Optoelectronic centering method and assembly method for complex infrared detection imaging system

Abstract

The present invention relates to the field of optoelectronic detection technology, and particularly to an optoelectronic centering method and an assembly method for a complex infrared detection imaging system. The optoelectronic centering method includes: performing non-uniform correction on the infrared detector in a case of being separated from the optical system; obtaining the transfer function corresponding to the optical system; obtaining an image to be processed after assembling the optical system and the infrared detector; performing frame superposition processing on multiple frames of the image to be processed to obtain a gray distribution map with noise suppression; determining information of N feature points based on the gray distribution map; establishing a mapping relationship between the gray distribution map and the transfer function based on the information of multiple feature points; determining the coordinates of the gray distribution maximum value point based on the maximum and minimum values of the transfer function and the mapping relationship between the gray distribution map and the transfer function; and performing optoelectronic centering according to the coordinates of the gray distribution maximum value point and the electronic center position. The present invention can achieve high-precision optoelectronic centering of a complex infrared detection imaging system, thereby improving the system performance.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic detection, and particularly to an optoelectronic centering method for a complex infrared detection imaging system. Background Art

[0002] Different from traditional optoelectronic detection devices, parameters such as NETD, detection distance, and detection sensitivity of an infrared detection imaging system have relatively high requirements for the MTF, transmittance, and optoelectronic center consistency of its internal optical system. Especially for a complex folded optical system, which is mostly used in high-integration and small-size infrared detection imaging devices, the redundancy between the optical field of view and the detection target surface is very limited. Therefore, it is particularly dependent on optoelectronic centering debugging, otherwise it will directly affect the detection performance of the infrared detection imaging system. At present, high-precision optoelectronic centering debugging of complex infrared detection imaging systems is still one of the technical problems in the industry. Summary of the Invention

[0003] (1) Technical Problems to be Solved

[0004] The technical problem to be solved by the present invention is to solve the problem that it is difficult to achieve high-precision optoelectronic centering for a complex infrared detection imaging system, so as to improve the detection performance of the infrared detection imaging system.

[0005] (2) Technical Solutions

[0006] To solve the above technical problems, the present invention provides an optoelectronic centering method for a complex infrared detection imaging system, which includes:

[0007] When the optical system of the infrared detection imaging system is separated from the infrared detector, perform non-uniform correction on the infrared detector;

[0008] Obtain the transfer function corresponding to the optical system;

[0009] After assembling the optical system and the infrared detector, obtain multiple frames of images to be processed;

[0010] Based on multiple frames of the images to be processed, perform frame superposition processing to obtain a gray-scale distribution map with noise suppression;

[0011] Based on the gray-scale distribution map, determine the information of N feature points; the information of the feature points includes the eigenvalue of the feature points and the coordinates in the gray-scale distribution map; N is a positive integer not less than 20;

[0012] Based on the information of the determined multiple feature points, establish a mapping relationship between the gray-scale distribution map and the transfer function;

[0013] Based on the maximum and minimum values of the transfer function and the mapping relationship between the gray-scale distribution map and the transfer function, determine the coordinates of the maximum and minimum points of the gray-scale distribution;

[0014] Based on the coordinates of the maximum and minimum points of the gray-scale distribution and the electronic center position of the infrared detector, perform optoelectronic centering of the infrared detection imaging system.

[0015] Optionally, the non-uniform correction of the infrared detector includes:

[0016] In the absence of the optical system, use only the infrared detector to image a uniform blackbody to obtain a background image;

[0017] Based on the uniformity of the background image, correct the infrared detector until the uniformity of the background image meets the preset index.

[0018] Optionally, the obtaining of the transfer function corresponding to the optical system includes:

[0019] In the absence of the infrared detector, use a transfer function meter to measure the transfer function of the optical system.

[0020] Optionally, the frame superposition processing based on multiple frames of the to-be-processed images includes:

[0021] After superimposing the gray-scale values of n frames of the to-be-processed images according to the coordinates and taking the average value, use it as the gray-scale value of the gray-scale distribution map; where n≥100.

[0022] Optionally, the determination of the information of N feature points based on the gray-scale distribution map includes:

[0023] Based on the gray-scale distribution map, calculate the gradient data in the row direction and the column direction respectively;

[0024] For the row direction and the column direction, respectively, sort the corresponding gradient data from large to small and select the top M gradient values; M≥10;

[0025] Take the points where the selected 2M gradient values are located as feature points, and the gradient values are the corresponding feature values.

[0026] Optionally, the determination of the coordinates of the maximum and minimum points of the gray-scale distribution includes:

[0027] If the optical system is a fully transmissive optical system, determine the coordinates of the maximum value in the gray-scale distribution in the gray-scale distribution map;

[0028] If the optical system is a catadioptric optical system, determine the coordinates of the minimum value in the gray-scale distribution in the gray-scale distribution map.

[0029] Optionally, the optoelectronic centering of the infrared detection imaging system includes:

[0030] Compare the size of the electronic target surface of the infrared detector and the size of the optical field of view of the optical system;

[0031] If the electronic alignment results in the loss of the optical field of view, adjust the relative position of the optical system and the infrared detector; otherwise, use electronic alignment to make the coordinates of the maximum and minimum points of the gray level distribution coincide with the electronic center position of the infrared detector.

[0032] Optionally, the determining the information of N feature points based on the gray level distribution map further includes:

[0033] Based on the gray level distribution map, sort the gray level values in the row direction and the column direction from large to small, and select the first L gray level values; L≥5;

[0034] Also use the points where the selected 2L gray level values are located as feature points, and the gray level values are the corresponding feature values.

[0035] Optionally, after obtaining multiple frames of images to be processed and before performing frame stacking based on the multiple frames of images to be processed, it further includes:

[0036] Perform filtering processing on each frame of the image to be processed.

[0037] The present invention also provides a method for assembling a complex infrared detection imaging system. During the stage of assembling the optical system and the infrared detector, the method for aligning the optical axis and the electronic center position of the complex infrared detection imaging system as described in any one of the above is used for calibration.

[0038] (III) Advantageous Effects

[0039] The above technical solution of the present invention has the following advantages: The present invention provides a method for aligning the optical and electronic centers of a complex infrared detection imaging system and an assembly method; the present invention performs non-uniform correction on the infrared detector when the optical system and the infrared detector are separated, and then assembles the optical system. At this time, when imaging again, the non-uniformity is completely introduced by the optical system. By combining the actually obtained gray level distribution with the transfer function corresponding to the optical system, the accurate position of the optical axis of the optical system in the image is determined, and finally the optical and electronic alignment of the infrared detection imaging system is achieved. The present invention can complete high-precision calibration and debugging of the optical axis of the optical system and the electronic imaging center of the infrared detector during the optoelectronic integration stage, thereby improving the detection performance of the infrared detection imaging system, and is particularly suitable for infrared detection imaging systems using complex folded optical systems. Description of the Drawings

[0040] Figure 1 It is a schematic diagram of the steps of a method for aligning the optical and electronic centers of a complex infrared detection imaging system in an embodiment of the present invention;

[0041] Figure 2It is the image to be processed obtained by an infrared detection imaging system in an embodiment of the present invention after assembling the optical system;

[0042] Figure 3 It is the three-dimensional distribution grayscale image corresponding to the image obtained by an infrared detection imaging system in an embodiment of the present invention. Detailed implementation manners

[0043] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] As described above, the infrared detection imaging system has relatively high requirements for the consistency of the optoelectronic center. Especially for the infrared detection imaging system adopting a complex folded optical system, it has high integration, small volume, and very limited redundancy between the optical field of view and the detection target surface. Therefore, high-precision optoelectronic centering debugging is particularly required. Otherwise, it will directly affect the detection performance of the infrared detection imaging system. The existing technology has a low accuracy in the optoelectronic centering debugging of complex infrared detection imaging systems. That is to say, the optical axis of the optical system cannot be strictly aligned with the electronic imaging center (also called the electronic center position) of the infrared detector, and the deviation often has dozens or even hundreds of pixels. In view of this, the present invention provides an optoelectronic centering method applicable to complex infrared detection imaging systems. This method uses the grayscale distribution of the actual image and the transfer function of the optical system to locate the optical axis, which can effectively improve the accuracy of the calibration debugging of the optical axis and the electronic imaging center.

[0045] As Figure 1 shown, an optoelectronic centering method for a complex infrared detection imaging system provided by an embodiment of the present invention includes:

[0046] Step 100, perform non-uniform correction on the infrared detector when the optical system of the infrared detection imaging system is separated from the infrared detector;

[0047] Step 102, obtain the transfer function corresponding to the optical system;

[0048] Step 104, after assembling the optical system and the infrared detector, obtain multiple frames of images to be processed;

[0049] Step 106, perform frame stacking processing on multiple frames of the images to be processed to obtain a grayscale distribution map with noise suppression;

[0050] Step 108: Determine the information of N feature points based on the grayscale distribution map; wherein, the information of the feature points includes the feature values of the feature points and the coordinates of the feature points in the grayscale distribution map (also known as pixel coordinates); N is a positive integer not less than 20.

[0051] Step 110: Establish a mapping relationship between the grayscale distribution map and the transfer function based on the information of the determined multiple feature points.

[0052] In this step, when establishing the mapping relationship based on the information of multiple feature points, all N feature points can be used, or some of the feature points can be discarded to avoid introducing incorrect feature point information caused by factors such as noise. However, the number of feature points used should not be too small, otherwise the mapping relationship may be inaccurate; it is preferably to establish the mapping relationship using the features of more than 10 feature points.

[0053] Step 112: Determine the coordinates of the grayscale distribution maximum and minimum points based on the maximum and minimum values of the transfer function and the mapping relationship between the grayscale distribution map and the transfer function.

[0054] Step 114: Perform optoelectronic centering of the infrared detection imaging system according to the coordinates of the grayscale distribution maximum and minimum points and the electronic center position of the infrared detector.

[0055] The optoelectronic centering method for the complex infrared detection imaging system provided by the present invention first performs non-uniform correction on the infrared detector in the infrared detection imaging system, and then assembles the optical system to obtain an image. Since the infrared detector has been non-uniformly corrected, after assembling the optical system, the non-uniformity of the obtained image to be processed is completely introduced by the optical system. That is to say, at this time, the energy distribution in the image completely depends on the transfer of the optical system, as Figure 2 and Figure 3 shown; considering that factors such as noise will cause interference, the gray levels of the maximum and minimum points where the optical axis is located in the image and the pixel points near them may not differ much. If the gray levels of the image are directly screened to determine the maximum and minimum points, large deviations are likely to occur and the centering accuracy cannot be improved. The present invention determines the maximum and minimum points of the image, that is, the position of the optical axis of the optical system in the image, by combining the actually obtained grayscale distribution with the transfer function corresponding to the optical system, and finally realizes the optoelectronic centering of the infrared detection imaging system, which can effectively improve the calibration and debugging accuracy of the optical axis and the electronic imaging center, and usually can be adjusted to a deviation of not more than 2 pixels.

[0056] Optionally, step 100 includes:

[0057] In the absence of the optical system, only use the infrared detector to image a uniform blackbody to obtain a background image.

[0058] Based on the uniformity of the obtained background image, the infrared detector is corrected until the uniformity of the background image meets the preset index.

[0059] In the above embodiment, the background image is obtained by imaging a uniform blackbody with an infrared detector. By calculating the uniformity index of the background image, the uniformity of the infrared detector can be evaluated, and then corrected according to the background image until the uniformity of the infrared detector meets the preset requirements.

[0060] Optionally, step 102 includes:

[0061] In the absence of the infrared detector, the transfer function of the optical system is measured by a transfer function meter.

[0062] In other embodiments, the transfer function of the optical system can also be obtained by other means, such as calling stored data, etc. The transfer function of the optical system can reflect the energy distribution of parallel light after passing through the optical system. The energy distribution trend of the transfer function is consistent with the distribution trend of the actual grayscale image obtained. Through the continuous transfer function, it is beneficial to accurately locate the point where the optical axis is located.

[0063] Step 104 is to obtain the imaging result of the assembled complex infrared detection imaging system. Optionally, after step 104 and before step 106, it further includes:

[0064] Filter each frame of the image to be processed.

[0065] Through the filtering process, it also helps to reduce the noise interference in the image to be processed and improve the centering accuracy.

[0066] Optionally, step 106 includes:

[0067] After superimposing the gray values of n frames of the images to be processed according to the coordinates and averaging them, the average value is used as the gray value of the gray distribution map; where n≥100; the corresponding expression is:

[0068]

[0069] where, X i represents the i-th frame of the image to be processed, Y0 represents the gray distribution map, and X i and Y0 are two-dimensional matrices of the same size.

[0070] In the above embodiment, by superimposing and smoothing the gray values of a large number of images to be processed, the noise can be effectively suppressed.

[0071] Optionally, step 108 includes:

[0072] Based on the gray distribution map, calculate the gradient data in the row direction and the column direction respectively;

[0073] For the row direction and the column direction, respectively, perform a descending sort based on the corresponding gradient data, and select the top M gradient values; M ≥ 10;

[0074] Take the points where the selected 2M gradient values are located as feature points, and the gradient values are the corresponding feature values. M is more preferably 30 or 50.

[0075] Furthermore, calculate the gradient data in the row direction or the column direction, and adopt the following method of adjacent two-pixel shift iteration, that is:

[0076]

[0077] where k i represents the gradient data of the i-th point in the row direction (or column direction), y i represents the gray value of the i-th point in the row direction (or column direction), y i+1 represents the gray value of the (i + 1)-th point in the row direction (or column direction), and the value range of i is determined by the total number of pixels in the row direction (or column direction) of the image.

[0078] In the above embodiment, the gradient distribution in the gray-scale distribution map is used as a feature. Correspondingly, in step 110, a mapping relationship between the gray-scale distribution map and the transfer function is established according to the gradient distribution feature, that is, by comparing the obvious gray-scale change trend, the corresponding relationship between the row-direction gray-scale distribution and the row-direction transfer function, and the corresponding relationship between the column-direction gray-scale distribution and the column-direction transfer function are established, so as to accurately locate the maximum and minimum points by using the transfer function subsequently.

[0079] Furthermore, step 108 further includes:

[0080] Based on the gray-scale distribution map, respectively perform a descending sort on the gray-scale values in the row direction and the column direction, and select the top L gray-scale values; L ≥ 5;

[0081] Take the points where the selected 2L gray-scale values are located as feature points, and the gray-scale values are the corresponding feature values.

[0082] The above embodiment uses the gradient distribution combined with the gray-scale maximum point as a feature to comprehensively determine the gray-scale distribution trend, which is beneficial to improving the accuracy of establishing the corresponding relationship between the gray-scale distribution and the transfer function.

[0083] Optionally, in step 112, if the optical system is a fully transmissive optical system, then determine the coordinates of the maximum value in the gray-scale distribution in the gray-scale distribution map;

[0084] If the optical system is a catadioptric optical system, then determine the coordinates of the minimum value in the gray-scale distribution in the gray-scale distribution map.

[0085] Step 112 corresponds the extreme value points of the transfer function to the grayscale distribution map to determine the coordinates of the point where the optical axis is located. For a fully transmissive optical system, its optical axis corresponds to the lowest point of the transmitted energy, while for a catadioptric optical system, its optical axis corresponds to the highest point of the transmitted energy. Determining the coordinates of this extreme value point also determines the position of the optical axis relative to the electronic target surface.

[0086] Optionally, step 114 includes:

[0087] Compare the size of the electronic target surface of the infrared detector and the size of the optical field of view of the optical system;

[0088] If the electronic calibration results in the loss of the optical field of view, adjust the relative position of the optical system and the infrared detector. Otherwise, use electronic calibration to make the coordinates of the extreme value point of the grayscale distribution coincide with the electronic center position of the infrared detector.

[0089] If there is a large margin between the electronic target surface and the optical field of view in the design, electronic calibration can be used to align the coordinates of the extreme value point of the grayscale distribution with the electronic center position of the infrared detector. If the redundancy between the optical field of view and the electronic target surface is very limited and part of the optical field of view cannot be received by the electronic target surface through electronic calibration, it is necessary to adjust the relative position of the optical system and the infrared detector to achieve centering.

[0090] The present invention also provides a method for assembling a complex infrared detection imaging system. During the stage of assembling the optical system and the infrared detector, the method for aligning the optical axis and the electronic center position of the complex infrared detection imaging system as described in any one of the above is used for calibration.

[0091] In summary, the present invention provides a method for aligning the optical axis and the electronic center position of a complex infrared detection imaging system and an assembling method. The present invention determines the position of the optical axis of the optical system in the image by actually obtaining the grayscale distribution in combination with the transfer function corresponding to the optical system, that is, the coordinates of the extreme value point of the grayscale distribution reflecting the transmitted energy distribution of the optical system. By making the coordinates of the extreme value point of the grayscale distribution coincide with the electronic center position of the infrared detector, it can effectively achieve the coincidence of the coordinates of the extreme value point of the grayscale distribution and the electronic center position of the infrared detector. Especially for an infrared detection imaging system using a complex catadioptric optical system, high-precision optical and electronic centering debugging can be realized, thereby improving the performance of the infrared detection imaging system.

[0092] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for optoelectronic centering of a complex infrared detection and imaging system, characterized in that, Including: When the optical system of the infrared detection imaging system is separated from the infrared detector, performing non-uniform correction on the infrared detector; Obtaining the transfer function corresponding to the optical system; After assembling the optical system and the infrared detector, obtaining multiple frames of images to be processed; Performing frame superposition processing on multiple frames of the images to be processed to obtain a gray-scale distribution map with noise suppression; Based on the gray-scale distribution map, determining the information of N feature points; The information of the feature points includes the eigenvalues of the feature points and the coordinates in the gray-scale distribution map; N is a positive integer not less than 20; Based on the information of the determined multiple feature points, establishing a mapping relationship between the gray-scale distribution map and the transfer function; Based on the maximum and minimum values of the transfer function and the mapping relationship between the gray-scale distribution map and the transfer function, determining the coordinates of the maximum and minimum points of the gray-scale distribution; According to the coordinates of the maximum and minimum points of the gray-scale distribution and the electronic center position of the infrared detector, performing optoelectronic centering of the infrared detection imaging system.

2. The optoelectronic centering method for a complex infrared detection and imaging system according to claim 1, characterized in that The performing non-uniform correction on the infrared detector includes: In the absence of the optical system, only imaging a uniform blackbody through the infrared detector to obtain a background image; Based on the uniformity of the background image, correcting the infrared detector until the uniformity of the background image meets the preset index.

3. The optoelectronic centering method of the complex infrared detection imaging system according to claim 1, characterized in that, The obtaining the transfer function corresponding to the optical system includes: In the absence of the infrared detector, measuring the transfer function of the optical system through a transfer function instrument.

4. The optoelectronic centering method of the complex infrared detection and imaging system according to claim 1, characterized in that, The performing frame superposition processing on multiple frames of the images to be processed includes: After superimposing the gray-scale values of n frames of the images to be processed according to the coordinates and then taking the average value as the gray-scale value of the gray-scale distribution map; where n≥100.

5. The optoelectronic centering method for a complex infrared detection and imaging system according to claim 1, characterized in that, The determining the information of N feature points based on the gray-scale distribution map includes: Based on the gray-scale distribution map, respectively calculating the gradient data in the row direction and the column direction; For the row direction and the column direction, respectively sorting the corresponding gradient data from large to small and selecting the first M gradient values; M≥10; Taking the points where the selected 2M gradient values are located as feature points, and the gradient values as the corresponding eigenvalues.

6. The optoelectronic centering method for a complex infrared detection and imaging system according to claim 1, characterized in that, The determining the coordinates of the maximum and minimum points of the gray-scale distribution includes: If the optical system is a fully transmissive optical system, determining the coordinates of the maximum value in the gray-scale distribution in the gray-scale distribution map; If the optical system is a catadioptric optical system, determining the coordinates of the minimum value in the gray-scale distribution in the gray-scale distribution map.

7. The optoelectronic centering method for the complex infrared detection and imaging system according to claim 1, characterized in that, The performing optoelectronic centering of the infrared detection imaging system includes: Comparing the electronic target surface size of the infrared detector and the optical field of view size of the optical system; If electronic calibration results in loss of the optical field of view, adjusting the relative position of the optical system and the infrared detector, otherwise using electronic calibration to make the coordinates of the maximum and minimum points of the gray-scale distribution coincide with the electronic center position of the infrared detector.

8. The optoelectronic centering method for the complex infrared detection and imaging system according to claim 5, characterized in that, The determining the information of N feature points based on the gray-scale distribution map further includes: Based on the gray-scale distribution map, respectively sorting the gray-scale values in the row direction and the column direction from large to small and selecting the first L gray-scale values; L≥5; Taking the points where the selected 2L gray-scale values are located as feature points, and the gray-scale values as the corresponding eigenvalues.

9. The optoelectronic centering method for the complex infrared detection and imaging system according to claim 1, wherein After obtaining multiple frames of images to be processed, before performing frame superposition based on the multiple frames of images to be processed, the method further includes: Performing filtering processing on each frame of the image to be processed.

10. A method for assembling a complex infrared detection and imaging system, characterized in that, In the stage of assembling the optical system and the infrared detector, the optical axis and the position of the electronics center are calibrated by using the method for photoelectric centering of the complex infrared detection imaging system according to any one of claims 1-9 above.

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