Compact thermal camera

• US 5,675,149 A
• Filed: 08/08/1996
• Issued: 10/07/1997
• Est. Priority Date: 09/30/1994
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Rezachek, Thomas Michael, Wood, Roland Andrew, Kubisiak, David
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US08/700,586
• Time in Patent Office: 425 Days
• Field of Search: 250/330, 250/334, 250/332
• US Class Current: 250/332
• CPC Class Codes: H04N 23/23 from thermal infrared radiation
• CPC Class Codes: H04N 23/58 Means for changing the camera field of view without moving the camera body, e.g. nutating or panning of optics or image sensors
• CPC Class Codes: H04N 3/09 for electromagnetic radiation in the invisible region, e.g. infrared
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A low-cost portable handheld still-frame thermal camera for capture of calibrated digital thermographic infrared images having a lens assembly, a slideable linear array of uncooled 8-12 um thermal IR sensors, a slider actuation mechanism, and associated digital processing capability for calibrating, displaying, and storing images captured by the camera. The sensors are preferably thermoelectric sensors. The lens passes infrared radiation, the array is contained in an evacuated chamber, and operates at room temperature. The thermographic images may be displayed immediately or remotely or may be printed by conventional techniques.

Claims

1. A self-contained infrared camera including a camera housing for enclosing and supporting all components for capturing and displaying a two dimensional infrared image of a scene which emits thermal radiation, the self-contained infrared camera comprising:

a focusing lens rigidly attached to a camera housing for transmitting infrared radiation therethrough and focusing a two dimensional infrared image of said scene at an image focal plane perpendicular to an optical axis of said focusing lens;

thermoelectric sensor array assembly means including a plurality of linearly arranged thermoelectric sensors, S_m, aligned with a sensor reference axis passing through said plurality of sensors, each of said plurality of thermoelectric sensors being capable of providing raw infrared sensor information, R_m, in response to sensed infrared radiation impinging thereon, and where M is the number of said plurality of linearly arranged thermoelectric sensors and where "m" designates the m^th position along said sensor reference axis;

support means for rigidly supporting said linear thermoelectric sensor array assembly means;

linear scanning means, responsive to a command signal, for controllably moving said support means to discrete scan positions, P_n, along a reference scan axis perpendicular to said optical axis, said support means coupled to and arranged relative to said scanning means such that said sensor reference axis is substantially perpendicular to said reference scan axis and said optical axis, where "n" represents the n^th position along said reference scan axis, and where said linear scanning means is capable of moving said plurality of thermoelectric sensors in alignment with said focal plane so as to be responsive to said infrared image;

storage means for storing unique thermoelectric sensor calibration information, C_mn, for each one of said sensors, S_m, and corresponding discrete scan positions, P_n, where said unique sensor calibration information is related to unique raw infrared sensor information of each of said plurality of said thermoelectric sensors at said discrete scan positions in response to known infrared radiation passing through said focusing lens and impinging thereon;

signal processing means for,

providing said command signal such that said scanning means controllably moves said support means to successive ones of said discrete scan positions, P_n, for a selected measurement time, such that at least some of said plurality of sensors, S_m, pass through the field of view of said infrared image in the direction of said scan axis, and provide said raw infrared sensor information for each discrete scan position, R_mn, in response to any infrared radiation impinging thereon, where R_mn represents said raw infrared sensor information for the m^th thermoelectric sensor at the n^th discrete scan position, and

deriving corrected infrared sensor information, Q_mn, for each of said plurality of thermoelectric sensors, S_m, at each of said discrete scan positions, P_n, as a function of corresponding ones of said raw infrared sensor information, R_mn, and said thermoelectric sensor calibration information, C_mn, and said corrected infrared sensor information, Q_mn, represents corrected raw infrared information associated with the m^th thermoelectric sensor at the n^th discrete scan position; and

display means rigidly attached to said camera body for displaying an 2 dimensional visual image, M×

N, representation of said corrected infrared sensor information, Q_mn, so as to provide a visual representation of said infrared image, where said visual image has one axis which represents successive discrete scan positions, and another display axis which represents said sensor reference axis.

2. The self-contained infrared camera of claim 1 further comprising:

reference plate means having known infrared emissivity and temperature for emanating known infrared radiation; and

means for subjecting said plurality of said sensors to said known infrared radiation emanating from said reference plate;

means for determining discrete sensor offset information, X_m, associated with each of said plurality of thermoelectric sensors, S_m, in response to raw infrared sensor information resulting from said known infrared radiation emanating from said reference plate; and

wherein said corrected infrared sensor information, Q_mn, for each of said plurality of thermoelectric sensors, S_m, at each of said discrete scan positions, P_n, is derived as a function of corresponding ones of said raw infrared sensor information, R_mn, said thermoelectric sensor calibration information, C_mn, and said discrete sensor offset information, X_m.

3. The self-contained infrared camera of claim 2 where in said signal processing means is capable of commanding said linear scanning means to position said support means to a position such that said plurality of said thermoelectric sensors receives infrared radiation directly from said reference plate.

4. The self-contained infrared camera of claim 1 where in said calibration information is in the form of calibration constants whereby said raw infrared sensor information from each of said thermoelectric sensors at a discrete scan position in response to infrared image of a scene is corrected to derive said corrected infrared sensor information, Q_mn.

5. The self-contained infrared camera of claim 1 wherein,

signal processing means provides said command signal such that said scanning means controllably moves said support means to a discrete scan positions, P_o such that said sensor reference axis substantially intersects said optical axis thereby centrally placing said plurality of thermoelectric sensors centrally in the field of view of said infrared image;

said signal processing means further including means for,

sampling raw infrared sensor information, R_mt, for each of said plurality of thermoelectric sensors, S_m for discrete sample times, t_s, in response to any infrared radiation impinging thereon, and

deriving corrected infrared sensor information, Q_mt, for each of said plurality of thermoelectric sensors, S_m, as a function of corresponding ones of said raw infrared sensor information, R_mt, and said thermoelectric sensor calibration information, C_mO, and

where said display means display means provides a visual representation of an object passing through the field of view of said focusing lens, where said visual image has one axis which represents successive discrete sample times, t_s, and another display axis represents said sensor reference axis.

6. The camera of claim 1 wherein said selected measurement time is the response time of said thermoelectric sensor.

7. A self-contained infrared camera including a camera housing for enclosing and supporting all components for capturing and displaying a two dimensional infrared image of a moving object which emits thermal radiation, the self-contained infrared camera comprising:

a focusing lens rigidly attached to a camera housing for transmitting infrared radiation therethrough and focusing a two dimensional infrared image of an object in the field of view of said focusing lens at an image focal plane perpendicular to an optical axis of said focusing lens;

thermoelectric sensor array assembly means including a plurality of linearly arranged thermoelectric sensors, S_m, aligned with a sensor reference axis passing through said plurality of sensors, each of said plurality of thermoelectric sensors being capable of providing raw infrared sensor information, R_m, in response to sensed infrared radiation impinging thereon, and where M is the number of said plurality of linearly arranged thermoelectric sensors and where "m" designates the m^th position along said sensor reference axis;

support means for rigidly supporting said linear thermoelectric sensor array assembly means such that said sensor reference axis is perpendicular to and substantially intersects said optical axis;

storage means for storing unique thermoelectric sensor calibration information, C_m, for each one of said sensors, S_m, where said unique sensor calibration information is related to unique raw infrared sensor information of each of said plurality of said thermoelectric sensors in response to known infrared radiation passing through said focusing lens and impinging thereon;

signal processing means for,

sampling raw infrared sensor information, R_mt, for each of said plurality of thermoelectric sensors, S_m, for discrete sample times, t_s, in response to any infrared radiation impinging thereon, and

deriving corrected infrared sensor information, Q_mt, for each of said plurality of thermoelectric sensors, S_m, as a function of corresponding ones of said raw infrared sensor information, R_mt, and said thermoelectric sensor calibration information, C_m ;

display means rigidly attached to said camera body for displaying a 2 dimensional visual image representation of said corrected infrared sensor information, Q_mt, associated with each of said plurality of thermoelectric sensors, S_m, so as to provide a visual representation of said object passing through the field of view of said focusing lens, where said visual image has one axis which represents successive discrete sample times, t_s and another display axis which represents said sensor reference axis.

8. The self-contained infrared camera of claim 7 further comprising:

reference plate means having known infrared emissivity and temperature for providing known infrared radiation; and

means for subjecting said plurality of said sensors to said known infrared radiation emanating from said reference plate;

means for determining discrete sensor offset information, X_m, associated with each of said plurality of thermoelectric sensors, S_m, in response to raw infrared sensor information resulting from said known infrared radiation emanating from said reference plate; and

wherein said corrected infrared sensor information, Q_mt, for each of said plurality of thermoelectric sensors, S_m, is derived as a function of corresponding ones of said raw infrared sensor information, R_mt, said thermoelectric sensor calibration information, C_m and said discrete sensor offset information, X_m.

9. A infrared camera including a camera housing for enclosing and supporting components for capturing a two dimensional infrared image of a scene which emits thermal radiation, the infrared camera comprising:

a focusing lens rigidly attached to a camera housing for transmitting infrared radiation therethrough and focusing a two dimensional infrared image of said scene at an image focal plane perpendicular to an optical axis of said focusing lens;

thermoelectric sensor array assembly means including a plurality of linearly arranged thermoelectric sensors, S_m, aligned with a sensor reference axis passing through said plurality of sensors, each of said plurality of thermoelectric sensors being capable of providing raw infrared sensor information, R_m, in response to sensed infrared radiation impinging thereon, and where M is the number of said plurality of linearly arranged thermoelectric sensors and where "m" designates the m^th position along said sensor reference axis;

support means for rigidly supporting said linear thermoelectric sensor array assembly means;

linear scanning means, responsive to a command signal, for controllably moving said support means to discrete scan positions, P_n, along a reference scan axis perpendicular to said optical axis, said support means coupled to and arranged relative to said scanning means such that said sensor reference axis is substantially perpendicular to said reference scan axis and said optical axis, where "n" represents n^th position along said reference scan axis, and where said linear scanning means is capable of moving said plurality of thermoelectric sensors in alignment with said focal plane so as to be responsive to said infrared image;

storage means for storing unique thermoelectric sensor calibration information, C_mn, for each one of said sensors, S_m, and corresponding discrete scan positions, P_n, where said unique sensor calibration information is related to unique raw infrared sensor information of each of said plurality of said thermoelectric sensors at said discrete scan positions in response to known infrared radiation passing through said focusing lens and impinging thereon; and

signal processing means for,

providing said command signal such that said scanning means controllably moves said support means to successive ones of said discrete scan positions, P_n, for a selected measurement time, such that at least some of said plurality of sensors, S_m, pass through the field of view of said infrared image in the direction of said scan axis, and provide said raw infrared sensor information for each discrete scan position, R_mn, in response to any infrared radiation impinging thereon, where R_mn represents said raw infrared sensor information for the m^th thermoelectric sensor at the n^th discrete scan position, and

deriving corrected infrared sensor information, Q_mn, for each of said plurality of thermoelectric sensors, S_m, at each of said discrete scan positions, P_n, as a function of corresponding ones of said raw infrared sensor information, R_mn, and said thermoelectric sensor calibration information, C_mn, and said corrected infrared sensor information, Q_mn, represents corrected raw infrared information associated with the m^th thermoelectric sensor at the n^th discrete scan position.

10. The infrared camera of claim 9 further comprising:

reference plate means having known infrared emissivity and temperature for emanating known infrared radiation; and

means for subjecting said plurality of said sensors to said known infrared radiation emanating from said reference plate;

means for determining discrete sensor offset information, X_m, associated with each of said plurality of thermoelectric sensors, S_m, in response to raw infrared sensor information resulting from said known infrared radiation emanating from said reference plate; and

wherein said corrected infrared sensor information, Q_mn, for each of said plurality of thermoelectric sensors, S_m, at each of said discrete scan positions, P_n, is derived as a function of corresponding ones of said raw infrared sensor information, R_mn, said thermoelectric sensor calibration information, C_mn, and said discrete sensor offset information, X_m.

11. The infrared camera of claim 10 where in said signal processing means is capable of commanding said linear scanning means to slidably position said support means to a position such that said plurality of said thermoelectric sensors receives radiation directly and only from said reference plate.

12. The infrared camera of claim 9 where in said calibration information is in the form of calibration constants whereby said raw infrared sensor information from each of said thermoelectric sensors at a discrete scan position in response to infrared image of a scene is corrected to derive said corrected infrared sensor information, Q_mn.

13. The infrared camera of claim 9 wherein,

signal processing means provides said command signal such that said scanning means controllably moves said support means to a discrete scan positions, P_O such that said sensor reference axis substantially intersects said optical thereby contrally placing said plurality of thermoelectric sensors centrally in the field of view of said infrared image;

and

said signal processing means further including means for,

sampling raw infrared sensor information, R_mt, for each of said plurality of thermoelectric sensors, S_m, for discrete sample times, t_s, in response to any infrared radiation impinging thereon, and

deriving corrected infrared sensor information, Q_mt, for each of said plurality of thermoelectric sensors, S_m, as a function of corresponding ones of said raw infrared sensor information, R_mt, and said thermoelectric sensor calibration information, C_mO.

14. The camera of claim 9 wherein said selected measurement time is the response time of said thermoelectric sensor.

15. An infrared camera including a camera housing for enclosing and supporting components for capturing a two dimensional infrared image of a scene which emits thermal radiation, the infrared camera comprising:

a focusing lens rigidly attached to a camera housing for transmitting infrared radiation therethrough and focusing a two dimensional infrared image of said scene at an image focal plane perpendicular to an optical axis of said focusing lens;

thermoelectric sensor array assembly means including a plurality of linearly arranged thermoelectric sensors, S_m, aligned with a sensor reference axis passing through said plurality of sensors, each of said plurality of thermoelectric sensors being capable of providing raw infrared sensor information, R_m, in response to sensed infrared radiation impinging thereon, and where M is the number of said plurality of linearly arranged thermoelectric sensors and where "m" designates the m^th position along said sensor reference axis;

support means for rigidly supporting said linear thermoelectric sensor array assembly means;

linear scanning means, responsive to a command signal, for centrollably moving said support means to discrete scan positions, P_n, along a reference scan axis perpendicular to said optical axis, said support means coupled to and arranged relative to said scanning means such that said sensor reference axis is substantially perpendicular to said reference scan axis and said optical axis, where "n" represents the n^th position along said reference scan axis, and where said linear scanning means is capable of moving said plurality of thermoelectric sensors in aligmnent with said focal plane so as to be responsive to said infrared image;

storage means for storing unique thermoelectric sensor calibration information, C_m, for each one of said sensors, S_m, where said unique sensor calibration information is related to unique raw infrared sensor information of each of said plurality of said thermoelectric sensors in response to known infrared radiation passing through said focusing lens and impinging thereon;

signal processing means for,

providing said command signal such that said scanning means controllably moves said support means to successive ones of said discrete scan positions, P_n, for a selected measurement time, such that at least some of said plurality of sensors, S_m, pass through the field of view of said infrared image in the direction of said scan axis, and provide said raw infrared sensor information for each discrete scan position, R_mn, in response to any infrared radiation impinging thereon, where R_mn represents said raw infrared sensor information for the m^th thermoelectric sensor at the n^th discrete scan position, and

deriving corrected infrared sensor information, Q_mn, for each of said plurality of thermoelectric sensors, S_m, at each of said discrete scan positions, P_n, as a function of corresponding ones of said raw infrared sensor information, R_mn, and said thermoelectric sensor calibration information, C_m, and said corrected infrared sensor information, Q_mn, represents corrected raw infrared information associated with the m^th thermoelectric sensor at the n^th discrete scan position; and

display means rigidly attached to said camera body for displaying an 2 dimensional visual image, M×

N, representation of said corrected infrared sensor information, Q_mn, associated with each of said plurality of thermoelectric sensors, S_m, at each of said discrete scan positions, P_n, so as to provide a visual representation of said infrared image, where said visual image has one axis which represents successive discrete scan positions, and another display axis which represents said sensor reference axis.

16. The camera of claim 15 wherein said selected measurement time is the response time of said thermoelectric sensor.