Thermal imaging system with integrated thermal chopper

A thermal imaging system for producing an image of a scene, comprising:

• optics for focusing radiation emitted by the scene on a focal plane array;
• the focal plane array, including a plurality of thermal sensors mounted on a substrate, for generating a biased signal representing the total radiance from the scene and for generating a reference signal by thermally shunting the thermal sensors to the substrate;
• electronics for receiving the biased signal and the reference signal and for subtracting the reference signal from the biased signal to obtain an unbiased signal representing radiance differences emitted by objects in the scene;
• and
• a display for receiving the unbiased signal and for displaying an image generated in response to the unbiased signal.

A focal plane array including a plurality of thermal sensors mounted on a substrate to provide a signal representative of the amount of thermal radiation incident to the focal plane array, each thermal sensor comprising:

• a common plate;
• a pair of thermally sensitive pixel elements with each pixel element electrically coupled on one side with the common plate and on the other side with a respective electrode;
• each electrode coupled to a respective contact pad disposed on the substrate for forming a signal path between the contact pads through the common plate, the pixel elements, and the electrodes;
• and
• each electrode comprising a flexible lead that allows the thermal sensor to deflect and contact the substrate for providing a reference signal representative of the temperature of the substrate.

A method for producing an image of a scene using a thermal imaging system with a plurality of thermal sensors mounted on a substrate, comprising the steps of:

• thermally shunting the thermal sensors to the substrate to establish a reference signal representative of the temperature of the substrate;
• detecting the thermal radiation from the scene to form a biased signal representing the total radiance of the scene;
• subtracting the reference signal from the biased signal to obtain an unbiased signal representing radiance differences emitted by objects in the scene;
• and
• displaying an image in response to the unbiased signal.