JPS60157735A - Optical pickup device - Google Patents

Abstract

PURPOSE:To drive linearly an objective lens in response to a servo signal without generating mechanical resonance, etc., by using a thin elastic material like a rubber-like material formed approximately into a bevel or truncated cone shape to produce a bearing means of an objective lens holding member. CONSTITUTION:A support shaft 2 is set vertically at the center part of a discoid substrate 1, and an objective lens holding barrel 3 is attached coaxially to the shaft 2 via a bearing means 4 so that the barrel 3 can move and turn freely in the axial direction. An objective lens 5 is set above the barrel 3 and at a position having eccentricity from the axial center. The means 4 consists of a pair of upper and lower elastic materials 11 and 11 which are fitted to the shaft 2. These materials 11 are actuated with a fixed start torque so as to move up and down and turn angularly the barrel 3 smoothly and with no friction when servo signals are applied to coils 6 and 7. At the same time, the materials 11 also function to give the linear response characteristics to absorb undesired vibration due to mechanical resonance produced between the barrel 3 and various parts attached to the barrel 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical pink-up device for reading information recorded on an optical information recording disk such as a compact disk.

Generally, in this type of optical pick amplifier device, 1
For example, as disclosed in Japanese Unexamined Patent Application Publication No. 57-210456, an objective lens holding cylinder having several objective lenses placed eccentrically from the axis can be rotated around a cylindrical support shaft in the thrust direction. Tracking adjustment is performed by slidingly fitting the objective lens holding cylinder and rotating the objective lens holding cylinder, and focus adjustment is performed by sliding the objective lens holding cylinder in the thrust direction. On the other hand, Japanese Patent Application Laid-Open No. 55-117745 discloses that a shirt 1 to which an optical head is attached to one end is rotatably supported by a slide bearing, and the shaft is rotated by an electromagnetic rotation drive device to perform tracking adjustment. Additionally, an optical pickup device is shown in which the focus is adjusted by moving it in the axial direction using an electromagnetic thrust drive device. Two conventional examples have been given above, and in both of them, a servo voltage is applied to the focus adjustment coil and the tracking adjustment coil to operate the objective lens holding tube or the shaft containing the optical head with high sensitivity and precision. In addition, the bearing part and the spindle of the objective lens holding tube, and the above-mentioned shirt! - and the slide bearing must be closely fitted together without any play. However, it is actually extremely difficult to create such a close fit, and each dimension changes relative to each other depending on temperature and humidity. The occurrence of this was inevitable. For reference, Figure 8 shows the servo frequency sensitivity curve (a curve that indicates whether mechanical operation is controlled linearly with respect to the control input voltage) and the characteristics of the servo frequency vs. phase curve in the conventional structure described above. In addition, FIG. 9 shows a characteristic diagram of the servo voltage applied to the focus adjustment coil versus the axial movement curve of the objective lens holding cylinder. As is clear from the characteristic diagram of FIG. 8, both the sensitivity curve and the phase curve are affected by resonance, and this is presumed to be caused by poor fitting of the bearing portion and unnecessary vibrations and friction. Also, the 9th
According to the characteristic diagram shown in the figure, it is clear that the objective lens holding cylinder does not operate even when a servo voltage is applied up to 0.05V, and that it operates linearly at a voltage higher than that. This is due to the friction of the bearing. Even if a material with an extremely low coefficient of friction, such as Teflon (trade name), is used for the bearing, when two objects rub against each other,
Since there is a force on the contact surfaces that tends to hinder mutual movement, as long as the above-mentioned conventional bearing fitting structure is adopted, as shown in the characteristic diagrams of Figs. 8 and 9, This phenomenon is unavoidable.

The present invention was made in view of the above-mentioned circumstances, and its object is to provide an optical system equipped with a bearing means capable of operating an objective lens holding member linearly in response to a servo signal without causing mechanical resonance or the like. The purpose of the present invention is to provide a pickup device.

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

As illustrated in FIG. 1, this optical pick amplifier device has a disk-shaped substrate 1, and a support 111112 is vertically provided in the center of the substrate 1. . The objective lens holding cylinder 3 is attached to the support shaft 2 by a bearing means 4.
They are coaxially mounted so that they are movable and rotatable in the axial direction. It should be noted that an objective lens 5 is disposed at the upper part of the objective lens holding cylinder 3 at a position eccentric from its axis as shown by an imaginary line. A focus adjustment coil 6 for controlling the focal position of the objective lens 5 by moving the objective lens holding tube 3 along the axial direction of the support shaft 2 and a focus adjustment coil 6 on the peripheral wall of the objective lens holding tube 3 are installed. The objective lens 5 is rotated around the axis of the support shaft 2.
Tracking adjustment coil 7 for controlling tracking of
and is provided. The substrate l is provided with an inner yoke 8 and an outer yoke 9, which are arranged inside and outside the objective lens holding cylinder 3 and form a predetermined magnetic gap with respect to the coils 6 and 7. In this embodiment, a magnet 10 is attached to the inner yoke 8.

In this invention, the bearing means 4 includes a pair of upper and lower elastic bodies 1.1. ．． 11
Consisting of Each of the elastic bodies 11.11 is activated by an extremely small activation torque such that when a servo signal is applied to the coil 6.7, the objective lens holding cylinder 3 is smoothly moved vertically and rotated angularly without friction. While operating, it is configured to absorb unnecessary vibrations due to mechanical resonance between the objective lens holding cylinder 3 and various parts attached thereto, and provide linear response characteristics.

That is, each of the elastic bodies 11 is
As illustrated in the figure, it is formed in the shape of an umbrella, and an insertion hole 12 for the support shaft 2 is provided at the top. The most suitable material for this material is, for example, silicone rubber, which has almost no change in response characteristics even at high temperatures of 90°C or higher and low temperatures of -15°C or lower, has a tensile strength of 10 to 20 kg/cnf, and an elongation rate of 130. %, and a linear shrinkage rate of about 0.3% is selected. Note that when using a material other than silicone rubber, a rubber-like elastic material that satisfies the above characteristics may be selected. In this embodiment, the wall thickness of the umbrella-shaped elastic body 11 is approximately 0.
, 51 jun, but the middle part 13 where bending stress and torsional stress are concentrated has a stress of 0 and 2 compared to other parts.
It has an extremely thin wall thickness of about ++m+~0.3 books. In this way, by making the middle portion [3] extremely thin, it is possible to move the objective lens holding tube 3 more accurately and linearly within a vertical movement range of, for example, ±1 mm and a deer antler rotation range of about ±20 degrees. can. It is also possible to adjust the linear characteristics by forming a flap 14 having a serrated cross section as shown in FIG. 11 on the outer or inner wall of the umbrella-shaped elastic body 11. Further, the elastic body 11 may be formed into a truncated cone shape, as shown in FIG. 5, instead of the umbrella shape described above.

1. The elastic bodies 11.11 are inserted into the support shaft 2 in such a manner that their tops face each other, and the upper and lower edges of the objective lens holding cylinder 3 are attached to their respective skirts, for example. It is fixed using adhesive or the like. In this case, the insertion hole 1 of the elastic body 11
An adhesive may be applied between the support shaft 2 and the support shaft 2 to adhesively fix the two. Thus, according to this invention,
Since the objective lens holding cylinder 3 is attached to the support shaft 2 via an elastic body 11 that exhibits rubber-like elasticity and is formed in the shape of an umbrella or a truncated cone, its response characteristics to servo signals are extremely good. In addition, the effects are remarkable, such as absorbing unnecessary vibrations due to mechanical resonance.

For reference, FIG. 6 shows a characteristic diagram of a servo frequency vs. sensitivity curve and a servo frequency vs. phase curve according to an embodiment of the present invention, and FIG. A characteristic diagram of the axial movement curve of the holding cylinder is shown. According to this, the sensitivity curve and the phase curve have linear characteristics, and the objective lens holding tube is extremely linear with respect to the focus adjustment servo voltage from zero potential to a range of approximately ±1-5 nnn. Since it moves up and down, it is convenient for electrical control.

Although the above embodiment describes an optical pickup device in which an objective lens holding cylinder is movably arranged around a support shaft, the shaft holding the objective lens in an eccentric position can be rotated on a slide bearing. In a device that performs focus adjustment and racking adjustment by sliding or rotating the shaft, the shirt 1 is supported by an umbrella-shaped or truncated cone-shaped elastic body. Yes.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an optical pickup device according to the present invention, FIG. 2 is an external perspective view of an umbrella-shaped elastic body incorporated in FIG. 1, and FIG. A cross-sectional view, FIG. 4 is a cross-sectional view of pleats provided in the umbrella-shaped elastic body, and FIG.
FIG. 6 is a characteristic diagram showing the sensitivity curve and phase curve for the servo frequency of the optical pickup device according to the present invention, and FIG. 7 is the same device. Figure 8 is a characteristic diagram similar to Figure 6 showing the sensitivity curve and phase curve of the conventional device, and Figure 9 is the characteristic diagram of the conventional device. FIG. 7 is a characteristic diagram similar to FIG. 7 showing the operating characteristics of the objective lens holding cylinder in FIG. In the figure, ■ is the substrate, 2 is the support 111111.3 is the objective lens holding tube, 4 is the bearing means, 5 is the objective lens, 6 is the focus adjustment coil, 7 is the tracking adjustment coil, 8 is the inner yoke, and 9 is the Outer yoke, 1o is McNet 1-11
1 is an elastic body. Patent applicant: Audio-Technica Co., Ltd. Agent: Patent attorney: Takuya Ohara

Claims (1)

[Scope of Claims] An objective lens holding member made of a rod-like or cylindrical body having an objective lens attached at an eccentric position, and a bearing means for supporting the objective lens holding member so as to be movable and rotatable in an axial direction. , a focus adjustment electromagnetic driving means for moving the objective lens holding member in the axial direction to control the focal position of the objective lens; and a trunking mechanism for controlling the ranking position of the objective lens by rotating the objective lens holding member. An optical pickup device comprising an electromagnetic driving means for adjustment, wherein the bearing means is made of a thin elastic body exhibiting rubber-like elasticity and having an umbrella shape or a truncated conical shape. type pickup device.