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A Concise Guide to Camera Testing Using Radiation Sources

16 August, 2017

A Concise Overview of Camera Testing for Avionics

Camera testing in the field of avionics requires the use of a range of different pieces of equipment, some of which rely upon the principles of black body radiation and thus involve integrating spheres. All three of the camera types considered below can be tested using such principles, but CCD-based day cameras may instead require a visible backlight. Take a look at the various electro-optical systems which can be tested and calibrated using specially designed test stations which examine the infrared and visible light sensors within.

Common Tests Used in Avionics

Despite the differences between the three camera types outlined here, testing regimes ultimately boil down to the examination of the same functions. This reflects the shared purpose of all cameras used in the field of avionics in both the military and civil sectors. The most common tests conducted on such cameras are as follows:

·         Resolution

·         Uniformity

·         Modulation transfer function

·         Minimum resolvable contrast

·         Signal to noise ratio

FLIR Camera Testing

Forward looking infrared cameras (FLIR) are generally used for thermal imaging purposes during night flights. They are always tested with the help of integrating spheres and a black body radiation source. Given the predictable and constant emission of such radiation, both cavity and extended area black bodies are very useful for calibrating FLIR cameras.

False positive results are practically eliminated when integrating spheres are used. A wide range of accessories can be used to test and diagnose such cameras by simulating several field conditions. For example, accurate infrared test patterns are generated with the addition of collimators and targets maintained at specific pre-defined temperatures.

Testing SWIR Cameras

Short wavelength infrared (SWIR) cameras generally operate between electromagnetic wavelengths of 0.7 – 2.5 micrometers, most of which is beyond the scope of typical silicon-based sensors. The indium gallium arsenide sensors that are optimal for such imagery can be tested by means of testing stations based on integrating spheres. The low light conditions generated by such stations are an excellent substitute for real-life obstacles like fog and water vapor.

Unlike FLIR testing, the inspection of SWIR cameras involves the use of cavity black bodies rather than the extended area type. Uniform cavity black bodies can operate at absolute temperatures of up to 1,200 degrees Centigrade, which makes them ideal for making sure that your SWIR camera will work to the highest level while subject to high thermal energies.

Examining CCD-based Day Cameras

Day camera testing equipment involves the use of visible radiation sources unlike those which are preferable for the various infrared cameras outlined above. While integrating spheres can and do operate within the visible light spectrum, day camera testing equipment also includes visible backlights.

Always Use a Correctly Tested Camera

Integrating spheres developed using the principles of black body radiation are vital to the proper function of camera testing stations in avionics. The only guaranteed way to conduct such tests appropriately is to involve measurable and constant sources of radiation. Whether you need a thermal imaging device for night use, a camera that works in low light conditions or a plain day camera, it’s incredibly important that you get them tested and calibrated properly.

Learning all about the proper methods of camera testing enables you to find precisely the equipment you need. Make sure you have the right tools for the job.

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