JPH0428027A - optical pickup - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical pickup that optically reads signals from a rotating information recording disc, such as a compact disc player or a video disc player, and in particular, the present invention relates to an optical pickup that optically reads signals from a rotating information recording disc such as a compact disc player or a video disc player. This relates to a structure that reduces the accumulation of such substances.

2. Description of the Related Art In recent years, there have been remarkable improvements in reproduction technology for information recording disks (hereinafter referred to as disks). In particular, optical pickups are being improved day by day, and even higher performance devices are being sought out.

An example of the conventional optical pickup mentioned above will be described below with reference to the drawings. FIG. 2 shows a configuration diagram for explaining the optical system of a conventional optical pickup. In FIG. 2, numeral 1 is a semiconductor laser, which serves as a light source for an optical pickup. Reference numeral 2 denotes a diffraction grating, which serves to slightly angularly separate the passing laser beam 3 and divide it into three beams, one of which is used for reproducing the information signal and two for tracking. 4
is a half mirror, which has the function of transmitting a part of the laser beam 3 and reflecting the rest. 5 is a laser mirror, and the direction of the laser beam 3 is changed by a beam direction converter 6. A collimating lens 7 has the function of collimating the laser beam. 8 is a focus lens, which directs the laser beam 3 onto the disk 9 by approximately 1 μm.
Converges to a spot of about. IO is a photodiode, upon which a laser beam 3 containing an information signal is incident, the signal is detected and converted into an electrical signal. Reference numeral 11 denotes a concave lens, which functions to correctly focus the laser beam 3 on the photodiode 10 by adjusting its movement parallel to the optical axis.

The operation of the optical system of the optical pick-up tube constructed in this manner will be described below. In FIG. 2, a laser beam 3 emitted from a semiconductor laser 1 is separated into three beams by a diffraction grating 2 and enters a half mirror 4. /X- Laser beam 3 incident on the mirror 4
A part of it is transmitted and the rest is reflected, but the reflected laser beam further enters the laser mirror 5, and this time most of it is reflected and the direction is changed and it enters the collimating lens 7. By passing through this collimating lens 7, the laser beam 3 becomes a parallel beam and enters the focus lens 8.
As a result, the laser beam 3 is focused on the signal pit of the disk 9.

The laser beam 3 reflected from the disk 9, which contains the information signal, is again focused by the focus lens 8, returns along the optical path in the opposite direction, passes through the collimating lens 7, and enters the laser mirror 5. The laser beam 3 that is reflected again by the laser mirror 5 and whose direction is changed is a half mirror.
When it enters lens 4, a part of it that passes through concave lens 1
1 and enters the photodiode 10, where the optical signal is detected as an electrical signal.

Note that in order to stably reproduce the signal from the disc 9, the position of the focus lens 8 with respect to the disc 9 needs to be constant, but if the focus lens 8 approaches or moves away from the disc 9, the half mirror 4
This generates astigmatism, and the photodiode IO detects this astigmatism, and issues a command to move the focus lens 8.

FIG. 3 is a sectional view of the vicinity of the focus lens 8 showing the reproduction state of a conventional optical pickup.

In FIG. 3, 12 is a focus coil for driving the focus lens 8 in the focusing direction, and 13 is a focus lens holding member for holding the focus lens 8 and driving the focus lens 8 in the focusing and tracking directions. coil is installed.

Problems to be Solved by the Invention However, in the above configuration, fine dust or oily foreign matter may accumulate on the surface of the focus lens 8, which may significantly impair the characteristics of the lens.

The present invention solves the above-mentioned problem, and aims to provide an optical pickup having a structure that prevents minute dust and oily foreign matter from accumulating on the surface of the focus lens 8. .

Means for Solving the Problems In order to solve the above problems, an optical pickup of the present invention includes: a focus lens for converging a laser beam onto a disk; a hollow focus lens holding member;
a lens cover having an opening at its tip that is smaller than the effective diameter of the focus lens; further, the hollow interior of the focus lens holding member and the internal space of the lens cover are communicated through the focus lens holding member and the inside of the side wall of the lens cover. It has a structure with ventilation holes.

According to the above-described structure, the present invention has a static pressure inside the hollow part of the focus lens holding member, but a dynamic pressure on the outside of the lens cover due to the influence of the rotation of the disk, which causes the internal space of the lens cover to be drained from the hollow inside of the focus lens holding member. After that, an airflow is generated that blows out to the outside of the lens cover, and this airflow removes minute dust and oily foreign matter that has started to accumulate on both surfaces of the focus lens.

EXAMPLE Hereinafter, an optical pickup according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of the periphery of a focus lens of an optical pickup according to an embodiment of the present invention. The optical pickup shown in FIG. 1 is different from the optical pickup shown in FIG. 3 in that a lens cover 15 is attached to the end of the holding member 13 on the focus lens 8 side. A ventilation hole 14 is provided that communicates between the hollow interior and the interior space of the lens cover 15 through the focus lens holding member 13 and the inside of the side wall of the lens cover 15. It is structured so that it flows along the

At this time, the structure of the lens cover 15 is such that the aperture diameter becomes smaller as it moves away from the focus lens 8, but since the laser beam 3 is converged to one point on the disk by the focus lens 8, the lens cover 15 does not adversely affect the laser beam 3.

The operation of the optical pickup constructed in this way will be described below with reference to FIG. 1.

Except in special cases, the atmosphere near the focus lens 8 of the optical pickup that is playing back the disc 9 often contains dust and oily foreign matter, which accumulates on both surfaces of the focus lens 8. However, since the hollow interior of the focus lens holding member 13 is under static pressure, and the outside of the lens cover 15 is under dynamic pressure due to the rotation of the disk, the ventilation hole is opened from the hollow inside of the focus lens holding member 13. 14. Due to the airflow 17 blown out to the outside of the lens cover 15 through the internal space of the lens cover 15, the dust and oily foreign matter that have started to accumulate on the surface of the focus lens 8 are blown out to the outside of the lens cover 15 without being deposited. It happens.

Effects of the Invention As described above, according to the present invention, there is provided a focus lens for converging a laser beam onto a disk, a hollow focus lens holding member for holding the focus lens, and a focus lens having a diameter smaller than the effective diameter of the focus lens. By providing a lens cover having an opening and further providing a ventilation hole that communicates between the hollow interior of the focus lens holding member and the interior space of the lens cover, the hollow interior of the focus lens holding member is under static pressure. Due to dynamic pressure on the outside of the lens cover due to the rotation of the disk, an airflow is generated from the hollow interior of the focus lens holding member to the outside of the lens cover via the ventilation hole and the internal space of the lens cover. The minute dust and oily foreign substances that have accumulated or are about to accumulate on both surfaces of the disc are removed, and a good reproduction signal can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the periphery of a focus lens of an optical pickup according to an embodiment of the present invention, FIG. 2 is a configuration diagram for explaining the optical system of a conventional optical pickup, and FIG. FIG. 2 is a cross-sectional view showing the vicinity of a focus lens of an optical pickup. 8... Focus lens, 9... Disc, 13...
...Focus lens holding member, 14...Vent hole, 1
5... Lens cover No. 3-)-Zahim/-74-77 or Sude-Dice 2/2-Further-Casco JhL/Left 1. Len people”ηha- Figure Figure Figure

Claims (1)

[Claims] 1. A focus lens for converging a laser beam on an information recording disk, a hollow focus lens holding member for holding the focus lens, and a lens cover having an aperture at its tip that is smaller than the effective diameter of the focus lens. . An optical pickup comprising a ventilation hole that communicates between the hollow interior of the focus lens holding member and the internal space of the lens cover through the inside of the side wall of the focus lens holding member and the lens cover.