Estimating the PSF of space camera based on in-orbit wavefront sensing

ABSTRACT An accurate estimation of the point spread function (PSF) is very useful in image restoration. This paper proposes a method of estimating the PSF of space camera based on in-orbit wavefront sensing. Three wavefront sensors are used to measure the wave-front errors of the spac e camera, with one sensor in the center field and the other two sensors in the two edge fields. The wavefront erro rs of other fields can be estimated by interpolation. Then, the PSFs of each field can be estimated using the wavefront errors. For monochromatic light, the PSF can be calculated by Fourie r Transformation. For a white light imaging system, the PSF is a weighted integration of the monochromatic PSFs. The weighting coefficient is the product of the sun-light spectrum, spectral reflection factor of the object, spectral transmission factor of the optical system, and the spectral response of the image detector. Becau se different object has a different spectral reflection factor, to be practical and simple, we use an average spectral reflection factor of typical ground scenes instead. It will induce error in the PSF estimations by using the averag e reflection factor instead of the real one. This error is analyzed in the paper which show s that the error is acceptable. Key words : remote sensing, wave-front sensing, point spread function, image restoration