JPS61190727A - Optical device - Google Patents

Abstract

PURPOSE:To shorten the access time by using the 1st and 2nd sliders which move linearly toward the radius of a disk, putting the minimum number of members necessary for constitution of an optical head and giving independent control to the positions of both sliders. CONSTITUTION:An end of each of two parallel springs 26 is fixed to the 1st slider 4, and an objective lens 10 and a focus coil 22 are supported at the other end of each spring 26. While a permanent magnet 23 and a yoke 24 are fixed to the 2nd slider 12 at the outside of the coil 22. The coil 22 conducts and gives vertical displacement to the lens 10 against a disk. Thus the slider 4 contains the optical elements including the lens 10 which constitute a photomagnetic optical system and other light-weight parts like an automatic focus detector, an automatic tracking detector, etc. While the slider 12 contains the magnet 23 for focus control, the yoke 24 and other primary members and an external signal line. Both sliders 4 and 12 are driven independently of each other. The light-weight slider 4 vibrates from a position A for control and stops at a position B after t3sec. While the heavy slider 12 reaches the point A later than the slider 4 and stops at the position B after vibration of a long time. In such a way, the access time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an optical head device used in so-called optical recording and reproducing devices such as various optical disks and magneto-optical disks. The various types of optical discs here include types called write-once, which can be written only once and cannot be rewritten, types called read-only, which can only be played back, and types that can be erased using phase transformation (amorphous/crystal). This refers to optical discs such as the .

(Background of the Invention) Conventionally, optical recording and reproducing devices that use optical disks and magneto-optical disks as recording media have been put into practical use as large-capacity memories used for recording and reproducing information, and have a large information storage capacity. Therefore, during recording and reproduction, it is required to access a desired track position at high speed to record and reproduce information.

Therefore, an optical head device used in an optical recording/reproducing device is equipped with a slider that is moved in the radial direction of an optical disk or magneto-optical disk (hereinafter simply referred to as a disk) by a linear motor, etc., and the slider is used to record the optical disk on the slider. It is equipped with the optical system necessary for playback, a head circuit, and an actuator for controlling the focus of the objective lens, and is also connected to external signal lines.

As shown in the speed diagram of FIG. 7, access control of such an optical head device is performed first at a position just before the target position! The slider is moved toward tA by speed control using a linear motor based on an external scale, and then moved to target position B after time t1 by position N control. In this case, the slider cannot be suddenly stopped even when it reaches the target position, and the slider vibrates at the target position B for a predetermined settling time (t2-tl).
> Later, it will stop at the target position.

When the optical head is moved by the slider to the target track position determined by the external scale in this way, tracking control is started after stopping, the track information is read out, and the difference from the target track position is detected. Subsequently, the galvanometer mirror or objective lens is driven by the detected track difference to perform a track jump and capture the target track.

Therefore, the access time to move the optical head to the target track is the sum of the time t2 until the slider settles at the target position and the track jump time Δt (t2+Δt).
Normally, the time until settling is about 200 m5 ec, and the track jump time is about 10 m5 ec, and by shortening the time until settling, the access time can be shortened.

(Problems to be Solved by the Invention) However, in such conventional optical head devices, there was a problem that the optical head mounted on the slider was heavy and the access time was long. When the force constant is F and the slider movable part!II is M, the acceleration a generated in the slider is a-F/M...(
1) is given by. As is clear from this equation (1), when the movable type ff1M of the slider is large, the acceleration a becomes small, and the moving speed of the slider becomes slow, so that the time taken to move to the target position becomes long. Furthermore, if the movable type ff1M of the slider is large, the control responsiveness of the slider deteriorates and the settling time increases. That is, the heavier the head, the longer the access time.

The reasons for the increase in head weight, which increases the access time, are as follows, especially in heads for magneto-optical disks.

First, the slider equipped with the head is equipped with an external magnetic field electromagnetic coil that applies a perpendicular magnetic field to the magneto-optical medium, and since the strength of the magnetic field usually requires about 300 to 500 degrees, the coil winding There are many of them, making the head heavy.

The head also has an objective lens focal point 1lillt11+.
An actuator consisting of a voice coil, a permanent magnet, and a yoke is provided, which is a factor that increases the weight of the head.

Furthermore, since the signal level of the magneto-optical reproduction signal is low, a preamplifier is installed near the photodetector, but the preamplifier must be placed in an iron shield case, and this shield case also adds weight to the head. It is the cause.

On the other hand, a coaxial cable for recording and reproducing signals and a signal cable for supplying control signals for tracking control and focus control are connected to the magneto-optical head, and when these wirings are connected to the slider, The springiness of the wiring acts as a disturbance, lowering the response and lengthening the settling time. Of course, heads for optical disks also involve the same problems, although there are differences in degree.

(Object of the Invention) The present invention has been made in view of such conventional problems, and provides an optical head device in which the weight of the slider movable part is kept to the necessary minimum and the access time is shortened. The purpose is to

(Summary of the Invention) In order to achieve this object, in the optical head device of the present invention, the slider that moves linearly in the disk radial direction is divided into two parts, a first slider and a second slider, each of which is independently driven by a linear motor. The first slider is equipped with the minimum necessary components for the optical head configuration to perform final tracking control, and the second slider is equipped with the focus control actuator and the main components of the head circuit. The access time is greatly shortened by mounting components and connecting signal lines to the outside to minimize the weight of the first slider.

(Embodiment) FIG. 1 is an explanatory diagram showing an embodiment of the present invention in plan view, FIG. 2 is a cross section taken along the It-It arrow, and FIG. A side view is shown partially in the direction of the arrow.

First, the outline of the device configuration will be explained with reference to Fig. 3.
1 is a base, a voice coil type linear motor 2 is installed on the right side of the base 1, and a moving coil forming a part of the linear motor is installed at one end of a shaft 3 extending from the voice coil type linear motor 2. An MC is attached to the disk 5, and a first slider 4 is provided at the other end so as to be linearly movable in the radial direction R of the disk 5. That is, the first slider 4
is the first rail along the round bar rail 7 installed under the upper frame 6 and the round bar rail 8 installed on the top of the base 1.
The first slider 4 is provided with a groove wheel 9 that guides and moves the slider 4 in the radial direction of the disk 5, and the first slider 4 is mounted with an objective lens 10 and a mirror 11 that constitute a head optical system.

On the other hand, on the outside of the first slider 4, a second slider 12, which will be made clear in the description of FIG. 1.2, is arranged so that it can move linearly in the radial direction of the disk 5 like the first slider 4.

Next, details of the first and second sliders will be explained with reference to FIG. 1.2.

First, from FIG. 1, the structure of the second slider 12 arranged outside the first slider 4 is made clear. That is, the second
The slider 12 is a pair of yokes 1 installed on the base 1.
The second slider 12 can move linearly in the radial direction of the disk by shifting the four ball bearings along the inner corner surface of the second slider 12.
3. It is driven by a linear motor consisting of a magnetic circuit consisting of a permanent magnet 15 and a yoke 16, and a voice coil 17 mounted on the slider side.

Figure 1 also shows a voice coil type linear motor 2 (third
A portion of the first slider 4 mounted on the shaft 3 extending from the shaft 3 (see figure) is shown, and an objective lens 10 mounted on the first slider 4 is equipped with a focus control lens which will be explained later. A movable part of the actuator is provided. Further, a mirror 11 is arranged above the first sura, Ida 4,
A two-split detector 18 and an LED 1 as a light source are installed on both sides.
9 are arranged on the second slider. The beam of the LED 19 reflected by the mirror 11 is irradiated onto the two-split detector 18, and the distance is measured by detecting the difference between the respective outputs of the two-split detector. By measuring this distance, the first slider 4 is caused to control the second slider 12 to follow it.

Furthermore, the first slider 4 includes a semiconductor laser as a light source,
The minimum number of members necessary to construct a magneto-optical head, including optical parts such as a reflecting prism, are mounted.

A head circuit equipped with a preamplifier, etc. that amplifies the reproduction signal from the disk is built into the second slider 12.
These head circuits are built into the shield case 20.

Next, the positional relationship between the first slider 4 and the second slider 12 will be described with reference to FIG. 2 (cross-sectional view taken along If-II in FIG. 1).

First, the first slider 4 has V groove wheels 9 provided above and below that are fitted into a round bar rail 7 fixed to the frame 6 and a round bar rail 8 fixed to the base 1, and is fitted along the round bar rail 7.8. to move linearly in the radial direction of the disk. A box-shaped second slider 12 is disposed outside the first slider 4, and the second slider is supported by a ball bearing 14 at the upper corner 13a of a yoke 13 disposed on both sides, so that it can be rotated in the disk radial direction as well. can move in a straight line. A box-shaped frame 21 whose upper part is made of iron is attached to both sides of the second slider 12, and a voice coil 17 constituting a linear motor is wound around the outside of this box-shaped frame 21 as shown in FIG. Between the box-shaped frame 21 and the yoke 13, the upper iron piece of the box-shaped frame 21 is attracted by the leakage magnetic flux of the magnetic circuit consisting of the permanent magnet 15 and the yoke 16, and is supported by a ball bearing 14.

A permanent magnet 15 and a yoke 16 that form the magnetic circuit of the linear motor are installed outside the box-shaped frame 21, and by energizing the voice coil 17 wound around the box-shaped frame 21, the linear motor is driven and the second slider is moved. 12 in a straight line.

Next, the structure of the seven cutout units for controlling the focus of the objective lens 10 provided on the inner first slider 4 will be explained.

This focus control actuator is the focus coil 22. Permanent magnet 23. York 24. It consists of an electromagnetic coil 25 for external magnetic field, and the focus coil 22 is supported by two parallel springs 26, and the right side of the parallel spring 26 is a first
It is fixed to the slider 4. On the other hand, the permanent magnet 23 and the yoke 24 are provided on the second slider 12 side facing the outside of the focus coil 22, and the external magnetic field electromagnetic coil 25 is also provided on the second slider 1 outside the objective lens 10.
It is installed on the second side.

FIG. 4 shows the focus υj actuator shown in FIG. It supports the coil 22. A permanent magnet 23 and a yoke 24 fixed to the second slider 12 are arranged outside the focus coil 22, and by passing a current through the focus coil 25, the objective lens 10 supported by a parallel spring 26 is moved perpendicularly to the disk 5. I try to drive it in the direction.

Next, to explain the signal line connection between the magneto-optical head and the external circuit, as shown in FIG. A belt-shaped control cable 28 is also connected to the second slider 12 for transmitting various control signals for the focus control actuator shown in FIG. 4 and the linear motor for moving the second slider 12. Further, the signal line connection between the second slider and the first slider to which the coaxial cable 27 and the control cable 28 are connected is made by a flexible print 30, and since the elasticity of the flexible print 30 is extremely small, The signal line connection to the first slider 4 has almost no effect on the responsiveness.

Next, access control of the optical head of the present invention will be explained with reference to the speed diagram of FIG.

First, up to the target position WIA, the voice coil type linear motor 2 for the first slider 4 (see Figure 3) and the linear motor for the second slider 12 (voice coil 17, yoke 13
．． 16 and permanent magnet 15) at the same time. In this independent movement 1/J IIl of the first slider 4 and the second slider 12 by linear motors, as shown in FIG. A linear motor is controlled so as to keep the distance between each slider measured by this deviation measuring device constant, and the second slider 12 is moved from the first slider. 4.

When the first slider 4 and the second slider 12 reach the position A before the target position B by controlling the speeds of the first slider 4 and the second slider 12, the moving speed of the slider is suppressed and the position control toward the target position B is performed. Under this position control, when the first slider 4, which has a small movable weight, reaches the target position B as shown by the solid line 5O in FIG. 5, it vibrates for settling and stops at the target position B after a time t3. On the other hand, the second slider 1 has a large movable weight.
2 reaches the target position B later than the first slider 4, as shown by the broken line 52 in FIG. It then stops at target position B.

That is, in the first embodiment of the present invention, the slider is divided into two parts, the first slider 4 and the second slider 12, and the first slider 4 is equipped with optical elements constituting the magneto-optical system, namely the objective lens 1o Total reflection prism, beam splitter-9 semiconductor laser, collimator lens, beam shaping prism, condensing lens.

Light weight items such as a cylindrical lens, polarizing beam splitter 1, avalanche photodiode for signal reproduction, 4-split PIN photodiode, i.e., a detector for autofocus and autotracking are mounted, and the second slider 1
2 is connected to the permanent magnet 23 and yoke 24 of the focus control actuator, the preamplifier for amplifying the reproduced signal, the coaxial cable, and the control signal cable.
The movable weight of the slider 4 can be significantly reduced, and as a result of this reduction in movable weight, the travel time of the first slider 4 to the target position B and the time required to reach the target position [8] are shown by the solid line 50 in FIG. The subsequent settling time can be significantly shortened.

When the first slider 4 stops at the target position B after time t3, tracking control is started, the difference to the target track is detected based on the track information read from the disk, and the objective lens 10 is moved to track the target track. make it jump When the objective lens 10 is track-jumped in this way, the second slider 12, which has a large movable weight, is in a vibration state for stabilization as shown by the broken line 52 in FIG. 5, but the control of the first slider 4 is 2nd slider 1
2, even if the second slider 12 is in a vibrating state, it does not affect the track jump caused by the objective lens 10 in any way.

In the above embodiment, the permanent magnet 23. in the focus control actuator. The magnetic circuit consisting of the yoke 24 was attached to the second slider 12 side, which has a large movable 1 fil, but since attaching this magnetic circuit to the first slider 4 side does not have much effect on the movable weight, the conventional split structure was replaced. It is possible to realize a sufficiently short access time compared to the case of using a slider with no hold. In addition, when the magnetic circuit of the focus control actuator is provided on the first slider 4 side, in addition to a one-dimensional actuator that drives only in the vertical direction of the disk, a two-dimensional actuator that drives the disk in the axial and lateral directions. can be used.

FIG. 6 is a second embodiment, and is an explanatory diagram showing an optical system used in a write-once disk head device.

In FIG. 6, a first slider 4 that reduces movable weight
The objective lens 10. A semiconductor laser 34 is attached to the second slider 12, which is equipped with a λ/4 plate, 3 sheet metals, 1 light beam splitter 32, and a total reflection prism 33, and does not require consideration of movable weight. Collimator lens 35. Beam shaping prisms 36, 37, condensing lens 389, cylindrical lens 39, and photodetector 40 are attached. In this case, the first slider 4
The light beam between the first slider 4 and the second slider 12
The parallel optical system is configured such that the optical axis does not change due to relative movement between the slider 12 and the second slider 12. By providing a parallel optical system between the first slider 4 and the second slider 12, the distance between the parallel optical systems can be shortened, and the fluctuation thereof can be suppressed. Furthermore, due to the configuration of the parallel optical system, even if there is a positional change between the first slider 4 and the second slider 12, the optical system is not affected by the positional change, which prevents control errors and degraded quality of the reproduced signal. Since this can be reliably prevented and the optical path length can be shortened, stability against temperature changes and stability during long-term use can be ensured. In the write-once optical head device shown in FIG. 6, the polarizing beam splitter 32 provided on the first slider 4 is replaced with a beam splitter, three λ/4 plates and one metal plate are used, and the second slider 12, a semiconductor laser 334 and a collimator lens 35. Beam shaping prism 36.37. In addition to the condenser lens 381, the cylindrical lens 39°, and the photodetector 40, a polarizing beam splitter is inserted and installed in front of the condenser lens 38 by rotating it at a certain angle (for example, 10 degrees) at the optical axis opening with respect to the incident light. , an avalanche photodiode (for detecting reproduced signal) for detecting transmitted light of the polarizing beam splitter, a cylindrical lens and a 4-division PIN photodiode for detecting reflected light and obtaining autofocus and autotracking signals are provided. This is a head device for magneto-optical disks. Since the magneto-optical disk head device according to the second embodiment is mounted on the first slider and has a lighter weight than the one according to the first embodiment, faster access is possible.

(Effects of the Invention) As described above, according to the present invention, the slider of the optical head device is divided into the first slider and the second slider, and the first slider is equipped with only the minimum number of members necessary for the configuration of the optical head. All components that are not mounted on the first slider are mounted on the second slider side, which greatly reduces the movable weight of the first slider. It is possible to shorten the settling time and the settling time after reaching the target position, and to significantly shorten the access time given by the sum of the settling time and track jump time to the target position. High-speed recording and reproduction can be performed.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of the present invention in plan view, Fig. 2 is a sectional view taken along the I-n line in Fig. 1, and Fig. 3 is a partial cross-sectional view of the side surface of Fig. 1. Explanatory diagram, FIG. 4 is an explanatory diagram showing the focus control actuator in FIG. 1.2, FIG. 5 is a velocity diagram of access υJtllll according to the present invention, and FIG. 6 is a head optical system used in the present invention. FIG. 7 is a speed diagram showing access control of a conventional optical head. 1: Base 2: Voice coil type linear motor 3: Shaft 4: First slider 5: Disk 6: Frame 7.8: Round bar rail 9: VIIIl 10: Objective lens 11: Mirror 12: Second slider 13.16. 24: Yoke 14: Ball bearing 15. 23: Permanent magnet 17: Voice coil 18: 2-split detector 19: LED 20: Shield case 21: Box-shaped frame 22: Focus coil 25: 'Fi magnetic coil for external magnetic field 26: Parallel spring 27: Coaxial cable 28 2 Control cable 30: Flexible print 31: λ/4 plate 32: Polarizing beam splitter 33: Total reflection prism 34: Semiconductor laser 35: Collimator lens 36. 37: Beam shaping prism 38 2 condensing lights Lens 39: Cylindrical lens 40: Photodetector

Claims (1)

[Claims] a first slider that moves linearly in the radial direction of the disk; and a second slider that moves linearly in the same direction as the first slider; the first slider is equipped with the minimum number of members necessary for the configuration of the optical head; The second slider is equipped with a focus control actuator and main components of a head circuit, and is connected to an external signal line so that the positions of the first and second slider members can be controlled independently. Optical head device.