Angular aperture

About: Angular aperture is a research topic. Over the lifetime, 1771 publications have been published within this topic receiving 27257 citations.

Operation apparatus for correcting ametropia with laser beam

Abstract: An operation apparatus for ablating the cornea by laser beam and correcting ametropia of the eye comprising a diaphragm with variable aperture, which is disposed on the optical path along which the laser beam is irradiated on the cornea, a shading member for shading the aperture of the diaphragm in the meridian diameter direction of the aperture, which is capable of varying the shading area to the aperture of the diaphragm by changing the turning angle to the optical path, in which aperture diameter of the diaphragm and variation in scope of the shading area by the shading member being controlled, and a beam rotator disposed in the eye side to the diaphragm rotates the laser beam passed through the aperture of the diaphragm about the optical path, whereby the cornea is ablated thicker at the periphery than at the center so as to correct hypermetropia.

On Arbitrarily Perfect Imagery with a Finite Aperture

Abstract: In theory, an optical system with a finite aperture can be coated to produce arbitrarily perfect imagery over a limited field. When the object is of limited extent, this field can be made the optical conjugate to the object, so that the whole object is imaged with arbitrary precision. The required pupil coating approximates low-contrast cosine fringes over its central region, with a frequency and amplitude that rapidly accelerate as the aperture edge is approached. Here the maximum occurs as a narrow spike. The frequency near the central region varies directly with the total extent of the conjugate field, and inversely with the required central core width Δ in the point amplitude response. As Δ is made arbitrarily narrow, the point amplitude response approaches the form of a sinc function over the field of view. This function is precisely the point amplitude for a diffraction-limited pupil with a magnified aperture of 1/Δ times the given pupil aperture ! The only image property that is not in compliance w...

Analysis of the noncollinear acousto-optic filter

Abstract: Theoretical analysis of an acousto-optic filter using noncollinear interaction is presented. The various characteristics of the filter, including tuning curve, resolution, angular aperture and deflection angle, are determined. The theoretical calculations are in good agreement with the measured results of a TeO2 filter.

Alternative to Gabor's representation of plane aperture radiation

Abstract: An exact procedure based on frame discretisation is proposed as an alternative for overcoming the inherent limitations of the well-known Gabor expansion. Numerical comparisons of these two phase-space methods are presented in the context of aperture radiation to demonstrate the stability, efficiency and accuracy of the frame decomposition, thereby emphasising its advantages over the Gabor representation.

Propagation of cosh-Gaussian beams diffracted by a circular aperture in turbulent atmosphere

Abstract: An analytical formula for the average intensity of cosh-Gaussian (ChG) beams diffracted by an aperture in turbulent atmosphere is derived and some limiting cases are discussed. By using the average intensity formula, some numerical simulation comparisons are made and some special cases are studied, especially the influences of the ChG beam parameter (Ω0), the propagation distance, the aperture and its size on the average normalized intensity distribution. It is determined that the evolution properties of the average normalized intensity profile in turbulent atmosphere with aperture are different not only from those of free space with aperture but also from those in turbulent atmosphere without aperture.