Bolometer autocalibration

• US 6,064,066 A
• Filed: 07/19/1996
• Issued: 05/16/2000
• Est. Priority Date: 07/21/1995
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Bevan, Malcolm J., McCardel, William L., Wadsworth, Mark V., Westphal, Glenn H.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Israel, Andrew
• Application Number:
  US08/684,122
• Time in Patent Office: 1,397 Days
• Field of Search: 250/345, 250/343, 250/339.12, 250/252.1 A
• US Class Current: 250/345
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices

Abstract

A sensor (1400) with radiation detectors (1421-1422) with two or more bolometer or photoconductor elements and bias polarity switching of one element to emulate mechanical chopping of input radiation. This electronic chopping permits higher chopping frequencies than mechanical chopping for bolometers because the scene settling time does not limit electronic chopping. The detectors may be within a single vacuum integrated circuit package with separate narrow passband filters for chemical spectral analysis.

Claims

1. A gas sensor, comprising:

(a) a radiation source;

(b) a first radiation detector spaced from said source, said first radiation detector detecting radiation of a first wavelength from said radiation source, said first wavelength corresponding to an absorption band of a gas to be sensed;

(c) a second radiation detector spaced from said source, said second radiation detector detecting radiation of a second wavelength from said radiation source, said second wavelength a reference wavelength;

(d) a first differencer with inputs from said first and second detectors, an output of said first differencer being the difference of the outputs of said first and second detectors, whereby the gas absorption is determined;

(e) a second differencer with inputs from said second detector and a reference, an output of said second differencer being the difference of the output of said second detector and said reference, whereby change in radiation from said source is determined; and

(f) a combiner with inputs being the outputs of the first and second differencers, an output of said combiner being the product of the outputs of the first and second differencers, whereby the gas absorption determination is adjusted for source radiation intensity.

2. The sensor of claim 1, wherein:

(a) said first and second differencers are difference amplifiers; and

(b) said combiner is an automatic gain control amplifier.

3. The sensor of claim 1, wherein:

(a) said first and second radiation detectors include bolometers and bandpass filters; and

(b) said wavelengths correspond to infrared radiation.

4. A sensor, comprising:

(a) a radiation source;

(b) a first radiation detector, said first radiation detector detecting radiation of a first wavelength from said radiation source;

(c) a second radiation detector, said second radiation detector detecting radiation of a second wavelength from said radiation source;

(d) a first differencer with inputs from said first and second detectors, an output of said first differencer being the difference of the outputs of said first and second detectors;

(e) a second differencer with inputs from said second detector and a reference, an output of said second differencer being the difference of the output of said second detector and said reference; and

(f) a controller with inputs being the outputs of the first and second differencers, an output of said controller being the product of the outputs of the first and second differencers.