Input device using laser self-mixing velocimeter
US7557795B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 30, 2005 |
| Grant date | Jul 7, 2009 |
| Priority date | — |
| Expiry date | Mar 12, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S17/58
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An input device encodes motion using a laser self-mixing velocimeter. The laser beam is directed at a disk or other moving member. As light from that beam is reflected back into the emitting cavity of the laser, the beam power output fluctuates because of the self-mixing effect and generates a beat signal. The beat signal frequency is used to determine the speed of the member's motion. The direction of motion is also determined based on the beat signal. A difference frequency analog phase locked loop filters the beat signal. A zero-point control disables motion detection when the average beat signal amplitude falls below a threshold. A triangle modulator generates a triangle wave for the laser bias current, with the triangle wave frequency being a submultiple of the beat signal frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.