Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-12-07
2001-06-19
Tran, Thang V. (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S044320
Reexamination Certificate
active
06249498
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a tilt detecting method in a recorded information reproducing apparatus for detecting a tilt occurring between a recording disk as a recording medium and a pickup to read recorded information from the recording disk.
2. Description of Related Art
To accurately read out recorded information from an optical disk as a recording medium, it is necessary to irradiate a reading beam perpendicularly to the recording surface of the optical disk. However, if the optical disk is warped, the reading beam cannot be irradiated perpendicularly to the recording surface of the optical disk and information reading precision deteriorates.
In recorded information reproducing apparatuses for reproducing the recorded information from the optical disk, a tilt sensor to detect a tilt occurring between the recording disk and the pickup is provided. In such an arrangement, the whole pickup is inclined by an angle corresponding to the tilt detected by the tilt sensor or a desired signal process according to the tilt is performed to the read signal which was read out by the pickup, thereby suppressing the deterioration in information reading precision.
FIG. 1
is a diagram schematically showing a construction in which a tilt sensor
4
is provided in a recorded information reproducing apparatus, to detect a tilt occurring between the recording disk and the pickup as mentioned above.
In
FIG. 1
, a beam generator
41
in the tilt sensor
4
irradiates divergent light which is irradiated to two different positions on the recording surface of a recording disk
3
which is rotated by a spindle motor
2
. A photodetector
42
receives a part of the reflection light when the divergent light is irradiated to the recording surface of the recording disk
3
and supplies a first detection signal having a level according to a photosensitive amount to a subtractor
44
. A photodetector
43
is arranged at a position that is symmetrical to the photodetector
42
around the beam generator
41
as a center. The photodetector
43
receives a part of the reflection light when the divergent light is irradiated to the recording surface of the recording disk
3
and supplies a second detection signal having a level according to a photosensitive amount to the subtractor
44
. The subtractor
44
obtains a level difference between the first and second detection signals and outputs as a tilt error signal. It is now assumed that each of the beam generator
41
and photodetectors
42
and
43
is arranged on the same parallel plane as that of a pickup (not shown).
Now, if we assume that a parallel relation is maintained between the recording surface of the recording disk
3
and the pickup, since the amounts of reflection light which is received by the photodetectors
42
and
43
are the same, a tilt error signal become equal to “0”. If a warp or the like exists in the recording disk
3
, the amounts of reflection light which is received by the photodetectors
42
and
43
are different, so that a tilt error signal corresponding to a difference between the reflection light amounts is generated.
If the tilt sensor
4
is provided in the recorded information reproducing apparatus, there however arises a problem that the scale of the apparatus becomes large. Furthermore, upon installation of the tilt sensor in the reproducing apparatus, the tilt sensor
4
has to be accurately attached at the position where the parallel relation between the disk and the pickup is held, so that there is a problem such that high attaching precision is required.
OBJECTS AND SUMMARY OF THE INVENTION
The invention is made to solve those problems and it is an object of the invention to provide a tilt detecting method which can accurately detect a tilt occurring between a recording disk and a pickup by employing a construction of a small scale.
According to the first aspect of the invention, there is provided a tilt detecting method in a recorded information reproducing apparatus, in which a tilt occurring between a recording disk on which information has been recorded and a pickup for photoelectrically converting reflection light when a reading beam is irradiated onto a recording track formed on the recording disk and obtaining a read signal is detected, comprising the steps of: setting a reading position of the pickup for the center recording track among three adjacent recording tracks to a reference; detecting a crosstalk amount, as a first crosstalk, from each of the positions which are displaced forward and rearward from the reading position on the recording track that is neighboring on the disk's inner rim side of the center recording track by a predetermined distance in the reading direction to the reading position; detecting a crosstalk amount, as a second crosstalk, from each of the positions which are displaced forward and rearward from the reading position on the recording track that is neighboring on the disk's outer rim side of the center recording track by a predetermined distance in the reading direction to the reading position; and detecting the tilt occurring between the recording disk and the pickup based on a balance between the first and second crosstalks.
According to the second aspect of the invention, there is provided a tilt detecting method in a recorded information reproducing apparatus, in which a tilt occurring between a recording disk on which information has been recorded and a pickup for photoelectrically converting reflection light when a reading beam is irradiated onto a recording track formed on the recording disk and obtaining a read signal is detected, comprising the steps of: setting a reading position of the pickup for the center recording track among three adjacent recording tracks to a reference; detecting a crosstalk amount, as a first crosstalk, from the position which is displaced forward from the reading position on the recording track that is neighboring on the disk's inner rim side of the center recording track by a predetermined distance in the reading direction to the reading position; detecting a crosstalk amount, as a second crosstalk, from a position which Is displaced forward from the reading position on the recording track that is neighboring on the disk's outer rim side of the center recording track by a predetermined distance in the reading direction to the reading position; and detecting the tilt occurring between the recording disk and the pickup on the basis of a balance between the first and second crosstalks.
According to the third aspect of the invention, there is provided a tilt detecting method in a recorded information reproducing apparatus, in which a tilt occurring between a recording disk on which information has been recorded and a pickup for photoelectrically converting reflection light when a reading beam is irradiated onto a recording track formed on the recording disk and obtaining a read signal is detected, comprising the steps of : setting a reading position of the pickup for the center recording track among three adjacent recording tracks to a reference; detecting a crosstalk amount, as a first crosstalk, from the position which is displaced rearward from the reading position on the recording track that is neighboring on the disk's inner rim side of the center recording track by a predetermined distance in the reading direction to the reading position; detecting a crosstalk amount, as a second crosstalk, from the position which is displaced rearward from the reading position on the recording track that is neighboring on the disk's outer rim side of the center recording track by a predetermined distance in the reading direction to the reading position; and detecting the tilt occurring between the recording disk and the pickup on the basis of a balance between the first and second crosstalks.
REFERENCES:
patent: 4674078 (1987-06-01), Otsuka et al.
patent: 5321519 (1994-06-01), Akiyama
patent: 5808985 (1998-09-01), Gerber et al.
patent: 5889752 (1999-03-01), Maeda et al.
pa
Kuribayashi Hiroki
Miyanabe Shogo
Chu Kim-Kwok
Perman & Green LLP
Pioneer Electronic Corporation
Tran Thang V.
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