JPH03147522A - Optical signal detector - Google Patents

Abstract

PURPOSE:To set the signal area of a reproducing signal widely by taking out the same current as that supplied from the emitter of the first transistor of a first current circuit comprised of first and second transistors to plural photoelectric conversion means from the emitter of the second transistor of the first current circuit to the second current circuit. CONSTITUTION:The device is equipped with the first current circuit 100 comprised of the first and second transistors and in which the collectors of the first and second transistors are connected to a power source and the base of the first transistor, the emitter of the first transistor, and the base of the second transistor are connected with each other. Also, it is equipped with the plural photoelectric conversion means 48 whose cathodes are connected to the emitter of the first transistor of the first current circuit 100, and the second current circuit which takes out the same current as that supplied to the photoelectric conversion means 48 from the emitter of the second transistor of the first current circuit 100. In such a way, it is possible to set the range of an output signal when recording information is reproduced widely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical signal detection device such as a disc device that records or reproduces information on an optical disc.

(Conventional technology) At present, as the informationization of society is rapidly progressing, including office automation, optical disk devices are attracting attention as large-capacity storage devices that can store large amounts of data such as code information, documents, and images. There is.

This is because optical disk devices record and reproduce data using focused laser light.

It has a recording density that is more than an order of magnitude higher than that of magnetic disks,
In addition, high reliability is maintained because recording and reproduction can be performed mechanically and without contact.

As is well known, this optical disc device is provided with an optical head that writes (records) or reads (reproduces) information by irradiating light (beam) onto the optical disc.

Light from the optical head is irradiated through an objective lens, following grooves (tracks or information pit rows) formed on the optical disk. That is, when recording or reproducing information.

The objective lens is subjected to tracking and focusing control with respect to the optical disc so that light is always irradiated onto the tracks of the optical disc. In this case, the light reflected by the optical disk is received by a photodetecting element consisting of a four-part sensor via an objective lens or the like. Then, the drive coil of the objective lens is controlled by a drive signal corresponding to the tracking control signal and focusing control signal generated by this photodetector. By controlling this drive coil, the objective lens is always maintained on a desired track, and information is accurately recorded or reproduced on the optical disc.

By the way, various methods have been invented in the past as signal detection methods for optical disk devices having the above-mentioned configuration. There are two methods for detecting the information reproduction signal, for example:
As disclosed in Japanese Unexamined Patent Publication No. 63-211131, the cathode side output ends of photodiodes and the output end of a DC power supply, which are commonly connected to each other, are input to an operational amplifier.

There is a method of obtaining a reproduction signal of information recorded on an optical disk from the output derived from the output end of this operational amplifier.

(Problem to be Solved by the Invention) However, when detecting a reproduced signal of information using the detection method disclosed in Japanese Patent Application Laid-Open No. 63-211131, a DC power source is connected to one end of the input terminal of the operational amplifier. Because of the connection, the following problems occurred. That is, when the cathode side outputs of the photodiodes commonly connected to each other have a high potential in proportion to the DC current output, the operational amplifier outputs a signal from the output terminal. For this reason, at the output end of the three operational amplifiers, only an output at a voltage higher than the potential of the DC power supply that is input to one input end of the operational amplifier is obtained.

There was a drawback that the signal area of the reproduced signal was narrow.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical signal detection device that can set a wide signal area for a reproduced signal when detecting a reproduced signal of information.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, an optical signal detection device of the present invention is composed of first and second transistors, The collector is connected to the power supply and the first
a first current circuit in which the base of the transistor, the emitter of the first transistor, and the base of the second transistor are connected; and a plurality of current circuits each having a cathode connected to the emitter of the first transistor of the first current circuit. photoelectric conversion means;
A second current circuit that extracts a current equivalent to the current supplied to the photoelectric conversion means from the emitter of the second transistor of the first current circuit.
It is characterized by being equipped with a current circuit.

(Function) The present invention provides a current that is equivalent to the current supplied from the emitter of the first transistor of the first current circuit constituted by the first and second transistors to the plurality of charging conversion means.
The second current circuit takes out the current from the emitter of the second transistor of the first current circuit.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a diagram showing a disk device to which the optical signal detection device according to the present invention is applied. Optical disc (recording medium) 1
A spiral or concentric groove (track) is formed on the surface of the optical disk 10, and the optical disk 10 is rotated by a motor 12 at, for example, a constant speed. This motor 12 is controlled by a motor control circuit 14.

As shown in FIG. 3, the optical disc 10 has a donut-shaped metal coating layer, ie, a recording film made of tellurium or bismuth, coated on the surface of a circular substrate made of glass or plastic, for example.
A notch, that is, a reference position mark 15, is provided near the center of the metal coating layer.

Furthermore, as shown in FIG.
Divided into sectors. On the optical disc 10, variable length information is recorded over a plurality of blocks, and 300,000 blocks are formed on 36,000 tracks on the optical disc 10.

The number of sectors in one block on the optical disc 10 is, for example, 40 sectors on the inner side and 20 sectors on the outer side.
It is supposed to be a sector. A block header A consisting of a track number, a sector number, etc. is recorded at the start position of the block, for example, when the optical disc 10 is manufactured.

Furthermore, if each block on the optical disc 10 does not end at the sector switching position, a block gap is provided so that each block always starts from the sector switching position.

Recording and reproduction of information on the optical disc 10 is performed by an optical head 16, as shown in FIG. This optical head 16 is fixed to a drive coil 18 that constitutes a movable part of a linear motor.
is connected to the linear motor control circuit 20.

As shown in FIG. 4, the optical head 16 has an objective lens 26 supported by a wire or a leaf spring (elastic member) 28. This objective lens 26 is moved in the focusing direction (lens optical axis direction) by a drive coil (lens actuator coil) 30, and in the tracking direction (lens optical axis direction) by a drive i-coil (lens actuator coil) 32 as a moving means. It is adapted to be moved in one direction (arrow BB shown in the figure) perpendicular to the optical axis. The optical head 16 is also provided with an objective lens position sensor 33. This objective lens position sensor 33 moves the objective lens 26 in the tracking direction BB.
- Based on the vicinity of the center position of the objective lens 26 when a pair of wires or leaf springs 28 supported by the terminals are balanced in a natural state.

The position of the objective lens 26 in the tracking direction BB= is detected.

A linear motor position detector 22 is connected to the linear motor control circuit 20 . This linear motor position detector 22 is adapted to output a current position signal by detecting an optical scale 24 provided on the optical head 16.

Further, a permanent magnet (not shown) is provided in the fixed part of the linear motor, and when the drive coil 18 is excited by the linear motor control circuit 20, the optical head 16 is moved in the radial direction of the optical disk 10 ( coarse access).

Furthermore, the position deviation signal 33a of the objective lens position sensor 33 described above is input to the linear motor control circuit 20. The linear motor control circuit 20 detects the position of the objective lens 26 from this position deviation signal 33a, and drives the drive coil 18 that constitutes the movable part of the linear motor in accordance with the operation of the objective lens 26.

Further, the semiconductor laser light source 3 is controlled by the laser control circuit 34.
The laser beam 38 generated from the collimator lens 4
0, the light is irradiated onto the optical disk 10 via the half prism 42 and the objective lens 26.

The laser beam 38 is reflected on this optical disk 10, and the reflected light from this optical disk 10 is guided to a photodetector 48 via an objective lens 26, a half prism 42, a condensing lens 44, and a cylindrical lens 46. . This photodetector 48 has four divided photodetection cells 48a and 48bq.
48c and 48d.

The output signal of the photodetection cell 48a of the photodetector 48 is supplied via an amplifier 50 to one end of an adder 52.54. The output signal of the photodetection cell 48b is supplied via an amplifier 56 to one end of an adder 58.60. The output signal of the photodetection cell 48c is sent to the adder 5 via the amplifier 62.
4.58 is supplied to the other end. The output signal of the photodetection cell 48d is supplied via an amplifier 64 to the other end of the adder 52.60.

The output signal of the adder 52 is supplied to an inverting input terminal of a differential amplifier 66, and the output signal of the adder 58 is supplied to a non-inverting input terminal of the differential amplifier 66. This results in
The differential amplifier 66 supplies a track difference signal 68 to the tracking control circuit 70 in accordance with the difference between the adders 52 and 58. This tracking control circuit 70
is the track difference signal 68 provided from the differential amplifier 66.
The track drive signal 72 is formed in accordance with the above. This track drive signal 72 is supplied to a drive device 31 and a drive coil 32 that move the objective lens 26 in the tracking direction, and by moving the objective lens 26 according to the number of tracks to be jumped, the laser beam 38 is transferred to the optical disc. It is designed to be moved on 10.

Further, the output signal of the adder 54 is supplied to an inverting input terminal of a differential amplifier 74, and the output signal of the adder 60 is supplied to a non-inverting input terminal of the differential amplifier 74. Thereby, the differential amplifier 74 supplies a signal regarding the focus point to the focusing control circuit 76 in accordance with the difference between the adders 54 and 60. The output signal 78 of the focusing control circuit 76 is supplied to the drive device 29 and the drive coil 30, and is controlled so that the laser beam 38 is always in just focus on the optical disk 10.

Furthermore, in the state where the above-mentioned focusing control and tracking control are performed, the photodetecting cells 48a to 48d
is supplied with a signal from an information signal detection circuit 79. The signals supplied to the photodetection cells 48a-48d depend on the amount of light irradiated to the photodetection cells 48a-48d, and reflect the unevenness of pits (recorded information) formed on the tracks. At this time, the photodetection cells 48a-48
dl:: A signal equivalent to the supplied signal is supplied from the information detection circuit 79 to the video circuit 80. This video circuit 80
reproduces image information, address information (track number, sector number, etc.) based on the supplied signal.

The laser control circuit 34 and the focusing control circuit 76
, tracking control circuit 70, linear motor control circuit 2
0, the motor control circuit 14, the video circuit 80, etc. are controlled by the CPU 84 via the pass line 82. This CPU 84 is designed to perform predetermined operations according to a program stored in a memory 86.

Further, the D/A converter 88 is connected to the focusing control circuit 76.
, is used for exchanging information between the linear motor control circuit 20 and the CPU 84.

Hereinafter, the configuration and operation of the information signal detection device of the present invention will be explained with reference to FIG.

FIG. 1 shows a photodetector 48, a current mirror circuit 100, a first
The power source 102 is composed of a power source 102, a second power source 104, and the like. The photodetection cells 48a to 48d of the photodetector 48 are connected at their cathodes, and are connected to an output end 106 that is output from a first power source 102 via a current mirror circuit 100. Moreover, the anode side of the photodetection cells 48a to 48d is
It is connected to amplifiers 50, 56, 62 and 64 as shown in FIG. As described above, the current mirror circuit 100 to which the current output from the first power supply 102 is input is composed of transistors 108 and 110, etc., and the same current 1 is output to the outputs @106 and 112. Ru. One output end 106 is connected to the above-mentioned photodetection cell 48a.
It is branched into two directions, the cathode side of -48d and the transistor 114, and is connected to each other. At this time, there is a current on the cathode side! 0. Current I2 is on the transistor 114 side.
is supplied. The other output end 112 is
2 between the inverting input terminal of the arithmetic unit 116 and the transistor 118
They are branched in different directions and connected to each other. Further, the second power supply 104 is supplied to the transistor 120 and the base sides of the transistors 114, 118 and 120 via the resistor R. Furthermore, transistor 114.11g
and 120 are connected together and grounded.

Also, the current input to the transistor 118! 3rd and 2nd
The current 4 supplied from the power supply 104 is configured to be the same as the current I2 input to the transistor 114. At this time, the current mirror circuit 1 is
It becomes possible to change the operating point of 00. By changing the operating point of the transistor 108 and the like, it is possible to operate at an operating point where it is easy to operate.

By the way, the current I5 input from the output terminal 112 to the inverting input terminal of the arithmetic unit 116 is transmitted to the photodetection cells 48a-48.
It is equivalent to the current IO supplied to the cathode side of d. This is clear from the fact that the current ■2 and the current I3 are the same current. Furthermore, the fact that the sum signal of the currents that can pass when the photodetection cells 48a to 48d are irradiated with light, that is, the current IO, and the current 5 are equivalent, means that this current 5 is The signal is equivalent to an optical signal (information signal) reflecting the pit information (recorded information) formed on the track on the disk 10. Further, since the current generator 5 is directly output from the current mirror circuit 100 to the arithmetic unit 116, it is supplied to the arithmetic unit 116 as a high-speed signal. This current I5 is compared in arithmetic unit 116 with the ground voltage connected to the non-inverting input terminal. This calculator 116 is supplied with voltage ±Vc volts. The arithmetic unit 116 compares and amplifies the voltage due to the current I5 input to the inverting input terminal with the ground voltage, and outputs an output signal 112. At this time, computing unit 1
16 receives the supply of current 5 and outputs an output signal 112. Therefore, the non-inverting input terminal of the arithmetic unit 116 can be grounded. Therefore, when the input voltage supplied to the inverting input terminal is in the range from -Vc volts to 0 volts, this arithmetic unit 116 can output a valid output signal 122. This input voltage range corresponds to a half range of the voltage (±Vc volts) supplied to the arithmetic unit 116.

As described above, the current mirror circuit 100 is provided, and one output of the current mirror circuit 100 is used to reproduce pit information (recorded information) formed in a track on the optical disk 10. In addition, at this time, since the arithmetic unit 116 can output a valid output signal 122 when the range of the input terminal supplied to the inverting input terminal of the arithmetic unit 116 is from -Vc volts to 0 volts, the arithmetic unit 116 can output a valid output signal 122. It becomes possible to set a wide range of input voltages. moreover,
By making the first power supply 102 and the second power supply 104 equivalent, etc., the operating point of the current mirror circuit 100 can be changed, and by changing the operating point, the transistor 108 etc. can operate at an operating point where it is easy to operate. operation is possible.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to set a wide signal output range when reproducing recorded information.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the optical signal detection device of the present invention, FIG. 2 is a schematic configuration diagram of a disk device to which the information signal detection device of the present invention is applied, and FIG. 3 is the configuration of an optical disc. 4 are schematic configuration diagrams showing the lens actuator system. 48...Photoelectric conversion means. 100...first current circuit. 104...Power supply. 114.118,120...Transistor Figure 1

Claims (1)

Claims: Consisting of a first and a second transistor, collectors of the first and second transistors are connected to a power supply, a base of the first transistor, an emitter of the first transistor, and a a first current circuit connected to the base of the second transistor; a plurality of photoelectric conversion means whose cathodes are connected to the emitters of the first transistors of the first current circuit; and supply to the photoelectric conversion means. an optical signal detection circuit, comprising: a second current circuit that extracts a current equivalent to the current output from the emitter of the second transistor of the first current circuit.