When I was an undergraduate student in physics at the University of Akron, I had a job as a page at the univer-sity library. Since I had served as a page at the Firestone branch of the Akron Public Library located across from the main gate of the Firestone Tire and Rubber Company, my campus position was both familiar and invigorating. In the summer when things went slack, we had time to inventory and reorganize the stacks. It was in the base-ment stacks that I found leather-bound volumes of the 15th and 16th centuries—books that I am sure now reside in special climate-controlled vaults. With leather under my fingernails I examined shelf after shelf. On the last pages of volumes that bound London newsweeklies were tabulations of the deaths in the city that year. The num-bers, as I remember them now, were in the thousands; they probably included only tradesmen and nobility. They were fascinating as real and immediate connections to a remote past.

Laser metrology has experienced escalating research, development, and application within the automotive industry since its inception.

This paper presents an overview of some recent progress in digital speckle interferometry and its application for vibration measurement in the automotive industry. It describes three methods to generate raw vibration fringe patterns with better quality; provides speckle averaging, phase shifting, and phase reconstruction iteration procedures to produce a high-quality and noise-free fringe pattern; illustrates one single setup for measuring both vibration deformation and geometric shape of an object; and demonstrates how powerful this tool is for whole vehicle modal survey, interactive design optimization, CAE model correlation, and nondestructive testing. Finally, areas for further development are suggested.

An optical microscope, utilizing the principles of time- averaged hologram interferometry, is described for microelectromechanical systems (MEMS) applications. MEMS are devices fabricated via techniques such as microphotolithography to create miniature actuators and sensors. Many of these sensors are currently deployed in automotive applications which rely on, or depend on, the dynamic behavior of the sensor, e.g., airbag sensors, ride monitoring suspensions sensors, etc. Typical dimensions of current MEMS devices are measured in micrometers, a small fraction of the diameter of a human hair, and the current trend is to further decrease the size of MEMS devices to submicrometer dimensions. However, the smaller MEMS become, the more challenging it is to measure with accuracy the dynamic characteristics of these devices. An electro-optic holographic microscope (EOHM) for the purpose of studying the dynamic behavior of MEMS type devices is described. Additionally, by performing phase measurements within an EOHM image, object displacements are determined as illustrated by representative examples. With the EOHM, devices with surface sizes ranging from approximately 35x400 to 5x 18 µm are studied while undergoing resonant vibrations at frequencies as high as 2 MHz.

One possible failure of microelectronic devices is due to leakage resulting from an imperfect hermetical seal in microelectronic packages such as microchips. This malfunction is often experienced in automobiles in which the electronic devices are exposed to hostile environments. Traditional leak-testing methods are very time consuming. A shearographic technique for rapid evaluation of hermetic seals is presented. The package under test is stressed by an external pressure change. With the pressure change maintained, the lid of a perfectly sealed package will remain deformed while a leaky package will not hold the deformation, which can be monitored by shearography. This leak testing is fast and practical and can be extended to testing pharmaceutical packages, food packages, etc.

In layered materials and structures, it is essential to observe stress and strain concentrations, strain gradients, failure initiation and growth, and local microstructure evolution. In this study, an innovative phase-shifting technique is proposed, coupled with image-processing software, to investigate several interesting problems in electronic packaging. A window-based graphics interface for phase shifting in a moire interferometry system is introduced. The phase shifting is accomplished by driving the reference grating in the moire interferometry system with a low-voltage piezo stack. Three images obtained from three shifts and the original image are used to derive the phase diagram, which is used for displacement and strain calculations. Automatic fringe numbering is achieved by the phase shifting, which significantly simplifies the traditional fringe-counting and -ranking process. The strain calculation is also automatic, utilizing the space derivative of the displacement. A three- point bending beam is used for the demonstration. In addition, a power plastic IC package and a flip-chip package are selected to demonstrate the power of the system. A nanoscale deformation field is obtained for both the corner area and the flip-chip solder balls.

Delamination buckling and growth are failure scenarios that lessen the structural integrity of laminated composite structural members. An experimental investigation of this failure mechanism in a twodimensional setting is carried out. When a delamination of an arbitrary planform is present at the edge of a structure, the response of the delamination may involve regions or points of contact with the undelaminated portion of the structure beneath it. The effect of this physical constraint is investigated by compressing model specimens that contain edge delaminations of rectangular planform with a fixed aspect ratio and varying thickness. Holographic interferometry is used to capture the deformation of the delaminated region, in particular, the deformation associated with the debond, so that insight into the growth of the debond can be obtained.

This paper describes the application of white-light optical interferometry to the nondestructive inspection of engine cylinder surfaces. A system has been designed and built specifically for application of this technique to the measurement of in situ engine cylinder walls. The system produces a three-dimensional measurement of the surface height over a 0.9x 1.2 mm region. A number of measurement results are presented, some of which are unavailable with a two-dimensional measurement.

A method that was originally developed for the investigation of microstructures has been adapted to the measurement of rough technical surfaces. Based on a combination of angular resolved light scattering measurement with a data analysis by linear multivariate regression, almost any surface parameter can be estimated. This includes height parameters such as the Ra and Rz roughness as well as spatial parameters such as the autocorrelation length T. To this end, a linear model is generated from several well-studied samples and some kind of a priori information. This model can then be used to calculate the surface parameters from the angular distribution of the scattered light. A generalized solution for the inverse scattering problem cannot be obtained, but the method is specially suited to measure deviations from rated values and to detect deviations in the machining process. In this paper, the basic principle of the method, a concept for the description of the angular distribution of scattered light, and the utilized data analysis technique are presented. Furthermore, the results of experiments that were made with honed surfaces may demonstrate its applicability in process control.

A scanning laser Doppler vibrometer (SLDV) is an optical instrument that can scan an area to measure the velocity field of structures. It has been widely used in the automotive industry. In some applications, the pose (position and orientation) of the SLVd are required. First, this paper describes two such applications. Then it presents a nonlinear regressive model for the pose determination of the SLDV with respect to a structural coordinate system. The model is derived from coordinate transformation and the scanner model. In it, the pose is expressed by six independent parameters: three for the translation vector and three for the rotation matrix. The six parameters are estimated by using the least-squares technique. Statistical inferences about this model are obtained by linear approximation. To determine the pose, four or more registration (reference) points are required. For each registration point, the structural coordinates and its corresponding input voltages need to be known. The model has been implemented in a laser-based data acquisition system, which has been used for modal analysis, structural dynamic modifications, and noise control.

Increased demands on the performance and efficiency of mechanical components impose challenges on their engineering design and optimization, especially when new and more demanding applications must be developed in relatively short periods of time while satisfying design objectives, as well as cost and manufacturability. in addition, reliability and durability must be taken into consideration. As a consequence, effective quantitative methodologies, computational and experimental, should be applied in the study and optimization of mechanical components. Computational investigations enable parametric studies and the determination of critical engineering design conditions, while experimental investigations, especially those using optical techniques, provide qualitative and quantitative information on the actual response of the structure of interest to the applied load and boundary conditions. We discuss a hybrid experimental and computational approach for investigation and optimization of mechanical components. The approach is based on analytical, computational, and experimental solutions (ACES) methodologies in the form of computational, noninvasive optical techniques, and fringe prediction (FP) analysis tools. Practical application of the hybrid approach is illustrated with representative examples that demonstrate the viability of the approach as an effective engineering tool for analysis and optimization.

Panel acoustic contribution analysis (PACA) is an advanced engineering tool to improve noise, vibration, and harshness quality and minimize weight of vehicles. it is a technique to categorize areas of vehicle body panels as positive (sound level increases as vibration amplitude increases), negative or neutral according to their contribution to the total sound. PACA is a hybrid of computer aided engineering and experimental methods. Computer aided holometry (CAH), scanning laser ve- locimetry (SLV), or an accelerometer net is used to experimentally measure structure vibration complex velocities. These velocities are the boundary conditions for a boundary element model of the acoustic cavity. Boundary element analysis is then used to predict the vehicle interior sound and calculate panel acoustic contributions. Experimental results for a welded steel box (validation) and vehicle application are presented.

The technique of retroreflective grating analysis is presented to measure surface contour. This noncontacting optical method can detect a dent with maximum depth less than 10 mm. A comparison with some physical measuring systems indicates that it has advantage over such contacting measurements, especially for specular surfaces.

A hybrid optical/digital system for detecting defects in optical fibers is proposed. Since the structure of the fibers is the multilayer coaxial cylinder with step indices, the defects in any layer change the spatial frequency spectrum of the fibers and can be detected by comparison with the spectrum of a desired perfect fiber. A joint transform correlator can carry out the detection by continuously updating the test fiber with the desired reference fiber in its stationary position. We show that by joint transform correlator, fiber defects can be successfully detected.

UV-IR cutoff filters consisting a number of alternating layers of TiO2 and SiO2 were prepared by reactive electron-beam deposition (EBD) at a glass-substrate temperature of 300°C and by reactive ion- assisted deposition (IAD) at an ambient substrate temperature. All the filters were prepared in the same coater, equipped with two electron beam guns and one advanced plasma source. The uniformity and reproducibility of filters prepared by both techniques were investigated and compared, and correlated with results from single-layer materials. The useful sample radii, with optical thickness variation less than 1.6%, for EBD and iAd filters were up to 50 and 30 cm, respectively. The run-to- run reproducibility of EBD filters was as good as or even better than that of IAD filters. However, the temperature stability of IAD filters was superior to that of EBD filters, which confirmed that the energetic ion bombardments made the component films denser.

A computer-generated diffractive optical element to produce 4 x4 spot matrix images was fabricated by electron-beam lithography. The element was applied to the inspection of paper sheets. Images of spot matrices were analyzed, and agreement between the reflectance measured by the present sensor and a spectrophotometer was observed. The sensor image was able to yield information about local curvature as well as defects. Moreover, sensor images from surfaces of different paper samples revealed material surface anisotropy in the cross-correlation analysis of image data.

A new method for designing diffractive optical elements (DOEs), based on the diffraction theory is reported. The method does not require complex computation and programming. The DOE can be easily designed according to simple formulas and has higher imaging accuracy. The DOE diffraction coefficient depends on taking the complex amplitude transmission.

A method of improving the band performance of fiber optic electric current measurement is described and put into test. An electric current sensing scheme with two metal-coated single-mode optical fibers in an Mach-Zehnder interferometer is employed. Experiments show that a comparatively large measurement bandwidth can be obtained by use of this method, in which only a low offset frequency component is detected, whatever the measurand frequency is. In the test experiments, we have shown a flat characteristic in frequency response up to 20 kHz.

A novel scanning fringe projection method is developed to simultaneously measure the variations in both position and shape of a swimming fish. This method combines the commonly used fringe pattern projection method and a laser scanning technique into one optical system. In this new system, one or more reference fringes are generated by an acousto-optic deflector, and laser triangulation is used to determine the order of the reference fringe. These reference fringes are then combined with the conventional fringe pattern, and the fringe order is determined from the reference fringes. The method enables us to simultaneously measure the position and shape of a moving object. We successfully apply the method to a swimming fish.

Based on a simplified model of Gaussian beam focusing, in which nontruncating, thin-lens, aberration-free, and on-axis optical systems are assumed and the thermal-lensing effect is neglected, a general and concise expression is derived to describe the variation of 1/e2 radius of the focused beam as a function of input beam waist to lens spacing, lens-to-target plane spacing, input beam Rayleigh range, and focal length of lens. From this expression, we get the depth of focus (DOF) of flying optics with a fixed flying range, which is used as a merit function to determine the optimal solutions for system parameters. The results are very useful in the design and analysis of flying optics in laser material processing. Finally, a practical example describing the optimization of the output coupler for CO2 laser resonator is given.

Digital image holography (DIH) is an interferometric method that allows one to superpose the states of the device investigated at different times. The interference fringes produced are similar to those obtained by real-time holography and are interpretable in the same way. High-contrast interference fringes are reliably obtained even under nonideal experimental conditions. In DIH a CCD camera captures the superposition of a phase-variant object beam and a temporally constant reference beam. The phase difference between these two beams is calculated. The way this is done differs from digital speckle pattern interferometry and other related methods. The temporal phase shift of the object beam is calculated from the phase difference between object and reference beam at two different times. The resulting interference intensity depends on the phase shift of the object beam.

A method is developed for feature-based coding of human face images. Deformable templates, wavelet decomposition, and residual vector quantization (RVQ) form three consecutive stages of the proposed method, which aims for recognition-based very low bit rate coding. Deformable templates are employed in localization of facial features and biorthogonal spline filters are used for the decomposition of segmented and normalized face images. Wavelet coefficients are zonal truncated before being vector quantized to generate multiresolution codebooks. Classified multiresolution codebooks are also generated for residual eye and mouth images to improve subjective quality of salient face features.

The main objectives of an engineering document management (EDM) system are outlined. Existing image compression algorithms [e.g., Group 4 (G4) and Joint Bilevel Image Experts Group (JBIG)] offer efficient solutions to the storage problem but do not sufficiently support other objectives such as spatial access and fast decoding. We propose a novel method based on JBIG in which the other objectives are also met. The compression performance of the proposed method is only 10% worse than that of JBIG, and at the same time, spatial access to a compressed file is achieved. The method is also 2.5 times faster in decompression than JBIG. This speedup is comparable to the G4 standard, but with better compression performance. The proposed method is applicable not only to engineering drawings but to binary images in any document imaging system.

Conventional medical image compression systems employ full-frame processing to avoid the blocking effect, which may lead to the incorrect diagnosis. But full-frame processing is time consuming and, worse, results in the blurring of sharp regions when the compression ratio is high. A new medical image compression technique based on 2 x 2 discrete cosine transform (DCT) is proposed. The 2 x 2 DCT has the ability to retain the detail characteristics of an image. Furthermore, it has the benefit of low computational complexity. By means of a simple transformation to gather the spectrum data with the same frequency domain and an information dominance strategy, the new compression technique promotes efficient coding when applied in the practical data management systems. The simulations are carried out on different types of medical images to evaluate the performance of the proposed scheme. The results verify the efficiency in terms of compression ratio, reconstruction quality, and processing time.

A new prediction technique using luminance compensation with adaptive block size for multispectral image compression is proposed. The luminance compensation based on a least-squares approach is updated block by block for efficient coding. The new technique exploits the property that the spatial features of neighboring spectral bands are almost identical. The image content of each band usually has almost the same spatial shape even when the pixel values are different. A Lagrange-multiplier technique is also used to optimize the quadtree for the adaptive block size.

We introduce a method for segmenting surfaces of threedimensional objects using two images of the object obtained from the same viewpoint under different illumination conditions. The method allows the surface spectral reflectance to vary from point to point and requires only weak conditions on the uncalibrated illumination configuration. The algorithm is based on the local recovery of an illumination change matrix that depends on surface geometry but not on the spectral reflectance of the surface. We show that for typical sensor noise levels, this technique can be used for the reliable detection of surface orientation changes of a few degrees. This approach can be generalized using a calibrated setup to recover a dense set of surface orientation estimates from two images. We present a set of experiments demonstrating the capability of the algorithm for the segmentation of planar surfaces in the presence of spatially varying spectral reflectance.

We report our study of a novel motion estimation algorithm based on structure segmentation and compensability analysis, where the macroblocks in the prediction frames are classified into four types corresponding to stationary background (or stationary objects), uncovered background (or new objects), moving objects, and edges among them. Then the following motion estimation operation is only performed on the compensable macroblocks, and the motion interaction among neighboring macroblocks is further used for reducing the search range. Preliminary results indicate that this proposed technique not only reduces the estimation burden drastically but also avoids the discontinuous change of picture quality, thus resulting in improvements of the subjective picture quality in comparison with a normal fast search algorithm.

We develop a theoretical model of image brightness variation of line-scan imaging systems using an ac-operated light source for object illumination. First, we derive an equation that relates the lamp operating frequency F, the object transport speed v , the image resolution R0 , and the number nc of lamp operating cycles within the time interval of one scan line. It is shown that nc=FlvR0=Ftexp , where t exp=1/vR0 is the exposure time of an image sensor element and is the time interval within one scan line. Following this, we define a normalized modulation function M(nc ) that relates to the variation ?E of the light energy E= ? I (t) dt received by a sensor element over t exp , where I(t ) is the intensity of object illumination. Three types of periodic functions for I(t ) are considered for which closed-form solutions for M(nc ) can be obtained: squarewave, sinusoidal, and triangular-wave. For the square-wave function we show that M(nc ) is a periodic function of nc , with zeros occurring at integral values of nc and peaks occurring at odd multiples of 1/2, with the heights of these peaks decreasing as 1/2nc with increasing nc . For the sinusoidal and triangular-wave functions, M(nc ) has similar periodic behavior except that the heights of the peaks decrease as 1/?nc and 1/4nc respectively. These results indicate that the square-wave function can be used to represent the worst case for assessing the performance of an imaging system under different conditions. Accordingly, we show numerically that lamps operating at a low frequency F=50 Hz cannot be used for object illumination because the variation in image brightness is too large, and lamps operating at F=20 kHz are generally applicable except at high object transport speed, typically at 100 in./s. Finally, we point out that this theoretical model may also be applied to area-scan imaging systems, such as for video cameras. For these imaging systems, the normalized modulation function can be used to assess the variation of image brightness between one whole image and another, rather than between one scan line and another.

Range Doppler imaging, a basic method used in inverse synthetic aperture radar (ISAR), is based on the uniform rotation model of a target. The rotation velocity and axis of a maneuvering aircraft often vary with time. Traditional imaging methods may blur the target image and even render it beyond recognition. A concept is presented for range- instantaneous Doppler imaging and a corresponding imaging method that can clearly improve the image quality of most maneuvering aircraft. The resulting images of real data show that the method is effective.

The optical character of electrorheological (ER) and electromagnetorheological (EMR) fluids under the influence of an external field are investigated. It is found that the transmission of ER fluids could be adjusted through selecting the proper electric field and suspension concentration. The IR spectral transmissions of ER fluids increase with an applied electric field. The maximum transmittance for low-concentration fluid changed from 4% to 23%. It is also observed that the window of transmission does not change with fluid consistency and external electric field. We find that the scattering patterns of ER fluids consist of the many bright and dark bands as a scattering grating. The widths of bright bands increase with increasing electric field. The scattering pattern of EMR fluids under electric and magnetic fields superimposed in the perpendicular is also observed. These phenomena provide new mechanics for the design of tunable optical devices and will have direct industrial application.

A new type of collimation testing technique using a single wedge plate in conjunction with a dual-field grating has been described. Interference pattern produced by a wedge plate illuminated by the test beam is superposed on a grating to get moire fringes. By using two different types of dual-field gratings, two testing configurations are obtained. These dual-field moire patterns provide self-referencing and improved sensitivity in collimation testing. The principle of the proposed techniques and experimental results are presented.

We describe a simple method to derive electronic speckle pattern interferometry (ESPI) fringes using compressed JPEG images from a digital still camera and a personal computer. We show that ESPI fringes of good quality can be obtained by this method. We show examples of ESPI fringes for thermal loading and for mechanical deformations of the test object.

The effects of low-frequency vibrations on speckle correlation fringes have been investigated. The relatively short capture time of the camera in the low-frequency case may yield usable fringe contrast in spite of vibration. It has been shown that the fringes also shift due to the vibration. The study is in agreement with experimental observations of good-contrast correlation fringes even if the object is not on a vibration- isolated table. Some such experimental observations are also presented.

A novel method of encoding a phase hologram that uses less than ? radians of phase is described. The technique is based on Lee's delayed sampling method for amplitude holograms. It was devised for use with liquid crystal spatial light modulators with limited phase modulation capability. Results are compared with Lee's method and binary phase holograms and show improved image quality.

Usually the quality of commercial LiNbO3 (LN) wafers is checked by their crystalline homogeneity. In X cut wafers, which are labeled for optical waveguide applications, however, the existence of a significant change in the hydroxyl content along the polarized Z axis is found by Fourier transform IR (FTIR) spectrometry, although a corresponding inhomogeneity was not observed about the lattice parameters, the Li and Nb contents, and the optical birefringence parameters. Such a difference in hydroxyl content might influence quality and stability of the obtained waveguides, and one should consider this before designing waveguide devices and fabrication processes.

It has been suggested that phased-array detection is a highly sensitive method of detecting and locating an inhomogeneity embedded within a scattering medium, e.g., a tumor embedded in breast tissue. No consideration has so far been given to the effects of noise within the system leading to detection errors. A probabilistic approach is used to find the optimum detector threshold and detection criteria. The technique is demonstrated using experimental data obtained from a novel phased- array system designed to eliminate noise due to amplitude fluctuations between the two sources. A brief comparison with single-beam frequency detection using the probabilistic method is also made.

The precision of sine-wave modulation transfer function (MTF) measurements of a color negative film was investigated at three laboratories within the Eastman Kodak Company. A spatial frequency range of 0.19 to 40.0 cycles/mm on Kodacolor Gold 100 film was employed for the measurements. The precision of the measurements at two of the laboratories was found to be equal, with the third set of measurements being less precise. The precision was measured by the standard deviation, at discrete frequencies, of replicate MTF measurements. This work may provide necessary supporting experimentation for an ANSI/ ISO color-negative-film MTF standard, which would enable meaningful comparisons of results between laboratories.

A heliostat is designed and built to track the sun for optical remote sensing of the stratosphere from a balloon-borne pointed gondola. The tracking mechanism is controlled by two direct torque motors used to drive a single flat acquisition mirror. A horizontal turntable, rigidly attached to the azimuth drive, supports the elevation assembly. A position sensor receiving a small part of the solar beam reflected off the main acquisition mirror is used for fine servo control. Using a CCD camera prepointing of the acquisition mirror is achieved when the sun is in the field of view of the heliostat. This system is coupled with a high- resolution (0.02-cm-1) Fourier transform IR (FTIR) spectrometer to retrieve stratospheric trace species concentration profiles. The suntracker directs the solar radiation in a stable direction along the spectrometer optical axis. The pointing precision is 1 arcmin from a stratospheric gondola, which has static and dynamic angular excursions up to 6 deg. The heliostat coupled to the Limb Profile Monitor of the Atmosphere (LPMA) instrument performs successfully on several balloon flights. The description, ground tests, and balloon flight results of the suntracker are presented.

This paper describes a noncontact laser sensor for pipe inner wall inspection using the circular optical cutting method. The sensor, consists principally of a laser diode light source, an optical ring pattern generator, and a CCD camera. The generator forms the light from the laser diode into a circular pattern to project on the pipe inner wall. The light reflected or scattered by the pipe inner surface is imaged on the CCD camera. It is possible to select the proper parameters by fundamental performance analysis and simulation according to the theory of light reflection and scattering. Experiments show that with the sensor mounted on an automated moving system, pipes of interior diameter between 80 and 140 mm can be inspected with resolution of 100 µm in radius. Analysis of the pipe interior wall surface using wavelet transforms is also described.

An optical fiber strain-rate sensor based on in-line Doppler velocimetry is developed using a 3 x3 coupler with a large path imbalance Mach-Zehnder interferometer for passive demodulation of Doppler wavelength shifts. A model is developed that relates the strain rate in an optical fiber to the corresponding Doppler wavelength shifts. The strain rate obtained by differentiating strain from a Michelson strain sensor mounted on the piezoelectric transistor (PZT) cylinder shows good agreement with the strain rate directly obtained from the Doppler-based strain-rate sensor. The Doppler-based strain-rate sensor is also bonded to a Hopkinson pressure bar in an attempt to detect the stress waves propagation. It is shown that the higher the strain rate of stress wave, the easier it is to couple into the lead-in/out fiber.