Damage Effects Identified By Scatter Evaluation Of Supersmooth Surfaces

W. Kent Stowell

doi:10.1117/12.943250

4 October 1984 Damage Effects Identified By Scatter Evaluation Of Supersmooth Surfaces

W. Kent Stowell

Proceedings Volume 0487, Physics of Optical Ring Gyros; (1984) https://doi.org/10.1117/12.943250
Event: Physics of Optical Ring Gyros, 1984, Snowbird, United States

Abstract

The surface quality of optics used in an extremely sensitive laser instrument, such as a Ring Laser Gyro (RLG), is critical. This has led to the development of a Variable Angle Scatterometer at the Air Force Wright Aeronautical Laboratories at Wright-Patterson Air Force Base, which can detect low level light scatter from the high quality optics used in RLG's, without first overcoating with metals. With this instrument we have been able to identify damage effects that occur during the typical processing and handling of optics which cause wide variation in subsequent measurements depending on when, in the process, one takes data. These measurements indicate that techniques such as a Total Integrated Scatter (TIS) may be inadequate for standards on extremely low scatter optics because of the lack of sensitivity of the method on such surfaces. The general term for optical surfaces better than the lowest level of the scratch-dig standards has become "supersmooth", and is seen in technical literature as well as in advertising. A performance number, such as Bidirectional Radiation Distribution Function (BRDF), which can be measured from the uncoated optical surface by equipment such as the Variable Angle Scatterometer (VAS) is proposed as a method of generating better optical surface specifications. Data show that surfaces of average BRDF values near 10 parts per billion per steriadian (0.010 PPM/Sr) for 0-(301 = 0.5, are now possible and measurable.

Citation Download Citation

W. Kent Stowell "Damage Effects Identified By Scatter Evaluation Of Supersmooth Surfaces", Proc. SPIE 0487, Physics of Optical Ring Gyros, (4 October 1984); https://doi.org/10.1117/12.943250

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