JPH0536092A - Position detecting circuit for objective lens - Google Patents

Abstract

PURPOSE:To obtain an exact detected signal even in the case of using a phototransistor for the position detecting circuit of an objective lens. CONSTITUTION:The detected signals are generated by two detectors 70 and 71, corresponding to the moving position of an objective lens 6, and a difference signal of those signals is outputted as the moving position signal of the above mentioned objective lens 6. At that time, the noise of phototransistors 70b and 71b constituting the above mentioned detectors 70 and 71, which is included in the difference signal, is removed by the band restriction of a filter 85.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens position detecting circuit for detecting the moving position of an objective lens in an optical head used in a disk device, for example.

[0002]

2. Description of the Related Art As is well known, a disc device capable of recording data on a disc and reading (reproducing) data recorded on the disc has been developed. Recording of data in this disk device is performed by outputting a laser beam from, for example, a semiconductor laser oscillator in the optical head, and reproduction of data is performed by using a detector in the optical head to convert the reflected light from the disk into an electrical signal. Is converted into a video signal and then converted into a video signal.

A disk drive of this type has a coarse access mode in which a linear motor for moving the entire optical head is used for rough access, and a fine access mode in which an objective lens in the optical head is moved for fine access. And have.

When the entire optical head is moved in the rough access mode, the objective lens in the optical head vibrates. Therefore, in order to prevent (suppress) this vibration, a method of detecting the moving position of the objective lens and holding it at a predetermined position using this detection signal is used.

As a detection circuit for detecting the moving position of the objective lens, a phototransistor (light receiving element) receives the amount of light reflected or shielded from the light source (light emitting element) with respect to the moving body that moves together with the objective lens, and the amount of movement thereof. The detection signal corresponding to the (movement distance) was output.

However, in the case where the phototransistor is used for the detection circuit, there is a drawback in that the noise which the phototransistor itself has affects the detection signal, so that an accurate detection signal cannot be obtained.

[0007]

As described above, conventionally, when a phototransistor is used in the detection circuit for detecting the moving position of the objective lens, noise of the phototransistor itself affects the detection signal. There is a drawback in that an accurate detection signal cannot be obtained.

Therefore, an object of the present invention is to provide a position detection circuit for an objective lens which can obtain an accurate detection signal even when a phototransistor is used and which enables stable control.

[0009]

In order to achieve the above object, in the position detecting circuit for an objective lens according to the present invention, an optical system having an objective lens for converging a light beam on a storage medium having a track is provided. A head, a moving means for moving the objective lens of the optical head in a direction orthogonal to the axis of the light beam, and a light emitting element and a light receiving element for generating a detection signal corresponding to the moving position of the objective lens by the moving means. A first detecting means composed of an element and a light emitting element and a light receiving element which are provided at positions different from the first detecting means and which generate a detection signal corresponding to the moving position of the objective lens. A second detection unit, a removal unit that removes noise of each light receiving element of the first and second detection units, a detection signal of the first detection unit, and a detection signal of the second detection unit. The difference signal is the objective Of the light emitting elements of the first and second detecting means, based on the sum signal of the output means for outputting the moving position signal of the lens and the detection signal of the first detecting means and the detection signal of the second detecting means. It is composed of adjusting means for adjusting the amount of light emission.

[0010]

According to the present invention, since the noise of the light receiving element can be removed by the above means, a stable output can be obtained.

[0011]

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 according to the present invention.

This disk device records / reproduces (or erases) data on / from a disk 1 composed of an optical disk or a magneto-optical disk by using focused light.

A spiral groove (recording track) is formed on the surface of the disk 1. The disk 1 is rotated by a motor 2 at a constant speed, for example. The motor 2 is controlled by a motor control circuit 18.

The disk 1 is divided into a plurality of sectors on the basis of the reference mark. Variable-length information (data) is recorded on a plurality of blocks on the disc 1, and 3 pieces are recorded on the disc 1.
300,000 blocks are formed on 6000 tracks. In this case, the sector and track are used to indicate the address of the block.

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 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, there is a data part in which data is recorded.

When 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 / reproducing (erasing) of data on the disk 1 is performed by an optical head 3 provided below the disk 1. This optical head 3
The linear motor 31 is fixed to a drive coil 13 that constitutes a movable portion. The drive coil 13 is connected to the linear motor control circuit 17.

A linear motor position detector 26 is connected to the linear motor control circuit 17. The linear motor position detector 26 outputs a position signal by detecting the optical scale 25 provided on the optical head 3.

Further, a permanent magnet (not shown) is provided on the fixed portion of the linear motor 31, and the drive coil 13 is provided.
Is excited by the linear motor control circuit 17, the optical head 3 is moved in the radial direction of the disk 1.

The disc 1 uses a recording film for forming pits by making holes.
It is also possible to use a recording film or a multi-layer recording film that utilizes phase change.

A recording / reproducing magnetic field generating means 35 composed of an electromagnet or a permanent magnet is provided at a portion facing the optical head 3 so as to sandwich the disk 1. The recording / reproducing magnetic field generating means 35 is capable of reversing the polarity of the generated magnetic field according to a signal corresponding 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.

The optical head 3 includes an objective lens 6, drive coils 4 and 5 for driving the objective lens 6, a photodetector 7 as a focus position sensor, a photodetector 8 as a tracking position sensor, and a semiconductor laser oscillator. Laser diode 9, a condenser lens 10, a collimator lens 11a for collimating the laser light from the laser diode 9, half prisms 11b and 11c, and a condenser lens 1.
1d, the knife edge 12, and a photodiode PD for monitoring as a light emission amount detection device for detecting the light emission amount of the laser diode 9 and the like.

As shown in FIG. 3, for example, the objective lens 6 includes a wire suspension 5 from a fixed portion (not shown).
Sunpended by 1,51. This objective lens 6
Are moved by the drive coil 5 along the focusing direction, in other words, along the optical axis direction of the objective lens 6. Further, the objective lens 6 is moved by the drive coil 4 along the tracking direction, in other words, the direction orthogonal to the optical axis of the objective lens 6.

That is, the objective lens 6 is moved in the direction of arrow C shown in the drawing, which is orthogonal to the optical axis thereof, by the interaction between the drive coils 4 and 4 and the permanent magnets 52 and 52 arranged in the fixed portion.

On the side of the objective lens 6, there is provided a reflecting plate 6a composed of a mirror or the like that moves together with the objective lens 6 in the direction of arrow C in the figure. This reflector 6
Two detectors 70 and 71 fixed to the main body of the optical head 3 are provided side by side in the direction of arrow a in the direction of arrow C in the figure. As shown in FIG. 1, these detectors 70 and 71 respectively include LEDs (light emitting diodes) 70a and 71a as light emitting elements and phototransistors 70b and 71b as light receiving elements.

These detectors 70 and 71 are provided with the light shield plate 6a.
The electric signal corresponding to the position of is output to the lens sensor processing circuit 72 as a position detection circuit. Detector 7
From 0 and 71, when the objective lens 6 corresponds to the center position, a detection signal whose difference signal is "0" is output.
As a result, the difference signal between the detection signals from the detectors 70 and 71 becomes an electric signal of a level corresponding to the moving position of the objective lens 6. FIG. 4 shows the detection characteristics of the detectors 70 and 71.

Here, the detection outputs of the detectors 70 and 71 with respect to the position of the objective lens 6 are shown. When the objective lens 6 is located at the neutral position near the center position in the movable range, the detection outputs of the detectors 70 and 71 are at the same level, and the difference signal between them is "0" as shown in FIG. It is like this.

The lens sensor processing circuit 72 includes a detector 7
The difference signal of the detection signals from 0 and 71 is obtained (see FIG. 6),
This difference signal is output as an electric signal of a level corresponding to the moving position of the objective lens 6, that is, a position signal.

Further, the lens sensor processing circuit 72 obtains a sum signal of the detection signals from the detectors 70 and 71, and adjusts the light emission amount of the LEDs 70a and 71a in the detectors 70 and 71 by the sum signal. ing.

That is, the lens sensor processing circuit 72 is
As shown in FIG. 1, the buffers 81 and 82, the subtraction circuit 8
3, level adjusting circuit 84, filter 85, buffer 8
6 and a light emission amount adjusting circuit 87.

The buffers 81 and 82 are connected to the detectors 70 and 7 respectively.
It converts a current as a detection signal supplied from 1 into a voltage, and is configured by amplifiers 81a and 82a and resistors R71 and R72, respectively.

As shown in FIG. 6, the subtraction circuit 83 subtracts the detection signal of the detector 71 from the detection signal of the detector 70 supplied from the buffers 81 and 82.
, The differential amplifier 83a and the resistors R73 to R76
It is composed by.

The level adjusting circuit 84 adjusts the signal level of the difference signal as the subtraction result supplied from the subtracting circuit 83, and as shown in FIG. 1, the amplifier 84a, the resistor R77, and the variable resistor VR1. , VR2. The level adjusting circuit 84 can adjust the bias voltage for the difference signal of the detection signal by the variable resistor VR1 and can change the amplification factor by the amplifier 84a by the variable resistor VR2.

The filter 85 is a low-pass filter as removing means for passing (band limiting) only a signal in a predetermined frequency band of the difference signal supplied from the level adjusting circuit 84, and as shown in FIG. It is composed of an amplifier 85a, resistors R78 to R80, and capacitors C11 and C12. Due to the band limitation by the filter 85, noise generated from the phototransistors 70b and 71b can be removed.

The buffer 86 temporarily holds the difference signal supplied from the filter 85, and is composed of an amplifier 86a, resistors R81 to R83, and a capacitor C13, as shown in FIG.

As shown in FIG. 5, the light emission amount adjusting circuit 87 includes detectors 70 and 7 supplied from buffers 81 and 82.
The sum signal of the detection signals of No. 1 is obtained, and the current amount of the LEDs 70a and 71a in the detectors 70 and 71 is controlled by the sum signal to adjust the light emission amount of the LEDs 70a and 71a. Accordingly, even if the light amount of the LEDs 70a and 71a fluctuates due to dust or temperature, the LEDs 70a and 71a can be accurately and automatically adjusted, and the detection outputs of the detectors 70 and 71 can be kept constant.

As shown in FIG. 1, the light emission amount adjusting circuit 87 is composed of an amplifier 87a, transistors 87b and 87c, resistors R84 to R89, a variable resistor VR3, a constant voltage diode D10, and a capacitor C14. The light emission amount adjusting circuit 87 can adjust the bias voltage with respect to the sum signal of the detection signals by the variable resistor VR3.

Here, by changing the amplification factor of the level adjusting circuit 84 and the bias of the detection signal of the light emission amount adjusting circuit 87 with respect to the sum signal, even if the light emitting amounts of the LEDs 70a and 71a vary widely, they are used as volumes. It can be adjusted by the variable resistors VR1 and VR3.

Further, by changing the bias for the difference signal of the detection signal of the level adjusting circuit 84, the offset for the mounting error of the optical head 3 can also be adjusted by the variable resistor VR1 as a volume. Next, the operation of the above configuration will be described.

That is, the currents as detection signals flowing through the phototransistors 70b and 71b of the detectors 70 and 71 are converted into voltages by the buffers 81 and 82, respectively, and output to the subtraction circuit 83 and the light emission amount adjustment circuit 87.

In the subtraction circuit 83, the difference signal between the detection signals (voltage values) of the detectors 70 and 71 is obtained by subtracting the voltage value from the buffer 81 from the voltage value from the buffer 81, and output to the level adjustment circuit 84. To be done.

In the level adjusting circuit 84, the level of the difference signal supplied from the subtracting circuit 83 is the above-mentioned LEDs 70a, 71.
After the level is adjusted to the light amount of a, the filter 8
5 is output.

The filter 85 removes noise generated in the phototransistors 70b and 71b from the difference signal supplied from the level adjusting circuit 84 by band limitation. Then, by transmitting this to the buffer 86, the position signal is output from the lens sensor processing circuit 72 to the CPU 23 via the bus line 20.

Further, the light emission amount adjusting circuit 87 generates a sum signal in which the voltage value from the buffer 81 and the voltage value from the buffer 82 are added, whereby the LEDs 70a and 71a are generated.
Is controlled.

The laser light generated by the laser diode 9 is collimator lens 11a and half prism 1.
1b, the disk 1 is irradiated via the objective lens 6. The reflected light from the disc 1 is guided to the half prism 11c via the objective lens 6 and the half prism 11b. Then, one of the light beams split by the half prism 11c is guided through a condenser lens 10 to a photodetector 8 including 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 the photodetector 7 composed of two photodiodes 7a, 7b. The detection signal from the photodiode PD is the laser control circuit 1 described later.
4 is output.

The photodiodes 8a and 8b of the photodetector 8 are connected to the preamplifier circuit 36, and the photodiodes 7a and 7b of the photodetector 7 are connected to the preamplifier circuit 37.

The preamplifier circuit 36 outputs a voltage signal corresponding to a data signal as header data or recording data for the write-once type disk 1 by the detection current from the photodiodes 8a and 8b, and a signal relating to a tracking point of laser light. That is, the 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 the focus of the laser beam. A signal related to a point, 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 that the laser beam is always just focused on the disc 1.

The data signal (voltage value) from the preamplifier circuit 36 reflects the unevenness of the pits (header data and recording data) recorded on the disk (write-once optical disk) 1. That is, this data signal is supplied to the video signal processing circuit 19, and in this video signal processing circuit 19, 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 reflects the unevenness of the pits (recording data) recorded on the disk (rewritable magneto-optical disk) 1. That is, this data signal is supplied to the video signal processing circuit 19, and the video signal processing circuit 1
In 9, the image data is demodulated and reproduced.

The laser control circuit 14 causes the laser diode 9 to generate a laser beam corresponding to the reproduction light amount in accordance with the switching signal from the CPU 23, and a recording signal in the state where the reproduction light amount of the laser beam is generated. The laser diode 9 is driven according to the recording pulse (original signal) supplied from the creating circuit 34 to generate the laser light of the recording light amount. This laser control circuit 14
The output light amount (reproduction light amount) of the laser diode 9 is controlled by the monitor current from the photodiode PD.

In the preceding stage of the laser control circuit 14, a recording signal generation circuit as a modulation circuit for modulating recording data supplied from the magneto-optical disk control device 33 as an external device via the interface circuit 32 into a recording pulse. 34 are provided.

The video signal (demodulated signal) processed by the video signal processing circuit 19 is output to the magneto-optical disk controller 33 after being subjected to error correction processing in the interface circuit 32.

Further, the disk drive includes focusing control circuit 15 and tracking control circuit 1, respectively.
6. 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
By moving the objective lens 6 according to the track jump signal supplied from the CPU 23 via the D / A converter 22, the laser beam can be 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 2.
It is controlled by the CPU 23 via 0, and the CPU 23 is adapted to perform a predetermined operation by a program stored in the memory 24.

The CPU 23 determines the moving position of the objective lens 6 in the optical head 3 in the C direction based on the position signal from the lens sensor processing circuit 72.

Next, the determination of the moving position of the objective lens 6 in the above-described structure when the optical head 3 is moved by the linear motor 31 by the rough access will be described.

For example, when the objective lens 6 is now displaced from the center position, a difference occurs between the detection signal of the phototransistor 70b and the detection signal of the phototransistor 71b, and a position signal corresponding to the difference is generated by the lens sensor processing circuit 72. Output to the CPU 23. Then, by the CPU 23,
The moving position of the objective lens 6 is determined from the supplied position signal, and the tracking control circuit 16 is controlled according to the determination result. As a result, the drive coil 4 is driven and moved so as to return the objective lens 6 to the center (neutral) position. As described above, the noise of the phototransistor used in the detector can be removed.

That is, the noise generated by the phototransistor is removed by band limiting using a low-pass filter. As a result, the accuracy of the detection signal of the detector can be improved, and a stable output can be obtained. Therefore, the drive control of the objective lens in the optical head can be stabilized, and the performance of the disk device can be improved. In addition, this invention is
Of course, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention.

[0064]

As described above in detail, according to the present invention, it is possible to provide an objective lens position detection circuit which can obtain an accurate detection signal even when a phototransistor is used, and which enables stable control. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a lens sensor processing circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of the disk device, similarly.

FIG. 3 is a plan view showing the configuration of the main part of the optical head in the same manner.

FIG. 4 is a diagram showing the relationship between the position of the objective lens and the detection output of each detector.

FIG. 5 is a diagram similarly showing a relationship between the position of the objective lens and the sum signal.

FIG. 6 is a diagram showing the relationship between the position of the objective lens and the difference signal.

[Explanation of symbols]

1 ... Disk, 3 ... Optical head, 4 ... Drive coil (moving means), 6 ... Objective lens, 6a ... Reflector, 7, 8 ... Photodetector, 9 ... Laser diode, 14 ... Laser control circuit,
15 ... Focusing control circuit, 16 ... Tracking control circuit, 17 ... Linear motor control circuit, 19 ... Video signal processing circuit, 23 ... CPU, 31 ... Linear motor, 3
6, 37 ... Preamplifier circuit, 70, 71 ... Detector (first and second detecting means), 70a, 71a ... LED (light emitting element), 70b, 71b ... Photodiode (light receiving element), 72 ... Laser sensor processing Circuit (output means), 8
1, 82, 86 ... Buffer, 83 ... Subtraction circuit, 84 ... Level adjusting circuit, 85 ... Filter (removing means), 85a ...
Amplifier, 87 ... Emission amount adjusting circuit (adjusting means).

Claims (1)

Claim: What is claimed is: 1. An optical head having an objective lens for condensing a light beam on a storage medium having a track, and moving the objective lens of the optical head in a direction orthogonal to the axis of the light beam. And a first detecting means including a light emitting element and a light receiving element for generating a detection signal corresponding to the moving position of the objective lens by the moving means, and the first detecting means. A second detection unit that is provided at a position and that generates a detection signal corresponding to the moving position of the objective lens, the second detection unit including a light emitting element and a light receiving element; and each of the light receiving elements of the first and second detection units. A removing unit that removes noise; an output unit that outputs a difference signal between the detection signal of the first detection unit and the detection signal of the second detection unit as a moving position signal of the objective lens; Of detection means The objective lens is provided with an adjusting means for adjusting the light emission amount of each of the light emitting elements of the first and second detecting means according to a sum signal of an intelligent signal and a detecting signal of the second detecting means. Position detection circuit.