JPH0526256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical pickup, and in particular, a cylinder that protrudes vertically is provided around the inner surface of a through hole for passing a light beam bored in the upper part of a fixed cylinder, and A donut-shaped plate larger than the outer diameter of the cylinder is provided around the upper outer circumferential surface of the movable cylinder at a constant distance from the lower end surface, and a donut-shaped plate larger than the outer diameter of the cylinder is provided at a constant distance from the upper lower surface of the fixed cylinder. This invention relates to an optical pickup characterized in that cylinders are erected at intervals to prevent dust from adhering to a tracking permanent magnet or the like.

There are conventional optical pickups as shown in FIGS. 1 and 2. That is, an objective lens 1C is housed inside the upper surface, a rectangular coil 1A for tracking control is attached to the upper outer circumference, and a circular coil 1 for focus control is attached to the outer circumferential surface of the lower part.
The inside of the fixed cylinder 2 has a pair of tracking permanent magnets 2A attached to its upper inner circumferential surface and a focusing cylindrical permanent magnet 2B attached to its lower inner circumferential surface. A pair of parallel plate springs 3 for tracking fixed to a ring 3A whose middle part is in contact with the outer circumferential part of the movable cylinder 1 and whose both ends are fixed to the inner circumferential surface of the fixed cylinder 2 and the outer circumferential part are fixed to the ring 3A. The movable cylinder is arranged via a focus leaf spring 4, which is a composite material of metal spring and rubber, which is fixed to the inner peripheral surface of the fixed cylinder 2 and whose inner peripheral part is fixed to the lower outer peripheral surface of the movable cylinder 1. 1 in the tracking direction (X-axis direction) and the focus direction (Y-axis direction).
It is elastically supported to be movable (in the axial direction).

Then, the emitted light from the semiconductor laser 5 passes through the polarizing beam splitter 6, the collimator lens 7, the 1/4 wavelength plate 8, the 90° deflection mirror 9, and the objective lens 1C, and enters the disk 10, where it is reflected from the disk 10. The light passes through the objective lens 1C, the 90° deflection mirror 9, the 1/4 wavelength plate 8, the collimator lens 7, and the deflection beam splitter 6, and enters the 4-split optical sensor 11.

In this prior art, a through hole 2C for passing the light beam is formed in the upper part of the fixed tube 2, and since there is a gap between the inner surface of the hole 2C and the outer peripheral surface of the objective lens 1C, the movable tube 1 cannot be moved. Due to the suction and discharge of air, dust is generated inside the fixed cylinder 2 (dotted line in the figure).
Inflow. If this dust accumulates between the tracking control rectangular coil 1A and the tracking permanent magnet 2A or between the focus control circular coil 1B and the focus cylindrical permanent magnet 2B, the movable cylinder 1 will get caught when it is moving. The transmission characteristics during movement become strange and the servo characteristics deteriorate.

Furthermore, when sticky particles such as cigarette smoke go around and pass through the weight-reducing through-hole 4A of the focus leaf spring 4 and adhere to the 90° deflection mirror 9 and the 1/4 wavelength plate 8, they are transmitted. index and reflectance deteriorate.

The present invention has been made in view of the problems of the prior art, and aims to solve the above problems by attaching a dustproof device to an optical pickup.

The present invention will be explained below based on the drawings.

FIG. 3 is a diagram showing an embodiment of the present invention.

Reference numeral 20 denotes a cylinder, which is disposed around the inner surface of a through hole 2C for light beam passage formed in the upper part of the fixed cylinder 2, and projects upward and downward. Due to the protruding portion, dust attached to the upper surface of the fixed cylinder 2 does not fall onto the movable cylinder 1.

Reference numeral 21 denotes a donut-shaped plate, which is disposed on the upper outer circumferential surface of the movable cylinder 1 at a position at a constant interval from the lower end surface of the cylinder 20, and its outer diameter is the same as that of the cylinder 2.
This constant interval, which is larger than the outer diameter of
The lower end surface of the cylinder 20 and the upper surface of the plate 21 are determined so as not to come into contact with each other.

Reference numeral 22 is a cylinder, which is erected on the upper surface of the outer circumference of the plate 21, and its upper end surface has a certain gap with the upper and lower surface of the fixed cylinder 2. This constant gap is maintained even if the movable cylinder 1 moves in the focus direction (up and down direction).
The upper end surface of the cylinder 22 and the upper lower surface of the fixed cylinder 2 are determined so as not to come into contact with each other.

The outer diameter of the plate 21 and the wall thickness of the cylinder 22 are set such that the lower outer circumferential surface of the cylinder 20 and the inner circumferential surface of the cylinder 22 do not come into contact even if the movable tube 1 moves in the tracking direction (front/rear or left/right direction). stipulate.

Since dust contained in the outside air comes into contact with the cylinder 20, plate 21, and cylinder 22 and is removed, it is easily removed from the inside of the fixed cylinder 2, especially after the square coil 1A for tracking control and the permanent magnet 2A for triking. It doesn't fit in.

Furthermore, in order to improve the dustproof effect, the cylinder 22 is divided into an inner side 22A and an outer side 22B, and a double cylinder is provided as shown in FIG. Alternatively, a cylinder 23 may be arranged.

In addition, it is possible to more completely prevent dust from entering the focus control circular coil 1B and focus cylindrical permanent magnet 2B, and sticky fine particles from entering the 90° deflection mirror 9 and quarter-wave plate 8. is a sponge stepped cylinder 2 at the bottom of the tracking permanent magnet 2A.
4, and a donut plate-shaped rubber support spring may be used as the focus plate spring 4 without making a hole in the spring itself.

Note that the present invention is applicable not only to the actuator and optical system described above, but also to other types of optical pickups.

As described above, the present invention provides a cylinder that projects vertically on the inner surface of a through hole for passing a light beam formed in the upper part of a fixed cylinder, and is spaced at a constant distance from the lower end surface of the cylinder. A donut-shaped plate larger than the outer diameter of the cylinder is provided around the upper outer peripheral surface of the movable cylinder, and a cylinder is erected on the upper surface of the outer peripheral part of the plate at a constant distance from the upper lower surface of the fixed cylinder. By providing this, it is possible to prevent dust from adhering to the tracking permanent magnet, etc., so that it is possible to prevent the properties of both the objective lens actuator and the optical system from deteriorating due to dust.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional optical pickup;
The figure is an exploded perspective view of FIG. 1 with the fixed cylinder removed, FIG. 3 is a sectional view showing one embodiment of the invention, and FIG. 4 is a sectional view showing another embodiment of the invention. 20, 22, 23...Cylinder, 21...Plate, 24...Stepped cylinder.

Claims (1)

[Claims] 1 The objective lens is housed inside the top surface, and a rectangular coil for tracking control is attached to the top outer circumferential surface.
In addition, a movable cylinder has a focus control circular coil mounted on the outer peripheral surface of the lower part, a pair of tracking permanent magnets are mounted on the upper inner peripheral surface, and a cylindrical permanent magnet for focusing is mounted on the lower inner peripheral surface. In an optical pick-up, the movable tube is elastically supported by a pair of parallel plate springs for tracking and a parallel plate spring for focusing, which are arranged inside a fixed tube to be movable in a tracking direction and a focus direction. , a cylinder protruding vertically is provided around the inner surface of a through hole for light beam passage bored in the upper part of the fixed cylinder, and a cylinder is provided on the upper outer circumferential surface of the movable cylinder at a constant distance from the lower end surface of the cylinder. A donut-shaped plate larger than the outer diameter of the cylinder is provided around the circumference, and a cylinder is erected on the upper surface of the outer circumferential portion of the plate at a constant distance from the upper and lower surfaces of the fixed cylinder to permanently track dust. An optical pick-up characterized by preventing adhesion to magnets, etc.