Zinc sulphide thermal imaging lenses

Paul Boughton

Demand for long wave infrared (LWIR) thermal cameras is growing and one of the most expensive parts of the camera is the current germanium lens. To address this feature, and to supply more affordable lenses, developments have been made with a sintered zinc sulphide (ZnS) lens.

This is not manufactured by the traditional method of vapour deposition (CVD), which is expensive and slow, but a precise sintering and moulding forming process utilising powdered material in a heated press.This process provides a perfect lens shape every time.

Material, time and labour are reduced and the resulting lenses are all around the F# 1.0~1.1 aperture providing high quality thermal imaging. The ZnS lens has characteristics such as high-purity transmission from 8 to 12μm in wavelength, optical surface roughness of less than 0.020 μm on average and profile errors within 3μm.

In addition, a ZnS lens of this type has remarkable modulation transfer function (MTF) performance to make images clearer in detail. These are threaded lens with the same mount which allows swapping out of one lens for another and the lenses  are Athermal ensuring the stability of the picture over a wide temperature range.-40°C to +80°C

These lenses are now available in 8.6mm. 13mm. 18.8mm and 35mm for both 320 and 640 pixel imagers with more versions to follow.

For more information, visit www.premierelect.co.uk



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