Regulated infrared source

• US 5,247,185 A
• Filed: 10/28/1991
• Issued: 09/21/1993
• Est. Priority Date: 10/28/1991
• Status: Expired due to Term

• Current Assignee: Dolphin Medical, Inc. (OSI Systems Incorporated)
• Original Assignee: Critikon, Inc.
• Inventors: Braig, James R., Goldberger, Daniel S., Herrera, Roger O.
• Primary Examiner(s): Berman, Jack I.
• Assistant Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US07/782,990
• Time in Patent Office: 694 Days
• Field of Search: 250/504 R, 250/495.1, 250/494.1, 250/493.1, 219/505, 219/497
• US Class Current: 250/504.00R
• CPC Class Codes: G01J 3/108 for measurement in the infrared range
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 2201/069 Supply of sources
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: H05B 3/46 heating conductor mounted on insulating base

Abstract

An infrared source which provides a miniature, highly stable and efficient source of infrared energy for use with infrared detectors and the like. The infrared source of the invention incorporates a platinum resistance temperature detector (RTD) which is integrated with the heater element to provide a means of electronic servo control of the heater temperature. The heater element and the RTD are tightly coupled thermally to provide accurate, continuous tracking and control of the heater temperature. The infrared source design provides excellent infrared energy output with less than one watt input power to the heater.

Claims

1. An infrared energy source, comprising:

a heater element which emits infrared energy when power is applied thereto;

a resistance temperature detector which is electrically isolated from but thermally coupled to said heater element so as to continuously detect the average temperature of said heater element; and

a regulator responsive to a temperature detection output of said resistance temperature detector for regulating the power applied to said heater element so as to maintain the infrared energy emitted by said heater element at a desired level.

2. An infrared energy source as in claim 1, wherein said heater element comprises a heater wire.

3. An infrared energy source as in claim 2, further comprising a ceramic rod about which said heater wire is wound near a tip thereof, said ceramic rod acting as a support for said heater wire.

4. An infrared energy source as in claim 3, wherein said ceramic rod has at least one internal bore in which said resistance temperature detector is concentrically disposed under said heater wire so as to be in close proximity with said heater wire.

5. An infrared energy source as in claim 4, wherein said heater wire and resistance temperature detector are threaded through respective internal bores of said ceramic rod from a base of said ceramic rod to said tip of said ceramic rod.

6. An infrared energy source as in claim 5, further comprising a protective glass coating about said heater wire, ceramic rod and resistance temperature detector.

7. An infrared energy source as in claim 4, wherein said resistance temperature detector is threaded through said at least one internal bore of said ceramic rod from a base of said ceramic rod to said tip of said ceramic rod and said heater wire is connected to leads external to said ceramic rod.

8. An infrared energy source as in claim 7, further comprising a protective glass coating about said heater wire, ceramic rod and resistance temperature detector.

9. An infrared energy source as in claim 3, wherein said resistance temperature detector comprises a platinum coil which is wound with said heater wire about said ceramic rod.

10. An infrared energy source as in claim 9, further comprising a protective glass coating abut said heater wire, platinum coil and ceramic rod.

11. An infrared energy source as in claim 3, further comprising a heat insulating plastic housing disposed about a base of said ceramic rod and an elliptical reflector in contact with said plastic housing and disposed with respect to said heating element so as to focus infrared energy emitted from said heating element towards a detection point.