Optical: systems and elements – Lens – With support
Reexamination Certificate
2002-04-15
2003-12-16
Dang, Hung Xuan (Department: 2873)
Optical: systems and elements
Lens
With support
C359S820000, C396S526000, C362S455000, C353S100000
Reexamination Certificate
active
06665132
ABSTRACT:
The invention relates to an optical lens system for use in an optical scanning device for scanning an optically scannable record carrier, which lens system comprises a first lens, a second lens, which is relatively small in comparison with the first lens and, in operation, is positioned between the first lens and the record carrier, and a lens holder accommodating the two lenses.
The invention also relates to an optical scanning device for scanning an optically scannable record carrier, which scanning device comprises a radiation source, an optical lens system having an optical axis for focusing a radiation beam supplied, in operation, by the radiation source to a scanning spot on the record carrier, and an actuator for displacing the lens system parallel to the optical axis, the lens system comprising a first lens, a second lens, which is relatively small in comparison with the first lens and, in operation, is positioned between the first lens and the record carrier, and a lens holder accommodating the two lenses.
The invention also relates to an optical player comprising a table which is rotatable about an axis of rotation, a displacement device and an optical scanning device for scanning an optically scannable record carrier which can be placed on the table, the scanning device comprising a radiation source, an optical lens system having an optical axis for focusing a radiation beam supplied, in operation, by the radiation source to a scanning spot on the record carrier, and an actuator for displacing the lens system parallel to the optical axis, the lens system comprising a first lens, a second lens, which is relatively small in comparison with the first lens and, in operation, is positioned between the first lens and the record carrier, and a lens holder accommodating the two lenses, at least the lens system of the scanning device being displaceable by means of the displacement device substantially in a radial direction relative to the axis of rotation.
An optical lens system, an optical scanning device, and an optical player of the types referred to in the opening paragraphs are known from EP-A-0 863 502. The first lens of the known lens system is a main lens or objective lens, whilst the second lens is a relatively small auxiliary lens which, in operation, is positioned between the main lens and the record carrier to be scanned. By using the auxiliary lens, the known lens system has a relatively large numerical aperture. As a result, the radiation beam, which, in operation, is generated by the radiation source of the known optical scanning device in which the known optical lens system is used, is focused by the lens system to a relatively small scanning spot on the record carrier. The known scanning device and the known optical player, in which the known scanning device is used, are thus suitable for scanning record carriers having relatively small elementary information characteristics, i.e. record carriers having a relatively high information density. The known scanning device and the known optical player are therefore particularly suitable for scanning record carriers in accordance with the so-termed DVR-system. The two lenses of the known optical system are made of glass. Upon manufacture of the optical lens system, the two lenses are separately arranged in the lens holder. In order to obtain an adequate optical accuracy of the lens system, the optical axes of the two lenses must coincide within predetermined, relatively close tolerances. In order to obtain such accurate positions of the lenses in the lens holder, the two lenses must be aligned relative to each other by means of suitable aligning tools during assembly of the lens system.
One drawback of the known lens system, the known optical scanning device and the known optical player is that the assembly of the lens system is relatively complicated, because the lens system comprises at least three separate parts, i.e. the lens holder and the two lenses, each of which needs to be produced separately first, and because the two lenses must be aligned relative to each other.
It is an object of the invention to provide an optical lens system, an optical scanning device and an optical player of the types referred to in the opening paragraphs, in which the lens system can be manufactured in a considerably simplified manner, whilst the lens system has an optical accuracy which, also in operation, is at least as high as the optical accuracy of the known lens system.
In order to achieve this object, an optical lens system according to the invention is characterized in that the lens holder and one of the two lenses are manufactured as one single integrated part from a transparent synthetic material by means of a moulding process, whilst the other lens is arranged in the integrated part as a separate component, with a chamber enclosed by the two lenses and the lens holder communicating with the environment of the lens system via an air vent connection.
In order to achieve this object, an optical scanning device according to the invention is characterized in that the lens system used therein is an optical lens system according to the invention.
In order to achieve this object, an optical player according to the invention is characterized in that the optical scanning device used therein is an optical scanning device according to the invention.
Since the lens holder and one of the two lenses are manufactured as one single integrated part from a transparent synthetic material by means of a moulding process, with the other lens being arranged as a separate component in the integrated part, only two parts need to be mutually assembled during assembly of the lens system according to the invention. The integrated part can be manufactured in a very accurate manner by means of the moulding process. The integrated part may be provided, for example, with a lens mount and/or a positioning surface for the other lens being accurately positioned with respect to the integrated lens, so that the other lens can be accurately positioned with respect to the integrated lens in the integrated part in a very simple manner. This leads to a considerable simplification of the assembly of the lens system according to the invention and obviates the need to align the lenses relative to each other. Since the chamber enclosed by the two lenses and the lens holder communicates with the environment of the lens system via an air vent connection, an increase of the air pressure in the aforesaid chamber is prevented in operation. Without the use of the air vent connection, such an increase of the air pressure would result from an increase of the ambient temperature of the lens system. Since the integrated lens of synthetic material is considerably less stiff than a lens which is made of glass, such an increase of the air pressure would lead to deformations of the integrated lens, which in turn would lead to an unacceptable decrease of the optical accuracy of the lens system. Since such deformations of the integrated lens are prevented in this manner, the lens system according to the invention has an optical accuracy which, also in operation, is at least as high as the optical accuracy of a lens system which only comprises glass lenses. Another advantage of the lens system according to the invention is the fact that the lens system has a relatively low mass, due to the use of the lens of synthetic material. In a special embodiment of the lens system according to the invention, said mass is further reduced by making the other lens of synthetic material as well. This leads to a considerable reduction of the forces required for displacing the lens system, as a result of which the scanning speeds of the scanning device and the player according to the invention can be considerably increased.
A special embodiment of an optical lens system according to the invention is characterized in that the integrated part comprises the lens holder and the second lens. Since the second lens is relatively small in comparison with the first lens, the second lens in itself would be
Hendriks Bernardus Hendrikus Wilhelmus
Van Der Vleuten Cornelius Antonius Nicolaas Maria
Van Dorst Fransiscus Christiaan
Van Gaal Fransiscus Marinus Andrea Maria
Belk Michael E.
Dang Hung Xuan
Martinez Joseph P
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