Spread Function

Spread Function

 

a function of an optical device that describes the distribution of illumination of the image of a small (point) radiation source created by the device. The spread function permits evaluation of the resolving power of the device and defines the relationship between illumination distribution in the image formation of an object and intensity distribution of the same object; having determined the illumination distribution in the image and knowing the spread function, it is possible to determine the intensity distribution of the object.

By definition, an ideal optical device represents a point radiation source as a point; in this way, its spread function everywhere except for that point is equal to zero. In real devices, as a consequence of the diffraction of light and the presence of aberrations and defects in the construction of the device, the image of a point source occupies an area of finite dimensions and the spread function differs from zero according to the limits of this area.

Considerable difficulty is encountered in the calculation of the spread function in the presence of aberrations and other factors; in view of this, the spread function is usually determined experimentally.

In application to spectral devices, the concept of the spread function has a somewhat different meaning. If the spread function of a spectral device is known, it is possible to determine the true energy distribution in the spectrum of the radiation source under investigation by the results of recording of the spectrum.

REFERENCE

Rautian, S. G. “Real’nye spektral’nye pribory.” Vspekhi fiziche-skikh nauk, 1958, vol. 66, no. 3, p. 475.

I. V. PEISAKHSON

References in periodicals archive ?
By exploiting approximate blurring point spread function (PSF) kernel, they proposed the work as "A Subband-Specific Deconvolution Model for MTF Improvement in CT." It can perform well even in the soft tissue region.
tries to estimate blur kernel or blur point spread function from a query blurred face image.
Image deblurring is an example of signal restoration: the recovery of an approximate of the original image, which was convolved with a point spread function and altered by additive noise.
In the first approach it simultaneously restores the true image and point spread function. this begins by making initial estimates of the true image and PSF.
All systems have a built-in "Agar Spread Function," which ensures homogenous distribution and an even surface on media.
One method is simply to remove the dominant scatterer by subtracting its point spread function signal from the received signal [8, 9].
And if the point spread function (PSF) is symmetric, the matrices A, L, and [A.sup.T]A + [L.sup.T]L can be diagonalized by the two-dimensional discrete cosine transform.
In essence, the intensity distribution of this kernel can be mathematically expressed as an oriented line spread function (LSF) that spreads as a Gaussian function in the theory of imaging systems [21-23].
A simulation of SRF based on Line Spread Function (LSF) is reported by Mouroulis et al.
In stimulated emission depletion (STED) fluorescence microscopy, the point spread function can be narrowed beyond the diffraction limit through the usage of a secondary toroidal depletion laser beam [23-25], whereby optical resolution is pushed to few tens of nanometers (A somewhat related improved resolution in the spectral domain is obtained in high-contrast Doppler- free transmission spectroscopy [26,27], also relying on a non-linear response-saturation).