JPH0473221B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical disc playback device,
In particular, the tracking control servo loop has been improved.

[Technical Background of the Invention] An optical disc playback device using laser light has been developed. This optical disk reproducing device includes a focus servo device that maintains a constant distance between the signal surface of the disk and the objective lens that receives the reflected light, and a focus servo device that maintains a constant distance between the signal surface of the disk and the objective lens that receives the reflected light, and a focus servo device that maintains a constant distance between the signal surface of the disk and the objective lens that receives the reflected light. A tracking servo device is provided to maintain the relative relationship constant.

FIG. 6 shows this type of optical disc playback device. Reference numeral 11 denotes an optical disk, which is rotated by a disk motor 12. Also 13
is the pick-up part, which generates laser light,
Receives reflected light from the signal surface of the disk 11. The objective lens 14 focuses the laser beam onto the information recording track of the disk 11, and also introduces reflected light from the disk 11. The introduced reflected light passes through the beam splitter 15 to the light receiving section 16.
guided by. The light receiving section 16 converts incident light into an electrical signal, and uses, for example, a split photodiode. The output of this light receiving section 16 is
The signal is input to the high frequency amplification circuit 20. The pickup section 13 further includes a tracking coil 17 and a focus coil 18 for physically driving the objective lens 14.

To explain from the tracking servo loop, the output of the high frequency amplification circuit 20 is given to a tracking control signal generation circuit 21. This tracking control signal generation circuit 21 is a high frequency amplifier circuit 20.
generate a tracking error signal using the output of
This is applied to the tracking coil drive circuit 23 via the switch 22. The tracking coil drive circuit 23 generates a drive signal based on the tracking error signal and supplies it to the tracking coil 17. As a result, the pick-up section 13
The information recording track can be followed.

Next, the focus servo loop will be explained. The output of the high frequency amplifier circuit 20 is also given to a focus control circuit 25. This focus control circuit 25 generates a focus error signal using the output of the high frequency amplifier circuit 20 and supplies it to the focus coil drive circuit 25. This focus coil drive circuit 25, based on the focus error signal,
Generates a drive signal and sends it to the focus coil 18
give to As a result, the focus of the pickup section 13 is maintained constant.

The above operation is performed when each servo loop is already in the operating state. Before the playback device is put into operation, the switch 22 is turned off.
In this type of system, when a normal play operation is performed, focus adjustment is first performed, and when the focus error signal reaches a predetermined range, that is, the servo loop pull-in range, the focus control circuit 24 sends a signal indicating that the focal length is good. It is only when this is obtained that the switch 22 is controlled and turned on.
A tracking servo loop is thus formed for the first time.

[Problems with Background Art] According to the conventional optical disc reproducing apparatus described above, there is a problem particularly when the switch 22 is turned on, and the retracting operation of the tracking servo loop may not be obtained. This is because at the time a signal indicating a good focal length is obtained from the focus control circuit 24, the 12 rotations of the disk motor have not yet reached the predetermined speed, and the tracking error signal is outside the servo loop's pull-in range. This is because it is in

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an optical disc reproducing device that can ensure the retracting operation of the tracking servo loop at the time of starting the operation of the reproducing device. purpose.

[Summary of the Invention] In the present invention, as shown in FIG. 1, for example, at the time of starting the apparatus, means is provided to delay the on-timing of the tracking servo loop switch 22 under certain conditions, and the disk 1
The tracking servo loop is turned on when the rotation of 1 becomes stable. This achieves the above objective.

[Embodiments of the Invention] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows one embodiment of the present invention, and the same parts as in the conventional one are given the same reference numerals as in FIG. 6 for explanation. In this embodiment, a rotation detection sensor 30 is attached to the disk motor 12, and its output signal is input to a rotation speed detection circuit 31. A control signal for turning on the switch 22 is obtained from the rotation speed detection circuit 31 only when the rotation speed of the disk motor 12 reaches a predetermined speed. Therefore, the tracking servo loop formed by the tracking control signal generation circuit 21, the switch 22, the tracking coil drive circuit 23, etc. is always set up after the rotational speed of the disk motor 12 reaches a predetermined speed. Become. Also, the conventional switch control signal from the focus control circuit 24 is no longer necessary.

This stabilizes the retracting operation of the tracking servo and improves the reliability of the device. It also eliminates misunderstandings such as malfunctions.

FIG. 2 shows a second embodiment of the invention, in which a low-pass filter 32 and a comparator circuit 33 for comparing the output thereof with a reference voltage are used. The input terminal of the low-pass filter 32 is connected to the output terminal of the high frequency amplifier circuit 20. Therefore, in this embodiment, when the rotation of the disk motor 12, that is, the rotation of the disk 11 is insufficient, the low-pass filter 32
The output level of the comparator circuit 33 is high, and the output level of the comparator circuit 33 is high. At this time, the switch 22 is set to remain off. disk 1
When the rotation speed of 1 reaches a predetermined speed,
The high frequency signal is cut out and the output level of the low pass filter 32 becomes low. As a result, the comparison circuit 33
The output becomes low level, and the switch 22 is turned on. Note that the other parts are the same as those in the first embodiment, so the explanation will be omitted.

FIG. 3 shows a third embodiment of the invention. In this embodiment, a delay circuit 34 is used as a control means for the switch 22. A control signal indicating a good focal length from the focus control circuit 24 is input to the delay circuit 34 . Therefore, this control signal is transmitted to switch 2 with a time delay.
2 will be turned on. As a result, switch 2
2 is turned on, the rotational speed of the disk 11 has reached a sufficient speed, and the tracking servo loop settles into a stable control state.

FIG. 4 shows a fourth embodiment of the invention. In this embodiment, the tracking error signal zero cross detection circuit 3 is used as a control means for the switch 22.
5. A tracking error signal determination circuit 36, a convergence area detection circuit 37, and an AND circuit 38 are used. The convergence area detection circuit 37 receives the output from the light receiving section 16 of the pickup section 13. Also, the tracking error signal zero cross detection circuit 3
5. The tracking error signal determination circuit 36 includes:
A tracking error signal from the tracking control signal generation circuit 21 is input. The outputs of the tracking error signal zero cross detection circuit 35, the tracking error signal determination circuit 36, and the convergence area detection circuit 37 are input to an AND circuit 38, and the logical product thereof is used as a switch control signal.

Next, the operation of the control means for the switch 22 will be explained. Assume that the disc playback device is now operated to play and the disc motor 12 starts rotating. At this time, the signals a, b, c, d, e of each part
The result is as shown in Fig. 5. The signal a stabilizes as a tracking error signal as the rotation of the disk approaches a predetermined speed. The tracking error signal zero cross detection circuit 35 detects this and compares it with a predetermined reference level to obtain an output like signal c. Further, when the tracking error signal determination circuit 36 detects that the input signal is within a predetermined range, it obtains the signal b shown in FIG. Further, the convergence region detection circuit 37 monitors the signal of the pickup section, and if the high frequency signal exceeds a predetermined reference level within a cycle within a predetermined time constant, it obtains the signal e shown in FIG. . In this way, an AND output can be obtained at time t, as shown by waveform f in FIG. Therefore, the output of the AND circuit 38 at this time causes the switch 22 to
By reversing from off to on, the tracking servo loop is reliably pulled into a stable control state.

[Effects of the Invention] As described above, according to the present invention, the tracking servo loop can be reliably brought into operation, and the reliability of the device can be improved.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing one embodiment of this invention, FIG. 2 is a configuration explanatory diagram showing a second embodiment of this invention, and FIG. 3 is a configuration explanatory diagram showing a third embodiment of this invention. 4 is a configuration explanatory diagram showing a fourth embodiment of the present invention, FIG. 5 is a signal waveform diagram of each part of the circuit in FIG. 4, and FIG. 6 is a configuration showing a servo system of a conventional disc playback device. It is an explanatory diagram. 11...Disk, 12...Disk motor, 13
...Pickup section, 20...High frequency amplification circuit, 21
...Tracking control signal generation circuit, 22...Switch, 23...Tracking coil drive circuit, 25...
Focus coil drive circuit, 31... Rotation speed detection circuit, 32... Low-pass filter, 33... Comparison circuit, 34
... Delay circuit, 35... Tracking error signal zero cross detection circuit, 36... Tracking error signal determination circuit, 37... Convergence region detection circuit, 38... AND circuit.

Claims (1)

[Scope of Claims] 1. A pickup section having a light receiving section through which the reflected light of the light irradiated onto the optical disk is incident through an objective lens, and obtaining a photoelectric conversion output from the light receiving section;
error signal output means for outputting a tracking error signal of the pickup section for the information recording track of the optical disk using the photoelectric conversion output; and a drive signal for outputting a drive signal to the tracking coil of the pickup section based on the tracking error signal. In the optical disk reproducing apparatus, a switch is provided between the error signal output means and the drive means, and a switch is provided between the error signal output means and the drive means, so that the optical disk 1. An optical disc playback device, comprising switch control means for detecting that the rotation has stabilized when the rotation has started, and turning on the switch to form a tracking servo loop. 2. The optical disc reproducing apparatus according to claim 1, wherein the switch control means is a rotation speed detection means of a desk motor that rotationally drives the optical disc. 3. The optical disc according to claim 1, wherein the switch control means includes a low-pass filter into which the output of the pickup section is input, and a comparison circuit that compares this output with a reference voltage. playback device. 4. The optical disc reproducing apparatus according to claim 1, wherein the switch control means is a delay circuit that delays a signal indicating a good focal length from a focus control circuit. 5. The switch control means includes a convergence area detection circuit that detects whether the output of the pickup section is within a predetermined convergence area, and a convergence area detection circuit that determines whether the output of the tracking error signal is within a predetermined level range. The device is characterized by comprising a determination circuit and a zero-crossing detection circuit for detecting whether or not the tracking error signal crosses zero, and the AND output of these circuits is used as the on-control output of the switch. An optical disc playback device according to claim 1.