Nonimaging optics was d2vlop2d to solve a wll—posd but narrow s2t of probl2ms1. A prototjpical xampl is th concentration of a light beam with div2rgnc half—angl2 e and cross—s2ctional area A1 into th2 minimum possible area A1 without loss of throughput or convrslj, th design of illumination sstms that convert a lambrtian source into a beam with divrg2nc half—angle e and no stray light without loss of throughput. Two class2s of algorithms have bn found which solve ths probl2ms xactl or narftj so. Ths ar summarized hr; th details can b found in Rf.2. Th first is th "string' or 'dg2—raj" m2thod (the 'Hottl string is a useful construct for calculating radiative transfer b2tw22n lamb2rtian surfacs3). It maj b succinctly charactrizd as: I ndl = constant along a string. (1) Notice that replacing string b 'ra" gives all of imaging optics. Th second class of algorithms places rflctors along th2 lines of flow of a radiation fi2ld st up bj a radiating sourc2. In cases of high sjmmtrj such as a sph2r or disc, on obtains ideal solutions in both two and thr22 dim2nsions. In cithr case rflcting and somtims rfracting 2l2mnts ar shaped in specific wags in combination to solv2 th problem. Rcntlj I addr2ss2d a wider class of problems that could not b solved bj th old methods. Hr ar two xampls: It is w2ll— known that th2 far—field illuminance from a lamb2rtian source falls off with a power of the cosine of the radiating angle cx. For example, strip radiators produce a cos3cx illuminance on a distant plane, while circular disc radiators produce a cos4cx illuminance. But suppose one desires a predetermined far—field illuminance pattern e.g., uniform illuminance? The old designs will not suffice; thej simpftj transform a lambertian source radiating over 2'rr into a lambertian source radiating over a restricted set of angles. Another example is more technical. We recall1 that older nonimaging designs require that reflectors be positioned verj c1os to th source (or r2civr). Violating this ru1 introduccs undsirab1c structure in th radiating or angular accptanc2 pattern of th d2vic, tpica1ftj a dip in th forward direction. Th limitation o th old d2signs is that thj ar too static and d2pnd on a fw paramtrs such as, th area of th beam A1 and th div2rgnc2 angl2 e. 0n2 n2ds to introduce additional dgr2s of rdom into th nonimaging designs to solve a wider class of probIms. Th purpose of this communication is to indicate th lines along which this additional frdom can b introduced.

Experiments were performed to validate the IR scene generation concept using a thin film galvanic cell based on a phenomenon in which silver ions are electrically injected into a thin film to modulate the transmission of IR radiation through the film. By fabricating a two- dimensional array of the thin film galvanic cells and electrically addressing them, an IR scene may be simulated.

The design and system performance of an infrared phase-stepping interferometer is reviewed. This instrument is capable of measuring rms surface roughness with a repeatability of 0.02 waves. The instrument uses a 4-bucket unwrapping algorithm. Calibration of the interferometer and removal of inherent system aberrations are discussed along with the system performance, including repeatability and accuracy. The interferometer is an all-reflective optics design to permit use at any wavelength, accommodating both far- (10.6 micron) and near- (5 micron) infrared sources. Testing applications include infrared windows and surface testing.

A non-contact (i.e., optical) technique is required to measure the deformation of a free oil surface under the influence of a localized thermal load. This deformation is caused by surface tension driven thermal convective flow inside the fluid, and can be as large as 250 micrometers . Therefore, conventional interferometry is not possible. Instead, a Ronchi technique is proposed for contour mapping the oil surface. This paper presents a design concept for a two channel Ronchi instrument and some preliminary results from a feasibility study using a single channel Ronchi instrument.

In recent years, the manufacturing of parts with compound surfaces relies more and more on computer integrated manufacturing (CIM) because of the ever increasing complexity of surface features. For a standard CIM cycle, it starts from a computer aided design (CAD) model which was designed previously be experienced mechanical drafters. The CAD model is then interpreted as numerical controlled (NC) machining codes according to which the part is finally manufactured, this is usually referred to as the normal manufacturing process in Figure 1. However, in many cases, a CAD model of a part is not always readily available to begin the CIM cycle. For instance, in automobile industry, the development of new car models takes a long time from concept to model because of the tedious manual digitization process. Also, in some other cases, the mechanical design of a product may need frequent modification, such as ship hulls, aeroplane fuselages, wings and turbine blades, etc. This was traditionally done by copymilling of a master model. In a computer aided manufacturing (CAM) environment, a mathematical model or representation of a part is required to begin a CIM cycle. The automation of the whole manufacturing system requires a rapid part modeling tool. Fortunately, this becomes possible with the advent of recent development in optical sensing devices and many non-contact sensing techniques. Before a part model is established, surface digitization should first be implemented so that enough measurement points can be fitted later, and this is the most important step of the reverse engineering process as in Figure 1. And also, it is obvious that the efficiency and accuracy of the surface modeling relies heavily on the efficiency and accuracy of the surface digitization. The present paper aims at achieving surface digitization accurately and rapidly with a coordinate measurement machine (CMM) and an inexpensive laser range-finding probe. By making full use of the control system of the CMM and the sensing device, a feed-back control module has been developed to achieve accuracy, speed, and economy at the same time. This economical system can achieve the same or higher level of accuracy than expensive machine vision systems.

Testing injection molded aspheres, with large deviations from spherical is difficult. One solution is to use a long wavelength interferometer, such as an infrared interferometer. Another solution is to use moire. This paper presents the use of a projection moire system to test the surface shape of an injection molded f/0.1 parabolic reflector. The theory of moire and its effective wavelength is presented. A projection system is constructed and data taken for a reflector is shown. Finally, some alignment errors associated with the system and how to correct them is presented.

Partially transparent plastic eyeglass frames are susceptible to fracture due to stress from oversized lenses. Using a dark field polariscope, likely fracture points can be predicted.

Interferometry is an optical testing technique based on the interference of light. Fringes are formed when the optical path difference (OPD) between a reference beam and an object beam is an integral multiple of the illuminating wavelength. This OPD is extracted through the process of sampling, ordering, and interpolating. This paper develops a linear-algebra vector notation model of the interferogram sampling and interpolation process.

In this paper we describe the fabrication of replica Wolter I optics from gold-coated lacquer- polished mandrels and the effect of plating bath temperature on the surface quality of electroforms produced from lacquer-polished substrates. We also discuss the use of ceramic masters to electroform replicas having high-frequency surface roughness as low as 3 angstroms.

An experiment to study the characteristics of the cladding-length-dependent sensor has been performed using an optical fiber with silica core and lossy liquid cladding (mercury). The results show that the output light power is linear and sensitive to the change of lossy cladding length and acceptance angle.

This paper presents two methods for improving and evaluating the imaging quality of the multi-core image fiber. A square shape preform technique is employed to decrease the deformation of element fiber and a lateral view method is proposed to measure the number, diameter of element fibers and to test the twist of image fiber. The results of experiments showed that these methods are effective to fabricated high quality multi-core image fiber.

The state of polarization of light propagating in a polarization-preserving fiber may be varied via the acousto-optic effect by introducing high-frequency acoustic waves into the core region of the fiber. This effect may provide active polarization control for applications in interferometry, switching, and amplitude modulation. This paper describes a method for inducing polarization coupling within an optical fiber by coupling bulk shear acoustic waves through the flat surface of an elliptical-core D-fiber. The theory of device operation is developed, and a device model is characterized. The effect is experimentally verified with a first-generation device achieving approximately 7% amplitude coupling efficiency at 2 W input electrical power at a frequency of 22.7 MHz.

This paper investigates a polarimetric fiber optic strain sensor embedded in concrete. A comparison is made between a table version and a recently developed integrated version. The problems and concerns of successfully embedding optical fiber into the harsh cementitious environment are discussed. Experimental data is presented and compared to a simple theoretical model of stress induced birefringence.

Quite often, the strongest motivation for the selection of an IR window is its transparency in the particular region of the spectrum in which a sensor behind it views the outside world. Generally, the requirement for high transmission in the sensor passband overshadows considerations about absorption in other parts of the spectrum. The existence of high-power radiation sources at wavelengths outside the window passband makes the window highly susceptible to damage. The application of IR-resonant meshes is being investigated as a means of reducing this susceptibility without intolerably degrading passband transmission.

Presented is a description of a preliminary qualitative study of the effects of spherical particle scattering on the polarization of linearly polarized He-Ne laser beams. Data were acquired for various concentrations of particles (either 0.22 micrometers or 0.494 micrometers diameters) in filtered, distilled water. The effects of some physical parameters, such as the detector acceptance angle and cylindrical scattering volume container diameter, are demonstrated. In general, the larger the diameter particles used and the higher the particle concentrations the more the incident beam is depolarized. Increasing the path length traversed by the scattered beam greatly depolarizes the beam (i.e., larger containers and detector positions at depth).

Large signal two-wave mixing in photorefractive materials was studied. A theory based on the Kukhtarev-Vinetskii's model was developed. The coupled-mode equations for large modulation was obtained and their numerical solutions were found. It is shown that large modulation reduces the coupling coefficient of the two-wave mixing interaction, and, therefore, the effective gain. Theoretical results of large modulation agree well with experimental measurements.

A HeCd laser and a BaTiO₃ crystal were used to obtain a self-pumped phase conjugate beam. This effect is applied to perform an optical tracking filter. A modified liquid crystal television is used to imprint an input image on the laser beam. The input image presents moving and stationary elements of a scenery. The light transmitting through the crystal reveals only the moving elements, whereas the phase conjugate beam only carries the stationary portions of the input image. Therefore, a real time novelty and monotony filter has been realized. There is a lower speed limitation which depends on the response time of the crystal. The high speed limitation is dictated by the electronics. Due to the single-beam requirement of self-pumped phase conjugation, the imaging optical system is simple, making the experimental apparatus compact and versatile. The self-aligning property of self-pumped phase conjugation allows a wide range of incident angles without changing the system performance.

A closed loop digital/optical pattern recognition system is presented, using a photorefractive correlator. A personal computer is used to control an optical cross-correlator, consisting of a 4f-Fourier processor with a BaTiO₃ crystal in its Fourier plane. A test pattern is inserted into the optical system, via a modified liquid crystal television. The test pattern is stored in the photorefractive crystal, using a two-wave mixing technique. Several master patterns are compared to the test pattern using the optical cross-correlation technique. The output signal of the optical cross-correlator is detected by a CCD camera, and is transferred to the PC for evaluation. The spatial resolution of the optical system is examined both theoretically and experimentally.

This research uses merged epitaxial lateral overgrowth (MELO) of crystalline silicon combined with a multi-dielectric layers as a high reflection mirror; resulting in high-quality silicon Fabry-Perot cavity with well-controlled cavity length and high Finesse. The MELO technique has been employed in the development of novel devices such as accelerometers and pressure sensors. Also, the same growing techniques, selective epitaxial growth (SEG) and epitaxial lateral overgrowth (ELO), have already been applied in development of three dimensional MOS and bipolar transistors. Hence this cavity forming technique is integrated circuit compatible.

Photorefractive crystals are being used as a means of capturing the spatial information of two coherent light sources interacting within them. Typical recording procedures, important crystal parameters, as well as holographic applications are described.

The holographic storage capacity of an azo dye-doped polymer is demonstrated using a self- referenced interferometer in a two-wave mixing arrangement. The system possesses the ability to store absorption gratings and has the peculiar property of being able to record the complete polarization of the incident light field. The film is used to store a wavefront which is compared to its displaced version at a later time. Diffraction efficiencies of up to 10% have been observed. A theoretical description and experimental results of the interferometer are presented as well as a description of the dye/polymer system in various polarization configurations.

Various holographic methods of imaging through highly scattering media such as biological tissue are described. Experimental results are given.

Described in this paper is a compact phase measuring ESPI system that incorporates single mode fiber and diode laser. The single mode fiber along with diode laser provides ease of system arrangement but also causes wavelength fluctuation and instability. The wavelength instability was reduced to an acceptable level with an optical isolator. Experimental studies on wavelength stability of the diode laser, the back-reflection intensity from the fiber ends, and their influence on the system are presented.

A portable holographic interferometer that can be used to measure displacements and strains in all kinds of mechanical components and structures is described. The holostrain system captures images on a TV camera that detects interference patterns produced by laser illumination. The video signals are digitized. The digitized interferograms are processed by a fast processing system. The output of the system are the strains or the stresses of the observed mechanical component or structure.

In this paper a comparison of different techniques to obtain vibration patterns by phase stepping on an electronic speckle pattern interferometer (ESPI) is made. The theoretical evaluation of the contrast of the fringes shows that the (pi) phase step method gives good contrast; however, the four step method gives the same contrast along with better pictorial representation. Speckle averaging on the other hand also increases the contrast of the fringes apart from smoothing of speckles. Experimental results corroborating the theoretical predictions are also presented.

The correspondence problem is the problem of establishing a one-to-one correspondence between the same physical features in multiple images of a scene. Solving this problem is an important task that arises in the computer automation of many visual processes. In this paper, we discuss how the neural analog diffusion/enhancement layer (or NADEL) can be used to address the correspondence problem. Implementation results are presented in the context of a real problem in biomedical image processing: construction of 3-dimensional models of cytoskeleta organelles in a nerve fiber axon from 2-dimensional cross-sectional images of the axon.

In this paper we use a neural network called the Lyapunov associative memory (LYAM) system to segment image texture into different categories or clusters. The LYAM system is constructed by a set of ordinary differential equations which are simulated on a digital computer. The clustering can be achieved by using a single tuning parameter in the simplest model. Pattern classes are represented by the stable equilibrium states of the system. Design of the system is based on synthesizing two local energy functions, namely, the learning and recall energy functions. Before the implementation of the segmentation process, a Gauss-Markov random field (GMRF) model is applied to the raw image. This application suitably reduces the image data and prepares the texture information for the neural network process. We give a simple image example illustrating the capability of the technique. The GMRF-generated features are also used for a clustering, based on the Euclidean distance.

In this paper the competition between two modes in a uni-directional ring resonator having photorefractive gain, is investigated. Each mode is defined in terms of different frequency and angle of incidence. The interacting beams are assumed to be plane waves with an amplitude varying along the direction of propagation only.

A virtual image replay system has been constructed at the Fermi National Accelerator Laboratory to replay holograms produced in experiment E-632. The holograms were produced by a modified in-line holographic system installed in the 15 ft. bubble chamber detector. The experiment produced 110,000 holograms useful for physics analysis. The holograms were recorded on 70 mm Agfa-Gevaert Holotest 10E75 film. The bubble images represent tracks of charged particles produced from high energy neutrino interactions. Since one of the main purposes of the experiment was to observe short lived particles, our holographic system makes it possible to record smaller bubble images (approximately 100 mm) than possible with conventional photographs (approximately 500 mm) which record the entire visible chamber volume (28 m³) and are subject to the limitations of conventional photography i.e., diffraction of the camera lens aperture. Although the holographic volume is 1.5 m³, 20 - 30% of all the interactions in the bubble chamber fall within the holographic volume since the beam is concentrated in the center of the chamber. An important aspect of the experiment is the inspection of the holograms and for this reason an effective replay system is necessary. We have constructed a low cost replay system and chosen a virtual image replay because it requires much less laser power and this has proven to be a great advantage. We discuss the major components of the holographic replay machine and the relevant design features. Replay wavelengths different than the original recording wavelength are possible and corrected for in the system described. The resolution of the system is improved using a liquid film gate. A fiber optic reconstruction reference beam has been useful and convenient. Examples of replayed bubble chamber events are shown.

A brief summary is given of each of the 66 papers presented in the eight sessions at Optical Engineering Midwest 1992 held on March 19, 1992 at the Illinois Institute of Technology in Chicago, Illinois. Each session is also related to some national topical issue.