OEM thermal imaging camera integration FAQs

The MicroCAM supports GigE, Camera Link, BT656, USB and our own proprietary Multiplexed format. BT656 is a common standard although Thermoteknix use a 'square pixel version' which is a common derivative.

BT656 supports colour although Thermoteknix only produce a monochrome output from the MicroCAM3. The image content is virtually identical to that seen on the analogue video output, in other words text overlays and image zoom are both supported.

The Multiplexed digital output is a lower level, proprietary digital format, (documented by Thermoteknix). Each pixel is conveyed as 16 bits (in two multiplexed bytes of 8 bits). This allows Three types of imagery to be selected:

• 8 bit Processed. 8 bit video image (similar to analogue but WITHOUT overlays/scaling)
• 14 bit Corrected. 14 bit processed image with full dynamic range of the sensor, NUC and Bad Pixel corrected.
• 14 bit Raw. 14 bit output direct from the sensor no processing applied.

The MicroCAM is designed as a board stack and the third board is known as the accessory board. For different types of digital output it is necessary to select different accessory boards. Your local sales contact will be able to provide more details including dimensions and weight.

'Uncooled' means the sensor operates at 'ambient' temperatures and no cooling technology is required.

Cooled thermal imagers use a different sensor material technology that has to be operated at cryogenic temperatures. Typically these cameras are more expensive, heavy and power hungry but have superior performance and can be used with higher F# number optics for long ranges.

Typically no maintenance is required for uncooled thermal cameras.

Microbolometers are the name given to the mainstream current technology for uncooled cameras. The sensors are arrays of micromachined thermal collectors (analogous to miniature thermopiles).

Thermal detectors have significant amounts of non-uniformity of response between array elements. This can be corrected by imposing a shutter over the array to determine (and then subtract away) the non-uniformity. Shutterless cameras use other techniques to eliminate this non uniformity (without imposing a shutter) such as calibration in the factory and various scene based algorithms.

The obvious difference is the presence and operation of the shutter! As well as the obvious issues of size and power with a shutter, the image is interrupted (stopped) periodically when the shutter is operated. For some applications this is not acceptable i.e. cannot have the possibility of the mage freezing when using a weapon sight!

Infrared optics use different materials and designs for lenses. Using these materials creates optics where the focus changing significantly with temperature. Athermalised lenses use additional techniques to combat this so that a lens stays 'in focus' (i.e. does not need refocusing) over a wide temperature range.

Infrared optical elements have to be coated to optimise the transmission of the infrared radiation. The highest efficiency coatings use exotic materials which can be used internally but would not stand up to typical environment in which the camera is used. For this reason a DLC (diamond like carbon) coating is often applied to the external lens element which has reasonable transmission but is also highly durable.

HEAR stands for 'high-efficiency anti-reflective coating' and give best performance in benign environments. DLC (diamond-like carbon) has reasonable performance and will withstand the harshest environments.

NETD or 'noise equivalent temperature difference' is a measure of the sensitivity of the sensor or system. NETD is usually measured in milli-Kelvins (mK) and the smaller the figure the better the performance.

The 'sensor pitch' is the distance between pixels on the sensor. Infrared sensors are Micromachined and pitches are typically measured in microns. As might be expected, the sensor pitch does determine the size of the sensor array (for same number of pixels) and smaller pitches can mean smaller optics. However the sensor pitch must be considered together with other system parameters when judging system suitability.

Microbolometers (and other infrared sensor arrays) suffer from non-uniformity i.e. each pixels is a separate entity and the outputs of different pixels typically do not match. If uncorrected this can yield an image that is simply unusable. Non-uniformity correction is the name given to the process of removing these variations from the image.