TABLE OF CONTENTS John C. Stover
TMA Technologies
Bozeman, Montana
| BRDF | bidirectional reflectance distribution function |
| BTDF | bidirectional transmittance distribution function |
| BSDF | bidirectional scatter distribution function |
| f | focal length |
| FN | focal ratio |
| L | distance |
| P | power |
| R | length |
| r | radius |
| TIS | total integrated scatter |
| ? | angle |
| ? N | vignetting angle |
| ? spec | specular angle |
| ? | wavelength |
| ? | rms roughness |
| ? | solid angle |
The measurement of optical scatter has received increased attention in the last decade. In addition to being a serious source of noise, scatter reduces throughput, limits resolution, and has been the unexpected source of practical difficulties in many optical systems. On the other hand, its measurement has proved to be an extremely sensitive method of providing metrology information for components used in many diverse applications. Measured scatter is a good indicator of surface quality and can be used to characterize surface roughness as well as locate and size discrete defects. It is also used to measure the quality of optical coatings and bulk optical materials. It is emerging as a valuable noncontact measurement technique outside the optics industry as well. Point sources of scatter imaged onto position-sensitive detectors are used to measure displacement. Doppler-shifted scatter is used to measure velocity, and polarization changes in scattered light can be used to reveal reflector material properties, such as the optical constants.
The instrumentation required for many of these measurements has to be fairly sophisticated. Scatter signals are generally small compared to the specular beam and can vary by several...
