Two-wavelength type respiratory gas concentration measuring apparatus

Claim 2

A two wavelength type respiratory gas concentration measuring apparatus comprising: a connector tube (2, 22) equipped with tube (2a, 210) end to be held in the mouth of an examinee (1) and an opposite open end (2b, 220), and having airtight windows (3, 23) provided between both ends of the connector tube (2, 22); a light source (4, 24) adapted to apply infrared rays in a light path passing transversely trough the connector tube (2, 22) by way of the windows (3, 23); a first filter (7, 27) which allows the transmission of a light component whose wavelength is such that it is absorbed by a particular gas of a respiratory gas breathed into the tube (2, 22) by the examinee (1); a second filter (8, 28) which allows the transmission of a light component whose wavelength is such that it is not absorbed by the particular gas; means (6; 26; 29) for alternately positioning the first filter (7, 27) and the second filter (8, 28) in the light path; photodetector means (10, 30) for converting the infrared rays transmitted through the filters (7, 27; 8, 28) to an electric signal, the photodetector means (10, 30) including a PbSe infrared-ray sensor; first detector means (11, 31) for detecting the light output of the first filter (7, 27) from the electric signal; second detector means (12, 32) for detecting the light output of the second filter (8, 28) from the electric signal; first power computing means (13, 33) for performing the power computation of the output of the second detector means (12, 32) with a power exponent m ; divider means (14, 34) for dividing the output of the first detector means (11, 31) by the output of the first power computing means (13, 33); DC level detector means (16, 36) for detecting the DC level of the photodetector means (10, 30) when no infrared rays are applied thereto; second power computing means (17, 37) for performing the power computation of the output of the DC-level detector means (16, 36) with a power exponent of 2(m-1); and multiplier means (18, 38) for multiplying the output of the second power computing means (17, 37) by the output of the divider means (14, 34); the power component m representing the ration of a temperature-­dependent coefficient α 1, with respect to the incident light quantity of the light component of the infrared rays whose wavelength is absorbed by the particular gas, of the variation with respect to temperature in resistance of the PbSe infrared-ray sensor to a temperature dependent cofficient α2, with respect to the incident light quantity of the light component of the infrared rays whose wavelength is not absorbed by the particular gas, of the variation with respect to temperature of the PbSe infrared-ray sensor, whereby the power exponent m and the temperature-dependent coefficients α1 and α2 are in the relationship: m = α₁ α₂ , the photodetector means (10, 30) supplying a constant voltage to the PbSe infrared-ray sensor, and detecting the current flowing through the infrared-ray sensor as an infrared-ray detection signal.

Claim 3

A two-wavelength type respiratory gas concentration measuring apparatus comprising: a connector tube (2, 22) equipped with an open tube end (2a, 210) to be held in the mouth of an examinee (1) and an opposite open end (2b, 220) and airtight windows (3, 23) provided between both ends of the connector tube (2, 22); a light source (4, 24) adapted to apply infrared rays in a path passing transversely through the connector tube (2, 22) by way of the windows (3, 23); a chopper (6, 26) having first and second filters (7, 27; 8, 28) situated thereon and adapted to alternately position in the light path the first filter (7, 27) which allows the transmission of a light component whose wavelength is such that it is absorbed by a particular gas and the second filter (8, 28) which allows the transmission of a light component whose wavelength is such that it is not absorbed by the particular gas; a photodetector (10, 30) including a PbSe infrared-ray sensor adapted to convert the infrared rays transmitted through the filters (7, 27; 8, 28) to an electric signal by means of the PbSe infrared-ray sensor; a first detector (11, 31) adapted to detect the output of the first filter (7, 27) from the electric signal; a second detector (12, 32) adapted to detect the output of the second filter (8, 28) from the electric signal; a first power computing circuit (13, 33) adapted to perform the power computation of the output of the second detector (12, 32) with a power exponent m ; a divider circuit (14, 34) for dividing the output of the first detector (11, 31) by the output of the first power computing circuit (13, 33); a DC level detector (16, 36) for determining the DC level of the photodetector (10, 30) when no infrared rays are applied; a second power computing circuit (17, 37) for performing the power computation of the output of the DC-level detector (16, 35) with a power exponent of 2(m-1); and a multiplier circuit (18, 38) for multiplying the output of the second power computing circuit (17, 37) by the output of the divider circuit (14, 34); the power component m representing the ratio of a temperature-­dependent coefficient α1, with respect to the incident light quantity of the light component of the infrared rays whose wavelength is absorbed by the particular gas, of the variation in resistance, which exponentially fluctuates with respect to temperature changes, of the PbSe infrared-ray sensor to a temperature-dependent coefficient α2, with respect to the incident light quantity of the light component of the infrared rays whose wavelength is not absorbed by the same particular gas, of the variation in resistance, which exponentially fluctuates with respect to temperature changes, of the PbSe infrared-ray sensor, whereby the power exponent m and the temperature-dependent coefficients α1 and α2 are in the relationship: m = α₁ α₂ the photodetector circuit (10, 30) supplying a constant voltage to the PbSe infrared-ray sensor, and detecting the current flowing through the infrared-ray sensor as an infrared-ray detection signal.

Claim 4

A two-wavelength type respiratory gas concentration measuring apparatus comprising: a connector tube (2, 22) equipped with an open tube end (2a, 210) to be held in the mouth of an examinee (1) and an opposite open end (2b, 220) and airtight windows (3, 23) provided between both ends of the connector tube (2, 22); a light source (4, 24) adapted to apply infrared rays in a path passing transversely through the connector tube (2, 22) by way of the windows (3, 23); a chopper (6, 26) having first and second filters (7, 27; 8, 28) situated thereon and adapted to alternately position in the light path the first filter (7, 27) which allows the transmission of a light component whose wavelength is such that it is absorbed by a particular gas and the second filter (8, 28) which allows the transmission of a light component whose wavelength is such that it is not absorbed by the particular gas; a photodetector (10, 30) including a PbSe infrared-ray sensor adapted to convert the infrared rays transmitted through the filters (7, 27; 8, 28) to an electric signal by means of the PbSe infrared-ray sensor; a first detector (11, 31) adapted to detect the output of the first filter (7, 27) from the electric signal; a second detector (12, 32) adapted to detect the output of the second filter (8, 28) from the electric signal; a first power computing circuit (13, 33) adapted to perform the power computation of the output of the second detector (12, 32) with a power exponent m ; a divider circuit (14, 34) for dividing the output of the first detector (11, 31) by the output of the first power computing circuit (13, 33); a DC level detector (16, 36) for determining the DC level of the photodetector (10, 30) when no infrared rays are applied; a second power computing circuit (17, 37) for performing the power computation of the output of the DC-level detector (16, 35) with a power exponent of 2(m-1); and a multiplier circuit (18, 38) for multiplying the output of the second power computing circuit (17, 37) by the output of the divider circuit (14, 34); the power component m representing the ratio of a temperature-­dependent coefficient α1, with respect to the incident light quantity of the light component of the infrared rays whose wavelength is absorbed by the particular gas, of the variation in resistance, which exponentially fluctuates with respect to temperature changes, of the PbSe infrared-ray sensor to a temperature-dependent coefficient α2, with respect to the incident light quantity of the light component of the infrared rays whose wavelength is not absorbed by the same particular gas, of the variation in resistance, which exponentially fluctuates with respect to temperature changes, of the PbSe infrared-ray sensor, whereby the power exponent m and the temperature-dependent coefficients α1 and α2 are in the relationship: m = α₁ α₂ the photodetector circuit (10, 30) supplying a constant voltage to the PbSe infrared-ray sensor, and detecting the current flowing through the infrared-ray sensor as an infrared-ray detection signal.