JPS6122444A - Optical disc reproducing device - Google Patents

Abstract

PURPOSE:To operate surely a servo loop by retarding the on-timing of a tracking servo loop switch under a prescribed condition and opening the servo loop when the rotation of a disc is made stable. CONSTITUTION:A rotation detecting sensor 30 is fitted to a disc motor 12 and its output signal is inputted to a number of revolution detecting circuit 31. Then a control signal to turn on a switch 22 is obtained from the number of revolution detecting circuit 31 not until the rotating speed of the disc motor 12 reaches a prescribed speed. Thus, the tracking servo loop comprising a tracking control signal generating circuit 21, a switch 22, and a tracking coil drive circuit 23 is formed without fail after the rotating speed of the disc motor 12 reaches a prescribed speed. Further, a conventional switch control signal from the focus control circuit 24 is not required. Thus, the pull-in operation of the tracking servo is made stable and the reliability of the device is attained. Further, a misunderstanding such as a fault is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical disc reproducing device, and particularly to an improved tracking control servo loop thereof.

[Technical Background of the Invention] Optical disc playback devices using laser light have been developed. This optical disc playback device includes a focus servo device that maintains a constant distance between the signal surface of the disc 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 disc 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 disc and the objective lens that receives the reflected light. Maintain the relationship constant (a racking servo device is provided).

FIG. 6 shows this type of optical disc reproducing apparatus. 11 is an optical disc, and a disc motor 1
Rotated by 2. A pickup section 13 generates laser light and receives reflected light from the signal surface of the disk 11. The objective lens 14 is the disk 11
A laser beam is focused on the information recording track of the disk 11, and reflected light from the disk 11 is introduced. The introduced reflected light is guided to the light receiving section 16 via the beam splitter 15. 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 input to a high frequency amplification circuit 20. The pickup section 13 further includes an objective lens 1.
a tracking coil 17 for physically driving 4;
It has a focus coil 18.

The output of the high frequency amplification circuit 20, which will be explained from the tracking servo loop, is given to a tracking control signal generation circuit 21. This tracking control signal generation circuit 21 generates a tracking error signal using the output of the high frequency amplifier circuit 2°, and supplies this to the tracking coil drive circuit 23 via a 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. This causes the pickup section 13 to follow the information recording track.

Next, the focus servo loop will be explained.

The output of the high frequency amplification circuit 20 is transmitted to the focus control circuit 25.
It is also given to The focus control circuit 25 generates a focus error signal using the output of the high frequency amplification circuit 20 and supplies it to the focus coil drive circuit 25. The focus coil drive circuit 25 generates a drive signal based on the focus error signal and supplies this to the focus coil 18 . Thereby, 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. The switch 22 is turned off before the reproduction device Vi is put into operation.

In this type of system, when a normal play operation is performed, focus adjustment is first performed, and when the focus error signal falls within a predetermined range, that is, within 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. This is the first time a tracking servo loop is formed.

[Problems with Background Art] According to the above-described conventional optical disk reproducing apparatus, there is a problem particularly when the switch 22 is turned on, and the tracking servo loop may not be able to perform a pull-in operation.

This means that at the time when a signal indicating a good focal length is obtained from the focus control circuit 24, the disk motor is still in the 1st position.
This is because the rotation of No. 2 is not at a sufficiently predetermined speed and the tracking error signal is outside the pull-in range of the servo loop.

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical disc playback device that can ensure the retracting operation of the tracking servo loop when the playback device starts operating. shall be.

[Summary of the Invention] In this invention, for example, as shown in FIG. The tracking servo loop is turned on when the rotation becomes stable.

This achieves the above objective.

[Embodiments of the invention] Embodiments 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. Only when the rotational speed of the disk motor 12 reaches a predetermined speed does the rotational speed detection circuit 31
A control signal for turning on the switch 22 can be obtained from the switch 22. Therefore, the tracking control signal generation circuit 21, the switch 22, and the tracking coil drive circuit 23
The tracking servo loop formed by the above is always set up after the rotational speed of the disk motor 12 reaches a predetermined speed. Further, 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 are used to compare the output thereof with a reference voltage. 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 output level of the low-pass filter 32 is high, and the output level of the comparison circuit 33 is high. At this time, the switch 22 is set to remain off. When the rotation speed of the disk 11 reaches a predetermined speed, the high frequency signal is cut off and the output level of the low pass filter 32 becomes low. As a result, the output of the comparison circuit 33 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, the delay circuit 34 serves as a control means for the switch 22.
is used. The delay circuit 34 receives a control signal from the focus control circuit 24 indicating that the focal length is good. Therefore, this control signal turns on the switch 22 with a time delay. As a result, when the switch 22 is turned on, the rotational speed of the disk 11 is at 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, a tracking error signal zero cross detection circuit 35, a tracking error signal determination circuit 36, a convergence area detection circuit 37, and an AND circuit 38 are used as control means for the switch 22.

The output from the light receiving section 16 of the pickup section 13 is input to the convergence area detection circuit 37 . In addition, the tracking error signal zero cross detection circuit 35 and the tracking error signal determination circuit 36 include a tracking signal zero cross detection circuit 35 and a 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. The signals a, b, c, d, and e of each part are 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. Furthermore, when the tracking error signal determination circuit 36 also detects that the input signal is within a predetermined range, it obtains the signal shown in FIG. If the high-frequency signal exceeds a predetermined reference level within a cycle within a predetermined time constant, a signal e shown in Fig. 5 is obtained.In this way, the signal e shown in Fig. 5 is obtained. An AND output is obtained at time t. Therefore, if the output of the AND circuit 38 at this time is used to turn the switch 22 from off to on, the tracking servo loop is reliably brought 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 apparatus can be achieved.

[Brief explanation of drawings]

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, and FIG.
FIG. 6 is a diagram illustrating the configuration of a servo system of a conventional disc playback device. 71... Disc, 12... Disc motor, 13
...Pickup section, 20...High frequency amplification circuit, 2
DESCRIPTION OF SYMBOLS 1... 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 area detection circuit, 38...
・AND circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 5c
. ↑ Figure 6

Claims (5)

[Claims] (1) A pickup section having a light receiving section through which reflected light of the light irradiated onto the optical disc is incident through an objective lens, and a pickup section that obtains a photoelectric conversion output from the light receiving section, and a pickup section that uses the photoelectric conversion output to an error signal output means for outputting a tracking error signal of the pickup section with respect to an information recording track of a disc, and a drive means for applying a drive signal to a tracking coil of the pickup section based on the tracking error signal, In an optical disc playback device that causes a pickup section to follow the information recording track, a switch is provided between the error signal output means and the drive means to stabilize the rotation of the optical disc when it starts rotating. 1. An optical disk reproducing apparatus, comprising: a switch control means for detecting that a tracking servo loop is detected 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 switch according to claim 1, wherein the switch control means is 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. type disc 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 detects whether the tracking error signal is within a predetermined level range. The means includes a determination circuit for making a determination, and a zero-cross detection circuit for detecting whether or not the tracking error signal has crossed zero, and uses an AND output of these circuits as an on-control output for the switch. An optical disc reproducing apparatus as claimed in claim 1.