We introduce a multigrid preconditioned conjugate gradient (MGCG) iterative scheme for computing open loop wavefront reconstructors in the adaptive optics (AO) system of large telescopes. We present numerical simulations which indicate that our MGCG method has a rapid convergence rate for a wide range of sub-aperture gradient measurement signal-to-noise ratios. The cost per iteration is order N...

Radio observations establish the B/A magnification ratio of gravitational lens 0957+561 at about 0.75. Yet, for more than 15 years, the optical magnfication ratio has been between 0.9 and 1.12. The accepted explanation is microlensing of the optical source. However, this explanation is mildly discordant with (i) the relative constancy of the optical ratio, and (ii) recent data indicating possib...

This document describes the details of our simulation. We simulate the necessary optical phenomena that affect the image quality. We also show the results with an angle limiter. Figure 1: Misalignment error caused by the curvature of the image surface. Since the distance from the GRIN lens to the image point B is longer than the radius of the image surface, angle S 2 (= S 1) is smaller than S 3...

Radio observations establish the B/A magnification ratio of gravitational lens 0957+561 at about 0.75. Yet, for more than 15 years, the optical magnfication ratio has been between 0.9 and 1.12. The accepted explanation is microlensing of the optical source. However, this explanation is mildly discordant with (i) the relative constancy of the optical ratio, and (ii) recent data indicating possib...

Photo-thermo-refractive (PTR) glass is a photosensitive multicomponent silicate glass containing photosensitive agents such as cerium and silver. Photoinduced crystalline phase precipitation results in refractive index variations in exposed areas of PTR glass, which has been successfully used for phase hologram recording. Photosensitivity being the result of the partial absorption of the exposi...

Refraction is a detrimental problem in terrestrial optical measurements and can be regarded as major source of systematic errors in the precise determination of distances and directions. In general, refraction is a function of the density inhomogeneities of the propagation medium. As the "classical" method of temperature-gradient determination does not meet the requirement of a representative i...

As for homogeneous lenses, for axial gradients the analysis of the Seidel and chromatic aberration coefficients can be very useful in lens design. However, at present few commercial optical design programs list the Seidel aberrations of GRIN lenses and none of them lists the chromatic aberrations. In order to facilitate the computer implementation of the chromatic aberrations of axial GRIN lens...