JPH0410278A - Optical disk reproducing device - Google Patents

Abstract

PURPOSE:To stabilize a spindle motor control by providing a changeover circuit and highly setting a gain of a frequency characteristic of a main signal amplifier only at the time of a seek operation for moving an optical pickup from the inner circumference to the outer circumference. CONSTITUTION:In the optical disk reproducing device for optically reading out a signal recorded on a disk at a constant linear velocity, a signal for forcedly moving the optical pickup from the inner circumference to the outer circumference of the disk is also sent to a changeover circuit 4 from a traverse motor control device 12, and when the forced signal is received by the changeover circuit 4, the frequency gain of the main signal amplifier 3 is changed, so as to raise the frequency characteristic gain of the amplifier 3 in a band of high frequencies and small amplitudes of a read signal. By this method, high amplitudes and low amplitudes of the read signal can be equalized, and even when a data slice level is lowered, the spindle motor control by a seek control can stably and promptly be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for appropriately controlling a spindle motor during random access in an optical disc reproducing device.

[Conventional technology]

As described in Hitachi's 2nd Generation CD Semiconductor Application Note, System Edition, p. 58, conventional optical disc playback devices receive the music or video signal recorded on the disc as the main signal with a detector, and generate a current. The photocurrent was converted into voltage by a voltage converter, amplified by a main signal amplifier, and then converted into a binary signal based on the slice signal by an EFM comparator circuit.

By the way, the frequency of the reproduced signal converted by the current-voltage converter is 196 kHz to 720 kHz, and since the gain of this frequency decreases from the middle of the reproduced frequency band, the amplifier adjusts the amplitude etc. to compensate for the decreased gain. was undergoing transformation.

[Problem to be solved by the invention]

The conventional optical disc reproducing apparatus described above controls the rotation of the spindle motor so that the linear velocity of the rotation of the disc is constant between the inner and outer circumferences.

Therefore, when the optical pickups are on the inner and outer peripheries,
The rotational speed of the disk is controlled to be different, and when random access or other seek is performed from the inner circumference to the outer circumference, the rotational frequency of the disk is controlled from high speed to low speed. FIG. 4 shows the EFM signal output from the current-voltage converter. If the EFM 3T playback signal, which is the pit information read signal, plays back a disc whose asymmetry is shifted as shown by the dotted line, the slice signal input to the data slice level control device 7 shown in FIG. Since the signal input to the signal processing device 6 is buffered and passed through a low-pass filter, the slice level appears to be lower than it should be. Therefore, the 6th
As shown in the figure, when the lens for reading information on the disc is moved from the inner circumference to the outer circumference, a situation occurs in which edges of the 3T signal, which generally has a lower modulation degree than 11T, are not detected. For this reason, the digital signal processing device 6 incorrectly judges that the maximum time width (for example, T) of the output signal of the digital signal converter 5 that is responsible for rotation control during seek is longer than the true length. It determines that the rotation speed of the spindle motor that rotates the disk is lower than the desired rotation speed, and sends a signal to the spindle motor to increase the rotation speed. Because of this, the rotation of the spindle motor becomes faster than the appropriate rotation speed, and the modulation degree of the EFM signal further decreases.EF
The edge of the M signal cannot be detected, and the spindle motor rotates at high speed, making it inaccessible.

[Means to solve the problem]

In order to solve the above problem, the present invention provides a main signal amplifier 3
Therefore, it is sufficient to amplify the EFM signal to a slightly higher level to prevent the digital signal converter 5 from not detecting edges of the EFM signal even if the data slice level decreases.

Incidentally, the amplitude of the EFM signal input to the main signal amplifier 3 deteriorates at high frequencies. For this reason,
Conventionally, in order to correct this deterioration, the main signal amplifier 3 has been designed to
Amplitude equalization is performed by applying frequency characteristics that increase gain in high frequency bands where modulation deteriorates. Therefore, if the EFM signal is always amplified to a high level by amplifier 3 (dotted line in Figure 5), the EF
Since the M signal is given more gain than it should be, and the signal output from the data slice level control device W7 has a higher amplitude than it should, the digital signal processing device 6 will process incorrect data. , the error rate increases and accurate audio cannot be reproduced. Therefore, in the present invention, the gain of the frequency characteristic of the main signal amplifier is set high as shown by the dotted line in FIG. 5 only while no data reading operation is performed. In other words, a switching circuit 4 is provided to switch the frequency characteristics of the main signal amplifier 3, and the frequency characteristics of the amplifier are switched to a higher one (dotted line in Figure 5) only during a seek operation to move the optical pickup from the inner circumference to the outer circumference. It is something to do.

By the way, in an optical disc playback device, during a seek operation in which the optical pickup is forcibly moved, the FE
The spindle motor is controlled by detecting the maximum time width of the M reproduction signal. Note that in this seek operation, the system control device 15 does not read the data. Therefore, switching in the switching circuit 4 is performed using a forced signal to the traverse motor.

[Effect]

In the optical disc playback device, a control signal for forcibly moving the optical pickup from the inner circumference to the outer circumference of the disk is sent from the system control device 15 to the traverse motor drive device 1.
Sent to 2. Here, the forcing signal is sent to the traverse motor drive device 13 and also to the switching circuit 4 that drives the traverse motor. The switching circuit 4 receives the forced signal and switches the high frequency gain of the main signal amplifier from the solid line shown in FIG. 5 to the dotted line frequency characteristic. As a result, even if the slice level is lowered due to asymmetry, it is possible to increase the amplitude of the 3T signal, which has a small amplitude, so that the etch can be sufficiently detected. There is no need to judge, and it is possible to avoid an inaccessible state due to high speed rotation of the spindle motor.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram schematically showing an optical disc device, for example a CD player.

The optical pickup 17 functions to irradiate convex signals called pits on the disk with a laser beam and read signals on the disk based on the strength of the reflected light. The optical pickup 17 includes a traverse mechanism that moves in the radial direction, a traverse motor 18 that drives the traverse mechanism, and
It has a focus control function so that the laser beam is focused on the disk, and a tracking control function so that the laser beam tracks the pit row. The signal read by the optical pickup 17 is transferred to a current-voltage converter 20.
The main signal is further sent to the digital signal converter 21
Here, the digital signal is converted into a binary signal, and then sent to the digital signal processing device 6, and further sent to the spindle motor drive device 25, which controls the rotation of the disk, to drive the spindle motor to record on the disk. Control the surface so that the linear velocity is constant. On the other hand, the binarized signal is sent to the audio reproduction device 26, where it is demodulated and output as a music signal. By the way, focus and tracking control is performed by converting the signal converted by the current-voltage converter 20 into the focus and tracking control device 22. Focus passes through the tracking coil drive device 23 and focuses.

This is done by sending the signal to a tracking coil.

FIG. 1 is a device block diagram showing one embodiment of the present invention. A signal recorded on the disk is detected by a main beam detector 1, and a current-voltage converter 2 converts the photocurrent into a voltage. The signal converted to voltage is subjected to amplitude equalization in the main signal amplifier 3 to compensate for the optical frequency characteristics.

That is, the frequency characteristics of the main signal amplifier 3 are such that, as shown in FIG. 5, the gain is high in a high frequency band where the amplitude of the read signal is small in the reproduction frequency band. This allows the main signal amplifier 3 to equalize the amplitudes of the high-amplitude and low-amplitude read signals.

The amplitude-equalized signal is converted into a digital signal by a digital signal converter 5 and sent to a digital signal processing device 6. Here, it is demodulated and converted into an audio signal. The data slice level used by the digital signal converter 5 is set by a data slice level control device 7. The data slice level is controlled by the digital signal processing device 6.
The input signal is buffered and passed through a low-pass filter.

By the way, for example, in double-speed playback, where the disk is rotated at a high speed for the purpose of shortening data transmission time, when a seek operation is performed to move the optical pickup from the inner circumference to the outer circumference of the disk. , as the rotational speed of the disk increases, the reproduction reading frequency increases accordingly.

For this reason, when a disc with misaligned asymmetry is played back, for example, the 3T signal becomes a 3T signal as shown by the dotted line as shown in FIG. 4, and the data slice level becomes lower than the original amplitude.

For this reason, when a seek operation is performed, as shown in FIG. 6, there are cases where the intended pulse cannot be detected, and the signal with the maximum time width appears to be wide. Therefore, the digital signal processing device 6 determines that the linear velocity of the disk is lower than the appropriate speed, and erroneously controls the spindle motor to rotate at a high speed.

Note that this phenomenon will not occur if a seek operation is performed from the outer circumference with a low rotation speed to the inner circumference with a high rotation speed, since the rotation speed must be increased in order to achieve the appropriate linear speed of the disk. .

Therefore, in the present invention, the system control device 15 connects the optical pickup 17 to the traverse control device 12 with respect to the disk 1.
When a seek operation signal is forcibly sent from the inner circumference to the outer circumference of the sensor 6, the seek operation signal is simultaneously sent to the switching circuit 4. As a result, the traverse motor 14 is driven to forcibly move the optical pickup 17 in the outer circumferential direction, and at the same time causes the switching circuit 4 to switch the frequency gain of the main signal amplifier, and the frequency characteristics of the amplifier are shown in FIG. Switch from the frequency characteristic shown by the solid line to the frequency characteristic shown by the dotted line.

FIG. 3 shows the relationship between the main beam reproduction signal and the switching signal. The switching signal becomes H level when the traverse motor is driven to forcibly move the optical pickup 17 from the inner circumference to the outer circumference of the disk 16, and the switching operation is performed only when the switching signal is at the H level.

Therefore, even if the slice level decreases, the digital signal converter 5 can detect even the edges of the EFM signal with low amplitude, and the digital signal processing device 6 can prevent erroneously determining the maximum time width of the EFM signal. The spindle motor can be controlled stably.

〔Effect of the invention〕

According to the present invention, in an optical disc reproducing apparatus that rotates a disc at high speed to reproduce the disc, the spindle motor can be controlled stably and instantaneously by seek control.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of an optical disc reproducing apparatus according to an embodiment of the present invention, and FIG. 3 is a block diagram of a main beam reproduction signal and a switching signal. FIG. 4 is a diagram showing the EFM signal output from the current-voltage converter. FIG. 5 is a diagram showing the frequency characteristics of the main signal amplifier. FIG. 6 is a diagram showing the data slice level and EFM signal. FIG. 3... Main signal amplifier 4... Switching circuit 7...
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Claims (1)

[Claims] 1. In an optical disc playback device that optically reads out signals recorded on a disc at a constant linear velocity, an optical device that reads data on the disc when an access operation is performed by moving the optical pickup from the inner circumference to the outer circumference. A forced feed signal from the traverse motor that controls the movement of the pickup is sent to a switching circuit that switches the frequency characteristics of the main signal amplifier, and during access operation to move the optical pickup from the inner circumference to the outer circumference, a bit signal is recorded on the disc being played. An optical disc playback device characterized by increasing the gain of high components.