JPH0210490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for moving an objective lens vertically and horizontally in an optical pickup device, and in particular, it provides focus control to an objective lens holder on which an objective lens is attached and a coil support piece attached to the objective lens holder. A tracking moving body is provided in which a tracking control coil and a tracking control coil are fixed in directions orthogonal to each other, and both coils are arranged in a gap between a pair of focus/tracking magnetic circuits, and are arranged parallel to a disk. The present invention relates to a vertical and horizontal movement device for an objective lens of an optical pickup device, which supports the objective lens holder so as to be movable vertically and horizontally via a parallel plate spring for focusing and a parallel plate spring for tracking.

An example of focus and tracking control in a conventional optical pickup device is shown in Figures 1 and 2. According to these, focus (Z-axis direction) control is performed by voice coil electromagnetic drive, and tracking (X-axis direction) control is performed by linear drive. This is done by electromagnetic driving of a motor, and the object to be driven is the objective lens 1 in both cases.

That is, a cylindrical permanent magnet 4 to which the objective lens 1 is fixed is mounted on a parallel plate spring 3 for tracking mounted inside the lens barrel 2, and a voice coil 5 is provided around the middle of the lens barrel 2, protruding from the middle part of the lens barrel 2. A cylindrical permanent magnet 4 and a voice coil 5 are arranged in a linear motor electromagnetic drive section 7 installed in the upper part of the storage tube 6 and in a voice coil electromagnetic drive section 8 installed in the middle part of the storage tube 6, respectively. , the storage tube 6 is installed using a focus parallel plate spring 9 having a circular hole in the center.
A lens barrel 2 is held inside, and the objective lens 1 is moved in the Z-axis direction or the X-axis direction depending on the direction and magnitude of the current flowing in the voice coil 5 or the coil 10 in the linear motor electromagnetic drive section 7. In this way, the tracking drive section and the focus drive section are arranged in two stages perpendicular to the disk D.

In this prior art, the parallel plate spring 3 for tracking preferably has a small spring constant in order to have a wide range of tracking motion, and also needs to have a somewhat large spring constant in order to stand on its own. Furthermore, metal is preferable because it is not affected by temperature changes. Taking all of the above into consideration, long metal leaf springs are generally used. Accordingly, the height _H1 of the optical pickup device in the Z-axis direction becomes large, which poses a problem in that the optical pickup device becomes large and heavy.

In addition, when the housing of the disk rotation drive motor and the optical pickup housing body are on the same side, when picking up the inner circumference of the disk, the separation distance R ₁ between the optical axis and the outer surface of the optical pickup housing in the disk radial direction must be as small as possible. However, since the focus drive unit composed of the voice coil 5 and the voice coil electromagnetic drive unit 8 and the objective lens 1 are arranged concentrically, there is a problem that the size cannot be reduced beyond a certain level.

The present invention was made by focusing on the problems of the prior art, and includes an objective lens holder to which an objective lens is attached, and a coil support piece attached to the objective lens holder, and a focus control coil and a tracking control coil. The two coils are fixed in directions orthogonal to each other, and both coils are placed in the gap between a pair of focus/tracking magnetic circuits, and a tracking moving body placed parallel to the disk creates a focus parallel plate. The object of the present invention is to solve the above-mentioned problems by supporting the objective lens holder so as to be movable vertically and horizontally via a spring and a parallel plate spring for tracking.

The present invention will be explained below based on the drawings.

FIG. 3, FIG. 4, FIG. 5, and FIG. 6 are diagrams showing one embodiment of the present invention.

First, the structure will be described. Reference numeral 11 denotes an objective lens holder, which has a circular hole 11A' formed in the vertical direction, and the objective lens 1 is mounted in the circular hole 11A'.

Reference numeral 12 denotes a rectangular focus control coil, which is fixed to the side surfaces 11A and 11B of the objective lens holder 11 with a constant gap _G1 between the side surfaces 11C and 11D of the objective lens holder 11. The height H ₂ ' of the focus control coil 12 is set lower than the height H ₁ ' of the objective lens holder 11.

Reference numeral 13 denotes a coil support piece, which has a U-shaped cross section and includes an opposing upper side 13A, a lower side 13B, and a vertical side 13.
It consists of an objective lens holder attachment part made of C, and a pair of plates 13D protruding from the vertical side 13C in the opposite direction to the upper side 13A and the lower side 13B. It is fixed via 13B. The separation distance H ₃ between the upper side 13A and the lower side 13B is approximately equal to the height H ₁ ' of the objective lens holder 11.

When the upper side 13A (or lower side 13B) extends over the circular hole 11', a circular hole 13E is bored in the upper side 13A (or lower side 13B). The vertical side 13C is in contact with the focus control coil 12 fixed to the side surface 11A of the objective lens holder 11.
Height H _3D of plate 13D is the height of vertical side 13C
Lower than _H3C .

14 is a rectangular tracking control coil whose height H ₄ is approximately equal to the height H _3D of the plate 13D and whose width W ₄ is larger than the width W _3D of the plate 13D.
It is fixed to the upper and lower surfaces of the plate 13D with a constant gap G ₂ from the vertical outer surface of the plate 13D, and is perpendicular to the focus control coil 12.

Objective lens holder 11 and coil support piece 1
3, the focus control coil 12 and the tracking control coil 14 are fixed in directions orthogonal to each other, so that the focus control coil 12 and the tracking control coil 14 are arranged on the same horizontal line. Z-axis height of
H ₂ becomes smaller, allowing the optical pickup device to be made thinner.

Reference numeral 15 denotes a pair of magnetic circuits for both focus and tracking, which are attached to the side surface 11 of the objective lens holder 11.
The other opposing side 15A that is longer than the separation distance W ₂ of the fixed parts 12A and 12B of the focus control coil 12 fixed to A and 11B, the opposite side 15B that is shorter than the separation distance W ₂ , and the other opposing side 15A and the opposite side 15
A focus magnetic body with a concave cross section consisting of a horizontal side 15C connecting the lower part of B, a side 15D fixed to the upper part of the inner wall of the other opposing side 15A, and a side 15D longer than the other opposing side 15A, which is constant with the end face of the opposite side 15B. The other side 15E and one side 15D with a gap G ₃
and a connecting side 15F that connects the other side 15E, and the height _H5 is the tracking control coil 1.
A tracking magnetic body whose height H is lower than ₄ and has a square shape in plan view, and which is fixed to a part of the inner wall of one side 15D, and one opposite side 15B and the other side 1.
There is a constant gap G ₄ between the inner walls of 5E, and the void part 1
It is composed of square bar-shaped permanent magnets 15G forming 5H.

The length of one opposing side 15B is determined so that the distance t between the end face and the fixing portions 12A, 12B of the focus control coil 12 is approximately 0.3 mm. The height _H5 of the tracking magnetic body is determined so that the distance f between the upper surface (or lower surface) of the other side 15E and the horizontal portion of the tracking control coil 14 is about 1 mm. By setting the separation distances t and f in this manner, even if an overcurrent flows through the focus control coil 12 or the tracking control coil 14, the tracking control coil 14 and the other side 15E
or the focus control coil 12 and the opposite side 15B are in contact, the focus control coil 12 is 1 mm or more, and the tracking control coil 1
4 does not move more than 0.3 mm, and these coils 12 and 14 also serve as a stopper when the servo returns, so there is no need to provide a separate stopper.

Focus/tracking magnetic circuit 15
is arranged with its longitudinal direction parallel to the tracking movement direction (X-axis direction), and is fixed to the base 16A of the optical pickup housing 16.

The non-fixed parts 12C and 12D of the focus control coil 12 and a part of the tracking control coil 14 are arranged in the gap 15H.

Since no magnetic circuit is disposed on the left side of the fixed portion 12B of the focus control coil 12, the separation distance _R2 between the optical axis and the outer surface 16B of the optical pickup housing 16 can be reduced. Furthermore, instead of using separate magnetic circuits for focus and tracking, only a pair of magnetic circuits 15 for focus and tracking can be used, so parts costs and assembly costs can be reduced.

Reference numeral 17 denotes a focus parallel plate spring, which is installed on the upper and lower parts of the vertical side 13C of the coil support piece 13 and the upper and lower surfaces of the outer end 18A of the tracking moving body 18,
The objective lens holder 11 is elastically supported so as to be movable in the focus movement direction (Z-axis direction) from the outer end 18A.

The tracking moving body 18 has an outer end 18A having a height slightly lower than the height H ₁ ' of the objective lens holder 11, and an outer end 18A that protrudes toward the objective lens holder 11 from the center of the outer end 18A.
A horizontal piece 18B having a height lower than _8A and having an inverted T-shaped planar shape, and a parallel plate spring for tracking with an inverted L-shaped side surface protruding from both sides of the tip of the horizontal piece 18B. A through hole 18D for weight reduction is vertically bored in the horizontal piece 18B, and a parallel plate spring mounting piece 18E for tracking is formed on the upper outer surface of the outer end 18A.
is installed protrudingly. Parallel plate spring for focus 17
The tracking movable body 18 is parallel to the disk D.

Reference numeral 19 denotes a parallel plate spring for tracking, whose height is greater than the height _H8 of the outer end 18A, and stands between the parallel plate spring mounting pieces 18C and 18E of the tracking moving body 18 and the base 16A of the optical pickup housing 16. The tracking movable body 18 is elastically supported so as to be movable in the tracking movement direction (X-axis direction) from the base 16A.

Next, the action will be explained. When the focus error signal or the tracking error signal is zero, no current flows through the focus control coil 12 or the tracking control coil 14, and the objective lens holder 11 remains stationary at a predetermined position. If there is a focus error signal now, a current flows through the focus control coil 12. Since the direction of this current and the direction of the magnetic flux of the focus/tracking magnetic circuit 15 are perpendicular to each other, the focus control coil 12 receives a force in the vertical direction (Z-axis direction) based on Fleming's left hand rule. Since the focus control coil 12 is integrated with the objective lens holder 11 and is elastically supported by the focus parallel plate spring 17, it moves in the vertical direction (Z-axis direction). Therefore, the objective lens 1, which is integrated with the focus control coil 12 through the objective lens holder 11, also moves in the vertical direction (Z-axis direction). Note that the direction and amount of movement are determined by the direction and magnitude of the current flowing through the focus control coil 12.

Next, when there is a tracking error signal, a current flows through the tracking control coil 14. Direction of this current and focus/tracking magnetic circuit 1
Since the directions of the magnetic fluxes 5 are perpendicular to each other, the tracking control coil 14 receives a force in the left-right direction (X-axis direction) based on Fleming's left-hand rule. The tracking control coil 14 is integrated with the objective lens holder 11, and the tracking parallel plate spring 1 is attached to the tracking moving body 18 via the focus parallel plate spring 17.
Since it is elastically supported in the left-right direction (X-axis direction) by 9, it moves in the left-right direction (X-axis direction). Therefore, the tracking control coil 14
The objective lens 1, which is integrated with the coil support piece 13 and the objective lens holder 11, also moves in the left-right direction (X-axis direction). Note that the direction and amount of movement are determined by the direction and magnitude of the current flowing through the tracking control coil 14.

Note that the focus error signal and the tracking error signal are generated by the semiconductor laser 2 as shown in FIG.
0 laser beam is guided to the polarizing beam splitter 21, collimator lens 22, 1/4 wavelength plate 23, 90° deflection mirror 24, and objective lens 1, and the reflected light from disk D is guided to the polarizing beam splitter 21 in the reverse order. The beam is returned to the original position, deflected by 90 degrees, and guided to a four-split optical sensor through a light shielding plate (not shown).

As described above, the present invention provides a focus control coil and a tracking control coil that are mounted on an objective lens holder to which an objective lens is mounted and a coil support piece attached to the objective lens holder in directions perpendicular to each other. Both coils are fixed and placed in the gap between a pair of magnetic circuits that also serve as focus tracking, and a tracking moving body placed parallel to the disk moves the coils through a parallel plate spring for focus and a parallel plate spring for tracking. By supporting the objective lens holder so that it can move vertically and horizontally, it is possible to make the optical pickup device thinner, lighter, and lower in cost, and the distance between the optical axis and the outer surface of the optical pickup housing can be reduced. can be made smaller, so
The advantage is that a disk rotation motor housing with a large diameter can be used.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the prior art, FIG. 2 is an exploded perspective view of a tracking drive unit of the prior art, FIG. 3 is an exploded perspective view showing an embodiment of the present invention, and FIG. 4 is an embodiment of the present invention. A plan view showing an example, FIG. 5 is a schematic sectional view taken along the line A-A in FIG. 4 including the optical system, and FIG.
It is a BB schematic cross-sectional view of the figure. 1... Objective lens, 2... Lens barrel, 3... Parallel leaf spring for tracking, 4... Cylindrical permanent magnet, 5... Voice coil, 6... Storage tube, 7...
Linear motor electromagnetic drive section, 8...Voice coil electromagnetic drive section, 9...Parallel plate spring for focus, 10
... Coil, 11 ... Objective lens holder, 12
... Focus control coil, 13 ... Coil support piece, 14 ... Tracking control coil, 15
... Focus/tracking magnetic circuit, 1
6... Optical pick-up housing, 17... Parallel plate spring for focusing, 18... Tracking moving body, 19... Parallel plate spring for tracking.

Claims (1)

[Claims] 1. A rectangular focus control coil 12, a coil support piece 13, and a rectangular tracking control coil 1.
4. A pair of focus/tracking magnetic circuits 15, a focus parallel plate spring 17, a tracking moving body 18, a tracking parallel plate spring 19
The square focus control coil 12 is connected to the objective lens holder 11 on which the objective lens 1 is attached.
on both sides 11A, 11B of said both sides 11A, 11
The coil supporting piece 13 is fixed to both orthogonal side surfaces 11C and 11D of the objective lens holder 11 which are orthogonal to B, with a gap G1, and the coil support piece ₁₃ is connected to an objective lens holder mounting portion having a U-shaped cross section and the objective lens holder. A pair of plates 13D protrude from the back side of the vertical side 13C of the mounting section and are lower than the height _H3C of the vertical side 13C, and the objective lens holder mounting section is attached to the upper and lower surfaces of the objective lens holder 11. The rectangular tracking control coil 14 is fixed via the upper side 13A and the lower side 13B.
The coil support piece 13 is fixed to the upper and lower surfaces of the plate 13D with a distance G ₂ from the vertical outer surface of the plate 13D, and the pair of focus/tracking magnetic circuits 15 have a focus magnetic circuit having a concave cross section. a tracking magnetic body having a J-shaped planar shape;
The height of the tracking control coil 14, which is composed of a square bar-shaped permanent magnet 15G and whose height is square, is
H ₄ and the length of one side 15D is longer than the other opposing side 15A of the focusing magnetic body.
The tracking magnetic body is placed inside the other opposing side 15A of the focus magnetic body, which is longer than the separation distance W ₂ between the fixing parts 12A and 12B of the rectangular focus control coil 12 fixed to The end face of the other side 15E is fixed to the end face of the opposite side 15B of the focusing magnetic body, which is formed shorter than the separation distance W ₂ , via the side surface of the side 15D with a distance G ₃ , and the The permanent magnet 15G is fixed to the other side of the side 15D with a distance G ₄ from the opposite side 15B and the other side 15E, and the pair of focus/tracking magnetic circuits 15 are attached to the base of the optical pickup housing 16. 16A, a part of the rectangular focus control coil 12 and the rectangular tracking control coil 14 are disposed in the empty part 15H of the pair of focus/tracking magnetic circuits 15, and the focus parallel plate A spring 17 is installed between the upper and lower parts of the vertical side 13C of the coil support piece 13 and the upper and lower surfaces of the outer end 18A of the tracking moving body 18, and the tracking parallel plate spring 19 is connected to the tracking moving body 18. A device for vertically and horizontally moving an objective lens of an optical pickup device, which is installed between the base 16A of the optical pickup housing 16 and the base 16A.