In precision optical instruments, it is often the case that aspects of the illumination system pupil--such as ellipticity, telecentricity, and partial coherence--relate directly to image resolution and placement accuracy. Standard design and analysis tools are often ill-suited to performing tolerance analyses on illuminators, since the figures-of-merit in terms of system performance do not reduce neatly to wavefront and distortion, as they often do for imaging optics. In order to address these deficiencies, we developed a multiparameter tolerancing method based on a probabilistic treatment of errors in an illumination system, and we will describe the work we have done in this paper.

There has been much written over the years about the generation of optical system fabrication, assembly, and alignment tolerances leading to a performance error budget and predicted system performance. Over my 40 years of optical design experience I have become increasingly more cautious (and concerned) about how accurately we, the optics community, are tolerancing our systems and predicting their manufactured performance. In this paper I will share with you some of these concerns along with recommended ways of avoiding the many "speed bumps," "pot holes," and other common issues encountered when tolerancing. And of course I will reveal why "tolerances don't lie" and how this relates to the Grand Canyon.

Our work discusses the tolerance modeling of an optical fiber that is inserted into a cylindrical alignment bore. We note that some commercial optical simulation software suites have the mechanical tolerance operands entered in Cartesian coordinates and if radial variation is entered as simple X and Y de-centering, there arises a kind of "corner condition" where fiber in the opto-mechanical model is offset more than is possible in the physical implementation resulting in an overly-conservative estimate of the worst-case coupling efficiency. Approaches to avoid this over estimation are presented and discussed.

The wavefront coding technology is known as a system-level technology which can extend the depth of focus of optical system by innovative optical design and image restoration. This technology can control misfocus related aberrations including misfocus, astigmatism, and Petzval curvature, temperature-related misfocus in digital imaging systems. It can also help optical system tolerate more residual error in optical manufacturing and alignment besides misfocus. The brief introduction of wavefront coding technology and the wavefront coded TMA system under research is presented respectively in part 1 and part 2. The "MTF similarity" is defined to describe the relationship among MTF at different position or different fields in the third part. It is also shown in this part that the MTF similarity of wavefront coded system is much higher than the normal system within a large range. In part 4 comparison between the origin system and the new system with wavefront coding technology is provided after multiple errors are introduced, from which it can be observed that the system with wavefront coding technology can tolerate much bigger error than origin system. The error tolerance is re-distributed according to a new criterion based on MTF similarity. If the MTF similarity is less than a certain value, it can be regarded that the system can tolerate the residual error. The new error tolerance is displayed and it is shown that the wavefront coding technology can also loosen the error distributing besides extended the depth of focus.

A gated spectrometer has been designed for real-time, pulsed infrared (IR) studies at the National Synchrotron Light Source at the Brookhaven National Laboratory. A pair of 90-degree, off-axis parabolic mirrors are used to relay the light from an entrance slit to an output IR recording camera. With an initial wavelength range of 1500-4500 nm required, gratings could not be used in the spectrometer because grating orders would overlap. A magnesium oxide prism, placed between these parabolic mirrors, serves as the dispersion element. The spectrometer is doubly telecentric. With proper choice of the air spacing between the prism and the second parabolic mirror, any spectral region of interest within the InSb camera array's sensitivity region can be recorded. The wavelengths leaving the second parabolic mirror are collimated, thereby relaxing the camera positioning tolerance. To set up the instrument, two different wavelength (visible) lasers are introduced at the entrance slit and made collinear with the optical axis via flip mirrors. After dispersion by the prism, these two laser beams are directed to tick marks located on the outside housing of the gated IR camera. This provides first-order wavelength calibration for the instrument. Light that is reflected off the front prism face is coupled into a high-speed detector to verify steady radiance during the gated spectral imaging. Alignment features include tick marks on the prism and parabolic mirrors. This instrument was designed to complement singlepoint pyrometry, which provides continuous time histories of a small collection of spots from shock-heated targets.

A key facet in taking an optical design from concept to an as-built system (or set of systems) is proper planning for alignment. Performing detailed analysis and investigating options for alignment are both imperative, especially in light of the role cost and performance typically have on success. In this paper we specifically discuss using derivative information in engineering an optical system for alignment. An example illustrates the flexible and powerful nature of such calculations in solving practical problems encountered in optical system design, development, and manufacturing.

Three methods of line of sight alignment are compared and contrasted for ease of use, accuracy of alignment and cost of equipment and fixtures. The three methods are the classical use of an alignment telescope, use of a laser beam to establish an axis, something impossible until the invention of the CW laser, and an autostigmatic microscope used in conjunction with mechanical means to establish an axis or points in space. While the method of choice is usually a pragmatic one of using the equipment at hand, this paper will demonstrate the flexibility of the autostigmatic microscope approach.

Alignment telescopes and interferometers are commonly used for the alignment of an optical system. Although alignment telescopes quantify angles, they are not particular helpful for quantifying wavefront quality. Interferometers by comparison are often used for alignment, but are most useful for quantifying wavefront quality. However, an optical system must be fairly well aligned before one can even use an interferometer. Many optical systems require the sensitivity and accuracy of an interferometer for final alignment. However, there are many optical systems where visual inspection of a star test would be adequate for system qualification, except for the fact that a visual test is qualitative. An autostigmatic or point source microscope (PSM) is a convenient tool for alignment and performance of a star-test. Like an alignment telescope, an autostigmatic microscope does not conveniently quantify the wavefront quality. Once a focused spot is obtained with an autostigmatic microscope a plane-parallel plate inserted into the converging beam path may be used to introduce a known focus shift. The resulting image may be used to estimate low order-aberrations. Experimental results are presented using very simple hardware.

This paper outlines progress to-date with the commissioning of the Bent-Gregorian focus at the Large Binocular Telescope. Active alignment at this focus utilizes and auto-guider system and a Shack Hartman wavefront sensor to determine system perturbations and drive corrections into various active optical components. Reported results include the correction of bi-nodal astigmatism, performance of the Shack-Hartman wavefront sensor, convergence of wavefront correction, convergence time, as well as various results pertaining to tracking and guiding.

There is a long list of new ground-based optical telescopes being considered around the world. While many are conventional Cassegrain and Ritchey-Chretien designs, some are from a family of three mirror anastigmatic (TMA) telescopes that are configured with an offset field (but still obscured) that trace back to designs developed in the 1970s for military applications. The nodal theory of aberrations, developed in the late 1970s, provides valuable insights into the response of TMA telescopes to alignment errors. Here it is shown for the first time that the alignment limiting aberration in any TMA telescope is a 3rd order astigmatism term with a new field dependence, termed field-asymmetric, field-linear 3rd order astigmatism. It is also shown that a TMA telescope under assembly that is only measured to have excellent/perfect performance onaxis is not aligned in any significant way. This is because the new astigmatic term is always zero on-axis, even though it is large over the field of view. Knowledge of this intrinsic misalignment aberration field for any TMA telescope aids greatly in ensuring it can be aligned successfully. The James Webb Space Telescope (JWST), is used an example of a relevant TMA system.

The James Webb Space Telescope (JWST) is an infrared space telescope scheduled for launch in 2013. JWST has a 6.5 meter diameter deployable and segmented primary mirror, a deployable secondary mirror, and a deployable sun-shade. The optical train of JWST consists of the Optical Telescope Element (OTE), and the Integrated Science Instrument Module (ISIM), which contains four science instruments. When the four science instruments are integrated to ISIM at NASA Goddard Space Flight Center, the structure becomes the ISIM Element. The ISIM Element is assembled at ambient cleanroom conditions using theodolite, photogrammetry, and laser tracker metrology, but it operates at cryogenic temperature, and temperature-induced mechanical and alignment changes are measured using photogrammetry. The OTE simulator (OSIM) is a high-fidelity, cryogenic, telescope simulator that features a ~1.5 meter diameter powered mirror. OSIM is used to test the optical performance of the science instruments in the ISIM Element, including focus, pupil shear, and wavefront error. OSIM is aligned to the flight coordinate system in six degrees of freedom via OSIM-internal cryogenic mechanisms and feedback from alignment sensors. We highlight optical metrology methods, introduce the ISIM and the Science Instruments, describe the ambient alignment and test plan, the cryogenic test plan, and verification of optical performance of the ISIM Element in cryo-vacuum environment.

The requirements for the Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) designate that the instrument be aligned to within specified wavefront tolerance limits. A sensitivity analysis was performed to determine the best selection of field point locations and wavelengths at which to take measurements to meet the wavefront requirements. This paper presents an overview of this analysis.

The requirements for the Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) specify that the instrument be aligned and operate at cryogenic temperatures. The error budget for the integration of the optical components was analyzed using a multi-parameter Monte Carlo simulation with compensators. Results from these simulations were used to revise the alignment process and error budget. This paper presents an overview of this analysis.

The phase-shifting Grating-Slit test has advantages of large measurement dynamic range when using with spatial light modulator (SLM) to generate the illuminating. But the rotary slit in the test does reduce the measuring speed and may cause measurement error if it's not aligned properly with the grating. Thus, a new modulating apparatus is proposed to replace the rotary slit used in the Grating-Slit test. In addition, a pellicle beam splitter is used to make the on-axis measurement possible and the measurement error from misalignment is greatly reduced. With a micro liquid crystal display generating and switching the direction of the illuminating grating, we can simultaneously interlace the tip-tilt direction alignments during measurement.

Optical metrology is a science and an art. Education in the engineering disciplines concentrates on technical knowledge transfer. However, creativity and imagination are required in partnership with these technical skills to generate truly innovative results. This presentation investigates strategies and methodologies of working in which the exploration of potential solutions to optical metrology problems becomes more of a creative process than the strict application of technical know-how.

The lateral correlation properties of speckle fields have been shown to be useful in aligning multiple optical channels relative to one another. Relative rotational alignment can also be achieved using a sub-sectioning extension of this technique. In this paper, we examine the three dimensional correlation properties of speckle, and by so doing, create a technique that allows for absolute positioning of a single channel free space optical system on the optical axis without the need for markers or gratings.

Optical encoders are pervasive in many sectors of industry including metrology, motion systems, electronics, medical, scanning/ printing, scientific instruments, space research and specialist machine tools. The precision of automated manufacture and assembly has been revolutionised by the adoption of optical diffractive measurement methods. Today's optical encoders comprise discrete components: light source(s), reference and analyser gratings, and a photodiode array that utilise diffractive optic methods to achieve high resolution. However the critical alignment requirements between the optical gratings and to the photodiode array, the bulky nature of the encoder devices and subsequent packaging mean that optical encoders can be prohibitively expensive for many applications and unsuitable for others. We report here on the design, manufacture and test of a miniaturised optical encoder to be used in precision measurement systems. Microsystems manufacturing techniques facilitate the monolithic integration of the traditional encoder components onto a single compound semiconductor chip, radically reducing the size, cost and set-up time. Fabrication of the gratings at the wafer level, by standard photo-lithography, allows for the simultaneous alignment of many devices in a single process step. This development coupled with a unique photodiode configuration not only provides increased performance but also significantly improves the alignment tolerances in both manufacture and set-up. A National Research and Development Corporation type optical encoder chip has been successfully demonstrated under test conditions on both amplitude and phase scales with pitches of 20 micron, 8 micron and 4 micron, showing significantly relaxed alignment tolerances with signal-to-noise ratios greater than 60:1. Various reference mark schemes have also been investigated. Results are presented here.

Based on fine optical grating and micrometer, one closed-loop high-precision position control system with two modes has been made. The system is used to control the optical elements moving in two ways. That is, one control mode is automatically control with optical grating feedback system and the other mode is manually control with micrometer. Under the support of conservative PID control algorithm, the precision of the system is up to ±0.1&mgr;m while operating on automatically way, otherwise, the position precision is ±1&mgr;m.

High image quality and complex, refractive optical systems, as those used in remote sensing applications, are, in general, very difficult to be manufactured with the required performance. This can be charged to the high sensitivity of such systems to the fabrication tolerances, mainly concerning the relative alignment of the optical components with respect to each other. When the system does not achieve the expected quality, the puzzle is to identify where the problems lies. This is even worsened when the number of optical elements becomes high. Due to these facts, some misalignment characterization and estimation techniques based on Bayesian estimators and wavefront measurements have been proposed in the literature. This paper is the result of a deep study and investigation of these techniques, with emphasis on an application to an intentionally simple system for the sake of illustration that highlights conceptual issues that could be extended to more realistic, complex optical systems. With this purpose, the sensitivity of the wavefront Zernike coefficients to the misalignment parameters, its use in a parameter estimator design that includes nonlinear terms, the study of the system observability, and a statistical analysis of the estimator performance considering the observation noise are addressed in details. Numerical simulation results for the simple system are shown. We also present insights on how to apply the technique to the alignment of a 11-lens optical system used in the Brazilian remote sensing camera MUX, that will fly on-board the upcoming Sino-Brazilian satellites CBERS 3&4.

The alignment philosophy of the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) is such that the cryogenic changes in the alignment of the science instruments (SIs) and telescope-related interfaces are captured in an alignment error budget. The SIs are aligned to the structure's coordinate system under ambient, clean room conditions using laser tracker and theodolite metrology. The ISIM structure is thermally cycled and temperature-induced mechanical and structural changes are concurrently measured to ensure they are within the predicted boundaries. We report on the ISIM photogrammetry system and its role in the cryogenic verification of the ISIM structure. We describe the cryogenic metrology error budget and the analysis and testing that was performed on the ISIM mockup, a full scale aluminum model of the ISIM structure, to ensure that the system design allows the metrology goals to be met, including measurement repeatability and distortion introduced from the camera canister windows.