JPS6258050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical head used in optical information reading devices and the like.

Optical heads for use in various of the above-mentioned devices have been proposed in the past. The most common optical head has the configuration shown in FIG. That is, in FIG. 1, 1' is a substantially cylindrical focusing lens holder, and a holding frame 2' is mounted on the upper part of the focusing lens holder.
A focusing lens 3' is attached via a focusing lens 3', and a solenoid coil 4' is attached below the focusing lens 3'. 5' is a main body, which has a hollow part 5'a into which the focusing lens holder 1' is vertically movably loosely inserted, and an electromagnetic yoke 6' and an electromagnetic yoke 6' in the lower part of this hollow part 5'a. A magnet 7' is attached to the center of the lens, and a solenoid coil 4' of the focusing lens holder 1' is freely movable vertically in a gap 8' formed by the electromagnetic yoke 6' and magnet 7'. inserted.
The main body 5' is supported on a base 9' by a support member (not shown), and is movable together with the focusing lens holder 1' in parallel to the information disk A'. 1
0' is an elastic thin plate whose peripheral edge portions are fixed to the upper and lower ends of the main body 5 and the focusing lens holder 1', and supports the focusing lens holder 1' in a vertically movable manner.
Reference numeral 11' denotes a mirror that deflects the light beam from the incident optical path 5'b, which is perpendicular to the hollow portion 5'a, toward the focusing lens 3'.
When the diameter of the spot formed by the focusing lens 3' of the light beam on the disk A' changes due to external vibrations, distortion of the disk A', etc., a focus control signal detected by a focus control signal detection device (not shown) changes. A focus adjustment control signal is input to the solenoid coil, and this solenoid coil 4' is energized to move up and down between the gaps 8', so that the focusing lens 3' provided on the focusing lens holder 1' moves up and down. death,
The spot diameter is adjusted appropriately by changing the distance between the information medium A' and the focusing lens 3'.

In this optical head, an electromagnetic yoke 6' and a magnet 7' are provided protruding from the lower end of the hollow part 5'a of the main body 5', and the focusing lens holder 1', the mirror 11', the electromagnetic yoke 6' There is a drawback that the magnets 7' etc. are arranged in a stacked manner, and therefore the entire optical head becomes thick. Also, this optical head is driven in the track access direction to allow the main body 5'
The main body 5' is moved horizontally as appropriate, but the electromagnetic yoke 6', magnet 7', etc., which are the drive devices for focus control described above, also move along with the horizontal movement of the main body 5'.
The weight of the driven body was large and there was a problem with responsiveness.

Therefore, one of the applicants of the present invention proposed an optical head as shown in FIG. 2, which is thinner, lighter, smaller, and faster in response. That is, in Figure 2, 2
0' is a focusing lens, 21' is a mirror, 22' is an elastic body, 23' is a solenoid coil wound around an arm extending laterally from the focusing lens 20', 24' is a focus magnetic device, and 25' is a track. An elastic column supporting the movable part, 26' is an external casing, and 27' is a movable casing for tracking. In addition, the magnetic device for tracking, etc. is the focusing lens 20' in FIG.
It is not shown because it is located behind the etc.

Focus control of the optical head configured as described above is performed by driving the focusing lens 20' in the vertical direction by a focus control mechanism comprising the solenoid coil 23' and the focus magnetic device 24'.

On the other hand, tracking control is carried out by the control current flowing through the movable housing for tracking (not shown) because the focus magnetic device 24' is fixed to the external housing 26' through a hole drilled in the movable housing 27'. , the focus control mechanism excluding the focus magnetic device 24', the mirror 21' and the movable housing 2
This is done by driving 7' perpendicular to the drawing.

Therefore, in the above-mentioned optical head, the focus magnetic device 24' is disposed on the side of the focusing lens 20' and the mirror 21', and is fixed to the external housing 26', so that the optical head mechanism section is The structure can be made thinner and the weight of the track movable section that is driven in the track access direction can be reduced.

However, although the above-mentioned optical head has the above-mentioned advantages, the related structure between each member is complicated and it is difficult to assemble.

SUMMARY OF THE INVENTION In view of the above-mentioned points, it is an object of the present invention to provide an optical head that simplifies the structure related to each member, facilitates assembly, and is thinner.

An embodiment of the present invention will be described below with reference to FIGS. 3 to 5.

Reference numeral 1 designates a substantially cylindrical lens holding tube, on the top of which a focusing lens 3 is provided via a holding frame 2, a solenoid coil 4 is attached to the lower side of the shoulder, and a side hole 1a is provided on the right side of the lower part. It is provided. This lens holding cylinder 1 has an inner wall of a frame with a substantially square cross section provided with a central hole 5a, and upper and lower ends of which are covered with thin plate-like elastic bodies 6, 6a.
It is supported so that it can move up and down. In addition, the frame body 5
A side hole 5b is provided on the right side. A cylindrical electromagnetic yoke 8 is disposed inside the lens holding tube 1, and the lower end of the electromagnetic yoke 8 is connected to a bottom plate 9 made of a magnetic material disposed below the lens holding tube 1 and the frame 5. It is fitted into a hole 9a provided in the hole 9a. On the right side of this electromagnetic yoke 8 is a side hole 8a that communicates with the side hole 1a.
A thin wall portion 1 of a fixing plate 11 for fixing the mirror 10 facing the side hole 8a is provided at the lower end.
A recess 12 is formed for extending 1a outward. The extended portion of the thin wall portion 11a is fixed to the lower end of the frame 5. On the outside of the frame 5 of the bottom plate 9, a magnet 13, an electromagnetic yoke block 14, and a plate-shaped electromagnetic yoke 15 having a concave portion at the tip are stacked and fixed. It extends into the inside of the frame 5 from a through hole 5c provided in the side wall of the frame 5 between the holes 6a, and its tip is formed in a concave shape to match the outer circumferential shape of the solenoid coil 4, and is close to the side of the solenoid coil 4. They are facing each other. Therefore, an electromagnetic body 16 consisting of an electromagnetic yoke 8, a bottom plate 9 made of a magnetic member, a magnet 13, an electromagnetic yoke block 14, and an electromagnetic yoke 15 is arranged from the inside of the lens holding cylinder 1 to the outside of the frame 5. It turns out. Also, on the side wall of the frame 5, a second
A bobbin 18 provided with a solenoid coil 17 is fixed, a protrusion 19a of a T-shaped core 19 is arranged in the hollow part of the bobbin 18, and magnets 2 are attached to both ends of the core 19.
0 and a yoke 21 are stacked and fixed so as to face the second solenoid coil 17.
The core 19 is fixed to an outer frame 22a that constitutes an outer case 22. This electromagnetic device 23 acts to move the entire frame body 5 laterally, and the frame body 5 has an elastic column body erected from a part of the upper cover 22b of the outer case 22 and the upper surface of the bottom plate 9. The upper part of 24 is fixed, and the frame 5 can be moved laterally.

The operation of the embodiment having the above configuration will be explained.

A light beam B emitted from a light source (not shown) passes through the side holes 5b, 1a, and 8a, reaches the mirror 10, is deflected by the mirror 10 toward the focusing lens 3, and is focused by the focusing lens 3 onto the information disk A at a beam spot 25. It is focused as This beam spot 2
As is well known, the reflected beam after irradiating the information disk A is irradiated onto a light-receiving element, and optical changes in the reflected beam on the light-receiving element are sensed and recorded on the information disk A. At the same time, the beam spot 5
A focus control signal and a tracking control signal corresponding to a change in the spot diameter of the beam spot 25 and a positional deviation of the beam spot 25 with respect to the information track are obtained.

The focus control signal is input to the solenoid coil 4, and the lens holding cylinder 1 is moved up and down against the elastic bodies 6, 6a by the excitation effect with the electromagnetic body 16, and the beam spot 25 is directed toward the information disk A. It acts to keep the spot diameter constant. Further, the tracking control signal
It is input to the solenoid coil 17, and by the excitation effect with the electromagnetic device 23, the frame body 5 is moved laterally against the elasticity of the elastic column body 24, and the relative position of the beam spot 25 with respect to the information track is determined. Control appropriately.

When the frame body 5 is moved, the electromagnetic body 16 is arranged inside the lens holding cylinder 1 and outside the frame body independently of the frame body, so the thickness of the entire device can be reduced, and the electromagnetic body 16 is subtracted from the weight of the frame 5 compared to the conventional device shown in FIG. 1, the frame 5 is lighter, the burden on the electromagnetic device 23 is reduced, and the control response is improved.

Further, when assembling the optical head, the lens holding cylinder 1 is attached to the frame 5 via the elastic bodies 6, 6a.
is supported, and the inside of the lens holding cylinder 1 of this frame 5 is inserted into the electromagnetic yoke 8 fitted on the bottom plate 9.
Thereafter, the tip of the electromagnetic yoke 15 can be inserted into the frame 5 through the through hole 5c, and the magnet 13 can be fixed to the bottom plate 9. The electromagnetic yoke 8, the bottom plate 9, the magnet 13, and the electromagnetic yoke block 1 constituting the electromagnetic device 16 for focus control can be assembled into a unit for easy handling.
4. Since the electromagnetic yoke 15 can be installed, assembly and assembly accuracy are improved.

Because of the above-described configuration, the present invention allows the optical head to be made thinner, and the movable track section that drives in the track access direction to be lighter in weight.Moreover, the related structure between the constituent members is simple, and assembly is possible. Furthermore, since the tip of the electromagnetic yoke is formed in a concave shape to match the outer circumferential shape of the solenoid coil, the electromagnetic yoke and the solenoid coil can be brought close to each other, and focus control can be performed effectively.

[Brief explanation of the drawing]

1 and 2 are sectional views showing a conventional example, FIG. 3 is a sectional view showing an embodiment of the present invention, FIG. 4 is a partial sectional view of the side of the same embodiment, and FIG. FIG. 3 is an exploded perspective view showing main parts of an example. A...Information disk, B...Light beam, 1...
Lens holding tube, 3... Focusing lens, 4... Solenoid coil, 5... Frame, 5c... Through hole, 6,
6a...Elastic body, 13...Magnet, 15...Electromagnetic yoke, 16...Electromagnetic body, 23...Electromagnetic device.

Claims (1)

[Claims] 1. Elastic bodies 6, Frame 5 at 6a
An electromagnetic device 23 is provided so that the frame 5 is movable in a track access direction parallel to the information disk surface A, and a magnet 13 and an electromagnetic yoke extend from the inside of the lens holding cylinder 1 to the outside of the frame 5. 15
A part of the electromagnetic yoke 15 is connected to the frame 5 between the elastic bodies 6 and 6a.
The electromagnetic yoke 15 extends into the inside of the frame 5 from a through hole 5c provided in the side wall, and the tip of the electromagnetic yoke 15 is formed into a concave shape to match the outer circumferential shape of the solenoid coil 4 provided in the lens holding cylinder 1. An optical head that faces the coil 4.