DIN Standards Committee Optics and Precision Mechanics
DIN ISO 15529
Optics and photonics - Optical transfer function - Principles of measurement of modulation transfer function (MTF) of sampled imaging systems (ISO 15529:2010)
Optik und Photonik - Optische Übertragungsfunktion - Messung der Modulationsübertragungsfunktion (MTF) von abtastenden Abbildungssystemen (ISO 15529:2010)
Overview
This standard specifies the principal MTFs for sampled imaging systems. It defines the related terms, and gives a number of suitable techniques for measuring the MTFs. It applies particularly to electronic imaging devices such as digital still and video cameras and the detector arrays they embody. A very important aspect of sampled imaging systems is the aliasing which is tightly linked to such systems. This standard defines a measure for "aliasing". The importance is that it allows spatial frequency components higher than the Nyquist frequency to be reproduced in the final image as spurious low frequency components. This gives rise to artifacts in the final image that can be considered as a form of noise. The extent to which this type of noise is objectionable will depend on the characteristics of the image being sampled. Images with regular patterns at spatial frequencies higher than the Nyquist frequency (for example, the woven texture on clothing) can produce very visible fringe patterns in the final image, usually referred to as moiré fringes. These fringe patterns are not acceptable in most applications, if they have sufficient contrast to be visible to the observer. Even in the absence of regular patterns, aliasing will produce noise-like patterns that can degrade an image. Although a number of MTF measurement techniques are described, the intention is not to exclude other techniques, provided they measure the correct parameter and satisfy the general definitions and guidelines for MTF measurement as set out in ISO 9334 and ISO 9335. The use of a measurement of the edge spread function, rather than the line spread function (LSF), is noted in particular as an alternative starting point for determining the OTF/MTF of an imaging system. The International Standard ISO 15529 has been prepared by ISO/TC 172/SC 1 "Fundamental standards", the secretariat of which is held by DIN. On the national level, the responsible Committee is Working Committee NA 027-01-02 AA "Grundnormen der Optik" ("Fundamental standards for optics") of NAFuO.
