Disc player

Details Disc player Disc player

1999-03-18

2001-08-28

Hindi, Nabil (Department: 2651)

Dynamic information storage or retrieval

Control of storage or retrieval operation by a control...

Control of information signal processing channel

C369S047270, C369S044410

Reexamination Certificate

active

06282160

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a disc player for reading information from an optical disc having ID regions, segmented into two regions in the direction of the track, in which record position information are preformatted and recorded.
A spindle control system as shown in
FIG. 14
is known as the technique for driving an optical disc to rotate in a CAV (constant angular velocity) mode in an optically readable, disc player. Information is read out of a disc
1
being rotated by a spindle motor
2
, by a pick-up (not shown). The spindle motor
2
includes means to generate a pulse signal (FG pulse signal) of which the frequency corresponds to a rotation speed of the motor. The FG pulse signal generated is applied to an error generating circuit
3
. A reference clock signal of a predetermined frequency corresponding to a target angular speed of the motor is supplied to the error generating circuit
3
. The error generating circuit
3
detects frequency and phase errors through the comparison of the clock signal and the FGpulse signal, and applies error signals dependent on the detection errors to a pulse width modulator (PWM)
4
. The output signal of the PWM
4
passes through a low-pass filter (LPF)
5
and reaches a drive circuit
6
.
Thus, the error signal is PWM processed and only its low frequency component is filtered out. The drive circuit
6
applies a drive signal, which is based on the error signal of the low frequency component, to the spindle motor
2
. The spindle motor
2
is controlled so as to reduce the error detected by the error generating circuit
3
to zero (0), viz., so as to maintain the target angular velocity of the motor.
To read the disc
1
in a CLV (constant linear velocity) mode, it is required that the disc
1
is driven to rotate in accordance with a read signal (or a read position) To realize such a drive of the motor, a synchronizing (sync) signal is extracted from the read signal, and the angular velocity of the spindle motor
2
is controlled so that the sync signal has a predetermined frequency.
In connection with the sync-signal basis motor control, the Examined Japanese Patent Application Publication No. Hei 4-71269 discloses the following technique. In a situation where no sync signal is produced, e.g., when the disc player is started or when the pick-up is moved at high speed, the maximum value of the time interval (maximum reversal interval) from the leading edge of a data signal of the read signal to the next trailing edge is detected, and the angular velocity of the spindle motor is controlled so that the maximum reversal interval reaches a predetermined value.
At present, a high density recording disc, called a DVD (digital versatile disc), is increasing its market share. Some type of the DVD has a plural number of formats for recording information therein. A typical example of those DVDs is a DVD-RAM (DVD-random access memory) allowing information to be rewritten into the DVD itself.
The DVD-RAM, or a RAM type DVD, has the following disadvantage when no information is recorded therein or a small amount of information is recorded in a part thereof. In the RAM type DVD, data signals to be used for the control of the spindle motor are absent or, if present, are insufficient for the control. Therefore, the disc player frequently fails to detect the maximum reversal interval or the maximum/minimum time period.
ID regions are preformatted at predetermined angular spatial intervals in the surface of the DVD-RAM. Address information on the disc and information indicative of a groove track or a land track are stored in the ID regions. (The ID region will be described in detail later.) It is required that the disc player accurately detects the ID regions.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a disc player capable of performing a good spindle control of a disc-like recording medium of the DVD-RAM type having no information recorded therein or information recorded in a part thereof in accordance with a signal read out of the disc, and hence of exactly recording information into or playing back the same from the disc.
According to a first aspect of the present invention, there is provided a disc player for obtaining a read signal from an optical disc having sectors including ID regions, preformatted at given angular spatial intervals, which demarcate the sectors and are segmented, in the track extending direction, into two regions, each segmented region including a plural number of recording regions and non-recording regions, which are alternately and radially arrayed while being radially shifted by approximately half a track pitch from the tracks of the sectors adjacent to the segmented regions, each recording region containing record position information recorded therein having predetermined time durations. The disc player comprises: optical read means for projecting a light beam onto the optical disc and receiving a light beam reflected from a recording surface of the optical disc; first and second signal generating means for generating first and second signals which are dependent on the record position information recorded in the recording regions of the first and second segmented regions by use of a signal output from the optical read means; and ID region detecting means for outputting a detecting signal indicating that the ID region is detected when the first and second signals are both present.
According to a second aspect of the present invention, a disc player, based on the first aspect, is constructed such that the ID region detecting means in the disc player produces a detecting signal when the first and second signals continue for a predetermined time.
According to a third aspect of the present invention, a disc player modifies the first aspect or the second aspect such that the first signal generating means generates a first signal by use of a signal formed by binarizing an output signal of the optical read means in accordance with a first threshold value, and the second signal generating means generates a second signal by use of a signal formed by binarizing an output signal of the optical read means in accordance with a second threshold value.
According to a fourth aspect of the present invention, a disc player modifies any of the first to third aspects such that information is recorded in the land tracks and the groove tracks every sector demarcated by the ID regions.
According to a fifth aspect of the present invention, a disc player modifies any of the first to fourth aspects such that the optical disc is controlled in rotation thereof in accordance with the detecting signals.
According to a sixth aspect of the present invention, a disc player, based on the fourth or fifth aspects, further comprises means for judging if the track being currently scanned is a land track or a groove track depending on the first and second signals, and the detecting signals.
The thus constructed disc player is capable of performing a good spindle control of a disc-like recording medium of the DVD-RAM type having no information recorded therein or information recorded in a part thereof in accordance with a signal read out of the disc, and hence of exactly recording information into or playing back the same from the disc.


REFERENCES:
patent: 4700337 (1987-10-01), Inagawa et al.
patent: 5872767 (1999-02-01), Nagai et al.
patent: 5930228 (1999-07-01), Miyamoto et al.
patent: 5933410 (1999-08-01), Nakane et al.
patent: 6091699 (2000-07-01), Nakane et al.
patent: 6147961 (2000-11-01), Nagasawa et al.
patent: 6163522 (2000-12-01), Nakane et al.
patent: 0 302 680 A2 (1989-02-01), None
patent: 0 795 858 A2 (1997-09-01), None
patent: 0 871 169 A1 (1998-10-01), None
patent: 0 872 838 A2 (1998-10-01), None
patent: 4-71269 (1992-11-01), None

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