JPH01253839A - Device for correcting inclination of light beam - Google Patents

Abstract

PURPOSE:To allow a disk even having deflection to follow a pickup by detecting a driving current from the actuator driving part of a focus servo, making a distance between the pickup and the disk constant and controlling the inclination of the pickup so that the light beams always become vertical to a disk surface. CONSTITUTION:The pickup 3 including an objective lens 4 and a linear motor 5 generating thrust are mounted on a guide rail 7 which vertically rocks around a turning fulcrum 6 and moved in the radius direction of the disk 1. The output of an inclination detection detector in the pickup 3 are impressed on a driving amplifier 13 through the switches of phase compensation circuits 11 and 12, and a motor 14 is operated by the outputs, whereby the guide rail 7 is allowed to move vertically so that the radiated surface of the light beams from the objective lens 4 and the disk 1 becomes always vertical. A height signal detection circuit in the pickup 3 detects the height of the focus servo actuator and impresses the position signal of the pickup 3 on the amplifier 13 through a switch 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a light beam tilt correction device for controlling the tilt of the disc and the light beam to be completely constant in an information recording/reproducing device such as an optical disc (hereinafter referred to as a disc). It is.

2. Description of the Related Art In recent years, so-called optical disk devices such as video disk players and compact disk players that reproduce information signals recorded on a disk by fully utilizing the reflected light of the original beam have become popular. Furthermore, optical disk file devices that can also record information signals by changing the power of the light beam are becoming popular for industrial use. Such a source disk device has a means called a pickup that irradiates the entire disk with an n-light beam and detects the reflected light.

Furthermore, there are focus servo means for aligning the focus of the light beam output from the pickup with the recording surface of the disk, and tracking servo means for causing the beam to follow the track of the sporatra disk having a diameter of about 1 μm.

In addition, the disk has static and dynamic deflections due to its own weight and during rotational drive, as well as inherent deflections during molding.This deflection becomes particularly large near the outer periphery of the disk, causing the beam spot to become elliptical on the disk. This may result in increased crosstalk with adjacent tracks. For this reason, video disc players and the like are equipped with a light beam tilt correction device that controls the tilt of the pickup so that the optical axis of the light beam is always perpendicular to the disc surface regardless of the deflection of the disc.

A conventional example will be described below with reference to the drawings. FIG. 3 is an example of a simple principle diagram for detecting the entire inclination of the disk and the light beam. The light emitting diode 16 is connected to the objective lens 4
The light emitting diode is arranged so that the light beam hits the vicinity of the light beam spot emitted from the light emitting diode, and the light emitted from the light emitting diode is substantially parallel to the original beam emitted from the objective lens 4. Furthermore, photodetectors 16 are mounted on both sides of the light emitting diodes 16 at symmetrical positions in the radial direction of the disk 1. The light emitted from the light emitting diode 15 is reflected by the disk 1, and the reflected light returns onto the photodetector 16. Therefore, if the light beam is tilted with respect to the disk 1 due to the deflection of the disk 1, the light emitting diode 1
Since the light emitted from the disk 6 is also tilted with respect to the disk 1, the intensity distribution of the reflected light returning onto the photodetector 16 changes, and by receiving the output at the differential amplifier 8, the output of the differential amplifier 8 A tilt error signal can be obtained.

FIG. 4 is a block diagram of a simple conventional example of a tilt correction device to which the tilt detection principle shown in FIG. 3 is applied. A flexible disk 1 is rotationally driven by a disk motor 2. The pickup 3 including the objective lens 4 generates thrust to move the entire pickup 3 in the radial direction of the disk 1, and together with the near motor 6, the pickup 3 includes a rotation fulcrum 6'ff: a guide rail that swings vertically around the center. 7
It is worn on top. The output of a photodetector for detecting the inclination of the light beam in the pickup 3 is received by a differential amplifier 8, and the output of the inclination error signal is sent to a phase compensation circuit 11.
．． Switch 12. The voltage is applied to the motor 14 through the entire drive amplifier 13. Further, the rotation shaft of the motor 14 is connected to the end of the guide rail 7 by a gear or the like, and the rotation of the motor 14 drives the guide rail 7 in the vertical direction, so that the light beam is always perpendicular to the irradiation surface of the disk 1. The tilt of the light beam is fully controlled.

Problems to be Solved by the Invention However, with such a conventional optical beam correction device, when the pickup moves at high speed over a long distance, such as when searching for an arbitrary track on the disk, depending on the deflection shape of the disk, If the focus servo actuator comes to a position outside of the dynamic range of movement during movement, the light beam spot will not be able to follow the signal recording surface and the recorded signal will not be able to be played back, causing the optical disc device to stop operating. There was a danger of falling.

FIG. 5 is a diagram briefly explaining the situation. This figure shows the movement of the guide rail and the objective lens 4 when the pickup 3 moves from track A on the inner circumference of the disk to track B on the outer circumference.

The operating position of the focus servo actuator that drives the objective lens 4 is adjusted so that it is at the center of the dynamic range when the guide rail 7 is in a parallel position and the disk 1 is not deflected. Therefore, as shown in FIG. 6, when the disk 1 is tilted upward near the outer track B and the height of the disk surface is close to the height in the parallel state, the focus servo is adjusted to the distance di between the disk surface and the objective lens 4. The objective lens 4 moves downward in the B track as shown in the figure because it operates to maintain a constant value. If the amount of movement at this time exceeds the dynamic range of the focus actuator, the focus servo will be unable to follow the focus, resulting in the optical disc device being stopped.

Means for Solving the Problems The present invention, which solves the above problems, includes a distance control means for detecting an actuator drive current from an actuator drive section of a focus servo and keeping the distance between the pickup and the disk constant, and a distance control means for controlling a light beam. a tilt control means for controlling the tilt of the pickup so that the light beam is always irradiated perpendicularly to the disk surface by detecting the angle; and means for switching between the distance control means and the tilt control means under predetermined conditions when the pickup is moving at high speed. It is equipped with the following.

Effects With this configuration, even if the focus servo cannot follow the conventional pickup's high-speed movement using only the tilt control means due to the deflection shape of the disk, it is possible to eliminate the risk that the optical disk device will stop operating, and to maintain stable operation. The optical disk device can now be operated.

Embodiment FIG. 1 is a diagram showing an embodiment of the present invention. disc 1
is rotationally driven by a disk motor 2. The pickup 3 including the entire objective lens 4 and the linear motor 6 that generates its thrust are both mounted on a guide rail 7 that can swing vertically around a pivot point 6, and move the disk 10 in the radial direction. Also, the output of the tilt detection detector in the pickup 3 is connected to the differential amplifier 81 and the phase compensation circuit 1.
1. The output of the drive amplifier 13 is applied to the drive amplifier 13 through the switch b of 12, and the output of the drive amplifier 13 rotates the motor 14, so that the light beam irradiated from the objective lens 4 and the irradiation surface of the disk 1 are always perpendicular to each other. Thus, a feedback control loop is formed to control the guide rail 7 in the vertical direction.

Further, the signal of the substantially vertical position of the pickup detected by the height signal detection circuit 9 from the focus servo actuator in the pickup 3 is transmitted to the switch ai of the pickup 3.
The signal is applied to the drive amplifier 13 via the signal, forming a feedback control loop that controls the distance between the pickup 3 and the disk 1, similar to the feedback control loop that controls the inclination of the original beam described above. 10 switch 4
The ON10 FF signal of switch b and 12 is controlled by a microcomputer, etc., and there is no possibility that the two switches are in the ON state at the same time. Switch 10 is O
N occurs when the pickup 3 searches for a track while moving at high speed, or when the height of the pickup 3 deviates to the extent that it deviates from the dynamic range of the focus servo actuator even during normal playback. This distance control loop is based on the height of the pickup 3 when the focus servo actuator is at the center of the dynamic range. Therefore, when the distance control loop is operating, the focus actuator always operates at the center of the dynamic range, and if the distance control loop is included during high-speed search, the focus servo becomes extremely stable.

FIG. 2 shows the principle of pickup height signal detection and the height signal detection circuit shown in the embodiment of FIG. 1.

FIG. 2 & is a diagram showing the frequency characteristics of the focus actuator, and to is the resonance frequency.

The movement of the actuator in the low frequency range is almost constant.
After detecting the current flowing on the day using a DC resistor RΩ and amplifying it with an amplifier 19, L, P, F 2o 1/C
A height signal in a lower frequency region is obtained. The amount of movement of the actuator is proportional to the current, and the operating position of the actuator relative to the pickup can be detected.At the same time, the objective lens that works with the actuator is kept at a constant distance from the disk by a focus servo, so the height of the pickup, which serves as a reference, can be determined. Once the height is determined, changes in height relative to the reference can be detected by the current flowing through the actuator. Furthermore, the output of the amplifier 19 is input to the microcontroller via a secondary LPF 21 and a comparator 22.
By providing the all-quadratic filter 21 with a characteristic close to the frequency characteristic of the actuator shown in a, the amount of movement of the actuator in the entire frequency range can be detected, and this amount of movement can be set in advance with respect to the dynamic range of the actuator. The comparator 22 compares the level with the safe operating range level, and inputs the output to the microcomputer to determine whether to switch between the distance control loop and the tilt control loop. In other words, the distance control loop is ONL when the pickup is moving at high speed, and the tilt control loop is basically ONL during normal playback.
However, if the amount of movement of the actuator exceeds the safe operating range, the distance control loop is turned on.

In this embodiment, an example was shown in which the distance control loop is unconditionally turned on when the pickup is moving at high speed. However, if the disk has a very gentle deflection within a short distance section, the distance control loop is turned off when the pickup is moving at high speed. is also valid.

In addition, by monitoring the tilt signal that is the output of the differential amplifier 8 shown in Fig. 1 with a microcomputer, etc. as shown in Fig. 2, it is possible to detect movement of the focus actuator and to adapt to the deflection shape of the disk. High performance and reliable control can be achieved.

Effects of the Invention As described above, an optical disk device equipped with the light beam tilt correction device of the present invention has a distance control loop during movement to maintain focus even when the pickup moves at high speed with respect to a deflected disk. Since the pickup is controlled so that the operating position of the actuator is at the center of the dynamic range, the focus servo will not be unable to follow during movement, and the original light beam tilt control loop will operate during normal playback, improving reliability. becomes very high. Furthermore, according to the present invention, by inputting the optical beam tilt signal and the pickup height signal to a microcomputer, etc. and switching the control system, stable and high-performance control with a large margin against disk deflection can be achieved. We can provide optical disk devices.

[Brief explanation of the drawing]

Figure 1 shows an embodiment of the present invention.
, b are waveform diagrams and circuit diagrams of the main parts of the same embodiment, FIG. 3 is a schematic diagram showing an example of conventional light beam tilt detection, and FIG. 4 shows a conventional light beam tilt correction device. The block diagram, FIG. 6, is an explanatory diagram of the case where the focus servo is off due to a warped disk. 1...Disc, 3...Pickup,
4...Mark: Objective lens, 9...Height signal detection circuit. Name of agent: Patent attorney Satoshi Nakao and 1 other person1-
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Claims (2)

[Claims] (1) In order to record an information signal on an optical disk or to reproduce an information signal already recorded from the optical disk, a pickup that irradiates a light beam onto the signal recording surface of the optical disk, and a pickup that focuses the light beam on the signal recording surface of the optical disk. a focus servo means for driving and controlling an objective lens mounted on the pickup to bring the optical disc into focus; a light beam inclination detecting means for detecting the inclination of the optical disc and the light beam; A pickup rocking means that can control the height and tilt of the pickup in the vertical direction, and a height signal that is a signal of the vertical position of the pickup with respect to the optical disk are detected by the focus servo means, and a pickup distance control means for controlling the pickup swinging means to maintain a constant distance from the optical disc; and a pickup swinging means for controlling the light beam to be substantially perpendicular to the optical disc by means of the light beam inclination detection means. a pickup tilt control means for controlling the
A control system switching means is provided for switching between the distance control means and the tilt control means, and when the pickup moves in the radial direction of the optical disc at high speed, such as when searching for an arbitrary track on the optical disc, the control system is switched between the distance control means and the tilt control means. A light beam tilt correction device characterized in that the distance control means is operated by the switching means. (2) comprising a determination means for determining which of the distance control means and the tilt control means should be operated based on the tilt signal output from the light beam tilt detection means and the pickup height signal;
2. The light beam tilt correction apparatus according to claim 1, wherein said determining means controls switching means of said control system.