Study Of CCD Exposure Time Control Technique Based On Driving Timing

In recent years, with the development of remote sensing technology of spectral imaging, spectral imaging technology plays a more and more important role. The development of spectral remote sensing technology depends on a variety of technological progress. CCD(charge coupled device) has become the core field of spectral imaging device due to many advantages such as high sensitivity, low noise and high dynamic range.The quality of the image captured suffered severe degradation while the CCD detector is used in the environment with large brightness variation. Through the analysis, there are four factors affecting the luminance of the image: the aperture size, incident light intensity, exposure time and signal gain, to adjust the exposure time is the best choice. But for the frame transfer area array CCD imaging devices without an electronic shutter function, under the condition of the frame frequency determined,exposure time out of control is the technical bottlenecks of such the CCD detector encountered.For exposure time control level setting method and the charge excretion method two methods are proposed respectively in this paper for non-electronic shutter CCD imaging detector. Level setting method is accomplished by setting all the signal in the photosensitive areas for the same level of zero. The charge excretion method drained the excess charge within a frame time quickly by increasing the charge excretion state to control the exposure time.Two exposure time control method based on two different CCD detectors respectively the TH7888 A and the CCD**. First of all, the two exposure control methods of implementation are introduced, including the CCD hardware drive circuit and the design of the driver timing logic. For the hardware design, the reasonable schematic diagram design proposal is given. In terms of the timing logic design, a variety of CCD required timing signals are achieved through the VHDL language, and the simulation results are given. Secondly, under the laboratory condition, the experiment waveforms and images under different exposure time are acquired based on the proposed method after the establishment of the experiment platform. Further analysis of the test results demonstrates that the proposed method performs quite well in correctness and feasibility.