JPH05109182A - Optical disk reproducing device - Google Patents

Abstract

PURPOSE:To prevent the number of rotations of a disk from becoming abnormally high even when the track deviation occurs at the time of the rough servo of a CLV in an optical disk reproducing device to read and reproduce the digital data of the limited cycle recorded by a CLV (constant linear velocity) mode at a spiral track on an optical disk. CONSTITUTION:The rough servo loop of a CLV is constituted of an optical disk 1, an optical pick-up 3, a waveform shaping means 4, a longest cycle measuring means 5, a motor control means 6, a switch 11, a loop filter 7, a driver 8 and a spindle motor 2. The track deviation of the optical pick-up 3 is detected by a track deviation detecting means 10, and at the time of the track deviation, by the witch 11, the rough servo loop of the CLV is cut and it is prevented that a motor driving signal is communicated to the spindle motor 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus for reading and reproducing digital data of a finite period recorded in a CLV mode on a spiral track on an optical disk.

[0002]

2. Description of the Related Art In recent years, optical discs have become widespread for consumer use in the form of compact discs as digital audio package media. Since digital audio has advantages over analog audio, such as wide dynamic range and no signal deterioration during transmission, analog records are being replaced by compact discs.

A conventional optical disc reproducing apparatus will be described below with reference to the drawings, taking a compact disc player as an example.

First, the format of a signal recorded on a compact disc will be briefly described. CLV mode (1.2 to 1.4 m / s) on the spiral track from the inner circumference to the outer circumference on the compact disc
Digital data is recorded in. This digital data is EFM (Eight to Fourteen Mo
modulation, and its inversion period (the period from when the data rises from L to H to the next fall from H to L, or vice versa, from H to L and then from L to H). Figure 4 shows how long it takes to get up
Approximately 231 ns (= 1 / 4.3218MH
z) is a basic period T and is limited to a length of 3T to 11T. Also, as a frame synchronization signal, 44.1 kHz
The longest 11T data is to be recorded twice consecutively in the z cycle. Therefore, the digital data is read, the edge is detected, the longest cycle thereof is measured, and the measured cycle is about 2.55 μs corresponding to 11T.
By rotating the spindle motor in such a manner as described above, the rotation speed control of approximately CLV can be performed. For normal reproduction, P is calculated from the reference clock obtained by dividing the crystal oscillation clock and the read digital data.
It is necessary to further configure the PLL with the clock generated by the LL and perform more precise rotation speed control.
This method of measuring the longest period is used as a rough servo for increasing the rotation speed to the capture range of.

FIG. 5 is a block diagram of a coarse servo system of a spindle motor of a conventional compact disc player. In FIG. 5, 1 is a compact disc, 2
Is a spindle motor, 3 is an optical pickup, 4 is waveform shaping means, 5 is longest period measuring means, 6 is motor control means,
Reference numeral 7 is a loop filter, 8 is a driver, and 9 is a reference clock generating means.

The operation of the compact disc player configured as described above will be described below. The digital data recorded on the compact disc 1 is
Focus by an optical servo circuit not shown,
It is read by the optical pickup 3 whose tracking is controlled. The read signal is an analog waveform with a small amplitude and frequency limited, and the slice level is controlled by the waveform shaping means 4 so that the amplified and averaged duty becomes 50% so as to be suitable for digital signal processing. After being punched out and shaped into a waveform, it is input to the longest cycle measuring means 5. The longest cycle measuring means 5 measures the longest cycle corresponding to 11T after performing edge detection. When both focus and tracking are normally controlled, the measured cycle is proportional to the rotation speed of the compact disc 1, that is, the spindle motor 2, and the information is input to the motor control means 6. The motor control means 6 outputs a motor drive signal based on the reference clock generated by the reference clock generation means 9 such that the inputted information of the longest cycle matches a predetermined cycle (about 2.55 μs). It This motor drive signal is the loop filter 7,
The spindle motor 2 is driven through the driver 8 to form a servo loop as shown in FIG.

[0007]

However, in the conventional optical disk reproducing apparatus as described above, when the optical pickup 3 is out of tracking due to some cause such as vibration, its output waveform is as shown in FIG. 6 (a). When the slice level cannot follow the fluctuation of the DC component of the input signal in the waveform shaping means 4, the period much longer than 11T is measured as the longest period according to the speed across the track as shown in FIG. 6B. It is input to the means 5. The motor control means 6 accelerates the spindle motor 2 in an attempt to match the abnormally long cycle with a predetermined cycle of 11T. As a result, there is a problem that a runaway state occurs, and in that state, the vibration of the spindle motor 2 cannot control the tracking of the optical pickup 3 in a stable manner, and the runaway state cannot be recovered forever. It was

In view of the above-mentioned conventional problems, the present invention has been made for the purpose of providing an optical disk reproducing apparatus which does not fall into a runaway state even when tracking is missed.

[0009]

In order to solve the above problems, an optical disk reproducing apparatus of the present invention comprises a spindle motor for rotating the disk, an optical pickup for tracing the track and reading digital data, and the optical pickup. And a motor for controlling the rotation speed of the spindle motor so that the longest cycle measured by the longest cycle measuring means coincides with a predetermined cycle. Control means, track off-track detection means for detecting that the optical pickup has caused track off, and turning on the output of the spindle motor control means to the spindle motor according to the output of the track off-track detection means And a switch for turning off / on.

[0010]

With the above-described structure, the present invention can prevent the spindle motor from being driven when the tracking of the optical pickup is missed, thereby preventing a runaway of rotation.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disk reproducing apparatus of the present invention will be described in detail below with reference to FIGS. 1 to 3 by taking a compact disk player as an example.

FIG. 1 is a block diagram of a coarse servo system of a spindle motor of a compact disc player according to an embodiment of the present invention. In FIG. 1, the same components as those in FIG. 5 are represented by the same numbers. Further, in FIG. 1, reference numeral 10 denotes a track deviation detecting means, and 11 denotes a switch.

The operation of the optical disk reproducing apparatus configured as described above will be described focusing on the points different from the conventional example of FIG. The output of the optical pickup 3 is the waveform shaping means 4
At the same time, the data is also input to the track deviation detecting means 10. The output of the off-track detecting means 10 is a control input of the switch 11, and the switch 11 is off when the track is off and the switch 11 is on when the track is off.

With this configuration, the output of the spindle motor control means 6 is passed through the loop filter 7 and the driver 8 so that the longest cycle information of the output of the longest cycle measuring means 5 becomes 11T except when the track is off. Drive 2 On the other hand, when the truck comes off,
As shown in (1), since the motor drive signal based on the incorrect longest cycle information is turned off by the switch 11, the spindle motor 2 is not unnecessarily accelerated and the runaway does not occur. The optical pickup 3 causes a track jump due to a vibration or the like, and the spindle motor 2 is driven in the same manner as in a normal case in a portion where the track deviation detection signal does not stand when the track crosses, that is, a portion where the track is on. Contrary to the runaway, the spindle motor 2 does not stop.

An offset for compensating for the shaft loss of the spindle motor 2 may be injected after the switch 11,
If overcompensation occurs, the effect of the present invention becomes less and there is a possibility of a runaway, so it is necessary to make sure that the compensation is insufficient.

As shown in FIG. 3A, the off-track detecting means 10 is provided with two detection circuits 12 and 13 having different time constants, each of which has an output of the optical pickup 3 as an input and has a DC component appropriately set. It is composed of a comparator 14 for comparing the output levels of the. FIG. 3B shows the operation waveform. Regarding the time constants of the two detection circuits, even when the disc with the maximum eccentricity according to the disc standard is reproduced and the tracking offset of the optical pickup 3 becomes large, it is not recognized as an off-track, and the slice level of the waveform shaping means 4 is not recognized. Set to recognize that the track is off before it can no longer follow.

Although not shown in FIG. 5, the track-off detection signal is once input to a microcomputer controlling the entire system, and then the output of the microcomputer controls ON / OFF of the switch 11. Good.

Although the switch 11 is also arranged between the motor control means 6 and the loop filter 7 in FIG. 1, it may be arranged between the loop filter 7 and the driver 8 or the driver 8 may be arranged. It may be configured to be inserted between the spindle motor 2 and the spindle motor 2.

Although it has been stated that the longest cycle detecting means 5 detects the longest cycle after performing the edge detection, it is not always necessary to detect the edge, and the longest cycle is directly detected from the output of the waveform shaping means 4, and the The motor control means 6 may be caused to function so that the longest cycle matches 22T.

[0020]

As described above, according to the present invention, it is possible to prevent a runaway state by detecting the off-track of the optical pickup, stopping the drive of the spindle motor at the time of the off-track, and setting the free run. It is possible.

[Brief description of drawings]

FIG. 1 is a block diagram of a coarse servo system of a spindle motor of an optical disk reproducing device according to an embodiment of the present invention.

FIG. 2 is an operation waveform diagram of each part in the embodiment shown in FIG.

FIG. 3A is a circuit diagram of a configuration example of a track deviation detecting means. (B) is an operation waveform diagram thereof.

FIG. 4 is an explanatory diagram of a signal format on a compact disc.

FIG. 5 is a block diagram of a coarse servo system of a spindle motor of a conventional optical disc reproducing apparatus.

6 is an operation waveform diagram of each part in the conventional example shown in FIG.

[Explanation of symbols]

 1 Compact Disc 2 Spindle Motor 3 Optical Pickup 4 Waveform Shaping Means 5 Longest Period Measuring Means 6 Spindle Motor Controlling Means 7 Loop Filter 8 Driver 9 Reference Clock Generating Means 10 Track Off Detection Means 11 Switches 12, 13 Detection Circuits 14 Comparator

Claims (1)

[Claims] 1. CL on a spiral track on an optical disk
An optical disc reproducing apparatus for reading and reproducing digital data of a finite period recorded in a V (constant linear velocity) mode, comprising a spindle motor for rotating the disc,
An optical pickup that traces on the track and reads digital data, a longest period measuring unit that measures the longest period of finite period digital data read by the optical pickup, and a longest period measured by the longest period measuring unit are predetermined. Motor control means for controlling the rotation speed of the spindle motor so as to coincide with the cycle, track deviation detecting means for detecting that the optical pickup has caused a track deviation, and output according to the track deviation detecting means. An optical disk reproducing apparatus comprising: a switch for turning on / off transmission of an output of the spindle motor control means to the spindle motor.