Method for full-frame type area array charge coupled device (CCD) camera to acquire target image with very-low radiance

Abstract

The invention relates to a method for a full-frame type area array charge coupled device (CCD) camera to acquire a target image with very-low radiance. In the method, an optical subsystem is configured for the full-frame type area array CCD for imaging, and a processing link of signals output by the CCD comprises an analog signal processing part and a digital signal processing part. The analog signal processing part is mainly used for carrying out correlated double sampling, low noise amplification, clamping and analog-to-digital conversion. The digital signal processing part is provided witha video memory and a status monitor. After each exposure is finished, weak images obtained by the CCD are accumulated to the video memory; meanwhile, the number of saturated pixels in the video memory is monitored; if the saturated pixels reach a proportion, data in the memory and the accumulated exposure times are output, and an image data register and the status monitor are reset, otherwise, animage accumulation process is continued. The images acquired by the method have the advantages of high quality and wide applied dynamic range; and the method is used to meet the demand of continuously monitoring the very-low radiance targets.

Description

technical field [0001] The invention relates to a method for imaging with a CCD camera. Background technique [0002] Obtaining high-quality target images under very low illumination conditions is an important practical technology. The extremely weak illuminance mentioned here refers to the target radiance as low as 1.0×10 -8 W / cm 2 Below sr, the radiance of ordinary objects during the day is 5 to 7 orders of magnitude lower than that of ordinary objects during the day. [0003] There are two low-radiance target imaging technologies currently used on satellites, namely image intensifier technology and time-delay integration technology (ie TDI technology). [0004] When using the image intensifier technology, first, the image intensifier is difficult to adapt to the space environment, and the technical difficulty required is high; second, the linear region of the image intensifier response is too narrow, and the linearity is poor, so it cannot cover the dynamic range of cl...

AI Technical Summary

Problems solved by technology

However, this technology has obvious shortcomings for application. First, the satellite orbit height is only a few hundred kilometers, and the image swath is usually several hundred kilometers. When the swath exceeds 1,000 kilometers, the distortion at the edge of the image is too large for users to use; two. Because the movement of satellites is controlled by orbital mechanics, the revisit period of a single satellite is generally not less than 24 hours, so it is impossible to obtain continuous cloud coverage maps and cannot be used to monitor the evolution of weather systems

If it is necessary to monitor the evolution of the weather system, a multi-satellite network is bound to be required; third, due to the fast movement speed of the sun-synchronous polar-orbiting remote sensing satellites relative to the ground (generally about 7 kilometers per second), in each exposure time, the photogenerated charge It may even be less than the dark signal charge, so the signal-to-noise ratio of the image is not high, resulting in low image quality

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