Diffraction type filter having a wave length selectivity

Details Diffraction type filter having a wave length selectivity Diffraction type filter having a wave length selectivity

1998-11-23

2000-07-04

Spyrou, Cassandra

Optical: systems and elements

Diffraction

From grating

359566, 359571, 369112, G02B 518, G11B 700

Patent

active

060847107

ABSTRACT:
A diffraction grating with a wavelength selectivity having one sectional side formed like a step is disposed at a marginal region of a filter, and only a wavelength of light whose luminous flux diameter is to be narrowed is diffracted sideways at the diffraction grating, whereby the luminous flux diameter of irradiation light is changed by a simple configuration without complicating an electric control system or restricting the direction of vibration of the irradiation light, while reducing noise. Disposed on a glass substrate 10 are a first region 11 having no diffraction grating 12A, and a second region 12 having diffraction gratings 12A constituted by long protrusions arranged in parallel at a predetermined pitch, each protrusion being continuous in one direction and having one sectional side formed like a step. The thickness (height) of one step in each diffraction grating 12A is set to such a value that the ratio of 1st-order diffracted light is made greater for the light at a wavelength of 780 nm employed for CD-R, whereas the ratio of 0-order diffracted light becomes substantially 100% for the light at a wavelength of 635 nm employed for DVD.

REFERENCES:
patent: 4940308 (1990-07-01), Debesis
patent: 5682265 (1997-10-01), Farn et al.
patent: 5696750 (1997-12-01), Katayama
patent: 5815293 (1998-09-01), Komma et al

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