Deriving instrumental point spread functions from partially occulted images

TL;DR

This paper introduces a semi-empirical, semi-blind method to derive the point-spread function from partially occulted images, improving image correction and resolution without requiring predefined PSF models.

Contribution

A novel algorithm that accurately derives the PSF from various partially occulted images without assuming a specific functional form, applicable in diverse imaging contexts.

Findings

Central PSF weight accuracy better than 1.2%

Reconstruction error typically between 0.5% and 5%

Applicable to laboratory, astronomical, and eclipse images

Abstract

The point-spread function (PSF) of an imaging system describes the response of the system to a point source. Accurately determining the PSF enables one to correct for the combined effects of focussing and scattering within the imaging system, and thereby enhance the spatial resolution and dynamic contrast of the resulting images. We present a semi-empirical semi-blind methodology to derive a PSF from partially occulted images. We partition the two-dimensional PSF into multiple segments, set up a multi-linear system of equations, and directly fit the system of equations to determine the PSF weight in each segment. The algorithm is guaranteed to converge towards the correct instrumental PSF for a large class of occultations, does not require a predefined functional form of the PSF, and can be applied to a large variety of partially occulted images, such as within laboratory settings, regular calibrations within a production line or in the field, astronomical images of distant clusters of stars, or partial solar eclipse images. We show that the central weight of the PSF, which gives the percentage of photons that are not scattered by the instrument, is accurate to bettern than 1.2%. The mean absolute percentage error between the reconstructed and true PSF is usually between 0.5% and 5% for the entire PSF, between 0.5% and 5% for the PSF core, and between 0.5% and 3% for the PSF tail.