D1.1 - Speckle-Insensitive Laser-Doppler Vibrometry with Adaptive Optics and Signal Diversity
- AMA Conferences 2015
2015-05-19 - 2015-05-21
- Proceedings SENSOR 2015
- D1 - Optical Metrology
- C. Rembe - TU Clausthal, Clausthal-Zellerfeld (Germany), A. Dräbenstedt - Polytec GmbH, Waldbronn (Germany)
- 505 - 510
Phase noise and signal drop-outs by laser-speckle are the dominant limitations for the resolution of laser-Doppler vibrometers while measuring on rough surfaces of mechanic-engineering parts. For a long time laser-speckle effects have been accepted to be an unsolvable problem that can only be treated with bandwidth limiting signal-processing filters. Recent publications show now that this perception can be conquered with methods from adaptive optics and signal diversity. The paper discusses the possibility to introduce adaptive optics with spatial light modulators in order to maximize the signal strength of a laser-Doppler vibrometer. The other solution discussed in this paper is based on signal diversity as it is known from radar technology. Several sub-apertures which detect different angular speckles and a special polarization detection scheme allow obtaining different signals from independent speckles. The possibilities and limits of the two approaches are explored. The conclusion of the paper is that speckle-insensitive laser-Doppler vibrometry is feasible.