This conference deals with commercial applications of precision manufacturing rather than research for its own sake. It is therefore relevant that we start by examining the pressures on industry. We live in a world of continuing change and this is reflect most forcibly in manufacturing industry where markets and the manufacturing is becoming more global, product lives shorter, and product variety ever greater.

This overview illustrates the range of existing applications for sub-micrometer processing of materials, and examines the limitations to further improvements due to the fundamental properties and microstructures. It is concluded that ceramic materials offer greater dimensional stability and quality of finish than metal alloys or polymers, provided that allowance is made for possibilities of damage in grinding processes. Novel materials and shaping and finishing techniques are examined as a means of improving the speed of production and cost-effectiveness of new and existing products.

Unconventional optical surfaces can now be readily manufactured with high precision. Good design practice requires that these surfaces be used to optimize the concept of an optical system rather than to provide a marginal performance improvement. The paper considers some of the possibilities.

For high-resolution optical imaging systems used in photolithography, lenses with diameters up to 200 mm and surface accuracies of about 25 nm are required. To realize an economic production of such elements, a computer-controlled polishing following classical techniques has been developed. Applications in the laboratory and production spheres are presented for components made from Zerodur, optical glasses and calcium fluoride.

Long term investigation into the production of optically flat, low damage surfaces has shown that the most time consuming part of the process is mechanically wear conditioning the polishing surface so that it produces the desired shape on the sample. A completely new concept in polishing systems has been produced which enables the operator to make precise changes to the polishing plate surface shape in resolution steps ranging from 50 nanometers over a 100 mm diameter sample to sub-nanometer increments for a sample of 10 mm diameter.

Samples of BK7 and SF10 optical glass were 'ductile' ground using a cast-iron diamond ring tool with an electrolytic in-process dressing system. Selected machining parameters gave nanometric quality surfaces (Ra < 2 nm) with minimal sub-surface damage. Relatively rough brittle fractured surfaces were obtained by machining the glasses with the same diamond wheel but without the assistance of electrolytic dressing. The grinding force (normal) generated whilst ductile machining was significantly greater than for brittle fracture grinding. The work described in this paper reveals a significant advance in the machining of optical glass. This novel and complex process requires further investigation to provide a full understanding of the science involved.

Low-damage surface-forms in brittle materials call for both form generation to within sub- micrometer limits and sub-micrometer cut depths. Traditional free abrasive-based finishing techniques incur restrictions in respect of determinism and manufacturing economics. The range of requirements and materials is expanding into volume markets so that alternatives are sought. Single-point investigations reveal a sub-micrometer ductile (plastic) regime not apparent at higher cut-depths or vibration-levels. Recent progress is described and prognoses offered for manufacturing and process economics.

This paper will examine the surface error which results as a consequence of fundamental axial spindle motion in the diamond turning process. A mathematical model of this error will be developed and contrasted with a traditional Zernike error fit. In addition, the effect of this error on the optical performance of these surfaces will be investigated.

Preliminary studies have been performed on small beams of silicon (1 X 6 X 40 mm) diamond machined by high speed milling/grinding. The effect of the grinding on the strength of these specimens has been assessed by masking a small portion of the surface and etching in a 1:9 solution of hydrofluoric and nitric acids for a set time. Removal of the mask reveals a step which is measured to determine the amount of material removed from the surface. These are then examined using x-ray diffractometry and the etch step surface finish measured using a Rank Taylor Hobson Form Talysurf stylus profilometer. Finally, the strength of the specimens is measured by loading the beams to failure in a small three point bend testing machine and monitoring the failure load. There is a slight increase in strength between the as-ground specimen and those where the surface has been etched by 1 - 2 micrometers . Both x-ray and stylus measurements indicate the presence of a surface layer of thickness of the order one micrometer that is likely to be due to ductile mode grinding. It is also noted that there appears to be a local peak in strength after approximately 2 - 3 micrometers has been etched from the surface. This is followed by a small reduction before steadily increasing to a maximum value of 425 MPa. It is speculated that this could be a result of a low defect zone around the tips of the cracks that are invariably propagated during the grinding process.

The aspheric lens has developed over many years to meet the needs of industry. Refinement in curve mathematics, methods of die surface generation, methods of moulding, up-to-date measurement techniques and mounting methods have led to the capability to produce lens elements with diffraction limited capability at economical cost. Such lenses are produced in wavelength ranges covering visible, near infrared and med infrared. An ever widening range of products is served, and the flexibility of plastics leads us to believe that many more are possible, at cost levels unobtainable by other techniques.

Hybrid ceramic bearings are now commercially available for use in high performance applications where the properties of the ceramic balls give advantages in terms of higher operating speeds, increased stiffness, lower fraction and less heat generation. Most hybrid bearings are high precision angular contact ball bearings fitted with silicon nitride balls, which have to be finished to ISO dimensional grades 3 and 5. Ball diameter variation and deviation from the spherical form has to be less than 0.125 micrometers for Grade 5 balls and less than 0.08 micrometers for Grade 3 balls. Surface finish of silicon nitride balls is typically 0.003 - 0.010 micrometers Rq (0.002 - 0.008 micrometers Ra). At this level, the basic material microstructures is discernible which facilitates inspection for material and other faults.

The use of excimer lasers and the development of deep UV lenses for the semiconductor industry has produced a technology capable of sub-micron feature generation. The high irradiance levels available at a working surface can give rise to various laser-induced processes that enable material to be removed or deposited precisely. One of the laser-induced processes that has received much attention over the last few years is ablation. The paper will concentrate on the relevant properties of excimer lasers, the development of deep UV lens technology and the phenomenon of ablation used for material removal. A number of examples will be given to illustrate the capability of excimer laser systems to ablate sub-micron features in polymers and other materials.

This paper describes a number of opto-mechanical components which have been specifically developed for packaging of semiconductor laser based devices and for components associated with these devices. These include miniature external cavity lasers, mode locked lasers and Fabry-Perot filters.

Microlenses have been with us for a long time as indeed the very word lens reminds us. Many early lenses,including those made by Hooke and Leeuwenhoek in the 17th century were small and resembled lentils. Many languages use the same word for both (French tilentillelt and German "Linse") and the connection is only obscure in English because we use the French word for the vegetable and the German for the optic. Many of the applications for arrays of inicrolenses are also well established. Lippmann's work on integral photography at the turn of the century required lens arrays and stimulated an interest that is very much alive today. At one stage, lens arrays played an important part in high speed photography and various schemes have been put forward to take advantage of the compact imaging properties of combinations of lens arrays. The fact that many of these ingenious schemes have not been developed to their full potential has to a large degree been due to the absence of lens arrays of a suitable quality and cost.

The potential advantages of hybrid refractive-diffractive elements in infrared systems are reviewed. It is shown that these advantages can be realized in practice by single point diamond turning. Indeed, their manufacture by this process is no more complex in principle than making conventional aspherics which is a well-established technology. The design and manufacture of a zinc sulphide hybrid lens for the 3 - 5 micron waveband is described.

Tetraform^R is a patented group of concepts which can be used to produce extremely high static stiffness and dynamic stiffness structures. A prototype machine tool, called Tetraform 1, has successfully demonstrated the concepts' advantages by grinding optical glasses and quartz to optical quality, at relatively high stock removal rates. The concepts, exampled by these grinding results, may be as applicable to high-speed and heavy machining as to ultra-precision and precision optical machining.

Cost-effective technique for producing longitudinal microgrooves in situ of near-optical quality has been developed to improve the aerodynamic performance of aircraft. The production technique utilizes a flexible tooling sheet, which is pressurized onto the painted surface of aircraft wings and fuselage under moderate temperature. In this method, the surface of aircraft is moulded with the pattern of the tooling sheet which can be mass-produced using conventional roller-rolling techniques. Both of the surfaces with thermo-plastic paints (e.g., acrylic lacquer) and thermo-setting paints (e.g. polyurethane) can be applied with this technique to produce triangular micro-grooves of 50 micrometers on the aircraft surface, which can save the jet-fuel cost by more than 2 percent.

Personal Manufacturing Systems are the missing link in the automation of the design-to- manufacture process. A PMS will act as a CAD peripheral, closing the loop around the designer enabling him to directly produce models, short production runs or soft tooling with as little fuss as he might otherwise plot a drawing. Whereas conventional 5-axis CNC machines are based on orthogonal axes and simple incremental movements, the PMS is based on a geodetic structure and complex co-ordinated 'spline' movements. The software employs a novel 3D pixel technique for give itself 'spatial awareness' and an expert system to determine the optimum machining conditions. A completely automatic machining strategy can then be determined.

Synovial joints at the ends of long bones, provide the means of articulation of the human skeleton. These joints provide varying degrees of freedom, from the simple hinge action of the elbow or the middle joints of the finger through the ball and socket joint of the hip to the complex rotating hinge with translation of the knee.

The paper will discuss some of the technology of sol-gel manufacture and will touch on such subtle problems as porosity of sol-gel prepared silica layers.

A brief overview is given of the papers presented in the session on Measurement and Characterization. Then techniques are mentioned that are appropriate for quantifying precision manufactured surfaces at the sub-micron level. The new techniques of atomic probe microscopy and long scan profilometers are highlighted.

With the invention of a new phase measuring technique, 'Direct Measuring Interferometry' (DMI), almost all practical difficulties of quantitative interferometry in production environment are solved to a large extent.

Through the consideration of a surface as a reflective phase grating, this paper establishes the various relationships between the statistical parameters of the surface topography and the far- field diffraction pattern. These relationships have been incorporated into Talyfine, a new measuring instrument designed primarily for the measurement of flats and cylinders. The performance of this instrument is compared against established stylus-based surface texture measuring instruments, Talystep and Form Talysurf.

Calibration of machine tools and co-ordinate measurement machines can be a lengthy business. New developments, based on linear interterometry, and novel software methods have drastically reduced the time required for machine calibrations and installation acceptances.

For the purposes of this paper, the measurement of shapes by optical noncontact methods is divided into two categories: 'simple' shapes, and 'complex' ones. Simple shapes are considered to be those that are near flat or spherical, and can be tested using conventional optical methods. Complex shapes are those that depart from flatness or sphericity by an appreciable amount, and currently need alternative test methods. A number of ways of testing complex shapes are described, and their relative merits are discussed.

This paper has been produced for use with the new BS4301 (1991). It describes a method for the objective measurement of surface damage such as digs and scratches on optical components. By comparison of image visibilities of defects with line and spot standards, scratches and digs can be quantified in terms of their line-equivalent widths and spot- equivalent diameters. The codes used on optical drawings are described and guidelines for surface damage thresholds are discussed. The preferred equipment to aid the various stages of inspection and measurement is described and the paper concludes with a flow diagram illustrating a typical system for the quality control of transmitting and reflecting components.

The difficulties of describing real rough surfaces in mathematical terms are introduced. The statistical treatment of height distributions leads to the application of time series analysis. But real surfaces often behave as non-stationary random processes, implying that their geometrical properties are not intrinsic constants but depend on sampling interval and sample length. Current attempts to incorporate these ideas into international roughness standards are described. Recent developments in fractal geometry have suggested a way forward, and some evidence is presented that rough surfaces on a nanometric scale may behave as self-affine fractals. Finally the difficulties of generalizing from two-dimensional descriptions to three- dimensional surfaces are discussed with particular reference to anisotropy.

This paper describes a compensation technique for the correction of repeatable rotationally- symmetric residual form errors in precision machined components. Details of the FTS2TPG software package, that connect a family of manufacturing equipment and metrology instrumentation together in a compensation cycle, are reviewed. In addition, examples are shown that demonstrate the level of compensation achievable with this technique.

Fluid Film Devices Ltd specialises mainly in the design and manufacture of self-acting or aerodynamic gas bearings. The geometric tolerances needed for these bearings can be of the order of O.lum. It was the need for rapid, noncontacting measurement of components, often made of ceramic material, that led to the re-development of the Pneumatic Probe (PP).

This paper describes the development of a novel mechanically scanned and non-contacting surface profiling technique in which measurements of electrical capacitance are used to maintain a small separation between the tip of a fine wire probe and the surface of the sample under examination as the probe is scanned over the surface. The principle of operation of the technique is described and examples of results obtained are shown. A prototype instrument has achieved a height resolution of approximately 5 nm and a lateral resolution of better than 500 nm, though these are by no means ultimate resolutions. This instrument also demonstrated the capability of the technique to measure surface profiles over both insulating and conducting surfaces. A commercial implementation of the technique offering 0.1 micron height resolution has recently become available and is described. Applications of this instrument and of the technique in general are discussed.

Many industries now require control of surface heights to sub-micrometre precision. The systems that calibrate quality control instruments for such applications must have capability at the nanometre level, or better, and excellent traceability. Xray interferometry is currently the strongest candidate for this task. As this paper demonstrates, it is quite feasibly used in a normal standards room yet provides accuracies of better than 0.1 nm. Following a description of the preferred meirological configuration, which uses silicon monolithic devices, some features that have improved its accessibility are discussed. Particular attention is paid to sensors and actuators that may t as transfer standards to provide convenient routine calibrations. Finally, a design for a stand-alone, desk-sized instrument is presented.