JPH09231662A - Signal processor circuit in optical disk system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal processor circuit capable of securing a superior playability at any velocity mode in the optical disk system in which velocity mode is variable for a spindle speed. SOLUTION: In an optical disk system whose velocity mode is variable for a spindle speed, a high frequency pass filter 18 is constituted of a first capacitor C1 one end of which is connected to the output terminal of a RF (high frequency) amplifier 15, switch SW one end of which is connected to the output terminal of the RF amplifier 15, and a second capacitor C2 which is connected between the other end of the switch SW and the other end of the first capacitor C1. In this case, the time constant of the high frequency pass filter 18 is switched in accordance with the velocity mode of the spindle speed by means of a switch control circuit 16, so that the time constant is set corresponding to each velocity mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing circuit in an optical disc system, and more particularly, to a recording / reproducing of information on / from an optical disc and a rotation speed (hereinafter referred to as spindle speed) of a spindle motor for rotationally driving the optical disc. The present invention relates to a signal processing circuit in an optical disc system having a variable speed mode.

[0002]

2. Description of the Related Art A conventional example of this type of signal processing circuit is shown in FIG. In FIG. 4, the disk 41 is rotationally driven by a spindle motor 42, and the recorded information is read by an optical pickup 43. The RF (high frequency) signal output from the optical pickup 43 is supplied to the RF amplifier 45 in the analog IC 44. RF amplifier 45 and DSP (Digit in the next stage digital IC 46)
al Signal Processor) circuit 47 and a capacitor C
Is connected.

In the conventional signal processing circuit having the above structure,
The capacitor C constitutes a high-pass filter together with the output impedance of the RF amplifier 45. This high-pass filter AC-couples the RF amplifier 46 and the DSP circuit 47 and causes RF due to the warp of the disk 41 or the like. Amplifier 4
This is for attenuating the swell component riding on the output signal of No. 5.

[0004]

By the way, when reproducing an optical disk such as a conventional music CD, the speed mode of the spindle speed is fixed. Therefore, in the conventional signal processing circuit, the time constant value of AC coupling determined by the capacitance value of the capacitor C and the output impedance of the RF amplifier 46 may be fixed. However, in recent years, in order to cope with the speeding up of optical discs such as CD-ROMs, it is possible to set a high speed mode (e.g., 8 times speed) as the spindle speed mode in addition to the standard mode. As described above, when the speed mode of the spindle speed is variable, if the time constant value of the AC coupling remains fixed, the problem such as the warp of the disk cannot be dealt with in the high speed mode, and the playability deteriorates. .

The present invention has been made in view of the above problems, and an object thereof is to ensure good playability in any speed mode in an optical disk system in which the speed mode of the spindle speed is variable. It is to provide a signal processing circuit capable of performing the above.

[0006]

The signal processing circuit according to the present invention is an output signal of an optical pickup for reading recorded information from an optical disk in an optical disk system in which the speed mode of the rotation speed of a spindle motor for rotationally driving the optical disk is variable. The high-frequency circuit that processes the high-frequency circuit, the high-pass filter with a variable time constant that passes the high-frequency component of the output signal of this high-frequency circuit, and the time constant of the high-pass filter according to the speed mode of the spindle motor rotation speed It has a configuration including a control circuit for controlling.

In the signal processing circuit having the above structure, the control circuit switches the time constant of the high-pass filter when the speed mode of the spindle speed changes. The high-pass filter cuts the DC component of the output signal of the high-frequency circuit according to the time constant, and AC-couples the high-frequency circuit and the next-stage circuit.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. In Fig. 1, music CD and CD-RO
Optical disc such as M (hereinafter, simply referred to as disc) 1
1 is rotationally driven by a spindle motor 12, and its recorded information is read by an optical pickup 13. RF output from the optical pickup 13
A undulation component generated due to warpage of the disk 11 or the like is superimposed on the (high frequency) signal. This playback RF
The signal is supplied to the RF amplifier 15 in the analog IC 14 via the input terminal pin 14a.

In the analog IC 14, the output terminal of the RF amplifier 15 is connected to the output terminal pin 14b.
The output end of the RF amplifier 15 is connected to one end of the switch SW, and the other end is connected to the output terminal 14c. The switch SW is on (closed) / off (open) controlled by a switch control circuit 16 provided outside the analog IC 14, for example. The switch control circuit 16 turns on the switch SW in the standard mode at 1 × speed and switches it in the high speed mode (for example, 8 × speed) according to the mode switching information provided from the outside when switching the speed mode of the spindle speed. Turn off the SW.

Outside the analog IC 14, one end of the first capacitor C1 is connected to the output terminal pin 14b,
One end of the second capacitor C2 is connected to the output terminal pin 14c. The other ends of the capacitors C1 and C2 are commonly connected, and the input terminal pin 1 of the digital IC 17 is further connected.
7a. These capacitors C1 and C2
Constitutes a high-pass filter 18 together with the output impedance of the RF amplifier 15. The high-pass filter 18 is for attenuating the swell component that is included in the output signal of the RF amplifier 15 due to the warp of the disk 11 or the like, and its time constant is 2 depending on whether the switch SW is opened or closed.
It is variable in stages.

In the digital IC 17, the input terminal pin 17a is connected to the input terminal of the DSP circuit 19, and the output terminal thereof is connected to the output terminal pin 17b. DS
The P circuit 19 is for digitally performing signal processing such as EFM (Eight to Fourteen Modulation) demodulation and error correction on the reproduction RF signal from the disk 11.

Next, the circuit operation according to the first embodiment having the above configuration will be described. First, when the speed mode of the spindle speed is the standard mode of 1 × speed, the switch control circuit 16 turns on the switch SW based on the mode switching information provided from the outside. This switch SW
In the ON state of, the time constant of the high-pass filter 18 is R
Output impedance Z of F amplifier 15 and capacitor C
It is determined by the parallel combined capacitance value of C1 and C2 (C1 + C2).

On the other hand, when the speed mode of the spindle speed is switched to the high speed mode, the switch control circuit 16
Turns off the switch SW based on the mode switching information given from the outside. In the OFF state of the switch SW, the time constant of the high pass filter 18 is determined by the output impedance Z of the RF amplifier 15 and the capacitance value of the capacitor C1.

By the way, the speeded-up optical disk does not always continue to rotate at a high speed, and even if the maximum speed is, for example, 8 times, the rotation speed is reduced when the error rate deteriorates. Here, the error rate is a value of (the number of frames in which the error cannot be corrected / the total number of frames) during the error correction processing in the DSP circuit 19. When playing a music CD, the spindle speed is set to the standard mode.

As described above, when the speed mode of the spindle speed is switched, the time constant of the high-pass filter 18 is switched according to the speed mode and the time constant corresponding to the speed mode is set. In the case of the high speed mode such as the 8 × speed, the time constant of the high pass filter 18 becomes small and the problem such as the scratch on the disk 11 can be dealt with, so that good playability can always be secured regardless of the speed mode. . Moreover, switch SW is IC
By mounting it inside, the cost of the entire set can be reduced.

As a method of switching the time constant of the high pass filter 18 according to the speed mode of the spindle speed, a method of selectively selecting the two capacitors C1 and C2 can be considered, but in the case of this method It is necessary to use a capacitor having a large capacitance value as the capacitor that determines the time constant of the high-pass filter 18 in the standard mode. However, in the present embodiment, the time constant of the high-pass filter 18 is set by using the parallel combined capacitance value (C1 + C2) of the capacitors C1 and C2. Therefore, it is preferable to use a capacitor having a small capacitance value as the capacitor C2. There is an advantage that you can.

FIG. 2 is a block diagram showing a second embodiment of the present invention. In FIG. 2, the disk 21 is rotationally driven by a spindle motor 22, and the recorded information is read by an optical pickup 23. The RF signal output from the optical pickup 23 has a swell component generated due to the warp of the disk 21 and the like. This reproduction RF signal is an analog IC2
4 is supplied to the RF amplifier 25 in the No. 4 via the input terminal pin 24a.

In the analog IC 24, the output terminal of the RF amplifier 25 is connected to the output terminal pin 24b.
Further, one end of the switch SW is connected to the output end of the RF amplifier 25, and the other end is connected to the output terminal 24c. The switch SW is on / off controlled by a switch control circuit 26 provided outside the analog IC 24, for example. The switch control circuit 26 turns off the switch SW in the standard mode at 1 × speed and switches it in the high speed mode (for example, 8 × speed) according to the mode switching information given from the outside when the speed mode of the spindle speed is switched. Turn on the SW.

Outside the analog IC 24, one end of the first resistor R1 is connected to the output terminal pin 24b, and one end of the second resistor R2 is connected to the output terminal pin 24c. The other ends of the resistors R1 and R2 are commonly connected. The other end of each of the resistors R1 and R2 is connected to one end of a capacitor C, and the other end is connected to an input terminal pin 27a of the digital IC 27. The resistors R1 and R2 and the capacitor C form a high pass filter 28. The high-pass filter 28 is for attenuating the swell component that is included in the output signal of the RF amplifier 25 due to the warp of the disk 21 and the like, and its time constant is changed in two steps according to the opening / closing of the switch SW. Is.

In the digital IC 27, the input terminal pin 27a is connected to the input terminal of the DSP circuit 29, and the output terminal thereof is connected to the output terminal pin 27b. DS
The P circuit 29 is for digitally performing signal processing such as EFM demodulation and error correction on the reproduced RF signal from the disk 21.

Next, the circuit operation according to the second embodiment having the above configuration will be described. First, when the speed mode of the spindle speed is the standard mode of 1 × speed, the switch control circuit 26 turns off the switch SW based on the mode switching information given from the outside. This switch SW
In the off state of, the time constant of the high pass filter 28 is determined by the resistance value of the resistor R1 and the capacitance value of the capacitor C.

On the other hand, when the speed mode of the spindle speed is switched to the high speed mode, the switch control circuit 26
Turns on the switch SW based on the mode switching information given from the outside. In the ON state of the switch SW, the time constant of the high pass filter 28 is equal to the resistance R
Parallel combined resistance value of R1 and R2 (R1R2 / (R1 + R
2)) and the capacitance value of the capacitor C.

As described above, the time constant of the high-pass filter 28 is switched according to the speed mode of the spindle speed, and the time constant corresponding to the speed mode is set. Similarly, in the case of a high speed mode such as 8 × speed, the time constant of the high pass filter 28 becomes small, and problems such as scratches on the disk 21 can be dealt with, so that good playability is always ensured regardless of the speed mode. be able to.

FIG. 3 is a block diagram showing a third embodiment of the present invention. In FIG. 3, the disk 31 is rotationally driven by a spindle motor 32, and the recorded information is read by an optical pickup 33. The RF signal output from the optical pickup 33 has a swell component generated due to the warp of the disk 31 and the like. This reproduction RF signal is an analog IC3
4 is supplied to the RF amplifier 25 in the No. 4 via the input terminal pin 34a.

In the analog IC 34, the output end of the RF amplifier 35 is connected to the input end of a high pass filter (HPF) 36, and the output end thereof is connected to the output terminal pin 34b. The high-pass filter 36 is for attenuating the waviness component on the output signal of the RF amplifier 35 due to the warp of the disk 31. The high-pass filter 36 is composed of, for example, an active filter, so that its cutoff frequency fc is continuously variable.

The analog IC 34 further controls the cutoff frequency fc of the high-pass filter 36 according to the mode switching information provided from the outside when the speed mode of the spindle speed is switched, so that the cut corresponding to the speed mode is performed. An fc control circuit 37 for setting the off frequency fc is built in. The input terminal pin 38a of the digital IC 38 is connected to the output terminal pin 34b of the analog IC 34.

In the digital IC 38, the input terminal pin 38a is connected to the input terminal of the DSP circuit 39, and the output terminal thereof is connected to the output terminal pin 38b. DS
The P circuit 39 is for digitally performing signal processing such as EFM demodulation and error correction on the reproduced RF signal from the disk 31.

Next, the circuit operation according to the third embodiment having the above configuration will be described. First, the high pass filter 36
Is composed of an active filter, and its cutoff frequency fc is continuously variable. Therefore, the speed mode of the spindle speed is, for example, 1 × speed, 2 × speed, 4 × speed, 6 ×.
Even when the speed is set in multiple stages such as double speed and 8 times speed, it is possible to set the optimum cutoff frequency fc corresponding to each speed mode.

Therefore, the fc control circuit 37 controls the time constant of the high pass filter 36 according to the mode switching information given from the outside when the speed mode of the spindle speed is switched, so that the high pass filter 3 is controlled.
The cutoff frequency fc of 6 is set to an optimum value corresponding to the speed mode.

As described above, the cutoff frequency fc of the high pass filter 36 is controlled by controlling the time constant of the high pass filter 36 according to the speed mode of the spindle speed.
Is set to a value corresponding to the speed mode, the time constant of the high-pass filter 36 becomes small in the case of the high speed mode such as 8 × speed as in the first and second embodiments. Since problems such as scratches on the disk 31 can be dealt with, good playability can always be ensured regardless of the speed mode.

Particularly, when the high-pass filter 36 is composed of an active filter and built in the analog IC 34, the number of external parts of the IC can be reduced and the spindle speed mode can be set in multiple stages. Also, since the cutoff frequency fc of the high pass filter 36 can be set to an optimum value corresponding to each speed mode, the circuit configuration can be simplified as compared with the case of switching the switch.
And the playability can be further improved.

In each of the above embodiments, the case where the circuit portion for performing signal processing such as EFM demodulation and error correction has a digital circuit configuration has been described, but the invention is not limited to the digital circuit configuration and an analog circuit configuration is used. May be

[0034]

As described above, according to the present invention,
In an optical disk system in which the speed mode of the spindle speed is variable, the time constant of the high-pass filter that AC-couples the high-frequency circuit that processes the high-frequency signal read from the optical disk and the circuit in the subsequent stage is set according to the speed mode of the spindle speed. By controlling the speed and setting it to a value corresponding to the speed mode, problems such as scratches on the optical disk can be dealt with even in the high speed mode, so good playability can be secured in any speed mode. become.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a block diagram showing a conventional example.

[Explanation of symbols]

11, 21, 31 Disc 12, 22, 32 Spindle motor 13, 23, 33 Optical pickup 15, 2
5,36 RF amplifier 16,26 Switch control circuit 18,28 High-pass filter 37 fc Control circuit 19,29,39 DSP circuit

Claims (4)

[Claims] 1. A high-frequency circuit for processing an output signal of an optical pickup for reading recorded information from the optical disk in an optical disk system in which a speed mode of a rotation speed of a spindle motor for rotationally driving the optical disk is variable; A high-pass filter having a variable time constant for passing the high-pass component of the output signal, and a control circuit for controlling the time constant of the high-pass filter according to the speed mode of the rotation speed of the spindle motor are provided. Signal processing circuit characterized by. 2. The high pass filter has a first capacitor whose one end is connected to an output end of the high frequency circuit, and one end which is connected to an output end of the high frequency circuit, and is turned on / off by the control circuit. The signal processing circuit according to claim 1, further comprising: a switch element that is configured to operate, and a second capacitor that is connected between the other end of the switch element and the other end of the first capacitor. 3. The high pass filter includes a first resistor having one end connected to an output end of the high frequency circuit, and the first resistor.
A resistor whose one end is connected to the other end of the resistor, a switch element whose one end is connected to the output end of the high-frequency circuit and which is on / off controlled by the control circuit, the other end of the switch element and the first 2. The signal processing circuit according to claim 1, further comprising a second resistor connected between the resistor and the other end thereof. 4. The high-pass filter is an active filter and is incorporated in the same IC as the high-frequency circuit, and the control circuit sets the high-pass filter according to a speed mode of a rotation speed of the spindle motor. 2. The signal processing circuit according to claim 1, wherein the cutoff frequency of the band pass filter is controlled.