| Summary: | 碩士 === 國立中正大學 === 電機工程研究所 === 88 === In this paper, we propose a new exposure control method for CMOS technology image sensor. The novel design of active pixel image sensor solves the problem that the dynamic range of image sensor is much less than the dynamic range of natural scene because of the restriction by circuit.
The exposure time of the image sensor is decided by the illumination of the chip. For raising the image dynamic range, the image sensor adjust the exposure time of the chip by the illumination.
Our design is based on the characteristic that the focus of taking picture by digital camera is generally at the center of the image. We detect the illumination of the chip by photo voltage of the pixel in the center at the pixel array. The exposure time of the pixel will be varied by the intensity of luminance. When the voltage of the pixel at the center of the pixel array approaches saturation, the control unit will enable the readout signal to read the photo signal out to prevent the image from overexposure or underexposure.
For understanding the photo property of CMOS image sensor, a 64x64 image array CMOS image sensor is fabricated in 0.6um one-poly-triple-metal technology. The chip area is 1800x1800um2. For verify our new design, a 128x128 image array CMOS image sensor is implemented in 0.35um technology and the chip area is 1800x1600um2. From the simulation result, the novel adaptive tuning mechanism will raise the dynamic range of the image sensor 1332.93 times, ie.62.5db. If the origin dynamic range of the image sensor is 70db, it will be 132.5db.
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