| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that a light receiving element could not correctly measure the amount of light received by the effect of dark current or extraneous light in the known method in which an object to be measured is optically measured by irradiating the object with near infrared light and receiving transmitted light and reflected light. SOLUTION: Near infrared (laser) light LI is applied to an object 70 by pulse driving. The light is received as transmitted light or reflected light by a light detection means (photodetector) 21, and converted into a voltage signal. The detected voltage signal passes through an amplifier 23 with an appropriate gain, and then passes through a band-pass filter 24. The band-pass filter 24 is used that is capable of extracting a frequency component with bandwidth between 1/2 and 2 times as wide as the signal frequency. Thus, a particular sine wave from which dark current variable with temperature, spectrum light (extraneous light) other than near infrared light LI/LO to be measured and laser noise of a light-emitting element 12 and photodetector 21 have been removed is obtained, so that the amount of light received is detected by measuring a crest value. COPYRIGHT: (C)2008,JPO&INPIT
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