Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2000-02-22
2004-06-22
Patel, Gautam R. (Department: 2655)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044340, C369S047190, C369S118000
Reexamination Certificate
active
06754145
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a disk drive which has a function of compensating a tilt (an inclination) between a disk which is a recording medium and a head from which a light beam is irradiated.
Recently, optical disks have attracted attention as a solution to meet demands for mediums for storing information more voluminous than conventional textual or audio information. On conventional erasable optical disks, guide grooves for use in control to keep a light beam for recording/reproduction on the track center are formed when the disks are manufactured. Because of the guide grooves, lands and grooves are formed on a disk in spiral or concentric form. By the use of both the lands and grooves as recording tracks (land tracks and groove tracks), recording twice as much information as that recorded by the use of either one as recording tracks can be realized. In addition, there is a method of connecting the lands and grooves so that the land tracks and groove tracks alternate every revolution of a disk to form a single spiral track, thereby improving the data access performance. This method is referred to as the single-spiral land/groove. (SS-L/G) recording format. An example of a disk drive using this method is described in Japanese Patent Application Kokai Publication No. 282669/1997.
According to the conventional disk format, recording tracks are divided in the track direction into sectors, and in the forefront of each sector, sector identification information, such as track number and sector number, is pre-formatted as pits which generate variation in physical shape or in local optical constants. Moreover, the sector format includes a first identification information area in which the sector identification information is disposed being displaced a predetermined distance in the radially outward direction from the center of the recording track, a second identification information area in which the sector identification information is disposed being displaced a predetermined distance in the radially inward direction from the center of the recording track, and a user information area which follows the sector identification information areas and in which user information and the like is recorded on the center of the recording tracks.
Next, a disk drive using an optical disk in which sector information is disposed as explained above will be described.
FIG. 16
shows a track layout of the conventional optical disk.
FIG. 17
is a block diagram showing the configuration of the disk drive for recording or reproducing information on such a kind of optical disks.
FIG. 16
shows the track layout of the conventional optical disk, the disposition of tracks and recording sectors in a zone, and the configuration of each recording sector. As shown in the drawing, the disk is in the SS-L/G recording format and comprises grooves and lands of identical width. That is, the width of grooves and lands is equal to the track pitch, and is a half of the interval between grooves.
In a recording track which includes an integer number of recording sectors, a sector identification information area (a sector identification signal part) in which sector identification information representing information for PLL pulling in, address information and the like is pre-formatted, is added to the forefront of each sector, and a user information area (an information recording part), in which user data and various management information are recordable, is disposed following the sector identification information part.
Moreover, the sector identification information area comprises two parts, that is, the front and rear parts as seen in the scanning direction, and is made of a first identification information area in which the sector identification information is disposed being displaced a predetermined distance in the radially outward direction from the center of the track and a second identification information area in which the sector identification information is disposed being displaced a predetermined distance in the radially inward direction from the center of the track.
An additional function is a track offset compensation. For optical disks of the sample servo method, a method is known which provides a pair of track offset detecting pits in the position displaced a predetermined distance to the right and left sides of the track center on the recording track so as to detect and compensate the tracking offset amount, as shown for example in the optical disk standard ISO/IFC 9171-1, 2 “130 mm Optical Disk Cartridge Write Once for Information Interchange,”1990.
When the light beam passes through the center of the pair of track offset detecting pits, the reproduced signal amplitudes of the pair of detecting pits are identical. If the light beam is offtrack, the reproduced signal amplitude of the pit in one side increases while that of the pit in the other side decreases. By detecting the track offset amount of the light beam, and applying compensation, it is possible to realize a control over the light beam so that it passes through the track center. This principle and effect can be applied to the SS-L/G recording format of the conventional drive.
Suppose that the light beam enters, from a user information area (a user signal area) in a certain groove recording sector, into a sector identification information area (a sector identification signal area) in the next groove recording sector. Since the forefront of the sector identification information area is shifted half the groove width to the outer (or inner) periphery of the disk, a corresponding tracking error signal is produced. After a while, the light beam reaches an identification signal part shifted half the groove width to the inner (or outer) periphery of the disk, and a corresponding tracking error signal is output. If these two error signals are detected in waveforms vertically symmetric with respect to a reference level (that is a tracking error level obtained when scanning the track center), the light beam is scanning the track center. Accordingly, the servo can be controlled to keep on the track center, by a comparison in size between tracking errors detected from the identification signal parts displaced to the inner and outer peripheries. Here, the order of disposition of the first and second identification information area is different depending on whether the track is a land or groove. That is, if in a land track the order of disposition is as the first identification information area and then the second identification information area, in a groove track the order is converse.
In this way, providing an SS-L/G recording disk with identification signals also makes it possible to improve a servo characteristic.
With reference to
FIG. 17
, the configuration of the conventional disk drive is as follows. In the drawing, reference numeral
10
, denotes an optical disk,
11
denotes a semiconductor laser (LD) serving as a light source,
12
denotes a collimate lens,
13
denotes a beam splitter,
14
denotes an objective lens,
15
denotes a photodetector,
16
denotes an actuator,
17
denotes a differential amplifier,
18
denotes a difference signal waveform shaping unit,
19
denotes a reproduced difference signal processor,
20
denotes a polarity controller,
21
denotes a polarity reversing unit,
22
denotes a tracking controller,
23
denotes a summing amplifier,
24
denotes a sum signal waveform shaping unit,
25
denotes a reproduced signal processor,
26
denotes a polarity information reproduction unit,
27
denotes an address reproduction unit,
28
denotes an information reproduction unit,
29
denotes a system controller,
30
denotes a traverse controller,
31
denotes a traverse motor,
32
denotes a recording signal processor,
33
denotes a laser (LD) driver, and
34
denotes an actuator driver. The semiconductor laser
11
, the collimate lens
12
, the beam splitter
13
, the objective lens
14
, the photodetector
15
, and the actuator
16
in combination constitute an optical head which is attached t
Nakane Kazuhiko
Shimamoto Masayoshi
Birch & Stewart Kolasch & Birch, LLP
Patel Gautam R.
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