Robert R. Shannon

Fabrication of Aspherics Using a Mathematical Model for Material Removal

A mathematica model has been developed that predicts the aspheric surface that a typical optical surfacing machine will produce. The model, which combines two basic assumptions concerning material wear with the kinematics of the machine, has been verified experimentally for the grinding process. In regions of the surface where the tool extends beyond the edge of the workpiece, pressure becomes nonuniform, and the model must be altered. The established model has been used to synthesize those machine strokes required to produce a desired aspheric surface.

Zoom lens design using lens modules

An initial design containing the first- and third-order properties of the four-group video camera zoom system using lens modules and its real lens design are presented. The optimum initial design with focal length range of 6.1693 to 58.4065 mm is derived by assigning appropriate first-order quantities and third-order aberrations to each module along with the specific constraints required for optimization. By thirdorder aberration theory, a real lens for each group has been analytically designed to match the first-order quantities and third-order aberrations at a given conjugates, and then combined to establish an actual zoom system. The combination of the separately designed groups results in a system that satisfies the properties of the zoom system consisting of original lens modules. As a result, we obtain a zoom system useful in video zoom camera employing the rear focus method.

Reflecting Schmidt imaging spectrometers

A new very wide angle imaging spectrometer optical configuration which uses an all-reflecting Schmidt camera with a prism spectrometer to give a strip field of view is presented. Three complete systems (15 degrees, 8.5 degrees, 2.6 degrees FOV), including fore optics and spectrometer optics, were designed. These slit fields of view are pushbroomed across object space to create a 2-D image. The performance of each near diffraction-limited system and optical prescriptions is detailed. An all-reflecting Schmidt camera fore-optics system with a 60 degree field of view is also given.

Overview of conformal optics

Applications of optics have traditionally conformed to the difficulties and limitations imposed by the practical limits on designing and fabricating optical systems. The operational efficiency of devices, especially military systems, has frequently been compromised by the need to accommodate an adverse environment in a non-optical manner.

Currency features for visually impaired people

The estimated 3.7 million Americans with low vision experience a uniquely difficult task in identifying the denominations of U.S. banknotes because the notes are remarkably uniform in size, color, and general design. The National Research Councils Committee on Currency Features Usable by the Visually Impaired assessed features that could be used by people who are visually disabled to distinguish currency from other documents and to denominate and authenticate banknotes using available technology. Variation of length and height, introduction of large numerals on a uniform, high-contrast background, use of different colors for each of the six denominations printed, and the introduction of overt denomination codes that could lead to development of effective, low-cost devices for examining banknotes were all deemed features available now. Issues affecting performance, including the science of visual and tactile perception, were addressed for these features, as well as for those features requiring additional research and development. In this group the committee included durable tactile features such as those printed with transparent ink, and the production of currency with holes to indicate denomination. Among long-range approaches considered were the development of technologically advanced devices and smart money.

Deformable primary mirror for a space telescope

A 4-m aperture deformable primary mirror has been designed with the mirror and its supports integrated into a single structure. The integrated active mirrors minimal weight makes it desirable for a space telescope as well as a terrestrial application. Utilizing displacement actuators instead of force actuators, the active controls at the mirrors surface include normal position control and slope control in both the radial and tangential directions at each of forty control points. Influence functions for each of the controls are nearly independent, reducing the complexity of the control system. Experiments with breadboard models verify the structural concept and the techniques used in the finite element method of computer structural analysis. This paper describes the results of finite element analyses.

Optimization of waveguide coupling lenses with optical design software.

We show that the coupling efficiency of an optical system to a waveguide can be related to an apodized and normalized point spread function. Adapting the problem to the use of optical design software, we analyze and optimize systems that contain a fair amount of aberration. We compare theoretical predictions with experimental results and obtain good agreement.

Lens design using a minimum number of glasses

Due to the increasing environmental limitations imposed on the chemical materials used in optical glass production, there is now an economic desire to minimize the number of glasses used in lens design. This paper presents the results of a study to create a glass listing that contains the minimum number of glasses needed for most lens designs. A double Gauss lens is used in the glass selection process. As part of this study, the relationship between the error function and the number of glasses chosen, as defined by a glass-count study, is found, as is the relationship between the error function and the location of a particular glass, as defined by glass-range study. Three lens libraries were studied using the global optimization method, and the most frequently chosen glasses were then compiled into the recommended glass listing according to the glass-count and glass-range studies. A recommended glass listing with nine glasses constructed from this study is presented.

Spectral plots for optical glass selection

Plots of the index of refraction and of partial dispersion versus V-number have long been used as a standard tool in selecting glasses for chromatic correction. The change in the distribution of glasses on these plots for widely differing spectral regions has generally been ignored. Some sample plots demonstrate the adjustments in approach required for selecting glasses in alternative spectral regions.

Teaching lens design

Lens design is one of the most basic activities in optical engineering. The subject requires an active working knowledge of all aspects of optics, and is a profession changing with the rise of new techniques in modern optics. The approach to teaching the subject is discussed, and the changes that have taken place over the past few decades are described.