Infrared source

• US 5,369,277 A
• Filed: 10/17/1990
• Issued: 11/29/1994
• Est. Priority Date: 05/23/1990
• Status: Expired due to Term

• Current Assignee: RIC INVESTMENTS LLC (Respironics Incorporated)
• Original Assignee: NTC Technology, Inc. (Dixtal Medical, Inc.)
• Inventors: Graham, Paul K., Labuda, Lawrence L., Knodle, Daniel W.
• Primary Examiner(s): FIELDS, CAROLYN
• Application Number:
  US07/598,984
• Time in Patent Office: 1,504 Days
• Field of Search: 250/493.1, 250/351, 250/343, 250/504 R, 219/548, 219/553
• US Class Current: 250/343
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01N 2021/0346 Capillary cells; Microcells
• CPC Class Codes: G01N 21/0303 Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment G01N21/031 - G01N21/15 take precedence
• 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

Infrared radiation emitter units for gas analyzers and other applications. The emitter has a substrate with a film of electrically resistive, emissive material on one of its surfaces. The emitter is so mounted on an emitter unit base that it can freely expand as the emitter heats up. A lead frame commutator, employed to electrically connect the emitter to an external power source, also facilitates the assembly of the unit. A component with a plated, parabolic surface collimates and focuses into an appropriate beam the energy generated by the emitter.

Claims

1. A system for generating periodic pulses of infrared radiation, said system comprising:

an emitter means which is resistive to the flow of electrical current therethrough and can accordingly be heated to an elevated temperature and caused to emit infrared radiation by applying an electrical voltage thereacross; and

means for applying electrical pulses of first one, and then the opposite, polarity to said emitter means to heat said emitter means as aforesaid to effect the emission of said pulses of infrared radiation therefrom.

2. An infrared radiation source which includes an emitter means and a support for said emitter means, said emitter means including a substrate and an emissive, electrically resistive material on said substrate and said source also including means for fixing one end only of said substrate to said support, whereby said emitter means is free to expand and contract without resistance as said emissive material is respectively heated to an operating temperature and cools to a lower temperature.

3. An infrared radiation source as defined in claim 2:

which includes a base mounting said emitter means support and a mirror means for collimating infrared radiation emitted from said emitter means into a beam;

said mirror means having an axis of symmetry and the means for fixing said one end of the emitter means to said support having the capability of automatically aligning the midpoint of the emitter means emissive layer with the axis of symmetry of the mirror means as the emitter means is fixed to the support.

4. An infrared radiation source as defined in claim 3 in which:

the emitter means support has first and second, spaced apart, diametrically opposed means for respectively supporting the fixed and opposite, floating end of the emitter means;

the means for fixing said one end of the emitter means to the first of the supporting means comprises a layer of adhesive on that supporting means; and

there is an aperture through said support at the location occupied by the fixed end of said emitter means when the emissive layer of the emitter means is centered as aforesaid;

whereby, when said emitter means is assembled to said support, said adhesive will flow toward said aperture and draw the emitter means toward said aperture by surface tension but will stop at said aperture, thereby halting said emitter means with its emissive layer centered as aforesaid.

5. An infrared radiation source which comprises:

emitter means having a substrate;

a layer of an electrically resistive, emissive material on said substrate; and

first and second electrical terminals on said substrate and in electrical contact with said layer of emissive material at the opposite ends thereof;

a base;

a lead frame with two electrically isolated segments supported along with said emitter means from said base; and

means providing electrical connections between the first emitter means terminal and one of said lead frame segments and between the second of said terminals and the other of the lead frame segments.

6. An infrared radiation source as defined in claim 5 in which the lead frame has two independent, arcuate segments, the length of said segments being such that, when the lead frame is assembled to the base, there are gaps between the ends of said segments.

7. An infrared radiation source as defined in claim 5:

which has a mirror means for collimating infrared radiation outputted by said emitter means and focusing said radiation into a beam;

said mirror means being supported by said base and having an axis of symmetry; and

the midpoint of the emitter material means emissive layer being coincident with the axis of symmetry of the mirror means.

8. An infrared radiation source as defined in claim 7 which has means for so spacing said emitter means from said mirror means as to keep the emitter means from contacting and damaging the mirror means.

9. An infrared radiation source as defined in claim 5 in which the lead frame has terminals integral with the respective segments of the lead frame and said base has terminal receiving slots for said terminals, said slots extending from end to end of the base.

10. An infrared radiation source as defined in claim 5 which has a protective cap assembled to said base in overlying relationship to said emitter means.

11. An infrared radiation source as defined in claim 10 which:

has a mirror means for collimating infrared radiation outputted by the emitter means and for focusing the collimated radiation into a beam; and

wherein there are aligned apertures in said base and said cap through which said beam of infrared radiation can pass to the exterior of the source.

12. A transducer which comprises:

an infrared radiation source as defined in claim 5 for outputting a beam of infrared radiation;

detector means for intercepting said beam after it has passed through a sample and been attenuated by a selected gas of interest in said sample; and

means for housing said infrared radiation source and said detector means in an aligned relationship along a selected optical path.

13. The combination of an airway adapter and a transducer for outputting an electrical signal which is indicative of the concentration of a selected gas in a stream flowing through the airway adapter;

said airway adapter having a sampling passage therethrough and optical windows on opposite sides of said sampling passage and aligned along an optical path traversing the sampling passage;

said transducer having;

an infrared radiation source as defined in claim 5 for generating infrared radiation and propagating a beam of said radiation along said optical path and detector means for intercepting said beam after it has traversed said sampling passage and for outputting a signal which is indicative of the extent to which the infrared radiation is attenuated as it traverses the sampling passage and, consequentially, of the concentration of the selected gas in the stream flowing through the sampling passage; and

said airway adapter and said transducer having cooperating means for detachably fixing said transducer to said airway adapter with said infrared radiation source and said detector means on opposite sides of the airway adapter and aligned along the optical path.

14. A system for analyzing the concentration of a selected gas in a sample which may contain that gas, said system including an infrared radiation source as defined in claim 5 for emitting infrared radiation and means for forming and directing a beam of said radiation through said sample to thereby attenuate said infrared radiation to an extent proportional to the concentration of the selected gas in said sample;

and

detector means for intercepting the attenuated beam of infrared radiation and outputting a signal proportional in magnitude to the concentration of the selected gas in the sample.

15. A system as defined in claim 14 in which the detector means comprises:

first and second detectors upon which said beam of attenuated infrared radiation can impinge;

a first filter means in front of said first detector for limiting the infrared radiation reaching the first detector to infrared radiation in that part of the electromagnetic spectrum containing energy absorbable by the selected gas;

a second filter means in front of said second detector for limiting the infrared radiation reaching that detector to infrared radiation in a selected part of the electromagnetic spectrum containing energy which is not absorbable by the selected gas; and

a beam splitter for transmitting said attenuated beam of infrared radiation to one of said first and second detectors and for reflecting said beam onto the other of said first and second detectors.

16. A system as defining in claim 15 which has a driver means for applying electrical pulses of first one polarity and then the opposite polarity to said emissive layer to effect the emission of pulses of infrared radiation therefrom.

17. That method of manufacturing an infrared radiation source which includes the steps of:

providing an infrared radiation emitter which includes a substrate and a layer of an emissive, electrically resistive material on said substrate;

providing a centrally apertured, electrically conductive lead frame;

fixing said infrared radiation emitter to said lead frame with the emitter spanning the central aperture in the lead frame;

electrically connecting opposite ends of the emissive material layer of the infrared radiation source to said lead frame on opposite sides of the aperture therein;

installing the assembly of infrared radiation emitter and lead frame in a base; and

then

interrupting the continuity of said lead frame at locations on opposite sides of the lead frame and between the infrared radiation emitter-to-lead frame connections to thereby divide the lead frame into two electrically isolated segments and create a circuit in which an electrical current applied to one of said segments flows therefrom through the layer of emissive, electrically resistive material to the other of the lead frame segments.

18. A method as defined in claim 17 in which:

the lead frame is a flat member having integral terminals extending from the segments of the lead frame;

the base has terminal receiving slots opening onto the periphery thereof; and

said terminals are bent to fit into said slots.

19. A method as defined in claim 18 in which:

the lead frame is an integral ring-shaped member with breakaway tabs separating the lead frame segments; and

the lead frame is divided into electrically isolated segments as aforesaid by removing said breakaway tabs.

20. A method as defined in claim 17:

in which there are terminals at the opposite ends of and electrically connected to the emissive material layer of the infrared radiation emitter; and

the electrical connections between the emissive layer and the lead frame are made between said terminals and the segments of the lead frame and after the lead frame and emitter are installed in the base.

21. A method as defined in claim 17 which includes the step of thereafter assembling a protective cap to said base on the exposed side of the infrared radiation emitter.

22. A method as defined in claim 17 which includes the step of assembling to said base and in axial alignment with the emitter a component with a mirror means for collimating infrared radiation outputted from the emitter and for focusing said radiation into a beam.

23. A method as defined in claim 17 which includes the steps of providing on said base and in said lead frame complementary sets of locator lugs and slots so asymmetrically arrayed that the assembly of lead frame and infrared radiation emitter can not be assembled to said base in an upside down orientation.

24. That method of manufacturing an infrared radiation source which includes the steps of:

providing a base and an infrared radiation emitter which includes a substrate and a layer of an emissive, electrically resistive material on said substrate;

providing a lead frame which has two independent, arcuate segments;

installing said segments in said base at one end thereof with the segments concentrically arranged about the axial centerline of the base and with gaps between the ends of the segments;

installing the infrared radiation emitter in the base on the lead frame; and

making electrical connections between the ends of the emissive material layer of the infrared radiation emitter and the lead frame segments, thereby creating a circuit in which an electrical current applied to one of said segments flows therefrom through the layer of emissive, electrically resistive material to the other of the lead frame segments.

25. A method as defined in claim 24:

in which said base has recesses for electrical leads extending from the locus of the lead frame to the opposite end of the base; and

after said lead frame is installed in the base,

installing leads in said recesses and electrically connecting the leads to the lead frame segments.

26. A method as defined in claim 25 which includes the step of thereafter assembling to said base and in axial alignment with the emitter a component with a mirror means for collimating infrared radiation outputted from the emitter and for focusing said radiation into a beam.

27. A method as defined in claim 24:

in which there are terminals at the opposite ends of and electrically connected to the emissive material layer of the infrared radiation emitter; and

the electrical connections between the emissive material layer and the lead frame are made between said terminals and the segments of the lead frame and after the lead frame and emitter are installed in the base.

28. A method as defined in claim 24 which includes the step of assembling a protective cap to said base on the exposed side of the infrared radiation emitter.

29. A device which can be converted into an infrared radiation source, said device comprising:

emitter means having a substrate;

a layer of an electrically resistive, emissive material on said substrate; and

first and second electrical terminals on said substrate and in electrical contact with said layer of emissive material at the opposite ends thereof;

a base;

a lead frame with two electrically isolatable segments supported along with said emitter means from said base; and

means providing electrical connections between the first emitter means terminal and one of said lead frame segments and between the second of said terminals and the other of the lead frame segments.

30. A device as defined in claim 29 wherein said lead frame is an integral annular ring with removable tab means which can be removed after said leaf frame is assembled to said base to divide said lead frame into two separate segments with gaps between the ends thereof.

31. A device as defined in claim 30:

which comprises means for assembling said emitter means to said lead frame with one end of the emitter means fixed relative to the lead frame and the other end thereof free to float relative to said lead frame, said lead frame thereby serving as both a support and an assembly jig for the emitter means; and

said lead frame and said base having cooperating means which so engage as the emitter means support is assembled to the base as to keep said emitter means from being assembled to said base other than in a single selected orientation relative to the base.

32. A device as defined in claim 31 in which:

said base has a platform for supporting the lead frame, a circular wall surrounding said platform, and an asymmetric array of locator lugs protruding radially from said wall; and

said lead frame is a flat member with a circular configuration, has a diameter such that it can be seated on said platform and positioned thereon by said wall, and has in the rim thereof a set of slots complementing and positioned to receive the locator lugs of the base.

33. An infrared source which comprises:

an emitter unit comprising an electrically driven emitter means, a support for said emitter means, and a base;

said emitter means support comprising a lead frame with a rim or terminals for connecting said emitter means across and electrical power source; and

said base and said lead frame having cooperating means which keep said emitter unit from being assembled to said base in other than a single orientation relative to said base.

34. An infrared radiation source as defined in claim 33 in which:

said base has a lead frame supporting platform, a circular wall surrounding said platform, and an asymmetric array of locator lugs protruding radially from said wall; and

said lead frame is a flat member with a circular configuration, has a diameter such that it can be seated on said platform and positioned thereon by said wall, and has in the rim thereof a set of slots complementing and positioned to receive the locator lugs of the base.

35. An infrared radiation source as defined in claim 33:

which has a mirror means for collimating and focusing electromagnetic energy outputted by said emitter means; and

in which;

said base has a central bore therethrough;

said mirror means is disposed in said central bore; and

said mirror means and said base have cooperating means which locate said mirror means in said bore in optically aligned relationship with the emitter means of the emitter unit.

36. An infrared radiation source as defined in claim 35 in which the cooperating means of the base and the mirror means is an array of complementary lugs and recesses.

37. An infrared radiation source as defined in claim 35 which includes means spacing said mirror means form said emitter means and thereby keeping the emitter means and the mirror means from coming into damage-producing contact.

38. An infrared radiation source as defined in claim 33:

which includes a cap assembled to said base in overlying protective relationship to said base, said cap having;

an aperture through which infrared radiation emanating from said emitter means can be propagated and means receiving the lead frame terminals; and

said cap and said base having cooperating slots and wall segments which fix the cap relative to the base.