This PDF file contains the front matter associated with SPIE Proceedings Volume 8839, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

High resolution deformation measurement method which requires only two speckle patterns in fringe analysis is proposed. In fringe analysis based on proposed optical system for new method, a pair of real- and imaginary-part components concerning the deformation information can be extracted from one speckle pattern by Fourier transform. The real part is shifted on frequency domain in order to give the information of carrier fringes. Furthermore, the amplitude of the intensity distribution is normalized so that the amplitude becomes one. A specklegram is calculated as a fringe image by the shifted and the non-shifted real parts of information. The fringe image which includes the spatial carrier-information is analyzed by spatial fringe analysis method based on moiré fringe analysis. The accuracy of the deformation measurement is efficiently improved by using the spatial fringe analysis method and the normalization of the amplitude. It is confirmed that the method can analyze deformation process with a convex phase distribution in high resolution power.

This paper presents a thorough comparison between a phase-based and an intensity-based optimization method for 3D shape measurement with the binary dithering techniques. Since for a 3D shape measurement system utilizing digital fringe projection techniques, the phase quality ultimately determines the measurement quality, and thus these two methods are compared in phase domain. Both simulation and experiments find that the phase-based optimization method can generate high-quality phase under given conditions. However, this method is sensitive to the amount of blurring (or defocusing). On contrast, the intensity-based optimization method can consistently generate high-quality phase with various amounts of defocusing. Both experiments and simulations will be presented to compare these two optimization methods.

Many applications require a fine measurement to be made over a small area, but with reference to a much larger area. The ability to inspect a large surface, then to zoom in to a small area is valuable in many applications ranging from bridges to turbines. However, the need to switch lenses or re-point a lens can make such inspection cumbersome. This paper discusses an optical method that permits an instantaneous switch from a wide view to a close up of any area within that wide view, without the need to change lenses or repoint the optical system. We will discuss the possible application of the method, as well as the limitations inherent to the concept.

It is difficult in interferometric metrology to maintain high spatial resolution over a large measurement region. In this paper this characteristic is achieved by scanning two focused laser beams of about 6 microns diameter over an object surface and a reference mirror surface, respectively, with a rotating mirror, a lens, and a polarization beam splitter. An electric-optic phase modulator generates the phase difference of a sinusoidal waveform of 10 MHz between the two focused beams to calculate the phase of the interference signal. Because the beam focused onto a diffraction grating of 50 microns period is not diffracted strongly, a surface profile of the grating can be exactly measured by this interferometer over the measurement region of 16 mm with the spatial resolution of 2 microns.

We present a new device, the Diffractive Optics Calibrator (DOC), for measuring duty-cycle and etching depth for computer generated holograms (CGH). The system scans the CGH with a collimated laser beam, and collects the far field diffraction pattern with a CCD array. The relative intensities of the various orders of diffraction are used to fit the phase shift from etching and the duty cycle of the binary pattern. The system is capable of measuring variations that cause 1 nm PV phase errors in the wavefront created by the CGH. The measurements will be used primarily for quality control CGHs, but the data can also be used to provide a lookup table for corrections that allow calibration of the lithography errors. Such calibration may be necessary for us to achieve our goal of measuring freeform aspheric surfaces with 1 nm RMS accuracy.

Digital-light-processing (DLP) and liquid-crystal-on-silicon (LCOS) are two digital projection technologies which enjoy great popularity. This paper will demonstrate the performance of the two technologies in generating digital sinusoidal fringe patterns in the two following ways: focused-sinusoidal-patterns (FSP) method and defocused-binary-patterns (DBP) method. Experiment shows that for the FSP method, LCOS projector is a better choice since nonlinear gamma effect is less significant and there is no need for precise synchronization; While for the DBP method, DLP projector has the advantage over LCOS projector since the generated images have higher contrast ratio.

We report optical characterization of the different optical components fabricated in transparent materials by bulk refractive index modification or surface ablation by femtosecond pulses. The methods used for characterization of the components with refractive index modification fabricated in fused silica by high repetition rate femtosecond KGW:Yb laser were transmission and diffraction measurements at 532 and 632.8 nm wavelengths, and total integrated scattering (TIS) at 532 mn wavelength. The combined characterization methods were sufficient for modification process optimization and allowed creation of the Bragg gratings with diffraction efficiency in range from 55 to 90% and low scattering losses. The forward and backward TIS measurements of the radial polarization converter showed that forward scattering is more than five times as high as backward scattering. Solar cells with modified surface by femtosecond pulse ablation were investigated by TIS and Volt-Ampere measurements. The current increase is registered with growth of the scattering loses in the solar cells.

A pulse-modulated phase-shifting interferometer that employs two coaxial interferometers and an undersampling technique is proposed and demonstrated. The former improves the robustness of the optical system, while the latter makes it economical. Several measurements on flat and concave mirrors confirmed a measurement accuracy of ~18 nm.

Photoluminescence is one of the methods used for analyzing the optical characteristics of materials. For components in solid-state lighting such as GaN-based LEDs, the use of an LED structure configuration on a patterned sapphire substrate has shown to be highly effective in improving light-extraction efficiency. We proposed a compact and simple photoluminescence measurement system based on fiber-optic probes that can be scanned over a 20 × 20 μm² area with a high spatial resolution. We applied the system in morphological study of InGaN/GaN epitaxial layers for LED applications. With this system, we obtained peak intensity, peak wavelength, and full width at half maximum of the emission spectrum.

The Multi-frequency sweeping Fizeau-type interferometer (MFS-FI) for optical coherence tomography (OCT) is demonstrated. The multi-frequency sweeping by a variable Fabry-Perot filter permits detection of high-order low-coherence interferometric signals in the Fizeau interferometer. The sinusoidal phase modulation technique was utilized to detect accurate interference amplitude and phase distributions of back scattered light from surfaces of a sample. OCT measurements by the MFS-FI were conducted for vibrating glass plates with a frequency of 1 kHz, and cellular tissues fixed with formalin and embedded in paraffin. The tomographic 3-dimensional volume and cross-sectional surface displacements were detected with an accuracy of nano-meters.

Recently the demand and number of applications of full-field, optical measurement methods based on noncoherent light sources increased significantly. They include traditional image processing, thermovision, digital image correlation (DIC) and structured light methods. However, there are still numerous challenges connected with implementation of these methods to in-situ, long-term monitoring in industrial, civil engineering and cultural heritage applications, multimodal measurements of a variety of object features or simply adopting instruments to work in hard environmental conditions. In this paper we focus on 3D DIC method and present its enhancements concerning software modifications (new visualization methods and a method for automatic merging of data distributed in time) and hardware improvements. The modified 3D DIC system combined with infrared camera system is applied in many interesting cases: measurements of boiler drum during annealing and of pipelines in heat power stations and monitoring of different building steel struts at construction site and validation of numerical models of large building structures constructed of graded metal plate arches.

Characterization of a surface shape and finish has been vital for the manufacture of precision parts. Overall profile, surface finish and waviness of a part can be measured in two ways, contact and non-contact. In the contact method a stylus is dragged on the surface of a part to measure the profile and texture of the part for quantifying the surface characteristics. Non-contact methods applied z precision metrology include: microscopy, interferometry, chromatic confocal microscopy and laser profiling such as structured light methods. The chromatic confocal method offers flexibility because of its fiber optics probes that can be manipulated to accommodate many sample geometries. This flexibility provides a wide range of possible analysis dimensions such as cylindrical shapes of holes and the potential to provide both surface roughness and shape. This paper will discuss the setup and testing of a system specifically for measuring cylindrical shaped parts and present the performance of the technology as a precision metrology tool.

Gas electron multiplier (GEM) detectors are widely used in contemporary high-energy physics experiments. The GEM is a detector containing a densely pierced polymer foil, coated with a thin metal layer on one or both sides. They are able to achieve high amplification gains and performance at low cost, even under harsh radiation conditions. The holes in the foils have a nominal diameter of 70 ± 5 μm and 140 μm pitch distance between the centers of the holes. High-quality assurance is needed to guarantee a long lifespan for the detectors in the severe radiation environment. Mapping of the defects connecting two or more holes is important phase when determining the usability of a foil for detector application. The commercial optical scanning system (OSS) with a scanning area of 950 × 950 mm was further developed in the Detector Laboratory at Helsinki Institute of Physics for controlling the quality of GEM foils. Microfabricated transfer standard containing sets of 10 × 10 numbered etched cavities with a nominal diameter of 70 ± 5 μm was produced for system calibration. The cavity dimensions and the expanded uncertainty were calculated with the 95% confidence level, as is required by the ISO Guide for Expression of Uncertainty in Measurement. The transfer standard was examined with the OSS in nine different positions of the scanning area. The results were analyzed, the uncertainties were calculated and the corrections were made according to the ISO requirement.

The Brownian motion of particles close to the interface between air and liquid is investigated using the one-shot measurement of temporal autocorrelation functions as a function of the distance from the interface by using a spectraldomain low-coherence dynamic light scattering. The technique is based on the principle of spectral-domain optical coherence tomography combined with that of dynamic light scattering. It is experimentally found that Brownian motion is suppressed in the region close to the air-liquid interface, but increases consistently with distance from the liquid surface, until free Brownian motion occurs. The results confirm the potential of the proposed technique for metrological applications.

Our objective of this study is to develop a miniature and high accuracy automatic 3D blood vessel searching system, which will be introduced in the laparoscopic operation with the minimally invasive surgery. Now, the conventional optical system used in the laparoscopic surgery has many difficulties of blood vessel imaging and detection, because the peripheral bio-tissue located around the blood vessel disturbs the light wave propagation, disperses and refracts. Consequently, only unclear image is obtained. We develop a new blood vessel detecting system by using Near-Infrared (NIR) light, two CMOS camera modules and a comprehensive image processing technique, which is implemented in the laparoscope pipe with 25mm in diameter. We adopt the stereo method for the searching system to determine 3D blood vessel location. The blood vessel visualization system adopts hemoglobin’s absorption characteristics of the NIR light, which has high permeability for the bio-tissue and absorbency for the hemoglobin. A sharpening process is employed to improve the image quality of original ones, through the LoG filter and the un-sharp-mask processing. 2D location of the blood vessel is calculated from luminance distribution of the image and its depth is calculated by the stereo method. A validity of our blood vessel visualization and 3D detecting system was examined through the comparison with the imaging and detecting the results of organization phantoms, which embedded at known depths under the surface. Experimental results of depth obtained by our detecting system showed good agreements with the given depths, and the availability of this system is confirmed.

Recent advances in technology have enabled the acquisition of high-resolution 3D models in real-time though the use of structured light scanning techniques. While these advances are impressive, they require large amounts of computing power, thus being limited to using large desktop computers with high end CPUs and sometimes GPUs. This is undesirable in making high-resolution real-time 3D scanners ubiquitous in our mobile lives. To address this issue, this work describes and demonstrates a real-time 3D scanning system that is realized on a mobile device, namely a laptop computer, which can achieve speeds of 20fps 3D at a resolution of 640x480 per frame. By utilizing a graphics processing unit (GPU) as a multipurpose parallel processor, along with a parallel phase shifting technique, we are able to realize the entire 3D processing pipeline in parallel. To mitigate high speed camera transfer problems, which typically require a dedicated frame grabber, we make use of USB 3.0 along with direct memory access (DMA) to transfer camera images to the GPU. To demonstrate the effectiveness of the technique, we experiment with the scanner on both static geometry of a statue and dynamic geometry of a deforming material sample in front of the system.

This paper demonstrated a uni-axial inner profile measurement based on the shape from focus. The key device is a conical mirror and a variable focus lens. The shape of light beam is transformed from a point beam to a disk-like beam after passing through the variable focus lens and the conical mirror. The focus position of the disk-like beam can be controlled by electric current given to the variable focus lens. The beam is formed like a ring on the inner surface of the cylindrical sample. A CCD camera captures the ring as intensity distribution after the ring beam turn back to the way. The magnitudes of the intensity distribution are changed along focused positions of the ring beam. That is to say, the intensity distribution is described a Gaussian profile in the function of the electric current value. As this result, the radius distribution of the inner surface profile can be determined from the property of electric current of the variable focus lens. We have shown some experimental results as a coaxial inner profile measurement.

The paper presents a custom-designed laser triangulation based metrology system, which enables high precision surface displacement measurement of various material types with a single sensor configuration. Laser structuring applications require material surface alignment relative to the laser focus position where fabrication conditions are optimal. The measurement system utilizes a high-quality UV wavelength laser beam (primarily used for structuring purposes) with automatic control of its intensity. The laser source operates in a continuous wave (CW) mode during the measurement process, whereas the UV wavelength enables measurement of transparent materials. Robust displacement measurement of various material types was solved by introducing a new approach of structured light projection and its centroid detection. A high resolution 2D galvanometric scanning system is used for dynamic symmetrical pattern projection, which is proven to reduce the effects of material surface related errors and speckle noise. Furthermore, a “double curve fitting” (DCF) centroid detection algorithm, where Gaussian curves are fitted to radial cross sections of the acquired pattern, and an ellipse is fitted to their peak positions, was introduced. The method includes subsurface scattering compensation, which proves crucial for translucent material measurement, where incident light penetrates into the material surface and causes uneven light intensity distribution of the acquired pattern. Experimental results have shown that the metrology system is robust to laser intensity variation and material type, with measurement bias lower than 50 μm and standard deviation lower than ±6.3 μm for all materials. The developed probe has been integrated into commercial LPKF laser structuring systems.

The present work consists on the development of an adaptive control system to compensate the reduction of the contrast in interferograms caused by mechanical vibrations present in a Mirau based interference microscopy system. The control generates random signals that are injected during the integration time of the camera through a piezoelectric device in order to change the phase of the interferometer. Each obtained image has different control signals injected during the integration time. The contrast is evaluated and if the contrast is improved, the signal injected is adjusted to seek for a better improvement. The best signals collected are added to the control signal, which is applied to the system after the adaptation process is over. The control scheme implemented is capable of finding signals to compensate the main frequency noisy components of the system.

We proposed a three-dimensional (3-D) microscope with a magnification of 50X based on the principle of angle deviation microscopy for measuring the transparent materials. We utilized a parallel beam like uncountable probes to sense a specimen. After sensing, each light may be deflected a small angle due to the non-smooth surface or/and the change of refractive index. A parallelogram prism is used to acquiring all the deflective angles by measuring the reflectivity of prism based on the critical angle method. Thus, the surface height is proportional to the deflective angle and the reflectivity. Using two CCDs is to record the intensity patterns on conditions of TIR and the critical angle, respectively. The CCDs are located at the image planes, one is in the TIR path, and the other is in the critical angle path, respectively. Thus, the reflectivity pattern can be calculated and transformed into the 3-D surface profile. In our experiment, the lateral and vertical resolutions can be demonstrated within submicron and 1 nm, respectively.