JPH0512678A - Disk device - Google Patents

Abstract

PURPOSE:To prevent a data signal taken out from the cathode of a photodiode from being influenced by a tracking signal taken out from the anode by converting the detection current of an optical head to voltage only at a low band, by-passing a high frequency component and simultaneously converting it to voltage at a high band. CONSTITUTION:A tracking signal inclusive of a data signal and a header signal is outputted by using the current from photodiodes 8a, 8b by a preamplifier 36. That is, the anode side of the diodes 8a, 8b are converted to current/voltage by a low speed amplifiers 52, 53 for making the tracking signal. Further, the signal from the cathode is supplied to the inverted input side of a high speed amplifier 51, converted to the voltage and becomes the header signal and the data signal. At this time, since the high frequency current flows to the diodes 8a, 8b by capacitors C1, C2, the high speed current is taken out by a high speed amplifier 51.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk device for recording or reproducing information on an optical disk, for example.

[0002]

As is well known, for example, information is recorded on an optical disk or information recorded on the optical disk is detected in the optical head by a laser beam output from a semiconductor laser oscillator (light source) in the optical head. After converting into an electric signal using a device, by converting into a video signal,
Various optical disk devices for reading have been developed.

In such an optical disk device, in order to take out a data signal, a signal is taken out from one side of the anode (or cathode) of the photodiode and current-voltage conversion is performed using a high speed amplifier. Furthermore, three high-speed amplifiers are required because the sum of each signal is taken out by the high-speed amplifier. For this reason, there is a problem in that the cost is increased, and high-speed signals are processed in two stages, so that it is difficult to obtain frequency characteristics due to the influence of the capacitance of wiring and the like.

Therefore, a method of taking signals from both the anode and cathode of the photodiode (for example, taking a sum signal from the cathode and taking a tracking signal or a focusing signal from the anode side) has been considered.

In this case, the photodiode is reversed by 5
If a bias of V or more is not applied, the capacity will increase and the frequency characteristics will not appear. Therefore, the power supply currently used is mostly + 12V single power supply. In such a case, the power supply is small. / It was difficult to get signals from both cathodes. Therefore, the problem is solved by adding a bias component at the same time that the signal is converted from current to voltage by the preamplifier circuit.

However, when the tracking signal (focusing signal) is taken from the anode side of the photodiode, the photodiode is affected by the frequency characteristic of the preamplifier circuit.
The current flowing through the cathode is restricted, and the signal extracted from the cathode is affected by the signal extracted from the anode.

[0007]

SUMMARY OF THE INVENTION In the present invention, when the tracking signal or the focusing signal is taken from the anode side of the photodiode, the current flowing through the diode is restricted by the frequency characteristic of the preamplifier circuit, and the data taken out from the cathode is taken. This is to eliminate the drawback that the signal is affected by the signal extracted from the anode. When the tracking signal or focusing signal is taken from the anode side of the photodiode, the current flowing through the photodiode due to the frequency characteristics of the preamplifier circuit. It is an object of the present invention to provide a disk device which is not subject to restrictions and is not affected by a signal taken out from an anode on a data signal taken out from a cathode.

[0008]

DISCLOSURE OF THE INVENTION In a disk device of the present invention, an optical head for photoelectrically converting light detected by irradiating a disk with light from a light source by a detecting means, and a current detected by the detecting means. Of the high frequency signal bypassed by the bypass means for converting the high frequency signal of the current detected by the detecting means into a voltage in a high band. It is composed of a second conversion means.

[0009]

According to the present invention, in the above-mentioned structure, the optical head has an optical head for photoelectrically converting the light obtained by irradiating the disk with the light from the light source. The converted current is converted into a voltage only in the low range, the high frequency signal of the current detected by the detection means is bypassed, and the current of the bypassed high frequency signal is converted into the voltage in the high band.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a disk device.
This disk device records and reproduces (or erases) data by using focused light on a disk 1 composed of an optical disk, a magneto-optical disk, or the like.

Grooves (recording tracks) are spirally formed on the surface of the disk 1, and the disk 1 is rotated at a constant speed by a motor 2. The motor 2 is controlled by a motor control circuit 18.

On the disk 1, a plurality of sectors are allocated on the basis of the reference mark. This sector is used as an address reference. Variable length information is recorded on a plurality of blocks on the disc 1, and 300,000 blocks are formed on the disc 1 in 36000 tracks.

The recording capacity of one block on the disk 1 is constant, and the number of sectors corresponding to one block decreases, for example, from the inside to the outside. At the start position of the above block,
A block header (header portion) including a block number, a track number and a sector position is recorded when the disc 1 is manufactured, for example. After this header part, it is a data part in which data is recorded.

If each block on the disk 1 does not end at the sector switching position, a block gap is provided so that each block always starts at the sector switching position.

Recording and reproducing (erasing) of information on the disc 1 are performed by an optical head 3 provided below the disc 1. The optical head 3 is fixed to a drive coil 13 that constitutes a movable portion of the linear motor 31, and the drive coil 13 is connected to a linear motor control circuit 17.

A linear motor position detector 26 is connected to the linear motor control circuit 17, and the linear motor position detector 26 detects a position by detecting an optical scale 25 provided on the optical head 3. It is designed to output a signal.

Further, a permanent magnet (not shown) is provided on the fixed portion of the linear motor 31, and the drive coil 1 is provided.
The optical head 3 is moved in the radial direction of the disc 1 by exciting the magnetic head 3 by the linear motor control circuit 17.

Although the disk 1 uses a recording film for forming pits by making holes,
It is also possible to use a recording film that utilizes phase change or a multilayer recording film.

A recording / reproducing magnetic field generating means 35 composed of an electromagnet or a permanent magnet is arranged across the disc 1 at a portion facing the optical head 3. The recording / reproducing magnetic field generating means 35 is capable of reversing the polarity of the generated magnetic field according to a signal according to writing or erasing of a pit to be recorded. The recording / reproducing magnetic field generating means 35 can also be provided on the optical head 3 side.

An objective lens 6 is held on the optical head 3 by a wire or a leaf spring (not shown). The objective lens 6 is moved by a driving coil 5 in the focusing direction (optical axis direction of the lens) and driven. The coil 4 allows movement in the tracking direction (direction orthogonal to the optical axis of the lens).

Laser light generated by a laser diode 9 as a semiconductor laser oscillator driven by the laser control circuit 14 passes through the collimator lens 11a, the half prism 11b, and the objective lens 6 to the disc 1
The light reflected from the disk 1 is directed to the half prism 11c through the objective lens 6 and the half prism 11b, and one of the beams split by the half prism 11c passes through the condenser lens 10. And is guided to a photodetector 8 as a pair of tracking position sensors. The photodetector 8 is composed of two photodiodes 8a and 8b.

On the other hand, the other light split by the half prism 11c is a condenser lens 11d and a knife edge 1.
It is led via 2 to a photodetector 7 as a pair of focus position sensors. The photodetector 7 is composed of two photodiodes 7a and 7b.

In the vicinity of the laser diode 9, a photodiode PD for monitoring is provided as a light emission amount detecting device for detecting the light emission amount of the laser diode 9. A monitor current as a detection signal from the photodiode PD is supplied to the laser control circuit 14.

The photodiode 8a of the photodetector 8,
8b is connected to the preamplifier circuit 36, and the photodiodes 7a and 7b of the photodetector 7 are connected to the preamplifier circuit 3
Connected to 7.

The preamplifier circuit 36 outputs a voltage signal corresponding to a data signal as header data or recording data for the write-once type disc 1 by the detection current from the photodiodes 8a and 8b, and at the same time, a laser light tracking point. A signal related to the above, that is, a tracking signal (track difference signal) is output.

The preamplifier circuit 37 outputs a voltage signal corresponding to the data signal as the recording data for the rewritable disc (magneto-optical disc) 1 by the detection current from the photodiodes 7a and 7b, and at the same time,
A signal related to the focus point of the light, that is, a focusing signal (focus difference signal) is output.

The tracking signal from the preamplifier circuit 36 is supplied to the tracking control circuit 16. The track difference signal output from the tracking control circuit 16 is supplied to the linear motor control circuit 17 and the drive coil 4 in the tracking direction.

The focusing signal from the preamplifier circuit 37 is supplied to the focusing control circuit 15. The output signal of the focusing control circuit 15 is supplied to the driving coil 5 in the focusing direction, and the laser light is controlled so as to always be a just focus on the disk 1.

The data signal (voltage value) from the preamplifier circuit 36 reflects the unevenness of the pits (header data or recording data) recorded on the disk (write-once optical disk) 1. This data signal is supplied to the video signal processing circuit 19, where the address data (track number, sector number, etc.) as header data and image data are reproduced.

The data signal (voltage value) from the preamplifier circuit 37 is a disk (rewritable type magneto-optical disk).
The unevenness of the pit (recording data) recorded in No. 1 is reflected. This data signal is the video signal processing circuit 1
9, and the video signal processing circuit 19 demodulates and reproduces the image data.

The laser control circuit 14 causes the laser diode 9 to generate a laser beam corresponding to the reproduction light amount in response to the switching signal from the CPU 23, and creates a recording signal in the state where the reproduction light amount of the laser beam is generated. Circuit 3
The laser diode 9 is driven in response to the recording pulse (original signal) supplied from the laser diode 4 to generate a laser beam of a recording light amount. The laser control circuit 14 controls the output light amount (reproduction light amount) of the laser diode 9 by the monitor current from the photodiode PD.

In addition, in front of the laser control circuit 14, a recording signal generating circuit 34 as a modulation circuit for modulating recording data supplied from an optical disk control device 33 as an external device through the interface circuit 32 into a recording pulse is provided. Has been.

The video signal (demodulated signal) processed by the video signal processing circuit 19 is subjected to error correction processing and the like in the interface circuit 32, and then the optical disk control device 3
3 is output.

Further, in this disk device, a focusing control circuit 15, a tracking control circuit 16,
A D / A converter 22 used for exchanging information between the linear motor control circuit 17 and the CPU 23 is provided.

Further, the tracking control circuit 16 is
The objective lens 6 is moved in accordance with the track jump signal supplied from the CPU 23 via the D / A converter 22, and the laser light is moved by one track.

The laser control circuit 14, the focusing control circuit 15, the tracking control circuit 16, the linear motor control circuit 17, the motor control circuit 18, the video signal processing circuit 19, the recording signal generating circuit 34, etc. are connected to the bus line 20.
Is controlled by the CPU 23 via the CPU, and the CPU 23 is adapted to perform a predetermined operation by a program stored in the memory 24.

The preamplifier circuit 36 outputs a voltage signal corresponding to a data signal or a header signal using currents from the photodiodes 8a and 8b, and also outputs a voltage signal as a tracking signal.
As shown in FIG. 1, the high speed amplifier 51, the low speed amplifier 52,
53, a differential amplifier 54, resistors R1, to R12, and capacitors C1 and C2.

That is, the signals from the cathodes of the photodiodes 8a and 8b are supplied to the inverting input terminal of the high speed amplifier 51, and the current flowing through the photodiodes 8a and 8b is converted into a voltage by the resistor R1. The non-inverting input terminal side of the high speed amplifier 51 is supplied with the potential determined by the resistors R3 and R4. Therefore, the inverting input terminal side has the same potential. By the way, the photodiodes 8a and 8b
The anode side is subjected to current-voltage conversion by the low speed amplifiers 52 and 53 in order to generate a tracking signal.

The power supply voltage VRE is applied to the preamplifier circuit 36.
By applying F as a bias, the voltage on the non-inverting input terminal side of the high-speed amplifier 51 can be raised to about 10V,
Bias the photodiodes 8a, 8b at 4V,
It is possible to perform processing such that the output of the high speed amplifier 51 is centered at 6V. Therefore, the voltage on the non-inverting input terminal side of the high-speed amplifier 51 can be increased, the photodiodes 8a and 8b are reverse-biased, and the signal band can be widened.

Further, the low speed amplifier 52 is connected to the anode side of the photodiode 8a through a bypass means composed of the capacitor C1 and the resistor R5, and the anode side of the photodiode 8b is connected to the capacitor C2 and the resistor R8. The low-speed amplifier 53 is connected via the configured bypass means.

For this reason, even if a high-speed signal tries to flow through the photodiodes 8a and 8b, there is no path. Therefore, only the high band is allowed to flow to the capacitors C1 and C2 by the capacitor C1, the resistor R5, and the capacitor C2 and R8. Thus, a high-speed current flows through the photodiodes 8a and 8b, and a high-speed data signal can be taken out by the cathode side of the photodiodes 8a and 8b, that is, the high-speed amplifier 51. That is, the impedance for high frequencies is lowered by the capacitors C1 and C2, and the photodiode 8
A high band signal is allowed to flow in a and 8b.

The preamplifier circuit 37 outputs the voltage signal corresponding to the magneto-optical data signal using the currents from the photodiodes 7a and 7b, and also outputs the voltage signal as the focusing signal. It has the same configuration as the circuit 36.

The video signal processing circuit 19 demodulates the data signal from the preamplifier circuit 36, the header signal, or the voltage signal corresponding to the magneto-optical data signal from the preamplifier circuit 37 into a reproduced signal, and is shown in FIG. Data, header signal processing circuit 41, binarization circuit 4
2, 45, demodulation circuit 43, magneto-optical data signal processing circuit 4
4 and a reference voltage circuit 90.

The data / header signal processing circuit 41 accurately binary-codes even when the amplitude of the data signal becomes small due to small dust or scratches adhering to the disk 1 and the level of the pit tip greatly fluctuates. For this purpose, the peak of the pit tip is detected and the input signal is fed back to make the output pit tip level uniform.

Further, the data / header signal processing circuit 41
Is for processing the header signal or the data signal supplied from the amplifier 51 in the preamplifier circuit 36,
In addition to the peak detection, band control is added to the feedback loop so that appropriate feedback can be performed according to the rotation speed and density.

That is, the data / header signal processing circuit 4
As shown in FIG. 4, 1 includes a level conversion circuit 56, a detection circuit 57, an auto bias control circuit 58, and changeover switches SW1 and SW2.

The level conversion circuit 56 includes the preamplifier circuit 3
The level conversion is performed on the header signal or the data signal supplied from the amplifier 51 in the reference numeral 6, and as shown in FIG. 4, it is composed of an amplifier 56a, resistors R21 to R24, and a diode D1.

The detection circuit 57 performs peak detection of the signal supplied from the level conversion circuit 56, and as shown in FIG. 4, the resistors R25 and R26, and the diode D.
2, D3, D4.

The auto bias control circuit 58 is
The bias of the level conversion circuit 56 is controlled according to the peak detection signal from the detection circuit 57, and as shown in FIG. 4, an amplifier 58a, resistors R27, R2, and R2.
9, capacitor C3, and band control capacitor C
It is composed of four. The changeover switch SW1 is C
The switch is switched by a header / data switching signal from the PU 23. The changeover switch SW2 is a CPU
It is a switch that can be switched by a recording / reproducing switching signal from 23.

Further, the automatic bias control circuit 5
In No. 8, there is a gap of several pits between the header part and the data part. Therefore, if the response in the header part is not performed as quickly as possible, it will affect the next data part. The detection and the peak detection time of the header section are switched by the changeover switch SW1 to improve the response to the header section.

Further, the automatic bias control circuit 5
By applying bias from + 12V and GND, it is not necessary to make the bias voltage VBias, and the power is directly turned on without considering the movement of VBias with respect to power supply fluctuations. Can move according to the power supply, and the circuit can be simplified.

By the way, since a signal called a sector mark is present at the beginning of the header section and has a larger amplitude than the header section, the data section changes the time constant for peak detection to charge and discharge in response to this. , The header section is switched to make the charging / discharging time the same, and the diodes D3 and D4 for the rectifying action for this purpose are connected in series to form a potential difference (0.7V). It responds well to the sector mark at the beginning of the copy.

Similarly, for magneto-optical (MO) signals, signal processing is performed using a magneto-optical data signal processing circuit 44 as shown in FIG. At this time, the header section is processed by another system (data, header signal processing circuit 41), but the influence of the header section appears on the magneto-optical signal (ideally, this does not occur at all, but a head mounting error). A header signal appears in the operation detection signal due to the above, etc. Since the header signal has a large S / N, a small error becomes a level that cannot be ignored as compared with the magneto-optical signal.).

For this reason, in order to prevent the binarization of the head portion when a magneto-optical signal comes in, it is difficult to binarize the header portion, and the bias is switched to a negligible level so as to have a fixed bias.

The magneto-optical data signal processing circuit 44 processes the magneto-optical data signal supplied from the amplifier 51 in the preamplifier circuit 37. By applying band control to the feedback loop in addition to the peak detection, the rotation is performed. According to the number and density, appropriate feedback can be given.

That is, the magneto-optical data signal processing circuit 41
As shown in FIG. 5, is composed of an addition circuit 61, a level conversion circuit 62, a detection circuit 63, an auto bias control circuit 64, and a changeover switch SW3.

The adder circuit 61 adds the header signal supplied from the amplifier 51 in the preamplifier circuit 36 and the magneto-optical signal supplied from the amplifier 51 in the pre-amplifier circuit 37, and the adder circuit 61 converts the magneto-optical signal into the header part. It outputs a magneto-optical data signal excluding the influence, and as shown in FIG. 5, the resistors R41 to R44 and the differential amplifier 61 are provided.
It is composed of a.

The level conversion circuit 62 performs level conversion on the magneto-optical data signal supplied from the differential amplifier 61a in the adder circuit 61, and as shown in FIG.
It is composed of an amplifier 62a, resistors R45 to R48, and a diode D8.

The detection circuit 63 performs peak detection of the signal supplied from the level conversion circuit 62, and as shown in FIG. 5, the resistors R49, R50 and the diode D.
It is composed of 9.

The auto bias control circuit 64 is
The bias of the level conversion circuit 62 is controlled in accordance with the peak detection signal from the detection circuit 63, and as shown in FIG. 5, an amplifier 64a, resistors R51, R5, and R5.
3, capacitor C6, and capacitor C for band control
It is composed of 7. The changeover switch SW3 is C
The switch is switched by a header / data switching signal from the PU 23.

Further, the automatic bias control circuit 6
By applying bias from + 12V and GND, it is not necessary to make bias voltage VBias in 4 and it is possible to directly turn on the power without considering the movement of VBias with respect to power supply fluctuations. Can move according to the power supply, and the circuit can be simplified.

The binarization circuit 42 binarizes the data, the data signal supplied from the header signal processing circuit 41, or the header signal. As shown in FIG. 6, the comparator 42a, the resistor R31, R32, diode D5, D
6, D7 and the capacitor C5.

That is, the binarization circuit 42 binarizes the signal rectified by the diodes D5, D6 and D7. In the bright portion of the data signal, the return light noise of the laser light and the noise of the disk 1 are likely to be affected. Therefore, for rectification in the bright direction, the potential difference is increased by using the two diodes D6 and D7 to reduce the noise. To widen the margin.

Further, feedback (positive feedback) is applied by the capacitor C5 so that the rectified signal (contrast of binarization) changes in the opposite direction to the changing direction of the data signal for a short period immediately after binarization. The margin for valuation spreads,
Data cracking can be prevented. The binarization circuit 43 binarizes the data signal supplied from the magneto-optical data signal processing circuit 44, and has the same configuration as the binarization circuit 42. The demodulation circuit 43 includes binarization circuits 42 and 43.
The demodulated signal obtained by demodulating the binarized signal supplied from the device is output as a reproduced signal.

The reference voltage circuit 90 generates a reference voltage VR used in each circuit in the video signal processing circuit 19. As shown in FIG. 7, the amplifier 90a and the resistor R are used.
61 to R66.

That is, the resistance R once has a resistance value sufficiently smaller than the resistance value of the voltage dividing circuit composed of the resistances R63 and R64.
It is possible to use the amplifier 90a with a small output current by generating the VR voltage with the voltage dividing circuit composed of 65 and R66 and supplying only the changed amount from the amplifier 90a. Can generate a sufficient reference voltage VR.

[0068]

As described above in detail, according to the present invention,
When the tracking signal or focusing signal is taken from the anode side of the photodiode, the current flowing through the photodiode is restricted by the frequency characteristics of the preamplifier circuit, and the data signal taken out from the cathode is affected by the signal taken out from the anode. It is possible to provide a disk device that does not have any problems.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of an operational amplifier circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a disk device according to an embodiment of the present invention.

FIG. 3 is a block diagram showing a circuit configuration of the video signal processing circuit of FIG.

FIG. 4 is a diagram showing a circuit configuration of a data / header signal processing circuit of FIG. 2;

5 is a diagram showing a circuit configuration of the magneto-optical data signal processing circuit of FIG.

6 is a diagram showing a circuit configuration of the binarization circuit of FIG.

FIG. 7 is a diagram showing a circuit configuration of the reference voltage circuit of FIG.

[Explanation of symbols]

1 ... Disk, 3 ... Optical head, 6 ... Objective lens, 7,
8 ... Photodetector (detection means), 7a, 7b, 8a, 8b ...
Photodiode, 9 ... Laser diode, PD ... Photodiode, 13 ... Drive coil, 14 ... Laser control circuit, 17 ... Linear motor control circuit, 19 ... Video signal processing circuit, 23 ... CPU, 31 ... Linear motor, 32 ... Interface Circuit, 33 ... Optical disc controller, 34
... recording signal generating circuit, 35 ... recording / reproducing magnetic field generating means,
36, 37 ... Preamplifier circuit, 41 ... Data, header signal processing circuit, 42, 45 ... Binarization circuit, 43 ... Demodulation circuit, 44 ... Magneto-optical data signal processing circuit, 51 ... High speed amplifier, 52, 53 ... Low speed amplifier , 54 ... Differential amplifier, R
1, ~ R12, R21, ~ R29, R31, ~ R32,
R41, ~ R54, R61, ~ R66 ... Resistance, C1, ~
C7 ... Capacitor, D1, ... D9 ... Diode, 56,
62 ... Level conversion circuit, 42a, 56a, 58a, 61
a, 62a, 64a, 90a ... Amplifier, 57, 63 ... Detection circuit, 58, 64 ... Auto bias control circuit, 61 ... Addition circuit, SW1, SW2, SW3 ... Changeover switch, C1, ... C7 ... Capacitor, 90 ... Reference Voltage circuit.

Claims (2)

[Claims] 1. An optical head which detects light obtained by irradiating a disk with light from a light source by means of a detection means and photoelectrically converts it, and a current which converts the current detected by said detection means into a voltage only in a low range. 1 conversion means, bypass means for bypassing the high frequency signal of the current detected by the detection means, and second conversion means for converting the current of the high frequency signal bypassed by this bypass means into a voltage in a high band. A disk device characterized by being provided. 2. The detection means comprises a diode,
The first side of the diode is connected to the anode side of the diode via bypass means.
2. The disk device according to claim 1, wherein the converting means is connected, and the second converting means is connected to the cathode side of the diode.