A way to measure the target contrast in low light level based on image intensifier technology

Target contrast is an important factor that affects the accuracy of viewing distance evaluation result of low light level device. There is a great difference between night sky spectrum and day spectrum, and the contrast of night target is different from that of day, so it is very important to measure the night target contrast accurately. Based on the basic concept of contrast and the relationship between brightness and illumination, and according to the high matching between the spectral response characteristic of the 3rd image intensifier and starlight spectrum, the way to measure the night target contrast by image intensified CMOS is proposed in this paper. And a measuring device calibrated by standard light source of 2856K color temperature in the laboratory is founded. Then, the device calibrated is used to measure the target contrast in urban. The results show that the deviation of the target contrast measuring device based on image intensified CMOS is less than 6.5% after laboratory calibration, the target contrast measurement results in urban are consistent with the visual observation results, and the target contrast measurement results are reliable. The results in this paper can provide an effective measurement method to ensure the accuracy of viewing distance evaluation results of low light level device.