Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1999-03-16
2001-06-05
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S053130
Reexamination Certificate
active
06243337
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tilt detector for detecting a tilt which is present between an information reading means for reading recorded information from a recording disk as a recording medium and the recording disk.
2. Description of Related Background Art
For correctly reading recorded information from a recording disk as an optical recording medium, it is necessary to irradiate the recording disk with a reading beam perpendicularly to a recording surface thereof. However, if the recording disk itself warps, the recording disk cannot be irradiated with the reading beam perpendicularly to the recording surface thereof, thereby resulting in a reduction in information reading accuracy.
To avoid this inconvenience, a recorded information reproducing apparatus for reproducing recorded information from such a recording disk is provided with a tilt sensor for detecting a tilt formed between a pickup as an information reading means and the recording disk. The entire pickup is tilted by an angle corresponding to a tilt detected by the tile sensor, or desired signal processing is applied to a read signal read by the pickup in accordance with the detected tilt, thereby preventing information reading accuracy from reducing.
FIG. 1
is a diagram schematically illustrating the configuration of a recorded information reproducing apparatus which is equipped with a tilt sensor
4
for detecting a tilt between a recording disk and a pickup, as mentioned above.
Referring specifically to
FIG. 1
, a beam generator
41
in the tilt sensor
4
emits divergent light which is irradiated to two different positions on a recording surface of a recording disk
3
rotated or driven by a spindle motor
2
. A light detector
42
receives a portion of reflected light produced when the divergent light is irradiated to the recording surface of the recording disk
3
, and supplies a subtractor
44
with a first detecting signal having a level corresponding to the amount of received light. A light detector
43
, in turn, is disposed at a position which is symmetrical to the light detector
42
with respect to the beam generator
41
. The light detector
43
receives a portion of the reflected light produced when the divergent light is irradiated to the recording surface of the recording disk
3
, and supplies the subtractor
44
with a second detecting signal having a level corresponding to the amount of received light. The subtractor
44
calculates the difference in level between the first detecting signal and the second detecting signal, and outputs the difference as a tilt error signal. The apparatus is herein on the assumption that the beam generator
41
and the light detectors
42
,
43
are disposed on the same parallel surface as a pickup, not shown.
When the recording surface of the recording disk
3
and the pickup is maintained in a parallel relationship, the light detectors
42
,
43
receive the same amount of reflected light, causing the subtractor
44
to generate the tilt error signal at “
0
.” On the other hand, if the recording disk
3
is not flat for warp or the like, the light detectors
42
,
43
receive different amounts of received light from each other, causing the subtractor
44
to output the tilt error signal corresponding to the difference in the amount of reflected light.
However, if the tilt sensor
4
is equipped in a recorded information reproducing apparatus, there is a problem that the scale of the apparatus becomes larger. Further, there is another problem that high positioning accuracy is required to correctly locate the tilt sensor
4
at a position for maintaining a parallel relationship with the pickup when the tilt sensor
4
is mounted.
SUMMARY OF THE INVENTION
In view of the problems mentioned above, it is an object of the present invention to provide a tilt detector which is capable of accurately detecting a tilt which is present between a recording disk and a pickup in a small scaled configuration.
A tilt detector according to the present invention is adapted to detect a tilt present between information reading means and a recording disk, wherein the information reading means reads recorded information from the recording disk having recording tracks formed thereon. The tilt detector comprises error detecting means for detecting an error value between a read signal read from a central recording track within three recording tracks which are adjacent to each other and a predetermined value, a coefficient calculating means for calculating a first coefficient from a correlation of a first read signal read from a first adjacent recording track which is adjacent to the central recording track on an inner peripheral side of the disk with the error value, and for calculating a second coefficient from a correlation of a second read signal read from a second adjacent recording track which is adjacent to the central recording track on an outer peripheral side of the disk with the error value, and means for calculating a tilt present between the recording disk and the information reading means based on a relationship in magnitude between the first coefficient and the second coefficient.
REFERENCES:
patent: 5253239 (1993-10-01), Edahiro et al.
patent: 5848045 (1998-12-01), Kirino et al.
Kuribayashi Hiroki
Miyanabe Shogo
Edun Muhammad
Perman & Green LLP
Pioneer Electronic Corporaion
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