JPS60205838A - Objective lens device - Google Patents

Abstract

PURPOSE:To prevent the secondary resonance of a high frequency band and to improve the discharging effect and then the servo performance, by providing an objective lens holding barrel containing a rib which is set slidably in the axial direction of a support shaft and two coils wound around the outer circumference of said barrel. CONSTITUTION:A holding barrel 2 is set slidably and rotatably in the axial direction of a support shaft 3, and an objective lens 6 is set apart from the shaft 3. The lens 6 is moved toward its optical axis by means of the 1st coil 8 wound around the outer circumference of the barrel 2 to perform focus control. While the lens 6 undergoes tracking control in its circumference direction by the 2nd coil 9. The barrel 2 increases its intensity by means of a rib 10 to prevent the generation of the secondary resonance. The rib 10 can dissipate the heat which is produced when large currents flow to both coils 8 and 9 at a high frequency band. As a result, the servo performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in objective lens devices used in optical disc players and the like.

The objective lens device used in the optical disc brake A/- has an objective lens holding cylinder that holds the objective lens arranged so as to be movable in the thrust direction and the radial direction. Do J: Sea urchins are known. That is, the objective lens is provided by cutting a support shaft for the objective lens holding cylinder, and the racking adjustment is performed by rotating the objective lens holding cylinder.
Also, by moving the objective lens in the thrust direction,
-Kasllll'l l! T! ! There are known devices configured to do this.

Recently, there has been a strong demand for miniaturization of such objective lens devices and high-density disks, and there has been a strong desire to increase the speed of control in the focus direction and radial direction as described above. .

However, since the conventional objective lens holding cylinder had a hollow structure, sub-resonance tended to occur in the form shown in FIG. 4 due to insufficient strength. For example, sub-resonance X may occur in the focus direction and the tracking direction in the practical frequency band.

This type of objective lens device is a two-degree-of-freedom system in which the bobbin is movable in two directions, the focusing direction and the racking direction, and the objective lens, spring, coil, etc. are movable with complex mass distribution. Since it is a body, various vibration modes are likely to occur, and errors are likely to occur in the detection of control signals. Furthermore, in order to improve the efficiency of the driving force, it has become desirable to reduce the thickness of the objective lens holding cylinder to reduce its mass, resulting in insufficient strength. As a result, the above-mentioned problem of sub-resonance has become serious.

Furthermore, as shown in FIG. 4, as the frequency increases, the gain decreases, so the current is avoided to be increased to compensate for the loss, but this also increases the generation of heat.

This invention has been made in view of the above circumstances, and is intended to increase the strength to prevent sub-resonance, especially in high frequency bands, and to improve the servo performance by increasing the heat dissipation effect. The objective is to provide an objective lens H'JR that can be used.

The gist of the present invention for achieving this object is to provide an objective lens holding cylinder rotatable around a support shaft and slidable in the axial direction of the support shaft; an objective lens provided in a lens holding tube apart from the spindle; a first coil means for focus adjustment and a second coil means for tracking adjustment provided inside the objective lens holding tube; and the objective lens. The objective lens device is characterized in that a rib is provided extending from the inside of the holding cylinder in the direction of the support shaft.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 1 indicates the entire bobbin, and an objective lens holding cylinder 2 is provided to be rotatable around a support shaft 3 and slidable in the axial direction of the support shaft 3. In the example shown in the figure, the objective lens holding cylinder 2 is formed with a thin wall as a whole, is hollow inside, and has a bearing 5 extending downward and integrally formed in the center. There is.

The objective lens 6 is provided in the objective lens holding tube 2 apart from the support shaft 3. The balancer 7 is provided in the objective lens holding tube 2 at a position opposite to the objective lens 6.

Further, inside the objective lens holding cylinder 2, a first coil means 8 for focus adjustment and a second coil means 9 for racking adjustment are provided. A first coil means 8 is wound inside the objective lens holding tube 2, and a second coil means 9 is mounted on top of the first coil means 8. The first coil means 8 is for forming magnetic flux in the axial direction of the bobbin 1, and the second coil means 9 is for forming a magnetic flux in the axial direction of the bobbin 1.
They are arranged in pairs centered on the bobbin 1, and are rectangular in shape to form a magnetic flux in a direction perpendicular to the axial direction of the bobbin 1.

A rib 10 extends from the inside of the objective lens holding cylinder 2 in the direction of the support shaft 3. In the illustrated example, four ribs 10 are installed in a cosmic shape, and are formed between the bearing 5, the inside, and the upper part.

The magnetic circuits 11 and 12 are arranged so as to sandwich the circumference of the objective lens holding cylinder 2, the first coil means 8, and the second coil means 9 with a slight distance between them.

These magnetic circuits 11, 12 are composed of permanent magnets and form a constant magnetic field.

The spring 13 is for elastically restricting the movement of the bobbin 1 in the axial and rotational directions, and one end thereof is attached to the base 14.
is fixed.

To explain bobbin control, first, control in the focus direction is a control to move the objective lens 6 in the direction of its optical axis, and is performed by controlling the current flowing through the first coil means 8 and using Lorentz force. be. Also,
Control in the tracking direction is to move and pull the objective lens 6 in the circumferential direction with respect to the spindle 3 of the bobbin 1, and to control the -4 current flowing through the second coil means 9.
′! In particular, J: is performed using the O-Lenz force. Explaining in relation to an optical disk (not shown), if the tracking control M is sufficiently small with respect to the diameter of the bobbin 1, a linear approximation is possible, and the moving direction of the objective lens 6 at that time is set to the disk under test. It coincides with the radial direction (not shown).

FIG. 3 shows a modification of the objective lens apparatus according to the present invention, in which a heat radiation hole 15 is formed in the -1- face of the objective lens holding cylinder 2. Except for these heat radiation holes 15,
The structure of the embodiment shown in FIG. 3 is substantially the same as that of the embodiments shown in FIGS. 1 and 2, so a detailed description thereof will be omitted.

Since the objective lens device according to the present invention is constructed in the same manner as shown in front J and E, the strength of the bobbin (particularly the objective lens holding cylinder) is greatly increased. As a result, the occurrence of sub-resonance can be prevented or minimized. For example, it is possible to prevent the occurrence of the sub-resonance indicated by the broken line Y in FIG.

Furthermore, when used in a high frequency band, as is clear from the graph in FIG. In that case, heat is generated in the coil means as the current increases. However, according to the present invention, since the ribs 10 are provided, the heat dissipation effect from the ribs 10 is great, and the problem caused by heat generation can be solved. In particular, as in the embodiment shown in FIG.
When forming and covering, the heat dissipation effect is greatly improved.

[Brief explanation of drawings]

FIG. 1 is a partially sectional perspective view of an example of an objective lens device according to the present invention, FIG. 2 is a schematic sectional view of the objective lens device of FIG. 1, and FIG. 3 is a schematic sectional view of the objective lens device according to the present invention A partially sectional perspective view showing a modified example, FIG. 4 is a graph showing the relationship between frequency and gain when using a conventional objective lens device, and FIG. 5 shows a frequency when using an objective lens device according to the present invention. It is a graph showing the relationship between and gain. i, , , , , bobbin 2...29. , objective lens 1 temple tube 3,,,,
, , , Support shaft 5 , , , Bearing 6 , , Objective lens 7 , , Balancer 8 , , , , , , 1 coil means 9, . . . , 2nd coil means 10, . . ., ribs 11.12. , , Magnetic circuit 13 , , Spring 14 , , Base 15 . Heat dissipation hole patent applicant Tokyo Kogaku Kikai Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) An objective lens holding tube that is rotatable around a support shaft and slidable in the axial direction of the support shaft, and an objective that is provided in the objective lens holding tube at a distance from the support shaft. a lens, a first coil means for focus adjustment and a second coil means for ranking adjustment provided on the circumference of the objective lens holding cylinder, and a direction from the circumference of the objective lens holding cylinder to the spindle. The objective lens device is characterized by having a rib that extends over it. (2) The objective lens device according to item 1 of the patent, wherein the objective lens holding cylinder has a heat radiation hole on the right side.