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Title: Thermograph absolute temperature referencing technique
Claims: I claim: 1. In a thermograph instrument that is characterized by a reference temperature target adjacent an optical field to be viewed, means for scanning and detecting an infrared energy component of the optical field in two dimensions with a portion of the reference target periodically being scanned and detected thereby, electronic video processing circuits receiving a time varying output of said detector means that is proportional to the infrared intensity of the optical field, and means synchronized with said scanning and detecting means for referencing a portion of said video processing circuits to a reference potential simultaneously with said reference target being scanned and detected, the improvement comprising means independent of said scanning and detecting means and responsive to the absolute temperature of said reference target for developing said reference potential proportional to the target absolute temperature. 2. The improved thermograph instrument of claim 1 wherein said improvement additionally comprises means including a manual adjustment for setting a biasing voltage component to said reference potential, whereby said referenced potential is set both by the temperature of the target and the manual adjustment. 3. The improved thermograph instrument of claim 1 wherein the video signal level appearing from the detecting means at the periodically referenced portion of the video circuits changes the same amount per unit temperature change of the reference target when viewed by the scanning and detecting means as does the reference potential. 4. In a thermograph instrument that is characterized by a reference temperature target adjacent an optical field to be viewed, means for scanning and detecting an infrared energy component of an optical field in two dimensions with a portion of the reference target periodically being scanned and detected thereby, electronic video processing circuits receiving a time varying output of said detector means that is proportional to the infrared intensity of the optical field, a pre-amplifier receiving the output of said detecting means and forming an amplified version thereof at its output, a capacitor coupled at one side thereof to the output of said pre-amplifier, and means synchronized with said scanning and detecting means for referencing a portion of said video processing circuits to a reference potential simultaneously with said reference target being scanned and detected, said reference potential connectable to an opposite side of said coupling capacitor at times when said reference temperature target is being imaged onto said detector, the improvement comprising means including a thermistor physically attached to said reference temperature target for developing said reference potential that is proportional to the temperature of said reference target. 5. In a thermograph instrument that is characterized by a reference temperature target adjacent an optical field to be viewed, means for scanning and detecting an infrared energy component of an optical field in two dimensions with a portion of the reference target periodically being scanned and detected thereby, electronic video processing circuits receiving a time varying output of said detector means that is proportional to the infrared intensity of the optical field, means synchronized with said scanning and detecting means for referencing a portion of said video processing circuits to a reference potential simultaneously with said reference target being scanned and detected, the improvement comprising means including a thermistor physically attached to said reference target and electrically connected to develop a signal non-linearly proportional in level to the target temperature, and means receiving said thermistor signal for compensating for the thermistor nonlinearity to form an output signal substantially linearly proportional to the temperature of said reference target, said output signal thereby setting said reference potential. 6. An apparatus for electronically clamping an infrared sensitive video system, comprising: an infrared sensitive detector, a reference temperature target, means for alternately scanning an object and said target in a two dimensional line raster pattern with said detector in order to develop a time varying electronic signal thereof, means independent of said detector for measuring the absolute temperature of said reference target and producing a voltage proportional thereto, and means receiving both said time varying electronic signal and the reference target temperature voltage for electronically summing them, whereby a resulting summation voltage signal contains object information from detector that is unaffected by temperature variation of the reference target. 7. The apparatus of claim 6 wherein said reference target temperature measuring means includes a temperature transducer physically attached to said reference target. 8. The apparatus of claim 6 wherein all of said detector, target, scanning means, measuring means and summing means are contained within a single instrument case. 9. The apparatus of claim 6 wherein said reference target temperature measuring and voltage proportional means includes means compensating an electrical signal developed by the target temperature measuring means in a manner that said voltage proportional to the target temperature varies at said summing means at the same rate per unit change in target temperature as does said time varying electronic signal from said detector at said summing means. Other info: Inventors: Hunt, Robert P. (Menlo Park, CA, US) Application Number: 447960 Filing Date: 1974-03-04 Publication_date: 1976-01-27 Assignee: Spectrotherm Corporation (Santa Clara, CA) Primary Class(es): 348/168 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Murray, Richard Assistant Examiner: Attorney: Limbach, Limbach & Sutton |
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