Thermal imager
AssigneeGEC-Marconi Limited
InventorBrian F. Smith
Life of this patent
Estimating the term…
Abstract
A thermal imager including a cryogenically cooled detector element array and a scanning element has an optical system with a field of view limited by a field stop (2). A retroreflective region (6) is provided on part of the field stop to act as a temperature reference by allowing the detector array to "look at" itself. A second, different temperature reference (5) is provided on another part of the field stop and the two references are used to equalize and adjust the output characteristics of the elements in the detector array.
Claims14
A thermal imager including:
- a thermal sensor and a first temperature reference means including retro-reflective means for providing a retro-reflected image of the sensor for use as a first temperature reference, a second temperature reference means, said second temperature reference means including means for providing a second temperature reference at a different temperature from that of the retro-reflected image, an optical system for admitting electromagnetic radiation to the thermal sensor, the optical system including a field stop adapted to limit the field of view of the scene viewed by the sensor, and wherein said first and second temperature reference means are situated on portions of the field stop;
- scanning means adapted to scan over the field of view of the scene and, when required, also over each temperature reference means;
- and electrical means for processing an output of the thermal sensor.
A thermal imager as claimed in claim 4 wherein the imager is a scanning type imager including one or more scanning elements adapted to scan over a field of view greater than that of the scene to be imaged and wherein the retro-reflective means is situated outside the field of view of the scene but within the possible field of view which may be scanned by scanning elements of the imager.
A thermal imager comprising:
- a thermal sensor;
- an optical system for admitting electro-magnetic radiation to the thermal sensor,
- a field stop positioned to limit a field of view of a scene viewed by said thermal sensor,
- a first temperature reference region including retro-reflective means for providing a retro-reflected image of the sensor as a first temperature reference,
- a second temperature reference region including means for providing a second temperature reference at a known temperature different from the temperature of the retro-reflected image;
- scanning means arranged to scan over the field of view of the scene and, when required, also over both temperature reference regions so as to provide two different temperature references;
- and
- electrical means for processing an output of the thermal sensor.
Dependencies are inferred from the claim text.