Patent ID: 6597439
Filing Date: 2003-07-22
Classification: G01N

Abstract:
An optical measurement method for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under background light having intensity which varies cyclically with a period, said method comprising steps of:(a) performing a first operation of measuring the first light for a first duration having a certain length and beginning at a first time, while illuminating the specimen with second light, to obtain a first measurement result; (b) performing a second operation of measuring the first light for a second duration having the same length as the first duration and beginning at a second time which is different from said first time by an integer multiple of said period, while illumination of the specimen is stopped, to obtain a second measurement result; and (c) subtracting said second measurement result from said first measurement result, to obtain a third measurement result which is not affected by said background light.