''Zerodur'' is a glass ceramic made by SCHOTT GLASWERKE, exhibiting special physical properties, while also being optimally suited for a variety of applications. Thermal expansion of ''Zerodur'' is zero over a large temperature range and temperature variations, thus, have no bearing on the geometry of workpieces, which makes ''Zerodur'' ideally suited for the use as mirror substrate blanks for astronomical telescopes, x-ray telescopes, or even for chips production, where maximum precision is a prime requirement. The temperature-independent base blocks of ring laser gyroscopes, as well as range spacers in laser resonators are likewise made of ''Zerodur''. ''Zerodur'' can be machined like glass, but unlike with many optical glasses the warming generated upon cementing and polishing does not cause any deformations of tension at the surface. The paper aims to provide a general view of the most essential properties of ''Zerodur'', its major fields of application, the manufacture and the machining in the forma of grinding and polishing.
Fiber reinforced plastic (FRP) is a modern material for light weighted constructions. However, by the inhomogenity of the material it is difficult to test it with conventional methods. This is valid as well for construction optimization as for nondestructive testing in production control. A good tool for the different tests is the holographic interferometry, because it invisions whole a field of deformations of a component under load. The use of holographic interferometry is shown in two examples which cover as well construction optimization as nondestructive testing: (1) Components of a radioastronomical antenna were investigated for construction optimization. The holographic interferometry was able to demonstrate the influence even of thin internal layers. (2) An application with different aspects is the test of an aircraft component. In order to detect defects, special loadings and special equipment has to be developed. The examples cover different aspects of testing fiber reinforced plastic components with holographic interferometry.
Several optical errors present in interferometer systems are examined in detail. Optical cavity errors are typically the primary limitation on measurement accuracy. Secondary sources of error include imaging distortion and ray-mapping (slope) errors. The effect of phase modulation/processing errors on precision is briefly discussed. Some on- site errors (operator technique and environmental effects) are also examined. Rules of thumb for error estimation are presented when applicable. Specific quantitative analysis is based on the Zygo MARK IVxp phase measuring interferometer.
In typical interferometric testing the part under test is measured against a reference standard. The measured result is the difference between the errors in the test and reference surfaces plus any addition errors introduced by the interferometer. For accurate qualification of the reference surface it is necessary to employ a technique that can measure the part absolutely. This paper examines an existing technique for absolute testing of spherical surfaces which produces a map of the entire surface. The capabilities of this technique, error sources, and experimental data will be examined.
This paper proceed with a revision of the basic principles involved in a method of optical microtopography that we are developing, presenting recent improvements. It is shown that a collimated light beam with a oblique incidence on a surface can be used to assess its distance from a reference plane if the bright spot produced on the surface is imaged onto a array of detectors which tracks its lateral displacement. The light beam is swept over the surface, so that large areas can be scanned. An account is given of some practical applications of the system. The system has been used with success to measure surface roughness of machined surfaces, thickness measure of silver and copper thin films, for the topographic inspection of the edge of silver films sputtered through different masks, for the surface inspection of polyethylene films and for non contact measurement of fabric thickness and relief mapping.
This paper initially describes the principles of laser-based dynamic fringe projection techniques, and more specifically, how these techniques have been exploited in the Dynamic Automated Range Transducer (DART). This instrument employs novel techniques to produce a high accuracy single point range measurement over a wide variety of distances. The latest miniature optical components lend themselves to the production of a small, low-cost, self-contained device, which is easily portable and suitable for use in on-line, automated inspection systems, or in the field. The development of the DART for three- dimensional measurements is described. Two methods are possible, either a single beam or twin-beam system. Using a CCD photodiode array with precise pixel geometry an accurate three dimensional mapping of an object can be achieved. The problems of processing the data from the various DART systems is briefly examined. For multi-pixel measurements a parallel architecture using fast digital signal processing devices is recommended.
Optical glasses, due to their high homogeneity regarding physical properties, and the ability to tailor key characteristics to meet the desired performance, find new applications in the wide fields of optics and optoelectronics. In the optical glass field the general development goals are: optical glasses with anomalous partial dispersion characteristics for apochromatic color corrections; glasses with reduced weight, so called lightweight glasses; glasses with improved UV- transmittance; new glass types for deep UV-applications; optical glasses with high homogeneity in diameter up to 1555 mm; highly prestressed windows dia. 930 mm for bubble chambers; the latest results will be presented. For radioactive environments and for space applications a variety of stabilized optical glasses have been developed. These glasses have been testes with electron-, proton-, neutron- and gamma radiation. Special glasses exist for the use in Cerenkov and Scintillation counters for particle research. Nonlinear optical effects in semiconductor doped glasses are under investigation.
The agreement between theoretical and experimental data forlight scattering from random rough surfaces has been investigated for several different wavelengths ofthe incident field. Theoretically the scattering from twodimensional surface roughness has a dependence whereas scattering from unidirectional surface roughness has a ? dependence. We have investigated this wavelength dependence experimentally. Our results show that perturbation theory gives a good agreement with experimental data when the root-mean-square (rms) roughness of the surface does not exceed about one twentieth of the wavelength of the incident field. These results have been obtained for scattering from several different materials and wavelengths indicating that theoretical calculations can be used as tool for assessing the influence of light scattering from surface roughness on system performance. The use ofexperimental surface profile data allows us to predict the scattering from a surface with good accuracy without any prior assumptions about the surface roughness. We have not bee able to verify experimentally the theoretical wavelength dependence of the scattered intensity
Wavelength change in a unbalanced interferometer makes phase change in interferograms, and this phenomenon can be used for the purpose of phase shifting interferometry. As an example of measurements, an optical plane parallel plate is tested, and the simultaneous measurement of both front and rear surfaces together with inhomogeneity of refractive index can be carried out. A new method for calculating phase distribution is developed under the condition where nonlinearity of tuning wavelength and fluctuation of output power take place.
A Laser Retroreflector Unit, consisting of an array of cube corners, has been designed and made for the satellite Aussat B. The design involved the study of cube corners with small angle offsets, the diffraction pattern they produce, the effects of surface coatings, and their transmittance at high angles of incidence. Interferometric tests were developed to measure during manufacture the angle offsets of the cube from which the retroreflectors were cut, and radiometric tests confirmed the final performance.
Laser diodes have the unique property that their output wavelength can be controlled by varying the injection current. This paper discusses some new interferometric techniques that utilize this property.
LOH created a method of oscillation free lapping and polishing of optical lenses which led to a considerable increase of quality. This method, named ''SYNCHROSPEED'', consists of computer calculations for tools and machine set up data, new designed tools and work-piece-holders and also specially developed machines. These facts enable the user to achieve a high repeatability even for difficult lenses. Last not least the set-up and production times were drastically reduced.
A computer based automatic measuring instrument has been developed to compute the power distribution of progressive lenses. The measurement principle is based on Talbot interferometry in which the self image of a Ronchi grating is made to interfere with an analyzing grating of equal period. The fringe patterns produced are captured with a CCD camera and digitized with a Data Translation DT2851 frame grabber card. A C- language software package has been developed to perform fringe analysis using spin filtering, weighted averaging, and fringe centerline extraction with the binary derivative method. The power distribution is computed from the slope of the fringe centers. The instrument has been applied successfully to evaluate constant power and progressive power lenses.
The Photon Scanning Tunneling Microscope (PSTM) is the photon analogue of the electron Scanning Tunneling Microscope (STM). It uses the evanescent field due to the total internal reflection of a light beam in a Total Internal Reflection (TIR) prism. The sample, mounted on the base of the prism, modulates the evanescent field. A sharpened optical fiber probes this field, and the collected light is processed to generate an image of the topography and the chemical composition of the surface. We give, in this paper, a description of the microscope and discuss the influence of several parameters such as - polarization of light, angle of incidence, shape of the end of the fiber - on the resolution. Images of various samples - glass samples, teflon spheres - are presented.
The optical beam induced current (OBIC) produced in devices by a laser scan microscope (LSM) is used to localize hot spots, leakage currents, electrostatic discharge defects and weak points. The LSM also allows photoluminescence measurements with high spatial and energy resolution. Using the infrared laser scan microscope (IR LSM), defects in the metallization and latch-up sensitive region could be detected from the back of the device.
A high sensitivity strain measurement procedure that combines moire interferometry and digital image processing, has been successfully implemented to determine thermally induced strains in electronic components. The technique is called Fractional Fringe Moire Interferometry (FFMI). It produces whole field displacement information that are used to compute strains in a certain plane. Displacements in the submicron domain are detected with excellent spatial resolution over the area of interest. An example is presented here to illustrate the use of the technique to monitor thermally induced deformations in a specimen made from a plastic DIP device. The specimen was uniformly heated from room temperature to 90 degree(s)C, and the resulting moire fringe patterns were recorded, analyzed using digital-image-processing and in plane displacements in the package were determined. Strain components were then computed by simple differentiation of the acquired displacement fields. Contour maps showing actual thermo/mechanical strain components in the device were constructed. Those maps can provide an excellent tool for strain analysis of microelectronic devices regardless of the structural complexity of the device.
Diode laser phased array of single-mode, single-lobe and diffraction limited far-filed pattern is pursued for many applications. According to coupled-mode analysis three types diode laser phased arrays have been designed and fabricated. The properties of these three types arrays show that the asymmetrical linearly chirped array can fulfill the application demands.
A new method is proposed for evaluating the local displacement of objects in speckle photography by using a Wigner distribution function (WDF). It is applied to evaluate the displacement of 1D specklegrams as well as specklegrams of the ground glass and rubber plate which are slightly shifted and stretched, respectively. As a preliminary study, the local spectra W(x,(omega) ) are qualitatively and quantitatively verified in comparison with the theoretical results and the conventional Young''s interference fringes. The results show the feasibility of evaluating the displacement of objects using the WDF.
The difficulty to achieve a refractive index matching between active substrate and active layer grown on, is one of the main problem in integrated optical devices based on gallium arsenide, because of its high refractive index value. One possible solution could be an active layer whose refractive index is variable during the grown. Zinc oxide is a very interesting material because of its electro-optic and acousto- optic properties. It has a low cost and can be prepared by a variety of techniques. In this paper deposition of lithium doped zinc oxide films by reactive sputtering has been investigated in order to study the dependence of optical properties on lithium content and deposition parameters. A ZnO:Li target was used. The film depositions were performed varying the oxygen content in sputtering gas. For comparison undoped ZnO films were also prepared. We have performed optical and electrical measurement on films relating the results to Li contents and O/Zn ratio obtained by nuclear reaction and Rutherford backscattering measurements respectively. The film analysis has shown that dopant concentration is mainly controlled by gas mixture. The optical properties are dependent on deposition conditions. Optical waveguides have been prepared and characterized. The results are presented and discussed.
The shadow moire method is used in conjunction with a Liquid Crystal Display (LCD) projection panel onto which is written a computer generated grating to display contours of the topography of objects. The ability of rapidly changing the parameters of the grating like the pitch and width of lines through the software makes this a versatile tool for shadow moire applications. Demonstration of the technique including means for rapid image enhancement are described in this paper.
Beginning with an analysis of the practical laser rangefinder system, this paper deals with (1) the restrictive relations between each main structural parameter of the optical system, (2) the main problem in the layout design, and (3) how to obtain the optimal design scheme of the total performance of the instrument subject to given technology by partially reducing the refractive index of the optical splitting prism material.
Results that have been achieved during the last 3—5 years by the Soviet specialists in the field of finish machining technology in mass production of optical components are presented. It is shown that due to the development of new grinding and polishing means (a range 01* diamond tools, hard polishing polyurethane—foam substrates, bound abrasive tools)a considerable advance has been made in finish machi— ning of optical spheres and planes.