JPS63138532A - Information reproducing device - Google Patents

Abstract

PURPOSE:To facilitate and ensure the pull-in operation into a focus enable range by moving a light collecting means in a vertical direction with respect to an information recording medium at a prescribed speed nearly equal to a face deflection speed of the information recording medium. CONSTITUTION:A control signal to move an objective lens 14 in the optical axis direction at a speed nearly equal to the face deflection speed within a prescribed speed difference in response to the face deflection speed of an optical disk 1 is fed from a CPU 33 to a focusing control circuit 26 via a D/A converter 35. Then the lens 14 is moved in its optical axis direction at a speed nearly equal to the face deflection speed by the CPU 33, the converter 35 and the focus servo system to pull the distance in between the recording face of the disk 1 and the lens 14 into a focus enable range. Through the constitution above, even if the face deflection speed of the disk 1 is changed by the setting change of the revolution speed of the disk 1 or the like, the pull-in operation within the focus enable range is ensured and quickened.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Field of Industrial Application) The present invention relates to an information reproducing device,
This is to ensure that the retracting operation in the J-bo system is performed reliably and quickly.

(Prior art) Generally, an optical disk device as an information reproducing device uses an optical disk having concentric or spiral recording tracks as an information recording medium.The recording track of such an optical disk rotated by a motor is On the other hand, a beam spot of a light beam emitted from a light source such as a semiconductor laser is projected, and this beam spot is moved in the radial direction of the optical disk so as to follow the recording track, and information is optically transmitted to the recording track. recording or playback.

Since the optical disk itself usually has "warpage," rotation causes surface wobbling on the optical disk. Although the surface runout M is defined within a predetermined range, in order to accurately record or reproduce information on the recording track, it is necessary to set the light source to the recording layer of the optical disk where such surface wobble occurs. It is required that the light beam from the . In other words, it is necessary that the light beam from the light source is always focused on the recording surface of the optical disc.

As such focusing means, the optical disc device 2 is equipped with a focus servo system.

The focus servo system includes, for example, a two-split detector for photoelectrically converting light reflected from an optical disk, a differential amplifier that differentially amplifies each output signal from the two-split detector and outputs a focus error signal, and a focus. It is comprised of a control circuit to which an error signal is supplied, a focusing drive coil, etc. that is controlled by an output signal from this control circuit. The focusing drive coil controls the movement of an objective lens that focuses a light beam from a light source in the direction of its optical axis.

And the optical disc is 400~600rprrl! ffl
The movement of the objective lens is controlled by the focus servo system in the following manner with respect to the optical disk which is rotated at a rotational speed of , and surface wobbling occurs due to this rotation.

That is, when the focus servo system starts in response to a focus-on command signal from a control system such as a CPU, the objective lens moves at a constant speed to the recording layer of the optical disk via a focusing drive coil in response to an output signal from the control circuit. can be approached. When this approaching movement of the objective lens brings the relative distance between the objective lens and the recording layer of the optical disk into the focusing range, focus lock is detected by the output signal of the differential amplifier at that time, and the control system A focus lock signal is then sent out, and thereafter the objective lens is automatically controlled so as to always be located within the focusable range.

Incidentally, in recent years, in order to shorten access time and increase processing speed for recording and reproducing on optical discs, there has been a tendency to increase the rotational speed of optical discs.
It has been raised to about m.

However, when the rotational speed of the optical disk is increased, a problem has arisen in that it becomes extremely difficult to bring the relative distance between the objective lens and the recording layer of the optical disk within a focusing range when starting the focus servo system. The difficulty of this retracting operation is thought to be due to the fact that the surface runout speed of the optical disk increases as the rotational speed of the optical disk increases.

(Problem to be Solved by the Invention) Conventionally, when starting the focus servo system, the objective lens was brought close to the rotating optical disk at a constant speed without considering the speed of the surface runout. There has been a problem in that when the speed of surface runout changes due to changes in the setting of the rotational speed of the optical disk, it becomes extremely difficult to pull the optical disk into the focusing range.

The present invention has been made based on the above circumstances, and it is an object of the present invention to provide an information reproducing device that can reliably and quickly perform an operation of pulling into a focusable range.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention includes a rotating means for rotating an information storage medium, and a light beam that emits a light beam to be irradiated onto the information storage medium. a light source, a condensing means for converging a light beam emitted from the light source onto the information storage medium, and condensing the light at a predetermined speed around the speed of surface deflection of the information storage medium caused by rotation by the rotation means. The object of the present invention is to include means for moving the means in a direction perpendicular to the information storage medium to bring the distance between the information storage medium and the light condensing means into a focusable range.

(Function) The moving speed of the light focusing means in the optical axis direction is controlled to a predetermined speed around the surface runout speed of the rotating information storage medium by the means for pulling the light into the focusing range, and the movement speed between the light focusing means and the information storage medium is The relative distance is brought within the focusable range. After retraction, the control system is locked and the condensing means is automatically controlled to be located within the focusable range.

(Example) Examples of the present invention will be described below based on FIGS. 1 to 4.

First, to explain the configuration of the information reproducing apparatus, in FIG. 1, 1 is an optical disk as an information recording medium, 2 is a motor (rotating means) for rotating the optical disk 1, and 3 is an optical head for recording and reproducing. .

The optical disc 1 includes a recording layer having concentric or spiral recording tracks, and one revolution is, for example, from 0 to
255'' and 256 sectors (not shown), and information is recorded in each sector. The motor 2 is controlled and driven by a motor control circuit 4.

The optical head 3 is attached to a movable part 5 of a DC linear motor, and is thereby linearly moved in the radial direction of the optical disc 1. The linear motor is equipped with a fixed part (not shown) having a permanent magnet, and a movable part 5 having a drive coil 6 moves directly on the permanent magnet of this fixed part. 7 is an optical scale fixed to the movable part 5, and 8 is a detector (transmission type optical sensor) that optically detects the position of the optical scale 7. The movable part 5 (that is, the optical head 3) position is detected. The output signal of the detector 8 is supplied to a linear motor control circuit 9.

The linear motor control circuit 9 controls the positioning of the movable part 5 of the linear motor, that is, the optical head 3, in accordance with the target position δ signal supplied from the CPLI and the output signal of the detector 8, which will be described later. The moving distance of the optical head 3 is detected based on the output signal, and the speed of the linear motor is controlled according to the moving distance.

The optical head 3 includes a semiconductor laser 11 which is a light source for emitting a light beam, a collimator lens 12, a polarizing beam splitter 13, which converges the light beam onto the recording layer on the optical disk 1, and sends the light to the recording layer on the optical disk 1. An objective lens 14 serves as a focusing means for positioning the beam spot of the beam; a focusing drive coil 15 moves the objective lens 14 in the direction of its optical axis; ) Tracking drive coil 16 and half prism 17
, a condensing lens 18, a knife lens 19, a focus position sensor 21 consisting of a two-split detector for receiving reflected light from the optical disk 1 and performing photoelectric conversion, and a condensing lens 22.
A tracking position sensor 23, which is a two-split detector for receiving reflected light from the optical disc 1 and converting the light, is also provided.

The semiconductor laser 11 is driven by a laser power control circuit 24 to perform oscillation, and a light beam is emitted. in this case,
When recording information on the optical disc 1, a light beam whose light intensity is modulated according to the information to be recorded is emitted, and when reproducing information from the optical disc 1, a constant light intensity is emitted. A light beam is emitted.

The light beam from the semiconductor laser 11 is collimated by the collimator lens 12 and then sent to the polarizing beam splitter 13, which converts the light beam to the optical disk 1.
reflected to the side. The reflected light beam passes through objective lens 1
4, the beam spot is positioned and irradiated onto a recording track provided in the recording layer on the optical disk 1. The reflected light from the optical disc 1 due to this light irradiation passes through the objective lens 14, further passes through the polarizing beam splitter 13, and is guided to the half prism 17.
This half prism 17 separates the light into two systems.

One of the separated reflected lights passes through the condensing lens 18 and the knife 19, forms an image on the light receiving surface of the focus position sensor 21, and is photoelectrically converted.

Each output signal of this focus position sensor 21 is used for focusing control. The other reflected light separated by the half prism 17 passes through the condensing lens 22 and forms an image on the light receiving surface of the tracking position sensor 23, where it is photoelectrically converted. Each output signal of the tracking position sensor 23 is used for tracking control and reading recorded information.

Focus position? Each output signal of the sensor 21 is supplied to a differential amplifier 25, and a focus error signal on the optical disc 1 is obtained from the output of the differential amplifier 25. A focus error signal output from the differential amplifier 25 is supplied to a focusing control circuit 26.

The focusing it, II control circuit 26 controls the focusing drive coil 1 according to the input focus error signal.
5, the objective lens 14 is driven in the optical axis direction, and the objective lens 14 is automatically controlled within a focusing range so that the light beam irradiated onto the optical disk 1 is just in focus. be. Focusing control circuit 26
is equipped with lock detection means for detecting focus lock based on the output of the differential amplifier 25 when the objective lens 14 is located within the focusable range. Focus lock signals etc. are sent to A/D converter 27 and data bus 2.
8 to the CPU, which will be described later. A focus servo system is constituted by the focus position sensor 21, differential amplifier 25, focusing control circuit 26, focusing drive coil 15, and the like.

On the other hand, the output signals of the tracking position sensor 23 are each supplied to two differential amplifiers, and a tracking position deviation signal is obtained from the output of the differential amplifier 29. The trunking position shift signal output from the differential amplifier 29 is
The signal is supplied to the tracking control circuit 31.

The tracking control circuit 31 controls the tracking drive coil 16 according to the input tracking position deviation signal, drives the objective lens 14 in the radial direction of the optical disc 1, and keeps the beam spot of the light beam on the optical disc 1 at all times. It is located on a recording track provided in the recording layer, and performs tracking control so that the beam spot accurately follows the recording track. The tracking position sensor 23, the differential amplifier 29, and the tracking control circuit 3
1, a tracking drive coil 16, and the like constitute a tracking servo system.

When tracking is being performed by the tracking servo system, the servo is applied not only to the objective lens 14 but also to the linear motor control circuit 9, and the positioning of the light beam is performed using the objective lens 14 and the linear motor.

Further, each output signal of the tracking position sensor 23 is supplied to a video circuit 32, respectively. The video circuit 32 adds each output signal of the tracking position sensor 23 to generate a reproduction signal of the recorded information, that is, a video signal reflecting the bits in the recording track, and converts the video signal into a binary signal. It outputs reading information.

The data bus 28 includes a CP which controls the entire device.
u <central processing unit) 33,
A CPLI memory 34 that stores the operation program of the CPU 33, speed control data of the objective lens 14 during retraction operation, eccentricity correction data, etc., a D/Δ converter 35 for analog conversion of various control signals, etc. from the CPU 33, and a motor control circuit. 4 is connected.

A control signal from the CPU 33 for moving the objective lens 14 in the optical axis direction at a speed before and after the speed of the surface wobbling within a predetermined speed difference according to the speed of the surface wobbling of the optical disc 1 is D.
Focusing control circuit 2 via /A converter 35
6.

Then, the CPU 33, the D/A converter 35, and the focus servo system move the objective lens 14 in the optical axis direction at a speed around the speed of the surface runout, and move the objective lens 14 between the recording surface of the optical disk 1 and the objective lens 14. It is possible to focus at a distance of I'! A means is constructed for retracting the lens into the focusing range and, after retracting, self-helping R, 11 to control the objective lens 14 to a focusing range.

Next, the operation will be explained.

First, to explain the access operation, position information recorded in advance on the recording track of the optical disc 1 is read,
Rough access is performed by moving the optical head 3 with a linear motor. When approaching the target recording track, the tracking servo system performs precise access using the objective lens 14, and the light beam is moved to the target recording track. These access operations are performed under the control of the CPU 33. Incidentally, since such an access operation is already well known, further explanation will be omitted.

Next, (A>, (B), (C) in Figures 2 to 4
The operation of retracting the objective lens 14 into the focusable range using the following will be explained.

Before recording or reproducing information on the optical disc 1, the optical disc 1 is rotated by the motor 2, and during this initial rotation, a retracting operation is performed at an arbitrary position on the optical disc 1.

First, in the focus error signal output from the focus position sensor 21 shown in FIG. 2, point F indicates the in-focus point (just in focus).

The just focus point F is the point where the beam waist of the light beam emitted from the semiconductor laser 11 is located on the recording surface of the optical disk 1, and although it is shown as a point in FIG. 2, the beam waist is actually The length, that is, the range of just focus, is approximately ±2 μm.

The focus servo system adjusts the position of the objective lens 14 so as to obtain just focus. In FIG. Relative distance between surfaces el
When l is drawn into this focusable range, the focus servo system is focus-locked, and thereafter the position of the objective lens 14 is automatically controlled so that just focus F is obtained.

In the waveform of surface runout of the optical disc 1 shown in FIG. 3, ΔX
indicates an interval corresponding to the focusable range n in FIG. 2, and hereinafter this range of ΔX will also be referred to as the focusable range.

(A> in FIG. 4 is an enlarged view of the P and Q surface runout waveforms from the surface runout waveform in FIG. 3. (B) shows the moving speed of the objective lens 14 in the optical axis direction when retraction is performed. In (B) of FIG. When the objective lens 14 is moved at a high speed, E is when the objective lens 14 is moved at a speed slower than the surface runout speed by a predetermined speed difference.
As mentioned above, G is a moving speed that is approximately intermediate between the moving speed of E, and this is the case where the objective lens 14 is moved at a speed that is approximately equal to the speed of surface wobbling.

The moving speed of the objective lens 14 and the moving speed E are CP
(Control signals corresponding to each of the moving speeds and E are supplied from J33 to the focusing control circuit 26 via the D/A converter 35, and the focusing drive coil 15 is controlled by the focusing control circuit 26. It will be done.

The control signal corresponding to the moving speed RI or the moving speed E output from the CPLI 33 is calculated each time by the CPU 33 based on the focus error No. 18 inputted to the CPU 33 via the Δ/D converter 27. Alternatively, since the surface runout speed changes in accordance with the rotational speed of the optical disc 1, control data obtained in advance based on the rotational speed of the optical disc 1 is stored in the CPU memory 34, and is read out by the CPU 33 for control. CPtJ3 as signal
Either method can be adopted, such as outputting from 3.

In addition, (C) in Fig. 4 shows the objective lens 1/l a3
j: indicates the change in the relative distance between the recording layers of the optical disc 1, and each characteristic line d, e, and g corresponds to (△) in FIG.
Displacements P and Q of surface runout and objective lens 1 in (B) of Fig. 4
This is calculated as the difference between each moving speed of 4, E, and G.

When the objective lens 14 is moved at a speed faster than the surface runout speed of the optical disc 1 by a predetermined speed difference, the objective lens 14 easily approaches the recording layer of the optical disc 1 where the surface runout is occurring, and the optical disc During one rotation of 1, the focusable range ΔX is reached. Furthermore, when the objective lens 14 is moved at a moving speed E that is slower than the surface runout speed of the optical disk 1 by a predetermined speed difference, the recording surface of the optical disk 1 that is wobbling comes closer to the objective lens 14. , during the second rotation of the optical disc 1, the focus is drawn into the focusable range ΔX in the same way as above.

On the other hand, if the objective lens 14 is moved at a moving speed Gt' that is approximately equal to the moving speed of the optical disc 1, the relative distance between them will not decrease and it will be difficult to draw the objective lens into the focusable range ΔX.

As described above, when the objective lens 14 is moved at a moving speed of 8 times or a moving speed of E, the optical disc 1 has surface wobbling.
, during one or two revolutions at startup, reliably n
The pull-in operation to the focusable range ΔX is quickly performed.

When the objective lens 14 is drawn into the focusable range Δx, the focusing control circuit 2
Focus lock is detected by the lock detection means in 6, and a focus lock signal is sent to the CPU 33 via the A/D converter 27. After the focus is locked, the objective lens 14 is automatically controlled by the CPU 33 so that it is always located within the focusable range ΔX and just focus is obtained.

[Effects of the Invention] As explained above, according to the present invention, the focusing means is perpendicular to the information storage medium at a predetermined speed around the speed of surface deflection of the information storage medium by the means for pulling the light into the focusing range. Since the distance between the information storage medium and the objective lens is brought into the focusing range, even if the speed of surface deflection of the information storage medium changes due to changes in the rotation speed of the information storage medium, etc. There is an advantage that the pull-in operation to the focusable range can be performed reliably and quickly.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the information reproducing apparatus according to the present invention, in which FIG. 1 is an overall configuration diagram, FIG. 2 is a waveform diagram of a focus error signal, and FIG. 3 is a diagram of an optical disc. FIG. 4 is a waveform diagram showing an example of surface runout, and FIG. 4 is a characteristic diagram showing the moving speed of the objective lens. 1: Optical disk (information storage medium), 2: Motor (rotating means), 3: Optical head, 11: Semiconductor laser (light source) 14: Objective lens (focusing means), 15: Focusing drive coil, 16: Tracking drive coil , 21: Focus position sensor, 25: Differential amplifier, 26: Focusing control circuit, 33: CPU.

Claims (1)

[Claims] Rotating means for rotating an information storage medium; a light source for emitting a light beam to be irradiated onto the information storage medium; and a condenser for converging the light beam emitted from the light source onto the information storage medium. means, and moving the light condensing means in a direction perpendicular to the information storage medium at a predetermined speed around the speed of surface deflection of the information storage medium caused by the rotation by the rotation means, so that the information storage medium and the condensation An information reproducing device comprising: means for reducing the distance between the optical means and the optical means to a focusable range.