Optical designs for phased-array imaging telescopes, and for interferometers with sparsely filled apertures, using simple two-mirror subtelescopes are discussed. Limitations to the field of view caused by Petzval curvature and distortion are discussed. Methods for reducing or correcting Petzval curvature in these systems by the use of off-axis paraboloidal mirrors are presented and design examples are given. It is shown that a 2.4 times increase in the field of view is possible for 10m diameter arrays, but that residual distortion precludes application of the method to the 50m diameter interferometers considered.
This paper concerns a new, machine mounted aspheric metrology device designed to measure a broad range of figures without the use of auxiliary optics. A prototype device, based on the classical Hartmann test, called a Hartmann Optical Surface Tester (HOST) was evaluated on a single point diamond turning machine. Design, initial testing, and validation data from reference spheres, and two types of aspheres are discussed. Results of a simulation model for estimating acceptable alignment errors for the HOST on the diamond turning machine also are presented. Peak-to-valley measurement uncertainty on the test optics was found to be better than 0.08 micrometers .
Recent advances in axial gradient material fabrication via the diffusion of glass plates has opened the door to a wide variety of optical design applications incorporating entire lenses of gradient index material. A proprietary software-driven process developed at LightPath Technologies Inc. creates gradient index glass by fusing together a stack of discrete glass plates, where each constituent plate has a distinctive composition and desired optical properties. LightPath's ability to prescribe large optical index changes (up to 0.47) throughout a glass substrate of virtually any diameter and thickness (macro gradient), invokes an interesting question: what are the properties of a solid gradient index lens and how can these properties be used most efficiently and effectively? This paper reports on a parametric study of third order spherical aberration vs. shape factor, for a macro gradient F/3 singlet lens whose index varies by +/- 0.4 in linear, quadratic and cubic profiles.
Designs for phased-array imaging telescopes covering a wide field of view (0.25 degrees) with satisfaction of all optical phasing conditions have been developed. Important concerns regarding the implementation of these telescopes include misalignment types and tolerances, and the complexity of active alignment systems needed to correct the misalignments. In this paper a phased-array telescope point design is briefly described. Possible misalignments in the array configuration are defined, and functional forms are given. A technique is introduced for including array misalignments in the wavefront aberration polynomial used to describe image quality in the final array focal plane. This polynomial is then used to show to what extent the misalignment-induced subtelescope aberrations defocus and coma may be corrected using only adjustments in the array configuration. Application to the point design shows that defocus and coma may be corrected, by the addition of piston and tilt terms, by factors equal to the ratio between the Seidel aberration coefficient and the corresponding Zernike polynomial coefficient. It is shown that correction possibilities result in looser subtelescope alignment tolerances and in the simplification of active alignment systems for individual subtelescopes.
The design for a telescope is presented which calls for small optical components in an all-reflective wide-field-of-view phased-array configuration. Attention is given to the geometric phasing conditions and other phasing requirements for the phased-array design, and analytical expressions are set forth for the paraxial relations and distortion. The design of the subtelescopes is based on a three-mirror design, and particular attention is given to the problem of subtelescope field curvature. It is shown that several configurations provide the required corrections for the field curvature and the stigmatic aberrations. Subtelescope aberrations such as coma can affect optical phasing, which indicates that a tolerance analysis conducted aberration-by-aberration is necessary for developing the all-reflective configuration.