Laser heterodyne surface profiler
US4353650A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 16, 1980 |
| Grant date | Oct 12, 1982 |
| Priority date | — |
| Expiry date | Jun 16, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J9/04
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus is disclosed for testing the deviation of the face of an object from a flat smooth surface using a beam of coherent light of two plane-polarized components, one of a frequency constantly greater than the other by a fixed amount to produce a difference frequency with a constant phase to be used as a reference. The beam also is split into its two components with the separate components directed onto spaced apart points onthe face of the object to be tested for smoothness. The object is rotated on an axis coincident with one component which is directed to the face of the object at the center which constitutes a virtual fixed point. This component also is used as a reference. The other component follows a circular track on the face of the object as the object is rotated. The two components are recombined after reflection to produce a reflected frequency difference of a phase proportional to the difference in path length which is compared with the reference phase to produce a signal proportional to the deviation of the height of the surface along the circular track with respect to the fixed point at the center.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.