Optical head for scanning a record carrier

Details Optical head for scanning a record carrier Optical head for scanning a record carrier

2005-10-18

2005-10-18

Miller, Brian E. (Department: 2652)

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

C369S112110

Reexamination Certificate

active

06956807

ABSTRACT:
A device for scanning a first and second type of optical record carriers (2; 40) generates a first and a second radiation beam for scanning the first and second type of record carriers, respectively, the first radiation beam having a first numerical aperture larger than the second numerical aperture of the second radiation beam. The device includes a non-periodic phase structure that does not affect the first radiation beam. The phase structure introduces an amount of spherical aberration in the second radiation beam for scanning the second type of record carriers for compensating the difference in spherical aberration required for scanning through the different thickness of the transparent layer (3; 41) of the first and second type of record carriers (2, 40). To reduce the amount of stray light on the detection system (25) from rays in the second radiation beam having a numerical aperture larger than the second numerical aperture, the phase grating introduces a discontinuity in the gradient of the wavefront deviation it introduces in the second radiation beam. The discontinuity allows spatial filtering in the plane of the detection system (25) of the desired and undesired rays of the second radiation beam.

REFERENCES:
patent: 5696750 (1997-12-01), Katayama
patent: 6166854 (2000-12-01), Katsuma
patent: 6201780 (2001-03-01), Katayama
patent: 6370103 (2002-04-01), Yamazaki et al.
patent: 6449095 (2002-09-01), Ohtaki et al.
patent: 6594222 (2003-07-01), Maruyama
patent: 6636365 (2003-10-01), Saito et al.
patent: 6760295 (2004-07-01), Maruyama
patent: 2002/0003767 (2002-01-01), Ota et al.
“Dual Wavelength Optical Head with a Wavelength Selective Filter for 0.6- and 1.2-mm-Thick-Substrate Optical Disks”, by R. Katayama et al., Applied Optics, vol. 38, No. 17, Jun. 10, 1999, pp. 3778-3786.

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