Optical transfer function: Difference between revisions

Revision as of 00:52, 27 August 2022

Revision as of 13:26, 30 November 2022

Line 1:

{{short description|Function that specifies how different spatial frequencies are handledcaptured by an optical system}}

[[File:Illustration of the optical transfer function and its relation to image quality.svg|thumb|right|400px|Illustration of the optical transfer function (OTF) and its relation to image quality. The optical transfer function of a well-focused (a), and an out-of-focus optical imaging system without aberrations (d). As the optical transfer function of these systems is real and non-negative, the optical transfer function is by definition equal to the modulation transfer function (MTF). Images of a point source and a [[spoke target]] with high [[spatial frequency]] are shown in (b,e) and (c,f), respectively. Note that the scale of the point source images (b,e) is four times smaller than the spoke target images.]]

The '''optical transfer function''' ('''OTF''') of an optical system such as a [[camera]], [[microscope]], [[human eye]], or [[image projector|projector]] specifies how different spatial frequencies are handledcaptured byor the systemtransmitted. It is used by optical engineers to describe how the optics project light from the object or scene onto a photographic film, [[Image sensor|detector array]], [[retina]], screen, or simply the next item in the optical transmission chain. A variant, the '''modulation transfer function''' ('''MTF'''), neglects phase effects, but is equivalent to the OTF in many situations.

Either [[transfer function]] specifies the response to a periodic [[sine-wave]] pattern passing through the lens system, as a function of its spatial frequency or period, and its orientation. Formally, the OTF is defined as the [[Fourier transform]] of the [[point spread function]] (PSF, that is, the [[impulse response]] of the optics, the image of a point source). As a Fourier transform, the OTF is complex-valued; but it will be real-valued in the common case of a PSF that is symmetric about its center. The MTF is formally defined as the magnitude (absolute value) of the complex OTF.