R. Andrew Wood

Uncooled thermal imaging with monolithic silicon focal planes

This article summarizes the characteristics of Honeywells two-dimensional (2-D) arrays of micromachined microbolometers, discusses practical methods of operating these arrays in high-sensitivity room-temperature infrared (IR) imaging systems, and describes recent performance measurements.

IR SnapShot camera

The IR SnapShotTM camera is an uncooled, handheld imaging radiometer designed primarily for the predictive and preventive maintenance market. It employs a linear thermoelectric array to scan the focal plane of a germanium lens, thereby producing a 120 by 120 pixel image with an instantaneous field of view (IFOV) of 2.8 by 2.8 mrad, an overall field of view (FOV) of 20 degrees by 20 degrees, a frame time of 1.44 sec, a noise equivalent temperature difference (NETD) no greater than 0.2 C, and a radiometrically calibrated dynamic range up to 500 C.

IR detector system for the GERB instrument

The Geostationary Earth radiation Budget (GERB) instrument will play an important role in Earth Observation Science, when it is launched on ESAs Meteosat Second Generation (MSG) satellite in 2000. The purpose of the instrument is to measure the reflected and emitted radiation of the Earth over at least a five year period, to an accuracy better than 1% within a 15 minute observation period. These scientific requirements have resulted in a detector system comprising several technological advances. The detector chosen for this instrument is a 256 pixel linear array of thermoelectric (TE) elements operating at room temperature. Based on an existing commercial design, the detector has pushed micromachined thermoelectric arrays to its limits to achieve the noise requirements. The spectral requirements of the instrument to give a flat spectral response over the 0.32 - 30 micrometer range has necessitated the blacking of the TE array. Blacking such small area arrays is a novel application and presented several problems during the course of the development. The signal conditioning electronics, consisting of 4 Application Specific Integrated Circuits, performs front end analogue signal processing, A/D conversion and multiplexing. The design of the detector system is presented in this paper, with the packaging, signal processing and blacking described in some detail.

IR detectors for the GERB instrument on MSG

The Geostationary Earth Radiation Budget (GERB) instrument is to be flown on ESAs Meteosat Second Generation (MSG) satellite in 2000. The purpose of the instrument is to measure accurately the daily cycle of the reflected and emitted radiation of the Earth over at least a five year period. The measurements will be made from geostationary orbit and will complement those planned from instruments in low Earth polar orbits. The data from GERB will provide the first consistent measurements of the hour-by-hour variation of clouds and simultaneous measurements of the radiation balance, and will allow climate models to be further developed and validated. The instrument will accumulate images of the Earth disc every 15 minutes in wavebands of 0.32 - 4.0 pm and 0.32 - 30 im with a nadir resolution of 50 km. The detector for this instrument consists of a 256 pixel linear array of thermoelectric (TE) elements. The TB array operates at room temperature and is blacked to give a flat spectral response over the 0.32 - 30 im band. The detector hybrid consists of the 256pixel detector plus 4 Application Specific Integrated Circuits (ASICs), comprising 64 channels each, which perform front end analogue signal processing, A/D conversion and multiplexing. As the MSG platform is spin-stabilised, the Earth image is stabilised on the detector using a de-spin mirror and is only present on the detector for 40 ms. Integration of the signal over the 40 ms and taken over a 15 minute observation period enables the radiance in both long and short wavebands to be measured to an accuracy better than 1%. The detector concept is described and test results of a prototype system are presented. Keywords: JR detectors, thermoelectric, gold black, EOS