Study on a novel illuminance calibration method for signal to noise ratio measurement of image intensifier

Signal to noise ratio is a fundamental performance of a image intensifier, which shows the photons detection ability from object in low light level, and its determine detection range and image definition. The input illuminated circular area must be 0.2mm in diameter on the photocathode, input illuminance must be 1.02x10(-4)lx in signal to noise ratio value measurement of Image intensifier. So the paper study a novel illuminance calibration method, which uses PMT photon counting detection technique. The method can directly calibrate illuminance value of very low light sources in signal to noise ratio measurement device of image intensifier. First, we introduce the principle of low light image intensifier S/N tester. Secondly we research illuminance calibration method of 0.2mm in diameter on the photocathode of image intensifier, design quasi-point low light luminometer, which adopts the photon counting detection technique. So we research the radiation characteristic of standard light source with 2856K color temperature and calculate its output photon number, For high accuracy measurement on quasi-point sources, vision function correction and cosine correction is made. Lastly, we research the traceability diagram of this luminometer, which is traceable to our primary photometry metrology standard device. The experimental results indicate the novel illuminance calibration method can accurately directly measure illuminance of quasi-point sources. Comparing with the conventional calibration method this novel method avoids the transfer error. The absolute illuminance calibration uncertainty is analyzed. These analysis results are useful as a evaluating method for improving signal to noise ratio of Image intensifier.