JPS58150139A - Driving device of objective lens - Google Patents

Abstract

PURPOSE:To prevent the resonance of an objective lens in the jitter direction at a light angle to the tracking direction thereof and to improve the oscillation characteristics of the oscillation system of the objective lens, by providing the 1st and the 2nd elastic members which absorb and prevent resonance to the 1st and the 2nd spring members, and providing the 3rd elastic member which absorbs and prevents the resonance in the jitter direction. CONSTITUTION:An objective lens 48 can be turned around the mounting part of a leaf spring 56 of a movable holding cylinder 43 and be moved by a prescribed distance in the direction at a right angle to the optical axis by conducting the electric current corresponding to tracking errors to a pair of stationary coils 42. The cylinder 43 can be moved by a prescribed distance in the optical axis direction of the lens 48 against spiral leaf springs 36, 39 by conducting the electric current corresponding to focusing errors to a movable coil 45. The disturbance in the oscillation characteristics generated by the displacement rate of the objective lens and the resonance thereof in the jitter direction with respect to the driving frequencies of delayed phases is eliminated by a circular disc damper 44. The oscillation characteristics particularly in the focusing direction are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an objective lens driving device particularly suitable for application to a device that reads information by projecting a reading light spot onto an information track recorded spirally or concentrically on a recording medium. The present invention relates to a damper mechanism for preventing unwanted photographing.

The above-mentioned information reading device is conventionally known, and a recording medium having an information track is, for example, called a video disk. While rotating a video disc on which optical information such as the following is recorded, the optical information is read by focusing laser light emitted from a laser light source and projecting it onto the video disc. One of the special features of such recording media is that the information recording density is very high, so that the width of each information track is very narrow and the spacing between successive information tracks is also very narrow. . Therefore, the diameter of the reading light spot is also extremely small. In order to accurately read the original information from an information track with such a narrow width and pitch, it is necessary to minimize the relative positional deviation between the reading light spot and the information track, that is, the tracking error. To this end, Shingeki tracking control has conventionally been used to detect the relative positional deviation between the reading light spot and the information track, and to displace the nine reading light spots in the width direction of the information track based on this tracking error signal. It is being done. As such a tracking mechanism, it has been proposed to dispose a vibrating mirror in the optical path between the laser light source and the objective lens, and to move this mirror together using a tracking error signal. However, with such a tracking mechanism, sufficiently satisfactory accuracy and response characteristics cannot be obtained, and it is difficult to obtain a small and inexpensive @1 layer.

In addition, in order to eliminate such defects, the objective lens or its holding frame is supported by an elastic support member made of a leaf spring, and the objective lens is moved perpendicular to its optical axis and the information track based on the tracking error signal. A method of displacement in the direction was proposed.

In a driving device using such a leaf spring, possible methods for moving the objective lens include a method using an electromagnet, a voice coil method, and a method using a piezoelectric element, but in order to maintain good tracking response characteristics, It is necessary to make it small and lightweight. In actual equipment, in addition to such tracking errors, there is also a forcing error in which the light spot is not correctly focused on the information track.
In order to correct this force shifting error, a force shifting mechanism for displacing the objective lens in the direction of its optical axis is also required. If the tracking mechanism is to be installed on top of the force-force traction mechanism, the tracking mechanism must be small and compact in order to perform force-force traction correction well.
It needs to be lightweight. Tracking mechanisms using electromagnets can provide the necessary force and are relatively easy to make compact and lightweight, but the relationship between the current flowing through the electromagnetic coil and the amount of displacement of the objective lens is non-linear, making accurate tracking difficult. It is not possible to correct errors. In addition, the voice coil method has drawbacks such as difficulty in reducing the size and weight, and devices using piezoelectric elements are difficult to obtain the necessary force.

In order to solve the above-mentioned drawbacks, the applicant connected the objective lens to a movable holding cylinder so that it can be displaced in the tracking direction by a pair of strip-like leaf springs extending in the optical axis direction, and the movable holding cylinder An objective that moves an objective lens in a focusing direction parallel to its tip axis and in a tracking direction perpendicular thereto by being connected to a fixed housing so as to be displaceable in a focusing direction via a pair of spiral plates 41. We are proposing a lens drive device.

However, in such an objective lens drive device, the displacement characteristic of the objective lens in the focusing direction is disturbed because the C spiral plate resonates around the drive frequency of s o o Hz, and in the tracking direction it is distorted at g kHz. In the above case, the strip-like leaf springs were both twisted in the direction perpendicular to the optical axis, causing some disturbance. Due to these disturbances, it is difficult to perform sufficiently accurate control.

I: In order to solve the drawbacks of the gutter mentioned above, the applicant proposed an improvement of the objective lens driving device in Japanese Patent Application No. 1982-268@.

Figures 1 (M) and (B) are the above-mentioned special 1111856-2
FIG. 68 is a plan view and an fflIr110 diagram showing a part of the structure of an example of an objective lens driving device that is driven two-dimensionally as llr[NO. Gap S between circular permanent magnet 8 fixed to outer frame 1 and circular yoke 8.4
A bobbin 6a is formed integrally with the coil holding cylinder 6 inside, and a movable coil 7 is wound around the outer periphery of the bobbin 6a. Both ends of the coil holding cylinder 6 are held by tube leaf springs, that is, spiral leaf springs 8 and 9, the spiral leaf spring 8 is held by the outer frame 1, and the spiral leaf spring 9 is held by a spacer 10 connected to the outer frame. . Furthermore, a fixed permanent magnet 18 is provided for the fixed yoke 11% via the yoke holding frame 11. Fixed date] 2 &: is a fixed date for driving the objective lens 14 in the tracking direction.
5 will be provided. The objective lens 14 is a lens holding frame 1 provided with a movable magnetic body 16? to hold the lens holding frame 17.
It is connected and held to the coil holding cylinder 6 by a pair of leaf springs 8.

Further, the above-mentioned member-wound plate spring 8.9 has a circular shape formed of an elastic body.

A pump 19 e g O is provided. This circular tamper 1
9 and go are all hollow circular shapes, and neoprene rubber, butyl rubber, etc. are used as the elastic material. The above-mentioned leaf spring 18 is also provided with dampers 21 and 24 formed of an elastic body.

Note that the arm g8 is a spiral portion of the single-volume plate spring 9.

When a current corresponding to the tracking error is applied to the movable coil 7, the objective lens 14 is displaced in the optical axis direction, and when a current corresponding to the tracking error is applied to the fixed coil 15, the objective lens 14 is displaced in the direction perpendicular to the optical axis. It can be displaced. According to such a configuration, the objective lens 14 near 50011Z is caused by the circular damper 19.20.
Disturbances in the amount of displacement disappear, and disturbances of g kHz or higher are eliminated by the dampers 21 and 22.

However, after conducting a more detailed study, we found that the objective lens 14, which is indicated by some arrows, shows the characteristics of the displacement and phase delay of the objective lens and the driving frequency shown in FIGS. It was detected that disturbances in the displacement amount and phase delay characteristics occurred in the frequency range of 500 to 600 Hz and also in the driving frequency range of 8 times and 8 times that frequency range.

This is due to the jitter in one direction, that is, the tracking direction perpendicular to the optical axis z-2 of the objective regaz] 4, as shown in Figure 168! -1, it was further clarified that this is because the vibration system of the objective lens 14 causes resonance in the perpendicular jitter direction Y-Y. This jitter is common to IM in one direction Y-Y.
&: The disturbance in the vibration characteristics of the vibration system of the objective lens 14 is
This makes it difficult to obtain satisfactory accuracy and response characteristics for a single-movement device with an objective lens. Note that the symbol @T-T indicates the direction of the track 1°.An object of the present invention is to solve the above problems, prevent jitter from resonating in one direction perpendicular to the tracking direction of the objective lens, and An object of the present invention is to provide an objective lens driving device in which the vibration characteristics of a vibration system are improved.

The invention connects an objective lens for focusing a light beam onto an information track to an intermediate movable member via a VHL spring member which holds the objective lens displaceable in its optical axis and in the tracking direction perpendicular to the information track. , this intermediate M #IJ
l! A second plate (connected to the fixed member via one member, and a tracking member connected to the first and second spring members, respectively) holds the ii material so as to be able to be displaced in a force pushing direction parallel to the optical axis of the objective lens. first and second elastic members are provided for absorbing and preventing resonance in the tracking direction and the forcing direction, and are provided between the intermediate piping member and the second spring member at right angles to the tracking direction and the forcing direction. #8 to absorb and prevent resonance in one direction
8 elastic members are provided.

Below, refer to the drawings to understand the present invention! Explain based on the # axis.

FIGS. 4(B) and 4(B) are a vertical 111]iIf view and a bottom view showing the configuration of an example of the objective lens plowing device of the present invention.

A permanent magnet 82 concentrically inscribed in a cylindrical outer frame 81
The circular yokes aaa and aab are fixed through the yoke. The field aab has a cylindrical portion 84 concentrically with the outer frame 81 at the center thereof, and this cylindrical portion 84 and the groove 88a form a concentric ring ms on the inside of the outer frame 81. A spiral plate spring 86 concentrically inscribed in the outer frame 81 is sandwiched and fixed between spacers 87' and a8 also concentrically inscribed in the outer frame 81.

In addition, the outer frame 81 is internally fitted in a stepped manner to the hole of the outer frame δ1.
A spiral leaf spring 89 is mounted concentrically with the .

Furthermore, a pair of fixing parts are provided on the inside of the outer frame 81 in accordance with the earthen figure of the spacer 88. - A pair of permanent magnets 41 are fixed 111- inside the #40. A pair of coils 42 is wound around each of these yokes 4"0.

Each spiral leaf spring 86. The upper end of the movable holding cylinder 48 having a circular S portion 48a provided in a seven-lung shape on the inner axis of J19 is brought into contact with the lower surface of the spiral plate spring 86,
A circular plate damper 44 whose lower end is made of an elastic material such as rubber.
It is connected to a coiled spring 89 as a vibration system via. This cylinder of town movement holding 11I4a! @The bottom surface of 543a is narrower than the damper 44 at the part where it contacts the circular plate damper 44, and is formed into an upward curvature in the direction in which the movable coil 45 is wound from the contact outer circumferential direction. Wrap the IJJ moving coil assembly 5 on the outside, and attach the 48b and fill 4b to the yoke 88a,
8ab and the permanent stone 82. A pair of plate springs 46 are provided facing each other on the movable holding cylinder 48, and these plate springs 46 form a lens holding frame 47 made of a uniform plate in a space surrounded by the respective fixed yokes 40 and permanent magnets 41. The objective lens 48 is held within the outer frame 81 via the outer frame 81. In addition, a plate damper 49 made of an elastic material is moved inside each of the plate springs 46, and a circular damper 50 made of an elastic material, for example, rubber, is attached to the spiral plate number 1 86. The round end of the leaf spring 86 is fixed.

In the objective lens drive device having such a configuration, the objective lens 48 is rotated around the attachment point of the leaf spring 46 of the movable holding cylinder 48 by passing a current corresponding to the tracking error through the pair of constant coils 42. .

can be moved by a predetermined amount in a direction perpendicular to its optical axis. Also, moving coil 4! By applying a current corresponding to the force-twisting error to I, the movable holding cylinder 48 is moved against the spiral plate 86, 89, and the objective lens 4 is
8 can be moved by a predetermined amount in the optical axis direction.

As shown in Figure 831, disturbances in the vibration characteristics due to resonance in one direction due to the jitter of the objective lens displacement amount and phase lag with respect to the drive frequency are shown in Figures r1 (m) and (
As shown in the characteristic diagram B), it disappears due to the circular plate damper 44. In particular, the vibration characteristics in the focus direction were improved. This includes a plate damper 49 fixed to a plate spring 46 that supports a movable holding cylinder 4δ that is displaced together with the objective lens 48 in the focus direction, a circular damper 50 fixed to a spiral spring 86, and a movable holding cylinder 48 made of an elastic body. Circular plate damper 4
This is due to the connection as a vibration system via 4.

In this example, a circular rubber plate with holes in the center of the circular plate damper 44 is used.

As shown in (B) and (0), a circular plate damper 44a has a hole in the annular portion, a radial cut toward the outer circumference of the annular portion, and a radial cut toward the center of the hole.

44b, 440 can be used. As for the material,
Elastic materials such as neoprene, NBR, polyurethane, silicone rubber, fluorine rubber, and natural rubber are used.

As described above, the objective lens drive device of the present invention has the effect of preventing jitter and resonance of the objective lens in one direction, stabilizing the vibration thread, and improving the vibration characteristics in the focus direction in particular. However, the present invention is not limited to the above-described embodiments, and numerous modifications and changes can be made.

For example, in the embodiment, the circular damper i has a spiral plate δ
Although the power is distributed to the upper surface of the coil 9, it may also be arranged below the coiled plate spring 86 or on the inner coiled plate springs 86 and 139, respectively.

[Brief explanation of drawings]

FIGS. 1(M) and 1(B) are a plan view showing a part of the 1111 series, which is an example of a conventional objective lens drive device, and I
IE#1 side view, Figures 8 (M) and (,B) are characteristic diagrams of the displacement amount and phase delay of the objective lens shown in Figures 1 (M) and (B), and the driving frequency, @8 The figure is a schematic perspective view of IiA showing the positional relationship in one direction of jitter, and FIGS. Figures 5 (M) and (B) are characteristic diagrams of the displacement amount, phase delay, and drive frequency of the objective lens of the embodiment of the present invention shown in Figures 1 (M) and (B), and Figure 6 (M). ), (B) and (0
) are diagrammatic plan views showing modifications of the circular plate damper shown in FIGS. 1(M) and 1(B). 81...Outer frame 82...Circular permanent magnet 8
8 a, 88 b...circular w-0°a4...
Cylindrical part 85... - space 86... Spiral plate 87. JI8... Spacer 89... Spiral leaf spring 46... Fixed image 41... Permanent magnet
42...Fixed coil 48...iJ dynamic holding cylinder
43a, 48b...circle f1m44.44a, 44b
, 44C...Circular plate number 45...-■ Moving coil 46...Plate number imitation 47...Lens holding frame 48...Objective lens 49...Plate plate number-60
・・・Circular evening "Nnoze". Patent applicant: Olin, <Sukou Kogyo Co., Ltd. Figure 1 (A) (R) Number of hawks for Todo (HE) Figure 4 (AJ (mouth) U Figure 5 2 Dado Kutakaei (Hz)

Claims (1)

[Claims] The objective lens that focuses the light beam onto the information track is placed at right angles to its optical axis and the information track.
2. T) The intermediate opening J
The movable member is connected to the fixed member via a second spring member that holds the movable member so as to be displaceable in the forcing direction parallel to the optical axis of the objective lens, and the first and second spring members are provided with the tracking direction and the second spring member, respectively. First and second elastic members are provided to absorb and prevent resonance in the force-shinging direction, and jitter is generated perpendicularly to the tracking direction and the force-shinging direction between the intermediate moving member and the 16g spring member. An opposing lens driving device characterized by being provided with an eighth elastic member that absorbs and prevents resonance in one direction.