This year people want to know what real place is there for replica optics in components and systems, and also in the market place. This paper addresses a sharp concern for the actual utility of replication as a viable process for designers and fabrication experts. What replica optics are actually being made? How does one identify a good replication capability? What measures can be made of capability, and what total outcome can be expected? Technical aspects of the replication process are explored, and examples given of components and systems. The design of substrates, tooling, and masters is discussed. Considerations pertinent to scattered light, reflectivity, stability and accuracy are given special treatment.
Replication of large scale optical quality mirrors has been demonstrated to be feasible for the first time in recent development work by Talbert Reflectors. This paper traces the stages of the development process from the author's first thoughts about large lightweight mirrors through pilot production of flight simulator mirrors. Large scale surfaces are possible because high vacuum is not required for fabrication of the optical surface. Sizes to 10 by 14 feet are feasible. Surface shapes are relatively unrestricted--spheric or off-axis aspheric shapes can be produced. Surface accuracies of 0.5 arc minutes per foot slo, e error have been achieved. Surface accuracy testing experience includes investigation of edge trimming, iamage, and creep effects. Lightness in weight and great rigidity are accomplished at relatively low cost by use of an aluminum honeycomb/epoxy-fiberglass substrate. Structural and thermal characteristics can be designed for specific applications. Standard optical coatings may be applied. A recent aluminum coating with an enhanced sili con dioxide overcoat measured 92% at 5500 A and passes both tape and cheesecloth abrasion tests. Applications include flight simulator displays, visual and TV projection systems, solar energy collectors, IR laser systems, millimeter and submillimeter radio reflectors.
A novel method of constructing variable focal length lens employing clear two component room temperature vulcanizing (RTV) silicone rubber is presented. Deformation of the lens is achieved by symmetrically applying pressure through a fluid to a slab of RTV-rubber in such a manner as to change the shape with minimum optical distortion. The theory of deformation of a flexible slab is presented and the optical manifestations predicted. Two different configurations of the variable focal length lens were constructed and experiments performed to measure refraction as well as surface properties. It is found that to first order the theory and experiment agree well. With this theoretical tool expanded to higher orders, new and interesting optical designs should be possible using RTV-rubber lens.
In the manufacture of small primary and secondary replicated mirrors used in tactical missiles one of the most critical decisions is when to accept a master to be used for the replication process. A method has been developed whereby actual measured data on each master can be input to the ACCOS V optical design program so as to appropriately distort the ideal mirror design contour in such a manner as would result from the use of these masters. The resultant image can then be evaluated in terms of blur circle diameter, MTF or whatever other convenient image evaluation criteria one may wish to use. To accomplish this task a program was written to accept the measured data from the masters and translate it into a form compatible with the SPLINE subroutine input format for each mirror. Once this was accomplished normal ACCOS V evaluations were performed. An example is given to demonstrate the steps needed to achieve the above evaluation, including SPLINE curve fitting, interpolation, input sequencing, storage manipulations and image quality evaluation.
Replicated optics won their present acceptance in the commercial sector of the optical industry by having been extensively tested for space and aerospace use. Only by offering beyond the State of the Art hardware in the 1960's for aerospace applications, was it possible for an independent manufacturer to market replicated optics. This paper describes the fact that the choice and preparation of the substrate material for light weight replicated mirrors is the determining factor for satisfactory results, assuming, of course, that the replication process itself is skillfully mastered.
The fabrication of aspheric elements by means of replication has become a very important method of supplying otherwise difficult to produce components. The Schmidt Corrector Plate is a typical example, the major benefit being projection TV for the consumer market. However, prior to this it is necessary to develop an objective test method. This paper describes a laser ray trace method of measuring the aspheric profile to ±5 il and subsequently using the derived coefficients to calculate the system M.T.F.' Using this as the quality criteria an objective test method has evolved. The systems shortcomings are discussed, and it is concluded that a useful production test method has been developed.
Some experience with replicated optics at Hughes: Hughes has many applications for replicated and/or plastic optics. These range from very high rate missile production programs to very low volume, one-of-a-kind, special optical test and evaluation equipment. This paper will discuss optics used in a program representative of each of these extremes. For a high rate example, where low recurring cost is the prime function, the design history of a f/.3 reflector used in the TOW anti-tank weapon's infrared beacon will be presented. More than 160,000 of these units have been produced to date, and the reflector has seen many changes over the years. For a one-of-a-kind, high performance oriented example, two light-weight 6-1/2"x 8-3/4" x 1" replicated 1/6 wave flats, used in a universal wide spectral band scanning radiometer, will be discussed. There will also be discussions of optical acceptance tests and their effects on the product design concepts and their cost effectiveness. In addition, pictures will be shown of the optics installed in their systems, and several TOW reflectors will be passed around for "hands-on" examination.
This paper deals with the various approaches taken to achieve hard overcoats or all dielectric optical thin film multilavers in replicated optics. It concludes that not much can be done to improve on conventional coating methods. The prerequisites for hard dielectric films still are a good vacuum and elevated substrate temperatures. To make these coatings readily available for reflective or refractive replicated components, a suitable release layer has to be found which will be compatible with temperatures of at least 300°C. at 1 x 10-6 torr. In addition, the release layer will have to be resilient enough in order to offer minimum adhesion to high surface tension dielectric stacks of any number of layers.
Transparent plastics, as optical components, are used for many applications to replace more expensive and fragile glass components. The primary disadvantage in the use of plastic optical components is their susceptibility to scratching. This inherent property of plastics limits their applicability. Abrasion resistant surfaces on plastics now being marketed have expanded the applicability of plastics; however, deficiencies still exist. Of major concern are the long high temperature cure, batch process, and the limiting to thick rigid substrates. A flexible, formable, rapid curing abrasion resistant coated plastic film has been developed at the 3M Company. This paper will present the properties and applications for this flexible abrasion resistant coated plastic film.
A large diameter, lightweight elliptical plastic mirror was developed for use with an airborne laser sensor system. The plastic mirror, of moderate optical quality, is about 1/3 the weight and cost of an aluminum mirror of comparable size. This paper discusses the fabrication and optical characteristics of a honeycomb constructed, plastic scanning mirror.