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Optical head for scanning record carrier

A carrier and optical head technology, applied in the direction of optical recording head, optical recording/reproduction, system characterized by carrier structure, etc., can solve the problem of high component cost

Inactive Publication Date: 2005-08-03
CP MAHK JAPAN
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The disadvantage of this known optical head is that the component costs are rather high due to the presence of the phase structure and the thin-film stack

Method used

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  • Optical head for scanning record carrier
  • Optical head for scanning record carrier
  • Optical head for scanning record carrier

Examples

Experimental program
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Effect test

Embodiment Construction

[0027] figure 1 A device 1 for scanning a first optical record carrier 2 of a first type and a second record carrier 40 of a second type is shown. In the illustrated embodiment, the first type is a digital versatile disc (DVD) and the second type is a writable compact disc (CD). The record carrier 2 comprises a transparent layer 3, on one side of which an information layer 4 is arranged. The side of the information layer facing away from the transparent layer is protected from environmental influences by a protective layer 5 . The side of the transparent layer facing the device is called the input face 6 . The transparent layer 3 acts as a substrate for the record carrier, providing mechanical support for the information layer. Alternatively, the transparent layer also has the function of protecting the substrate of the information layer, while the information layer is mechanically supported by a layer on the other side of the information layer, for example by a protective ...

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Abstract

A device for scanning a first and second type of optical record carriers (2; 40) of different thickness generates a first and a second radiation beam of different wavelengths. The first radiation beam (17) has a first numerical aperture NA1. The second radiation beam (46) has an effective second numerical aperture NA2 smaller NA1. The rays of the second radiation beam having an NA smaller than NA2 form a central sub-beam (48), the rays having a larger NA form an outer sub-beam (49). The device includes a non-periodic phase structure that does not affect the first radiation beam. The introduced spherical aberration compensates the difference in spherical aberration caused by the difference in thickness of the transparent layers (3; 41). To reduce the amount of stray light falling on the detection system (25) from rays in the outer sub-beam (49), the phase structure introduces an amount of defocus in the second radiation beam (17). Which displaces the focus of the central sub-beam with respect to of the outer sub-beam, causing the intensity distribution of the central and outer sub-beam to split in two separate distributions. If the position and size of the detection system are properly chosen, the detection system will capture mainly rays from the central sub-beam and not from the outer sub-beam. Hence, the displacement of the foci allows spatial filtering in the plane of the detection system (25) of the desired and undesired rays of the second radiation beam.

Description

technical field [0001] The invention relates to an optical head for scanning first and second different types of record carriers. The invention also relates to a device for scanning two different types of optical record carriers, said device comprising an optical head. Both types of record carriers have an information layer and a transparent layer through which a radiation beam can scan the information layer. The thickness of the transparent layer is different for the two types of record carriers. The optical head comprises a radiation source for generating a radiation beam having a first wavelength for scanning a first type of record carrier and a second radiation beam having a second different wavelength for scanning a second type of record carrier. The first radiation beam has a larger effective numerical aperture than the second radiation beam for scanning the information layer. Background technique [0002] Advances in the field of optical recording have brought new ...

Claims

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Application Information

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IPC IPC(8): G11B7/1353G02B5/18G11B7/00G11B7/135
CPCG11B7/1374G11B2007/0006G11B7/139G11B7/13922G11B7/1353G11B7/1275G11B11/10543G11B7/0912
Inventor J·E·德弗里斯B·H·W·亨德里克斯
Owner CP MAHK JAPAN