Patent ID: 7339154

Claim:
A level detector, comprising: a position detection device including a plurality of light receiving elements arranged in parallel with each other; a first amplifier device configured to amplify a light receiving signal output from a terminal of the position detection device; a first gain switching device configured to switch and set a gain of the first amplifier device; a first peak hold device configured to hold a peak value of an amplified signal output from the first amplifier device; an arithmetic control device configured to analyze a light receiving position of laser light received by the position detection device; a second amplifier device configured to amplify the peak value of the amplified signal held by the first peak hold device; and a second gain switching device configured to switch and set a gain of the second amplifier device, wherein the arithmetic control device analyzes the light receiving position of laser light received by the position detection device, based on a signal output from the second amplifier device.