The author has found that linear approximations in heat transfer, elasticity and optics are powerful tools that are adequate for solving the great majority of optomechanical engineering design problems. In his experience the analytical errors are minimized by assuming linearity in the equations and unifying the solution into a single analytical code. He suggest that organizations planning optomechanical analyses perform top-down error budgets of the processes involved in order to design the most cost-effective analysis for the project. An ISO standard is recommended as a guide to the error budgeting process.

Mechanical vibrations have a large impact on the optical performance of many systems. In order to accurately predict optical performance, an integrated optomechanical analysis is required. It is difficult to pass finite element vibration data to optical programs since harmonic response includes phase angles due to damping, and random response has lost all phase information. This paper discusses a new technique to decompose harmonic and random response into pointing, focus, and wavefront error components in an efficient manner. This technique is compatible with commonly used error budgets. A method to identify key contributors to each error component is also presented.

A method to predict performance of adaptive optical systems subject to mechanical perturbations is presented. Integrated modeling techniques coupling finite element analysis and optical design software are discussed that enable mechanical design trades of an adaptive mirror assembly based on correctability of the optical system wavefront error. This method is based on the linearity of wavefront error consistent with that caused by mechanical disturbances during operation. Optical surface sensitivities are computed based on rigid-body and higher-order surface deformations that relate mechanical surface errors to optical system wavefront error. The sensitivities are then used to determine the best-fit set of actuators to minimize the wavefront error in the optical system due to finite element derived mechanical disturbances. An example is demonstrated for a Cassegrain telescope with an active primary mirror.

The Full-Sky Astrometric Mapping Explorer (FAME) instrument was designed to be an extremely accurate star mapper. To map the entire sky, the earth-orbiting FAME satellite rotates about its spin axis every 40 minutes, and uses solar pressure to precess about the spin axis every 40 days. The instrument had two apertures, separated by 84.3 degrees, allowing a star to be imaged twice in one rotation with about a 10 minute delay. This delay enables the elimination of most measurement errors. The light enters an aperture, bounces off of a compound fold flat mirror, (2 ULE fold flats bonded together at an 84.3 degree angle), passes through a Cassegrain telescope, and is imaged by the focal plane. The requirement for the fold flat’s dimensional stability is severe - the variation in the angle between the flats (basic angle) must be held to be held to 10 μarcsec during the 10 minute period between the first and second time a star is imaged. This paper presents a transient opto-thermo-mechanical analysis of the optical system.

Based on our model, a program designed by us can give the distributions of temperature, stress and refractive index inside the laser medium of diode-pumped rod laser. Some displayed results obtained by simulation are in excellent agreement with experimental results reported in the literature.

Diffraction-limited performance of 30-m class telescopes requires the integration of structural, optical and control systems to sense and counteract real time disturbances to the telescope. Accurate simulation of an integrated telescope model is essential for optical performance estimation and design validation. Our approach to integrated time domain modeling of large telescopes is to interface commercially available structural,optical and control modeling software packages. The model architecture, data structures, and the interfacing tools of the simulation environment are presented. Preliminary simulation results of a 30-m class telescope subject to wind load and a ground layer phase screen are presented.

A linear optical model for 30 m class astronomical telescopes is discussed. Our approach to modeling the optical performance of the telescope is an extension of the line-of-sight analysis to incorporate low order image aberrations. The model describes the optical path difference at the telescope exit pupil as a linear combination of primary and secondary mirror displacements and deformations in a Zernike basis. Although the model is valid over a significant, useful range of deformation amplitude and field of view, it is particularly convenient for the design and investigation of active optics control systems operating close to the desired condition of an unperturbed telescope. The formalism of the linear model and comparison with the OPD results generated by ray-tracing are discussed.

This note presents some of the optical modeling work performed at JPL and at Goddard in support of the Laser Interferometer Space Antenna (LISA) effort. The end-to-end optical model will be used to generate a synthetic data stream. The simulation will have the spacecraft moving in their respective orbits, with pointing of the spacecraft and station keeping about the proof masses accomplished using a control scheme, which minimizes the disturbance on the proof masses in the sensitive direction. The resulting data stream gives an indication of the magnitude of instrumental noise due to pointing jitter and motions of the spacecraft with respect to the proof masses. To reach this goal portions of the overall optical train have been modeled. Subsequent work will, as the modeling software and optical model evolve, combine these pieces into an integrated system.

Initial optical modeling activities for the JWST project systems engineering team are presented. This paper discusses the development of the linear optical model, used primarily for integrated modeling and sensitivity studies. Various issues and assumptions are considered and preliminary results are presented.

The prototyping process of miniaturized plastic imaging lens is described. The sequence is divided into five phases: specification, optics design, optomechanical design, manufacturing and characterization. During specification, the optical and mechanical requirements of the lens are defined. In the optical design phase, the lens is optimized, and a tolerance analysis is carried out. Simulation tools, especially, an image quality simulator, can be used to visualize and verify the performance of the design. Mechanical design is performed considering the geometrical specifications and optical tolerances of the system. In addition, stray light analysis is carried out to verify the optical performance of the optomechanics. Plastic optics are particularly vulnerable to stray light due to the integrated mountings, which provide additional paths for unwanted light. If the prototype is used for preliminary performance evaluation of a future product, the differences between prototype and mass manufacturing methods need to be considered carefully. After the lenses are manufactured they are characterized, and the experimental results are compared with the original specifications and estimations obtained from the previous design verification simulations. New error analysis simulations can be performed in order to pinpoint faults in manufactured modules. If the performance of the prototype is not sufficient, a new prototyping iteration circle is needed. The whole process is described and analyzed using a miniature, plastic imaging lens as an example, but it can also be applied to other optical prototyping tasks.

The reduction in molecular outgassing afforded by the high vacuum degassing of the system components and the expected outgassing of the same when employed under normal ambient pressure and purging are evaluated and discussed. The contaminant deposits that could be expected from the residual outgassing systems are evaluated. A comparison of the contamination produced by the outgassed and non-outgassed systems has been carried out and is based on the outgassing rate of a combination of devices in the compartment obtained at the end of a reasonable period of outgassing in vacuum and on the rates at the time of employment.

It is shown that a light beam diffracting from a narrow slit (width on the order of magnitude of the wavelength of the incident light) at oblique incidence exhibits coma aberration. The motivation for this study was simulation of an optical system in which light is emitted from a waveguide array at an oblique angle. It was found that the coma aberration of the slit or waveguide array is canceled out exactly by the coma aberration of a collimating plano-convex cylindrical lens. Analytical expressions, numerical simulation results and laboratory results are presented.

Thin, visibly opaque components for use in infrared transmission present a challenge in tolerancing and manufacture: Most optical shops do not have access to infrared interferometry and so must evaluate the opposing surfaces in visible light. The inevitable bending of thin parts will create surface deformations that are individually far in excess of allowable limits. However if the opposing surface deformations track each other, the part may be perfectly functional. The dilemma is between over-specification of the surfaces and consequent multiplication in costs and schedule; vs. verification in the infrared, thus eliminating most perfectly competent vendors. Herein, I present a novel interferometric cavity setup utilizing a standard, commercial interferometer, in which the test beam reflects twice from each side, in point by point registration across the aperture. I also present fringe-scaling factors based on angle of incidence and index of refraction. The cavity error can be conveniently subtracted. Small wedge can be measured or eliminated, or if desired, large wedge can be eliminated. The components can, thus, be specified and verified functionally with significant reduction in difficulty and cost. NOTE: this work was presented at SPIE in 1991, v 1527 p 188. The audience that day was very small. I think the technique remains valuable and virtually unknown.

The reflected signature of an optical fiber Bragg grating is analyzed using the transfer function method. This approach is capable to cast all relevant quantities into proper places and provides a better physical understanding. The relationship between reflected signal, number of periods, index of refraction, and reflected wave phase is elucidated. The condition for which the maximum reflectivity is achieved is fully examined. We also have derived an expression to predict the reflectivity minima accurately when the reflected wave is detuned. Furthermore, using the segmented potential approach, this model can handle arbitrary index of refraction profiles and compare the strength of optical reflectivity of different profiles. The condition of a non-uniform grating is also addressed.

It is noted that the fiber propagation loss is a random process along the length of propagation. The stochastic nature of the loss process induces a random fluctuation to the energy of the optical signals, which, as an extra source of noise, could become comparable to the amplified-spontaneous-emission noise of optical amplifiers. The optical noise in random loss/gain has a quantum origin, as a manifestation of the corpuscular nature of electromagnetic radiation. This paper adopts the Schrodinger representation, and uses a density matrix in the basis of photon number states to describe the optical signals and their interaction with the environment of loss/gain media. When the environmental degrees of freedom are traced out, a reduced density matrix is obtained in the diagonal form, which describes the total energy of the optical signal evolving along the propagation distance. Such formulism provides an intuitive interpretation of the quantum-optical noise as the result of a classical Markov process in the space of the photon number states. The formulism would be more convenient for practical engineers, and should be sufficient for fiber-optic systems with direct intensity detection, because the quantity of concern is indeed the number of photons contained in a signal pulse. Even better, the model admits analytical solutions to the photon-number distribution of the optical signals.

Linear statistical models have been generated to predict the performance of metal-semiconductor-metal (MSM) PDs for multi-gigabit optical interconnections. The models estimate the bandwidth and responsivity of the MSM PDs based on the input factors: absorbing layer thickness, detector size, finger widths and finger gaps. The design of experiments (DOE) approach was employed to obtain the necessary data to construct the models. Numerous samples were fabricated so that multiple devices measurements could serve to both construct and verify the linear statistical models. The MSM PDs were fabricated from material with structure InAlAs/InAlGaAs/InGaAs (2000Å, 3000Å or 5000Å, absorbing layer)/InAlAs. The MSM interdigitated fingers were photolithographically defined with finger gaps and widths varying as DOE parameters. A benzocyclobutene (BCB, Cyclotene 35) layer was spin-coated onto all of the samples as isolation from the probing pads. In the bandwidth analysis, the detector size (S) and material thickness (T) were investigated with a fixed finger width (1 μm) and gap (1 μm). Taking the measured results of these detectors in the design matrix, and using least square regression, the model equations were derived as: Bandwidth (GHz) = 12.87 - 0.065S - 3T - 0.02ST. After these equations were developed, predictive calculated results from these equations were then further used to predict and compare measured results on devices that were not used in the statistical model. This leads to an average deviation between predicted and measured bandwidth of less than 5%. In the responsivity analysis, the predictive calculation leads to an average deviation less than 11%.

Color measurements in textile samples is a very well known problem, current measurement methods are repositioning-of-sample dependent. In particular, the orientation of the sample is the first parameter of discrepancies in the reproducibility of measurements, even when we use the same instrument and the same sample. In this work we propose a new optical arrangement which is insensible to rotations. Preliminary experimental results show the invariance under rotations of two-dimensional periodic samples.

Recently it was reported a method to calculate the instrument function of a two-aperture radiometer which describes the energy transport through two apertures using the theory of partial coherence. The result of that work was expressed as a multiplication of a two-fold integral and its complex conjugate. In this work we solve partially this two-fold integral, particularly we introduce a semi-cicle angular integral that reduces the integration. This new representation allows a faster numerical evaluation as well as an easier interpretation of energy transport for radiometric considerations.

Pulsed short-arc xenon flashlamps are used as the source of optical radiation in many analytical and life science instruments. They provide useable energy from below 150nm to over 1100nm. As a pulsed source they can operate at high peak power while still maintaining a low average power. The electrical operating conditions play a major role in the final performance of the lamp. This paper will look at the effect on electrical to optical conversion efficiency, arc size, and spectral distribution of varied electrical operating conditions. Some "rules of thumb" will be developed for the above characteristics as a function of electrical operating conditions. Specific attention will be paid to the new generation of smaller sized flashlamps.

Light that is scattered from lenses and mirrors in an optical system produces a halo of stray light around bright objects within the field of view. The angular distribution of scattered light from any one component is usually described by the Harvey model. This paper presents analytic expressions for the scattered irradiance at a focal plane from optical components that scatter light in accordance with the Harvey model. It is found that the irradiance is independent of the location of an optical element within the system, provided the element is not located at or near an intermediate image plane. It is also found that the irradiance has little or no dependence on the size of the element.

The National Ignition Facility (NIF), currently under construction at the University of California s Lawrence Livermore National Laboratory (LLNL) is a stadium-sized facility containing a 192-beam, 1.8 Megajoule, 500-Terrawatt, 351-nm laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. NIF is being built by the National Nuclear Security Administration and when completed will be the world s largest laser experimental system, providing a national center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF s 192 energetic laser beams will compress fusion targets to conditions where they will ignite and burn, liberating more energy than required to initiate the fusion reaction. The first four beamlines (a quad) are currently being commissioned, with increasingly energetic laser pulses being propagated throughout the laser system. Success on many of the NIF laser s missions depends on obtaining precisely specified energy waveforms from each of the 192 beams over a wide variety of pulse lengths and temporal shapes. A computational system, the Laser Performance Operations Model (LPOM) has been developed and deployed during NIF commissioning to automate the laser setup process, and accurately predict laser energtics. For each shot on NIF, the LPOM determines the characteristics of the injection laser system required to achieve the desired main laser output, provides parameter checking for equipment protection, determines the required diagnostic setup, and supplies post-shot data analysis and reporting.

In this paper, an imaging system simulation tool is presented. With the tool, it is possible to simulate the performance (quality) of an imaging system. Furthermore, the system allows optimization of the lens system for a given image sensor. Experiments have shown that the tool is useful in actual lens design.

The characteristics of the vision-based human-computer interaction system have been analyzed, and the practical application and its limited factors at present time have also been mentioned. The information process methods have been put forward. In order to make the communication flexible and spontaneous, the algorithms to adaptive control of user’s head movement has been designed, and the events-based methods and object-oriented computer language is used to develop the system software, by experiment testing, we found that under given condition, these methods and algorithms can meet the need of the HCI.

A kind of eye-gaze input sensing model based on the pupil’s relative offset to the reflection point on the cornea (Purkinje spot) from an assistant infrared light source in front of the user’s head, has been completely set up. A set of control strategy that can adapt to the user’s head movement, has also been put forwards. It can effectively overcome the difficulties existing in the similar systems that the user’s head should be stationary or just allowed a little movement while the system works. Therefore it is a spontaneous and harmonious human-computer interaction system. Moreover, this system has the obvious merits such as convenient to use, non-contact, non-wear, non-interference, non-restraint, and so on. An experiment eye-gaze input platform for human-computer interaction has been built, and the sensing and controlling model have been verified.

A non-contact morphology system for 360° object surface measurement, involving a CCD camera, a line-structured light source and a rotated platform has been developed based on the triangulation method. The system parameters have been optimized to meet the requirement of system specification, such as range scope, range resolution, measurement accuracy and the shadow effect. For sampling the whole object surface, the CCD camera captures one frame after the motor rotates every step of 1.5° under the control of a computer. The mapping relationship among the 2-D images and 3-D surfaces from the different views and orientations can be developed by means of the spatial geometric correspondence. Moreover, the intensity, color and texture information from the CCD intensity image can be affixed to the entire 3-D surface with OpenGL. The system records more than 160000 facial coordinates with a dynamic resolution of approximately 1 mm in 60s. Examples of application of the system are given.

The coupling length and coupling ratio is defined as input and output respectively, which are used to train the neural network model. Radial base function neural network model is built for optical fiber direction coupler, which is in turn simulated and designed through the model. This method has the advantages of speediness, accuracy and reliability, which are identified by the design example. It can be used to design the other kind of optical passive device. This way is a novel design approach, which can save the cost of device design, decrease period of design and has a good prospect of application.

In this paper,we propose and demonstrate a novel technique for the spectrum-sliced wavelength-division-multiplexed optical communication-switching network.The fiber ring light source can be used to test the optical communication-switching network.We analyze the performance of the optical communication system, with considering the crosstalk and loss of each switching element and the light source power.We compare the worst case for the every channel to analysis the performance of the mesh-switching optical communication system.

A set of nonlinear differential equations are derived from the first principles, namely the Maxwell's equations and the material responses to electromagnetic excitations. The derivation retains the mathematical exactitude down to details. Still in compact and convenient forms, the final equations include the effect of group-velocity dispersion down to an arbitrary order, and take into account the frequency variations of the optical loss as well as the transverse modal function. Also established is a new formulation of multi-component nonlinear differential equations, which is especially suitable for the study of wide-band wavelength-division multiplexed systems of optical communications. The formulations are applied to discuss the problem of compensating the optical nonlinearity of fiber transmission lines using optical phase conjugation. Two system configurations are identified suitable for nonlinearity compensation. One setup is mirror-symmetric and the other translationally symmetric about the optical phase conjugator, both being in a scaled sense.

The complex study of a ultra-fine (4000 to 5870 grooves/mm) holographic gratings designed for Near Ultra Violet (NUV) channel of Cosmic Origin Spectrograph (COS) are presented. The gratings underwent a comprehensive program of efficiency and scatter characterization at flight-like environment conditions. Initial tests revealed significant departures of grating efficiencies from the values predicted. Effects of profile non-replication (layers nonconformity) for multi-layer coated grating surfaces are investigated. The rigorous efficiency modeling based on groove profiling atomic force microscopy (AFM) data for both multi-layer conformal and non-conformal coated gratings in both polarizations allowed to identify the problem as a leaky mode anomalies for dielectrically coated gratings. Both shift in peak efficiencies and wide absorption band are observed to be critically dependant of grating groove shape and reflective coating thickness. Grating depth/profile topography changes induced by coating process are observed and called for groove profile measurements at all stages of the gratings production line. Grating scatter characterizations data for COS and SORCE/SOLSTICE gratings at UV-VUV wavelength are presented. The wavelength scaling at VUV-UV waveband (140 nm to 442 nm) for holographically ruled 3600 gr/mm grating are also reported.