Diffraction free arrangement
US4887885A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 4, 1987 |
| Grant date | Dec 19, 1989 |
| Priority date | — |
| Expiry date | Aug 4, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10K11/26
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
Arrangements are disclosed for generating a well defined traveling wave beam substantially unaffected by diffractive spreading. In different embodiments, the beam can be an electromagnetic wave, particle beam, a transverse beam, a longitudinal beam such as an acoustic beam, or any type of beam to which the Helmholtz generalized wave equation is applicable. Pursuant to the teachings herein, a beam is generated having a transverse dependence of a Bessel function, and a longitudinal dependence which is entirely in phaser form, which results in a beam having a substantial depth of field which is substantially unaffected by diffractive spreading. In first and second disclosed embodiments respectively, optical and acoustical beams are generated by placing a circular annular source of the beam in the focal plane of a focussing means, which results in the generation of a well defined beam thereby because the far field intensity pattern of an object is the Fourier transform thereof, and the Fourier transform of a Bessel function is a circular function. In a third disclosed embodiment, a microwave beam is generated by transmitting a coherent microwave beam sequentially through a phase modula…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.