Patent ID: 6747276
Filing Date: 2004-06-08
Classification: G01J,G01N

Abstract:
An interference filter transmission wavelength scanning photometer for determining a concentration of an interesting component in a sample without interference from coexistent components by measuring the light absorption of the interesting component, said photometer comprising:a light source; an interference filter operable to scan a transmission wavelength periodically; an infrared sensor; and a zero cross detector; said photometer having functions to determine the concentration of the interesting component in the sample by operations comprising: deciding a range of scanning the transmission wavelength of said interference filter so that a center of a small change in a wavelength induced by scanning the transmission wavelength periodically is equal to an absorption wavelength of the interesting component; detecting an intensity of a light beam output from said light source as an electric signal by said infrared sensor in which the light beam is provided to after the light beam is transmitted through said interference filter and after the light beam is transmitted or reflected on the sample placed to the front or rear of said interference filter; obtaining a full period T, which is a period of time between every other zero cross point of an AC component of the electric signal, and a half period T1, which is a period of time between each zero cross point of the AC component of the electric signal which said zero cross detector is operable to detect from the electric signal; and determining the concentration of the interesting component by calculating a ratio expressed by (Tâˆ’2T1)/T.