JPS61239438A - Objective lens driver - Google Patents

Abstract

PURPOSE:To facilitate easy control of the optical axis of a matter to be driven with operation of a fastening screw by separating the matter to be driven and including an objective lens from a drive part including an attachment base and magnets. CONSTITUTION:The magnetic circuit members 17a and 17b consisting of yoke plates 3a and 3b and rectangular parallel piped magnets 4a and 4b magnetized in the thickness direction are fixed on a base 2 made of a die-cast material and having an opening part 1 at the center part by means of setscrews 5a and 5b with the polarities of the same sides set opposite to each other. The magnetic fluxes of the members 17a and 17b are produced toward arrows of magnetic gaps 6a and 6b respectively. Thus the 1st part is formed. Then the 2nd part is set opposite to the 1st part. That is, a support frame 7 and a terminal plate 14 are set opposite to the plate 3a of the member 17a for formation of a square. Then an end of each horizontal part of support springs 8a-8d is stuck to each of four corners of said square with an adhesive. While the other end of each horizontal part of screws 8a-8d is stuck to each of four corners of a mobile frame 9 respectively.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention aims to read information optically recorded on a recording medium. The present invention relates to an objective lens driving device that drives in a direction.

[Conventional technology]

In optical reproducing devices that use laser light, signals are detected by focusing the laser light onto a minute spot using a lens, etc. However, in order to detect signals correctly, the light must be adjusted according to the irregularities and vibrations of the information recording carrier. Focusing control to focus the spot on the information recording carrier and tracking control to always make the optical spot follow the correct signal track are required. Furthermore, if a time axis error occurs due to uneven rotation of the information recording carrier, control is required to correct this error. In order to perform these controls, an error detection device that detects each error and an actuator that moves the optical system to cancel the errors are required.

Conventionally, for this purpose, a so-called voice coil was provided on the driven body including the objective lens to make it movable in the optical axis direction, and mirrors with mutually orthogonal rotation axes were placed in the optical path leading to the objective lens. However, a configuration is known in which the optical path is moved in two directions perpendicular to the optical axis by rotating these mirrors, thereby controlling the focal position in three independent directions.

In addition, there is a method in which an optical system using an objective lens with a narrow angle of view is supported by an elastic support member such as a plate spring, and vibrated in the direction of the optical axis and in the direction perpendicular to the optical axis using a corresponding electric signal. It has been proposed in No. 138903, etc. In such a device that drives the objective lens two-dimensionally, possible methods for driving the objective lens include a method using an electromagnet, a voice coil pair method, and a method using a piezoelectric element, but focusing and tracking responses are In order to maintain good performance, it is necessary to make it small and lightweight.

In particular, the present invention relates to an objective lens drive device that uses a coil on the side of a driven body including an objective lens, uses a magnetic circuit based on an electromagnet on the drive side, and performs tracking control and focusing control using the same magnetic circuit.

[Problem that the invention seeks to solve]

It is very difficult to align the optical axis of the driven body including the objective lens with the optical axes of other optical components. For example, when playing a digital audio disc, the tilt accuracy is ±0.1° with respect to the assembly reference plane of the driven body including the objective lens.
However, in order to achieve the above value, it is necessary to suppress the processing accuracy of each part to within several μm, which has the disadvantage that the price of one part becomes extremely expensive.

An object of the present invention is to provide a highly accurate objective lens drive device that does not particularly require high accuracy in parts processing during one assembly.

[Means to solve the problem]

The above object is achieved by making it possible to separate the driven body including the objective lens from the drive unit including the mounting base and magnet.

[Effect]

A part of the drive unit including the mounting base and the magnet has at least one screw hole, and the driven body including the objective lens is attached to the mounting base side with a screw.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

On the upper surface of the base 2 made of die-cast material with an opening 1 in the center shown in FIG.
Magnets 4a and 4b having a rectangular parallelepiped shape and magnetized in the thickness direction
The magnetic circuit members 17a and 17b consisting of the setscrew 5a
, 5b, etc., as shown in FIG. 1, so that the same polarity faces each other. Magnetic circuit members 17a, 17
magnetic pole of b.

The directions of the magnetic lines of force are as shown in FIG. 4, and magnetic fluxes are generated in the directions of the arrows in the magnetic gaps 6a and 6b, respectively. The above is the first part shown in FIG. 7(b).

In contrast, the second portion shown in FIG. 7(a) is opposed to this. That is, the support frame 7 and the terminal plate 14 are provided opposite to the yoke plate 3a of the magnetic circuit member 17a, and with these as fixed ends, support springs are attached to the squares thereof, as is clear from FIGS. 2 and 1. One end of each horizontal portion 8a to 8d is adhered with adhesive.

The other ends of the support springs 8a to 8d are bonded to the squares of the moving frame 9 with adhesive.

On the other hand, objective lenses 20a, 20b, 20C [seventh
The lens barrel 10 that accommodates the lens frames 11a that accommodate the lenses shown in FIG.

11b with an adhesive.

A square focusing coil 12 is fixed to the outer surface of the square lens frame 11b with adhesive. Track king coil 1 on the square of this focusing coil 12
3a to 13d are fixed with adhesive. Then, the focusing coil 12 is sandwiched between the lens frames 11a and l.
Support (suspension) holders 18a and 18b are fixed to the support holders 18a and 18b with adhesive, and the free ends a of the vertical portions of the support springs 8a to 8d shown in FIG. 1 are fixed to the support holders 18a and 18b.

b, c, and d are fixed with adhesive. Here, the other end of each vertical portion of the support springs 8a to 8b is integrated with each horizontal portion, and is fixed to the moving frame 9 with an adhesive. The two tracking coils 13a to 13d are connected in series, and both ends thereof are soldered to free ends a and b of each vertical portion of the support springs 8a and 8b. Further, both ends of the forcing coil 12 are soldered to the free ends c and d of the respective vertical parts of the support springs 8c and 8c. Therefore, each coil is electrically connected to the terminal plate 14 via the leaf springs 8a to 8d.
The tracking coils 13a to 13d are electrically connected to terminals 14a and 14b, and the focusing coil 12 is electrically connected to terminals 14c and 14d via the copper foil surface of the terminal board 14. This second part shown in FIG. 7(a) is assembled by attaching the terminal plate 14 together with the support frame 7 by the setscrews 19 shown in FIG. 7(b), FIG. 2, and FIG. Figure 2.

It is fixed to the base 1 of the first part shown in FIG.

With this configuration, two sets of coils 12.1
3a to 13d exist in the magnetic gaps 6a and 6b shown in FIG. 3, and are displaced in the Y direction by energizing the focusing coil 12, and the tracking coils 13a to 1
By energizing 3d, it is displaced in the X direction.

Here, as described above, the lens barrel 10 to which the objective lens is fixed has three lenses 20 as shown in FIG.
Objective lenses having configurations a, 20b, and 20c are arranged and fixed at the end closer to the disk side (upper side). Therefore, in FIG. 2, the lens barrel 10. Lens frame 11at
The center of gravity G of the driven body consisting of the llbt coils 12, 13a to 13d is located near the objective lens in the lens barrel 10. On the other hand, the center of the driving force of the driven body in the tracking direction is on the center of the vertical portions of the tracking coils 13a to 13d, that is, on the virtual plane including DE.

Point F is the center in the optical axis direction of the objective lens. On the other hand, the center of gravity G of the driven body will be located above this point F. Therefore, at the lower end of the lens frame Ilb below the lens barrel 10, there is a window 15a in the center through which the light beam can pass.
A weight 15 equipped with the above is fixed with an adhesive. By attaching this weight 15, the center of gravity of the driven body itself
is lowered to make the center of gravity G of the driven body coincide with the center of the driving force F in the tracking direction of the driven body.

The weight 15 is made of a non-magnetic material such as brass or aluminum. Here, the support springs 8a to 8d are withdrawn a.
d are approximately equally spaced from the center F of the driving force in the tracking direction. Also, this weight 15.

In FIG. 2, when the setscrews 19 are not tightened, that is, when the driven bodies 10 to 13 are fixed to the support springs 88 to 8d and the support frame 9, the structure is such that they can be fixed later. It can easily respond to changes in temperature.

In this figure, a cover 16 is provided to protect the objective lens driving device according to the present invention.

The cover 16 is fixed to the stepped portion 2a of the base 2 with an adhesive.

FIG. 8 is a vibration frequency characteristic diagram in the tracking direction of the objective lens driving device according to this embodiment. Tracking control is performed by passing a driving current through the tracking coils 13a to 13d to move the driving body including the objective lens in the tracking direction. In FIG. 6, the horizontal axis represents the frequency supplied to this driving current, and the vertical axis represents the frequency supplied to this driving current. The upper part shows the amplitude relative displacement characteristics, and the lower part shows the phase characteristics. In the figure, f□ is the support spring 88
The lowest resonant frequency f2 determined by the rigidity of ~8d and the mass of the driven body lO~13 is a coupled resonant (rolling) frequency that occurs at several times the frequency f□.

FIG. 9 is an explanatory diagram when the objective lens driving device is driven in the tracking direction.

If the weight 15 is not attached, as shown in Fig. 9(a),
When the driving force F in the tracking direction is supplied to the driven object 10 including the objective lens 20, it will tilt. Moreover, the direction of inclination is in the direction opposite to the driving force F, away from the disk track. Therefore, when the tracking error signal is tilted as shown in FIG. 9(a) due to the driving force in the tracking direction, the tracking error signal becomes larger because it tilts away from the disk track. This results in the spot being missed.

Moreover, as shown in FIG. 8, the phase is delayed by more than 180 degrees at frequency f2, so the tracking servo oscillates at frequency f2, making servo impossible. Therefore, conventionally it has not been possible to perform accurate tracking control. Weight 1 for that
5, and when the center of gravity G is made to coincide with the driving force F in the tracking direction using the weight 15 as shown in FIG. 9(b), the solid line in FIG. 8 becomes 180 degrees or more at one frequency f□. Since no phase delay occurs, accurate tracking control can be performed.

〔Effect of the invention〕

As described above, according to the present invention, the optical axis of the driven body can be easily adjusted by the tightening force of the screw.

Furthermore, since the driven body and the drive section can be assembled separately, each can be easily checked.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a two-dimensional objective lens drive device according to an embodiment of the present invention, FIG. 2 is a developed view thereof, FIG. 3 is a perspective view of a magnetic circuit member, and FIG. 4 is a perspective view of the objective lens drive device. Amplitude frequency characteristic diagram, Figure 5 is a plan view of Figure 1, Figure 6 is a front view of Figure 1, Figure 7 is a sectional view before assembly, Figure 8 is a vibration frequency characteristic diagram, Figure 9 ( It is an explanatory diagram of driving the driven body in the tracking direction. 2... Base, 3... Yoke plate, 4... Magnet, 5... Screw, 7... Fixed frame, 8... - Support spring, 9... Moving frame, 10... Lens barrel housing the objective lens, 11... Lens frame, 12.13... Drive coil, 14... Terminal plate, 19...・Screws. Fig. 1 No. 7 (cL) Fig. 3 Circumference A 1 piece (1-12) Fig. 5

Claims (1)

[Claims] 1. A driven body including an objective lens, an elastic support member that elastically supports the driven body so as to be movable in the focusing direction of the optical axis of the objective lens and in the tracking direction perpendicular to the optical axis, and the driven body a first portion including a focusing coil and a tracking coil fixed to the second portion;
and a second part including a magnetic circuit member in which two coils are located within the same magnetic gap, the first part and the second part are assembled together, and the focusing coil and the tracking coil are located in the same magnetic gap. An objective lens driving device characterized in that the objective lens is fixed in a state where it is bounded by.