Thermal detector modulation scheme

• US 5,620,254 A
• Filed: 03/08/1995
• Issued: 04/15/1997
• Est. Priority Date: 03/08/1995
• Status: Expired due to Fees

• Current Assignee: Business Alliance Capital Corp. (Banco Santander SA)
• Original Assignee: Servo Corporation of America
• Inventors: Rost, Martin
• Primary Examiner(s): Bennett, G. Bradley
• Application Number:
  US08/400,348
• Time in Patent Office: 769 Days
• Field of Search: 374/32, 374/121, 374/129, 374/126, 374/128, 374/133, 374/163, 374/183, 374/130, 250/349, 250/338.1
• US Class Current: 374/129
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices

Abstract

The apparatus is a thermal detector which uses an active detector element and a compensator detector element, particularly in a voltage divider configuration. Radiation from a scene of interest impinges on the active detector element and radiation from an electronically modulated light source impinges on the compensator detector element.

Claims

1. A thermal detector including:

an active detector element which detects radiation from a scene of interest;

a modulated light source;

a compensator detector element which detects radiation from said modulated light source; and

a modulated output which is responsive to an output of said active detector element as compensated by an output of said compensator detector element.

2. The thermal detector of claim 1 wherein said modulated light source is modulated electronically.

3. The thermal detector of claim 2 wherein said active detector element and said compensator detector element change resistance in response to the intensity of radiation impinging thereon.

4. The thermal detector of claim 3 wherein said active detector element and said compensator detector element are thermistor bolometers particularly responsive to infrared radiation.

5. The thermal detector of claim 4 wherein said active detector element and said compensator detector element are configured as resistors in a voltage divider.

6. The thermal detector of claim 5 wherein a voltage of a given magnitude and a given polarity is applied to a first end of said active detector element;

a voltage of said given magnitude and a polarity opposite said given polarity is applied to a first end of said compensator detector element;

a second end of said active detector element and a second end of said compensator detector element are joined at a common node; and

wherein a voltage signal from the thermal detector is measured from said common node.

7. The thermal detector of claim 6 wherein said active detector element and said compensator detector element are configured on a common substrate.