JPH03127338A - Optical head - Google Patents

Abstract

PURPOSE:To prevent dust from introducing in an optical path by forming a cylindrical part on the optical head block side correspondingly to an actuator bobbin so that the optical path to an objective lens is surrounded with the cylindrical part. CONSTITUTION:An objective lens 4 is attached to a bobbin 15 of an actuator, and a barrel part 20 of the objective lens 4 is formed in the bobbin 15, and an information recording medium 10 like a disk is arranged above the bobbin 15 and faces the objective lens 4. A cylindrical part 16 of an optical head block 32 is projected to the actuator bobbin 15 so that the optical path between the objective lens 4 and a jumping-up mirror 33 is surrounded with the cylindrical part 16. Thus, dust is prevented from introducing in the optical path to the objective lens 4 from the side because of the cylindrical part surrounding the optical path though the bobbin supporting the objective lens is brought into contact with or separated from the optical head block for the purpose of performing the focus control.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical head used in an information recording/reproducing device that optically records, reproduces, or erases information on a recording medium such as an optical disk or magneto-optical disk. It is.

(Prior Art) This type of information recording/reproducing device uses an optical head equipped with a series of optical systems to randomly record, reproduce, or erase audio or image information using a light beam with high performance. has been done. For example, as shown in FIG. 5, the optical head includes a semiconductor laser 1. Collimator lens 2. Polarizing beam splitter (PBS) 3, 6, 7. Objective lens 4. Condensing lens 5. Servo sensor 8. RF sensor 9
Optical elements such as these are attached to the head block.

In particular, in recent years, optical heads have been made lighter in order to shorten seek time, and as a result, optical heads are also made up of a fixed head part 31 and a movable part that moves for seeking, as shown in FIG. A structure separated into 32 parts is adopted. In this case, the movable part 32 is equipped with an objective lens 4 and a flip-up mirror 33, and the objective lens 4 is moved in the focusing direction and the tracking direction by an actuator (not shown) installed in the movable part 32. It is configured as follows.

(Problem to be Solved by the Invention) The problem here is that the bobbin of the actuator that supports the objective lens 4 has a structure that moves in the optical axis direction of the objective lens when controlling the focus direction. The unit 32 moves toward and away from the optical head block (carriage), and when the unit 32 moves away, dirt, dust, etc. enter the optical head block from above the flip-up mirror 33 and adhere to the mirror 33. , to be deposited. In this way, when dirt and dust adhere to or accumulate on the mirror, the effective value of the laser power is reduced.
This will affect the optical signal and reduce the reliability of the servo signal.

(Object of the Invention) The present invention has been made based on the above circumstances, and is based on the above-mentioned circumstances.
To provide an optical head capable of preventing dust and dirt from entering an optical path between an objective lens and a flip-up mirror with a simple configuration, regardless of the movement of a bobbin in the optical axis direction.

(Means for Solving the Problems) Therefore, in the present invention, an objective lens is used in an optical head that irradiates a disc-shaped recording medium with a focused light beam through an objective lens to perform recording, reproduction, or erasing. Opposed to the bobbin of the actuator that controls the operation in the focus direction and the tracking direction, a cylindrical part projects in the optical axis direction of the objective lens so as to surround at least the optical path to the objective lens, on the side of the optical head block that supports the actuator. It is set up.

(Function) Therefore, even if the bobbin that supports the objective lens moves towards and away from the optical head block for focus control, the cylindrical part surrounds the optical path to the objective lens and there is no interference from the side. Since the intrusion of dirt and dust can be prevented, and the flip-up mirror is therefore kept clean, the effective value of the laser power can be maintained, the optical signal will not be adversely affected, and the servo signal can also maintain high reliability.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIGS. 1 to 3. In FIG. 1, reference numeral 32 denotes an optical head block (
A flip-up mirror 33 is arranged inside, and an optical path window 32a is opened horizontally corresponding to the optical path. The optical path window 3 corresponds to the optical path
2b is an opening. The objective lens 24 is attached to the bobbin 15 of the actuator, which is shown in detail in FIG. 2, and the lens barrel portion 20 of the objective lens 4 is formed on the bobbin 15. A disk-shaped information recording medium 10 is arranged above the bobbin 15 and facing the objective lens 4.

Corresponding to the actuator bobbin 15, the optical head block 32 has a cylindrical portion 16 protruding from the bobbin 15 side so as to surround the optical path between the objective lens 4 and the flip-up mirror 33.

In particular, in this embodiment, the lens barrel portion 2 of the objective lens 4
0 means that it is inserted into the cylindrical portion 16, leaving a clearance within a range that does not hinder control in the tracking direction.

As shown in FIG. 2, the actuator is provided with a shaft support 15a at the center of the bobbin 15, which is fitted onto a support shaft 17 installed on the optical head block 32. It is supported so as to be movable in the axial and rotational directions relative to the support shaft 17. Above bobbin 1
A weight 22 is attached to the weight 5 axially symmetrically with the objective lens 4, and a focusing coil 42 is mounted on the outer periphery of the weight 22, and tracking coils 41 are arranged above it at equal intervals in the circumferential direction. has been done. Further, a magnetic field generating means for generating a magnetic field that crosses the coil 42 is arranged on the optical head block 32 side.

Here, a pair of electromagnetic yokes 18 and 18' are used, which have outer yokes 18b and 18b' and inner yokes 18c and 18c' that are continuous to each other via bottom yokes 18a and 18a'. Yoke 18b, 1
Magnets 19 and 19' are attached to opposite surfaces of 8b'. And the inner yoke 18c, 18
c' is a half-moon-shaped engagement hole 15b, 1 formed in the bobbin 15;
It is loosely inserted into 5b'. In the figure, reference numeral 21 indicates a control rubber portion for returning the bobbin 21 to the neutral position (tracking direction).

In such a configuration, an electromagnetic force acts on the bobbin 15 by controlling the current to the coils 41 and 42, and when the coil 41 is energized, a rotating force is generated in either the forward or reverse direction.
When energized, a force is applied in the vertical direction (focus direction), and the bobbin 15 moves along the support shaft 17. In particular, when the bobbin 15 is moved in the vertical direction by the energization of the coil 42, the optical path of the objective lens 4 and the flip-up ξ roller 33 expands and contracts, but the cylindrical portion 16 extends in the optical axis direction. Since the lens barrel part 20 of the objective lens 4 is fitted,
Prevents dirt and dust from entering from the sides. As a result, dust flies up onto the mirror 33.

Since dust does not adhere or accumulate and is kept clean, the effective value of the laser power is not reduced, the optical signal is not adversely affected, and the servo signal can maintain high reliability. 3(a) shows a state in which the bobbin 20 has moved to the upper limit, and FIG. 3(b) shows a state in which it has descended to the lower limit, and the optical path is always surrounded by the cylindrical portion 16. is made clear.

In the embodiment shown in FIG. 4, the cylindrical portion 16 is disposed so as to surround the outer peripheral portion of the actuator bobbin 15 (or the skirt portion extending below it). In this case as well, dirt and dust are substantially prevented from entering the optical path between the objective lens 4 and the flip-up roller 33. In addition, by including the lens barrel part 20 as is, the optical path is surrounded twice,
The dustproof effect can be further enhanced.

In the above embodiment, the cylindrical portion 16 was provided protruding only from the optical head block 32 side, but it is also possible to actively protrude toward the cylindrical portion 16 by using the lens barrel portion 20 and the outer circumferential portion of the pobbin 15. It is preferable to provide a cylindrical portion on the bobbin 15 side to prevent dirt and dust from entering the optical path.

(Effects of the Invention) The present invention has been described in detail above, and by forming a cylindrical part on the optical head block side so as to surround the optical path to the objective lens, corresponding to the actuator bobbin that supports the objective lens. It is possible to prevent dirt and dust from entering the optical path between the objective lens and the flip-up mirror, thereby realizing highly reliable servo.

[Brief explanation of the drawing]

Fig. 1 is a vertical side view showing an embodiment of the present invention, Fig. 2 is an exploded perspective view of the main parts, Figs. A longitudinal side view of another embodiment,
5 and 6 are perspective views showing the configuration of a conventional optical system. 4... Objective lens, 15... Bobbin, 16... Cylindrical part, 20... Lens barrel part, 32... Optical head block (carriage), 33... Flip-up mirror

Claims (1)

[Claims] In an optical head that irradiates a disc-shaped recording medium with a focused light beam through an objective lens to perform recording, reproduction, or erasing, an optical head that faces the bobbin of an actuator that controls the operation of the objective lens in the focusing direction and tracking direction. An optical head characterized in that a cylindrical portion is provided on the optical head block side supporting the actuator so as to protrude in the optical axis direction of the objective lens so as to surround at least the optical path to the objective lens.