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Method and apparatus for measurement of light from illuminated specimen eliminating influence of background light

  • US 6,597,439 B1
  • Filed: 02/11/2000
  • Issued: 07/22/2003
  • Est. Priority Date: 02/12/1999
  • Status: Expired due to Fees
First Claim
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1. 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.

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