JPH10198986A - Optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent springs supporting a lens folder from being deformed by an excessive force added to the lens holder holding an objective lens by a fall impact, etc. SOLUTION: Stopper projections 20, 21 limiting an excessive downward movement of a lens holder 8 are provided at the center of gravity or in the neighborhood of the lens holder 8. Thus, when an excessive force is given to the device by a fall impact, etc., since the upward force is obstructed by a cover, while the downward force is obstructed by the stopper projections 20 and 21 abutting on the upper face of a yoke 12 located in the lower part thereof, springs 14, 15 are prevented from being excessively deformed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head used for a CD device, an MD device, a DVD device, etc. using an optical disk as a recording medium.

[0002]

2. Description of the Related Art Conventionally, this type of optical head focuses a light beam emitted from a semiconductor laser on an optical disk surface by an objective lens, and reads pit information formed on the disk surface from the reflected light beam. It is configured. In order to accurately read the pit information, two-axis control of focusing control for moving the objective lens in the direction of the optical axis and tracking control for moving the objective lens at right angles to the optical axis toward the center of the optical disk must be performed. In order to enable minute control for the optical head, it is required to reduce the weight and thickness of the optical head.

FIG. 4 is a schematic plan view showing an example of a conventional optical head, FIG. 5 is a schematic sectional front view thereof, and FIG. 6 is a schematic sectional side view thereof. In these figures, reference numeral 1 denotes a resin base, and a rack 2 and a guide hole 3 are provided on one side.
Are formed, and are engaged with a pinion and a guide rod of a driving device (not shown) to move the entire optical head in the tracking B direction. In the base 1, a hollow lens barrel 4 is formed along a focusing A direction perpendicular to the tracking B direction, and a semiconductor that emits a laser beam under a partition wall 4b having a through hole 4a below the hollow lens barrel 4. A laser 5 is mounted via a mounting bracket 6.
An objective lens 7 is mounted on a lens holder 8
And is disposed so as to face the lens barrel 4. The lens holder 8 is provided with two arms 8a and 8b on the side of a lens holding portion that holds the objective lens 7, and a bobbin 9 is fixed between them. This bobbin 9
The focusing coil 10 is wound around
Two tracking coils 11 are attached. 2
Between the arms 8a and 8b, a pair of rising pieces 12a and 12b of a yoke 12 fixed to the upper surface of the base 1 and forming a magnetic circuit are connected to the focusing coil 10a.
A magnet 13 is fixed to one rising piece 12 a passing through the bobbin 9 so as to cross the magnetic path of the tracking coil 11. The arms 8a and 8b each have one mounting portion of two springs 14 and 15 formed by punching an extremely thin leaf spring, and the other mounting portion of the springs 14 and 15 is made of resin. Are fixed to both sides of the support base 16. The support 16 is fixed to the upper surface of the base 1, and the lens holder 8 has two springs 14, 15 on the support 16.
Is supported in a cantilevered state. The entire optical head is covered by a cover 17, and an opening 18 is provided in the cover 17. Through this opening 18, a light beam from the semiconductor laser 5 is applied to the optical disk 19 via the objective lens 7. It has become.

In the above configuration, when a control current is supplied to the focusing coil 10, the current in the tracking B direction flowing through the focusing coil 10 and the magnetic flux from the magnet 13 constituting the magnetic circuit cause the objective lens 7 to move in the focusing A direction. A force is generated to move the object. This force moves the lens holder 8 supported by the support base 16 via the springs 14 and 15 in the focusing A direction, whereby the focusing adjustment of the objective lens 7 is performed. When a control current is supplied to the tracking coil 11, a force for moving the objective lens 7 in the tracking B direction is generated by the current in the focusing A direction flowing through the tracking coil 11 and the magnetic flux from the magnet 13. This force applies the spring 1 to the support 16.
By moving the lens holder 8 supported via 4 and 15 in the tracking B direction, the tracking adjustment of the objective lens 7 is performed. The objective lens 7 receives the laser beam emitted from the semiconductor laser 5 while receiving such focusing adjustment and tracking adjustment.
The information recorded on the optical disk 19 is collected by condensing the light on a pit array formed on the optical disk 19, receiving the reflected light beam from the pit array again with the semiconductor laser 5, and detecting a change in the terminal voltage of the semiconductor laser 5. Is playing.

[0005]

In such an optical head, the apparatus may be hit at the time of transportation, or may be dropped if the apparatus is of a portable type. In such a case, the lens holder 8 is held in a cantilever state by the extremely thin springs 14 and 15 in a cantilever state.
, The springs 14 and 15 may be subjected to excessive force and deform beyond the elastic limit. If the springs 14 and 15 are deformed, the above-described focusing adjustment and tracking adjustment cannot be performed accurately. In order to prevent such deformation of the springs 14 and 15, it is conceivable to increase the spring constant of the spring. However, in this case, a large amount of energy is required to drive the lens holder 8 in the focusing direction and the tracking direction. This is not practical for an optical head that requires a small size and light weight.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an optical head capable of preventing deformation of a spring due to a drop impact or the like.

[0007]

According to the present invention, in order to achieve the above object, a stopper projection is provided at or near the center of gravity of a lens holder to limit excessive downward movement of the lens holder. . As a result, even if an excessive force is applied to the apparatus due to a drop impact or the like, the stopper projection provided at or near the center of gravity of the lens holder hits the lower member and is prevented from moving further. Can be prevented from being deformed.

[0008]

FIG. 1 is a block diagram showing an embodiment of the present invention.
3 will be described with reference to FIG. FIG. 1 is a schematic plan view of an optical head according to the present embodiment, FIG. 2 is a schematic sectional front view thereof, and FIG. 3 is a schematic sectional side view thereof. The optical head according to the present embodiment has the same configuration as the conventional optical head shown in FIGS. 4 to 6 except that a stopper projection is provided. Elements are similarly numbered. 1, 2 and 3, the stopper projections 20 and 21 pass through the center of gravity G of the lens holder 8, in a direction perpendicular to the direction parallel to the springs 14 and 15 (tracking B direction), or with the objective lens 7. It is provided below the arms 8a and 8b of the lens holder 8 in a direction perpendicular to a straight line connecting the center of the support 16 and at symmetrical positions on both sides of the center of gravity G. Further, the distance from the lower end surfaces of the stopper projections 20 and 21 to the upper surface of the yoke 12 thereunder is set to be slightly larger than the maximum downward adjustment distance in the focusing adjustment, so as not to hinder the focusing adjustment. By providing the stopper projections 20 and 21 at such positions, when an excessive force is applied to the apparatus due to a drop impact or the like, an upward force is blocked by the cover 17, and a downward force is applied to the stopper projections 20 and 21. Since the abutment 21 contacts the upper surface of the lower yoke 12, further movement is prevented, and it is possible to prevent the springs 14 and 15 from being deformed due to excessive force.

When an external force is applied to the apparatus due to a drop impact or the like, a moment acts on the lens holder 8 supported in a cantilever state by the springs 14 and 15 on the support base 16, but the stopper projections 20 and 21 By hitting the lower yoke 12, this becomes a second fulcrum. At this time, in the present embodiment, since the stopper projections 20 and 21 are provided at positions passing through the center of gravity G of the lens holder 8 and symmetrically with respect to the center of gravity G, the stopper projections serving as second fulcrums There is no moment generated around the centers 20 and 21 due to the center of gravity of the lens holder 8, and the lens holder 8 stops without tilting. On the other hand, when the stopper projections 20 and 21 are not at positions passing through the center of gravity G, a moment due to the center of gravity G of the lens holder 8 is generated around the stopper projections 20 and 21 serving as the second fulcrum, and the lens holder 8 will tilt, causing excessive deformation of the springs 14,15.

In the above embodiment, two stopper projections 20 and 21 are provided at symmetrical positions on both sides passing through the center of gravity G of the lens holder 8, but depending on the shape of the lens holder, the position of the center of gravity or the position of the center of gravity may be determined. Only one can be provided in the vicinity.

[0011]

As described above, according to the present invention, the stopper projection for limiting excessive downward movement of the lens holder is provided at or near the center of gravity of the lens holder. Even if external force is applied,
Since the stopper projection provided at or near the center of gravity of the lens holder hits the lower member and stops,
Excessive deformation of the spring can be prevented, and the performance of the optical head can be favorably maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of an optical head showing an embodiment of the present invention.

FIG. 2 is a schematic sectional front view of the optical head according to the embodiment.

FIG. 3 is a schematic cross-sectional side view of the optical head according to the embodiment.

FIG. 4 is a schematic plan view showing an example of a conventional optical head.

FIG. 5 is a schematic sectional front view of a conventional optical head.

FIG. 6 is a schematic cross-sectional side view of a conventional optical head.

[Explanation of symbols]

 Reference Signs List 1 base 2 rack 3 guide hole 4 lens barrel 5 semiconductor laser 6 mounting bracket 7 objective lens 8 lens holder 9 bobbin 10 focusing coil 11 tracking coil 12 yoke 13 magnet 14, 15 spring 16 support base 17 cover 18 opening 19 optical disk 20 , 21 stopper projection

Claims (2)

[Claims] 1. A lens holder holding an objective lens, a support for supporting the lens holder in a cantilever state via a spring, and a lens barrel for fixing the support and facing the objective lens. In an optical head including a base and a semiconductor laser attached to an end of the lens barrel opposite to the objective lens, an excessive downward movement of the lens holder at or near the center of gravity of the lens holder. An optical head with a stopper projection that restricts movement. 2. The optical head according to claim 1, wherein the stopper projections are provided at symmetrical positions on both sides of the center of gravity in a direction passing through the center of gravity of the lens holder and perpendicular to a direction parallel to a spring supporting the lens holder.