Image signal processing unit

Abstract

An image signal processing unit comprising an image signal receiver, a first addition block, a compression block, and a determination block, is provided. The image signal receiver receives an image signal. The image signal is generated by an imaging device. The imaging device has a plurality of pixels generating pixel signal. A receiving surface of the imaging device is divided into a number of pixel blocks. A number of pixels are arranged in the pixel block. The first addition block generates high-sensitivity signal by adding up the pixel signals generated by some pixels arranged at a predetermined position in the pixel block. The compression block generates low-sensitivity signal by compressing the high-sensitivity signal so that the low-sensitivity signal is lower than the maximum signal level of the pixel signal. The determination block determines whether a signal level of the high-sensitivity signal is over the threshold level The low-sensitivity signal is output if the signal level of the high-sensitivity signal is over the threshold level. Alternatively, the high-sensitivity signal is output if the signal level of the high-sensitivity signal is under the threshold level.