A previous paper (1) described spheric and aspheric thermal infrared optical systems that were designed for three hypothetical applications. This paper is a sequel in that it describes four designs - two spherical, two aspheric - formulated for a specific application. The application chosen is an afocal telescope of X 12.5 magnification having an exit pupil of nominal diameter and axial clearance of 11 and 24 millimetres respectively: the field of view of the telescope in scanner space is 70 degrees. The four designs are examined with respect to their performance and narcissus characteristics and also their size, complexity and ease of manufacture.

For optical systems with smaller field angle the correction of spherical aberration is advanced. For such systems the use of aspherics allows either improvement of image quality or reduction of the number of lens elements required to achieve the aforegiven image quality. Optical systems in the visible spectral region used for technical applications like optical data processing can be attached to this type. Here the use of aspherics is advantageous. By reducing the number of elements veiling glare can also be minimized. When observing systems in the infrared spectral region with not too large a field angle, the use of aspherics makes the corrections easier. This is important because in the infrared region only a few optical transparent materials are available. The possibility to reduce the number of elements allows the reduction of weight of the whole system. Typical aspherics for such systems in the visible and the infrared spectral region are shown and their advantages demonstrated. The required accuracy of these aspherics is specified.

Laser fusion, or strictly the use of laser power to compress matter to achieve high temperatures, requires optics to focus a laser beam with very high power density to a nearly diffraction-limited spot; thus lenses with aperture diameters of order 100 mm and focal ratios in the range F/3 to F/0.6 are required. The reasons for using aspherics will be explained and several designs will be described.

The physics of x-ray reflection dictates the use of grazing incidence mirrors in a wide range of focussing x-ray systems, and some typical instrument configurations are discussed. The advantages of using algebraic expressions derived by geometrical optics to analyse the effects on image quality of errors in figure and alignment of the mirrors are discussed. A formal outline of the derivation is presented in an Appendix. The analysis leads to the construction of an error budget on which the manufacturing strategy can be soundly based.

A wide class of geodesic components for integrated optics, that are capable of beam deflection and splitting, focusing and imaging, are described. They are obtained simply by inserting in the substrate of the optical circuit a depression (or protrusion) of suitable curvature. The majority of these geodesic elements have aspherical surfaces, that must be fabricated with high accuracy. A general analytical design procedure is reported, which can be used also to evaluate the effects of the fabrication errors. The experimental tests of some aspheric components, fabricated in glass substrates by conventional grinding and polishing techniques, have been satisfactory.

The design of lenses for an integrated optics spectrum analyser is critically examined. In this signal processing device, guided light is acousto-optically Bragg deflected by electrically generated surface acoustic waves, in directions determined by their frequencies. Single crystal LiNb03 is the preferred substrate material, and geodesic lenses are used for beam collimation and focusing. The lenses must be aspheric to overcome aberrations and to guide light into surrounding plane regions. The diverging beam of an infrared (0.85μm) semiconductor laser is edge-coupled into the waveguide, then collimated by a geodesic lens to a width of 7mm in the acousto-optic interaction region. The resultant deflected beams are focused by a second lens on a detector array having mm element snacing. The geodesic lens dimensions are 18.5mm focal length, lOmm diameter, 1.3mm centre depth, and 75μm maximum departure from spherical. Factors affecting the image structure, and hence frequency discrimination, are examined. Diffraction, and fitting a straight detector array to the focal circle, lead to images up to about 2.5μm wide. Crystal anisotropy and wave-guide scatter further degrade the image. Lens profile tolerances are about ±0.5 µm.

Philips Research Laboratories have developed the COLATH, a high-precision single-point diamond tool machining equipment for con-toured (spherical and aspheric) optical surfaces of revolution. Contour accuracy is better than 0.5 micrometers, surface finish is better than 20 nanometers (peak to valley). Work capacity is 200 millimeters diameter, with X-slide (tool) and 7-slide (spindle) travels of maximum 100 and 200 millimeters, respectively. A Hewlett Packard laser transducer system, interfacing a Philips P 9201 minicomputer, is incorporated for fully automatic X and Z-axis displacement control (resolution λ/40 ≈16 nanometers). The laser-beam path is totally enclosed. Hydro-static bearings and hydraulic drives (linear and rotational) of in-house design have been employed throughout. The oil of the hydraulic system and the ambient air are temperature controlled (± 0.2 centigrades). The COILATH machine is operational since early 1978; so far aspherics for mainly infrared optics and visible-light systems have been produced.

In the machining of optical components truth-to-form and surface finish are of critical importance and the adverse effects of vibration must be avoided if satisfactory work is to be produced. This paper discusses the two basic types of vibration encountered in the use of machine tools - forced vibration and chatter, and the ways in which they can affect finished workpieces. Some of the techniques available for investigating and solving vibration problems on machine tools are described and some of the design principles to be considered in reducing the susceptibility of machine tools to vibration are discussed.

The paper discusses two topics that the author has found to be of importance in the application of air bearings to diamond tool machine tools. The first topic discussed concerns the potentially poor performance, in relation to a machine tool, of an air bearing journal, if it is designed for the maximum possible static load carrying capacity. The problem is associated with a sometimes self-excited instability, associated with the compressibility of air. The second subject is concerned with two different types of non-influencing drive system , both of which have been used to promote a vibration-free mode of operation. One type of drive provides a uniform linear motion to an air bearing supported table on a diamond tool flycutter. The other type of drive has been used to provide angular velocity to the Headstocks of both a diamond tool lathe and an aspheric generator.

The section of a conicoid used for X-ray reflection optics has a slow change of curvature; i.e. the difference between a straight generator and the actual generator is quite small. A grinding machine has been built to generate a cone with a means of correcting from a straight line to the curve required. This correction is produced by means of a 20 to 1 lever system from a template with a magnified contour.

For testing aspheric surfaces, computer generated holograms are frequently used. Some methods of generating the holograms as well as a comparison of in-line and off-axis computer generated holograms will be discussed. Furthermore, examples tested will be analysed from the stand point of an industrial testing procedure.

Testing of aspherics by synthetic holography has many attractive features. Use of in-line holograms and tracing to scale of the hologram represents in our idea a simplification of the method. We recall the Principles of order filtering for in-line holograms. We also present the interferograms obtained in a comparison of the holographic method with classical interferometry, when testing a parabola opened at f/0.6.

We report the operation of a new instrument which measures with ± 5 nm precision the shape of steep aspheric surfaces. The instrument makes use of contacting probes, and its working is based on an optical differential technique. Special attention is paid to the mechanical construction, and a detailed error analysis is given.

The design and production of an fil aspheric focussing lens for a high powered laser system operating at 1054 nm is described- The degree of flexibility in the choice of parameters in the lens is commented upon These parameters are chosen carefully, an extramely versatile lens capable of a large vavelength cover is produced: its manufacture is also considerably easied On this latter point, a comparison is made between the manufacture of its aspheric surface by high quality, although conventional, optical manufacturing practices, with an asphoric generated and polished entirely by a CNC jig grinding machine.

Thermal polishing of a settled layer of glass grains on a ground aspherical substrate by heat transfer is described. The layer-glass and substrate-glass have the same index of refraction. A phenomenological description is given of transparent turning of optical glasses by a single-point tool. The glass is turned at an elevated temperature at about the American softening temperature. A process combining abrasive turning and viscous relaxation makes transparent turning of a limited number of glasses possible.

The functional performance of a workpiece depends on the method of manufacture which is often controlled by measuring the surface texture of the machined parts. This paper describes the internationally recognised method of surface texture measurement by a stylus instrument and describes the ISO recommended parameters. Reference is also made to statistical parameters.

For many purposes it is useful to describe a rough surface by some statistical parameters rather than deterministically; thus the variance of surface height and the correlation length may be useful statistical parameters which summarize the properties of surfaces produced by given methods. The use of scattered coherent light to obtain these parameters will be explained.

The 1933 LINNIK Point Diffraction Interferometer continues to offer new possibilities in non-contacting aspheric grazing incidence mirror testing. In this work we demonstrate the wave-front aberration of a stigmatic Soft X-Ray reflecting optic recorded at progressively shorter wavelengths to a current limit of 313 nm yielding a twofold increase in sensitivity over previously reported measurements.

The performance of an optical imaging system depends not only on the accuracy of figure of its individual components, but also on the accuracy of alignment of the assembled components. Provision for achieving alignment can be made by having the appropriate number of centring and tilt adjustments. However, the number of adjustments can be advantageously reduced by coupling centring and tilt so as to constrain adjustment to rotation about a chosen neutral point, thus optimizing the alignment achieved for a given effort. The concept can be implemented by using spherical interfaces, or reference mounting surfaces, and is discussed in relation to several x-ray imaging devices. Some wider applications, such as scanning and steering optics, are also discussed.

Tilt and offset of aspheric surfaces are detected by a narrow aperture interferometer which performs a zonal rotary scan by means of a precise air-bearing spindle. Positioning of unknown aspheric surfaces with respect to machining or measuring apparatus requires centration of the samples (i.e. tilt and offset) and also longitudinal setting. The accuracy of the scanning interferometer is based on the precise axis of rotation of an Intop-Watt-type air-bearing spindle which steers the contactlessly probing laser interferometer beam on a conical path. Thus, a center and an axis of symmetry are defined. The system allows alignment of the aspheric surface and it also permits to detect coincidence between the scan-cone apex and the center of the sphere best fit to the zone being scanned.

A non-contacting measuring method is devised for optically polished surfaces, i.e. for surfaces with sufficient reflection. By means of precision measurement of angles and distances between two positions, apexial and normal, the parameters of aspherical surfaces are found. The surfaces are defined by the equation of the meridional section. Presupposed are rotational surfaces arising through the rotation of a conic section around its axis, which is also the optical axis of the measured componentes. In analogy with spherical optics, where first the radius defining - thanks the equation of the curve of section - every point of the surface, is measured; halfparameter and halfaxis are determined for conic sections. The local deformations are interesting only after the type of curve and the equation of section have been determined. Methods of evaluation based on known constants of the instrument are determined. The results of measurement for concrete dimensions are compared to a surface with known parameters. The comparisons are made for a convex and concave spherical surface too. The block diagram of hierarchy for conicoids is established.