Imaging quality automated measurement of image intensifier based on orthometric phase-shifting gratings

A method for automatically measuring the imaging quality parameters of an image intensifier based on orthometric phase-shifting gratings (OPSG) is proposed. Two sets of phase-shifting gratings, one with a fringe direction at 45° and the other at 135°, are successively projected onto the input port of the image intensifier, and the corresponding deformed patterns modulated by the measured image intensifier on its output port are captured with a CCD camera. Two phases are retrieved from these two sets of deformed patterns by a phase-measuring algorithm. By building the relationship between these retrieved phases, the referential fringe period can be determined accurately. Meanwhile, the distorted phase distribution introduced by the image intensifier can also be efficiently separated wherein the subtle imaging quality information can be further decomposed. Subsequently, the magnification of the image intensifier is successfully measured by fringe period self-calibration. The experimental results have shown the feasibility of the proposed method, which can automatically measure the multiple imaging quality parameters of an image intensifier without human intervention.