JPS59191146A - Optical scanner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical head for use in recording and reproducing optical disks in optical information recording and reproducing devices such as optical information file devices and optical video disk devices. The present invention relates to an optical scanning device.

[Prior art]

An optical head is used to record information on an optical disc or to reproduce information recorded on an optical disc. This optical head focuses laser light onto the information surface of the optical disc,
The light receiving element is configured to detect reflected light modulated by a diffraction phenomenon caused by the bits of the information track. However, since the position of the information track fluctuates due to deformation, eccentricity, etc. of the optical disc, it is necessary to make the focal point of the laser beam follow this fluctuation. For this reason, conventionally, Figure 1'O.

Optical scanning devices such as those shown in FIG. 1 and FIG. 2, respectively, have been used.

In FIG. 1, the objective lens 2 is replaced by a voice coil type linear motor (not shown), etc., for fluctuations in the optical axis direction (two directions) of the objective lens 2 of the information track (1-1) due to the rotation of the optical disc 1. By driving in two directions, the focal point of the light beam 4 is made to follow this variation. Also, the radial direction (X direction) of the optical disc 1 of the information track (1-1)
In response to this variation, the movable mirror 3 provided in the optical path of the light beam 4 is rotated as shown by the broken line to deflect the light beam 4 and cause the focal point to follow this variation.

In the system shown in FIG. 1, the diameter of the aperture of the objective lens 2 needs to be larger than the diameter d of the incident light beam of the light beam 4 by the amount of lateral shift of the incident light beam due to the deflection of the light beam 4. Therefore, there is a drawback that the objective lens 2 becomes large. In addition, since the angle of incidence of the light beam 4 entering the objective lens 2 changes, the objective lens 2 suffers from comatic aberration in addition to spherical aberration.
It is necessary to correct field curvature, etc., which makes it expensive. Furthermore, there is also a drawback that the reflected light (4-2) of the optical beam 4 undergoes lateral movement due to the deflection of the optical beam 4, making it difficult to accurately control the focal point.

FIG. 2 is an explanatory diagram showing another type of conventional optical scanning device.

In FIG. 2, the focal point of the light beam 4 is located on the information track (
1-1) Optical axis direction (Z direction) and radial direction (X direction)
In order to follow the fluctuations in , the objective lens 2 is driven in two directions and in the X direction by a method disclosed in, for example, Japanese Unexamined Patent Publication No. 57-71532.

By the way, in the method shown in FIG. 2, the angle of incidence of the light beam 4 entering the objective lens 2 does not change and remains constant, so the objective lens 2 only needs to correct spherical aberration. will be cheaper than However, the incident luminous flux diameter d of the light beam 4 needs to be made larger than the aperture diameter of the objective lens 2 by the amount of movement of the objective lens 2 in the X direction, which has the disadvantage of a large light loss. Furthermore, as the objective lens 2 moves in the X direction, the reflected light of the light beam 4 -(4
-2) Another disadvantage is that lateral movement occurs and accurate control of the focal point is difficult.

[Purpose of the invention]

It is an object of the present invention to eliminate the drawbacks of conventional optical scanning devices;
It is an object of the present invention to provide an optical scanning device that can use an inexpensive objective lens, has little light loss in the objective lens, and prevents lateral movement of reflected light.

[Summary of the invention]

In order to achieve the above object, in the present invention, only the objective lens is driven in the optical axis direction to follow the variation in the optical axis direction of the objective lens of the optical disc, and the variation in the radial direction of the optical disc is Together with the objective lens, the mirror is also driven in the radial direction so that the optical axis of the light beam and the optical axis of the objective lens are substantially aligned.

[Embodiments of the invention]

Hereinafter, embodiments of an optical scanning device according to the present invention will be described in detail with reference to the accompanying drawings.

3 and 4 are diagrams explaining the principle of the optical scanning device according to the present invention, in which FIG. 3 corresponds to a plan view and FIG. 4 corresponds to a front view. However, the optical disk is not shown in FIG. 3.

In FIGS. 3 and 4, 1 is an optical disk, 2 is an objective lens that can be displaced in the X direction and two directions, 4 is a light beam,
Reference numeral 6 indicates a raised mirror fixed to the outside, and reference numeral 7 indicates a mirror that can be displaced only in the X direction.

In the above configuration, when the optical disk 1 changes in the optical axis direction (two directions), the objective lens 2 is driven in the Z direction to cause the focal point of the light beam 4 to follow this change. Moreover, with respect to the fluctuation of the optical dimmer 1 in the radial direction (X direction), the objective lens 2 and the mirror 7 are driven in the receiving direction to follow this fluctuation as shown by the broken line in the figure.

In the method shown in FIGS. 3 and 4, the angle of incidence of the light beam 4 on the objective lens 2 does not change, so the objective lens 2 can be an inexpensive one that corrects only spherical aberration, and Since the aperture diameter of 2 and the beam diameter d of optical beam 4 can be made approximately equal, there is little loss of light quantity. Furthermore, since no lateral movement occurs in the reflected light (4-2)', the focal point can be accurately controlled.

5 to 8 are diagrams showing one embodiment of the optical scanning device according to the present invention, in which FIG. 5 is a plan view of the present embodiment, FIG. 6 is a longitudinal sectional view, and FIG. 7 is a Z(+ ) direction, and FIG. 8 is an explanatory diagram illustrating a driving state in the X (+) direction.

In FIGS. 5 and 6, the first driven body 10 includes an objective lens 2, a lens holder 11 having a hole (111) through which the light beam 4 passes, a z-direction driving coil 12, and a hole through which the light beam 4 passes. (13-1), the objective lens 2 is attached to the center of the top of the lens holder 11, and the z-direction drive coil 12 is wound around the bottom of the lens holder 11. The leaf spring holding plate 13 is attached to the side surface of the lens holder 11.

Further, the second driven body 20 includes a mirror 7 and a mid holder 21.
, an X-direction drive coil 22, and a coil bobbin 23. The mirror 7 is installed in the groove of the mirror holder 21 as shown in the figure, and the X-direction drive coil 22 is wound around the side surface of the mirror holder 21. coil bobbin 2
3 is installed.

Here, the first driven body 10 is a first parallel plate spring (14) made of an elastic body such as metal or plastic so that it can be displaced only in the optical axis direction (two directions) of the objective lens 2.
-1) to (i4-4) (each plate is made of a flat plate and is arranged so that the thickness direction is two directions) to the mirror holder 21 of the second driven body 2°. Furthermore, the second driven body 2o is equipped with a second parallel plate spring (24- 1) to (24-4) (each plate is made of a flat plate and arranged so that the thickness direction is in the X direction) to the first protrusion (30-1) of the base 3o. installed.

Further, as a two-way electromagnetic drive means, a magnet (31-1),
(31-2), upper yoke (32-1), (32-2)
, a lower yoke 33, and a center yoke 34, a first magnetic circuit 35 is fixed to the base 3o, and forms a linear motor together with the two-way drive coil 12. In addition, a magnet (36-1), (
36-2), upper yoke (37-1), (37-2),
A second magnetic circuit 40 consisting of a lower yoke 38 and a center yoke 39 is fixed to the upper surface of the second protrusion (30-2) of the base 30 as shown in the figure, and the X-direction drive coil 22
Together with this, a linear motor is formed.

The raising mirror 6 is used to further change the direction of the light beam 4, which has entered the mirror 7 and has been redirected in the tangential direction of the information track, toward the optical axis of the objective lens 2. It is fixed to the upper part of the center yoke 34 of the circuit 35.

In the above configuration, when a current is supplied to the two-direction drive coil 12 in response to fluctuations in the optical axis direction (two directions) of the C1 optical disk 1, the first driven body 10 receives forces in two directions, and the first driven body 10 receives forces in two directions. Due to the action of parallel leaf springs (14-1) to (14-4), it is translated in two directions as shown in FIG. On the other hand,
The second driven body 20 is a second parallel leaf spring (24-1)
Due to the property of (24-4) that it is difficult to deform in two directions, there is almost no displacement in two directions as shown in FIG. When a current is supplied to the X-direction drive coil 22 in accordance with the -4), the first driven body 10 is moved in parallel in the X direction.
Due to the property that the first parallel plate springs (14-x) to (14-4) have extremely high rigidity in the X direction, they are integrally connected to the second driven body 20 and parallel to the Moving.

Therefore, the optical axis direction (
For fluctuations in the radial direction (X direction), the objective lens 2 is driven in two directions, and for fluctuations in the radial direction (X direction), both the objective lens 2 and the mirror 7 are driven in the X direction.
No lateral movement occurs in the reflected light (←2) from the optical disk l.

Therefore, the aperture diameter of the objective lens 2 and the luminous flux diameter of the light beam 4 can be made approximately equal, and the loss in the amount of light of the light beam 4 can be reduced.

〔Effect of the invention〕

As explained above, in conventional optical scanning devices,
Lateral movement occurs in the optical axis of the reflected light from the optical disk, making it difficult to accurately control the focal point, and requiring the use of expensive and large objective lenses, or when using inexpensive objective lenses, the amount of light may vary. However, in the optical scanning device of the present invention, the reflected light is reduced by driving the objective lens in the optical axis direction and driving both the objective lens and the mirror in the radial direction of the optical disk. There is no lateral movement of the axis, an inexpensive objective lens can be used, and the loss of light quantity can be reduced, thus solving the above-mentioned drawbacks of the prior art.

[Brief explanation of drawings]

1 and 2 are diagrams each explaining the principle of a conventional optical scanning device, and FIGS. 3 and 4 are diagrams explaining the principle of the present invention,
FIG. 5 is a plan view showing an embodiment of the present invention, FIG. 6 is a longitudinal sectional view of the same, FIG. 7 is an explanatory diagram of the same embodiment driven in the z (+) direction, and FIG. 8 is the same < An explanatory diagram of the drive state in the (+) direction. ...First driven body, 12... Two-way drive coil, (14
-1) to (14-4)...First parallel plate spring,
20...Second driven body, 22...X
Directional drive coils, (24-1) to (24-4)...
...Second parallel leaf spring, 30...Base, 35
...First magnetic circuit, 40...Second magnetic circuit Agent Patent attorney Akio Namiki Figure 1 'N2 Figure 3 Figure 4 Figure g 5 Reason 40 No. 6 Figure 7 Figure n No 0 Figure S

Claims (1)

[Claims] 1) An optical head comprising at least an objective lens for condensing light onto the information recording/reproducing surface of the disk, and first and second mirrors for guiding the light beam from the light source to the objective lens. In an optical scanning device for scanning a disk, the first beam emits the incident light beam parallel to the information recording/reproducing surface of the disk and with the direction changed in the tangential direction of the information track on the surface. A second driven body having at least a mirror mounted thereon is fixed to an external fixed body for receiving the light beam from the first mirror, changing the direction of the beam in the optical axis direction of the objective lens, and emitting the beam. a first driven body on which at least the objective lens is mounted; and means for driving the first driven body in a first direction along the optical axis direction of the objective lens. , comprising a second driving means that interlocks and drives the second driven body and the first driven body in a second direction orthogonal to the first direction. optical scanning device.