Interference filter transmission wavelength scanning photometer

• US 20020190211A1
• Filed: 10/26/2001
• Published: 12/19/2002
• Est. Priority Date: 02/28/2000
• Status: Active Grant

• Current Assignee: Nikkiso Company Limited
• Original Assignee: Atsuo Watanabe
• Inventors: Watanabe, Atsuo
• Granted Patent: US 6,747,276 B2
• Time in Patent Office: Days
• US Class Current: 250/339.07
• CPC Class Codes: G01J 3/06 Scanning arrangements arrangements for order-selection
• CPC Class Codes: G01J 3/12 Generating the spectrum; Monochromators
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• CPC Class Codes: G01N 2021/317 Special constructive features
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence

Abstract

An interference filter transmission wavelength scanning photometer wherein the angle of inclination of an interference filter (3) is periodically varied, the wavelength of the light to be transmitted is modulated with the periodical variation centered at the maximum absorption wavelength of the interesting component, the variation of the intensity of the light transmitted through a sample is extracted by an infrared sensor (11) as an electrical signal. The time between the rise and fall zero cross points of the AC component of the electric signal is determined by a microprocessor (16), the ratio (T−2T₁)/T. is calculated from the full period T (time for every other zero cross point of the AC component) and half period T₁ (the time for every zero cross point of the AC component) obtained from the above determined time, and the concentration of the interesting component is determined from the variation of the result of the calculation of the ratio, thereby quantitatively determining the component without interfering of the coexistent components.

Claims

1. An interference filter transmission wavelength scanning photometer for determining concentration of an interesting component in a sample without interfering of the coexistent components by applying the light absorption of the interesting component comprising:

a light source, an interference filter which has means scanning transmission wavelength periodically, an infrared sensor and a zero cross detector;

said photometer having functions to determine concentration of an interesting component in a sample by operations comprising the steps of;

deciding range of scanning the transmission wavelength of said interference filter, so that center of small change of wavelength induced by scanning the transmission wavelength periodically is equal to an absorption wavelength of said interesting component;

detecting intensity of light beam from said light source as an electric signal by said infrared sensor in which light beam is put, after transmitting through said interference filter and transmitting or reflecting on said sample put front or rear of said interference filter;

obtaining a full period T (time for every other zero cross point of the AC component) and half period T₁ (time for every zero cross point of the AC component) which said zero cross detector takes out of the AC component of said electric signal;

determining concentration of said interesting component by calculating a ratio

(T−

2T₁)/T.

2. The interference filter transmission wavelength scanning photometer according to the claim 1, wherein the transmission wavelength is scanned by swinging an interference filter periodically as inclining the normal of said interference filter to the optical axis.