David R. Shafer

Four mirror unobscurred anastigmatic telescope with all spherical surfaces

A variety of four-mirror telescopes are described, all corrected for spherical aberration, coma, and astigmatism; all unobscured; and all with spherical surfaces. Performance is discussed with an afocal beam expander and a flat-field telescope as typical design examples.

Zoom null lens

A simple null lens is described that is moved back and forth relative to a point source to provide large amounts of variable wave front aberration. This device can be used to test a wide variety of optical components and systems.

Simple Method For Designing Lenses

A simple method is described for quickly and easily designing high-performance optical systems. It involves little iteration, if any, and requires neither a computer nor extensive hand calculations. The systematic application of this design method allows one to construct configurations where the function of every surface is clearly understood. As a result, new design configurations tend to suggest themselves to the designer. This insight, which is an integral part of the design method to be described, also makes it clear how to compound designs so as to extend the f/# and/or field of view over which high performance is obtained. Although the design method only uses well-known principles of aberration control, it combines them and systematically applies them in a particular way that has not gained the wide use it merits. Several design examples illustrate how this design method is applied. They include a telephoto lens, an inverse telephoto lens, a fisheye type lens and a catadioptric system.

Null lens design techniques

There are a surprising number of discrete, well-corrected null lens designs with just two elements for testing a large, fast-speed parabolic mirror from its center of curvature. Some design techniques are discussed for generating these solutions, which may be applicable to the design of null lenses for other mirror shapes. Without examining these multiple solutions, which differ greatly in performance, there is no way to know if the optimum configuration has been found.

Simple Method Of Correcting The Aberrations Of A Beamsplitter In Converging Light

A simple method of correcting exactly the third order aberrations of a tilted plate beam-splitter in converging light is presented. Various well corrected design examples are given.

Optical Design With Only Two Surfaces

A wide variety of designs are described, using only two optical surfaces, that can perform useful functions with good aberration correction. Several use no aspherics.

Large Telescope Designs With A Spherical Primary Mirror

Very large telescopes of the future will be much more practical to build if the large primary mirror can have a spherical surface. This greatly reduces the time and expense required to optically figure a large surface. Several two-mirror designs are discussed which have a spherical primary mirror and a sub-aperture diameter aspheric secondary mirror. The light path reflects off of both mirrors twice, and the system is corrected for spherical aberration, coma, and astigmatism. Designs with small obscuration are possible if astigmatism correction is dropped. Scanning arrangements for huge Arecibo-type systems are also discussed.

Anastigmatic two-mirror telescopes: some new types.

A type of two-mirror telescope is described in which light leaving the secondary mirror is allowed to reflect off the primary mirror again before coming to the final focus. It is shown that this double bounce off the primary mirror results in a telescope that may be configured to be corrected for spherical aberration, coma, and astigmatism. In fact, there are four distinct families of designs that are anastigmatic, encompassing a wide variety of optical forms. The more interesting designs are described in detail, and some performance numbers are given.

Gaussian to Flat-top in Diffraction Far-field

A very simple and cheap method is shown for making a gaussian laser beam have a flat-top energy distribution in the far-field.

Well-corrected Two-element Telescope with a Flat Image

The three element Schmidt-Cassegrain telescope is a well-known catadioptric system that can be corrected for spherical aberration, coma, astigmatism and Petzval curvature. This paper describes a ve...