Optical system with an extended, imaged source

• US 5,714,759 A
• Filed: 02/23/1996
• Issued: 02/03/1998
• Est. Priority Date: 02/23/1996
• Status: Expired due to Fees

• Current Assignee: Datex-Ohmeda Incorporated (GE Healthcare Technologies, Inc.)
• Original Assignee: Ohmeda, Inc. (Linde Plc)
• Inventors: Nelson, Shari
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US08/605,973
• Time in Patent Office: 711 Days
• Field of Search: 250/339.02, 250/339.06, 250/339.13, 250/343
• US Class Current: 250/343
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0259 Monolithic
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis

Abstract

The source (12) has a heater element (122) sandwiched between elongate emitter plates (124 and 126). In operation, the source (12) is operated at temperatures in excess of 900° C. and, preferably, at least about 1200° C. to provide radiation in the 7-10 micrometer wavelength range. In one embodiment, the source (12) is used in conjunction with an elongate detector array (14) in a gas analyzer (10) for analyzing respiratory and anesthetic gases. Spherical mirrors (36a, 36b) and flat mirrors (38a, 38b) are employed to image the source (12) on the detector array (14). A linear variable filter (26) allows for analysis of the radiation at multiple wavelengths using detector array (14).

Claims

1. A respiratory and anesthetic gas analyzer, comprising:

an elongated source of infrared radiation for transmitting polychromatic infrared radiation that encompasses a 7 to 10 micrometer wavelength range, said elongated source having a first longitudinal axis;

a detector array for substantially simultaneously detecting said polychromatic radiation across the wavelength range and including a detector array surface, the detector array having a second longitudinal axis;

optical imaging means for defining an optical path for imaging said source onto and across said detector array surface, wherein infrared radiation from said source impinging on said detector array surface defines an image of said elongated source, and wherein the first longitudinal axis of the source, when imaged on the detector array surface, is aligned with the second longitudinal axis of said detector array;

a gas sample chamber, including a sample gas to be analyzed, disposed on the optical path.

2. The apparatus of claim 1, further comprising a linear variable filter disposed between the source and the detector array surface and having a center axis, the center axis being aligned with the first and second longitudinal axes when the source is imaged on the detector array surface.

3. The gas analyzer of claim 2, wherein the source, filter, and detector array are arranged in an aligned upstanding orientation.

4. The apparatus of claim 1, wherein said source comprises a substantially planar radiation emitter surface.

5. The apparatus of claim 1, wherein said source comprises two, oppositely facing substantially planar radiation emitter surfaces.

6. The apparatus of claim 1, wherein said source has a primary radiation band including the 7 to 10 micrometer wavelength range.

7. The apparatus of claim 1, wherein said source operates at a temperature greater than 900°

C.

8. The apparatus of claim 1, wherein said source operates at a temperature of at least about 1200°

C.

9. The apparatus of claim 1, wherein said detector surface is dimensioned to substantially match said image of said source.

10. A gas respiratory and anesthetic analyzer, comprising:

an elongated radiation source for emitting polychromatic radiation including the 7 to 10 micrometer wavelength range, the elongated radiation source having a first longitudinal axis;

a detector array for substantially simultaneously detecting the polychromatic radiation across the wavelength range and including a detector array surface, the detector array being aligned relative to a second axis;

optical imaging means for defining first and second optical paths from said source to said detector array, wherein radiation sequentially passing along the first and second optical paths and impinging on said detector surface defines an image of said source across said detector array surface such that the first longitudinal axis of the source, when imaged on the detector array surface, is aligned with the second axis; and

a gas sample chamber, including a sample gas to be analyzed, disposed on at least one of said first and second optical paths.

11. The gas analyzer of claim 10, further comprising a polychromatic filter disposed along at least one of the first and second optical path, the filter having a third longitudinal axis that is aligned with the first and second longitudinal axes.

12. The gas analyzer of claim 10, wherein said source comprises a substantially planar radiation emitter surface.

13. The gas analyzer of claim 10, wherein said source operates at a temperature greater than 900°

C.

14. The gas analyzer of claim 10, wherein said source operates at a temperature of at least about 1200°

C.

15. The gas analyzer of claim 10, wherein said detector surface is dimensioned to substantially match said image of said source.

16. The gas analyzer of claim 10, wherein said gas sample chamber is disposed between said optical imaging means and said detector.

17. The gas analyzer of claim 10, wherein a first radiation portion is passed along the first optical path and a second radiation portion is passed along the second optical path and the first and second radiation portions each have a common predetermined band of wavelengths.

18. A respiratory and anesthetic gas analyzer, comprising:

an elongate infrared radiation source, having a first longitudinal axis, for transmitting polychromatic infrared radiation including a wavelength band ranging from about 7 to about 10 micrometers;

a radiation detector array for substantially simultaneously receiving said infrared radiation across the wavelength range from said radiation source, said array having a plurality of radiation sensitive elements that are aligned relative to a second axis;

a polychromatic filter for filtering said infrared radiation from said radiation source, said filter including a plurality of filter portions having differing wavelength dependent radiation transmission characteristics, said filter being oriented such that each of said plurality of filter portions is optically associated with one of said plurality of radiation sensitive elements, the plurality of filter portions being aligned relative to a third axis;

optical means for defining an optical path for imaging said infrared source onto and across said radiation detector array and said polychromatic filter such that said infrared source is imaged simultaneously on the plurality of radiation sensitive elements and the plurality of filter portions, wherein said wavelength band of infrared radiation from said source impinging on said detector array and said plurality of filter portions defines a polychromatic image of said source such that said first longitudinal axis of said source, when imaged on said detector array, is aligned with said second axis of said array and said third axis of said plurality of filter portions; and

a gas sample chamber, wherein the detector array, polychromatic filter, and gas sample chamber are disposed on the optical path.

19. A method for analyzing respiratory and anesthetic gas comprising the steps of:

placing a sample gas in a sample chamber;

emitting polychromatic radiation encompassing a wavelength range of approximately 7 to 10 micrometers from an elongated source having a first longitudinal axis;

directing the radiation through the sample chamber;

imaging the polychromatic radiation source through the sample chamber and onto and across a radiation detector array having a plurality of radiation sensitive elements aligned to a second axis, wherein radiation across said wavelength range is substantially simultaneously detected;

aligning said first longitudinal axis of said source with said second axis of said radiation detector array;

filtering said radiation with a polychromatic filter having a plurality of filter portions having differing wavelength dependent transmission characteristics;

orienting said filter so that each of said plurality of filter portions is optically associated with one of said plurality of radiation sensitive elements.

20. The method for analyzing gas of claim 19 wherein the step of emitting radiation further comprises:

positioning a heating element and a substantially planar emitter plate in thermal contact to define said source;

connecting the heater element to a power source; and

operating the power source to heat the emitter plate at a temperature greater than 900°

C.