JPS59112447A - Dust preventive device of optical pickup - Google Patents

Abstract

PURPOSE:To prevent dust from going into a fixed cylinder, and to prevent the deterioration of a servo-characteristic due to dust by providing circumferentially a doughnut- like plate between the lower end face of a cylinder provided circumferentially on the circumferential surface of a through-hole for making an optical beam pass through, and the outside circumferential surface of the upper part of a movable cylinder. CONSTITUTION:An emitted light from a laser 5 is made incident to a disk 10 through a mirror 9, and its reflected light is made incident to an optical sensor 11. A doughnut- shape plate 21 is provided circumferentially between the lower end face of a cylinder 20 provided circumferentially on the circumferential surface of a through-hole 2C for making an optical beam pass through, and the outside circumferential surface of the upper part of a movable cylinder 1. Also, since a cylinder 22 is provided on the outside circumferential part of the plate 21, even if the movable cylinder 1 moves, a path through which dust is introduced from the outside goes into the inside of a fixed cylinder 2 is elongated, therefore, it is not introduced beyond a tracking controlling coil 1A and a permanent magnet 2A. Accordingly, it is possible to prevent the deterioration of a servo-characteristic, which is caused by the fact that dust is piled on and the movable cylinder 1 is cuaght by the dust.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dustproof device for optical pickup, and particularly,
A cylinder is provided around the circumferential surface of the light beam passage hole drilled in the upper part of the fixed cylinder, and the cylinder is placed at a position on the upper outer peripheral surface of the movable cylinder and at a constant distance from the lower end surface of the cylinder. A dust-proof device for an optical pickup comprising a P-nut-shaped plate that is larger than the outer diameter of the cylinder, and a cylinder that is erected on the upper surface of the outer circumference of the plate with a certain gap between the upper and lower surfaces of the fixed cylinder. Regarding. There are conventional optical pickups as shown in FIGS. 1 and 2. That is, an objective lens 1C with a partially exposed part is housed inside the upper part, a pair of square coils for tracking control are attached to the outside of the upper part, and a circular coil 1B for focus control is attached to the outer part of the lower part. The movable cylinder 1 is placed inside a fixed cylinder 2, which has a pair of tracking permanent magnets attached to the inside of the upper part and a cylindrical focusing permanent magnet 2B installed to the inside of the lower part, and the middle part is movable. A pair of tracking parallel plates fixed to a ring 3A, which is in contact with the outer circumference of the tube 1 and has both ends fixed to the inner circumference of the fixed tube 2;
and a focusing plate spring 4, which is a composite material of metal spring and rubber, whose outer circumferential part is fixed to the inner circumferential surface of the fixed cylinder 2 and whose inner circumferential part is fixed to the lower outer circumferential surface of the movable cylinder 1. The movable barrel 1 is elastically supported so as to be movable in the tracking direction (X-axis direction) and the focus direction (Y-axis direction). Then, the emitted light from the semiconductor laser 5 is transmitted through the polarizing beam splitter 61, the collimator lens 7, the 1/4 wavelength plates 8, 9
(10 deflection mirror 9. disk 1 via objective lens 1C)
0, and the reflected light from the disk 10 is reflected by the objective lens 1.
The light passes through a 0.90° deflection mirror 9, a quarter-wave plate 8, a collimator lens 7, and a polarizing beam splitter 6 before entering a four-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 barrel 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 barrel 1 is movable. suction of air by. Due to the discharge, dust flows into the fixed cylinder 2 (as indicated by the dotted line in the figure). If this dust accumulates between one rectangular coil for tracking control and two permanent magnets for tracking, or between the circular coil for focus control 1B and the cylindrical permanent magnet for focus 2B, the movable cylinder 1 It got stuck, and the transmission characteristics when moving became strange, and what about sir? Characteristics deteriorate. Furthermore, sticky fine particles such as cigarette smoke may disintegrate and disintegrate, causing the focus leaf spring 4
If the light passes through the 900° deflection mirror and attaches to the 9° quarter-wave plate 8, the transmittance and reflectance will 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 the 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 circumferential surface of a light beam passage hole 2C bored in the upper part of the fixed cylinder 2, and its upper part protrudes from the upper surface of the upper part of the fixed cylinder 2. This protruding portion can reduce the amount of dust that has settled on the upper surface of the fixed tube 2 from entering the through hole 2C. 21 This is a hollow-shaped plate, which is installed around the upper outer circumferential surface of the movable cylinder 1 at a position at a constant distance from the lower end surface of the cylinder 20, and its outer diameter is equal to the outer diameter of the cylinder 20. This larger constant interval is determined so that the lower end surface of the cylinder 20 and the upper surface of the plate 21 do not come into contact even if the movable cylinder 1 moves in the focus direction (vertical direction). 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 such that the movable barrel 1 is in the focus direction (
Even if the cylinder 22 moves in the vertical direction), the upper end surface of the cylinder 22 and the fixed cylinder 2
The upper and lower surfaces of the The outer diameter of the plate 21 and the wall thickness of the cylinder 22 are set such that the lower outer peripheral surface of the cylinder 20 and the inner peripheral surface of the cylinder 22 do not come into contact even if the movable cylinder 1 moves in the tracking direction (back and forth or left and right directions). stipulate. In this way, even if the movable cylinder 1 moves, the path for dust to enter the inside of the fixed cylinder 2 becomes longer, so that the dust can easily enter the inside of the fixed cylinder 2, especially the rectangular coil 1A for trunking control. , cannot enter the permanent magnet for dragging after 2A. Sixth, in order to improve the dustproof effect, the cylinder 22 is divided into an inner side 22A and an outer side (11! 122 B), and a fixed cylinder 2 is installed between the inner side 22A and the outer side 221, as shown in Fig. 4.
A cylinder 23 protruding from the upper and lower surfaces of the cylinder 23 (7 is also acceptable) is arranged.
, 1. In order to more completely prevent sticky particles from entering the /4 wavelength plate 8, a stepped sponge cylinder 24 is placed below the two tracking permanent magnets, and a P- A nut plate-shaped rubber support spring may be used without making holes in the spring itself. Note that the present invention relates to the above-mentioned actuator. The present invention is applicable not only to optical systems but also to other types of optical pickups. As explained above, the present invention provides a cylinder around the circumferential surface of a light beam passage hole drilled in the upper part of a fixed cylinder, and a cylinder is provided on the outer peripheral surface of the upper part of the movable cylinder. A cylinder having a P-shaped plate larger than the outer diameter of the cylinder circumferentially arranged at a position with a fixed distance from the lower end surface, and a fixed gap between the upper and lower surfaces of the fixed cylinder on the upper surface of the outer circumference of the plate. By standing up the objective lens actuator, you can prevent dust from entering the fixed tube. The effect of preventing the characteristics of the optical system from deteriorating due to dust can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional optical pickup, Fig. 2 is an exploded perspective view of the m1 diagram excluding the fixed cylinder, Fig. 3 is a sectional view showing an embodiment of the present invention, and Fig. 4 is a sectional view of the present invention. FIG. 7 is a sectional view showing another embodiment. 20.22.23...Cylinder, 21...Plate, 2
4... Number of stages cylindrical patent applicant Akai Electric Co., Ltd. 7- Fu Figure 1 Figure 2, T 23 Figure 3 Figure 4

Claims (1)

[Claims] 1. A cylinder is provided around the circumferential surface of the light beam passage hole drilled in the upper part of the fixed cylinder, and a cylinder is provided at a position on the upper outer peripheral surface of the movable cylinder and at a constant distance from the lower end surface of the cylinder. A dustproof optical pickup comprising a P-nut-shaped plate that is larger than the outer diameter of the cylinder, and a cylinder that is erected on the upper surface of the outer periphery of the plate with a certain gap from the upper and lower surface of the fixed cylinder. Device