The objective lens is a single element glass lens with one aspheric replicated surface and one flat surface. The manufacture of the aspheric surface by means of replication is suitable for high quality mass-production.

Gas lasers have shown to be capable of delivering tens of terrawatt aspeak power or tens of kilowatt as average power. The efficiencies of most high power gas lasers are relatively high compared with other types of lasers. For instance molecular lasers,oscillating on low lying vibrational levels, and excimer lasers may have intrinsic efficiencies above 10%. The wavelengths of these gas lasers cover the range from the far infrared to the ultra-violet region, say from 12000 to 193 nm. The most important properties are the scalability, optical homogeneity of the excited medium, and the relatively low price per watt of output power. The disadvantages may be the large size of the systems and the relatively narrow line width with limited tunability compared with solid state systems producing the same peak power.

A rigorous experimental analysis (=acceptance testing) of the dimensional and temporal stability of an ultra precision machine involves the actual manufacture of such components that, as witness sample, allow the application of optical testing. The paper illustrates performance and quality verification tests for ultra precision air bearing spindles and slides with error motions ranging much below lium. Systematic machine errors are pinpointed. Repeated machining on the same surface allows the measurement both of vibrations, and of temporal dimensional changes, as might be caused by thermal growth.

Stiffness of a machine must be known between the tip of the cutting tool and the surface being machined in order to correlate with microfinish. Signature of the machine tool and its environs are registered on the micro-machined surface. Imperfections are triggered by disturbances which may originate off the machine, from the machine, or by reaction between the tool and the workpiece. The machine transfer function is a complex mechanical system with many input points and resonance frequencies to be contended with. This paper deals with recognizable surface imperfections which are related back to mechanical parameters in and between the machine elements. To be complete, one must include spindles, slides, supports, vibration isolators, tool holders, tools, fixtures, and the workpiece itself. Their relation to sources of disturbance is discussed and examples are given of surface measurements made which identify the relation between machine stiffness and microfinish signatures.

A design procedure for flat, circular thrust bearings is presented here. The procedure is based upon a new dynamic model of the bearing and the principle of tuning the bearing's dynamic stiffness to optimize the dynamic performance of the overall, machine-bearing system. The design procedure is iterative so as to satisfy a number of different design constraints and is illustrated in an example problem.

A brief description is given of the successful development of a large computer controlled machine for diamond turning aluminium alloy X-ray mirror substrates (1.5 m (60 in.) dia., 600 mm (24 in.) axial length). The in situ metrology facility for axial profile, roundness and diameter measurement is described, together with the technique for automatic programming of the final tool path to compensate for errors of workpiece deflection, tool setting and edge radius, etc.. Examples are based on the ROSAT and SXT mirrors for which the axial and radial location/mounting surfaces are produced with precise reference to the reflecting surfaces. Adaptation of this type of ultra-precision machine/metrology facility to the production of other types of optical components is also discussed.

Simple techniques for an assessment of the depth and intensity of plastic work, or sub-surface damage, in single point diamond turned components are described. Based on microhardness measurement techniques, the approach outlined here gives good qualitative correlation with conventional metallographic approaches for sub-surface damage assessment. Some data indicating variation of sub-surface damage with changing process parameters is presented; the aim of the paper, however, is to outline possible test methods and stimulate discussion. Possible approaches to measurement of tool sharpness are also discussed, again with the aim of eliciting comments.

The diamond turn process affects the metal-surface in a complex way. The knowledge of the relevant mechanisms (influence of polycrystallinity, crystal structure, grain size, mechanical behaviour) shows a new way to optimize optical metal surfaces by using micro-crystalline metals.

The feasibility of high speed diamond turning of optical glasses at room temperature without production of brittle chips has been studied for a wide variety of inorganic glasses. Transparent and nearly stress free new surfaces are produced by microshearing of the glass in a viscoplastic manner due to adiabatic melting and instantly annealing at higher cutting speeds. It is shown that both plastic cutting speed and maximum usable feed rate are strongly dependent on glass type.

The fracture mechanisms of brittle mode glass grinding are investigated using a high stiffness, single point abrasion system, where depth of diamond penetration and speed is controlled during the scratching of the glass. Normal and tangential forces on the glass are recorded and related to scratching speed, depth of cut, and types of damage observed for speeds between lOmm/s. and 14m/s. A reduction in these forces, but with increased levels of signal oscillation due primarily to chipping in front of the diamond ,is observed with in-creasing diamond speed. The presence of water in the abrasion zone acts to reduce brittle zone scratching forces in a highly speed dependent manner.

Roughness of micromachined surfaces and certain error motions occuring in micromachi ning may be determined by evaluating the mechanical interaction between two surfaces micro-machined successively on a substrate such as to form a small prismatic angle of, say, 1 arc.sec. Thereby a ridge is generated with a texture interlacing the two individual cutting patterns. Such substrate calibrates the phase - or interference - contrast image of samples in a range extending below about λ /20. Below that limit, it is impossible to correlate the image intensity profile with the surface relief. With RET one can measure the depth of machining profile in the order of between 0.01 and 0.005 pm, using a common microscope.

Relief angles and rake angles of end mills, reamers and thread taps are often formed by surfaces with a width of less than one millimeter. Sample inspection using a contour projector, which up to now has been applied in the manufacturing process of these tools, requires a destruction of the sample. This paper shows a non-contact and non-destructive method for measuring these angles. The technique features a directed illumination of these surfaces. An optical detector configuration is used to determine the direction of the reflected beam. This direction describes the angular position of the surface against the measuring system. The relation between coordinate system of the tool in the illuminated spot and the reference system of the optical measuring device is determined by a second setup. Both optical angle measurement and the determination of the coordinate systems lead to the measurement of the cutting edge angles. As for the example of an end mill the reproducibility attained amounts to about +0.1°.

The advent of rapid figure generation at the University of Arizona has prompted the development of rapid metrology techniques. The success and efficiency of the generating process is highly dependent on timely and accurate measurements to update the feedback loop between machine and optician. We will describe the advantages and problems associated with the in-process metrology and control systems used at the Optical Sciences Center.

Although the advantages of optical techniques have long been appreciated, the inherent limitations of such methods have meant that stylus techniques remain the accepted "standard" for surface assessment. The study of many engineering processes, such as engine preparation techniques, have been based on stylus methods. Much of this research may be extended to optical techniques for surface assessment if a detailed comparison of results obtained from the two techniques is carried out with respect to the process under investigation. A study of this kind will help to develop optical assessment techniques which, although will initially be limited to specific processes, may prove useful in the production environment. This paper presents a study of established two dimensional models which have been applied to the characterization of the preparation of engine cylinder liners and bores. These models are extended to three dimensions and quantified using a three dimensional stylus measuring system consisting of a computer controlled Talysurf 5 stylus instrument and a precision linear translation stage. Relocation techniques are then employed and the surface finish is assessed using a computer controlled laser measuring system. With reference to the original models it is shown that engine preparation techniques may be monitored using an optical assessment of this kind. Thus an alternative method of assessing the evolution of engine preparation is proposed for optically based techniques. It is hoped that studies of this nature will eventually lead to the development of an on line optical surface assessment system for engine preparation techniques with all its associated advantages.

A novel highly precise distance measurement tool is introduced. Using an optical autofocussing head and a backlash free mechanical translation mechanism, it is possible to reach a resolving power of 0.1 micron and an absolute accuracy of better than 1 micron in combination with a measurement range of 40 millimeters. Due to the character of the autofocus it is also possible to recognize on-line the inclination and curvature of the surface.

Over the last five years the Aspheric form has become a commonly used geometric shape, primarily in the optical industry for components such as contact lenses and compact disc laser focusing optics. The dimensions of these Aspherisities are sub-micron, yet must still be controlled to retain the designers intended function of the component. This control can be attained by measurement of the Aspheric form using a contacting stylus instrument. The measurement data, stored in the microprocessor, can now be fitted to the designers required form and after least squares alignment can be removed to leave the error of form introduced during production. Having obtained this error, it is possible to vary the designers input parameters to minimize this error and hence determine the absolute adjustment required on the component generator. This paper firstly explains what an Aspheric form is, and describes a systematic method of quantifying departure from the required geometry and concludes by showing a practical example of how these results can be used to adjust the Aspheric generator as part of an in-process close control loop.

An interference system has been studied and its ability in measuring surface profiles is shown. The precision of the interference system is easily up to 0.05 μm, and its measure-ment range is independent of coherence length of source. In this system, a crating is used, and its spatial period and ruled length respectively influence the precision and measurement range of the system. If a long and fine grating is used, both high precision and large measurement range can be obtained at the same time.

Mechanical measurement of deep aspherical optics during fabrication is presented. The center of curvature of the best-fit sphere of the aspherical surface is aligned with the axis of a precision air-bearing rotary table. A Linear Variable Differential Transformer (LVDT) gage measures the difference between the aspherical surface and the best-fit sphere. The data is plotted against the calculated data of the final surface. The measurement is repeatable and accurate to a couple of micrometers, when the aspherical surface departs from its best-fit sphere by 230 micrometers.

Straylight Measurement, Interferometric Measurement, Schlieren Microscopy, Optical Distance Sensing and Capacitive Distance Measurement are reviewed in their potential for in-process metrology. Today existing restraints are outlined and development necessities discussed.

The process of single point generation of a surface, although convenient for the manufacture of aspherical surfaces without apparently the need for final polishing, usually results however in some residual surface texture. The effect of polishing defects, such as roughness and flaws, on the quality of different optical systems is reviewed and discussed in order to illustrate the significance of residual texture in terms of perceived quality and function. Different methods for in-process measurement of texture are described, together with results recently obtained on the measurement of turned surfaces at various stages of tool wear.

Laser scanners are a valuable tool for qualitiy control in hostile hot and vibrating environments. Their high measuring speed allows time minimisation of disturbing influences. The loss of accuracy of systems due to thermal distortion could be minimised by designing mechanical-optical systems with low temperature gradients and small differences between thermal expansions of the components. For application in the forging production a laser scanner measuring in situ a series of profile lines describing the hot forging tools has been designed using aluminium for all distortion sensitive mechanical and optical components.

A precise, non-contact measuring of structures, thickness and form deviation is of decisive importance for modern production methods. A measuring unit is described which senses the structures to be measured with a 1 μm Laser Focus employing the principle of dynamic focusing. An automatic focusing device with a precision of <2 nm provides constant 'contact' with the surface and the required lens movement is transformed into an analog displacement signal. Maximum vertical steps of up to 600 μm can be assessed. The highest measuring frequency is >600 Hz. In addition to a short introduction to the measuring principle, special emphasis is laid on practical applications in the sectors of glass material, roughness standard samples, diamond turned surfaces and soft materials.

Elektro-optical measurement systems for the measurement of microgeometries are of increasing importance in quality control. Disadvantages of the tactile probes can be avoided to a large extent by utilizing non-touching methods /1/. This holds for

This paper describes a phase-shifting, self-referencing, interferometer, designed for testing rapidly varying optical surfaces or a pulsed laser wavefront quality. It is the modified version of a general class of phase-shifting interferometers without moving parts: the phase shift and separation of beams are obtained with a stationary diffraction grating. The presentation includes results from experiments, and a review of the systems where its use might be appropriate.

As a low cost approach to fringe scanning profilometry, a commercially available Linnik microinterferometer was equipped with a CCD array, interfaced to an IBM PC. The instrument's potentials and limitations will be discussed.

On the basis of a recently established dyadic Green's function formalism describing the diffuse scattering of light from a rough surface, we investigate the fundamental integral equation describing, selfconsistently, the electromagnetic field in the selvedge, i.e. profile, region. With emphasis on the physical properties, a detailed description is given of the Green's function which by screened radiation couples the different external current density sources in the profile together. Numerical calculations showing the electromagnetic radiation in the plane of a flat surface stemming from an oscillating dipole just outside the surface are presented. Finally, a few remarks are presented concerning the determination of the selvedge field associated with a so-called strip geometry of the surface topography.

Phase-measuring interferometers were developed as laboratory research instruments and several such products are available commercially. However, the transition from laboratory to optical shop applications has been slow. This paper discusses the advantages of phase-measuring interferometry, the design features that an interferometer needs in order to operate in an optical shop environment, and the performance features of the data acquisition and analysis software package.

In order to achieve a high reproducibility and high working velocity in the production of high quality optics, Zeiss concepted a numerically controlled polishing/testing system which consists of a CNC-controlled polishing machine and a computer controlled measuring machine. The data can be exchanged between the two machines and thus used for an in-cycle optimization procedure for the optical surface to be machined. The requirements for the resolution of the measurement were given by the precision of the optical components which have to be tested on the machine: These will be mainly mirrors for applications with synchrotron radiation. Surface slope errors are specified there to be as small as 0,1 arcsec in some cases. This required the construction of a coordinate measuring machine (CMM) with a positional resolution of 10 nm in all three coordinates. The concept of the CMM is based on the complete separation of machine controlling and measuring systems. Thus the results of the measurements are not related to the quality of machine axes but to the quality of reference mirrors which form normals for the three coordinate axes. Experiments performed until now show a reproducibility of better than 0,1 arcsec. Both linear as well as scanning areal measurements have been performed until now and used for the optimization of high quality mirrors for synchrotron radiation applications.