During the past few years that I have served on the Board of Directors of SPIE, it has become clear that the word ‘‘International’’ in our name has taken on increasing importance. From what began as a society of American engineers doing high-altitude photography,

One of the main features of modern cameras is their ability to perform a mechanical autofocus and capture a sharp image. Experimental results for misfocusing corrections by fast and exact numerical postprocessing algorithms are presented. Furthermore, the optical transfer function (OTF) for a defocused circular pupil with an arbitrary diameter is presented. These methods are based on the wave optics and, thus, are more realistic than ray optics based methods.

A new optical design technique for catadioptric imaging optics is described, that permits near-zero values for the classical Seidel aberrations at relative apertures faster than f/1, with field angles over 3 deg arc, ~ 106 resolved pixels, a 600-nm bandwidth in the visible and near infrared and zero vignetting. Performance is limited only by high-order aberrations. The principle is that of combining the concentricities of a spherical concentric catoptric and a spherical concentric catadioptric, by optical superposition of the centers of curvature. The only full-aperture component is a spherical mirror; all other surfaces are spherical, except for an optional small weak zonal corrector. The new design approach is suited to aperture diameters of ~ 100 mm to > 1m when used with appropriate electronic detectors. Variants are possible for any segment of the electromagnetic spectrum for which there are suitable refractive and reflective media. In general, a large improvement in data acquisition rate is possible compared to that of existing designs.

Conventional confocal microscopes are based on the dual scanning of a specimen by the images of a point source and of a point detector. Hence, their imaging mode is serial, i.e., the confocal image is obtained from the sequence of single-point or multiple-point partial images. Parallel-mode confocal imaging is possible on the basis of broad- source image-plane holography. We adapted this classical holography technique for real-time reflected-light microscopy. The imaging speed of the parallel-mode confocal microscope is not limited by any part of the optical system, but only by the image detection and storage systems. Both the image phase and the image amplitude are reconstructed from the interference signal. We verify both theoretically and experimentally that the main imaging parameters of the microscope are comparable with those of a conventional confocal microscope. The only exception is the imaging speed, which can be much higher.

A compact and low-cost device that emulates a 100-km single-mode fiber optic link at 1550 nm is proposed. The device, composed of a chirped fiber grating and a monitor coupler, is analyzed by simulation and experimentally proved. A chirped fiber grating synthesis procedure is also introduced.

Tapering of fused silica optical fiber using a carbon dioxide (CO2) laser as the heating source is analyzed taking into account a Gaussian profile for the laser power distribution. The differential thermal equation is solved numerically using an implicit Crank-Nicolson finite difference method. The interaction of the CO2 laser electromagnetic (EM) radiation with the optical fiber is treated using Mie theory following the approach of plane-wave light scattering from thin rods. The fiber surface temperature is studied as a function of fiber diameter and laser power. The effect of different EM polarizations (parallel and perpendicular to the fiber axis) on the fiber temperature is also investigated. The final taper diameter values predicted by the present model are compared with experimentally acquired data. The analysis shows that to achieve final taper diameters of the order of 20 mm laser powers in excess of 25 W are required.

The work done to provide image sensors (CCDs and CMOS) with a wide dynamic range is reviewed. The different classes of solutions, which consist of logarithmic sensors, "clipped" sensors, multimode sensors, frequency-based sensors, and sensors with control over integration time are described. The pros and cons of each solution are discussed, and some new experimental results are shown. Active pixel sensors with a wide dynamic range are analyzed and possible future directions are pointed out.

We develop high-spectral-resolution lidar (HSRL) using an iodine absorption filter and a narrow-band Nd:YAG laser with high- frequency-doubled output and use it for atmospheric measurements at the National Institute for Environmental Studies (NIES). The lidar system separates Doppler-broadened molecular scattering and unbroadened aerosol scattering components of the backscattered laser light, consequently providing direct measurements of these two signals. Due to stable and strong absorption at room temperature, iodine absorption filters are easy to use and they enable high rejection against aerosol scattering with a short length. The measurement principle with an error analysis and the system construction of the HSRL are described. Examples of aerosol and cloud observations made by the HSRL are also presented. The experimental results indicate that the HSRL is a powerful tool for quantitatively measuring aerosol and cloud optical properties. The use of a high-output laser gives our system the ability to provide stratospheric observations. We also present the HSRL measurements of the stratospheric temperature and backscatter profiles with better resolutions in both range and time. An example of temperature and backscatter measurements is shown for the altitude range from ~`10 to ~40 km with a vertical resolution of 300 m and an integrated time of ~2 h.

The image quality of color liquid crystal displays (LCDs) are evaluated by measuring the modulation transfer function (MTF). The measurement system is constructed with a linear charge coupled device (CCD) and the spectral response is corrected with a V(?) filter for the human eye. The scanning width of a white dot is determined by considering the characteristics of LCDs. The MTF of the LCDs are measured at five positions on the screen as well as different combinations of contrast and brightness levels. The results are presented and discussed. We show that the MTF measuring method is very useful to evaluate the image quality of color LCDs.

A superluminescent diode interferometer that uses sinusoidal phase-modulating interferometry and the shifting method is applied to measure the front and rear surface profiles of a glass plate with an accuracy of a few nanometers. Since the roughness of the reference surface is large, a glass plate is put behind the object as another reference surface, which is estimated by the shifting method with an accuracy of a few nanometers.

All commercial paper types have a more or less apparent periodic pattern, called wire mark. We show how a Fourier optic analysis of this pattern can be used for on-line measurement of the dimensional variations of the paper in a paper or printing machine operating at a realistic speed (10 to 20 m/s). The way in which motion blur should be avoided during the exposure of the spatial light modulator, required to transform a spatially incoherent image of the paper into a coherent one, is also studied. Three techniques for doing this are discussed: rotating prism, rotating mirror and inverse filtering.

Wrinkling is one of the most important fabric performance properties, which are routinely evaluated in reference to a set of visual standards in the textile industry. The visual evaluation is unreliable and time-inefficient. An industrial need for objective and automatic evaluation methods has been increasing markedly in the recent years. An image analysis system is developed to meet this need. The laser line triangulation method is used to measure the 3D surface data of a wrinkled fabric, and a neural network is built to execute the wrinkle classification with respect to the visual standard. Due to the directionality of wrinkles, a rotary stage is used to change the sample's orientation under the camera so that multiple images of the sample can be captured at different angles and more wrinkle data can be extracted for classification. The wrinkle classifications provided by the system are highly consistent with the visual standards, showing the potential for replacing human graders in fabric wrinkling evaluations.

Optical pattern recognition and classification are commonly implemented by means of correlation, and a specialized filter for the patterns to be recognized must be constructed first. Although it has the inherent advantages of high speed, shift invariance, and high distin- guishability, how to build an effective and easily implemented filter or group of filters still remains an open problem. By combining the methods of correlation filtering, transform encoding, and neural network mapping, a least substructuring elements (LSE) extracting method is proposed in this paper. Some basic substructuring elements of a specific group of patterns to be processed could be extracted to compose masks in the least number. Computer simulation upon the 26 English capital letters is provided. One integrated hybrid optoelectronic implementation system is described.

An analysis of an optical current transducer (OCT) considering in particular the influence of temperature induced variations in the Verdet constant is presented. The analysis is supported by an experimental evaluation of a prototype OCT over a range of operating temperatures and current values and concludes with a laboratory demonstration of a temperature compensation scheme that improves the measurement precision to better than 0.7%.

Details are presented on a technique for compensation of vibration-induced noise in an optical current transducer (OCT). The light intensity changes that result from vibration are reciprocal, i.e., their magnitude does not depend on the direction of light propagation. However, intensity changes that result from the Faraday rotation induced as the light travels through the OCT are dependent on the direction of propagation and hence, by using two counter-propagating beams, vibration- induced intensity noise can be canceled by applying simple signal processing. This solution also enables true dc current measurement to be made. The principles of operation of the compensation method an experimental evaluation of the system are presented and the limitations associated with the compensation scheme are discussed.

An optical sensor for determining the proportional composition of two liquids in a mixture is developed. It is based on observing changes in the reflected light intensity at the glass-mixture interface brought about by the changes in the proportion of one liquid over that of the other in the mixture. Sample mixtures for this investigation here have been prepared by changing the concentration of substances such as kerosene and diesel fuel in a fixed volume of petrol. A procedure for identifying as well as evaluating the concentration of kerosene or of diesel fuel or of a mixture of the two in a sample of petrol has been reported. Evaporation of these sample mixtures is carried out by exposing them to a constant flow of air at the same temperature as that of the sample mixtures. Experimental determination of the changes in the reflected intensity are carried out by using an arrangement in which one of the two isosceles surfaces of a right-angled isosceles prism is interfaced with the sample mixture. Experimentally determined values for some of these changes are compared with the theoretical estimates for them obtained from Fresnel's equation.

A modified reciprocal reflection interferometer (MRRI) is proposed for vibration insensitive optical fiber current sensors (OFCSs). The verifications of experiments are in good agreement with our theoretical analyses. A large vibrational perturbation applied to a segment of lead fiber to simulate the disturbance to the OFCS can be suppressed over 20 dB compared with a conventional reciprocal reflection interferometer (RRI). The noise floor of the OFCS with an MRRI under perturbations is about 1.36 Armsturns/Hz1/2 near the shot noise limit. A good linear demodulation result is obtained and the evaluation of the Verdet constant 1.1?rad/Arms turns approximates the literatural data measured in static environment.

A reticle for the verification of the correct operation of the phase Doppler particle analyzer (PDPA) is presented. As an alternative to common calibration devices such as a droplet generator or reticles, we introduce a new reticle that consists of a single polymer microlens affixed to a glass substrate. The microlens reticle, when placed in the measurement volume of the PDPA, scatters light in a manner similar to that of a droplet. We report on results from tests performed using three microlens reticles of the same diameter and two models of the PDPA.

The characterization of electro-optical system performance by means of the standard minimum resolvable temperature difference (MRTD) or the minimum resolvable contrast (MRC) has a number of serious disadvantages. One of the problems is that they depend on the subjective decision criterion of the observer. We present an improved measurement procedure in which the results are free from observer bias. In an adaptive two-alternative forced-choice (2AFC) procedure, both the standard four-bar pattern and a five-bar reference pattern of the same size and contrast are presented consecutively in random order. The observer decides which of the two presentations contains the four-bar pattern. Misjudgments are made if the bars cannot be resolved or are distorted by sampling. The procedure converges to the contrast at which 75% of the observer responses are correct. The reliability of the responses is tested statistically. Curves cut off near the Nyquist frequency, so that it is not necessary to artificially set a frequency limit for sampling array cameras. The procedure enables better and easier measurement, yields more stable results than the standard procedure, and avoids disputes between different measuring teams. The presented procedure is a "quick fix'' solution for some of the problems with the MRTD and MRC, and is recommended as long as bar patterns are used as the stimulus. A new and fundamentally better method to characterize electro-optical system performance, called the triangle orientation discrimination threshold (TOD) was recently proposed by Bijl and Valeton (1998).

The role of a wedge prism for strain sign determination and to enhance the sensitivity for subfringe changes is presented. The design and incorporation aspects for in-plane sensitive interferometers are described in detail. Some experimental results dealing with stress determination by laser annealing and speckle correlation interferometry are presented. The prism can also be applied to produce standardized carrier fringes in spatial phase shifting interferometry.

We present a technique for enhancing the resolution of a twodimensional detector by processing images that have been subsequently acquired shifted by a fraction of a pixel with respect to each other. Possible limitations due to the intrinsic spectral broadening of the actual signals and to sources of error in the procedure have been analyzed. The results prove that the reconstruction algorithm is insensitive to high uncertainties in the relative subpixel displacements of the single images and to a low signal-to-noise ratio. Experimental tests have been performed with a detector with pixel size 25x25 ?m2. Images of fine wire mesh grids with periods 100 and 50 ?m and of a 10-?m-wide slit are presented. The reconstructed images show improved resolution of the profiles of the targets corresponding to 1/4-pixel sampling.

An optical Kerr gate with the capability of light amplification and a femtosecond opening time in a special fast setup is applied to time-resolved imaging. Transient-induced anisotropy created by a first pump pulse is canceled by the perpendicular-induced anisotropy created by a delayed pump. The transverse resolution of the image is better than 70 ?m without degradation due to the optical Kerr effect or optical amplification. Moreover, the rather wide spectral band of the gate offers the possibility of spectroscopic imaging. Three-dimensional imaging of small-signal objects using the gate are demonstrated for several types of transmitting objects hidden behind light diffusers.

Recently I encountered two remote sensing problems that required an estimate of direct lunar radiance at thermal IR wavelengths. One was the calculation of signal levels for atmospheric absorption spectroscopy using the moon as a source,1,2 and the other was the determination of the effect that moon glints have on IR polarization radiometry of water surfaces.3