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Using wipers with thermal cameras

Thermal cameras are becoming the ­solution of choice as the people discover their benefits.

Thermal cameras are unbeatable in dark nights, misty conditions and smog. The detectors used in thermal imaging cameras produce a clear image in adverse conditions. By glancing at the thermal camera housing, it seems to look a lot like a normal optical camera and we have found customers asking us if thermal cameras must be equipped with wipers, or, should they be cleaned more frequently.

Optical cameras housed in an outdoor housing are often fitted with wipers. However, by using wipers only, they tend to scratch the window of the housing during cleaning. Flir Systems has found that the wipers are a neat item to look at, but in the real world they offer little if no usable benefit when installed on a thermal imaging camera.

Multiple reasons for not installing wipers:

One of the first reasons for not installing a wiper setup onto the thermal camera housing is that you do not need to remove the dirt, salt or water droplets on the lens. The particles are very close to the camera and completely out of focus. This means that you will not even see the particles on the thermal image. Furthermore, the particles are so small that they are not obstructing the infrared radiation that goes through the lens and that is captured on the detector, to create a crisp clear image.

In the extreme case where the lens is so much contaminated with dirt that it does interfere with the quality of the image, it is recommended that the lens is cleaned manually, without using a wiper.

Although a thermal camera looks almost the same as a standard optical camera, it is far from the same thing. Optical cameras use a glass lens, which does not transmit infrared radiation well, and thermal cameras use a metal, Germanium, which is a good transmitter of infrared radiation. Germanium is a very expensive material and it is covered with a carbon coating. Although this carbon coating is a protective layer on the lens, it can be scratched during the wiper operation. The scratches will minimise the effectiveness of the detector.

Wipers are widely used in humid conditions. Manufacturers use a built in heater system on the lens which will prevent condensation on the lens. So again, there is no need to install wipers.

Not only will the wipers damage the carbon layer, it will add to the increase of maintenance of the camera system. It is very difficult to install a wiper system with a sprayer on a continuous rotation unit and allowance must be made for the curvature of the germanium lens, as this lens is not a flat surface as the windows on a standard CCTV housing.

Therefore, the most effective solution in ensuring a crisp, clear and detailed image will be with the aid of a high pressure hose, as this will be the most cost effective as well.

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