JPH03105732A - Optical disk device - Google Patents

Abstract

PURPOSE:To eliminate the need for an expensive position and relative speed detector and to control an optical head at a low speed to prevent runaway by detecting an open voltage (voltage corresponding to the counter electromotive force) generated in a coil when a linear motor is driven intermittently and no current flows for a drive idle period as a speed thereby using the speed for the speed control. CONSTITUTION:A motor is driven intermittently to drive an optical head 11 at a low speed, an open voltage across a coil 12a of the motor for a drive idle period is detected and the open voltage is regarded as a speed of the optical head 11 to apply the open voltage. That is, the open voltage across the coil proportional to the speed at that time is detected as a speed for a drive idle period when no current flows to the coil 12a of the motor and a current flows to the coil 12a for the drive period so as to attain an object speed thereby attaining the object speed. Thus, no position and relative speed detector is required, the cost is reduced and when unsynchronization of focus servo is detected during the drive of the optical head 11, the object speed is brought into 0 to prevent runaway of the optical head 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc device for recording and reproducing code data, image data, audio data, and the like.

2. Description of the Related Art Conventionally, this type of optical disk device has an optical head consisting of an objective lens that produces a light spot on a data recording medium, and a lens actuator that positions the objective lens within a small range at high speed. Positioning is performed by driving an electromagnetic motor such as a linear motor. Therefore, the objective lens is controlled by a two-stage servo lube.

In order to shorten the access time, the optical head is often driven in linear mode as described above, and it is common to detect the speed of the optical head by some method and perform speed control. .

When the objective lens is controlled by focus servo in a direction perpendicular to the data recording medium so that a light spot is generated on the data recording medium, a track error signal indicating the relative position of the objective lens with respect to the track can be detected. The relative velocity of the objective lens with respect to the track can be detected by differentiating, for example, and if the relative velocity can be detected, the velocity can be controlled.

However, this only occurs when the focus servo is engaged; if there is no data recording medium, or even if the focus servo is disengaged due to large vibrations, the tracking error signal is not output, so the optical head The speed cannot be controlled, and in the worst case, the optical head will run out of control.

Therefore, conventional optical disk devices are provided with a sensor that can detect the position or speed of the optical head relative to the drive, and the signal from this sensor is used to prevent the optical head from running out of control.

As shown in the schematic diagram of FIG. 7, the conventional optical disc device
a spindle motor 2 that rotates the data recording medium 1;
An optical head 5 driven by a linear motor 4 on the housing 3
, an objective lens 7 positioned by a lens actuator 6 on the optical head 5, and a position/relative speed detector 8 for detecting the position or relative speed of the optical head 5 with respect to the housing 3.

Problems to be Solved by the Invention However, in the conventional optical disk device described above, it is necessary to provide a position/relative velocity detector 8 that can detect the position/relative velocity over the entire movable range of the optical head 5. However, since this position/relative velocity detector 8 is generally expensive, there is a problem in that it is difficult to reduce the cost.

The present invention solves these conventional problems,
An object of the present invention is to provide an optical disc device that prevents an optical head from running out of control without using a position/relative velocity detector.

Means for Solving the Problems In order to achieve the above object, the present invention drives the optical head at low speed by intermittently driving the motor, detects the open circuit voltage across the coil of the motor when the drive is stopped, and detects this detection. The open-circuit voltage generated is regarded as the speed of the optical head, and the speed is controlled.

According to the above-mentioned configuration, the present invention detects the open circuit voltage across the coil, which is proportional to the speed at that time, as the speed during the drive rest period when no current is flowing through the motor coil, and the detected speed becomes the target speed. The speed is controlled by passing a current through the coil during the drive period, eliminating the need for a position/relative speed detector, making it possible to reduce costs, and
If a deviation of the focus servo is detected while the optical head is being driven, runaway of the optical head can be prevented by setting the target speed to "O".

Embodiment FIGS. 1(a) and 1(b) are a plan view and a front view schematically showing the structure of an embodiment of the present invention. Figure 1(a)
, (b), 1l is an optical head provided with a linear motor coil 12a, l3 is a housing, 14 is 14a. 14b is an origin position detector which indicates that the optical head 11 is at the origin position; 15 is an objective lens positioned by a lens actuator 16;

Figure 2 shows a block diagram of the linear motor control circuit. In Figure 2, 17 is a speed detector that receives a track error signal and detects the speed from the near motor current, and 18 controls the linear motor 12 using the track error signal. 19 is a differential amplifier for comparing the target speed and the detected speed; 20 is a phase compensation circuit for stabilizing the linear motor control loop by the output of the differential amplifier 19; 21 is a changeover switch 22, open/close. switch 2
3 is connected to the phase compensation circuit 20 to drive the linear motor 12, 24 is a 10kHz oscillator, and 25 generates a timing signal from the output signal of the oscillator 24 under the control of the linear motor controller l8. A timing generation circuit, 26 is a voltage detector at both ends of the coil of the linear motor 12, 27 is a primary hold circuit that monitors the sample/hold circuit connected to the voltage detector 26 via an open/close switch 28, and 29 is a changeover switch. be.

Next, the operation of the above embodiment will be explained. objective lens l
5 is driven by a lens actuator 16 so as to be able to move on the optical head 11 within a range of several hundred μm, and this optical head 11 is driven by a linear motor 12 to move on the housing 13. can be moved within a range of several tens of millimeters.

The access operation for positioning the objective lens 15 in order to record/reproduce arbitrary data is performed by moving the optical head 11 to a large size.
Moreover, it is different from coarse access in which coarse positioning is performed and fine access in which positioning is performed by finely moving the objective lens 15 to the target track.

In FIG. 2, the timing control circuit 25 includes the oscillator 2
The output of 4 is controlled by the LCIVEL signal output from the near motor controller 18. The detailed operation will be described later, but during normal servo, LO-VE
When the L signal is off, both the open/close switch 23 and the open/close switch 28 are on.

When focus servo is applied, a track error signal indicating the relative position of the objective lens 15 with respect to the track is obtained, so the speed detector 17 determines the speed of the optical head 11 with respect to the housing l3 from the track error signal. Strictly speaking, the speed obtained here is the relative speed of the objective lens 15 with respect to the track, not with respect to the housing 13, but when moving the optical head 11 largely as in rough access, the objective lens Since the displacement of 15 with respect to the optical head 11 can be ignored, it can be approximated as described above.

As shown in FIG. 3, the track error signal is output in the form of a triangular wave with respect to the relative position of the objective lens 15 with respect to the track, so the track error signal from the speed detector 17 is differentiated to obtain the absolute value. The speed is detected by taking the reciprocal of the cycle. Mainly, low frequency components of the detection speed are detected by the former, and high frequency components are detected by the latter.

At the time of rough access, by turning the changeover switch 29 to contact A, the output signal of the speed detector 17 is regarded as the detected speed, and is compared with the target speed output from the linear motor controller 18 by the differential amplifier l9. The servo circuit operates so that the detected speed and target speed match.

The linear motor controller 18 monitors the track error signal, always knows how many tracks are left to reach the target track, and determines the target speed based on the number of remaining tracks. Specifically, a speed profile as shown in FIG. 4 is output as the target speed.

The output signal of the differential amplifier 19 is sent to the phase compensation circuit 20, the changeover switch 22 connected to contact A, and the open/close switch 2 turned on.
3 to the power amplifier 21, and the linear motor l
Drive 2. This current of the linear motor 12 is fed back to the power amplifier 21. This power amplifier 2l is a so-called current drive type amplifier, and its input is a current command value. Thus, during rough access, speed control is performed using the speed obtained from the track error signal and the current of the near motor 12.

In the case of long-distance access, bang-bang control is performed to maximize the driving ability of the linear motor 12 in order to move the optical head 11 at high speed. In this case, the changeover switch 22 is placed in the contact position A, and the thrust of the linear motor 12 is directly controlled by the linear motor controller 18. That is, maximum thrust acceleration and maximum thrust deceleration are performed in order, and the optical head 11 is moved at high speed to the vicinity of the target track.

However, since this is oven control, the positioning error is large, and the speed control is then performed to position the target track.

On the other hand, when the focus servo is not applied, for example when there is no data recording medium, the tracking error signal is not detected, so the speed as described above. I can't control tl7. But what? If tIJ fil is not applied, the linear motor 12 may run out of control.
Usually, the position is controlled so that it is fixed at the origin position.

Here, the origin position is detected by the origin position detector 14 and the optical head 11 is fixed. However, since this origin position detector 14 is a simple device that can only detect a position near the origin, it cannot be fixed unless the optical head 11 is moved to the vicinity of that position.

Next, this method of movement will be explained with reference to the timing chart of FIG. First, the changeover switch 29 is turned on to contact C, the changeover switch 22 is turned on to contact A, and the control signal LO-VEL is turned on. This control signal LO-VE
When L is off, the open/close switch 23 and the open/close switch 28 are on, but when the control signal LO-VEL is on, the open/close switch 23 is turned on for a certain period of time by the input of the oscillator 24, and the target speed is detected. A signal related to the speed difference is input to power amplifier 21 . When the output of the oscillator 24 becomes low level, the open/close switch 23 is turned off and the input of the power amplifier 21 becomes "O". After a while, the current of the linear motor 12 also becomes "O", and at that time the voltage detector 2 detects the open voltage across the coil of the linear motor 12.
The output of 6 is proportional to the speed.

Therefore, the output proportional to the speed of the voltage detector 26 is sampled by the on/off switch 28 and temporarily held, and then passed through the changeover switch 29 to obtain the detected speed. In this way, the speed of the optical head 11 is controlled to the target speed output from the linear motor controller 18.

The output of the origin position detector 14 is as shown in FIG. 6, and there is no sudden change at any position other than the origin position. When this output is at a high level, the target speed is initially several tens of mm /
Set the low speed of s and move the origin position detector 1 in the outer circumferential direction.
The optical head 11 is moved until the output signal of No. 4 becomes low level. This low speed is such a speed that mechanical shock to the optical head 11 will not be a problem even if it hits a rubber limiter (not shown) that limits the range of movement of the optical head l1.

Conversely, if the output of the origin position detector 14 is low level from the beginning, the target speed is set to move at a low speed in the inner circumferential direction, and the output signal of the origin position detector 14 is set to a high level. Move the optical head 11 until the

In either case, when the polarity of the output signal of the home position detector 14 changes, the changeover switch 29 is turned on to contact A, and the target speed is set to "O". Then, the output signal of the origin position detector 14 is obtained by subtracting the reference voltage ref shown in FIG. Therefore, the optical head 11 is fixed at the origin position.

Effects of the Invention As described above, according to the present invention, by driving the optical head or driving the near motor intermittently, the open circuit voltage (reverse Since the configuration is configured to detect the electromotive force as the speed and control the speed, there is no need for an expensive position/relative speed detector that detects the position or relative speed over the entire movable range of the optical head, resulting in an inexpensive and compact optical disk device. In addition, the optical head can be controlled at a low speed to prevent runaway.

[Brief explanation of drawings]

FIG. 1(a) is a plan view schematically showing an objective lens positioning device which is a part of an optical disk device according to an embodiment of the present invention, FIG. 1(b) is a front view of FIG. 1(a), Figure 2 is a block diagram of the beam near motor control circuit, Figure 3 is a waveform diagram of the track error signal, Figure 4 is a graph showing the speed profile, Figure 5 is a timing chart, and Figure 6 is the output of the home position detector. The waveform diagram in FIG. 7 shows a conventional optical disc device. 11... Optical head, 12... Linear mode evening, 14.
...Origin position detector, l8...Linear motor controller, 26...Voltage detector.

Claims (2)

[Claims] (1) a motor that drives an optical head in a radial direction of an optical disk; a motor controller that drives the motor intermittently; a voltage detector that detects an open circuit voltage at both ends of a coil of the motor during a period when the motor is not driven; An optical disc device comprising: a servo circuit that controls the speed of an optical head so as to match a target speed output from the motor controller by regarding a voltage as a detected speed. (2) The optical disc device according to claim 1, further comprising an origin position detector for detecting the origin position of the optical head.