Automatic exposure control method and device based on FPGA and suitable for space exploration imaging

Abstract

The invention relates to an automatic exposure control method and device based on an FPGA and suitable for space exploration imaging. The method includes the steps that the current-frame image average brightness is acquired through the main current-frame image average brightness, time of exposure is adaptively selected according to whether a difference value between the current-frame image average brightness and the expected image average brightness is positive or negative and is large or small, continuous frames are adopted for continuous loop iteration, and therefore the current-frame image average brightness reaches the expected image average brightness. The automatic exposure control device for conducting the automatic exposure control method comprises an optical lens, an APS sensor and the exposure control FPGA. According to the method and device, the technical problems existing in excessive exposure of a target image, segmentation of the target image and balance between the automatic exposure speed and stability in the existing space exploration imaging technology are solved, the image contrast ratio is increased, faster, more stable and more accurate automatic exposure control can be conducted in various space exploration light environments, and adaptive ability in the space exploration environment imaging process is improved.

Description

technical field [0001] The invention relates to the field of automatic exposure control in deep space detection technology, in particular to an FPGA-based automatic exposure control method and device suitable for space detection imaging. Background technique [0002] The automatic exposure control of the imaging device has a great influence on the output image quality. The goal of automatic exposure control is to ensure that the details of the dark part of the image of the subject are not lost, the bright part is not exposed, and the average brightness is suitable for human eyes. [0003] When the imaging device used in space exploration is working in orbit, it is very important whether the exposure time is appropriate. If the exposure time is too short, the scene will be very dark, and if the exposure time is too long, the scene will be saturated in brightness. Therefore, automatic exposure control is necessary, but automatic Exposure control is very complicated. If the ex...

AI Technical Summary

Problems solved by technology

[0005] First of all, in terms of the automatic exposure control method, ① the imaging device applied to space detection, when imaging the subject, cannot be set according to the scene because it is impossible to predict the lighting conditions, position, and image area occupied by the subject. Automatic Exposure Control Mode

②If the imaging device used in space detection uses the existing overall brightness of the image to control the exposure, if the brightness difference between the subject and the background is too large, the subject will be underexposed or overexposed

③ If the imaging device used in space detection adopts the reference brightness value control method of civilian cameras, the image is divided into blocks, and the brightness of each sub-image is used to set the reference brightness value, which can be obtained by adjusting the size of the aperture, of course Similarly, the reference brightness value can also be obtained by setting the shutter speed, and the imaging device applied to space detection is unmanned, and the aperture or shutter cannot be set

④ Some civilian cameras conduct exposure control by studying the relationship between brightness and exposure value under different lighting conditions. Imaging devices using space detection cannot pre-calibrate the brightness and exposure value, so this exposure control method cannot be used

⑤ Civilian automatic exposure control methods are based on the entire image for automatic exposure control. When the subject is small relative to the background, the subject will be overexposed

⑥The existing automatic exposure algorithm for the subject image, in order to segment the subject image, often uses a fixed brightness threshold for segmentation, but due to the temperature influence of the space detection imaging device, the fixed brightness threshold segmentation cannot adapt to various situations. Therefore, it is necessary to introduce the method of adaptive threshold segmentation into the automatic exposure control method.

[0009] The automatic exposure control method currently used in space detection and imaging devices in China, because the imaging device cannot identify the shooting subject, when the scene in the field of view is relatively complex, effective exposure control cannot be performed, and it is greatly disturbed by noise and non-shooting subjects, making the shooting in the image It is difficult for the brightness of the subject to be within an appropriate range, which increases the difficulty of automatic exposure control

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