With any kind of precision manufactured assembly, the transformation of a concept into a useful product depends on how well the design has been tailored to suit the available methods of fabrication and inspection. Optics is no exception. The tolerances on the drawing must correlate to a method of fabrication and a method of measurement. Among the topics discussed in this paper will be: 1. Some practical aspects of radius tolerancing. 2. The tolerancing and measurements of lens centration. 3. Thickness tolerances in the optical shop. 4. Why method is often more important than tolerances.
The Autologic Micro-5 CRT phototypesetter employs a vacuum-tensioned web transport wherein type images displayed on a cathode-ray tube are imaged by a lens upon photographic film or paper. A unique servo design utilizing a microcomputer permits character exposure while the media is in motion. An extensive evaluation of type requirements and photographic materials led to an optimized lens design that provides the necessary type acuity and machine speed at moderate cost. A family of optical magnifications are housed in a common lens barrel design, thus maximizing commonality. The Micro-5 can be used to typeset both characters and halftone pictures. It can produce complete camera-ready pages, eliminating traditional pasteup composition. Typefonts are stored digitally upon an integral magnetic disc, and displayed on the CRT utilizing a patented technique.
Designing for high reliability and low maintenance should not be left to just the mechanical aspects of an optical system. Ideally, the optical design itself should strive towards these goals. As an example, we consider an infrared telescope which is intended to cover a moderate field-of-view at fast f# speed. There are a variety of two-element designs that might be considered as design candidates and which will perform well, on paper. The actual performance of a system often depends, however, on how well it can be aligned and how stable the alignment is under adverse environmental conditions. This paper describes a single element design which completely avoids this problem, for there is nothing to misalign. It is a thin aspheric Mangin mirror which has several desirable features in addition to good performance. In some cases the aspheric can be omitted. Representative design examples are shown and discussed.
Historical background is presented of the U.S. Army's requirement for a high performance, lightweight, night vision goggle for use by helicopter pilots. System requirements are outlined and a current program for development of a third generation image intensification device is described. Primary emphasis is on the use of light precision molded, aspheric plastic optical elements and molded plastic mechanical components. System concept, design, and manufacturing considerations are presented.
The design of the Secondary Mirror Subassembly (SMSA) in the 2.4m NASA Optical Telescope is presented. The secondary mirror is a circular disc provided with a shoulder. Three clamps located 120 apart support the mirror shoulder. On one side of the mirror shoulder, a coated graphite-epoxy ring connects the three clamps. Three axial flexures with a low radial compliance extend out from a support platform constructed of coated graphite-epoxy box struts and invar corners, and provide a nominal in-plane zero coefficient of thermal expansion (CTE). In each invar corner piece, a ball joint provides a connection to a six-degree-of-freedom adjustment system that can move the secondary mirror with a high degree of precision in defocus, decenter, and tilt. Thermal controls that maintain structural-element temperature variations within specified limits insure that the SMSA exceeds stability and figure control requirements on the secondary mirror.
The U.S. Army's new M19 binocular, which incorporates an unusual modular assembly concept for simplified maintainability, is currently being produced at the rate of 2,000 per month. In this paper, the origin and development by the Army of the modular concept for this binocular are reviewed briefly and performance requirements are summarized. Following this, the manufacturing engineering approach and implementation developed and carried out by the Optics Division of Bell & Howell Company in producing the M-19 binocular are presented.
Mechanical defects in glass-to--lass bonds have been characterized by optically measuring ultrasonic waves that travel along the interface. Such waves are ideal for the evaluation of interference-fit and adhesive bondline properties because significant interactions occur as the propagating waves sample bondline surface structure and because the effects of these interactions can be observed. Ultrasonic wave interactions with different types of defects at or near the boundary may be theoretically analyzed by considering a generalized model of the interface. In this paper, such theoretical predictions are compared with recent acoustooptical measurements of surface and near-surface defects. Specifically, the model developed by Murty and others consisting of two elastic solids separated by a Newtonian viscous liquid layer of thickness H 0 and viscosity coefficient n suggests several types of behavior if defects are present. First, surface defects cause interface wave scattering and attenuation. This attenuation has been interferometrically measured as a function of void diameter on several glass-to-glass boundariesÃ‚Â° Second, sensitivity to near-surface defects has been observed by optically interacting with the internal interface wave fields on either side of such boundaries. Decreased sensitivity to buried defects has been noted as the ratio of substrate densities decreases. Optical measurements and analytical interface wave behavior are compared for both of these cases.
This paper examines various techniques, both optical and mechanical, that can be used to ensure system performance in high shock situ.tions. From the optical viewpoint, this would involve optimizing system design to improve tolerance to such errors which are inevitable under operational conditions, and designing optical components that are not obviously going to be damaged by those same conditions. Mechanically, consideration must be given to methods of holding lenses, retainers, spacers, and of mounting mirrors and prisms that will provide the design location, as well as not damage the glass as the result of shock-induced elastic deformation of the metal parts.
The design of an operational mount to rigidly secure the primary mirror to its baseplate without the introduction of figure error always proves to be a major task on diffraction limited optical systems. A summary of the design of the Infrared Astronomical Satellite (IRAS) primary mirror mount is given. The mirror was designed to be aligned and tested at room temperature and operated in a zero "g" field at temperatures of 2K. To minimize overstressing, a stiffness requirement of greater than 150 Hz was required for cold launch and room temperature vibration acceptance testing. Additional isolation was required to minimize strains, intro-duced via the mounting base, due to thermal and mechanical distortions.
A projection display system incorporating a CRT driven liquid crystal light valve has been designed for use on various types of naval vessels. The projection unit can be used in either a horizontal plotter configuration or a vertical large screen display. It has been designed to withstand the rigorous environmental requirements of surface ship and submarine applications. The totally water cooled projector consists of two principal optical subsystems, the illumination optical system and the projection optics. Common to both subsystems is the polarizing beamsplitting prism which acts as both polarizer and analyzer. Since the light valve operates in linearly polarized light, extreme care has been taken in mounting the prism such that undue stress is not induced in the glass while at the same time maintaining the integrity to withstand all shock and vibration requirements. Excessive force on the prism leads to stress birefringence which causes contrast degradation and non-uniformity in the projected image. In addition to the prism, the illumination subsystem includes a replaceable prealigned, prefocussed, 550 watt, water-cooled xenon arc lamp module, and optical elements to relay the light to the light valve. The light valve, being a reflective device, then directs the energy through the projection optics. To minimize cabinet size in the horizontal plotter and bulkhead to screen distance in the vertical display, a wide angle folded projection lens was required. Attenuation of light output and night adaptation is accomplished with the use of neutral density and red filters. Operator controls such as light output, focus, centering, and scaling can be remotely actuated.
The planning of scientific field experiments that use delicate optical instrumentation poses a challenge to the designer. At the U.S. atomic test site in Nevada, many experiments are conducted under the most adverse conditions for instrumentation, including extremes of temperature and dust, while the instruments are being installed, aligned, and tested above ground. They are subjected to mechanical shock while being lowered into place deep underground and during the back-filling process. Before being destroyed by the blast, they then must operate in intense radiation fields long enough to transmit their data to a recording station. In this paper we present the design and implementation of the "downhole" portion of a measuring system for gamma rays. Included are three alternative designs for radiation-resistant collimating and condensing lenses, sample cells, turning mirrors, and fiber-optic termination techniques. Also discussed are mechan-ical mounts and positioners, shielding, alignment, test methods, and field installation. Some general design suggestions for optical systems in adverse environments are also presented.
This paper discusses the design of a passive isolation system for a high-altitude, long-range oblique reconnaissance camera. The passive isolation system works in conjunction with the active, gyro-stabilized system to attenuate a broad spectrum of vibratory inputs. This paper does not discuss the analytical mechanics applied to the design of the isolation system; that is covered in many texts, some of which are included in the bibliography. It does discuss a design approach, presents mathematical equations and definitions in support of that approach and exhibits some pertinent data.
The ability to produce strain free mounts for metal mirrors is shown to be feasible by the application of four principles: o Mounting strain isolated from mirror surface o Mirror stiffer than mount o Mirror figured in "as mounted" strain condition o Mount tolerances equal to surface tolerances The application of precision diamond machining is shown to be advantageous in applying these principles. Several real mirrors are shown as examples.