JPS609938Y2 - optical information reproducing device - Google Patents

Description

[Detailed description of the invention] This invention relates to an optical information reproducing device, particularly an optical information reproducing device having a position control system for controlling the relative position between a recording medium and a recording/reading section with extremely high accuracy. .

Generally, magnetic tape is the most widely used recording medium for recording video, audio, etc., but this is because magnetic tape is relatively easy to record and play back, and it has a large recording capacity. It is.

However, recently, records using an optical reproduction system have started to attract attention as a recording medium that has several times the recording capacity of magnetic tape and is also cheaper.

Normally, a record is played by touching the stylus to the record, but this classical music playback method attempts to read information by irradiating the record with laser light without directly touching it.

Therefore, recorded information can be maintained semi-permanently, and high-density, high-quality information can be recorded and reproduced.

Furthermore, vinyl records have many advantages, such as being the same size as ordinary audio records and being manufactured using the same pressing method, which is why they are seen as promising as a new recording medium that surpasses magnetic tape.

FIG. 1 is an explanatory diagram showing an example of an optical information reproducing apparatus for reproducing this type of record.

In the figure, 1 is a disc-shaped record that is driven by a motor 2 and rotates at a predetermined rotational speed, and the second
As shown in the figure, there is a transparent disk part 1b in which concave and convex pits) la on which information is encoded are engraved in a spiral or concentric form, and a reflective metal film IC attached to the surface side on which the concave and convex pits la are engraved. , and a protective film 1d that protects the reflective metal film IC.

Reference numeral 3 denotes a laser device that sends a laser beam 4 to a recording/reading section 7 via a first splitter 5 consisting of a pair of triangular prisms and a total reflection mirror 6.

The recording/reading section 7 has one lens 7a, and scans the record 1 in the radial direction while focusing the laser beam 4 on a predetermined position on the record 1.

Here, the laser beam 4 is modulated and reflected by the uneven bit 1a of the record 1, and the reflected light 8 passes through the total reflection mirror 6 and the first splitter 5 again, and then passes through the second splitter 9 made of three triangular prisms. The reflected light 8 is split into three components 8at and 8bt by the second splitter 9.
It is divided into 8c.

Further, each component of the reflected light 8 is converted into an electrical signal by an optical converter 10.

11 are components 8a and 8b at both ends of the reflected light 8;
This is a first amplifier that extracts a difference signal between electric signals corresponding to each of the two amplifiers and sends an output signal to a position control device that performs focus adjustment for radial deviation in the recording/reading section 7, and this first amplifier The device 11 has a motional feedback circuit 12 from the position controller.

Reference numeral 13 compares the electrical signal corresponding to 8C, which is the central component of the reflected light 8, with a predetermined reference value, and outputs an output corresponding to the deviation to adjust the focus for the vertical deviation of the recording/reading section 7. The motional feedback circuit 14 is a second amplifier that sends the signal to the position control device for performing smooth position control, similar to the first amplifier 11 described above.
have.

15 is an output terminal from which a component 8C containing information of the reflected light 8 is derived.

However, a relatively problematic aspect of such an optical reproducing device is that the laser beam must be scanned while always focusing the laser beam on a predetermined position on the record.

In other words, since it is completely non-contact, focusing and tracking are complicated, and a highly accurate position control mechanism is required.In particular, it is necessary to detect and correct deviations in the focal position due to vibration or deflection of the record. becomes an essential condition.

However, in conventional optical information reproducing devices, normal position control such as focusing or tracking is determined simply by the focus control signal obtained from the reflected light component, and by the small mass of the lenses and other components that make up the optical system. Since the attempt was to deal with both overshoot and dynamic characteristic compensation control such as vibration at the same time, it was difficult to provide optimal operating characteristics (control constants, response speed, etc.) to each of the above-mentioned controls, and as a result, Both of the above-mentioned controls are either unsatisfactory, or the two control operations interfere with each other, resulting in increased instability as a whole.

Therefore, this idea was made in view of the above points,
The normal position control and the dynamic characteristic compensation control are substantially divided into two,
An optical information reproducing device is provided that has a position control system that can provide optimal control operation characteristics for each control, perform extremely accurate and smooth position control as a whole, and has a simple configuration. It is to provide.

In order to achieve such an object, this invention provides an optical information reproducing apparatus having a position control system for controlling the relative position between a recording medium and a recording/reading section, in which the recording/reading section is provided with an information reproducing section at one end. an optical system consisting of a cylindrical body in which a lens is held, a driving coil is wound around the other end, and a magnetically sensitive element is provided near the driving coil; and an optical system having an optical through hole in the center; An envelope that surrounds the cylindrical body, a support that elastically supports the cylindrical body so as to be movable in one direction with respect to the envelope, and a magnetic circuit that supplies a cross magnetic field in a fixed direction to the drive coil are integrated. The position control system receives as input both the reflected optical signal component and the cylindrical position change component respectively obtained from the optical system and the magnetically sensitive element of the optical pickup, and controls the optical pickup. It also includes an amplifier that controls the position of the lens by supplying an output current to the coil of the pickup, and controls the current supplied to the drive coil of the optical pickup based on the reflected light signal component to control the position of the optical system. The dynamic characteristics of the optical system are stabilized by main controlling the position and performing auxiliary control by motion feedback to the main control system of the coil based on the output of the magnetically sensitive element. be.

The optical information reproducing apparatus according to this invention will be explained in detail below with reference to the drawings.

FIG. 3 is a sectional view of an optical pickup portion as a recording/reading section showing an embodiment of a position control device which is a main part of an optical information reproducing apparatus according to this invention.

In the same figure, 16 is an envelope having a hollow chamber 17 inside and forming a magnetic path a, and 18 is this envelope 16.
It is a cylindrical permanent magnet that is magnetically connected and attached to the bottom of the hollow chamber 17, and has a through hole 19 connected to the envelope 16 at its axis, and a tip with a small diameter. is formed.

Here, the envelope 16, the permanent magnets 1 and 8, etc. form a fixed member.

A constant magnetic field perpendicular to the opposing surface is formed in the gap between the small diameter portion 18a of the permanent magnet 18 and the protrusion 16a provided near the center of the envelope 16.

Reference numerals 20 and 21 designate elastic bellows disc-shaped dampers whose outer edges are respectively fixed to stepped portions 16b and 16c provided at two locations of the envelope 16 at a predetermined interval; 22, these dampers 20; .21 is a cylindrical lens holder that is fixed to the respective edges 20a and 21a, and this lens holder 22 is thereby attached to the envelope 16.
It is held movably against the

A lens 23 is fixed to the tip of this lens holder 22 via a holding annular body 22a, and the holding annular body 22
a, and the two dampers 2
It has a cylindrical body 22b made of a magnetic material fixed to 0.21 mm, and the rear end of this cylindrical body 22b is connected to the protrusion 1 of the envelope 16.
6a and the small diameter portion 18a of the permanent magnet 18, and the magnetic fields intersect at right angles.

Reference numeral 24 denotes a drive coil wound around the outer wall of the cylindrical body 22b located in a constant magnetic field, and 25 denotes a motion feedback coil wound around the outer wall of the cylindrical body 22b in parallel with the drive coil 24.

In the position control device configured in this way, by driving the drive coil 24 wound around the cylindrical body 22b of the lens holder 22, the lens is held by the interaction between the drive coil 24 and a constant magnetic field. The body 22 moves in the axial direction, that is, in the direction of the arrow, in accordance with the drive signal.

Here, the drive signal applied to the drive coil 24 is sent out from the second amplifier 13 based on the reflected light component obtained from the optical system as described in FIG. The voltage etc. correspond to the vertical focal position shift that is constantly detected.

The above configuration forms a main control system for the position of the optical system.

However, when the lens holder 22 moves in the direction and distance corresponding to the drive signal, the lens holder 22 has dynamic characteristics that are determined based on the mass of the lens, etc., such as overshoot and vibration. , it is difficult to correct according to the control of the main control system.

If you try to correct this irregularity in dynamic characteristics using only the main control system, the main control system will be forced to perform more control than necessary.
As a result, the main control system becomes complicated or the main control system itself becomes unstable.

The motional feedback coil 25 is provided as a countermeasure against this problem.

This has an independent detection system separate from the main control system, forming an auxiliary control system that supplements the control contents of the main control system, and this motion feedback coil 25 is connected to the lens holder 22. It generates an electrical signal that accurately corresponds to the movement of the lens holder, and sends this output to the drive coil 24.
The signal is fed back to the second amplifier 13, which is a drive control system.

As a result, independent auxiliary control is performed only for overshoots and vibrations that deviate from the control content of the main control system, reducing the burden on the main control system, and A highly accurate position control system with extremely stable dynamic characteristics is used, and the correction of the lens holder 22 is performed accurately, quickly and smoothly.

The laser beam passes through the lens holder 22 through the through hole 19 passing through the envelope 16 and the permanent magnet 18, reaches the lens 23, and the lens 23 reaches the lens 23.
3 focuses on a predetermined position in front.

Correction is performed by changing the focal position in the vertical direction as the lens holder 22 moves.

As described above, according to the position control device according to this embodiment, the lens holder around which the drive coil and the motion feedback coil are wound is movably arranged in a constant magnetic field via two dampers, and Since the lens holder has a through hole that serves as an optical path, if a main control drive signal corresponding to the shift in the focal position is applied to the drive coil, the lens holder will be forced by the interaction with the magnetic field. receive and move.

Along with this, the distance between the lens and the code disk changes, and the focal position is corrected.

Furthermore, since the movement of the lens holder is converted into an electrical signal by motion feedback and detected, this detection result is fed back to the drive coil control system as an auxiliary control signal, allowing the lens holder to be deflected with extremely high precision. It is done well, quickly and smoothly.

In addition, in this embodiment, a case has been described in which a coil is used as a means for detecting the movement of the lens holder, but this invention is not limited to this, and other magnetic sensing elements such as a Hall element can be used. It is clear that the same effect can be obtained even if a magnetoresistive element or the like is attached to the lens holder and placed in the magnetic field.

Furthermore, although this embodiment shows a structure in which the lens holder is supported by two dampers, it is also possible to support it by one or two or more dampers, and the shape of the damper may be a bellows disk. It is not limited to the following.

Further, the drive coil does not always need to be wound around a magnetic cylinder, and it is of course possible to use the tightly wound solenoid coil itself as the cylinder forming the lens holder.

As explained above, the optical information reproducing device according to this invention has an information reproducing lens held at one end, a drive coil wound around the other end, and a magnetically sensitive element provided near the drive coil. an optical system consisting of a cylindrical body; an envelope having an optical through hole in the center and surrounding the optical system; and a support that elastically supports the cylindrical body so as to be movable in one direction with respect to the envelope. and a magnetic circuit that supplies a cross magnetic field in a fixed direction to the drive coil 1, and mainly controls the reflected optical signal component obtained from the optical system of this optical pickup. The position change component obtained from the magnetically sensitive element is detected as an auxiliary control signal, and the current supplied to the coil is controlled based on the reflected light component obtained from the optical system to change the position of the optical system. In addition to performing main control, the dynamic characteristics of the optical system are stabilized by performing auxiliary control by motion feedback on the main control system of the coil based on the output of the magnetically sensitive element. In addition, the auxiliary control system installed in parallel with the main control system corrects control deviations that occur due to vibrations and deflections of information recording media such as records and cannot be corrected by the main control system for the position of the optical system. can be complemented very accurately by the system.

As a result, the main control system only needs to perform complex focusing or tracking control for loads that are equivalently free of irregularities in dynamic characteristics, such as overshoots or vibrations, which puts a burden on the main control system. In addition, the operating characteristics of the main control system or auxiliary control system can be set to those optimal for the control operations assigned to each, and although the configuration of each can be relatively simple, the position control as a whole can be improved. This has the effect of being extremely accurate and allowing smooth correction.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of an optical information reproducing device, and FIG.
The figure is a sectional view of the essential parts of an example of a record disc used in the optical information reproducing apparatus shown in Fig. 1, and Fig. 3 is an implementation of the position control device which is the essential part of the optical information reproducing apparatus according to this invention. FIG. 3 is a cross-sectional view of an optical pickup portion as a recording/reading section showing an example. 1... Record disc, 2111+11@Ill motor, 3... Laser device, 7... Recording/reading unit, 10... Optical converter, 11, 13・・・
...Amplifier, 16...Envelope, 18...
...Permanent magnet, 19...Through hole, 20.21
... Damper, 22 ... Lens holder, 23 ... Lens, 24 ... Drive coil, 25 - Song/motional feedback coil.

Claims (1)

[Claims for Utility Model Registration] In an optical information reproducing device having a position control system for controlling the relative position between a recording medium and a recording/reading section, an information reproducing lens is held at one end as the recording/reading section, an optical system consisting of a cylinder around which a drive coil is wound around the other end and a magnetically sensitive element provided near the drive coil; and an envelope surrounding the optical system and having an optical through hole in the center. and a support body that elastically supports the cylindrical body so as to be movable in one direction with respect to the envelope, and a magnetic circuit that supplies a cross magnetic field in a certain direction to the drive coil. An optical pickup is provided, and the position control system inputs both the reflected optical signal component and the cylindrical position change component obtained from the optical system and the magnetically sensitive element of the optical pickup, and outputs it to the coil of the optical pickup. an amplifier that supplies current to control the position of the lens, and controls the current supplied to the drive coil of the optical pickup based on the reflected light signal component to main control the position of the optical system; . An optical information reproducing apparatus, characterized in that auxiliary control is performed by motional feedback on the main control system of the coil based on the output of the magnetically sensitive element.