Diffraction grating rhombs, consisting of two identical gratings, are commonly used as laser beam sampling components exhibiting no angular dispersion. Three conditions must be strictly maintained if two gratings placed in series are to form a grating rhomb: the grating substrates must be parallel, the gratings must be rotated in their own planes so that the grooves are parallel, and they must have equal periods. The detailed behavior of grating rhombs is investigated by cascading the grating equation. The shift-invariant property of diffraction gratings in direction cosine space is utilized to describe "conical" (out-of-plane) diffraction behavior. A detailed grating rhomb alignment sensitivity analysis has been performed and sensitivity curves illustrate the effects of misalignments. An interferometric alignment procedure is also discussed.

The Nova laser, presently under construction at Lawrence Livermore National Laboratory, will be capable of delivering more than 100 kJ of focused energy to an Inertial Confinement Fusion (ICF) target. Operation at the fundamental wavelength of the laser (1.05 Am) and at the second and third harmonic will be possible. This paper will discuss the optical alignment systems and techniques being implemented to align the laser output to the target at these wavelengths prior to each target irradiation. When experiments require conversion of the laser light to wavelengths of 0.53 μm and 0.35 μm prior to target irradiation, this will be accomplished in harmonic conversion crystals located at the beam entrances to the target chamber. The harmonic alignment system will be capable of introducing colinear alignment beams of all three wavelengths into the laser chains at the final spatial filter. The alignment beam at 1.05 μm will be about three cm in diameter and intense enough to align the conversion crystals. Beams at 0.53 μm and 0.35 Am will be expanded by the spatial filter to full aperture (74 cm) and used to illuminate the target and other alignment aids at the target chamber focus. This harmonic illumination system will include viewing capability as well. A final alignment sensor will be located at the target chamber. It will view images of the chamber focal plane at all three wavelengths. In this way, each beam can be aligned at the desired wavelength to produce the focal pattern required for each target irradiation. The design of the major components in the harmonic alignment system will be described, and a typical alignment sequence for alignment to a target will be presented.

A theory has been developed for representing fabricated optical components by a set of easily identified local coordinate systems linked by physically relevant stationary pivot points. The use of stationary pivot modeling has many advantages when attempting to make performance predictions on complex optical systems during the fabrication and assembly process. In this paper, the basic techniques for modeling fabricated optical components by stationary pivots are developed and some applications discussed.

This report on the Laser Optical Line of Sight (LOLOS) project developed at Lawrence Livermore National Laboratory presents the technical portion of the development of a multidetector alignment system, including the final design, key calculations, and a summary noting critical technical issues.

The Kern Electronic Coordinate Determination System (EGOS-1) is based on the philosophy that a digitally-based theodolite system can lower the cost of measurements in both the fabrication and inspection phases of large jigs, tools and parts. This philosophy assumes a desire on the part of the user to subject each project to rigorous control, from a management as well as a technical perspective. The Kern ECDS-1 package and its programs for job management, orientation, data collection and special function analysis of coordinate measurements are discussed.

Precision optical alignment and/or measurement more often than not requires coordinate systems which for convenience of analysis are not based on a gravity reference system. Conventional jig transits, telescopic transit squares and optical transit squares which rely on a gravity reference system require that measurements be taken from. plumb lines (vertical planes) and level lines (horizontal planes). If the object being analyzed is not oriented coincident to the earth's xis, then data oust be mathematically reduced by use of trigonometry and geometry formulae which mu be time consuming as well as introduce additional potential errors in analysis. A state-of-the-art optical instrument has been developed which virtually defies gravity and allows rapid. setting of orthogonal pl.H.nes without a gravity reference.

Simultaneous, real time measurements of the relative inclinations of two distinct surfaces is the domain of the Brunson instrument Model 653DR Dual Axis Differential Electronic Level. A. gravity-referenced, two axis instrument, it allows communication between itself and a like, remote unit to establish a comparison between two planes, regardless of their horizontal or vertical separation. The performance and functions of the 653DR. as a static r dynamic monitoring or alignment instrument used as an alternative to more cumbersome, slower methods previously accepted are discussed. Included are the usefulness of data averaging; display of local, remote, or differential sensor data; selectable bandwidth. (or response damping); and comparison of the rate of tilt (angular velocity) of the two sensors. Applications such as the static monitoring of large structures including buildings, dams, ships, and aircraft are suggested. Also discussed are alignment applications in static or dynamic environments such as waterborne alignment of shipboard navigational systems, where the transference to remote locations of the attitude of a master plane referenced to the sips structure is critical.

Although the technology of alignment telescopes for use in the visible region of the spectrum is well developed, there are currently no such instruments usable in the infrared. We have developed a design that operates over a wavelength range of from 2.2 to 12 micrometers, and which employs several unusual techniques to deal with problems associated with making precise measurements at infrared wavelengths.

Alignment of the Nova laser requires control of hundreds of optical components in the ten beam paths. Extensive application of computer technology makes daily alignment practical. The control system is designed in a manner which provides both centralized and local manual operator controls integrated with automatic closed loop alignment. Menu-driven operator consoles using high resolution color graphics displays overlaid with transparent touch panels allow laser personnel to interact efficiently with the computer system. Automatic alignment is accomplished by using image analysis techniques to determine beam reference points from video images acquired along the laser chain. A major goal of the design is to contribute substantially to rapid experimental turnaround and consistent alignment results. This paper describes the computer-based control structure and the software methods developed for aligning this large laser system.

An essentially analogic approach with DC motors is proposed for the optimization of the excitation of an optical waveguide with a light source when the two components are not in mechanical contact.

An automatic motorized system is presented. It is based on an essentially analogic approach and the use of DC motors. The electronics and mechanics have been designed for assembling optical components that must be in mechanical contact.

The Point-Diffraction Interferometer (PDI) forms a spherical reference wavefront at the image of a point source, as produced by some optical system under test, by diffraction at a point-like discontinuity. The reference wavefront interferes with the directly transmitted light, forming an interference pattern that represents a direct and accurate measure of the wavefront aberration. Fringe visibility can approach unity by appropriate design of the interferometer. These principles and performance characteristics are briefly reviewed. By virtue of its operation, the PDI provides precise information about the location of an image relative to the interferometer aperture, with measurement precision intrinsic to two-beam interferometry. It is shown that high internal and external alignment precision of an optical system is possible using a PDI.

Various phases of ground testing of orbiting, object-scanning mapper telescopes require a high degree of alignment accuracy between the telescope under test and a bench collimator which simulates an earth scene. Alignments must be measured under transient conditions, during an interval in which the scanned ground image passes across the telescope's focal plane array (FPA). Alignment accuracies at microradian levels have been obtained over several rotational degrees of freedom by printing out patterns of detector signal versus time obtained from selected detectors as the scene image passes across the FPA. Although this technique was developed specifically for testing the Thematic Mapper (TM), it may be found useful in aligning and testing other kinds of scanning telescopes.

The Sensor Technology Department of Lockheed Missiles & Space Company is an electro-optical technology, device development, and hardware production organization. Novel metrological need causes an electro-optical sensor development to occur. The measurement requirement is defined and a concept is proposed. That concept is often developed into a device which demonstrates that it will solve the problem and acquire the required data. The long coherence lengths associated with lasers has been instrumental in the development of several novel and extremely sensitive devices.

Continued increase in performance and resolution for pointing and tracking hardware aboard spacecraft have required precise knowledge of their behaviour in, and response to, the thermal vacuum environment. This paper discusses acquisition of this type of knowledge by both line-of-site and interferametric methods. Results of the applications of both methods are reported, along with discussions of overall resolution and error, as well as possible difficulties which arise when these techniques are used. The line-of-site method is an autocol-limating technique employing digital theodolites. The interferanetric technique is an integration of off-the-shelf modular optical units into a multichannel laser interferameter. Both of the techniques are immune to movement between instruments outside the vacuum chamber, and targets inside.

Optical systems with tilted and decentered components are being constructed on an ever-larger scale. In its simplest form such a system consists of many flat and spherical elements that are tilted and decentered about a central reference line, creating a rotationally symmetric array of subapertures. The final alignment accuracy largely depends on the precison with which the elements in a sector can be aligned to an arbitarily selected local reference line and to a global coordinate system. The alignment procedure must consider for practical reasons the use of standard optical test techniques performed with commercially available equipment. The techniques are based on autocollimation and boresighting, and the instrumentation used to project the test beams should be fundamental optical tooling or test instruments and surveying equipment. The alignment procedures are performed on an array of over 207 optical elements, which are arranged in rotational symmetry in a large vacuum/pressure vessel (power amplifier) as part of the Antares Laser at the Los Alamos National Laboratory. The optical train of each sector (subaperture) is dissected into discrete functional longitudinal segments, for each of which an alignment theory is developed using functional alignment and quasi-alignment as overriding philosophies. The optical path must duplicate or approximate the path of the operational device over the range of the segment being aligned. To facilitate the techniques, we project alignment reference beams along the optical axes of the individual components and add auxiliary reference targets, reflectors, or simple modifications to standard instruments.

A review of the operational performance of the alignment system for the large Antares optical system is presented. The alignment of twenty-four optical channels consisting of two hundred optical elements is verified and established as required prior to each target shot for this CO₂ laser fusion test facility. The overall system design included features such as automatic operation, data base driven controls, self calibration, provisions for initial optical alignment set up, and system aided fault location. The system approach employed two alignment stations which sequentially viewed the 24 optical channels (sectors) and could be used for prealignments and calibrations. Closed loop operations via the computer permit rapid mirror alignments. The performance of the applied techniques and devices is evaluated and compared to the required performance specifically from the standpoint of accuracy and shot rate. Overall system performance with verification by actual target shots is presented.

Over the years, the optical system of the submarine periscope has become increasingly more complex. Earliest systems consisted of two simple telescopes arranged such that one could view the output of the other. The visual mode was the only mode, thus the degree of precision called for in the alignment and collimation of the optical components was not great. Today's systems may contain from two to four choices of magnification and, in addition to the basic visual mode of operation, the system may contain a varied array of subsystems including; photographic, television, night viewing and laser rangefinder. Obviously, the procedures and degree of precision to be encountered have become proportionately more sophisticated. This paper will present a brief review of this history and a detailed discussion of contemporary systems and the alignment procedures being employed to assure their satisfactory performance.

A major limitation on the performance of lenses is the accuracy with which the elements can be centered. Most methods for alignment of lens elements require rotation of the elements in a precision bearing. Small lenses are difficult to manipulate with precision while mounted in a rotating bearing. A method is described which does not need rotation to center the elements. The advantages and requirements of such systems are analyzed.

The Los Alamos Meson Physics Facility (LAMPF) consists of a linear accelerator with multiple target systems, where the particle beam is being switched into separate channels to be aimed at discrete terminals to perform a variety of functions. The beam is always enclosed in an evacuated pipe with directional changes following simple geometric patterns along vertical or horizontal reference lines. Beam steering and focusing is accomplished with magnets surrounding the evacuated beam tubes. In a novel application it was necessary to cut into an existing beam tube and add a line which was to be skewed in a compound angle to clear the existing equipment and fit into the limited space provided in the beam tunnel. Alignment of the skewed beamline was accomplished by setting optical reference lines and planes to calculated beam centerlines and positioning the beam pipes and most magnets to these references using special centering fixtures. This paper describes the combined use of the optical tooling and surveying technology as applied to the marking of the components and positioning of subassemblies in the reference grid. Auxiliary targets and alignment fixtures were developed to facilitate the unique procedures and are described. Design and measured alignment tolerances are compared.