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The Strehl ratio, in the form of McCutchen's theorem, is employed to design a spatial filter that increases the depth of focus. Computer-simulated images show the increment in focal depth.
A new approach for obtaining line-spread functions (LSF's), which vary slowly in out-of-focus planes, is described. Based on this approach, we report a LSF that shows relatively less sensitivity to focus errors than that shown by both the diffraction-limited LSF and a LSF previously reported.
The optical transfer functions for variable focus error are contained as a single picture representation in the ambiguity function that is associated with the pupil function. This picture representation is shown to be useful for designing pupil functions that increase the depth of focus. We specify a criterion for an optical transfer function with low… (More)
We show that a zone plate with a prespecified number of foci, which are separated axially by Rayleigh's limit of resolution, can create an arbitrarily high focal depth when used as an apodizer over an otherwise clear aperture. We discuss the resolution and light gathering power of this method.
Apodizers with relatively high transmittance over an annular region of the exit pupil can reduce the sensitivity to defocusing and to spherical aberration [Opt. Lett. 11, 487 (1986)]. Here, we analyze the imaging properties (pupil functions, point spread functions, optical transfer functions, and Strehl ratios) of the Bessel type of annular apodizers. We… (More)
The theoretical development of dynamic holographic gratings with piezoelectric crystals is presented. A thin layer of photoresist is applied over the surface of the piezoelectric crystal. A holographic grating was recorded over the photoresist-piezo device in such a way that when it is activated the changes in its dimensions produce a geometrical change in… (More)
Space-invariant and space-variant filtering of discrete images with unidimensional variation is performed in this paper through the Wigner distribution function (WDF). Low-pass, bandpass, and high-pass filtering is used in the Fourier domain and in the Wigner distribution, to compare their different behavior in both cases. A space-variant filter is… (More)
In this paper we propose an alternative technique for producing digital Fresnel holograms. The evaluation of a diffraction pattern in a wide region is implemented in such a way as to avoid redundant calculations and preserve the precision. Because of the symmetry of the kernel, the complex amplitude is calculated at four points in the registration plane… (More)
An optical digital processor based on the Wigner distribution function (WDF) has been implemented, permitting space variant filtering of 2-D real images. The processor sequentially generates all space samples of the distribution; thus, each sample can be modified by a different filter. The filtered Wigner distribution function is optically inverted, and a… (More)