The two micron all sky survey (2MASS) project, currently underway, requires a camera mated to a 1.3 meter Cassegrain telescope that will simultaneously image the J, H and Ks spectral bands onto three separate NICMOS3 HgCdTe detector arrays. Dichroic beamsplitters allow the three FPAs to view the same field simultaneously. This paper reviews the development of this camera, presents a detailed analysis of the optical design, and discusses the techniques used to align the instrument and evaluate its performance. The low irradiance of astronomical sources, combined with background limited performance of the detectors, mandated a reimaging configuration and the enclosure of the camera optics within the cold volume. Correcting chromatic aberrations, and minimizing ghost images were additional challenges imposed by program requirements. The key to achieving high performance was found to be the selection of lens materials. The final F/3.5 optical design uses fifteen CaF₂ elements and four Infrasil elements in an all-spherical configuration. The design is diffraction limited over the full format in the Ks spectral band, and is nearly so in the J and H bands. The tolerance environment is benign, making the design well suited for use in a cryogenic environment. A single channel prototype has been built and extensively field tested at the 50-inch telescope at Kitt Peak National Observatory. Each channel in the multi-spectral camera uses the same optical design successfully demonstrated in the prototype. Currently, the first of two three-channel cameras is undergoing lab tests for image quality and channel registration.

The Ball Aerospace & Technologies Corporation and Southwest Research Institute have built a three mirror anastigmat telescope as a proof-of-concept, working model of the visible camera system for the highly integrated Pluto payload system (HIPPS) intended for use on the Pluto Express mission. This instrument is unique due to its small size, light weight (less than 2.5 kg) and bolt together design. The all aluminum construction allows the unit to operate over a wide temperature range. The system was designed to have a 5.8 by 0.2 degree field of view, 650 mm effective focal length, 75 mm diameter entrance pupil and a 26 micrometer spot size. The initial version of this telescope utilized diamond turned aluminum mirrors due to cost and schedule limitations. The scattering and imaging properties of this telescope were evaluated. A baffle system was designed and installed to reduce stray light in the system. To improve system performance, the mirrors were resurfaced with electroless nickel, diamond turned and post polished. The stray light performance of the system before and after resurfacing the optics is discussed. Future performance testing plans for this system are presented.

High performance infrared optical designs require careful tolerancing to ensure that the as built performance meets the system requirements. Using modern optical design programs a wide vareity of single element and group tolerances can be defined and statistical analysis employed to formulate a prediction of the as built performance. When the number of units being produced is small or near diffraction limited performance is required, then a worst case analysis is often employed to generate a more accurate prediction. However, in some situations, such as low F/number lenses, certain effects that may be important are not always adequately addressed by first order tolerance analysis. This paper reviews one such effect; zonal irregularity or slope errors. To quantify the impact of zonal irregularity on the MTF performance of an infrared lens, detailed comparisons are made between measured and predicted performance. Interferometric analysis of the lens element irregularity is incorporated within the design to predict the as built lens line spread function.

The far ultraviolet spectroscopic explorer (FUSE) satellite will make high spectral resolution ((lambda) /(Delta) (lambda) equal 30,000) measurements in the 905 - 1195 angstrom bandpass from low-earth orbit. The optical system of the instrument consists of four coaligned telescopes and gratings, which disperse their spectra onto two detectors; both the mirrors and slit assemblies will be adjustable in flight. Because of this complicated, coupled optical system, it is important to understand all of the effects which may affect performance. The ability of the FUSE instrument to maintain its high resolving power and effective area is dependent on many factors, including the optical design, manufacturing errors, the ability to coalign the system on orbit, and the stability of the structure holding the optical elements. In order to predict the on-orbit performance, a detailed optical performance budget has been developed. This budget includes all effects which affect the resolution and throughput. Included are short term effects (such as the stability of the metering structure due to thermal variations during a single orbit); long term effects (such as moisture desorption from the graphite/cyanate ester structure and gravity release); and installation tolerances. We present the results of this exercise, and describe the dependence of the instrument performance on the expected errors.

This paper presents an optical principle based on four right angle prisms with an optional intermediate lens that allows a large aperture combined with a large field of regard. The optics can be fitted into a small volume and the major part of the thermal imager is placed off-gimbal.

Due to mechanical aspects of fabrication, launch, and operational environment, space telescope optics can suffer from unforseen aberrations, detracting from their intended diffraction-limited performance goals. Presented here are the results of a simulation study designed to explore how wavefront aberration information could be used in post- processing to improve the effective resolution of such telescopes. Knowledge of the telescope pupil aberration can be effectively used in a post-processing paradigm referred to as deconvolution from wavefront sensing (DWFS). Simulation results show that even when relatively noisy wavefront sensor information is used on images experiencing up to 10% of a wave root-mean-squared (RMS) of unspecified wavefront error, the signal-to-noise ratios (SNRs) of the optical transfer function (OTF) can be increased by a factor of 1.5, and RMS OTF phasor angle errors can be approximately cut in half, across a wide range of spatial frequencies. Post-processing consisted of correction of the Fourier phase of the image spectra using information from wavefront sensing, without the use of inverse filtering or adaptive optics compensation.

We have developed a scanning near-field infrared microscope (SNIM) that utilizes the Stanford picosecond free electron laser as its illumination source. Infrared spectroscopy is a sensitive technique for characterizing materials. However, the spatial resolution of conventional infrared microscopy is limited to a few micrometers due to diffraction. The SNIM overcomes this limitation by using infrared near-field optics to obtain sub-wavelength resolution. The system is built around a near-field scanning optical microscope (NSOM) head, in which a tapered infrared transmitting fiber is mounted as the scanning probe. The Stanford picosecond free electron laser, which provides high power infrared radiation with a wavelength that is continuously tunable from 3 to 15 micrometers, is then coupled to the fiber. In combination with the FEL, the SNIM can obtain infrared spectra of localized regions smaller than one micrometer and acquire images at a chosen wavelength with sub-micrometer resolution. The most promising aspect of SNIM is in the development of 'vibrational nanospectroscopy.' Images have been obtained of biological tissue such as kidney sections using the intrinsic amide absorption in the tissue proteins to provide contrast, instead of relying on an externally introduce stain or marker. Images of lithographically patterned semiconductor samples have also been obtained, revealing subsurface features in gallium arsenide.

A reflected-light confocal scanning optical microscope with circular scan line is described. For the horizontal scanning, the instrument uses a rotating dispersive prism embedded at the tip of a hollow motor shaft. The rotating hollow motor shaft accepts a polarized collimated laser beam and transforms it into a rotating beam, with a cone-shaped trajectory, on its exit from the prism. The rotating beam then passes through an inverted telescope and a quarter-wave plate before it is focused onto the specimen plane by a conventional microscope objective. To improve upon the ranging accuracy, a telecentric scan is maintained throughout the scan. The reflected light travels back through the same components until it is redirected by a beam splitter to pass through an analyzer and a pinhole before arriving at the detector. The use of the same optics for both illumination and imaging automatically satisfies the confocal requirement, and eliminates the need for a synchronizing mechanism. Also, the use of a rotating prism renders the system completely insensitive (for all practical purposes) to motor wobble.

The optical system of an optical rotary encoder is presented. The requirements of the optics system are given and their effects on optical design decisions are discussed. Steps taken to insure stable operation over aa minus 40 degree Celsius to plus 85 degree Celsius temperature range are presented. Designing for manufacturing tolerances is discussed. A novel application of a fiber illuminator LED as a short-distance collimated source is shown to be an acceptable low-cost alternative to a laser diode. The importance of effective plastic element employment in low- cost, mass-production optical systems is demonstrated.

The present work delineates the principles of a direct vision color image intensifier tube. An arrangement consisting of microchannel tube in conjunction with input color filters mosaic and matched output color filters mosaic is described. It is shown that color imaging can be achieved at very low light levels with acceptable color resolution. The present work is aimed at describing the basic theoretical model for simulation and analysis of color imaging tubes including quantification and optimization of its performance. The basic model incudes the major color tube components and operating parameters, namely, spectral characteristics of the RGB basic color filter's elements, its diameter and center-to-center spacing; spectral characteristic of the photocathode and phosphor; MCP's pore size, center-to-center spacing and gain; voltages and spacing between electrodes; tolerance of registration of input-output filters, etc. For a number of technologically achievable parameters it is shown that: (1) the resolution of the device, based on the Nyquist frequency, can reach 16 color (line pairs)/mm; (2) the light uniformity is about 5% which is insignificant; (3) realistic set of filters provides a good color transformation -- compatible to the transformation in color CRT displays; (4) cross-talk level in single basic color element from neighboring elements is about 6%; (5) the light amplification is compatible to conventional intensifier tubes; (6) the proposed configuration is not too sensitive to design parameters. It is possible to conclude that realistic configurations can produce a color direct vision image intensifier device with high resolution and good color transformation. The device simulations serve to design a workable prototype.

The development of the ability to routinely 'machine' glass materials to optical tolerances is highly desirable and, in particular, could provide new degrees of control over the precise shape of complex and unusual optical surfaces. Of particular interest in this regard is the formation of non- spherical shapes where there is a need to fabricate both inexpensive, low-precision optics as well as specialized high-precision aspheric components. This work describes the initial feasibility tests of the machining of a new type of glass, lead indium phosphate (LIP), a material which transmits from the visible to 2.8 micrometer (for thin samples). Glossy surfaces were produced with a root-mean- square surface roughness of less than 100 nm (with 200 micrometer filter). The results indicate that this approach offers the potential for producing high-quality aspheric optical shapes based on the use of LIP glass.

The fabrication of microlenses on flat and three-dimensional substrates is described. A totally dry resist process is used. The characteristics of this novel process are investigated. A technique for lens positioning and exposure was developed for a scanning electron microscope using an image processor as a beam control system. The hyperbolic profile of the microlenses is computer generated. Microlenses of cylindrical, round, and elliptical geometry were fabricated on a Si wafer and on the end of a monomode quartz fiber. Focusing of infrared light by fabricated microlenses is demonstrated.

This paper describes the process used to verify that the mounts designed for the STIS and COSTAR program would perform as designed. The optics on these two programs were all fabricated to (lambda) /100 rms surface figure. Some of the optics were bonded into mounts and others were mechanically mounted. All the mounts were designed to impart less than 0.005 (lambda) rms additional distortion with a goal of 0.003 (lambda) rms. A series of tests showed that the mounts performed as designed. Stability, thermal performance, contamination, and survivability were also tested.

A special surface geometry of diffractive Fresnel-lenses, which is well adapted to the Cartesian working regime of most microlithographic machines is presented in this paper. Due to this adaptation the amount of data necessary for the description of the exposure and also the exposure-time decreases drastically and so the realization of large area diffractive lenses and lens-arrays became possible. In this paper we compare the modified lens-geometry with the common radially symmetrical diffractive Fresnel-lens and we show some experimental results which we obtained for a lens realized by electron-beam lithography.

The optical design, test, and fabrication of a large ultra lightweight flat beryllium scan mirror is reported. The mirror is a key component for the (TIR) thermal infrared radiometer instrument which is scheduled to compliment the (EOS) Earth observation satellite program. The unique optical design properties of the mirror provide state of the art performance for scan operations and thermal imaging of the earth's surface in the 8.0 to 12.0 micron wavelength range. The mirror's opto-mechanical design provides a very stable non-deformed platform for the scan drive system. The mirror's optical figure, surface characteristics and protected gold coating have been tested and are well within the flight specifications.

This paper describes the process and methods to bond the corrective optics space telescope axial replacement and space telescope imaging spectrograph optics to their mounts. The optics on the two programs were all fabricated to .01 waves rms surface figure. These high quality optics for the Hubble Space Telescope required extreme care to mount. Since they must operate down to 1200 angstroms, contamination and minimizing surface distortion were serious concerns. The process produced excellent results. No significant surface distortion or contamination was induced.

For composite media some recent phenomenological approaches to treating dielectric properties in the long-wavelength limit are considered. Among the problems discussed are the features of media with close-packed particles, role of topology and bounds for the effective dielectric function. As an example, we consider close packing of submicron TiO₂ particles. An analysis of the near-normal reflection spectra is made. Using the Kramers-Kronig relation and the modified Avary method, we obtained a composite dielectric function in far IR. When modeling the dielectric properties of the system studied, we used Bergman's representation.

A prism fingerprint sensor is described which uses a holographic grating glued to a right angled prism. The quality of the fingerprint is very good; the pores on the ridges can be seen.

A Finnish-French group has proposed an imaging spectrometer- based instrument for the ENVISAT Earth observation satellite of ESA, which yields a global mapping of the vertical profile of ozone and other related atmospheric gases. The GOMOS instrument works by measuring the UV-visible spectrum of a star that is occulting behind the Earth's atmosphere. The prime contractor of GOMOS is Matra Marconi Space France. The focal plane optics are designed and manufactured by Spacebel Instrumentation S.A. and the holographic grating by Jobin-Yvon. VTT Automation, Measurement Technology has participated in the GOMOS studies since 1989 and is presently responsible for the verification tests of the imaging quality and opto-mechanical interfaces of the holographic imaging grating of GOMOS. The UVIS spectrometer of GOMOS consists of a holographic, aberration corrected grating and of a CCD detector. The alignment of the holographic grating needs as an input very accurate knowledge of the mechanical interfaces. VTT Automation has designed, built and tested a characterization system for the holographic grating. This system combines the accurate optical imaging measurements with the absolute knowledge of the geometrical parameters at the accuracy of plus or minus 10 micrometers which makes the system unique. The developed system has been used for two breadboard gratings and the qualification model grating. The imaging quality results and their analysis together with alignment procedure utilizing of the knowledge of mechanical interfaces is described.

E-beam lithography offers the possibility for fabricating metallic subwavelength gratings for visible light which show strong polarization properties. By using such gratings and other micro-optical elements (like lenses and diffraction gratings) a new kind of polarization detector without mechanical motion is proposed. The basic idea is the use of a special analyzing grating element with different grating directions (e.g. a circular metallic subwavelength grating). We realized both a wavelength-independent polarimeter and a polarimeter with spectroscopic properties. Characteristic parameters estimated are the angular resolution of the polarization plane (best value 0.001 degree) and the wavelength resolution (best value 15 nm).

Highly efficient diffractive grating based on doped photorefractive crystal sillenite family have been observed without application of external electric field. The diffractive efficiency of the doped crystal is discovered 700 times as much as that of the undoped crystals. The space frequency greater than 11363 lines/mm and response time of 70 msec using low power cw laser have been achieved. Practically unlimited number of grating cycles of write, erase and read have been performed without optical damage and external electric or temperature fields. High adaptivity (self-reconstruction) of this grating to external influence fields (vibration, temperature, electric, optic, etc.) allows creation of a new optical development of small size diffractive dynamic elements -- DDE in contemporary optical engineering. Applications of DDE to microinterferometry, single beam microcorrelators, precision targeting have been presented.

An optical method for the determination of high spatial frequency grating profiles with visible light is presented. The theoretical background is the effective medium theory. By using an optical surface profiler, the change of the surface height in the grating region is measured in two different ways. The results can be used to determine the duty cycle and the groove depth in the case of a binary grating profile.

The concave diffraction grating is both the dispersive and the focusing element at the same time. It can be the only optical unit of monochromator or polychromator. Using the concave diffraction gratings with nonequidistant and curved grooves gives the possibility for correction of the aberrations in the useful region of spectrum and provides the devices with determined focal surfaces. To increase the height of the entrance slit of the spectroscopic device we have to eliminate the first and the second-order astigmatism aberrations. Consideration of this type of aberration is very important now in view of the new types of spectral devices using fiber optics and multielement detectors being developed. These new elements allow us to register the spectrum of extended objects or a number of spectrums simultaneously. For the case of the double monochromator we noticed, that the second-order astigmatism can be completely eliminated if the second part of the double monochromator is equivalent to its first part, but the ray tracing is inverse. The experiment on the mathematical model of the double monochromator confirms this idea. For the case of polychromator or CCD spectrometer we can compensate that aberrations using the illumination system, consists of the spherical mirror. The angle of incidence of the light to the mirror is calculated such a way, that the astigmatism of the grating is compensated by the astigmatism of the mirror.

The design of a compact contact microscope, which can be used in-vivo to study the cataracts in human eyes is presented. This microscope has the capability to evaluate the changes in the optical density within the eye lens itself, and thus enabling an examiner to ascertain the progression of a cataractous change or at least the optical changes associated with cataractous development. The microscope has a variable focal length so it can be focused at any depth through the entire thickness of the eye lens. A separate small objective lens is spring loaded against the cornea (like a tonometer tip) so that the natural eye movements can occur safely during the examination. The distance between the objective lens and rest of the optics is variable to accommodate the movements of the eye due to pulse or breathing without affecting the image quality of the instrument. The layer by layer images can be captured on a CCD camera and stored in the computer. The reconstruction software can quantitatively display the characteristics of the cataracts, such as the location, size, and density. The optical design and performance results for the microscope are presented. The optomechanical design features of the microscope are also discussed.

Genetic algorithm and its application in lens design is studied. A new algorithm is presented which includes a genetic algorithm (GA) and damped least square (DLS) method. The convergence property of GA in lens design is demonstrated. A GA generated design is obtained without artificial intervention. The aberration correction has to be done by DLS, and the result is close to the starting configuration generated by GA.

The optical design of a breadboard high resolution infrared spectrometer for the IRS instrument on the SIRTF mission is discussed. The spectrometer uses a crossed echelle grating configuration to cover the spectral region from 10 to 20 micrometer with a resolving power of approximately equals 600. The all reflective spectrometer forms a nearly diffraction limited image of the two dimensional spectrum on a 128 multiplied by 128 arsenic doped silicon area array with 75 micrometer pixels. The design aspects discussed include, grating numerology, image quality, packaging and alignment philosophy.

Recent advances in the manufacturing of large (up to 62 mm diameter) glass blanks with axial index gradients of up to 0.20 enable significant performance gains in optical designs. The new axial gradient material has an index and dispersion similar to SF (short flint) glasses, except the index varies continuously through the axis of the blank. The axial gradient material and numerous design examples using the new material are presented.

A method for converting single mode Gaussian beams into beams with uniform irradiance profiles is described. This technique has application to laser cutting and welding, laser ablation, semiconductor mask fabrication, and other tasks. Currently, designs for rectangular and circular flat top profiles have been investigated. Experimental results are presented for an element that converts a single mode Gaussian beam into a square, flat top spot. The design is based on a Fourier transform relation between the input and output beam functions and can be implemented as a diffractive or refractive element. The form of the element reduces to a common equation that is scaled for the particular geometry involved. This scale factor contains the product of the widths of the input and output beams, the focal length of the system, and the wavelength. It is a dimensionless quantity that uniquely determines the quality of the target spot, regardless of wavelength or system geometry. A designer can thus start from a desired target quality and lay out the required optical system to achieve that quality, in contrast to an iterative approach.

The goal of the optical design of luminaires and other radiation distributors is to attain the desired illumination on the target with a given source. Usually there are constraints that should be satisfied, such as avoiding glare, maximizing the optical efficiency and respecting practical size limitations (not to mention considerations of fabrication costs, availability of materials and esthetics). While the required design procedure is well known for situations where the source can be approximated as a point or as a line, the development of an explicit analytical design method (as opposed to numerical search) for extended sources has begun only a few years ago. A solution for extended isotropic sources can be obtained by establishing a one-to-one correspondence between target points and edge rays, using the tools of nonimaging optics. The designs are called TED (tailored edge-ray designs). Particular solutions have been found in separate papers by Ries and Winston and by Gordon, Rabl and Ong. The present paper present a topological classification of all possible solutions in two dimensions and discusses their general characteristics. We show that any illumination distribution can be obtained exactly in the central region of the target, but in general there will be a certain amount of spillover outside this region. Some flexibility for tailoring designs to specific requirements (size, glare control, etc.) can be gained by the choice of the solution type, the choice of the boundary conditions, and by the use of hybrid configurations that combine several types of solution. The design method is illustrated with specific examples.

In this paper, combining refractive and diffractive effects, a new kind of infrared lenses with wavelength 1 0.6 jim was designed and produced for CO2 laser material processing. This refractive-diffractive lens (RDL) converts a CO2 laser beam into the rectangular shape with light intensity distribution in the concave shape at x-direction. A method which employs input aperture division and geometrical transformation technique for obtaining a better initial phase distribution of the iteration is presented. The experimental results show that the desired shape of the output light beam was obtained with a high efficiency in energy utilization. Keywords: Binary Optics, Diffractive optics, Infrared lens design

The optical design of a dual path imaging spectrometer and peak up camera for the IRS instrument on the SIRTF mission is discussed. The dual path configuration allows for a single area array to be simultaneously used for both low resolution spectroscopy and high resolution imagery without overlapping. This is accomplished by the use of off-axis reflective Schmidt cameras in each optical path. These cameras provide a high resolution image and a low resolution spectral image that reside side-by-side on the focal plane without residing side-by-side in the object field.

A differential equation method is applied to the design of a three-mirror telescope. The resulting system is mostly free of spherical aberration, coma and astigmatism. From caustic theory and a generalization of the Coddington Equations, the Abbe sine condition and the constant optical path length condition, three coupled differential equations, one for each reflecting surface, are generated. A system which satisfies these conditions will have a high resolution over a wide field of view. Analysis of this application is presented as a comparison to a similar three-mirror telescope system produced by conventional optimization techniques.

We describe a new form of prism spectrograph system based on aplanatic principles. The basic system is simple, comprising a prism with two spherical refracting surfaces, both operating near their aplanatic conjugates, and a spherical mirror operating near its center of curvature. This form provides a flat, accessible focal surface suitable for use with modern array detectors. Good image quality can be maintained over large wavelength intervals at fast focal ratios, making this form particularly useful for moderate resolution spectrography. Its simplicity, compactness, and tolerance of misalignment make it attractive for space and cryogenic instruments. We present there examples of operating instruments that have been constructed using this new form.

An afocal optical system designed to be attached to a conical optical beam deflector is discussed. The conical beam deflector generates a collimated optical beam that rotates along a cone-shaped trajectory in space. This output beam is then fed to the afocal attachment, a telescope, designed to tailor the beam characteristics to suit a particular application. For many applications, the afocal attachment functions as a beam expander and modifies three characteristics of the input beam. First, it expands the input beam diameter to an acceptable level. Then, it inevitably reduces the apex cone angle of the beam due to the inherent property of a telescope. Third, the stationary plane, the plane where the apex of the cone resides, is magnified and transferred to the conjugate image plane.

The optical design and the expected performances of a multi- band imaging system are presented. The instrument is to be operated in a low earth orbit in a pushbroom scanning mode. It has 15 spectral bands with the wavelength range extending from 0.45 micrometer to 10.7 micrometer. The instrument comprises a single mechanically cooled focal plane, a 36 cm aperture, wide field of view off-axis three mirror anastigmatic telescope, and an on-board calibration subsystem. The design has near diffraction limited performance for all spectral bands from visible to long wavelength infrared (IR). It has high throughput and low polarization sensitivity. To minimize the background noise at long wavelength infrared (LWIR) a cold stop is located at the exit pupil to achieve 100% cold shielding.

This paper describes a real time optimization method for optical systems. We examine the features of the global-opt optical ray tracing program, which has been developed to provide the optical engineer with interactive optimization capabilities. We illustrate the program's main features through the results of design study into an F/1.0 camera for use in a planned astronomical spectrograph. This instrument is the high resolution optical spectrograph (HROS), which is part of the international Gemini project to build twin 8 m aperture telescopes towards the end of the decade. The global-opt program allows the optical engineer to ray trace, in batch mode, up to 1 million optical systems over a period of several hours. Once complete, the engineer can explore the properties (i.e. aberrations) of these million systems in real time in order to locate the most suitable one for a particular task. This is achieved by transferring the multi- dimensional optimization problem into 3 spatial dimensions in which all the aberrations and variable parameters are represented in a 'landscape' visualization. The user is then able to interact with these moving visualizations in order to attempt system optimization. Animation of these visualizations helps the user identify any features present, which directly represent specific attributes of the design form under investigation. We have noted that these moving features resemble water waves, hence the interactive optimization process described here is made analogous to 'surfing.'

The space telescope imaging spectrograph (STIS) instrument is due to be installed on board the Hubble Space Telescope (HST) in 1997. STIS uses 20 filters located on a wheel that can rotate any one of 88 apertures or combination filter/aperture in to the beam path. The instrument incorporates a continuous range of spectral response from the VUV (115.0 nm) to 1 micrometer. Therefore, filters that perform in the VUV are discussed as well as filters that operate in the near infrared. Neutral density filters are also being used for on-board calibration from 300 nm to Lyman-Alpha (121.6 nm).

It is common for spectrometers to cover large spectral ranges with a single focal plane. It is difficult or impossible to strongly suppress reflections with a single coating stack. Abutting short and long wavelengths coatings is expensive, and the performance can still be insufficient. We discuss a novel structure that comprises a single layer whose thickness varies along the length of the dispersed spectrum. Such a coating has high performance, is inexpensive, and has large fabrication tolerances. We further report on measurements of the performance of one such optic. Extension of the concept are discussed.

The aim of present work is the development of a method of high reflective (H/R) optical multilayer coating on KTP and BK-7 Glass with the specification: R (reflectance): greater than or equal to 99.9% at 1064 nm. T (transmittance): greater than or equal to 95% at 532 nm and T (transmittance): greater than or equal to 95% at 809 nm for a second harmonic generation (SHG) laser. The parameters that can be used to reach these goals are the number of layers in the multilayer, the layer thicknesses and refractive indices and extinction coefficients of the individual layers and of surrounding media. Clearly, the more demanding the performance specifications, the more complex is the resulting system. In our case, we have the most demanding performance specification, that is why the technology of obtaining coatings with this specification is very precise and complicated. In order to fulfill the demand of high reflectance at lambda equals 1064 nm it is necessary to deposit 30 or more alternative quarter wavelength thickness layers of ZrO₂ and SiO₂ and to fulfill the demand of high transmittance at lambda₁ equals 532 nm and lambda₂ equals 809 nm the SiO₂ layer of lambda/8 (last layer) optical thickness is used to suppress the secondary maxima. The perfect suppression of secondary maxima takes place, when we deposit multilayer coating with equal optical thicknesses of high and low refractive indexes layers. The performance of many optical multilayers depends critically on the thicknesses of individual layers. The control of the layer thicknesses during their deposition is therefore very important. The most common techniques used is optical monitoring performing indirectly on a witness glass (or the chip). R (reflectance) optical monitoring is however used to measure the quantities of each layer optical thicknesses in our system. We used different control wavelength to monitor and control each layer optical thickness with different coating materials for compensating the deposited optical thickness.

In situ x-ray monitoring of reflectivity in the short range 0.05 - 0.3 nm for investigation of thin carbon layers and multilayer carbon structures is proposed. X-ray monitoring is based on periodical alternations of Fresnel's reflectivity when layer thickness increases or decreases. The source of x rays with wavelength 0.154 nm was located out of working volume of installation and consisted of x-ray tube, monochromator block and collimating system. The objects of in-situ investigations were carbon films obtained by rf-plasma discharge and magnetron methods. Multilayer carbon structures were synthesized by alternating these layers. Density and microroughness of the growing film were determined for every half-wave of reflectivity oscillations that corresponds to averaging by the layer of 1.0 nm thickness. It is shown that x-ray monitoring system permits the user to control the layers thickness during multilayer structure growth with precision up to 0.1 nm.

Increasing number of bandwidth intensive applications demand introduction of concurrency among multiple user transmissions, using techniques such as time division multiplexing (TDM) or wavelength division multiplexing (WDM), to achieve higher aggregate bandwidth. Commercial exploitation of WDM networks, despite their immense potential and promise, find extreme reluctance due to their vulnerability to the wavelength instability of the transmitter sources, and budgetary concerns raised by the inordinate cost of stabilizing them. Robust WDM network uses an intelligent multichannel wavelength tracking receiver that is capable of dynamically accommodating the manufacturing and operating imperfections of the transmitter sources. This yields robust WDM to be a lucrative option for cost sensitive computer networking markets. In this paper we present token-based medium access control protocol and network node architecture designed for the demonstration testbed of robust WDM network. Behavior of average waiting time for a typical connection request on the network is presented using computer simulation.

Photonic switching systems image arrays of sources onto arrays of detectors and modulators. Even this simple functionality poses serious challenges for the optical engineer. Image quality must be excellent because the large modulator bandwidth demands small modulator size. Magnification and distortion must be precisely corrected for the spot array to fit onto the detector array. The system must be extraordinarily stable for the spots to stay on the detector array. For these reasons, photonic switching systems have traditionally been mounted on vibration isolated optical tables. This paper describes our newest system, which is mounted in a standard electronics frame. Experimental results and design methodologies are discussed.

A scanning beam collimation (SBC) method is developed for measuring dynamic angle variations in which an acousto-optic deflector is used as a diffractive scanner to compensate the angle variation in real time, and a position sensor is used to detect the position of the beam that is reflected from the reflector (i.e., object) to be measured. The angle variation can be measured at high speed due to the very high scanning speed available in the acousto-optic deflector. There was good agreement between the angle variation measured using the SBC method and that using a conventional electronic autocollimator. The repeatability, resolution, and linearity of the scanning beam collimation method were determined using a piezo translator to generate tilt angle; the results showing that high accuracy also can be achieved in dynamic angle variation measurement. The SBC method was applied to measure the tilt angle variation caused by the beating force of a dragonfly attached to one end of a gauge block. The results confirmed the effectiveness of this new method.

An optically routed gate array (OPGA) is used to implement a simple game of Tic Tac Toe to demonstrate the utility of electro-optical circuits which embody user input, display and logic functions in a single device. Progress on routing techniques layout and logic simulation are presented.

Since acousto-optic tunable filter (AOTF) is one of the volume gratings that has an extremely small dielectric constant (or index of refraction) modulation it needs the grate volume (about mm or cm-order thickness) to attain the sufficient diffraction efficiency. If the width or the coherence length of incident light beam is much smaller than the width of the volume gratings, AOTF needs to be treated by 2-dimensional (2D) coupled mode theory to study the amplitude distributions of the transmission and the diffraction light waves, the spatial resolving power of the Bragg diffraction imaging, and the trace of energy flow, which cannot be obtained by 1D-model. Among the above- mentioned 2D problems, we theoretically studied the trace of energy flow of AOTF made of TeO₂ crystal, taking account of being an optically anisotropic medium.

Beamsplitter is one kind of optical element or apparatus which changes one light beam into two or more light beams, and it has been widely used in optical technique. We have already introduced a series ordinary beamsplitter made by using birefringent crystal. In this article we introduce a new series type beamsplitter, that is an adjustable displacement parallel beamsplitter. We can change one light beam into two parallel light beams, and the displacement between the two parallel light beams can be adjusted by using this type of beamsplitter. According to the property of the two parallel light beams, the beamsplitter can be divided into two kinds: the first kind, the two light beams both are polarization light beams; the second kind, the two light beams both are nonpolarization light beams. We have discussed their structure character, working principle and use specification in this article.

Light beam attenuator is one kind of optical element which has been widely used in optical technique. According to beam attenuation principle, it can be divided into two kinds, one is absorbing type attenuator, the other is non-absorbing type attenuator. There has been considerable attention paid to study visible attenuator, but there are few ways to attenuate 3.39 micrometer laser beam. In this article we have introduced a series new type 3.39 micrometer laser beam attenuator made by using birefringent crystal. Some is absorbing type attenuator, the other is non-absorbing type attenuator. Such as: two calcite parallel plates type, two yttrium orthovanadate prism type, two yttrium orthovanadate parallel plates plus lambda/2 waveplate type, etc.

Nearly all light sources are partially polarization, the photomultiplier tube, photocell detector and grating have polarization sensitive effect. When we use natural light to do some experiment, the light from the light source must be depolarized. In order to reduce the polarization sensitive effect of the detector, we need fix a depolarizer in front of the detector. Since the times of 1928, there has been considerable attention paid to the study of polychromatic light depolarizer. But there are very limited number of ways to depolarize monochromatic light. We have ever introduced some kind of single element structure monochromatic light depolarizer made by using birefringent crystal. In this article we introduce some kind of double elements structure monochromatic light depolarizer made by using some birefringent crystal and fused silica crystal. We introduce their structure character, working principle and use specification in detail.

A new type of the normal incidence scanning reflectometer has been designed and constructed. In the system design, instead of using a reference reflective sample or adjusting the optical path as did in the traditional design, we use a fixed M-type fused quartz prism to split the incidence light source beam into two ones by a total internal reflection configuration. Therefore, these two light beam have the same spot sizes, intensities and spectral response. One beam goes directly to the detector and is used as the incidence reference beam. The second sampling beam goes to the sample first, and then is reflected by the sample with the beam intensity measured finally by the same detector. A metal disk with three holes is driven precisely by a stepping motor and is used to control the reference beam, reflection beam and background signals to be measured in sequence. Afterwards, the absolute reflectivity of the sample at the certain wavelength can be determined immediately by the computer through calculating those three signals. The system is controlled automatically by the computer and worked in a wavelength range from 400 to 800 nm under a 5-degree nearly normal incidence angle condition. In the paper, the details of the system design, optical element configuration and error reduction are given and discussed. The measured reflective spectral results for testing samples are also given and shown in good agreement with those measured by other optical method. The system designed in this work, however, is simpler and more reliable to be used in many optical measurements of the sample.

Liquids have been shown to be very effective in the design of apochromatic lenses. The incorporation of abnormal liquids is complicated by their large thermal coefficients of refractive index (dn/dT). To make a glass-liquid design thermally stable, two liquids with different dn/dT and dispersions are typically used. This paper, which extends previously reported investigations of liquid dn/dT dependencies in the visible spectrum (SPIE Volume 2512, 1995), explores the dependence of dn/DT, abnormal dispersion, and composition for a number of liquids. The optical property measurements were made at the Vavilov State Optical Institute, St. Petersburg, Russia, in collaboration with the Lockheed Martin Advanced Technology Center, Palo Alto, California.

Annular two phase flow is one of the most common regimes of gas/liquid flow found in industrial equipment. In this regime, the liquid flows in part as a film on the channel walls while the rest of the liquid is carried as drops by the gas flowing in the center of the channel. Detailed knowledge of the liquid drops particularly their sizes and velocities is essential in processes involving heat and mass transfer. This information is of great importance for the oil industry where inclined drilling has recently become a common practice. The effect of inclination on the drop sizes is still unknown and requires further investigation. Laser diffraction is one of the few available techniques which is widely used for the measurement of droplet size distribution. Although the technique is simple to use, it is not free from problems. This paper highlights the practical difficulties encountered when the technique was used to measure the drop size distribution in an inclinable flow column. The laser system was mounted on the rig and the flow column was rotated from vertical to horizontal position. Liquid drops appearing on the optical windows prohibited laser measurements. Other problems included the glass reflections and vibration when the rig was in operation. In this paper some practical suggestions have been made to overcome these problems and some useful results have been included.

A system of three identical CCD-cameras was developed enabling stereoscopic auroral observations. An image intensifier allows for real-time imaging of auroral arcs with interference or broad-band filters. The combination of a small-angle optics with a CCD-chip of 756 by 580 pixels provides spatial resolutions of auroral small-scale structures down to 20 m. The cameras are controlled by personal computers with integrated global positioning (GPS) modules enabling time synchronization of the cameras and providing the exact geographical position for the portable cameras. Calibration with a standard light source is the basis for quantitative evaluation of images by image processing techniques. The current technical development is the combination with local operating networks (LON) for monitoring camera parameters like voltage and temperature and remote control of parameters like filter positions, mounting tilt angles and camera gain.

In many optical experimental systems, an achromatic 1/4 wavelength retarder is needed to satisfy experiment condition. This can be fulfilled using a rhomb prism which has a nearly constant refractive index in the working wavelength range. To make the easy use of the prism in the optical system and to avoid the problem of central beam deviation, one type of the prism having three total internal reflection faces can be designed to have the total retarding angle equal to 90 degrees. Though the angle can be relatively easily calculated in principle, the size and optical opening window of the prism depend on the practical and optimum geometric design. In this paper, we give a few examples of geometric design by taking different size parameters into consideration. We have made the prisms and put them into the application of measuring the magneto- optical Kerr ellipticity with success. Detailed calculation and error reduction in the design are also given.