Scaling laws for light weight optics, studies of light weight mirrors mounting and dynamic mirror stress, and light weight mirror and mount designs

Scaling laws for light-weight optical systems are examined. A cubic relationship between mirror diameter and weight has been suggested and used by many designers of optical systems as the best description for all light-weight mirrors. A survey of existing light-weight systems in the open literature was made to clarify this issue. Fifty existing optical systems were surveyed with all varieties of light-weight mirrors including glass and beryllium structured mirrors, contoured mirrors, and very thin solid mirrors. These mirrors were then categorized and weight to diameter ratio was plotted to find a best curve for each case. A best fitting curve program tests nineteen different equations and ranks a goodness-to-fit for each of these equations. The resulting relationship found for each light-weight mirror category helps to quantify light-weight optical systems and methods of fabrication and provides comparisons between mirror types

Dynamic analysis and design of the SIRTF primary mirror mount

The criteria and considerations for the design of the support system for the Space Infrared Telescope Facility (SIRTF) primary mirror are presented. A flexural-gimbal-baseplate design for the 0.5 m primary mirror was developed. Preliminary studies have indicated that this design may be further improved by replacing the flexures by a post-gimbal system wherein the gimbal design accomodates both the cryogenic cool down effects, the dynamic launch loads, and manufacturing tolerance effects. Additionally, a prestressed baseplate concept had evolved and was presented for the full scale 1.0 m mirror. However, preliminary design studies indicate that this concept will not be required, and the post-gimbal-baseplate design similar to the 0.5 m alternate support system will meet the cryogenic cool down, dynamic launch load criteria, and manufacturing tolerance effects

Mueller Polarimetry for Quantifying the Stress Optic Coefficient in the Infrared

The stress optic coefficient of an infrared transmitting material was measured at room temperature at a wavelength of 1550nm. This work discusses a Mueller matrix imaging experiment to measure the stress optic coefficient, observe the spatial distribution of birefringence, and quantify experimental sources of uncertainty. A one-inch diameter disk of sample material was diametrically loaded with increasing force, and linear retardance was measured in the central region. Finite element and analytical modeling was done to estimate the magnitude of stress in this central region. A Rotating Retarder Mueller Matrix Imaging Polarimeter measured the spatial distribution of linear retardance. The retardance is related to the change in birefringence with stress magnitude. The slope of this linear fit is the stress optic coefficient. The stress optic coefficient of the infrared transmitting material was measured to be 1.89 ± 0.1424 [TPa]−1. To test the precision of our stress optic coefficient measurement procedure, a 1-inch diameter N-BK7 disk was measured at a wavelength of 1550nm and compared with industry-accepted values. The stress optic coefficient of N-BK7 was measured as 2.83 ± 0.1057[TPa]−1. The published N-BK7 value measured at visible wavelengths is 2.77 [TPa]−1 ± 3%.1-3 This agreement validates the experimental Mueller matrix imaging methods and supports the common assumption of minor wavelength dependence of the stress optic coefficient. © 2023 SPIE.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]