Focused optical beam encoder of position
US4899048A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 27, 1987 |
| Grant date | Feb 6, 1990 |
| Priority date | — |
| Expiry date | Apr 27, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/34715
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A light beam, typically 780 nanometer coherent light generated by a laser diode, is focused, preferably by a wide angle graded index optics lens having a numerical aperture of 0.46 and a diameter of 1.8 mm, into a diffraction limited spot, of approximate diameter 0.039 to 0.3 mils, upon an encoder wheel. The encoder wheel is typically a photoetched radial reticular grating on Mylar.RTM. plastic having lines at 0.00025" width at a radius of 1". The focused light beam intercepts the encoder wheel at this 1" radius and is alternately transmitted and obstructed by the reticular grating of the rotating encoder wheel. The selectivity transmitted light beam is received at a detector, typically a phototransistor. Greater than 10,000 transitions per encoder wheel revolution are detectable.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.