 2K digital detector and reduce the non-uniformity of a readout circuit of the 2K digital detector, and has very good promotion potential.

Description

Technical Field

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

[0002] Infrared technology has a history of over 200 years. In 1800, the Englishman Herschel discovered infrared radiation using a mercury thermometer. In 1821, thermocouples and thermopile devices began to be used in infrared detectors. In 1859, Kirchhoff proposed the law relating the absorption and emission of thermal radiation by objects. In 1900, Planck published the quantum model of energy and the law of blackbody radiation, deriving the relationship between the blackbody spectral radiant exitance and temperature and wavelength. These works 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, and infrared thermometry equipment were developed. In 1952-1953, the United States developed the world's first thermal imager.

[0003] Currently, the column-level digital readout circuits of infrared-based digital detectors integrate analog-to-digital converters (ADCs) into the readout circuit. This circuit is suitable for N-on-P type mercury cadmium telluride detectors, which operate in snapshot mode and use an integration-while-readout mode. It features two LVDS digital outputs and a unique SPI serial port control function. These readout circuits employ a column-level ADC digital readout architecture, integrating a total of 4096 ADCs on-chip, divided into two 2048×1 arrays, placed on the upper and lower sides of the pixel array respectively. The upper 2048 ADCs connect to the outputs of the upper half of the pixel array, while the lower... The 2048 ADCs connect to the outputs of the lower column pixels in the pixel array. After the ADC outputs are buffered, they are selected by a multiplexer and finally sent to the external device via a high-speed LVDS interface. A total of eight data output channels are configured to transmit data from the upper and lower column pixels respectively. Therefore, the existing digital detector can not only output digital signals, but also directly perform digital image processing. At the same time, it can improve system integration, reduce system power consumption, and improve system electromagnetic compatibility. It is currently 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 entire digital domain.

[0004] However, the characteristics of the 2K digital readout circuit cause the relative output delay between different channels to vary due to process differences when the detector outputs a total of 8 channels of data in parallel from the upper and lower halves. Therefore, when the detector operates in high frame rate mode and uses a high-speed clock to sample the parallel 8 channels of data, it cannot guarantee that the 8 channels will be sampled stably and correctly on the same clock edge for verification data, resulting in unstable image sampling and flickering. Secondly, due to the parallel output of the upper and lower ADCs of the detector's readout circuit, after two-point calibration, non-uniform vertical bars gradually appear in the upper and lower halves of the 2K infrared image as the power-on time progresses, and a more obvious layering 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-mentioned 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. It can read out two images with a resolution of 2048×1024 by sorting through multi-channel automatic sampling buffer, and perform temporal non-uniformity compensation on the two images to reduce the non-uniform drift of the infrared image caused by power-on time. Finally, the two images are stitched together in the buffer to form an infrared image with a resolution of 2048×2048. This effectively solves the technical problems of poor sampling stability, obvious layer boundaries and poor infrared image quality in existing methods.

[0007] To achieve the above-mentioned technical objectives, the specific technical solution adopted by the present invention is as follows:

[0008] An infrared imaging signal processing method based on a digital detector includes the following steps:

[0009] S1. Power on the infrared imaging component;

[0010] S2, is divided into an upper half of 4 channels and a lower half of 4 channels of parallel data, with each channel being sampled independently;

[0011] S3. After verification, write to an independent channel cache;

[0012] S4. The buffer reads pixel data sequentially to form an image row data stream;

[0013] S5. Calculate the average coordinate data of the first two rows of the current frame, as shown in the formula below;

[0014]

[0015] Where j = 0, 1, 2…2047;

[0016] Then, the mean value of the previous frame is read from the temporal compensation buffer, expressed as follows:

[0017] S6. Perform a time-domain summation operation based on the mean result of the previous frame to obtain the result of the time-domain summation operation, as shown in the following formula:

[0018]

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

[0020] The result of the time-domain accumulation operation is written to the time-domain compensation cache for updating the time-domain compensation information;

[0021] S7. Read the temporal compensation information of the current frame from the temporal compensation buffer, the expression is:

[0022] The formula for correcting and compensating for infrared images is as follows:

[0023]

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

[0025] S8. Write the compensated and corrected upper and lower halves of the infrared image data into the cache, and then stitch them together to form a 2048×2048 infrared image.

[0026] S9. The final output is a 2048×2048 infrared image.

[0027] Furthermore, in step S1, during the power-on process of the infrared imaging component, the infrared detector core is cooled to a certain temperature, completing the global reset of the infrared detector, configuring the detector parameters and integration time register via SPI, and generating periodic frame trigger signals.

[0028] Furthermore, in step S2, each channel uses an independent clock, and each channel's verification uses a row check word.

[0029] Furthermore, in step S9, the infrared image that makes up the 2048×2048 in step S8 is corrected at two points, and the corrected infrared image is output.

[0030] Furthermore, in step S7, when data is read from the channel buffer to the third line, the infrared image data information is f. cur(i, j), read the temporal compensation information of the current frame from the temporal compensation buffer, the expression is: Correct and compensate for infrared images.

[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 detector operates in snapshot mode, uses an integration-while-readout mode, has two LVDS digital outputs, and features a unique SPI serial port control function.

[0032] Furthermore, the readout circuit in the digital detector adopts a column-level ADC digital readout architecture, integrating a total of 4096 ADCs 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 output of the upper half of the pixel array, and the lower 2048 ADCs are connected to the output of the lower side of the pixel array. The output of the ADCs in the digital detector is buffered, selected by a multiplexer, and finally sent to the external device via a high-speed LVDS interface.

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

[0034] 1. This invention discloses an infrared imaging signal processing method based on a digital detector. By using an 8-channel independent sampling method, the digital signals of the 8 channels are processed separately. This can improve the image sampling stability of the digital detector under high frame rate and high clock conditions. At the same time, it improves the compatibility of the infrared imaging circuit with devices produced by different detector processes. It has the advantages of strong versatility, strong clock frequency and frame rate compatibility, complete module packaging, and rapid portability.

[0035] 2. This invention proposes an infrared imaging signal processing method based on a digital detector. It utilizes time-domain compensation for non-uniformity to correct the non-uniform drift of the original infrared image caused by changes in the reference voltage amplitude. It also weakens the edge traces caused by the different non-uniformities when splicing the upper and lower halves due to the characteristics of the readout circuit. It 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. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1This is a flowchart illustrating an infrared imaging signal processing method based on a digital detector, as described in this invention. Detailed Implementation

[0038] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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 based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this invention, those skilled in the art will understand that one 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 set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0041] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0042] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can 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 includes the following steps:

[0045] S1. Power on the infrared imaging component;

[0046] The process involves cooling to a warm temperature, the infrared imaging circuit controlling the detector to power on, a global reset, configuring detector parameters and the integration time register via SPI, and generating periodic frame trigger signals.

[0047] S2, is divided into an upper half of 4 channels and a lower half of 4 channels of parallel data, with each channel being sampled independently;

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

[0049] S3. After verification, write to an independent channel cache;

[0050] The verification passes the row check.

[0051] S4. The buffer reads pixel data sequentially to form an image row data stream;

[0052] Once the eight buffers have stored enough data for each of the upper and lower halves, they can be read sequentially from the eight channel buffers to form an image row data stream. This operation can improve the stability of detector sampling under high frame rate and high speed clock conditions.

[0053] S5. Calculate the average coordinate data of the first two rows of the current frame, as shown in the formula below;

[0054]

[0055] Where j = 0, 1, 2…2047;

[0056] Then, the mean value of the previous frame is read from the temporal compensation buffer, expressed as follows:

[0057] The detector's upper and lower ADCs each output 1026 lines of data: the first two lines are reference voltage data, and the last 1024 lines are image data.

[0058] S6. Perform a time-domain summation operation based on the mean result of the previous frame to obtain the result of the time-domain summation operation, as shown in the following formula:

[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 to update the time-domain compensation information. Time-domain iteration can reduce the time-domain changes introduced into the compensation effect by the change in the voltage amplitude difference between the current frame and the previous frame.

[0062] S7. When reading data from the channel buffer to the 3rd line, the infrared image data information is f. cur (i, j), read the temporal compensation information of the current frame from the temporal compensation buffer, the expression is:

[0063] The formula for correcting and compensating for infrared images is as follows:

[0064]

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

[0066] S8. Write the compensated and corrected upper and lower halves of the infrared image data into the cache, and then stitch them together 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 infrared image to observe the effect of the method after optimization.

[0068] 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 detector uses a snapshot exposure mode, an integration-while-readout working mode, 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, 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 output of the upper half of the pixel array, and the lower 2048 ADCs are connected to the output of the lower half of the pixel array. The output of the ADCs in the digital detector is buffered, selected by a multiplexer, and finally sent to the off-chip via a high-speed LVDS interface.

[0070] In summary, this invention can improve the sampling stability of a 2K digital detector and reduce the different non-uniformity between the upper and lower parts caused by the output characteristics of the 2K digital detector's readout circuit. It avoids the influence of the column-level digital readout circuit on the non-uniformity of the digital detector from the source and has great potential for promotion.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for processing infrared imaging signals based on a digital detector, characterized in that, Includes the following steps: S1. Power on the infrared imaging component; S2, is divided into an upper half of 4 channels and a lower half of 4 channels of parallel data, with each channel being sampled independently; S3. After verification, write to an independent channel cache; S4. The buffer reads pixel data sequentially to form an image row data stream; S5. Calculate the average coordinate data of the first two rows of the current frame, as shown in the formula below; Where j = 0, 1, 2…2047; Then, the mean value of the previous frame is read from the temporal compensation buffer, expressed as follows: S6. Perform a time-domain summation operation based on the mean result of the previous frame to obtain the result of the time-domain summation operation, as shown in the following formula: Among them, j=0,1,2…2047, α+β=1; The result of the time-domain accumulation operation is written to the time-domain compensation cache for updating the time-domain compensation information; S7. Read the temporal compensation information of the current frame from the temporal compensation buffer, the expression is: The formula for correcting and compensating for infrared images is as follows: Where i = 2, 3, 4…1025; j = 0, 1, 2…2047, δ is the compensation parameter, bias is a constant used to counteract the weakening of the grayscale response after compensation, and f cur (i, j) represents the infrared image data information when data is read from the channel buffer to the 3rd row; S8. Write the compensated and corrected upper and lower halves of the infrared image data into the cache, and then stitch them together to form a 2048×2048 infrared image. S9. The final output is a 2048×2048 infrared image.

2. The infrared imaging signal processing method based on a digital detector as described in claim 1, characterized in that: In step S1, during the power-on process of the infrared imaging component, the infrared detector core is cooled to a certain temperature, completing the global reset of the infrared detector. The detector parameters and integration time register are configured via SPI, and a periodic frame trigger signal is generated.

3. The infrared imaging signal processing method based on a digital detector as described in claim 2, characterized in that: In step S2, each channel uses an independent clock, and each channel's verification uses a row check word.

4. The infrared imaging signal processing method based on a digital detector as described in claim 3, characterized in that: In step S9, the infrared image that makes up the 2048×2048 in step S8 is corrected at two points, and the corrected infrared image is output.

5. The infrared imaging signal processing method based on a digital detector as described in claim 4, characterized in that: In step S7, when data is read from the channel buffer to the third line, the infrared image data information is f. cur (i, j), read the temporal compensation information of the current frame from the temporal compensation buffer, the expression is: Correct and compensate for infrared images.

6. The infrared imaging signal processing method based on a digital detector as described in claim 5, characterized in that: The digital detector integrates an analog-to-digital converter into the readout circuit, which is suitable for N-on-P type mercury cadmium telluride detectors. The detector's exposure mode 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.

7. The infrared imaging signal processing method based on a digital detector as described in 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 output of the upper half of the pixel array, and the lower 2048 ADCs are connected to the output of the lower side of the pixel array. The output of the ADCs in the digital detector is buffered, selected by a multiplexer, and finally sent to the off-chip via a high-speed LVDS interface.

Images