Method and apparatus for photorefractive pirouette display and processing of analog signals
US5612812A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 31, 1995 |
| Grant date | Mar 18, 1997 |
| Priority date | — |
| Expiry date | Aug 31, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03H1/26
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A photorefractive pirouette display device can produce the sonogram of speech sounds by incorporating the short-time Fourier spectrum of speech waves as the input. The device requires a coherent source of optical radiation which can be obtained for a variety of different lasers. A photorefractive circuit is used to display a time-dependent signal, beam. An analog signal is imposed on the beam as temporal modulations on its intensity and/or phase, the pump beam is a plane wave constant amplitude. The signal beam interferes with the pump beam in the photorefractive crystal, the resultant intensity modulation pattern nonuniformly excites the charge carriers in the crystal. The excited charge carrier migrate in the crystal to form a microscope electric field, which produces an index grating in the crystal due to the Pockels effect. The crystal is rotating continually with angular velocity. The pump beam diffracts off of the holographic grating and reconstructs the signal beam. As the crystal rotates, the reconstructed signal beam rotates along a circular ring. In polar coordinates the angle .THETA. specifies a position on the ring. The diffracted light at angle .THETA. at a given time …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.