Loose abrasive line-contact machining of aspherical optical surfaces of revolution.

A new fabrication technique for the generation of optical aspherical surfaces of revolution is presented. This fabrication technique combines the characteristics of conventional loose abrasive machining with features of high-precision machining tools. A prototype of the machine tool based on this fabrication technique is currently being developed. We describe the characteristics of this method. Fabrication of aspherical ultraprecise surfaces using a tube is a line-contact method for the generation of both on- and off-axis, convex and concave, aspherical surfaces of revolution. It employs a self-correcting process and enables the use of loose-abrasive ductile grinding [Appl. Opt. 30, 2761-2777 (1991)] and subsequent bowl-feed polishing [Appl. Opt. 26, 696-703 (1987); Opt. Eng. 31, 1086-1092 (1992); Appl. Opt. 33, 89-95 (1994)] for the generation of aspherical surfaces.

Generation of on-axis and off-axis conic surfaces of revolution by applying a tubular tool.

A new technique, fabrication of aspherical ultraprecise surfaces using a tube, is applied to the generation of conic surfaces of revolution, which also demonstrates that it is possible to generate different kinds of surfaces with the same tube. Surfaces are considered that are generated with the same tube with an elliptical edge but with different off-axis distances and different angles between the tube and the surface. Subsequently it is shown that the generated surface is always a radial section of a conic surface. In addition it is proven that the shape of the generated conic surface is independent of the off-axis distance. With each elliptical tube edge a range of different conic surfaces can be made depending on the angle between tube and surface. The more the tube edge resembles a circle, the larger will be the range of different surfaces. For each tube an angle between the tube and the surface exists at which it generates an on- or off-axis part of a semi-ellipsoid. Finally, an optimization technique is presented for the determination of the best combination of process-determining parameters for the generation of a certain conic surface.

Equivalent layers: another way to look at them.

We describe the behavior of the equivalent refractive index (or Herpin index) and equivalent phase thickness in relation to the phase thicknesses of the layers in a dielectric stack. This relation is visualized by a diagram that provides insight into the existing solutions for given combinations of the Herpin index and the equivalent phase thickness. Furthermore, it can be used for the explanation of the occurrence of stop bands and of the dispersion of equivalent layer stacks.

Adaptation of the refractive indices of antireflection coatings to other surrounding media.

The design of various types of antireflection coating is extensively described in the literature. In practice, however, such designs must often be adapted to other surrounding media or angles of incidence. For such cases, a method is presented in which, starting from a known antireflection coating, a useful reflectance characteristic is obtained for changed situations.

Thickness measurement using Young's interferometric experiment.

The paper describes an interferometer for use in the thickness determination of optical thin films. The standard deviation obtained by repeated measurements is of the order of 0.3 nm. In those measurements, the thickness is obtained as a fraction of the applied wavelength, which consequently acts as the unit of length. The method does not require a layer of known thickness for calibration.

Optical monitoring of nonquarterwave stacks.

The planning of an optical monitoring process for nonquarterwave stacks, using standard equipment for turning value monitoring, is a rather complicated procedure. It is shown that by using a computer program together with some simple rules the planning becomes a more straightforward task. Detailed examples are presented.

Nonpolarizing beam splitter design.

A three-step design procedure is developed for dielectric stacks which are required to be nonpolarizing for a given wavelength lambdar and angle of incidence theta 0,r, at which the reflectance Rr is prescribed. The method leads to solutions in which only three layer materials occur and can be applied for a wide range of values of theta0,r and Rr. The media can be chosen from the available coating materials. Furthermore, the procedure offers the possibility of optimizing with respect to the behavior of the reflectance in the neighborhood of lambdar and theta0,r. An example is elaborated, and its results are compared with an actually produced coating.