JT refrigeration infrared focal plane detector newly-added blind pixel detection method considering air source quality fluctuation

Abstract

The invention provides a JT refrigeration infrared focal plane detector newly-added blind pixel detection method considering air source quality fluctuation, and belongs to the field of blind pixel detection. The problem that the imaging quality of an infrared imaging system is damaged due to blind pixels of an infrared detector caused by air source quality fluctuation is solved; comprising the following steps: aligning a JT refrigeration infrared focal plane detector in a normal working state to a surface source black body, and enabling a JT refrigerator to be in a stable operation state; turning off a gas source switch, starting to store output image data of the detector, and monitoring an output voltage signal of a temperature measuring diode of the detector; when the output voltage signal of the detector temperature measuring diode is reduced to a set threshold value, data storage is automatically stopped; reading back the existing blind pixel coordinate data of the detector stored in the infrared imaging system; calculating a newly added blind pixel in the stored image data; sequencing the existing blind pixels and the newly added blind pixels to generate a new blind pixel coordinate file; the method is applied to the blind pixel detection of the JT refrigeration infrared focal plane detector.

Description

Technical Field

[0001] The invention provides a newly added blind pixel detection method for a JT refrigeration infrared focal plane detector taking into account fluctuations in gas source quality, belonging to the technical field of blind pixel detection. Background Art

[0002] JT cooled infrared focal plane detectors are widely used in various types of precision-guided weapons and equipment due to their small size, light weight, fast startup and high sensitivity. However, such equipment requires high-quality high-pressure gas when working. Once the quality of the gas source fluctuates, blind pixels will appear in the imaging system, damaging the image output quality of the infrared imaging system and affecting the detection and tracking of targets by precision-guided weapons.

[0003] High-sensitivity infrared focal plane detectors usually work in ultra-low temperature environments (generally 80-90K (-183℃~-193℃) and below), and a refrigerator is needed to create a low-temperature environment for it. At the same time, the system will monitor the output voltage of the temperature measuring diode inside the detector to determine the temperature inside the detector dewar, that is, the working state. Among them, the JT refrigerator is widely used due to its small size, light weight, and fast start-up. The JT refrigerator uses the cooling effect of high-pressure gas expansion to create a low-temperature environment. During use, high-quality high-pressure nitrogen is generally used.

[0004] When the gas source quality fluctuates, it will have a greater impact on the JT cooler, causing the internal temperature of the detector to rise. By studying the IV characteristics of infrared focal plane pixels (essentially photodiodes), such as Figure 1 As shown in the figure, for an infrared focal plane detector in a reverse biased working state, the diode leakage current of some pixels will be larger as the ambient temperature rises (as shown by the red curve). The diode leakage current is superimposed on the photocurrent and converted into voltage by the readout circuit and A / D sampling. It will appear as a bright blind pixel with a higher grayscale value in the image. Summary of the invention

[0005] In order to solve the problem that blind pixels appear in infrared detectors due to fluctuations in gas source quality, thereby damaging the imaging quality of infrared imaging systems, the present invention proposes a new blind pixel detection method for a JT cooled infrared focal plane detector taking into account fluctuations in gas source quality.

[0006] The technical solution adopted by the present invention is: a method for detecting blind pixels added to a JT-cooled infrared focal plane detector taking into account fluctuations in gas source quality, comprising the following steps: S1: Aim the JT-cooled infrared focal plane detector in normal working state at the surface source black body, and keep the JT cooler in stable operation state; S2: Turn off the gas source switch and start saving the output image data of the detector, while monitoring the output voltage signal of the temperature measuring diode of the detector; S3: When the output voltage signal of the temperature measuring diode of the detector drops to the set threshold, data saving will be automatically stopped; S4: Read back the existing blind element coordinate data of the detector stored in the infrared imaging system; S5: Calculate the newly added blind pixels in the image data stored in step S2; S6: Sort the blind pixels in steps S4 and S5 to generate a new blind pixel coordinate file.

[0007] Furthermore, in step S3, the threshold range of the output voltage signal of the temperature measuring diode of the detector is set according to the range of the temperature rise in the detector dewar.

[0008] Furthermore, the temperature rise inside the detector dewar is controlled at 4°C~5°C.

[0009] Furthermore, the threshold value of the output voltage signal of the temperature measuring diode of the detector is set in the range of 8mV-12.5mV.

[0010] Furthermore, in step S5, the position and number of the newly added blind pixels are calculated by sliding window mean square error.

[0011] Furthermore, the existing blind pixel coordinate data in step S4 is the original blind pixel coordinates after the detector is calibrated before leaving the factory or the last calibration data after the detector has been used before leaving the factory.

[0012] Furthermore, the new blind element coordinate file is burned into the product using the JT cooled infrared focal plane detector and read back for verification.

[0013] The beneficial effects of the present invention compared with the prior art are as follows: the present invention utilizes the process of shutting off the gas source to simulate the gas source quality fluctuation, determines the temperature rise inside the dewar by monitoring the output voltage of the detector temperature measuring diode, detects and eliminates the blind pixels generated when the temperature rises inside the dewar in advance, reduces the probability of new blind pixels caused by gas source quality fluctuation during the use of the infrared imaging system, and improves the reliability and stability of the infrared imaging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 It is the IV characteristic diagram of the focal plane detector pixel changing with temperature; Figure 2 The monitoring flow chart of the method of the present invention is shown in FIG. DETAILED DESCRIPTION

[0015] like Figure 2As shown, the present invention provides a method for detecting newly added blind pixels of a JT refrigerated infrared focal plane detector taking into account fluctuations in gas source quality. The process of shutting off the external gas source of the JT refrigerated infrared focal plane detector is cleverly used to simulate fluctuations in gas source quality. By collecting the image data of the JT refrigerated infrared focal plane detector in this process, pixels that are not robust and have hidden dangers in the detector can be detected in advance, and these pixels can be eliminated, thereby ensuring the performance of weapons and equipment during use and reducing the probability of device maintenance. The method of the present invention can be used for secondary calibration of the detector after factory calibration, and can also be used for recalibration of the detector installed on the weapon equipment after a period of use (or regular calibration at regular intervals), and there is no need to remove the detector separately for detection, thereby improving detection efficiency.

[0016] The method of the present invention includes the steps of image acquisition, detector temperature measurement diode output voltage monitoring, diode voltage value automatic control image storage, blind pixel judgment, blind pixel coordinate reading back, merging and burning. The specific implementation process is as follows: 1) Aim the JT cooled infrared focal plane detector at the surface source black body, which is in normal working state, and make the JT cooler in stable operation state, that is, the internal regulator is in the self-adjusting state with a small opening.

[0017] 2) Turn off the gas source switch and start saving the output image data of the detector, while monitoring the output voltage signal of the temperature measuring diode of the detector.

[0018] 3) When the output voltage signal of the temperature measuring diode drops to 10mV, data saving will stop automatically.

[0019] 4) Read back the original or existing blind pixel coordinates of the detector in the infrared imaging system.

[0020] 5) Calculate the newly added blind pixels in the image data stored this time.

[0021] 6) Blind cell burning after merging: Sort the blind cells in steps 4) and 5) in ascending order, generate a new blind cell coordinate file, burn it into the product, and perform a read-back verification.

[0022] In the present invention, the control threshold of the change value of the output voltage of the temperature measuring diode is particularly critical. When the threshold is small, the temperature change in the detector dewar is not large, and the weak pixels have not yet shown the blind pixel state; when the threshold is large, the change in the detector dewar is too large, and many pixels will be misjudged as blind pixels, affecting the use of the infrared imaging system. In general, it is believed that for every 1°C increase in the temperature in the detector dewar, the output voltage of the temperature measuring diode increases by about 2mV~2.5mV. Through a large number of tests and tracking the increase of blind pixels in the subsequent use of the product, this embodiment sets the upper limit of the threshold to 10mV, that is, when the output voltage reduction value of the temperature measuring diode is controlled at 10mV, when the temperature rise in the detector dewar is controlled at 4°C~5°C, the position and number of blind pixels determined by a certain sliding window mean square error detection standard best meet the use requirements of the infrared imaging system.

[0023] The method of the present invention has been used and verified on an infrared imaging system using a JT-cooled infrared focal plane detector. The invention has an ingenious idea and a simple and practical implementation method, which greatly reduces the probability of new blind pixels appearing in the detector during subsequent use and reduces the maintenance frequency of the system. The technology used in the present invention is highly mature and practical, filling the gap of how to deal with new blind pixels generated by fluctuations in gas source quality in an infrared imaging system using an infrared focal plane detector based on JT cooling, and is easy to implement in engineering. The method of the present invention can greatly improve the reliability and stability of the infrared imaging system and reduce the maintenance frequency and cost. It has versatility and has broad application and promotion prospects for infrared imaging systems using JT-cooled infrared focal plane detectors.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A new blind pixel detection method for a JT-cooled infrared focal plane detector considering fluctuations in gas source quality, characterized in that: The following steps are involved: S1: Aim the JT-cooled infrared focal plane detector in normal working state at the surface source black body, and keep the JT cooler in stable operation state; S2: Turn off the gas source switch and start saving the output image data of the detector, while monitoring the output voltage signal of the temperature measuring diode of the detector; S3: When the output voltage signal of the temperature measuring diode of the detector drops to the set threshold, data saving will be automatically stopped; S4: Read back the existing blind element coordinate data of the detector stored in the infrared imaging system; S5: Calculate the newly added blind pixels in the image data stored in step S2; S6: Sort the blind pixels in steps S4 and S5 to generate a new blind pixel coordinate file.

2. According to claim 1, a method for detecting newly added blind pixels of a JT-cooled infrared focal plane detector taking into account fluctuations in gas source quality, characterized in that: In step S3, the threshold range of the output voltage signal of the temperature measuring diode of the detector is set according to the range of the temperature rise in the detector dewar.

3. The method for detecting newly added blind pixels of a JT-cooled infrared focal plane detector taking into account fluctuations in gas source quality according to claim 2, characterized in that: The temperature rise in the detector Dewar is controlled at 4℃~5℃.

4. The method for detecting newly added blind pixels of a JT-cooled infrared focal plane detector taking into account fluctuations in gas source quality according to claim 3, characterized in that: The set threshold of the output voltage signal of the detector temperature measuring diode is 8mV-12.5mV.

5. The method for detecting newly added blind pixels of a JT-cooled infrared focal plane detector taking into account fluctuations in gas source quality according to claim 1, characterized in that: In step S5, the position and number of the newly added blind pixels are calculated by the sliding window mean square error.

6. The method for detecting newly added blind pixels of a JT-cooled infrared focal plane detector taking into account fluctuations in gas source quality according to claim 1, characterized in that: The existing blind pixel coordinate data in step S4 is the original blind pixel coordinates after the detector is calibrated before leaving the factory or the last calibration data after the detector has been used before leaving the factory.

7. A method for detecting newly added blind pixels in a JT-cooled infrared focal plane detector taking into account fluctuations in gas source quality according to any one of claims 1 to 6, characterized in that: Burn the new blind pixel coordinate file into the product using JT cooled infrared focal plane detector and perform a read-back verification.

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