US 6,747,276 B2 · Interference filter transmission wavelength scanning photometer

Abstract

An interference filter transmission wavelength scanning photometer operable to determine the concentration of an interesting component in a sample without interference from coexisting components by measuring the light absorption of the interesting component. An angle of inclination of an interference filter varies periodically and is centered at the maximum absorption wavelength of the interesting component. The wavelength of a transmitted light is modulated due to the periodical variation of the angle of inclination. Variation in the intensity of the light transmitted through a sample is extracted by an infrared sensor as an electric signal. The time between rise and fall zero cross points of an AC component of the electric signal is determined by a microprocessor. A ratio is calculated from a full period and a half period of the AC component. The concentration of the interesting component is determined from a variation in the calculation of the ratio.

Claims14

Dependent claims

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 (T−2T1)/T.

8 more elements

An interference filter transmission wavelength scanning photometer operable to determine a concentration of an interesting component in a sample without interference from coexisting components by measuring the light absorption of the interesting component, said photometer comprising:

a light source operable to output a light beam;
an interference filter operable to scan a transmission wavelength periodically within a range 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, and to pass the light beam outputted from said light source therethrough to be transmitted on the sample located to the front or rear of said interference filter;
an infrared sensor operable to receive the light beam outputted from said light source after the light beam is transmitted through said interference filter and transmitted or reflected on the sample, and to detect an intensity of the light beam upon receiving the light beam;
a zero cross detector operable to detect a full period T corresponding to a period of time between every other zero cross point of an AC component of the electric signal and a half period T1, corresponding to a period of time between each zero cross point of the AC component of the electric signal;
and
a determining unit operable to determine the concentration of the interesting component by calculating a ratio expressed by (T−2T1)/T.

3 more elements

Dependencies are inferred from the claim text.

Interference filter transmission wavelength scanning photometer

Life of this patent

Interference filter transmission wavelength scanning photometer

Life of this patent

Abstract

Claims14