Abstract
An autofocusing, laser-based system for measuring the surface topography of a spinning optical-quality disk is described. The essential feature of the system is high resolution of absolute surface profiles with large peak to peak variations. Illustrative experimental results are presented for glass and plastic disks. Applications of the instrument to surface accelerations and thickness measurements are also discussed.
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Abbreviations
- θ:
-
angle between focus spot and datum on the disk
- \(\mathop \theta \limits^ \bullet \) :
-
angular speed of disk (sled stationary)
- S :
-
change in focal position
- T :
-
disk thickness
- β:
-
focus cone semi-angle in the disk material
- ϕ:
-
focus cone semi-angle in air
- n :
-
index of refraction of disk material
- δ:
-
surface position relative to datum
- \(\mathop \delta \limits^{ \cdot \cdot } \) :
-
surface/objective acceleration
- e :
-
focus-error signal
- t :
-
time
- r :
-
radial position of focus spot on disk
References
Bricot, C. Lehureau, J.C. andPuech, C., “Optical Readout of Videodisc,”IEEE Trans. on Consumer Electronics,22,304–308 (1976).
Lagace, L.J. and Kissinger, C.D., “Non-Contact Displacement and Vibration Measurement Systems Employing Fiber Optic and Capacitance Transducers,” 23rd Inter. Instr. Symp. of the ISA, ISBN 87664-362-4 (1977).
Menadier, C., Kissinger, C. andAdkins, H., “The Fotonic Sensor,”Instruments and Control Systems,40,114–120 (1967).
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Wagner, J.G. A system for measuring the surface profile of a spinning disk. Experimental Mechanics 22, 296–301 (1982). https://doi.org/10.1007/BF02327247
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DOI: https://doi.org/10.1007/BF02327247