Diffraction type filter having a wavelength selectivity

Details Diffraction type filter having a wavelength selectivity Diffraction type filter having a wavelength selectivity

1998-09-29

2000-07-25

Spyrou, Cassandra

Optical: systems and elements

Diffraction

From grating

359566, 369112, G02B 518, G11B 700

Patent

active

060943084

ABSTRACT:
A diffraction grating having a wavelength selectivity is disposed at a peripheral 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. On a glass substrate 10, a first region 11 having no diffraction grating 12A and a second region 12 having diffraction gratings 12A with a rectangular cross section are disposed. The second region 12 comprises linearly arranged diffraction gratings 12A each having a rectangular cross section. The thickness (height) of each diffraction grating 12A is set to such a value that the ratio of .+-.first-order diffracted light is made greater for the light at a wavelength of 780 nm employed for CD-R, whereas the ratio of zero-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: 5363226 (1994-11-01), Strasser et al.
patent: 5682265 (1997-10-01), Farn et al.
patent: 5696750 (1997-12-01), Katayama
patent: 5815293 (1998-07-01), Komma et al.

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