The standard EMVA 1288 describes a complete set-up for the experiment and the measuring requirements. First, it is important to shield the camera against any ambient light and to work with a defined monochrome illumination. The wavelength can be chosen arbitrarily. Moreover, the image sensor should be illuminated very homogeneously. This is accomplished best by a set-up without an optical lens and by making use of a Lambert's emitter. The standard´s description of the geometrical configuration is comprehensive and very easy to understand. The diameter of the emitter in combination with the distance to the camera should result in an f-number of 8. Figure 1 shows the set-up used in our experiment. The light source is an approximate Lambert's emitter with a diameter of 25 mm. Consequently, the distance to the camera is 200 mm.
In addition the following settings on the camera are necessary: It is important that the geometrical centers of both components are positioned along the same axis and that they stay parallel to each other. The grey level resolution (number of bits per pixel) must be as high as possible.Through a higher bit number the ADC receives more steps to discretize the analogue signal. The higher the resolution, the lower the quantization noise. The amplification must be as low as possible but high enough to ensure that the noise is greater than or equal to one grey value.The Offset (Black Level Calibration) must be as low as possible but high enough to ensure that the signal in darkness is greater than or equal to one grey value.No automatic corrections and/or settings may be used.
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