Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specified detail of transducer assembly support structure
Reexamination Certificate
1999-04-19
2001-07-03
Nguyen, Hoa T. (Department: 2652)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specified detail of transducer assembly support structure
Reexamination Certificate
active
06256287
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to optical disk drives for reading and writing information in tracks of a rotating disk and is most closely related to optical lens systems for focusing the scanning beam into a spot on the disk in such optical disk drives.
BACKGROUND OF THE INVENTION
The invention relates to a method of manufacturing an optical lens system including a housing, a first lens element having a first optical axis, and a second lens element having a second optical axis. According to the method, the lens elements, before being secured to the housing, are aligned relative to each other such that the optical axes of the lens elements coincide.
The invention further relates to an optical scanning device for scanning an information track of an optically scannable information carrier. The scanning device includes a radiation source, an optical lens system having an optical axis for focusing a radiation beam supplied, in operation, by the radiation source into a scanning spot on the information carrier, and a first actuator for displacing the lens system in a direction parallel to the optical axis. The lens system includes a first lens element, a second lens element and a second actuator for displacing the first lens element and the second lens element relative to each other.
The invention also relates to an optical player including a table which can be rotated about an axis of rotation, an optical scanning device for scanning an information track of an optically scannable information carrier which can be arranged on the table, and a displacement device which displaces the scanning device, in operation, relative to the axis of rotation, predominantly in a radial direction.
An optical lens system manufactured in accordance with a method of the type mentioned in the opening paragraph, as well as an optical scanning device and an optical player of the types mentioned in the opening paragraphs are known from U.S. Pat. No. 5,712,842. The known optical lens system used in the known optical scanning device includes an objective lens and a relatively small, so-called solid immersion lens, which is arranged between the objective lens and the information carrier to be scanned. By using the solid immersion lens, the known lens system has a relatively large numerical aperture, so that a relatively small scanning spot on the information carrier to be scanned is obtained. As a result, the known scanning device can suitably be used to scan information carriers having relatively small elementary information characteristics, i.e. information carriers having a relatively high information density, such as a high-density CD. Using the first actuator of the known scanning device, the lens system is displaced parallel to the optical axis, thus enabling the scanning spot to be focused on the information layer of the information carrier. Using the second actuator of the known scanning device, the solid immersion lens is displaced relative to the objective lens in a direction parallel to the optical axis, thus enabling a spherical aberration of the radiation beam in a transparent protective layer of the information carrier between the information layer and the scanning device to be corrected.
The objective lens of the known optical lens system is secured to the housing of the lens system in a fixed position, while the solid immersion lens is secured to the housing via a leaf spring. For a good optical operation of the lens system, the optical axes of the objective lens and the solid immersion lens must coincide as much as possible. To achieve this, in the course of the manufacture of the lens system, the objective lens and the solid immersion lens are aligned relative to each other, before being secured to the housing of the lens system, in such a manner that the optical axes of the objective lens and the solid immersion lens coincide as much as possible.
The above citations are hereby incorporated in whole by reference.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method of the type mentioned in the opening paragraphs, by which the lens elements of the lens system to be manufactured can be accurately aligned relative to each other by simple auxiliary apparatus, before they are secured to the housing of the lens system.
To achieve this, at least the first lens element is secured to the housing via two elastically deformable mounting elements. The mounting elements, when viewed parallel to the first optical axis, are arranged at some distance from each other and each individually allow tilting of the first lens element about tilting axes extending perpendicularly to the first optical axis. The mounting elements, when viewed in directions at right angles to the first optical axis, are substantially undeformable. At least one of the mounting elements is displaced, before being secured to the housing, in a direction transverse to the first optical axis to bring the lens elements into mutually parallel positions. In order to bring the lens elements of the lens system into a position in which the optical axes of the lens elements coincide, at least one of the lens elements must be tilted, during the aligning process, about a tilt axis directed at right angles to its optical axis, so that the lens elements are brought into mutually parallel positions, and, during aligning, at least one of the lens elements must be displaced at right angles to its optical axis, so that the lens elements are centered relative to each other. If, before being secured to the housing, at least one of the mounting elements is displaced in a direction transverse to the first optical axis, the first lens element is tilted about a tilt axis directed perpendicularly to the first optical axis, thereby elastically deforming the two mounting elements. Because the lens elements are brought into mutually parallel positions, in the manner described above, by displacing at least one of the mounting elements only in a linear direction transverse to the first optical axis, and that such linear displacements can be carried out with great accuracy, the lens elements can be very accurately brought into mutually parallel positions by a simple manipulator having limited possibilities of displacement. Since, viewed in directions perpendicular to the first optical axis, the mounting elements are substantially undeformable, after securing the mounting elements to the housing, viewed perpendicularly to the first optical axis, a very rigid support of the first lens element relative to the housing is obtained, while the cooperation between the two mounting elements secured to the housing additionally provides for a very high tilt resistance of the first lens element relative to the housing about tilt axes directed at right angles to the first optical axis. In this manner, the mutual positions of the two lens elements obtained during aligning are accurately maintained after securing the mounting elements to the housing.
In a particular embodiment of the method in accordance with the invention, before being secured to the housing, the second lens element is displaced in a direction transverse to the second optical axis in order to center the lens elements relative to each other. Because the lens elements are centered relative to each other, as described above, by displacing the second lens element exclusively in a linear direction transverse to the second optical axis, and that such linear displacements can be carried out with great accuracy, the lens elements can also be very accurately centered relative to each other by a simple manipulator having limited possibilities of displacement.
In a further embodiment, before being secured to the housing, the mounting elements are displaced over equal distances and in a same direction transverse to the first optical axis in order to center the lens elements relative to each other, and over equal distances, in mutually opposite directions transverse to the first optical axis in order to bring the lens elements into mutually parallel positions. The first lens element is dis
Aarts Jan W.
Baartman Jan P.
Altman, III Franklin D.
Nguyen Hoa T.
U.S. Philips Corporation
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