JPH059854B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is useful for recording signals on optical discs, such as so-called DRAW discs, on which a user can optically record signals, and for reproducing signals from such optical discs. The present invention relates to a tracking servo device for correctly tracing a light beam incident on a disc onto a track of the disc in an optical disc player.

BACKGROUND TECHNOLOGY AND PROBLEMS In optical discs, such as so-called DRAW discs, on which the user can optically record signals, groups indicating tracks or track addresses are generally pre-cut on the surface of the disc substrate. Figure 1 shows one such method called land recording, in which a land 1 is formed on the surface of the disk substrate showing a track with a height corresponding to 1/8 wavelength of the light beam incident on the disk. Track addresses and the like are recorded by partially pre-cutting group 2 at a depth corresponding to 1/4 wavelength of the light beam incident on the disk. Figure 2 shows another method called group recording, in which a group 3 is pre-cutted on the surface of the disk substrate, showing a track with a depth corresponding to 1/8 wavelength of the light beam incident on the disk. Track addresses and the like are recorded in advance by irradiation with a light beam.

By the way, in an optical disc having a track consisting of a pre-cutting part and a user recordable part, which is based on the land recording or group recording method, when a player records a signal on the disc or reproduces a signal from the disc,
The magnitude of the tracking error signal, which detects the deviation of the light beam incident on the disk from the track, is different from that of the user when the light beam traces the pre-cutting part of the track, even if the deviation of the light beam from the track is the same. There is a problem that the tracking servo, which correctly traces the light beam incident on the disk on the track of the disk, is not stable.

Purpose of the Invention In view of the above, the present invention provides an optical disc player having a track consisting of a pre-cutting section and a user recordable section, in which the tracking servo is always applied stably.

Summary of the Invention When a light beam is made incident on an optical disk having a track consisting of the aforementioned pre-cutting section and a user recordable section, a reproduced signal obtained by detecting the light beam from the optical disk is The potential or waveform changes when the beam traces the pre-cutting part of the track and when it traces the user recordable part. Specifically, in the case of the land recording method shown in FIG. ₁ , as shown in _{FIG .} The potential changes between a certain potential and a low
In contrast, in the user-recordable portion U, the potential does not fall below the intermediate potential between _{V 1 and} V ₂ , and therefore the potential V ₁ is never crossed, and the user-recordable portion In the recorded part R of U, the potential changes between an intermediate potential between the potentials _V1 and _V2 and a certain potential higher than the potential _V2 , and the potential _V2 is intermittently crossed, and the unrecorded part of the user recordable part U changes. In part N, the potential is maintained at an intermediate potential between potentials V ₁ and V ₂ . Furthermore, in the case of _the group recording method shown in FIG _. 2 _, as shown in FIG. The recorded area R of the user-recordable area U changes between 2 and 3 and intermittently crosses the potential V ₃ but never crosses the potential V ₄ .
The voltage changes between a certain potential higher than the potential V ₄ and a certain potential lower than the potential V ₃ , intermittently crossing the potentials V ₃ and V ₄ , and the potential V ₃ in the unrecorded area N of the user recordable area U. held at a certain lower potential.

Focusing on this point, in the present invention, when a light beam is made incident on an optical disk having a track provided with a pre-cutting section and a user recordable section, a light beam from the optical disk is detected. By comparing the resulting playback signal with a reference voltage, it is possible to detect whether the light beam incident on the disc is tracing the pre-cutting part of the track or the user recordable part, and the detection output is Therefore, the transmission gain of the tracking error signal is adjusted so that the loop gain of the tracking servo is the same when the light beam incident on the disk traces the pre-cutting part of the track and the user recordable part. control.

Embodiment FIG. 5 shows an example of the tracking servo device of the present invention, which corresponds to the land recording method explained in FIGS. 1 and 3, and is equipped with an optical pick-up. Photodetector 1 divided into two for tracking error detection
1 and a photodetector 12 divided into four for focus error detection, the outputs of the two photodetecting elements 11A and 11B of the photodetector 11 are supplied to a subtraction circuit 21, and the outputs of the two photodetecting elements 11A and 11B of the photodetector 11 are A tracking error signal TE representing the difference in output is taken out and sent to two photodetecting elements 1 in a diagonal direction with a photodetector 12.
The outputs of 2A and 12C are supplied to an adder circuit 22, the outputs of two other diagonal photodetecting elements 12B and 12D are supplied to an adder circuit 23, and the outputs of the adder circuits 22 and 23 are supplied to a subtracter circuit 24. and the sum of the outputs of elements 12A and 12C and element 1
A focus error signal FE, which is the difference between the sum of the outputs of 2B and 12D, is taken out and sent to adder circuits 22 and 2.
3 is supplied to the adder circuit 25, and the output of element 12
A reproduction signal RF, which is an information reproduction signal of the sum of the outputs of A, 12B, 12C, and 12D, is extracted. That is, an optical system having a track provided with a pre-cutting section and a user recordable section is formed by the photodetectors 11 and 12 and the subtraction circuits 21 and 24 and addition circuits 22, 23 and 25 connected thereto. When a light beam is made incident on the disk, a signal forming section detects the light beam from the optical disk and obtains a tracking error signal TE, a focus error signal FE, and a reproduction signal RF which is an information reproduction signal. It is composed of

The reproduced signal RF is supplied to a detection circuit 30, and it is detected from the reproduced signal RF whether the light beam incident on the disc is tracing the pre-cutting part of the track or the user recordable part. In this example, the detection circuit 30 is composed of a voltage comparison circuit 31 and a waveform shaping circuit 32, and the reproduced signal RF is supplied to the voltage comparison circuit 31 and compared with the reference voltage of the potential _V1 explained in FIG. As shown in FIG. 6, the output signal of the voltage comparator circuit 31 has a low level when the reproduced signal RF is above the potential _V1 , and a high level when the potential is lower than the potential _V1 .
Therefore, when the light beam incident on the disc traces the pre-cutting part P of the track, the signal C is intermittently set at a low level and then at a high level, and when tracing the user recordable part U, the signal C is kept at a low level. ₁ is obtained, and this signal _C1 is supplied to the waveform shaping circuit 32, and as an output signal of the waveform shaping circuit 32, the light beam incident on the disk hits the pre-cutting part P of the track. A detection signal GC is obtained which has a high level when tracing and a low level when tracing the user recordable area U. The waveform shaping circuit 32 is
For example, it is composed of an integrating circuit that integrates the signal _C1 and a voltage comparison circuit that compares the integrated signal with a reference voltage of a predetermined potential.

The tracking error signal TE is then supplied via a gain control circuit 41 to a tracking drive coil, that is, a coil 42 of a tracking drive device that moves the incident position of the light beam onto the disk in the radial direction of the disk, and output from the detection circuit 30. The signal GC is supplied as a gain control signal to the gain control circuit 41, and when the light beam incident on the disk traces the pre-cutting part P of the track and the user recordable part U.
In other words, depending on whether the output signal GC is at a high level or a low level, so that the loop gain of the tracking servo is the same when tracing the The transmission gain of the tracking error signal TE is changed when tracing P and when tracing the user recordable section U.

FIG. 7 shows another example of the tracking servo device of the present invention, which corresponds to the group recording method explained in FIGS. 2 and 4.
This example is the same as the example shown in FIG. 5 except that the specific configuration of 0 is different.

In this example, the detection circuit 30 includes two voltage comparison circuits 33 and 34 and two waveform shaping circuits 35 and 3.
6, an inverter 37, and an AND gate 38, the reproduced signal RF is supplied to the voltage comparison circuit 33 and compared with the reference voltage of the potential _V3 explained in FIG. 8th
As shown in the figure, the reproduction signal RF is at a low level when the potential is below _V3 , and is at a high level when it is higher than the potential _V3 . When tracing and when tracing the recorded portion R of the user recordable portion U, the low level and high level are intermittently maintained, and when tracing the unrecorded portion N of the user recordable portion U, the low level is maintained. A signal C ₃ is obtained, this signal C ₃ is supplied to the waveform shaping circuit 35, and as an output signal of the waveform shaping circuit 35, the light beam incident on the disk is directed to the pre-cutting portion of the track. A signal _I3 is obtained which is at a high level when tracing P and when tracing the recorded area R of the user recordable area U, and at a low level when tracing the unrecorded area N of the user recordable area U. It will be done.

Further, the reproduced signal RF is supplied to the voltage comparison circuit 34 and compared with the reference voltage of potential V ₄ explained in FIG.
As shown in FIG. 8, when the reproduction signal RF is below the potential _V4 , it becomes a low level, and when it is higher than the potential _V4 , it becomes a high level. When tracing the recorded part R of U, the low level and high level are maintained intermittently, and when tracing the pre-cutting part P and the unrecorded part N of the user recordable part U, the low level is maintained. signal to be
_C4 is obtained, this signal _C4 is supplied to the waveform shaping circuit 36, and as an output signal of the waveform shaping circuit 36, the light beam incident on the disc is transmitted to the user recordable area U of the track. A signal _I4 is obtained which is at a high level when tracing the recorded part R of , and becomes low level when tracing the pre-cutting part P and the unrecorded part N of the user recordable part U. , this signal _I4 is supplied to the inverter 37, and as an output signal of the inverter 37, as shown in the figure, when the light beam incident on the disc traces the pre-cutting part P of the track and the user recordable part. A signal ₄ is obtained which has a high level when tracing the unrecorded portion N of the user recordable portion U, and a low level when tracing the recorded portion R of the user recordable portion U.

Then, the output signal _I3 of the waveform shaping circuit 35 and the output signal ₄ of the inverter 37 are supplied to the AND gate 38, and as the output signal of the AND gate 38,
As shown in FIG. 8, the detection signal GC becomes high level when the light beam incident on the disc traces the pre-cutting part P of the track, and becomes low level when it traces the user recordable part U. is obtained, and similarly to the example of FIG. 5, this detection signal GC is supplied to the gain control circuit 41 as a gain control signal, and when the light beam incident on the disk traces the pre-cutting part P of the track, User recordable area U
In other words, depending on whether the output signal GC is at a high level or a low level, so that the loop gain of the tracking servo is the same when tracing the The transmission gain of the tracking error signal TE is changed when tracing P and when tracing the user recordable section U.

Effects of the Invention According to the present invention, when a light beam is made incident on an optical disk having a track provided with a pre-cutting section and a user recordable section, a light beam from the optical disk is detected. By comparing the obtained information reproduction signal with a reference voltage, it is possible to detect whether the light beam incident on the disc is tracing the pre-cutting part of the track or the user recordable part, and the detection output is used to detect Therefore, the transmission gain of the tracking error signal is adjusted so that the loop gain of the tracking servo is equal when the light beam incident on the disk traces the pre-cutting part of the track and the user recordable part. The difference in tracking error detection sensitivity between the pre-cutting section and the user-recordable section due to the difference in the shape of the disk substrate surface between the pre-cutting section and the user-recordable section is corrected using a circuit. As a result, stable and appropriate tracking servo is always applied. In addition, the transmission gain of the tracking error signal can be set in advance according to the state in which the light beam incident on the optical disk traces the pre-cutting part of the track and the state in which it traces the user recordable part of the track. The change in the transmission gain of the tracking error signal that takes different values is the change from tracing the pre-cutting part of the track of the light beam incident on the optical disk to tracing the user-recordable part of the track. , or vice versa, can be made very quickly in response to changes.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are perspective views, partially in cross section, showing an example of the form of the substrate surface of the disk, respectively;
3 and 4 are diagrams showing reproduced signal waveforms corresponding to FIGS. 1 and 2, respectively, and FIG. 5 is a connection diagram showing an example of the tracking servo device of the present invention,
FIG. 6 is a waveform diagram for explaining the operation of the main parts,
FIG. 7 is a connection diagram showing another example of the tracking servo device of the present invention, and FIG. 8 is a waveform diagram for explaining the operation of the main parts thereof. In the figure, 1 is land, 2 and 3 are grooves, 11
and 12 is a photodetector, TE is a tracking error signal, RF is a reproduction signal, 30 is a detection circuit, 31,
33 and 34 are voltage comparison circuits, 41 is a gain control circuit, and 42 is a tracking drive coil.

Claims (1)

[Scope of Claims] 1. Information reproduction by detecting the light beam from the optical disk when the light beam is made incident on an optical disk having a track provided with a pre-cutting section and a user recordable section. a signal forming unit that obtains the signal and the tracking error signal; and a signal forming unit that compares the information reproduction signal from the signal forming unit with a predetermined reference voltage, and determines the light beam incident on the optical disk based on the result of the comparison. The first trace of the pre-cutting part of the track
and a second state in which a light beam incident on the optical disk traces the user recordable portion of the track; and in response to the detection output signal from the detection circuit; , a gain control circuit that changes the transmission gain of the tracking error signal from the signal forming section between the first state and the second state; and a tracking device to which the tracking error signal that has passed through the gain control circuit is supplied. A tracking servo device for an optical disc player, comprising a drive device.