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A new laser differential reflection-confocal lens thickness measurement (DRCTM) method is proposed for the high-accuracy measurement of the lens thickness. DRCTM uses the test beam reflected from the lens first and last surface to determine the vertex positions of the two surfaces. Differential confocal technology is used to precisely identify the lens vertexes of the lens first and last surfaces, thereby enabling the precise measurement of the lens thickness. Compared with the existing measurement methods, DRCTM has high accuracy and strong anti-interference capability. Theoretical analysis and experimental results indicate that the DRCTM measurement error can be limited to 0.0015%.

A new six-step phase shifting method is presented in this paper to determine the phase retardation for whole-field photoelastic stress analysis in optical glass based on the plane polariscope setup. This new phase stepping strategy is of no quarter wave plate errors and with less intensity variations of emerging light. By this method, it's not necessary to determine the isoclinic angles in advance when measuring the phase retardations, so the data processing will be simplified and the isoclinic angle errors will cause no influnces on the measurement. A plane polariscope is setup including a LED array light source, rotatable dichroic polymer film polarizer and analyser, a digital CCD camera and image grab system. Two mica waveplates with known phase retardances are measured, and the experimental results agree well with the those values. This method is expected to be used for the stress induced birefringence test in optical glass.

Critical dimension measurement based on scatterometry is expected to be the key technology in current and future semiconductor manufacturing processes. Scatterometry has strong dependence on modeling. The paper compares the Integral Equation Solver and the Rigorous Coupled Waveguide Analysis (RCWA) technique from convergence, and chooses the RCWA method to simulate the critical dimension measurement. The paper introduces an angle resolved scatterometry technology constructed on microscope. The back focal plane of a bright field reflection microscope contains diffraction information about the sample, and positions in the back focal plane map to diffraction angles from the sample. With suitable control of the angle of the incident illumination, back focal plane imaging can provide information similar to that obtained from angle resolved scatterometry. The paper simulates the reflectance of the rectangular grating at a fixed wavelength (λ=532nm) versus angle of incidence, measured for both s polarization and p polarization. The silicon gratings are 10nm difference with line width, pitch, line height and sidewall angle. The simulations reveal that the p polarization light is more sensitive than the s polarization light to the changes of the grating size, and the scatterfield microscopy has nanometer level sensitivity to the line width variations.

Due to the phasing effects, the measurements of Minimum Resolvable Temperature Difference (MRTD) for Staring array thermal imagers often get abnormal results when the targets approaching system Nyquist frequency (f n ). To simulate the relations between MRTD values and four-bar targets' frequencies, this paper introduces the concept of best contrast. Clearly, the MRTD results are inversely proportional to the best contrasts under optimum phases, higher contrast corresponding to a lower MRTD. On the other hand, with the spatial frequencies increasing, the target's opening area shrinking and leads the effective infrared eradiation decreasing, this means the MRTD results are inversely proportional to the opening area of the target. Based on these two assumptions, and through numerical simulations, this paper depicts the tendency chart of MRTD under optimum phases to the four-bar targets' spatial frequencies. The tendency chart adequately explains the hump curve happens at frequencies between 0.6f n and f n . From the simulations, the maximum of MRTD values can be predicted at the frequency of 0.89f n . The tendency chart illustrated by numerical simulation is consistent with the MRTD results get in laboratory. While in Dynamic Minimum Resolvable Temperature Difference (DMRTD) testing, moving the four-bar targets introduces temporal effects not present in static MRTD test. Simulation reveals that DMRTD test can get more realistic shape of the curve between 0.6f n and f n , the characteristic hump in the static MRTD curve between 0.6f n and f n is not seen.

Due to the imperfectness of the reference wavefront produced by standard lens, the spherical figure measurement precision of the traditional interferometer is limited. The fiber point diffraction interferometer (FPDI) provides a method to produce the nearly perfect reference wavefront for the spherical figure measurement. The diverging wavefront diffracting from the fiber tip can serve as an ideal reference for the concave spherical surface measurement. However, it can not serve for the convex surface measurement until an auxiliary positive lens is introduced. This paper presents the different FPDI configurations for the concave and convex spherical surface measurement. The measurement uncertainty of the FPDI comes from the following factors: the spherical figure error of the reference wavefront diffracting from the fiber tips; the flatness of the fiber tips; the phase shifting error of PZT; the tilting error introduced by adjustment during measurement; the environmental influences such as temperature, vibration, and air turbulence. In all of these factors, the flatness of the fiber tips mostly affects the measurement uncertainty. The estimation of the expanded uncertainty is about λ/95 for the concave and λ/40 (λ=532nm) for the convex spherical figure measurement by FPDI.

The point diffraction interferometer (PDI) is the technology which realizes the absolute interferometric measurement without the use of reference surface. Pinhole is mostly used to generate the ideal spherical wavefront traditionally. While using the single mode optical fiber instead of pinhole can easily introduce phase-shifting ability for PDI measurement. This paper mainly discusses the merits and disadvantages of two kinds of fiber phase shifting point diffraction interferometer (FPS/PDI). Two fibers FPS/PDI is a separated-path configuration. Although it's easy to adjust, it's more sensitive to environment influence, and the thickness of fiber cladding will induce an off-axis error during measurement. Single fiber FPS/PDI is a common-path configuration, thus it is robuster than the front, but the maximum visibility is now one half. Its accuracy is mainly affected by factors such as the fiber core diameter, slight ellipticity and oblique face. The paper lastly compares the single fiber PDI with ZYGO interferometer based on measurement data about a sphere surface, the single interference pattern collected by our experimental fiber PDI apparatus is analyzed and the major error sources are also discussed.

The primary restriction on the precision of spherical figure measurement is the imperfectness of the reference spherical wavefront. Using the nearly perfect spherical wavefront diffracting from a single mode fiber as the reference, the accuracy of spherical figure measurement can be greatly improved. To get good contrast of interference fringe, the extraneous interference should be eliminated, and the intensity of the reference beam must match to the measuring beam at the same time. Using the short coherence length laser source can avoid most of the extraneous interference. The principles through stretching the resonant cavity length to shorten the coherence length are discussed; the effects are validated by constructing a Twymann-Green interferometer using the cavity length tunable YAG solid state laser. Calculations on light intensity show that only through controlling the attenuation of the measuring beam, can it match to the reference beam. Coating the fiber tips with semi-metallic film can substantially improve the contrast of the interference fringe. Comparing to the measurement results of ZYGO interferometer, the single interference pattern collected by our experimental fiber PDI apparatus is analyzed and the major error sources are also discussed.

The Log Amplifier described in this paper is designed for hearing aids (HA) application. It works on a low single-supply voltage (1.3V). The input signal varies between 0.01mV and 100mV. To give enough compensation to the hearing impairment, the amplifier provides a very large gain. The output swing is limited because of the low supply voltage and the large gain. Therefore, the logarithmic amplifier introduced into the design of HA to compress input signal so that the output distortion can be avoid. Another factor we use it here is that the amplifier has enough sensitivity and gain to deal with the compressed input signal without getting extra distortion coursed by the pre-process on input signal. The short channel CMOS devices play an important role in reduction of the supply voltage. DONG-BU ANAM 0.18 μm process is selected.

This paper presents a new idea of Epipolar Slope. There are some feature points, e.g. the inflection point, on the epipolar line or curve. The homonymous points can be discovered in a couple images, and Feature Matching can be achieved as visible measurement. The Improved Hough Transform has been discussed in this paper because the standard quadratic curve may be discovered by the Improved Hough Transform as the pre-process of the Feature Matching.