CN109660743B - Method for realizing high dynamic range imaging of refrigeration type thermal infrared imager - Google Patents
Method for realizing high dynamic range imaging of refrigeration type thermal infrared imager Download PDFInfo
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Abstract
The invention discloses a method for realizing high dynamic range imaging of a refrigeration type thermal infrared imager, which comprises the steps of taking 8 frames of images as a cycle of images output by the refrigeration type thermal infrared imager, and then passing each frame of images through a non-uniformity correction module to obtain corrected images; then the corrected image passes through a divider with the divisor of 8, and the numerical value of the image is changed into one eighth of the original numerical value; summing all images in each cycle through a divider and storing the summed images into the LPDDR2, and when finishing the accumulation of 8 frames of images in the same cycle, starting the re-accumulation of the next cycle; and finally, when the first frame image and the fifth frame image of the same cycle arrive, respectively reading the images in the LPDDR2 and transmitting the images to a subsequent image processing module, and finally outputting the video images. The invention effectively expands the adaptability of the thermal infrared imager to scenes with large temperature change range, can acquire more scene information and expands the application field of the thermal infrared imager.
Description
Technical Field
The invention belongs to the field of infrared image processing, and particularly relates to a method for realizing high dynamic range imaging of a refrigeration type thermal infrared imager.
Background
The dynamic range of an original image generated by the thermal infrared imager is narrow, and the gray scale is concentrated. Due to the limited charge storage capacity of the integrating capacitor of the readout circuit in the focal plane detector assembly, the integration time of the detector is limited, when high-temperature objects in a scene are seen clearly, low-temperature objects may be submerged by noise, and when low-temperature objects are seen clearly, the high-temperature objects are saturated early.
Austin et al originally proposed the concept of infrared image superframe technology. The infrared image superframe technology is that a plurality of frames of images are obtained within a single frame of imaging time specified by an infrared imaging system, then saturated pixels of each pixel of a subframe with long integration time are replaced by pixels with short integration time, a new image is obtained and output within the single frame of image time, and therefore the purpose of widening the imaging range of the infrared thermal imager is achieved. However, the method has complex requirements on the algorithm, and cannot improve parameters such as the signal-to-noise ratio of the image.
On the basis, scholars at home and abroad carry out relevant research to obtain some achievements, and methods such as a superframe principle prototype based on an optical-mechanical device and infrared image superframe processing based on a high-speed numerical transmission circuit are provided, but the methods need to use complex optical devices and are not beneficial to technical popularization.
Disclosure of Invention
The invention aims to provide a method for realizing high dynamic range imaging of a refrigeration type thermal infrared imager, overcomes the defects that the thermal infrared imager has lower dynamic range and can not completely and clearly image a scene with large temperature change range, improves the signal-to-noise ratio of an output signal of an infrared imaging system,
the technical solution for realizing the purpose of the invention is as follows: a method for realizing high dynamic range imaging of a refrigeration type thermal infrared imager comprises the following steps:
step 1) taking 8 frames of images as a cycle of images output by a refrigeration type thermal infrared imager, wherein the integration time of each frame of image in the same cycle is different from each other;
step 2) each obtained frame image passes through a non-uniformity correction module, and non-uniformity of the image is removed to obtain a corrected image;
step 3), the corrected image passes through a divider with the divisor of 8, and the numerical value of the image is changed into one eighth of the original numerical value;
step 4) summing all images in each cycle passing through the divider in the step 3) and storing the summed images into the LPDDR2, and when the accumulation of 8 frames of images in the same cycle is completed, restarting the re-accumulation of the next cycle;
and 5) when the first frame image and the fifth frame image of the same cycle arrive, respectively reading the images in the LPDDR2 and transmitting the images to a subsequent image processing module, and finally outputting the video images.
Compared with the prior art, the invention has the following remarkable advantages:
(1) the imaging dynamic range of the infrared imaging system is improved, more information can be captured for scenes with larger temperature change range, and a better imaging effect is achieved.
(2) The signal-to-noise ratio and the sensitivity of the infrared imaging system are improved.
Drawings
FIG. 1 is a flow chart of a method for implementing high dynamic range imaging of a refrigerated thermal infrared imager in accordance with the present invention.
Fig. 2 is an image at each integration time and an image of high dynamic range imaging, where (a) is an image at a low integration time, (b) is an image at a high integration time, and (c) is an image obtained by a high dynamic range imaging method.
Detailed Description
The present invention is described in further detail below with reference to the attached drawing figures.
The refrigeration type thermal infrared imager performs high dynamic range imaging by enabling an infrared detector to output super-frame frequency images in different integration time, then adding all sub-frames and finishing the output of image data within a specified frame of image time. By the method, a wider temperature range and more scene information are obtained, and the signal-to-noise ratio and the sensitivity of the system are increased.
With reference to fig. 1, a method for implementing high dynamic range imaging of a refrigeration type thermal infrared imager includes the following implementation steps:
step 1) taking 8 frames of images as a cycle of images output by the refrigeration type thermal infrared imager, wherein the integration time of each frame of image in the same cycle is different from each other.
The method comprises the following steps of (1) enabling integration time of every eight frames of images to be different from each other:
1-1) setting a counter, the counter is positioned in the driving module, the counter counts from 0 to 7 in a cycle, and the counter is +1 every time a new image of one frame is input;
1-2) setting 8 different integration times in advance, taking down one integration time every time when the counter is +1, and so on until one cycle is finished;
1-3) when the next cycle starts, sequentially sending the 8 integration time to the refrigeration type thermal infrared imager.
The requirements for the detector input clock and the number of frames of the output image are as follows: the clock frequency for the detector is 6MHz, the detector outputs 200 frames of images per second, and a four-way output mode is adopted.
And 2) passing each frame of image through a non-uniformity correction module, removing the non-uniformity of the image, and obtaining a corrected image.
The method comprises the following steps of obtaining non-uniformity correction parameters:
2-1) setting the integration time as the first of 8 integration times, carrying out parameter calibration under the integration time to obtain a non-uniformity correction parameter, and turning to the step 2-2);
2-2) storing the non-uniformity parameter under the integration time into the LPDDR2, and turning to the step 2-3);
2-3) returning to 2-1) until all the non-uniformity correction parameters under the remaining 7 integration times are acquired and stored;
and calling the non-uniformity correction parameters to be selected according to the counting of the counter of the driving module, and calling the non-uniformity correction parameters under the corresponding integration time according to the counted numerical value when the image arrives.
And 3) the corrected image passes through a divider with the divisor of 8, and the numerical value of the image is changed into one eighth of the original numerical value. After the corrected image passes through the divider, if the remainder is 0, 1, 2 or 3, the result takes the quotient of the divider, and if the remainder is 4, 5, 6 or 7, the result takes the quotient of the divider plus 1.
And 4) summing all the images in each cycle passing through the divider in the step 3) and storing the summed images into the LPDDR2, and when the accumulation of 8 frames of images in the same cycle is completed, restarting the re-accumulation of the next cycle. The accumulation and storage mode of 8 frames of image data in each cycle comprises the following specific steps:
4-1) storing the first frame data in the first address space of LPDDR 2;
4-2) when the second frame data comes, reading out the data from the first address space in the LPDDR2, adding the data to the data of the second frame in turn, and storing the sum of the data into the second address space of the LPDDR 2;
4-3) when the third frame data comes, reading out the data from the second address space in the LPDDR2, adding the data to the data of the third frame in turn, and storing the sum of the data into the first address space of the LPDDR 2;
4-4) when the fourth frame data comes, reading out the data from the first address space in the LPDDR2, adding the data of the fourth frame to the data in sequence, and storing the sum of the obtained data in the second address space of the LPDDR 2;
4-5) when the fifth frame data comes, reading out the data from the second address space in the LPDDR2, adding the data of the fifth frame to the data in sequence, and storing the sum of the data into the first address space of the LPDDR 2;
4-6) when the sixth frame data comes, reading out the data from the first address space in LPDDR2, adding the data of the sixth frame to the data in sequence, and storing the sum of the data into the second address space of LPDDR 2;
4-7) when the seventh frame data arrives, reading out the data from the second address space in the LPDDR2, adding the data of the seventh frame to the data in sequence, and storing the sum of the obtained data in the first address space of the LPDDR 2;
4-8) when the eighth frame data comes, the data is read out from the first address space in LPDDR2, and the data of the eighth frame is sequentially added, and the sum of the obtained data is stored in the third address space of LPDDR 2.
And 5) when the first frame image and the fifth frame image of the same cycle arrive, respectively reading the images in the LPDDR2 and transmitting the images to a subsequent image processing module, and finally outputting the video images. Every time the counter counts 0 and 4, the data is read out from the third address of LPDDR2 and sent to the subsequent image processing module, the subsequent image processing module performs detail enhancement, histogram equalization, cropping, PAL display and the like on the data, and finally the image data is transmitted to the display device to output the image video.
Example 1
The method is characterized in that an input image with the resolution of 320 x 256 and the bit width of 14 bits is adopted, the model of an adopted FPGA is 5CEFA5C19I7, the adopted refrigeration type thermal infrared imager is MARS-LW-RM3 of SOFRADIR corporation, the clock frequency of a detector is 6MHz, one frame of image is output every 30000 clocks, and the detector adopts a four-way output mode.
The images are respectively imaged in three times by using the combination of the integration time parameters of 10 mus, 200 mus and eight different integration time parameters, and the final images obtained under different integration time conditions are acquired, and the obtained results are shown in (a), (b) and (c) of fig. 2, and the images show that a high-temperature object soldering iron exists in the observed scene. When the integration time is short, the soldering bit is not saturated, the relevant details can be seen, but the characters beside the soldering bit are blurred, the contrast is low, and the characters cannot be clearly distinguished; when the integration time is higher, the characters can be clearly distinguished, but the soldering iron is saturated and effective information cannot be obtained; when the high dynamic range imaging method under the multi-integration time is adopted for imaging, the soldering iron in the image is not saturated, the details can be distinguished, and the characters beside the soldering iron can be clearly distinguished, so that the purposes of improving the dynamic range of the thermal infrared imager and acquiring more effective information are achieved.
Claims (2)
1. A method for realizing high dynamic range imaging of a refrigeration type thermal infrared imager is characterized by comprising the following steps:
step 1) taking 8 frames of images as a cycle of images output by a refrigeration type thermal infrared imager, wherein the integration time of each frame of image in the same cycle is different from each other;
step 2) each obtained frame image passes through a non-uniformity correction module, and non-uniformity of the image is removed to obtain a corrected image;
step 3), the corrected image passes through a divider with the divisor of 8, and the numerical value of the image is changed into one eighth of the original numerical value;
step 4) summing all images in each cycle passing through the divider in the step 3) and storing the summed images into the LPDDR2, and when the accumulation of 8 frames of images in the same cycle is completed, restarting the re-accumulation of the next cycle;
step 5) when the first frame image and the fifth frame image of the same cycle arrive, respectively reading the images in the LPDDR2 and transmitting the images to a subsequent image processing module, and finally outputting a video image;
in the step 1), the integration times of the eight frames of images in the same cycle are different from each other, and the specific steps are as follows:
1-1) setting a counter, the counter is positioned in the driving module, the counter counts from 0 to 7 in a cycle, and the counter is +1 every time a new image of one frame is input;
1-2) setting 8 different integration times in advance, taking down one integration time every time when the counter is +1, and so on until one cycle is finished;
1-3) sequentially sending the 8 integration time to a refrigeration type thermal infrared imager when the next cycle starts;
the frame number requirements of the refrigeration type thermal infrared imager on the input clock and the output image are as follows:
the clock frequency for the refrigeration type thermal infrared imager is 6MHz, the refrigeration type thermal infrared imager outputs 200 frames of images per second, and a four-way output mode is adopted;
in the step 2), each obtained frame of image is passed through a non-uniformity correction module to remove the non-uniformity of the image, and the specific steps are as follows:
2-1) setting the integration time as the first of 8 integration times, carrying out parameter calibration under the integration time to obtain a non-uniformity correction parameter, and turning to the step 2-2);
2-2) storing the non-uniformity parameter under the integration time into the LPDDR2, and turning to the step 2-3);
2-3) returning to 2-1) until all the non-uniformity correction parameters under the remaining 7 integration times are acquired and stored;
2-4) when the image arrives, calling a non-uniformity correction parameter under the corresponding integration time according to the numerical value of the counter, and performing non-uniformity correction on the current image;
in the step 3), after the corrected image passes through the divider, if the remainder is 0, 1, 2 or 3, the result is taken as the quotient of the divider, and if the remainder is 4, 5, 6 or 7, the result is taken as +1 on the basis of the quotient of the divider;
in the step 4), the accumulation and storage mode of 8 frames of image data in each cycle includes the following specific steps:
4-1) storing the first frame data in the first address space of LPDDR 2;
4-2) when the second frame data comes, reading out the data from the first address space in the LPDDR2, adding the data to the data of the second frame in turn, and storing the sum of the data into the second address space of the LPDDR 2;
4-3) when the third frame data comes, reading out the data from the second address space in the LPDDR2, adding the data to the data of the third frame in turn, and storing the sum of the data into the first address space of the LPDDR 2;
4-4) when the fourth frame data comes, reading out the data from the first address space in the LPDDR2, adding the data of the fourth frame to the data in sequence, and storing the sum of the obtained data in the second address space of the LPDDR 2;
4-5) when the fifth frame data comes, reading out the data from the second address space in the LPDDR2, adding the data of the fifth frame to the data in sequence, and storing the sum of the data into the first address space of the LPDDR 2;
4-6) when the sixth frame data comes, reading out the data from the first address space in LPDDR2, adding the data of the sixth frame to the data in sequence, and storing the sum of the data into the second address space of LPDDR 2;
4-7) when the seventh frame data arrives, reading out the data from the second address space in the LPDDR2, adding the data of the seventh frame to the data in sequence, and storing the sum of the obtained data in the first address space of the LPDDR 2;
4-8) when the eighth frame data comes, the data is read out from the first address space in LPDDR2, and the data of the eighth frame is sequentially added, and the sum of the obtained data is stored in the third address space of LPDDR 2.
2. The implementation method of high dynamic range imaging of a refrigeration-type thermal infrared imager according to claim 1, characterized in that: in the step 5), every time the counter counts 0 and 4, the data is read from the third address of the LPDDR2 and sent to the subsequent image processing module, the subsequent image processing module performs detail enhancement, histogram equalization, cropping and PAL display on the data, and finally the image data is transmitted to the display device to output the image video.
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