Image signal processing unit

An image signal processing unit, comprising:

• an image signal receiver that receives an image signal generated by an imaging device that has a plurality of pixels generating pixel signal according to the amount of received light on said receiving surface, and whose receiving surface is divided into a plurality of pixel blocks, where a plurality of said pixels are arranged;
• a first addition block that generates a high-sensitivity signal by adding up said pixel signals generated by a plurality of said pixels arranged at a predetermined position in said pixel block;
• a compression block that generates a low-sensitivity signal, which increases proportionately to increasing said high-sensitivity signal, by compressing said high-sensitivity signal for each of said pixel blocks, so that a maximum signal level of said low-sensitivity signal is lower than a remainder of the difference between a maximum signal level of said pixel signal and a second threshold level;
• and
• a second addition block that adds up said high-sensitivity signal and said low-sensitivity signal when a signal level of said high-sensitivity signal is under said second threshold level, adds up said low-sensitivity signal and the threshold signal corresponding to said second threshold level when a signal level of said high-sensitivity signal is over said second threshold level.