Diffraction type filter having an aberration correction function

Details Diffraction type filter having an aberration correction function Diffraction type filter having an aberration correction function

1998-12-11

2000-12-26

Spyrou, Cassandra

Optical: systems and elements

Diffraction

From grating

359565, 359566, 359571, 369112, G02B 518, G02B 2744, G11B 700

Patent

active

061668540

ABSTRACT:
A zone plate having an aberration correcting function in a wavelength selecting manner and a diffraction grating substantially having a light shielding function in a wavelength selecting manner are formed, respectively, in a center region and a marginal region of a filter, whereby only a predetermined wavelength of light is converged or diverged by the zone plate and is diffracted sideways by the diffraction grating, whereby the luminous flux diameter of the irradiation light is changed while the aberration caused by a convergent lens is favorably corrected. The diffraction type filter 8A is constituted by a first region 11 comprising a central circular portion and a second region 12 comprising a marginal portion thereof. The first region 11 is provided with a zone plate 11A (diffraction grating formed like concentric circles) having such a wavelength selectivity that light at a wavelength of 635 nm is transmitted therethrough as it is and that light at a wavelength of 780 nm is converged thereby. The second region 12 is provided with a diffraction grating 12A having such a wavelength selectivity that light at a wavelength of 635 nm is transmitted therethrough as it is and that a major part of light at a wavelength of 780 nm is diffracted sideways so as to be substantially blocked out.

REFERENCES:
patent: 5161040 (1992-11-01), Yokoyama et al.
patent: 5360973 (1994-11-01), Webb
patent: 5682265 (1997-10-01), Farn et al.
patent: 5696750 (1997-12-01), Katayama
patent: 5815293 (1998-09-01), Komma et al.
patent: 5880879 (1999-03-01), Foo

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