Registers – Records – Magnetic
Reexamination Certificate
2001-12-04
2004-06-08
Lee, Michael G. (Department: 2876)
Registers
Records
Magnetic
C235S487000, C360S048000, C360S097010, C360S098060, C360S098070
Reexamination Certificate
active
06745946
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for scanning a disc-shaped information carrier which is provided, near a circumference, with a support element manufactured from a magnetizable material, which device is provided with an electromagnetic system for co-operating with the support element and with a scanning unit for scanning information present on the information carrier, said information carrier, by co-operation between the electromagnetic system and the support element, being positionable with respect to the scanning unit, rotatable about an axis of rotation directed perpendicularly to the information carrier and displaceable along an X-axis directed perpendicularly to the axis of rotation.
The invention also relates to a disc-shaped information carrier which is provided, near a circumference, with a support element manufactured from a magnetizable material, which support element is used to co-operate with a device in accordance with the invention.
2. Description of the Related Art
A device and a disc-shaped information carrier of the types mentioned in the opening paragraphs are disclosed in EP-A-0 300 336. The known information carrier is provided, along its circumference, with a ring of a ferromagnetic material for co-operating with the electromagnetic system of the known device. The scanning unit of the known device is secured, in a fixed position, to a frame of the device. The scanning unit includes a read and write head by means of which information present on the information carrier can be read or information can be written on the information carrier. The electromagnetic system of the known device comprises two pairs of rows of electromagnets. Viewed in a middle position of the information carrier along the X-axis and viewed in a direction parallel to a Y-axis extending perpendicularly to the axis of rotation and the X-axis, both pairs are arranged diametrically opposite each other, the ferromagnetic ring of the information carrier being situated, in operation, approximately between the two rows of electromagnets of each pair. Furthermore, said ring is situated, in operation, between the electromagnets of eight pairs of electromagnets which are arranged between the two pairs of rows of electromagnets so as to be distributed along the circumference of the information carrier. The electromagnets of said rows and pairs exert, in operation, electromagnetic forces on the ring of the information carrier. The known device further comprises a system of sensors by means of which a position of the information carrier with respect to the frame and the scanning unit can be measured, and the known device further comprises a control unit by means of which the electromagnetic forces can be controlled such that the measured position of the information carrier with respect to the scanning unit substantially corresponds to a desired position. In operation, electromagnetic forces are used to position the information carrier, with respect to the scanning unit, in five degrees of freedom, i.e. in all degrees of freedom except the degree of freedom about the axis of rotation. In operation, the electromagnetic forces are controlled such that the information carrier is rotated about the axis of rotation and simultaneously displaced along the X-axis in such a manner that the scanning unit follows a spiral-shaped information track present on the information carrier. The construction of the known device thus is very simple compared to that of conventional devices for scanning disc-shaped information carriers, which are provided with a rotatable turntable for the information carrier and with a displacement device for displacing and positioning the scanning unit with respect to the rotating information carrier.
A drawback of the known device resides in that the applied electromagnetic system has a large number of electromagnets. As a result, the construction of the electromagnetic system and the necessary control unit are complicated.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a device of the type mentioned in the opening paragraphs, which is provided with an electromagnetic system enabling an information carrier of the type mentioned in the opening paragraphs to be positioned also in five degrees of freedom with respect to the scanning unit, i.e. all degrees of freedom except the degree of freedom about the axis of rotation, but the construction of said electromagnetic system being simplified.
To achieve this object, a device in accordance with the invention is characterized in that the electromagnetic system is provided with a single pair of rows of electromagnets arranged along the X-axis, said rows of electromagnets, viewed in a direction parallel to the axis of rotation, being arranged on either side of the information carrier, and with a first pair of electromagnets and a second pair of electromagnets which, viewed in a middle position of the information carrier along the X-axis and viewed in a direction parallel to a Y-axis extending perpendicularly to the axis of rotation and the X-axis, are arranged substantially diametrically opposite each other, the electromagnets of each pair, viewed in a direction parallel to the X-axis, (Marc, tekst claim
1
wijkt hier af) being arranged on either side of the information carrier, and the magnetic poles of the electromagnets being at substantially the same distances from the axis of rotation (ook hier wijkt tekst af van claim
1
) and, in each position of the information carrier along the X-axis, on one side of a magnetic point of application of the support element.
It is to be noted that the expression “magnetic point of application” is to be taken to mean a point at which the electromagnetic force of an electromagnet of the electromagnetic system acts on the support element. As the two pairs are substantially diametrically arranged with respect to each other and the poles of the electromagnets of the two pairs are at substantially equal distances from the X-axis and are situated, in each position of the information carrier along the X-axis, at one side of the magnetic point of application, the electromagnetic forces of the two pairs comprise, in each position of the information carrier along the X-axis, both a component parallel to the axis of rotation and a component along the Y-axis, the components along the Y-axis of the two pairs extending in opposite directions. As the rows of electromagnets extend along the X-axis, in each position of the information carrier along the X-axis, at least one pair of electromagnets of both rows are situated in positions on either side of the magnetic point of application. The electromagnetic forces of the relevant pairs comprise a component extending parallel to the axis of rotation as well as a component extending along the X-axis, the components extending along the X-axis of the electromagnets of each of the relevant pairs extending in opposite directions. The position of the information carrier along the Y-axis can be controlled by controlling said oppositely directed components along the Y-axis of the forces of the first and the second pair by means of a control unit and a system of position sensors. The position of the information carrier along the X-axis can be controlled by controlling said oppositely directed components along the X-axis of the forces of the pair of rows. By controlling said components, directed parallel to the axis of rotation, of the forces of the two pairs and of the pair of rows, both the position of the information carrier parallel to the axis of rotation and the angles of the information carrier about the X-axis and Y-axis can be controlled. As the electromagnetic system comprises only a single pair of rows of electromagnets and two pairs of diametrically arranged electromagnets, the construction of the electromagnetic system is comparatively simple, and the number of electromagnets to be controlled is limited, so that also the necessary control unit is comparatively simple.
A particular embodiment of a de
Kahlman Josephus Arnoldus Henricus Maria
Ophey Willem Gerard
Van Rosmalen Gerard Eduard
Koninklijke Philips Electronics , N.V.
Lee Michael G.
Paik Steven S.
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