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How FPA Imagers Differ

Most modern thermal imagers utilize a Focal Plane Array (FPA) detector. Although the term FPA is widely used, it is frequently misunderstood. Since detector type can affect imager performance it is imperative to understand the differences among FPA detectors.

The term Focal Plane Array is a non-standard industry term which applies to modern thermal imagers that utilize a detector chip with multiple picture elements configured in a flat, single-plane array. Each pixel of an FPA is an independent sensor capable of detecting infrared energy. When arranged in an integrated array, these pixels form a sensor capable of producing relatively high resolution images compared to older, single or multi-element scanned detectors.

At present, there are two distinct types of FPA detectors:

• Cooled FPA
• Microbolometers (Uncooled FPA)

Cooled FPA imagers are short wave only, contain a Stirling cycle cooler and require approximately 5-7 minutes of cool-down time after initially turning on the unit. Cooled FPAs were initially imtroduced in the mid 1990’s and revolutionized thermography with their small size and high resolution imagery. They have been largely replaced by market demand for uncooled microbolometer imagers.

Uncooled FPA imagers or microbolometers are long wave only, do not contain a cryogenic cooling system and typically require less than one minute to produce an image after initially turning on the unit. Uncooled FPAs were first introduced in the late 1990’s and have seen many improvements over time. Nearly every thermal imager currently being offered for PPM and PdM applications utilizes a microbolometer detector.