Many - but not all-optical imaging systems meet the simplifying assumptions necessary for the Fraunhofer diffraction theory used by the FFTВ MTF algorithm. The sampling is set high enough to accurately model the PSF This means uniform distribution of rays on the entrance pupil remains reasonably uniform on the exit pupil The exit pupil is not significantly distorted concerning the entrance pupil. The region over which the diffraction PSF has significant energy is small compared to the distance from the exit pupil of the optical system to the image surface The f/# is large enough so that scalar diffraction theory applies The resulting MTF is the modulation as a function of spatial frequency for a sine wave object В although optionally the real, imaginary, phase,В and square wave response is available.ДЇFT-based methods of computing the Point Spread Function and MTF are well known and are based on Fraunhofer diffraction theory. The method involves a Fast FourierВ Transform ofВ a grid of rays traced to the pupilВ (hence the name FFT MTF). The MTF algorithm usedВ by the above analysis feature, which produces a graph of MTF for all spatial frequencies that the lens can support,В is based upon the Fraunhofer diffraction theory. The original image as produced by OpticStudio is of photographic quality. Note:В The apparent image quality is reduced by screen resolution and the compression of the image. The bitmap image analysis window below shows good image qualityВ in the section showing the three boys: but how do we quantify 'good'? The contrast ratio in the various line images provides quantitative data on the quality of the image formed. In this blog post, we look at various sampling schemes and MTF algorithms available in OpticStudio, and how each of those algorithms can be individually incorporated into the Merit Function.В While each algorithm has its corresponding optimization operand, the Contrast optimization method is preferred for optimizing against the MTF. OpticStudio can compute the MTF for either target type. For bar targets, it is measured in line pairs. For sinusoidal targets, the MTF is measured in the sinusoidal response - or cycles. MTF is measured per millimeter (mm) in focal space, and per milliradian (or some other angular unit) in afocal space. As a consequence of applying Fourier theory to image-forming optical systems, MTF describes the contrast in the image of a spatial frequency presented in the scene being viewed. Modulation Transfer Function (MTF) is an important method of describing the performance of an optical system. It is commonly used to specify lens performance, and as an optimization and tolerancing target during lens design. MTF describes the transfer of modulation from the object to the image as a function of spatial frequency.

Mtf from zemax file