Modulation transfer function testing system for EBAPS

Electron bombarded active pixel sensor (EBAPS) is a new type of vacuum solid hybrid low light night vision device, and the modulation transfer function (MTF), as one of the performance parameters of EBAPS, can reflect the transmission ability of imaging systems to different frequency components. However, there is currently a lack of corresponding testing methods in China. Therefore, in order to characterize and evaluate the imaging quality of EBAPS, a MTF testing system for EBAPS was designed and built based on the principle of image intensifier slit method for testing MTF. By driving the EBAPS device and using a USB interface to transmit the collected data to the upper computer for image analysis, the slit image was processed to obtain the line spread function (LSF), and the corresponding modulation transfer function curve was obtained through discrete Fourier transform. When the illumination at the slit target was 2×10⁻² lx, within a certain range, as the voltage increased, the MTF of EBAPS first increased and then decreased, and reached its maximum value when −1 000 V was applied. In the light imaging mode, by fine-tuning the relative position between the slit and the sensor imaging surface, the standard deviation of MTF values for several important frequency points obtained from 5 consecutive tests was less than 0.01, indicating good stability.