JPH0434207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The lens actuator of the present invention uses a laser as a light source to condense light onto a recording track formed on a disk-shaped recording medium (hereinafter referred to as a disk) to record information. The present invention relates to a lens actuator for an optical recording/reproducing device for recording or reproducing information.

Conventional Structure and Problems Therewith, in an optical recording and reproducing apparatus, the recording and reproducing characteristics are determined by the convergence state of the light beam on the recording track, that is, the aberration on the focal plane.

A factor that adversely affects this light focusing state is the inclination between the optical axis of the objective lens housed in the disk and the lens actuator, that is, the aberration caused by the light emitted from the objective lens entering the disk obliquely. and the inclination between the laser optical axis (referring to the optical axis from the laser to the objective lens) and the objective lens optical axis, that is, the aberration caused by the oblique incidence of the incident light on the objective lens. When the diameter of the disk is large, such as 8 inches or 12 inches, the warpage of the disk becomes large, so that the influence of aberrations caused by the inclination between the disk and the optical axis of the objective lens becomes relatively large. On the other hand, when the optical path length from the laser to the objective lens is long, as in the case of an optical head called a separate optical head that moves only the optical path conversion mirror and lens actuator in the disk radial direction, the incident light on the objective lens Since fluctuations in the optical axis of the light tend to increase, aberrations caused by the inclination between the objective lens optical axis and the laser optical axis become dominant.

Therefore, when using a small disk such as a compact disk, or when using a separate optical head, reducing the inclination with respect to the laser optical axis is a major adjustment item for the optical recording/reproducing apparatus.

A conventional example will be described below with reference to FIG. The disk 1 is attached to a turntable 2 that is coaxially attached to a motor 3 and rotates around the Z axis in the figure. On the other hand, the light emitted from the semiconductor laser 4 has its optical path changed by a mirror 5 and enters an objective lens 7 housed in a lens actuator 6. Further, an optical unit 9 including a semiconductor laser 4, a collimator lens, a quarter-wave plate, a beam splitter, a photodetector, etc. (not shown) is attached to the carriage 8, and a lens actuator attached to the optical unit 9 is attached. For example, the disk 1 is moved by a stepping motor together with the Yuator 6.
is transported in the radial direction.

In an optical recording/reproducing device having such a configuration, the inclination of the optical axis of the semiconductor laser 4 and the optical axis of the objective lens 7 is mainly caused by processing errors, etc., on the bottom surface of the lens actuator 6, that is, the mounting surface of the lens actuator. This is largely due to the perpendicularity deviation of the optical axis of the objective lens 7 relative to the optical axis.

However, the lens actuator disclosed in, for example, Japanese Unexamined Patent Publication No. 53-120403 does not have a means for correcting verticality deviation in the lens actuator alone.

Therefore, in the conventional example, the inclination of the disk 1 and the objective lens 7 is adjusted by rotating the turntable 2 or the carriage 8 around the X and Y axes in the figure so as to obtain the best recording and reproducing characteristics. Ta.

Further, the inclination of the optical axis of the semiconductor laser 4 and the optical axis of the objective lens 7 was similarly adjusted by rotating the mirror 5 so that the recording and reproducing characteristics were optimized.

Such an adjustment method has the drawback that not only does it require a large number of adjustment steps, but also that it is difficult to obtain mutual compatibility between parts when, for example, only the lens actuator is replaced.

Therefore, the present applicants proposed a means for correcting the tilt of the objective lens 7 using the optical axis of the semiconductor laser 4 and the lens actuator alone, as described in Japanese Patent Application No. 58-70350. FIGS. 2 and 3 show a plan view and a front view, respectively. In FIGS. 2 and 3, 11 is a lens barrel housing the objective lens 10, 12a and 12b are tracking drive movable coils fixed to the lens barrel 11, 13 is a focus drive movable coil, 14a, 14b is a tracking drive magnet unit fixed to the housing 18, and 15 is a focus drive magnet unit. The lens barrel 11 has an elastic support member 16
It is movably and elastically supported by a and 16b.

Therefore, as is well known, the focus control signal or the tracking control signal is transmitted to the first moving coil 13 or the second moving coil 12a, 12b.
When energized, the magnet units 14a, 14b,
15, an electromagnetic force according to Fleming's left hand rule is generated, and the lens barrel 11 housing the objective lens 10 is elastically supported by elastic support members 16a and 16b, correcting a focusing error or a tracking error. It will be moved like this.

The elastic support member 16b is coaxially engaged with the lens barrel 11 and the housing 18. On the other hand, the elastic support member 16a is engaged with the lens barrel 11 at its inner circumference, and engaged with the elastic support member holder 17 at its outer circumference.

This elastic support member holder 17 is attached to a housing 18
is attached by screws 19a to 19b. During installation, a through hole larger than the screw diameter provided in the housing 18 is provided in the elastic support member holder 17 so that the elastic support member holder 17 can be moved in the XX and YY directions in the figure. .

Therefore, the elastic support member holder 17 is moved in the XX direction and the YY direction, and the lens barrel 1 housing the objective lens 10 is removed via the elastic support member 16a.
By raising the upper end of the objective lens 10, the inclination of the optical axis of the objective lens 10 with respect to the mounting surface of the lens actuator to the optical unit can be corrected.

However, in the lens actuator having such a configuration, when adjusting the tilt of the objective lens 10,
There is a high possibility that residual stress will remain in the elastic support members 16a and 16b. Therefore, there has been a problem in that the initially perpendicularity of the optical axis cannot be maintained over time due to relaxation of residual stress.

OBJECT OF THE INVENTION The optical pickup of the present invention solves the above-mentioned conventional problems. Specifically, it makes it possible to correct the inclination between the optical axis of the objective lens and the mounting surface of the lens actuator, reducing the number of adjustment steps and increasing mutual compatibility when replacing parts such as the lens actuator and optical unit. The purpose is to obtain.

Structure of the Invention The present invention provides an objective lens for condensing light emitted from a light source onto a recording track formed on a disk-shaped recording medium, a lens barrel housing the objective lens, and a lens barrel for each lens barrel. an electrical focusing drive means and a tracking drive means that drive the objective lens in the optical axis direction and the recording track radial direction; an elastic support member that supports the objective lens movably in the two directions; The entire casing is provided with a casing that accommodates the fixing part and to which the elastic support member is fixed, and the casing is rotatable around two axes that are perpendicular to the optical axis of the objective lens and perpendicular to each other. The tilt of the objective lens optical axis with respect to the mounting surface of the lens actuator can be corrected by rotating the entire lens actuator around the two axes. This makes it possible to correct the inclination of the objective lens and lens actuator toward the mounting surface with a single unit.

DESCRIPTION OF EMBODIMENTS FIG. 4 is a cross-sectional view of a lens actuator in one embodiment of the present invention, and FIG. 5 is a perspective view of the entire lens actuator. In FIGS. 4 and 5, 21 is a disk, 22 is an objective lens, 23 is a lens barrel housing the objective lens 22, 24 is a moving coil for focus control, 25a, 25b is a moving coil for tracking control, 27a, 27b are tracking drive magnet units, 26a, 26b
2 denotes an elastic support member, and 28 denotes a housing of the entire lens actuator.

This lens actuator is significantly different from the conventional lens actuator, as shown in FIG. By rotating the optical axis of the objective lens 22 around two axes that are orthogonal to the optical axis of the laser beam and mutually orthogonal, that is, the X axis and Y axis in the figure, the optical axis of the objective lens 22 is aligned with the laser optical axis, that is, the Z axis in the figure. It is possible to adjust it to match the axis. That is, it becomes possible to correct the optical axis of the objective lens 22 and the inclination of the light incident on the objective lens 22. As this rotation adjustment mechanism, for example, a mechanism as shown in FIG. 6 can be mentioned.

FIG. 6 is a front view of the first embodiment of the rotation mechanism. 22 is an objective lens, 28 is a housing, 31a, 3
1b is a hemispherical protrusion formed on the housing 28. 32a and 32b are hemispherical grooves provided in the lens actuator supports 29a and 29b, respectively. By configuring the rotation adjustment mechanism as described below, the optical axis of the objective lens 22 can be adjusted by rotating the housing 28 around the X-axis and Y-axis in the figure with the hemispherical protrusions 31a and 31b as axes. The rotation can be adjusted to match the Z axis. That is, the lens actuator alone can correct the optical axis tilt of the objective lens 22 with respect to the optical axis of incidence on the objective lens 22.

Furthermore, the configuration shown in FIG. 7 is also possible as another embodiment of the rotation adjustment mechanism. FIG. 7 shows a second embodiment of the rotation adjustment mechanism. Reference numerals 33a and 33b are protruding step portions provided on the housing 28, and two through holes are provided in each of the protruding step portions 33a and 33b.
Two screw holes are provided in each of a and 29b. As a result, screws 34a, 34b, 34c and 3
The stepped portions 33 each protrude to a height of 4d (not shown).
a, 33b, and lens actuator support 29
By adjusting the springs 38a, 38b and 38c, 38d (not shown) arranged between a and 29b, the rotation of the casing 28 can be adjusted around the X and Y axes. Therefore, rotational adjustment is possible so that the optical axis of the objective lens 22 coincides with the Z axis. That is, the lens actuator alone can correct the optical axis tilt of the objective lens 22 with respect to the incident optical axis.

Another embodiment of the rotation adjustment mechanism is shown in FIG. The lens actuator supports 29a and 29b are screwed into the housing 28 by screws 35a and 3 through two through holes provided in each.
5b, 35c, and 35d (not shown). Since the through hole is bored with a diameter larger than the screw diameter, the rotation adjustment around the Y axis can be performed by rotating the housing 28 using the side surfaces 36a and 36b of the lens actuator supports 29a and 29b as guides. It is done. Further, the rotational adjustment around the X-axis is also possible through the through holes of the lens actuator supports 29a, 29b and the screws 35a, 35b.
This is done by utilizing the gaps between the lens actuator support 29 and 35c and 35d.
Rotation adjustment is performed by plastically deforming portions A of a and 29b. At this time, part A is configured to be easily plastically deformed by providing a slit or using a low-rigidity material such as aluminum. With the above configuration, the housing 2
8 can be rotated around the X and Y axes. Therefore, rotational adjustment is possible so that the optical axis of the objective lens 22 coincides with the Z axis. That is, the lens actuator alone can correct the optical axis tilt of the objective lens 22 with respect to the incident optical axis.

According to the embodiments described above, the optical axis of the objective lens can be tilted with respect to the incident optical axis without leaving any residual stress in the elastic support member. Therefore, the number of man-hours required for adjusting the optical recording/reproducing device can be reduced, and mutual compatibility between parts can be achieved.

This is especially true when using a small disk that has less warpage than a video disk such as a compact disk, or when using a separate head that moves only the lens actuator, where fluctuations in the optical axis of incidence on the objective lens are less likely to occur. In an optical recording/reproducing device, where the inclination of the objective lens optical axis and the incident optical axis has more influence on the focusing characteristics than the inclination of the disk and the laser beam, such as when the target is large, the lens actuation as in this example is The effect of being able to adjust the inclination of the objective lens optical axis and the incident optical axis with the Yueta alone is significant.

Note that as long as the lens actuator alone can adjust the inclination of the objective lens optical axis and the incident optical axis, it is possible to use a rotation adjustment mechanism other than the three mentioned in this example. Needless to say.

Effects of the Invention As described above, according to the present invention, a lens barrel housing an objective lens, a focusing drive means and a tracking drive means, an elastic support member that supports the objective lens movably in the two directions,
The lens actuator housing is perpendicular to the optical axis of the objective lens and is attached to the support of the entire housing so that it can rotate around two axes that are orthogonal to each other, so that the incidence of the optical axis of the objective lens can be adjusted. The elastic support member can be tilted with respect to the optical axis without leaving any residual stress. Therefore, the number of man-hours required for adjusting the optical recording/reproducing device can be reduced, and mutual compatibility between components can be realized.

This is especially true when using a compact disk that has less warpage compared to a large disk such as a video disk, or when using a separate head that moves only the lens actuator, where the optical axis of incidence on the objective lens is In optical recording and reproducing devices, where the inclination of the objective lens optical axis and the incident optical axis has more influence on the light focusing characteristics than the inclination of the disk and the laser beam, such as when the fluctuation of the optical axis is relatively large, the lens actuator The effect of being able to adjust the inclination of the objective lens optical axis and the incident optical axis with just the eta is significant.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of a conventional lens actuator, Fig. 2 is a plan view of a lens actuator conceived prior to the present invention, Fig. 3 is a sectional front view of the same lens actuator, and Fig. 4 The figure is a sectional front view of a lens actuator in one embodiment of the present invention, and FIG. 5 is a perspective view of the lens actuator.
FIG. 6 is a partially sectional front view of the lens actuator, and FIGS. 7 and 8 are perspective views of the lens actuator in other embodiments. 22... Objective lens, 28... Housing, 29a,
29b...Lens actuator support, 31
a, 31b... hemispherical projection, 37a, 37b...
...hole, 34a, 34b, 34c...screw, 35
a, 35b, 35c, 35d... screws.

Claims (1)

[Claims] 1. An objective lens that focuses light emitted from a light source onto a recording track formed on a disc-shaped recording medium, a lens barrel that houses this objective lens, and a lens barrel that is connected to the optical axis of the objective lens. an electric focusing drive means and a tracking drive means for driving in the direction and the radial direction of the recording track; an elastic support member for movably supporting the objective lens in the two directions; and a fixing part of the drive means. The lens actuator is provided with a housing to which the elastic support member is fixed, and the housing is attached to a support body so as to be rotatable around two axes that are perpendicular to the optical axis of the objective lens and perpendicular to each other. A lens actuator that is capable of correcting the inclination of the optical axis of the objective lens by itself.