Method and apparatus for measurement of spatial signal and noise power of imaging systems

摘要

A photographic facsimile of a line image at a predetermined orientation is illuminated by a collimated monochromatic light source to produce a diffraction pattern. The Fourier distribution of the diffraction pattern is focussed by a converging lens to image on a spatial frequency plane of spatial signal and spatial noise components. The image in the spatial frequency plane is applied to a detector for selectively measuring the spatial power contribution of the signal and noise components, thereby to provide a measure of image quality relating to imaging system signal-to-noise ratio. A spatial filter (18) may be introduced into the optical path to block the spatial signal components, while allowing the noise components to impinge on the detector. The line image is then reoriented in the image plane, and successive measurements of spatial signal and noise contributions repeated. The ratio of signal-to-noise power is then computed for each orientation of the line image. By simulating selected imaging components and generating a resultant line image, the effect of such components on noise may be determined.