JPH0528571Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an optical disk player, and in particular, the focus servo does not come off when the disk starts rotating, and moreover, the focus servo does not come off when the disk starts rotating, and moreover, the focus servo does not come off due to scratches on the disk during steady rotation. This invention relates to an optical disc player in which the servo does not come off.

<Prior art> Compact disk player (CD player)
is equipped with a focus servo control device, which generates a focus error signal having a voltage value according to the distance between the objective lens and the disk, and performs servo control using the focus error signal to keep the distance constant. In other words, the position of the objective lens relative to the disk surface is controlled so that the disk surface always becomes the focal plane.

By the way, in order for the focus servo circuit to start up, the distance between the objective lens and the disk reflective surface must be close to the depth of focus to some extent. Therefore, immediately after the disk is loaded on the turntable, the objective lens must be moved to a position where the focus servo is applied. Therefore, as shown in Figure 4a, normally the focus servo is applied using a low-frequency focus search signal (1 to 2 Hz triangular wave signal) FS until the focus servo is applied, for example, to the in-focus point (where the focus matches the reflective surface of the disk). The objective lens is moved to the position of the objective lens when
Using FE (see Figure 4b), focus servo is performed so that the objective lens is located at the focal point.

Additionally, CD players are equipped with a defect detection circuit that detects scratches and dust on the disc.
When these scratches or dust are detected, the focus servo control based on the focus error signal is stopped to prevent the focus servo from coming off due to scratches or the like.

Fig. 5 is a waveform diagram explaining the operation of the defect detection circuit, in which a shows the RF signal (RFS) output from the optical pickup, and b shows the envelope waveform signal (RFE) of the RF signal. Figure c is a signal obtained by slicing the envelope waveform signal RFE at a predetermined level. If there is a scratch on the disk, the envelope waveform signal RFE fluctuates by a considerable amount at the scratch, so by slicing at a predetermined level, the defect detection signal DDS shown in Figure c can be obtained. And this defect detection signal DDS
becomes a focus servo stop signal and is applied to the focus servo control section, during which time the focus servo control is stopped.

<Problem that the invention is trying to solve> Now, in a CD player, the rotation of the disc is controlled so that the linear velocity is constant, but it takes a considerable amount of time to reach the predetermined linear velocity when the disc is started. It takes. Then, when the rotation starts, the RF signal RFS and the envelope waveform signal RFE become low frequency signal waveforms as shown by periods T in FIG. As shown in c, a defect detection signal DDS is generated and the focus servo control is stopped. For this reason, focus servo control is no longer performed (the focus error signal is turned off), and there is a problem that the focus servo control cannot be performed at startup.

In view of the above, an object of the present invention is to provide an optical disk player that can be pulled into the focus servo when the disk starts rotating, and that does not cause the focus servo to come off due to scratches on the disk during steady rotation.

<Means for solving the problems> Fig. 1 is a block diagram of the main parts of a CD player according to the present invention.

11 is a disk, 12 is an optical pickup, 12
a is an objective lens, 13 is an RF amplifier, 14 is a digital signal processing circuit, 15 is a focus servo control unit,
16 is a spindle motor, 17 is a CLV circuit, 1
8 is a defect detection circuit, and 19 is a defect control circuit.

<Function> The built-in synchronization code detection circuit 19a detects the disk 11.
Until detecting the synchronization code recorded in
The generation of FSS is prohibited, and the focus servo control section 15 is caused to execute focus servo.

When the synchronization code is detected, it is assumed that the rotational speed of the disk has exceeded the predetermined linear speed.
Thereafter, if the defect detection circuit 18 detects a scratch or the like, the focus servo stop signal FSS is applied to the focus servo control 15 during this time to stop the focus servo control and prevent the focus servo from coming off due to the scratch. .

<Embodiment> FIG. 1 is a block diagram of the main parts of a CD player according to the present invention.

11 is a compact disk, 12 is an optical pickup, 12a is an objective lens, 13 is an RF amplifier,
14 digital signal processing circuit, 15 focus servo control section, 16 spindle motor, 17
CLV circuit, 18 is a defect detection circuit, 19
is a defect control circuit.

Acoustic signals are digitally recorded on the compact disk 11, and control data called frame synchronization codes and subcoding are recorded for each predetermined number of data. The optical pickup 12 optically reads digital information recorded on the compact disk 11 and inputs it to the RF amplifier 13.
The RF amplifier 13 amplifies the RF signal output from the optical pickup 12 and sends it to the digital signal processing circuit 14.
is input to the defect detection circuit 18 and the defect control circuit 19. Note that a signal (referred to as an EFM signal) obtained by waveform shaping an RF signal at a predetermined slice level is input to the digital signal processing circuit 14 and the defect control circuit 19.

The digital signal processing circuit 14 demodulates the EFM signal, separates the audio data and sub-coding, performs error detection/correction processing on the audio data, inputs it to a DA converter (not shown), and further outputs the Q channel of the sub-coding. is analyzed and data indicating the current song number, elapsed time for each song, total elapsed time, etc. is extracted and displayed as appropriate.

The CLV circuit 17 detects the shortest or longest pulse included in the signal read from the disk at startup, and multiplies the length of the shortest or longest pulse (3T or 11T if the bit length is T) by 588/3 or
A pseudo synchronization signal is generated by multiplying by 588/11, and this is regarded as a regeneration synchronization signal to control the rotation of the spindle motor to the extent that the synchronization signal can be regenerated.After the synchronization signal is regenerated, the linear velocity is controlled at a constant level based on the synchronization signal. is going on.

The focus servo control unit 15 includes a focus error signal detection circuit 1 that generates a focus error signal FE having a value corresponding to the distance to the in-focus point of the objective lens, and a focus error signal detection circuit 1 that generates a focus error signal FE having a value corresponding to the distance to the in-focus point of the objective lens, and a focus error signal detection circuit 1 that detects when the objective lens has reached the vicinity of the in-focus point. A detection circuit 2 for detecting near-focus point and generating a signal FOK moves the objective lens using a focus search signal to a position where the focus servo is applied after loading the disk, and then uses a focus error signal FE to move the objective lens to the position where the focus servo is applied. A focus servo circuit 3 that performs focus servo, and a focus drive circuit 4 that drives an actuator (not shown)
have. In addition, the focus servo circuit 3 is
As shown in FIG. 2, a focus search signal generation section 3a, a reference voltage generation section 3b, an in-focus point arrival detection section 3c, a drive signal switching control section 3d, signal changeover switches 3e and 3f, and a combining circuit 3g and a focus servo correction section 3h.

The defect detection circuit 18 has the same configuration as the conventional one, and includes an envelope detection circuit 18a that detects and outputs the envelope waveform signal RFE of the RF signal that is the output of the RF amplifier 13, and an envelope detection circuit 18a that slices the envelope waveform signal at a predetermined slice level. It is composed of a waveform shaping circuit 18b. If there is a scratch on the disk, the envelope waveform signal RFE fluctuates by a considerable amount at the scratch, so by slicing at a predetermined level, the defect detection signal DDS can be obtained (see FIG. 5). When the disk is rotating at a constant linear velocity, this defect detection signal DDS becomes a focus servo stop signal FSS and is applied to the focus servo control section 15 to stop the focus servo control.

The defect control circuit 19 is an EFM
It is composed of a synchronization code detection circuit 19a and an AND gate 19b, which generates a high-level synchronization code detection signal SSD after detecting a synchronization code from the signal. Note that the detection of the synchronization code means that the linear velocity of the disk has fallen within several percent of the target linear velocity. AND gate 19b is synchronization code detection signal SSD and defect detection signal DDS
Find the focus servo stop signal FSS by calculating the AND of
Output.

The operation of the CD player according to the present invention will be explained below with reference to FIGS. 1 and 2.

If you place the disc on the turntable and insert it into the CD player, the disc loading signal DST (second
Figure) occurs. When the disk loading signal DST is generated, the drive signal switching control section 3d switches the switch 3e.
Turn on and turn off switch 3f. This results in
The focus search signal FS generated from the focus search signal generation section 3a is applied to the focus drive circuit 4 (FIG. 1) via the synthesis circuit 3g and the focus servo correction section 3h, and the focus drive circuit 4 is not shown in the figure. The objective lens 12a is moved toward the focal point by driving the actuator that does not move.

On the other hand, in parallel with the control by the focus search signal, the CLV circuit 17 (FIG. 1) controls the rotation of the spindle motor 16 as described above. As a result, the linear velocity of the disk increases from zero toward the target linear velocity.

By the way, since the rotational speed of the disk is low when the disk starts rotating, the synchronization code detection circuit 19a
Since it does not detect a synchronization code, its output is at a low level, and the focus servo stop signal FSS, which is the output of the AND gate 19b, is at a low level regardless of the level of the defect detection signal DDS.

As a result, the focus servo does not stop when the disk starts rotating, and the objective lens moves in response to the focus search signal FS (see Figure 2). Figure 1) Signal FOK arriving near the in-focus point
is output. Thereafter, when the objective lens moves further and reaches the in-focus point, the focus error signal FE crosses the reference voltage V _R (Fig. 2), so the in-focus point arrival detection section 3c generates the in-focus point arrival signal FAR. .

The drive signal switching control unit 3d switches the in-focus point arrival signal FAR when the near-in-focus point arrival signal FOK is at a high level.
When this occurs, switch 3e is turned off and switch 3f is turned off.
Turn on. Thereby, the focus error signal FE outputted from the focus error signal detection circuit 2 is inputted to the focus drive circuit 4 via the synthesis circuit 3g and the focus servo correction section 3h, and focus servo is performed. .

In parallel with such focus servo control, when the linear velocity of the disk falls within several percent of the target linear velocity, the synchronization code detection circuit 19a (FIG. 1) detects the synchronization code, and thereafter outputs a high-level synchronization code detection signal. Output SSD.

As a result, focus servo control is executed/determined depending on the level of the defect detection signal DDS.
Controlled outage. That is, when the defect detection circuit 18 detects a scratch on the disk and the defect detection signal DDS becomes high level, the focus servo stop signal FSS becomes high level. When the focus servo stop signal FSS becomes high level, the drive signal switching control section 3d (Fig. 2) turns off both switches 3e and 3f to open the servo loop.
Stops focus servo control using focus error signal FE. Then, as soon as there are no more scratches and the defect detection signal DDS becomes low level, the drive signal switching control section 3d turns on the switch 3f to close the servo loop, and thereafter resumes focus servo control using the focus error signal FE. .

In addition, in the above, it was determined whether the linear velocity of the disk has exceeded a predetermined linear velocity based on whether or not a synchronization code was detected, but as shown in Figure 3, instead of the synchronization code detection circuit, the time after startup is determined. A high-level time-over signal is generated when a predetermined time elapses.
A timer 21a that outputs TOV is provided, and when the time-over signal is generated, it is assumed that the disk has reached a predetermined speed or higher, and after that, the AND gate 21b is opened and the output signal of the defect detection circuit 18 is output as the focus servo stop signal FSS. It may be configured to do so.

Furthermore, in the above, the output of the defect detection signal DDS was controlled according to the linear velocity of the disk, but the output of the defect detection signal DDS is controlled according to the linear velocity of the disk.
It is also possible to configure the input to be controlled according to the linear velocity.

Furthermore, although the case of a CD player has been described above, the present invention can also be applied to a video disc player and the like.

<Effect of the invention> According to the invention, generation of the focus servo stop signal is prohibited when the rotational speed of the disk is below a predetermined linear velocity, and when the rotational speed of the disk exceeds the predetermined linear velocity. If a scratch or the like is detected afterwards, the focus servo control is stopped during that time, so it is possible to reliably engage the focus servo when the disk starts rotating, and it also prevents the focus servo from being activated due to scratches on the disk during steady rotation. It never comes off.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of the CD player according to the present invention, FIG. 2 is a block diagram of the focus servo circuit, FIG. 3 is another block diagram of the CD player according to the present invention, and FIGS. 4 to 6 The figure is a waveform diagram for explaining the drawbacks of the prior art. 11...Compact disk, 12...Optical pickup, 13...RF amplifier, 15...Focus servo control section, 16...Spindle motor, 1
8... Defect detection circuit, 18a... Envelope detection circuit, 19... Defect control circuit, 19a... Synchronization code detection circuit.

Claims (1)

[Claims for Utility Model Registration] (1) A focus servo control unit that performs focus servo control by generating a focus error signal so that the focus of the objective lens matches the reflective surface of the disk; a defect detection section that generates a signal to stop the focus servo control when a scratch on the disk is detected using an RF signal; An optical disc player comprising a prohibition circuit that prohibits generation of a stop signal. (2) The prohibition circuit includes a synchronization code detection circuit that detects the synchronization code recorded on the disk, and a gate circuit that prohibits the focus servo stop signal from being generated from the defect detection section until the synchronization code is detected. An optical disc player according to claim (1) of the utility model registration claim. (3) The prohibition circuit includes a timer that measures time from the start of rotation of the disk, and a gate circuit that prohibits the focus servo stop signal from being generated from the defect detection section until a predetermined period of time has elapsed from the start of time measurement. An optical disc player according to claim (1) of the utility model registration.