Patent ID: 7493034

Claim:
A focus detection system comprising: at least one line sensor array having a plurality of areas, each of which includes a plurality of pixels, wherein said line sensor array photoelectrically converts object light received by each of said plurality of pixels into an electric charge to accumulate said electric charge, and outputs said accumulated electric charge as an image signal; at least one monitor sensor array, positioned adjacent to said line sensor array, for monitoring an integral value of said line sensor array so as to output a monitor signal; a controller which terminates an integral operation of said line sensor array one of immediately after said monitor signal reaches a predetermined integration termination value and immediately after a lapse of a predetermined maximum integral time, whichever occurs first; and an amplifier which amplifies said image signal at an amplification factor determined in accordance with said monitor signal at said termination of said integral operation, wherein said controller detects said integral value of said line sensor array from said monitor signal output from said monitor sensor array during a monitoring operation thereof, continues to make said line sensor array perform said integral operation until a secondary maximum integral time elapses in the case where said controller determines, upon a lapse of a predetermined primary maximum integral time, that a value of said monitor signal is necessary to be amplified at an amplification factor greater than a maximum amplification factor of said amplifier, and increases said amplification factor of said amplifier after a lapse of said secondary maximum integral time, said secondary maximum integral time being longer than said primary maximum integral time.