CN118429209A - TDI (time delay and integration) mechanism-based long-wave thermal infrared imager image sawtooth eliminating method and system - Google Patents
TDI (time delay and integration) mechanism-based long-wave thermal infrared imager image sawtooth eliminating method and system Download PDFInfo
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Abstract
The invention discloses a TDI (time delay and integration) -mechanism-based long-wave thermal infrared imager image sawtooth eliminating method and system, which belong to the field of infrared imaging, and the method comprises the following steps: preliminary processing of detector pixel image signals is achieved through the FPGA, and the length and the number of columns of saw teeth are judged according to the detector pixel image signals after the preliminary processing; the FPGA receives a cache delay column number instruction which is sent by the upper computer and is determined based on the sawtooth length column number, and the data of odd lines of the detector is read out in advance or read out in the column determined by the cache delay column number instruction by adjusting the time sequence of a read-write control signal in the FIFO data cache; judging whether the image saw-tooth is reduced or increased, and selecting a proper cache delay column number instruction according to the image saw-tooth eliminating effect so as to finish the online adjustment of the image saw-tooth. The invention does not need to carry out non-uniformity correction again, and does not interrupt the image during target detection.
Description
Technical Field
The invention belongs to the field of infrared imaging, and particularly relates to a refrigerating long-wave thermal infrared imager image sawtooth eliminating method based on a TDI mechanism. And more particularly, to a method and system for online adjustment of image saw teeth of a thermal infrared imager equipped with 768 x 8 cryogenic long wave detector based on TDI mechanism.
Background
The long-wave thermal infrared imager based on a Time Delay Integration (TDI) mechanism is widely applied to the fields of military, aviation and aerospace, and can realize a large imaging field of view and higher spatial resolution simultaneously through optical scanning. The use environment condition of the military thermal infrared imager is harsh, the working environment temperature span is large, and the military thermal infrared imager generally works in an environment of-40 ℃ to +65 ℃. When imaging in a wider environment temperature range, due to the problem of matching precision between the TDI and optical scanning, when imaging a scene, the edge of the scene in the infrared image always presents a saw tooth shape, thereby influencing the look and feel of the image and the extraction and identification of a small target.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention aims to provide an online adjustment method and an online adjustment system for image saw teeth of 768 multiplied by 8 refrigeration long-wave thermal infrared imager based on TDI mechanism in actual use.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for removing image aliasing of a long-wave thermal infrared imager based on a TDI mechanism, comprising:
preliminary processing of detector pixel image signals is achieved through the FPGA, and the length and the number of columns of saw teeth are judged according to the detector pixel image signals after the preliminary processing;
The FPGA receives a cache delay column number instruction which is sent by the upper computer and is determined based on the sawtooth length column number, and the data of odd lines of the detector is read out in advance or read out in the column determined by the cache delay column number instruction by adjusting the time sequence of a read-write control signal in the FIFO data cache;
judging whether the image saw-tooth is reduced or increased, and selecting a proper cache delay column number instruction according to the image saw-tooth eliminating effect so as to finish the online adjustment of the image saw-tooth.
In some alternative embodiments, the preliminary processing of the detector pixel image signals by the FPGA includes:
and (3) caching the image data of the odd lines of the detector by using the FIFO in the FPGA, and after the even lines are sensitized to the same target, parallelly sending the detector data of the odd lines and the even lines into 16-channel data synthesis and sequencing processing, and sequentially synthesizing the 16-channel parallel image data into 1-channel serial image data.
In some alternative embodiments, the TDI mechanism-based image aliasing cancellation method is applied to 768×8 refrigerated long-wave thermal infrared imagers.
In some alternative embodiments, the determining the length and the number of the saw-tooth columns according to the primarily processed image signals of the detector pixels includes:
Determining that imaging information of even rows on the target lags behind the spatial distance L of odd rows by l=7×54um+108 um=486 um;
Because the center distance between adjacent pixels of the 768×8 refrigeration long-wave infrared thermal imager is 54um, the scanning step length is 54 um/3=18um, the scanning step length is 1 column, and the theoretical total column number of imaging of even lines to the target is determined to be 27 columns behind odd lines by 486um/18 um=27.
In some alternative embodiments, the number of columns determined by the cache latency column number instruction determined based on the sawtooth length column number is a column number adjusted based on 27 columns.
According to another aspect of the present invention, there is provided a TDI-based long-wave thermal infrared imager image aliasing cancellation system, including:
The data processing module is used for realizing the preliminary processing of the image signals of the detector pixels through the FPGA;
the column number determining module is used for judging the length column number of the saw teeth according to the initially processed detector pixel image signals;
The adjusting module is used for receiving a cache delay column number instruction which is sent by the upper computer and is determined based on the sawtooth length column number by the FPGA, and leading the data of the odd rows of the detector to be read out in advance of the column number which is determined by the cache delay column number instruction or read out after the column number which is determined by the cache delay column number instruction by adjusting the time sequence of a read-write control signal in the FIFO data cache;
and the adjusting module is used for judging whether the image saw teeth are reduced or increased, and selecting a proper cache delay column number instruction according to the image saw tooth eliminating effect so as to finish the online adjustment of the image saw teeth.
In some optional embodiments, the data processing module is configured to buffer the image data of the odd lines of the detector with FIFO in the FPGA, send the detector data of the odd lines and the even lines into the 16-channel data synthesis and sequencing process in parallel after the even lines are sensitized to the same target, and synthesize the 16-channel parallel image data into 1-channel serial image data in sequence.
In some alternative embodiments, the TDI mechanism-based image aliasing cancellation method is applied to 768×8 refrigerated long-wave thermal infrared imagers.
In some alternative embodiments, the column number determination module is configured to:
Determining that imaging information of even rows on the target lags behind the spatial distance L of odd rows by l=7×54um+108 um=486 um;
Because the center distance between adjacent pixels of the 768×8 refrigeration long-wave infrared thermal imager is 54um, the scanning step length is 54 um/3=18um, the scanning step length is 1 column, and the theoretical total column number of imaging of even lines to the target is determined to be 27 columns behind odd lines by 486um/18 um=27.
In some alternative embodiments, the number of columns determined by the cache latency column number instruction determined based on the sawtooth length column number is a column number adjusted based on 27 columns.
In general, the above technical solutions conceived by the present invention, compared with the prior art, enable the following beneficial effects to be obtained:
The invention designs an online adjustment mode of image saw teeth for 768×8 long-wave thermal infrared imagers based on a TDI mechanism. The image saw tooth size can be adjusted on line by sending an instruction through the upper computer. The method can be applied to other long-wave or medium-wave refrigeration infrared detectors based on TDI mechanism types, such as 288×4, 480×6, 576×6, 768×8, 1024×6 and other infrared detectors. According to the invention, no thermalization optical lens is required to be redesigned, the motor rotating speed of the scanning swing mirror in the internal scanning mode is not changed, the turntable speed of the photoelectric system in the circumferential scanning mode is not changed, the integration period of the infrared detector is not changed, and the saw teeth at the scene edge of the infrared image caused by temperature change can be effectively eliminated. According to the invention, the upper computer sends the related instructions to carry out online adjustment on the image saw teeth, so that the non-uniformity correction on the infrared image is not needed, and the continuity of observing and aiming and tracking of the target is ensured. The method designed by the invention is applied to a multi-type infrared warning system and an infrared photoelectric system product, has good sawtooth eliminating effect and is approved by users.
Drawings
FIG. 1 is a schematic diagram of a refrigeration long-wave 768×8 infrared detector imaging a target according to an embodiment of the present invention;
FIG. 2 is a detail view of sawtooth of a cryogenic long-wave 768×8 thermal infrared imager provided by an embodiment of the invention;
FIG. 3 is a detail view of the cooling long wave 768×8 thermal infrared imager for eliminating saw teeth provided by the embodiment of the invention;
Fig. 4 is a flowchart of an implementation of a method for eliminating image aliasing of a long-wave thermal infrared imager according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The scanning line type refrigeration long wave infrared detector comprises a multi-stage Time Delay Integration (TDI) link, such as 288×4, 480×6, 576×6 and 768×8 detectors, wherein the TDI stages are 4 stages, 6 stages and 8 stages respectively. The invention uses a refrigeration long wave 768 multiplied by 8 detector as a test object for verification. As shown in fig. 1, the 768×8 detector is composed of 768×8 photosensor array divided into two sub-arrays of parity, which are arranged separately in the horizontal direction and staggered in the vertical direction. Each sub-array has 384 rows of 8 pixels each and the readout circuitry performs Time Delay Integration (TDI) on the 8 pixels of each row.
The invention relates to a 768 multiplied by 8 refrigeration long-wave thermal infrared imager image sawtooth online adjustment method based on a TDI mechanism based on a certain type thermal infrared imager from the engineering practical application perspective. The method for changing the space in time can effectively eliminate scenery image saw teeth, truly restore details of the edges of small targets, greatly improve the look and feel of images, and can be widely applied to equipment such as infrared searching and tracking (INFRARED SEARCH AND TRACK DEVICE, IRST) systems, infrared photoelectric systems and the like.
The invention designs a 768 multiplied by 8 refrigeration long wave infrared thermal imager image sawtooth online adjustment method according to the pixel distribution and TDI mechanism characteristics of the refrigeration long wave 768 multiplied by 8 infrared detector. The method does not need to carry out non-uniformity correction again, and the image is not interrupted when the target is detected.
More specifically, a schematic diagram of imaging a target by using a refrigeration long-wave 768×8 infrared detector is shown in fig. 1, and under the condition that the TDI direction is determined, a rod-shaped target moves from a position a to a position B, an odd-line image element firstly sensitively images the target, and an even-line image element later than the odd-line image element images the target. The spatial distance of the pixels is calculated, namely, the spatial distance L of the imaging information of the even line to the target behind the odd line is:
7×54um+108um＝486um
More specifically, since the detector is of a 3-stage TDI structure, the center distance between adjacent pixels is 54um, so the scanning step length is 54 um/3=18um. The scan step is referred to as 1 column. The even rows therefore image the target behind the odd rows by the theoretical total column number as follows:
486um/18um＝27
More specifically, the delay time of the odd row data and the even row data is desirably 27 column periods. Due to the influence of the ambient temperature, the focal length of the optical system changes, saw teeth appear at the scene edge in the infrared image, and the theoretical delay column number between the odd-numbered rows and the even-numbered rows is not suitable.
More specifically, in the invention, the reverse angle is considered, the space physical interval of pixel distribution on the detector is innovatively converted into time delay, namely, the theoretical total column number of even rows, which is determined according to the space distance L, and the imaging of the target is behind the theoretical total column number of odd rows is theoretically taken as the time delay, so that the purpose of eliminating image saw teeth is achieved.
More specifically, by adjusting the timing sequence of the read-write control signal in the FIFO data buffer module, the data of the odd-numbered rows of the detector are read out in advance by several columns or read out in later columns. The user can select a proper cache column number according to the sawtooth adjusting effect in the use scene. And adjusting the theoretical total column number of the target imaging behind the odd number of the lines according to the even number of lines determined by the space distance L, for example, sending an instruction of 26 columns, 25 columns or 28 columns, 29 columns or the like of the caching delay column number through an upper computer, and then adjusting and eliminating the infrared image saw teeth on line.
According to the method, test verification is carried out on a thermal infrared imager provided with 768 multiplied by 8 detectors, the infrared image detail image with saw teeth of the thermal infrared imager is shown in fig. 2, the infrared image detail image with saw teeth eliminated by the thermal infrared imager is shown in fig. 3, and therefore the effectiveness of online adjustment and elimination of the saw teeth of the infrared image is verified by using the method.
As shown in fig. 4, the thermal infrared imager is normally energized.
In step S1, the FPGA realizes the preliminary processing of the pixel image signals of the detector, and utilizes the FIFO module in the FPGA to buffer the image data of the odd lines of the detector, and after the even lines are sensitized to the same target, the detector data of the odd lines and the even lines are sent in parallel to the 16-channel data synthesis and sorting processing module, and the 16-channel parallel image data are synthesized into 1-channel serial image data in sequence. And controlling the read-write signal time sequence of the FIFO, writing the data of the odd-numbered lines of the detector into the FIFO, waiting for the even-numbered lines of the detector to finish photoelectric conversion of the target, and then reading the data of the odd-numbered lines of the detector.
In step S2, under the influence of the ambient temperature, the focal length of the optical system changes, and a sawtooth appears at the scene edge in the image of the cryogenic long-wave 768×8 thermal infrared imager, and the number of sawtooth length columns is primarily determined.
In step S3, an upper computer is used to send instructions on line, and +1, +2, +3, and the like are sent, or-1, -2, and-3 are sent, respectively. And the FPGA internally adjusts the time sequence of read-write control signals in the FIFO data buffer module to enable the data of odd lines of the detector to be read out in a plurality of columns in advance or read out in a plurality of columns later.
In step S4, it is determined whether or not the image jaggies are reduced or increased, and an appropriate jaggy adjustment parameter is selected according to the image jaggy removal effect.
In step S5, online adjustment of the image saw-tooth of the cryogenic long-wave 768×8 thermal infrared imager is completed.
It should be noted that each step/component described in the present application may be split into more steps/components, or two or more steps/components or part of operations of the steps/components may be combined into new steps/components, according to the implementation needs, to achieve the object of the present application.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. The method for eliminating the image saw tooth of the long-wave thermal infrared imager based on the TDI mechanism is characterized by comprising the following steps of:
preliminary processing of detector pixel image signals is achieved through the FPGA, and the length and the number of columns of saw teeth are judged according to the detector pixel image signals after the preliminary processing;
The FPGA receives a cache delay column number instruction which is sent by the upper computer and is determined based on the sawtooth length column number, and the data of odd lines of the detector is read out in advance or read out in the column determined by the cache delay column number instruction by adjusting the time sequence of a read-write control signal in the FIFO data cache;
judging whether the image saw-tooth is reduced or increased, and selecting a proper cache delay column number instruction according to the image saw-tooth eliminating effect so as to finish the online adjustment of the image saw-tooth.
2. The method according to claim 1, wherein said preliminary processing of detector pixel image signals by an FPGA comprises:
and (3) caching the image data of the odd lines of the detector by using the FIFO in the FPGA, and after the even lines are sensitized to the same target, parallelly sending the detector data of the odd lines and the even lines into 16-channel data synthesis and sequencing processing, and sequentially synthesizing the 16-channel parallel image data into 1-channel serial image data.
3. The method according to claim 1 or 2, wherein the TDI mechanism-based long-wave thermal infrared imager image aliasing cancellation method is applied to 768 x 8 refrigerated long-wave thermal infrared imagers.
4. A method according to claim 3, wherein said determining the number of columns of the length of the saw tooth based on the preliminary processed detector pixel image signals comprises:
Determining that imaging information of even rows on the target lags behind the spatial distance L of odd rows by l=7×54um+108 um=486 um;
Because the center distance between adjacent pixels of the 768×8 refrigeration long-wave infrared thermal imager is 54um, the scanning step length is 54 um/3=18um, the scanning step length is 1 column, and the theoretical total column number of imaging of even lines to the target is determined to be 27 columns behind odd lines by 486um/18 um=27.
5. The method of claim 4, wherein the number of columns determined by the cache latency column number based on a saw tooth length column number determination instruction is a column number adjusted based on 27 columns.
6. The system for eliminating image aliasing of a long-wave thermal infrared imager based on a TDI mechanism is characterized by comprising:
The data processing module is used for realizing the preliminary processing of the image signals of the detector pixels through the FPGA;
the column number determining module is used for judging the length column number of the saw teeth according to the initially processed detector pixel image signals;
The adjusting module is used for receiving a cache delay column number instruction which is sent by the upper computer and is determined based on the sawtooth length column number by the FPGA, and leading the data of the odd rows of the detector to be read out in advance of the column number which is determined by the cache delay column number instruction or read out after the column number which is determined by the cache delay column number instruction by adjusting the time sequence of a read-write control signal in the FIFO data cache;
and the adjusting module is used for judging whether the image saw teeth are reduced or increased, and selecting a proper cache delay column number instruction according to the image saw tooth eliminating effect so as to finish the online adjustment of the image saw teeth.
7. The system of claim 6, wherein the data processing module is configured to buffer the image data of the odd-numbered rows of the detector with FIFO in the FPGA, send the detector data of the odd-numbered rows and the detector data of the even-numbered rows into the 16-channel data synthesis and sorting process in parallel after the even-numbered rows are sensitized to the same target, and synthesize the 16-channel parallel image data into 1-channel serial image data in sequence.
8. The system according to claim 6 or 7, wherein the TDI mechanism-based long-wave thermal infrared imager image aliasing cancellation method is applied to 768 x 8 refrigerated long-wave thermal infrared imagers.
9. The system of claim 8, wherein the column number determination module is configured to:
Determining that imaging information of even rows on the target lags behind the spatial distance L of odd rows by l=7×54um+108 um=486 um;
Because the center distance between adjacent pixels of the 768×8 refrigeration long-wave infrared thermal imager is 54um, the scanning step length is 54 um/3=18um, the scanning step length is 1 column, and the theoretical total column number of imaging of even lines to the target is determined to be 27 columns behind odd lines by 486um/18 um=27.
10. The system of claim 9, wherein the number of columns determined by the cache latency column number based on the sawtooth length column number determination instruction is a column number adjusted based on 27 columns.
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