JPH05166210A - Optical head - Google Patents

Abstract

PURPOSE:To facilitate the production of a holder and the position adjustment of a light emitting element and to prevent the weight balance of the holder from being impaired by detecting the light from the light emitting element by a light receiving element fixed to a base, thereby detecting the position of the objective lens. CONSTITUTION:The light emitting element 35 is fitted to a balancer 31 attached to the objective lens holder 21 which holds the objective lens 23 and controls tracking and focusing by turning and sliding the lens with a holder supporting shaft 15. The light receiving element 37 is fixed to the base 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for irradiating an optical recording medium such as an optical disk or a magneto-optical disk with a light spot to optically read and write information.
Specifically, it relates to a position detecting mechanism of an objective lens in an optical head.

[0002]

2. Description of the Related Art When recording / reproducing an optical recording medium, it is necessary to accurately irradiate a target recording track with a light spot. Also, the loading error of the recording disc,
It is inevitable that the spot irradiation position is displaced in the tracking direction and the focusing direction due to rotational eccentricity, surface wobbling, and the like. Therefore, it is necessary to detect the positional deviation amount as an error signal and control the spot irradiation position by the objective lens actuator at the same time when the information is reproduced and recorded.

Therefore, in a conventional optical recording (including magneto-optical recording) apparatus, an objective lens actuator is generally mounted on an optical head. The objective lens actuator includes an objective lens holder having an objective lens mounted thereon and an actuator mechanism capable of driving the holder with respect to the optical head.

In reproducing and recording information, in general, the optical head is driven at high-speed coarse access to move the objective lens to a target recording track, and then the focusing coil and the tracking coil are used to move an optical signal by an objective lens actuator. Finely control the irradiation position of the spot.

Since acceleration is applied to the objective lens holder at the time of high speed driving, the objective lens holder is likely to vibrate, and if this vibration occurs, it takes time for the fine control to rise. Therefore, it is conceivable to detect and hold / control the position of the objective lens so that the objective lens holder (that is, the objective lens) is always positioned at the neutral point during high-speed driving.

Further, since the drive control range of the objective lens actuator in the tracking direction and the focusing direction is narrow, the fine control mechanism operates promptly unless the objective lens is located near the neutral point during the fine control drive of the objective lens actuator. do not do. Therefore, it may be necessary to detect the position of the objective lens and brake to the neutral point.

In addition, it is important and often performed to detect the position of the objective lens in the focus direction and control it when the apparatus is started.

As a conventional method for detecting the position of such an objective lens, the objective lens holder is held by a leaf spring so as to be movable in the focusing direction, and a support member for supporting the leaf spring is made rotatable and is supported. There is known an optical pickup device in which a light emitting element is fixed to a member and a light receiving element is provided on a stationary member facing the light emitting element.

However, with this device, it is difficult to adjust the positions of the light emitting element and the light receiving element during assembly. Further, only the position of the objective lens in the tracking direction can be detected, and further, if the leaf spring holding the objective lens holder is deformed or twisted, the position of the objective lens in the tracking direction cannot be accurately detected.

It is also known to detect the position of the objective lens by providing a reflecting plate on the side surface of the objective lens holder and providing a light source and a light receiving element on a stationary member.
However, in this method, the holder must be provided with a flat portion necessary for fixing the reflection plate, and by fixing the reflection plate, the weight of the movable portion (including the holder and the objective lens) of the objective lens actuator is balanced. It becomes difficult to induce the above vibration.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a position detecting mechanism for an objective lens in an optical head which does not complicate the device and which is easily adjusted during assembly.

[0012]

The optical head of the present invention comprises:
In an optical head in which an objective lens holder equipped with an objective lens is fitted so as to be rotatable and slidable with respect to a holder support shaft and the objective lens is driven in a focusing direction and a tracking direction, the objective lens holder with respect to the holder support shaft is A light receiving element for fixing a light source to a balancer attached to an objective lens holder for weight balance, and for detecting an irradiation position of light from the light source on an immovable portion which is immovable with respect to a holder supporting shaft. Is provided.

[0013]

1 is a top view showing an embodiment of an optical head of the present invention, and FIG. 2 is a longitudinal sectional view taken along the line A--A.

FIG. 3 is a partially enlarged sectional view (corresponding to FIG. 2) near the fixing portion of the light emitting element 35, and FIG. 4 is a partially enlarged exploded perspective view of the same.

An actuator base 13 is fixed to the optical head base 11, and the actuator base 13 is fixed.
A holder support shaft 15 is fixed to the. On the holder support shaft 15, the objective lens holder 21 is slidable vertically with respect to the holder support shaft 15 via the bearing 29, and
It is fitted around the holder support shaft 15 so as to be rotatable.
An objective lens 23 is mounted on the objective lens holder 21 at a position eccentric with respect to the holder support shaft 15, and is rotated by the objective lens holder 21 to be converged by the objective lens 23 to form an image on a recording disk 55. The spot irradiation position of the luminous flux 51 that moves moves in the tracking direction Tr.

A focusing coil 25 is wound around the outer peripheral surface of the peripheral wall portion of the objective lens holder 21. A yoke member 4 including an inner yoke 43b and an outer yoke 43a.
A magnetic device including the magnet 3 and the magnet 41 is fixed to the actuator base 13. The magnetic flux from this magnetic device forms a linear motor across the focusing coil 25. By passing a signal current through the focusing coil 25, the objective lens holder 21 slides up and down along the holder support shaft 15 to focus. Control is made.

Further, four wound tracking coils 27 are fixed to the outer peripheral surface of the peripheral wall portion of the objective lens holder 21. The magnetic flux from the above-mentioned magnetic device intersects with one winding portion of the tracking coil 27 running in the vertical direction to form a rotary motor.
By passing a signal current through the objective lens holder 21, the objective lens holder 21 rotates about the holder support shaft 15 and tracking control is performed. Luminous flux 5 from laser diode (not shown)
1 is a reflection mirror 5 fixed to the optical head base 11.
Reflected by 3 and started up, actuator base 13
After passing through the opening, the light enters the objective lens 23, is converged, and is spot-irradiated on the recording disk 55.

At this time, as described above, in order to perform tracking control, it is necessary that the objective lens 23 be held at a position eccentric with respect to the holder supporting shaft 15, so that the holder supporting shaft 15 is centered. Objective lens holder 2
It is unavoidable that the weight balance of 1 is lost. Therefore, in the shaft-sliding type objective lens actuator shown in FIGS. 1 and 2, the balancer 31 is mounted on the objective lens holder 21 at a position symmetrical to the objective lens 23 with respect to the holder support shaft 15, and the weight balance is achieved. Is taking As described above, the balancer 31 is an essential component in a shaft sliding type objective lens actuator, and its installation position is also strictly determined in the actuator design stage.

In the embodiment shown in FIGS. 1 to 4, a light emitting element 35 (light source) such as an LED is attached to the vertical portion 31a of the balancer 31 (the portion protruding from the lower end of the objective lens holder 21). There is. In the balancer vertical portion 31a, the holder support shaft 15 side is cut off to remove the light source fixing surface 3
1b is formed, and the light emitting element 35 is fixed thereto. An aperture 33 is formed in the light source fixing surface 31b as a through hole for narrowing the light from the light source.

On the other hand, the actuator base 13 has 4
A light receiving element 37 such as a split photodiode is attached, and the light from the light emitting element 35 is focused by the aperture 33 and enters the light receiving element 37. Based on the light incident position on the light receiving element 37, it is possible to detect the amount of positional deviation from the reference point (neutral point) of the objective lens holder 21 on which the balancer 31 is mounted, that is, the objective lens 23, in the tracking direction and / or the focusing direction. .. It should be noted that the light receiving element 37 may be fixed to any portion that is immovable with respect to the holder support shaft 15 serving as a drive reference of the objective lens 23, and may be directly fixed to the optical head base 11, for example.

[0021]

According to the present invention, the light source is fixed to the balancer attached to the objective lens holder of the shaft sliding type actuator, and the light from this light source is attached to the immovable portion immovable with respect to the holder supporting shaft. The position of the objective lens can be detected by detecting with the light receiving element.

At this time, since the objective lens holder does not require special processing such as a light source fixing surface, the holder can be easily manufactured and the weight balance of the holder is not impaired. Further, the entire optical head can be made smaller and thinner.

In designing the objective lens holder,
Since the position of the balancer has already been specified to balance the weight, by fixing the light source to this balancer, the position of the light source and the light receiving element can be adjusted almost automatically.
Easy adjustment during assembly.

[Brief description of drawings]

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

2 is a vertical cross-sectional view taken along the line AA of FIG.

FIG. 3 is a partially enlarged cross-sectional view showing the vicinity of a balancer vertical portion 31a.

FIG. 4 is a partially enlarged exploded perspective view showing the vicinity of the balancer hanging portion 31a.

[Explanation of symbols]

 11 Optical Head Base 13 Actuator Base 15 Holder Support Axis 21 Objective Lens Holder 23 Objective Lens 25 Focusing Coil 27 Tracking Coil 29 Bearing 31 Balancer 31a Balancer Vertically 31b Light Source Fixing Surface 33 Aperture 35 Light-Emitting Element 37 Light-Receiving Element 41 Magnet 43 Yoke Member 43a Outer yoke 43b Inner yoke 51 Luminous flux 53 Reflective mirror 55 Recording disk

Claims (1)

[Claims] 1. An optical head in which an objective lens holder having an objective lens mounted therein is rotatably and slidably fitted to a holder support shaft to drive the objective lens in a focusing direction and a tracking direction. In order to balance the weight of the objective lens holder with respect to, the light source is fixed to the balancer attached to the objective lens holder, and the light irradiation position from the light source is fixed to the immovable part that is immovable with respect to the holder support shaft. An optical head comprising a light receiving element for detecting.