JPH04364392A - Speed detection circuit - Google Patents

Abstract

PURPOSE:To detect a speed of an optical head without adverse influence to a vibrating characteristic by using a driving coil of a linear motor. CONSTITUTION:In a linear motor 31 having a driving coil 13 movable relatively to a magnetic member 31a in a direction crossing a magnetic flux generated by the member 31a, a relative speed of the coil 13 and the member 31a, i.e., a moving speed of an optical head 3 by the motor 31, is detected by utilizing an electrical change in the coil 13 generated at a moment of crossing the magnetic flux by the coil 13.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed detection circuit for detecting the moving speed of an optical head used in an optical disk device for recording information on an optical disk or reproducing information from an optical disk.

0002

2. Description of the Related Art Generally, in an optical disc device that records information on or reproduces information from an optical disc, information is recorded and reproduced using an optical head that moves linearly in the radial direction of the optical disc. This optical head is moved by a linear motor.

The moving speed of the optical head is determined by time-differentiating position information obtained from a photodetector provided on the movable part of the linear motor and an optical scale.
Detected.

As described above, since optical scales and photodetectors have been used to detect speed, if an optical scale or photodetector is attached to the moving part of a linear motor, resonance may occur in the movement of the optical head during high-speed movement. There was a problem in that vibration characteristics were adversely affected.

[0005]

[Problems to be Solved by the Invention] Conventionally, there has been a problem in that vibration characteristics are adversely affected, such as resonance occurring in the movement of the optical head.

[0006] The present invention has been made in view of the above points, and is a speed detection method that can perform speed detection without using an optical scale or photodetector, and can perform speed detection without adversely affecting vibration characteristics. The purpose is to provide circuits.

[0007]

[Means for Solving the Problems] The speed detection circuit of the present invention includes a magnetic material that generates magnetic flux, a conductor that is movable in a direction transverse to the magnetic flux generated by the magnetic material, and a conductor that moves together with the conductor. a moving body that moves the conductor and the movable body by controlling the current in the conductor, a detection means that detects an electrical change inside the conductor that occurs at the moment the conductor crosses the magnetic flux. , and a detection means for detecting the relative movement speed between the conductor and the magnetic material using the electrical change detected by the detection means.

[0008]

[Operation] In the above configuration, the present invention provides a conductor body movable in a direction transverse to the magnetic flux generated by the magnetic material, and a movable body is moved together with the conductor body to control the current in the conductor body. By moving the conductor and the moving body, detecting an electrical change inside the conductor that occurs at the moment when the conductor crosses the magnetic flux, and using this detected electrical change to move the conductor and the magnetic material. It is designed to detect the relative movement speed with respect to the vehicle.

[0009]

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. In other words, a recording medium 1 composed of an optical disk or the like
Spiral grooves (recording tracks) are formed on the surface of the recording medium 1, and the recording medium 1 is rotated by a motor 2 at, for example, a constant speed. This motor 2 is controlled by a motor control circuit 18. Recording and reproduction of information on the recording medium 1 is performed by an optical head (moving body) 3 provided at the bottom of the recording medium 1.

Note that the recording medium 1 uses a recording film in which pits are formed by perforation, but
A recording film or a multilayer recording film that utilizes phase change may be used, and a magneto-optical disk or the like may be used as the recording medium. In the above case, the configuration of the optical head and the like is similarly changed.

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

Furthermore, the laser light generated by the semiconductor laser oscillator 9 driven by the laser control circuit 14 is
The recording medium 1 is irradiated via the collimator lens 11a, the half prism 11b, and the objective lens 6, and the reflected light from the recording medium 1 is reflected by the objective lens 6 and the half prism 1.
1b, a condensing lens 10a, and a cylindrical lens 10b. The photodetector 8
is composed of four divided photodetection cells 8a, 8b, 8c, and 8d.

The output signal of the photodetection cell 8a of the photodetector 8 is supplied to one end of adders 30a and 30c via an amplifier 12a, and the output signal of the photodetection cell 8b is supplied to one end of the adder 30a, 30c via an amplifier 12a.
2b to one end of adders 30b and 30d,
The output signal of the photodetection cell 8c is supplied to the other end of the adders 30b and 30c via an amplifier 12c, and the output signal of the photodetection cell 8d
The output signal is sent to adders 30a and 3 via amplifier 12d.
It is designed to be supplied to the other end of 0d.

The output signal of the adder 30a is supplied to the inverting input terminal of the differential amplifier OP1.
The output signal of the adder 30b is supplied to the non-inverting input terminal of the adder 30b. Thereby, the differential amplifier OP1 supplies a track difference signal to the tracking control circuit 16 according to the difference between the adders 30a and 30b. This tracking control circuit 16 creates a track drive signal according to the track difference signal supplied from the differential amplifier OP1.

A track drive signal output from the tracking control circuit 16 is supplied to the drive coil 4 in the tracking direction. Further, the track difference signal used in the tracking control circuit 16 is supplied to the linear motor control circuit 17.

The linear motor control circuit 17 applies a voltage corresponding to the moving speed to a drive coil (conductor) 13 in the linear motor 31, which will be described later, in response to a track difference signal from the tracking control circuit 16 and a movement control signal from the CPU 24. is applied.

The linear motor control circuit 17 utilizes an electrical change inside the drive coil 13 that occurs at the moment the drive coil 13 in the linear motor 31 crosses the magnetic flux generated by the magnetic member (magnetic material) 31a, which will be described later. A speed detection circuit 40 is provided to detect the relative speed between the drive coil 13 and the magnetic member 31a, that is, the moving speed of the linear motor 31.

The output signal of the adder 30c is supplied to the inverting input terminal of the differential amplifier OP2, and the output signal of the adder 30d is supplied to the non-inverting input terminal of the differential amplifier OP2. Thereby, the differential amplifier OP2 supplies a signal regarding the focus point to the focusing control circuit 15 according to the difference between the adders 30c and 30d. The output signal of the focusing control circuit 15 is supplied to the focusing drive coil 5, and is controlled so that the laser beam is always in just focus on the recording medium 1.

Each photodetection cell 8a, . . . of the photodetector 8 with focusing and tracking performed as described above
The sum signal of the outputs of the adders 8d, that is, the output signals from the adders 30a and 30b, reflects changes in reflectance from pits (recorded information) formed on the tracks. This signal is supplied to the signal processing circuit 19, and this signal processing circuit 19
Recorded information and address information (track number, sector number, etc.) are reproduced. Further, a recording signal generation circuit 34 as a modulation circuit that modulates the recording signal is provided upstream of the laser control circuit 14.

The reproduction signal (reproduction information) reproduced by the signal processing circuit 19 is outputted to a recording medium control device 33 as an external device via an interface circuit 32.

This disk device also includes a focusing control circuit 15, a tracking control circuit 16, and
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 includes:
The objective lens 6 is moved in response to a track jump signal supplied from the CPU 23 via the D/A converter 22, and the beam light is moved by one track.

The laser control circuit 14, focusing control circuit 15, tracking control circuit 16, linear motor control circuit 17, motor control circuit 18, signal processing circuit 1
9. The recording signal generation circuit 44 and the like are controlled by the CPU 23 via the bus line 20, and the CPU 23 is configured to perform predetermined operations according to a program stored in the memory 24.

The optical head 3, as shown in FIG.
Guide rail 51 fixed to a frame (not shown)
, 52 as guides, it can be moved reciprocally (in the radial direction of the recording medium 1). optical head 3
The carriage 53 is connected to a drive coil 13 as a movable part of the linear motor 31.

The linear motor 31 includes a yoke-shaped magnetic member 31a, a permanent magnet (magnet) 32 adhesively fixed to the inner surface of the magnetic member 31a, and the magnetic member 31.
It is constituted by a drive coil 13 that is provided movably on a.

The drive coil 13 moves on the magnetic member 31a in response to the voltage applied by the linear motor control circuit 17 and the magnetic field generated from the permanent magnet 32 attached to the magnetic member 31a. As the drive coil 13 moves, the optical head 3 is also moved.

Further, the drive coil 13 is connected to a speed detection circuit 40 within the linear motor control circuit 17. This speed detection circuit 40 outputs a speed signal corresponding to the moving speed of the drive coil 13, that is, the optical head 3, by checking the amount of current flowing through the drive coil 13. As shown in FIG. 3, the speed detection circuit 40 includes a resistor R inserted in series with the drive coil 13 to detect the current flowing through the drive coil 13, and outputs a voltage value applied to the drive coil 13. A differential amplifier circuit 41 that outputs the current value flowing through the resistor R, a differentiating circuit 43 that differentiates the current value flowing through the resistor R from the amplifier circuit 42, an output of the differential amplifier circuit 41, an amplifier circuit 42 that outputs the current value flowing through the resistor R, Output, differentiation circuit 43
It is constituted by an adder circuit 44 that adds the outputs of .

From the differential amplifier circuit 41, as shown in FIG.
A signal obtained by amplifying the voltage applied to the drive coil 13 as shown in FIG. 4(c) from the differentiating circuit 43.
A differential signal as shown in FIG.
A signal (velocity signal) obtained by combining the output signals from 3 and 3 is output. The relationship between electrical signals regarding the drive coil 13 in the linear motor 31 shown in FIG. 1 can be expressed as follows. E=RI+vB1-L(dI/dt)...(1)

However, the voltage applied to the coil is E, the resistance is R, the current flowing through the coil is I, the self-inductance is L, the effective length of the coil is 1, the air gap magnetic flux density is B, and the moving speed is v. Therefore, the moving speed v can be expressed by the following equation. v=E−RI+L(dI/dt) … (
2) The content of this equation 2 is the addition (synthesis) of the adder circuit 44
It corresponds to the content.

Next, the operation of detecting the moving speed of the optical head 3 in the above configuration will be explained. A predetermined voltage value is applied to the drive coil 13 by the linear motor control circuit 17 . As a result, the current-carrying drive coil 13 receives the magnetic field generated from the permanent magnet 31b and moves on the magnetic member 31a.

The voltage applied to the drive coil 13 is amplified by the differential amplifier circuit 41 and output to the adder circuit 44. The current flowing through the drive coil 13 is amplified by the amplifier circuit 42 and output to the adding circuit 44, and the current from the amplifier circuit 42 is differentiated by the differentiating circuit 43 and output to the adding circuit 44.

The adder circuit 44 adds and synthesizes the signals from the respective parts ((a) to (c) in FIG. 4) based on the above-mentioned formula 2, so as to generate a signal as shown in (d) in FIG. Obtain a speed signal waveform.

Speed data corresponding to the speed signal from this adder circuit 44 is output to the CPU 23, and
The current moving speed of the optical head 3 is determined from the speed data from the adding circuit 44, and voltage is again applied to the drive coil 13 by the linear motor control circuit 17 so that the target speed is achieved.

The speed signal waveform shown in FIG. 4(d) above shows the state of movement of the optical head 3 by the linear motor 31 when acceleration, stop, acceleration in the opposite direction, and stop are repeated. ing.

As described above, in a linear motor having a drive coil that can move relative to the magnetic material in a direction transverse to the magnetic flux generated by the magnetic material,
The relative speed between the drive coil and the magnetic material, that is, the moving speed of the linear motor (optical head), is detected by using the electrical changes inside the drive coil that occur at the moment the drive coil crosses the above magnetic flux. be. Thereby, speed detection can be performed without using an optical scale or a photodetector, and speed detection can be performed without adversely affecting vibration characteristics. Therefore, the speed can be detected by calculating the signal applied to the drive coil of the linear motor without using a special speed detection coil.

[0036]

[Effects of the Invention] As detailed above, according to the present invention,
It is possible to provide a speed detection circuit that can perform speed detection without using an optical scale or photodetector, and can perform speed detection without adversely affecting vibration characteristics.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a linear motor in 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 the circuit configuration of the speed detection circuit shown in FIG. 2;

FIG. 4 is a diagram showing output signals of each circuit in the speed detection circuit of FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Recording medium, 3... Optical head (moving body), 6... Objective lens, 13... Drive coil (conductor), 17... Linear motor control circuit, 23... CPU, 31... Linear motor, 31
a...Magnetic member (magnetic material), 31b...Permanent magnet, 40...
speed detection circuit, 41... differential amplifier circuit, 42... amplifier circuit,
43...differentiation circuit, 44...addition circuit, 53...carriage.

Claims (1)

[Claims] Claim 1: A magnetic material that generates a magnetic flux, a conductor that is movable in a direction transverse to the magnetic flux generated by the magnetic material, a movable body that moves together with the conductor, and a conductor that is movable in a direction that crosses the magnetic flux generated by the magnetic material. a moving means for moving the conductor and the moving body by controlling current; a detection means for detecting an electrical change inside the conductor that occurs at the moment the conductor crosses the magnetic flux; A speed detection circuit comprising: a detection means for detecting the relative movement speed of the conductor and the magnetic material using electrical changes.