Optical system for a gas measurement system

• US 7,183,552 B2
• Filed: 03/03/2004
• Issued: 02/27/2007
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: Philips RS North America LLC (Koninklijke Philips N.V.)
• Original Assignee: RIC INVESTMENTS LLC (Respironics Incorporated)
• Inventors: Russell, James T
• Primary Examiner(s): Porta; David
• Assistant Examiner(s): TANINGCO, MARCUS H
• Application Number:
  US10/792,180
• Publication Number:
  US 20040256560A1
• Time in Patent Office: 1,091 Days
• Field of Search: 250/338.5
• US Class Current: 250/338.5
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis

Abstract

An improved optical configuration for use in a gas monitoring system. The optical system uses a high numerical aperture lens that maximizes capture of relatively large angle rays, thereby increasing the measured signal at the infrared radiation detector. In one embodiment of the present invention, a half-ball-type lens is provided proximal to the infrared radiation source in the gas measurement system. To further increase the measured signal at the infrared radiation detector and allow more efficient capture of the larger angle rays, materials that are reflective in the infrared band of interest are used, so that the walls of the sample cell act as a hollow light pipe.

Claims

1. A system adapted to analyze a concentration of a selected gas in a gas sample, the system comprising:

(a) a gas analyzer comprising;

(1) a gas analyzer housing,

(2) a receptacle defined in the gas analyzer housing,

(3) a source disposed in the gas analyzer housing and adapted to emit radiation of a specified intensity and wavelength along an optical path such that the radiation is absorbed by the selected gas in the gas sample being analyzed, and

(4) an infrared radiation detector disposed in the gas analyzer housing along the optical path in optical communication with the source and adapted to detect an intensity of the emitted radiation by the source after the radiation has passed through the gas sample; and

(b) a sample cell adapted to be disposed between the source and infrared radiation detector, wherein the sample cell includes;

(1) a sample cell housing adapted to be selectively disposed in the receptacle,

(2) a gas inlet disposed at a first end portion of the sample cell housing and on a first side of the sample cell,

(3) a gas outlet disposed at a second end portion of the housing generally opposite the first end portion and on a second side of the sample cell generally opposite the first side of the sample cell, and

(4) a gas flow passage defined in the sample cell through at least a portion of the sample cell housing between the gas inlet and the gas outlet, wherein the gas flow passage is generally parallel to the optical path between the source and the detector such that the gas flow passage defines a sample chamber, wherein a length of the gas flow passage defining the sample chamber is greater than a width of the gas flow passage, and wherein the gas inlet, the gas outlet, and the gas flow passage are disposed in a “

Z”

configuration in which at least one angle in the “

Z”

configuration through which gas passes is less than 90°

, and wherein at least a portion of a wall defining the gas flow passage includes an infrared reflective surface so as to direct rays of radiation from the source to the infrared radiation detector generally along the optical path.

2. The system of claim 1, wherein the infrared reflective surface is selected from group consisting of aluminum and gold.

3. The system of claim 1, wherein the infrared reflective surface comprises a high index material.

4. A system for analyzing the concentration of a selected gas in a gas sample, comprising:

(a) a gas analyzer comprising;

(1) a gas analyzer housing,

(2) a receptacle defined in the gas analyzer housing,

(3) a source disposed in the gas analyzer housing and adapted to emit radiation of a specified intensity and wavelength such that the radiation is absorbed by the selected gas in the gas sample being analyzed,

(4) a high numerical aperture-lens disposed in the gas analyzer housing so as to receive radiation from the source and direct the emitted rays in a manner to be substantially parallel to each other, and

(5) an infrared radiation detector disposed in the gas analyzer housing in optical communication with the emitter and adapted to detect an intensity of the emitted radiation by the source after the radiation has passed through the gas sample; and

(b) a sample cell disposed between the source and the infrared radiation detector, wherein the sample cell includes;

(1) a sample cell housing adapted to be selectively disposed in the receptacle,

(2) a gas inlet disposed at a first end portion of the sample cell housing,

(3) a gas outlet disposed at a second end portion of the sample cell housing, and

(4) a gas flow passage is defined in the sample cell through at least a portion of the sample cell housing between the gas inlet and the gas outlet, wherein the gas flow passage is generally parallel to an optical path between the source and the detector such that the gas flow passage defines a sample chamber, wherein the gas inlet, the gas outlet, wherein the gas flow passage is disposed in a “

Z”

configuration in which at least one angle in the “

Z”

configuration through which gas passes is less than 90°

, and wherein a length of the gas flow passage defining the sample chamber is greater than a width of the gas flow passage.