2D Sub-pixel Point Spread Function Measurement Using a Virtual Point-Like Source

2D point spread function (PSF) is a commonly used measure to assess the quality of various imaging systems. The most convenient way of 2D PSF measurement is taking an image of a light source with its size well below the diffraction limit of the imaging system. In this paper, we present a novel method that allows formation of such a virtual point-like source by a simple setup with a convex spherical mirror and a collimated light source. Sub-pixel 2D PSF measurements are possible by displacing the setup in sub-pixel steps. Comparison of the 1D modulation transfer functions estimated by the proposed method and the International Organization for Standardization (ISO) 12233 standard shows that the proposed method presents a viable alternative to the ISO 12233 standard. Furthermore, future work on calibration patterns and algorithms for sub-pixel 2D PSF estimation from a single image could benefit from the presented method, which provides ground truth sub-pixel 2D PSF measurements for real imaging systems.