Robert E. Hopkins

Creative Thinking and Computing Machines in Optical Design

Our present optical programs are made up of a group of subroutines which may be used in a large variety of ways. These routines are automatic first- and third-order aberration, fifth-order aberration, ray tracing, energy distribution, and tolerance analysis. The design procedure is to string these routines together into iterative loops. As the design nears completion a high and higher degree of automation is possible. Perhaps the greatest value of the computer is that it enables designers to explore some of their wildest ideas. The program is flexible enough to allow individual differences in the method of approaching the design.

Automatic Correction of Third-Order Aberrations

A method for the automatic correction of third-order aberrations in thick lenses has been tried on several lens problems. The procedure is to use the Newton method for solving the nonlinear equations involved. The derivatives are found by differentiating the third-order surface contribution formulas. The method has proven to be successful on a large variety of lens types.

Some Thoughts on Lens Mounting

The mounting of lenses is a major consideration in the manufacture of lenses. The design of the mount, the material used and the manufacturing methods can all significantly affect the performance, cost and profit margin in lens making. Various methods of mounting will be described and some ideas for improvement will be presented. The suggested improvements are based on the observation that the optical shop is a hostile environment for precision instruments and machines. The grinding materials and liquids are ruinous to precision tools. The one process in lens making that is unique to lens making is the degree of concentration on polishing spherical surfaces. To optimize the manufacturing process one should consider reducing precision requirements as much as possible in all the steps except for the polishing. This thinking leads to looking at new methods of assembly which can be done in clean room conditions. Modern epoxy cements, inch worms, interferometers, and minicomputer control units can be used in assembly to short cut the need for precision lens shaping and tight mounting tolerances.

Some Demonstration Experiments in Optics Using a Gas Laser

Some elementary experiments in geometrical and physical optics, usually limited to individual observations in the laboratory, can be adapted for presentation to larger groups as lecture or classroom demonstrations, by making use of the gas laser as light source. This paper describes several such experiments dealing with lens aberrations, interference and diffraction phenomena, and the Abbe theory of the microscope; together with some practical optical systems for performing them.

Third-Order and Fifth-Order Analysis of the Triplet

A series of triplet objectives have been corrected to the same third-order values and compared by computing the fifth-order aberrations. The calculations show that the most symmetrical solutions have reduced fifth-order coma but have an inward curving, high-order astigmatism.

Re-Evaluation of the Problem of Optical Design

The field of geometrical optics, instrument design and development is undergoing a curious change. Production as measured by the number of units appears to be going steadily downward while activity and interest in special items is rapidly increasing. We face the problem of needing highly advanced techniques, facilities, and special materials without the demand for production. In the past the promise of large production has ensured an advance in the state of the art; with this removed how can we justify the manufacture of such things as special optical glass, expensive aspheric grinding machines, and fifty-layer interference filters? This paper describes the field of geometrical optics and suggests ways in which the computer can help us clearly define our needs and allow us to sharpen up requirements so that the smaller production runs will be of widespread use. Testing and manufacturing techniques are discussed in order to suggest ways of streamlining our efforts.

Some Effects of Glass Choice in Telescope Doublets

A series of air-spaced telescope doublets have been investigated using a least-squares program written for an IBM 650 computer. The effects of glass choice on air space and state of correction are presented, together with some conclusions.

The Problem of Evaluating a White Light Image

The authors have made investigations with Super XX film and find that the resolving power in white light is strongly influenced by the shape and size of the blue and red images. The results indicate that if the imaging characteristics of a lens in white light are to be determined photoelectrically they should be done in at least three wavelength regions. As a by-product of the experiments it was found that the low-contrast resolving power correlated fairly well with subjective picture evaluation.

The Symposium Lens–An Epilogue

A lens design problem was proposed by a group of lens designers. Several alternative designs have been corrected on two different automatic correcting programs. The final designs are similar and exhibit a high degree of correction.

Fiber Optics. Part III. Field Flatteners

A method of field flattening using a bundle of transparent fibers is studied in some detail. Different optical arrangements of field flatteners are proposed and their relative merits are investigated. An improved type of field flattener which also acts as two Fresnel lenses has been developed and the term “Fresnel lens type field flattener” is proposed to denote it. A gain in image quality and weight of a flight periscope system seems possible by the use of such a field flattener. The methods of alignment and fabrication of these field flatteners are described. Working models using 200 μ diameter glass fibers have been constructed which demonstrate the expected gain.