Infrared or thermal imaging systems typically use a plurality of thermal sensors to detect infrared radiation and produce an image capable of being visualized by the human eye. Thermal imaging systems typically detect thermal radiance differences between various objects in a scene and display these differences in thermal radiance as a visual image of the scene.
The basic components of a thermal imaging system generally include optics for collecting and focusing infrared radiation from a scene, an infrared detector having a plurality of thermal sensors for converting infrared radiation to an electrical signal, and electronics for amplifying and processing the electrical signal into a visual display or for storage in an appropriate medium. A chopper is often included in a thermal imaging system to produce a constant background radiance which provides a reference signal. The electronic processing portion of the thermal imagining system will subtract the reference signal from the total radiance signal to produce a signal with minimum background bias.
Thermal imaging systems may use a variety of infrared detectors which are sometimes classified into two main categories as cooled and uncooled. Uncooled detectors typically include thermal sensors which generate a change in voltage due to a change in temperature resulting from incident infrared radiation striking the thermal sensor. Cooled detectors typically include thermal sensors which generate a change in voltage due to a photoelectron interaction within the material used to form the thermal sensor. This latter effect is sometimes called the internal photoelectric effect.
A thermal detector having thermal sensors which generate a change in voltage due to a change in temperature resulting from incident infrared radiation striking the thermal sensors, generally includes thermal isolation between the thermal sensors and the associated integrated circuit substrate or signal processing portion of the thermal detector. Without effective thermal isolation, the thermal sensors will not respond satisfactorily to incident infrared radiation. Typically, such thermal sensors also require one or more electrical contacts to provide a signal to the associated integrated circuit substrate in response to incident infrared radiation. These electrical contacts often compromise or reduce the effectiveness of the thermal isolation between the respective thermal sensors and the associated integrated circuit substrate.