JPH01229434A - Focusing mechanism and optical pickup - Google Patents

Abstract

PURPOSE:To decrease the strokes of an actuator and to reduce the scale of a focusing mechanism by setting a mirror between a light source and a lens and displacing the mirror. CONSTITUTION:The divergent light emitted from a semiconductor laser 101 is made incident on a mirror 103 with the optical path bent by a beam splitter 102. The light reflected by the mirror is transmitted through the splitter 102 and condensed at an image forming position 105 by a lens 104. In this case, the mirror 103 can be moved toward an optical axis 107 by an actuator 106. As for the actuator 106, an electromagnetic type including a permanent magnet and a coil or a piezoelectric element, etc., are used. In such a constitution, the displacement value of a spot light source is reduced and the scale of a focusing mechanism can be reduced.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a focusing mechanism for displacing the imaging position of a lens in the optical axis direction of the lens, and an optical system for recording and reproducing information using light. Regarding the structure of pickup.

[Prior Art] As an example of a conventional focusing mechanism and an optical pickup equipped with the same, there is one that utilizes the imaging relationship of a lens such that the time aperture a=62-66428. The principle of this focusing mechanism will be briefly explained using FIG. 7. The distance from the point light source 7o2 to the objective lens 701 is a
, the distance from the objective lens 701 to the imaging position 703 is b
In this case, if the focal length of the objective lens 701 is f, there is a relationship of 1 / a + 1 / b = 1 / f, so by displacing the point light source 702 in the optical axis direction 7 degrees 4, the image can be formed. The fact that the position 703 can be displaced in the optical axis direction is utilized.

[Problem to be Solved by the Invention] However, in the above-mentioned conventional technology, the amount of displacement of the image forming position 703 is reduced to about a fraction of the amount of displacement of the point light source 7°2 due to the magnification of the lens 701. A problem arises in that the amount of displacement of the point light source 7°2 for obtaining the amount of displacement of the imaging position 703 becomes large, and the focusing mechanism becomes large.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a compact focusing mechanism that reduces the amount of displacement of a point light source.

Furthermore, since the conventional focusing mechanism is large as described above, when used as a focusing mechanism for an optical pickup, it has the problem of hindering miniaturization of the optical pickup.

Another object of the present invention is to provide an optical pickup that allows high-speed access and is miniaturized.

[Means for Solving the Problems] The focusing mechanism of the present invention includes a light source, a lens that focuses light from the light source, and a mirror that reflects the light from the light source and guides it to the lens as main components. The lens is characterized in that the mirror is displaced in the optical axis direction of the lens.

Further, the optical pickup of the present invention is characterized in that it includes the above-mentioned focusing mechanism.

[Operation] According to the above configuration of the present invention, by displacing the mirror that reflects the light from the light source and guiding it to the lens in the optical axis direction of the lens, the change in the distance between the light source and the lens is reduced by the amount of displacement of the mirror. This is doubled, and the displacement of the imaging position where the light from the light source is focused by the lens can be obtained with a small mechanical displacement.

Hereinafter, the details of the present invention will be shown by examples.

Embodiment 1 FIG. 1 is a sectional view of the main structure of a first embodiment of a focusing mechanism of the present invention.

The divergent light emitted from the semiconductor laser 101 has its optical path bent by the beam splitter 102 and enters the mirror 103 +:.

The light reflected by the mirror passes through the beam splitter 102 and is focused on an imaging position 105 by a lens 104.

Mirror 103 can be moved in optical axis direction 107 by actuator 106 . Actuator 10
As 7, an electromagnetic type composed of a permanent magnet and a coil, or a type composed of a piezoelectric element, etc. can be used.

Next, the principle of the focusing mechanism of the present invention will be explained using FIG. Note that the same elements as in FIG. 1 are indicated by the same numbers as in FIG.

Displacement amount S of the mirror 103 by the actuator 105
When the beam is moved away from the tin l/ivy 102 by 2 seconds, the distance between the semiconductor laser 101 as the light source and the lens 104 increases by 2 seconds, and the position of the light source moves away from the lens 104.
approaches the lens 104 side from the position 105 where it is not displaced (202). Conversely, by bringing the mirror 103 closer to the beam splitter 102, the imaging position 105 can be moved away from the lens 104. Note that the dotted line in FIG. 2 indicates the mirror 10 when the mirror 103 is not displaced.
3 represents the position and rays of light.

Embodiment 2 FIG. 3 is a sectional view of the main components of a second embodiment of the focusing mechanism of the present invention.

Divergent light from the semiconductor laser 101 is transmitted to the beam splitter 1
After passing through the beam 02 and being reflected by the mirror 103, the beam passes through the beam splitter 102 and is converted into parallel light 302 by the collimator lens 301. This parallel light 302 is transmitted through the lens 30
3, the light is focused on an imaging position 304. Also in this embodiment, the imaging position 304 can be displaced in the optical axis direction by the displacement 107 of the mirror 103.

Embodiment 3 FIG. 4 is a sectional view of the main structure of a third embodiment of the focusing mechanism of the present invention.

The light from the semiconductor laser 101 is transmitted through a single mode optical fiber 401. The tip of the optical fiber 401 is fixed with a glass plate 402. The diverging light emitted from the optical fiber 401 is reflected by the mirror 103 and passes through the glass plate 402, and then is focused by the lens 403 onto the imaging position 404.

In this case as well, by displacing the mirror 103 in the optical axis direction 107 with the actuator 106, the imaging position 404 can be displaced in the optical axis direction.

Embodiment 4 FIG. 5 is a main configuration diagram of one embodiment of the optical pickup of the present invention, in which (a) is a plan view and (b) is a sectional view of a part of (a).

Light emitted from a semiconductor laser 501 attached to a housing 502 passes through a beam splitter 503, is once focused by a lens 504, passes through a focusing point 505, diverges again, and is guided to a mirror 508 by a beam splitter 506. lens 5
A pinhole 507 is placed at the focal point 505 created by 04.

The light reflected by the mirror 508 returns to the beam splitter 5.
06, is reflected by a flip-up mirror 509, and is focused onto a recording medium 511 by an objective lens 510. The recording medium 5 is
Information can be recorded on the recording medium 511, and information can be reproduced from the light reflected by the recording medium 511. The reflected light from the recording medium 511 passes through the objective lens 510, flip-up mirror 509, beam splitter 506, and mirror 50.
8. The optical path is bent by the beam splitter 503 through the pinhole 507 and the lens 504, and the light passes through the lens 513 and enters the photodiode 514, where it is converted into an electrical signal and information on the recording medium can be detected.

FIG. 5(b) is a cross-sectional view of FIG. 5(a) including the mirror 508, beam splitter 506, flip-up mirror 509, and objective lens 510.

If the focused spot 512 formed by the objective lens 510 deviates from the surface of the recording medium 511 due to surface fluctuation of the recording medium 511, the deviation can be obtained from the output of the photodiode 514, and the deviation can be corrected. mirror 508 to align the condensed spot 512 with the surface of the recording medium.
is displaced in the optical axis direction 516 by an actuator 515. This mechanism is described in Example 1 or Example 2. A focal point 505 formed by a lens 504 corresponds to the position of the semiconductor laser in the first or second embodiment.

On the other hand, if the focused spot 512 by the objective lens 510 deviates from the desired track on the recording medium 511, the deviation can be obtained from the output of the photodiode 514, and the deviation can be corrected. to move the focused spot 512 to a desired track.
The flip-up mirror 509 is slightly rotated 518 by the actuator 517 to make the focused spot 51 as shown by the dotted line.
Move to 9.

The recording medium 511 in this embodiment is fixed to a spindle 520 and rotates, and the optical pickup casing 50
2 is moved in the radial direction of the recording medium 511 by a voice coil motor (not shown) (521).

The pinhole 507 used in this example is to prevent unnecessary light from the mirror 508 from returning to the photodiode 514, and the combination of a polarizing beam splitter and a wavelength plate prevents the light returning to the photodiode. You can suppress it.

Embodiment 5 FIG. 6 is a main configuration diagram of another embodiment of the optical pickup of the present invention, in which (a) is a plan view and (b) is a sectional view of a part of (a). Embodiment 4 of FIG. 5 in FIG.
Similar elements are labeled with the same numbers as in FIG.

Light emitted from a semiconductor laser 501 attached to a housing 502 passes through a beam splitter 503 and is focused by a lens 504, and the optical path is bent by a mirror 601 to reach a focusing point 50.
5 and diverges again, and is guided to a mirror 508 by a beam splitter 506.

The light reflected by the mirror 508 returns to the beam splitter 5.
06, passes through a collimator lens 602, a rotatable mirror 603, and a flip-up mirror 607 fixed to another housing 606, and is focused onto a recording medium 511 by an objective lens 510. A pinhole 507 is placed at a focal point 505 formed by a lens 504. The reflected light from the recording medium 511 is reflected by the objective lens 510 and the flip-up mirror 607.
, a rotatable mirror 604, a collimator lens 602,
Beam splitter 506, mirror 508, pinhole 5
07, returns to mirror 601 and lens 504, has its optical path bent by beam splitter 503, passes through lens 513, and is detected by photodiode 514.

A housing 502 containing a semiconductor laser 501, a photodiode 514, etc. is fixed to a recording/reproducing device, and a housing 606 is fixed to a flip-up mirror 607 and an objective lens 510.
Although not shown in the figure, the voice coil motor sends the signal to a desired track on the recording medium 511 (608).
.

Focusing, which causes the focused spot 512 by the objective lens 510 to always follow the surface of the recording medium, can be performed using the same mechanism as in the fourth embodiment.

In order to make the focused spot 512 by the objective lens 510 always follow the track of the recording medium 511, the rotatable mirror 603 is slightly rotated by the actuator 604 (
605) to move the focused spot created by the objective lens to 609 as shown by the dotted line.

In the optical pickup of this embodiment, only the objective lens 510 and the housing 606 to which the flip-up mirror 607 is fixed are moved when sending the focused spot 512 created by the objective lens 510 due to the stress of recording and reproducing information. The weight is significantly reduced, and the access time as a recording/playback device is reduced by 2.
It is possible to shorten the length to about 0 to 30 m5ec.

Although the embodiments have been described above, the present invention can be applied not only to the above embodiments but also to various optical pickups.

For example, if the present invention is applied to an optical pickup having a function of detecting the rotation of polarized light, it is possible to construct an optical pickup for so-called magneto-optical recording that allows high-speed access.

Furthermore, the present invention is applicable not only to optical pickups but also to systems requiring a focusing mechanism such as laser beam printers.

[Effects of the Invention] As described above, according to the present invention, by displacing the mirror between the light source and the lens, the stroke of the actuator that must be moved to obtain the necessary displacement of the imaging position is reduced. This type of focusing mechanism has the effect of being able to miniaturize the focusing mechanism.In addition, when accessing such a focusing mechanism, the only thing that needs to be moved when accessing it is the objective lens and the casing to which the mirror is fixed. By using this method, it is possible to construct an optical pickup that is small and capable of high-speed access.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main components of a first embodiment of the focusing mechanism of the present invention. FIG. 2 is a sectional view showing the principle of the focusing mechanism of the present invention. FIG. 3 is a sectional view of the main components of the second embodiment of the present invention. This is a main configuration diagram of one embodiment of the optical pickup; FIG. 6(a) is a plan view, and FIG. 6(b) is a diagram of the main configuration of another embodiment of the optical pickup. A partial cross-sectional view. FIG. 7 is a sectional view of the main parts of a conventional focusing R structure. 101... Semiconductor laser 102... Beam splitter 103... Mirror 104... Lens 105... Imaging position 106... Actuator 107... Optical axis direction 201... Imaging position 202. ...Movement of the imaging position 301 ...Collimator lens 302 ...Parallel light 303 ...Lens 304 ...Image formation position 401 ...Optical fiber 402 ...Glass plate 403 ...Lens 404. ...Image position 501...Semiconductor laser 502...Casing 503...Beam splitter 504...Lens 505...Focusing point 506...Beam splitter 507...Pinhole 508...・Mirror 509...Flip-up mirror 510...Cow lens 511...Recording medium 512...Focusing spot 513...Lens 514...Photodiode 515...Actuator 516...Mirror Movement direction 517...Actuator 518...Flip-up mirror rotation direction 519...Focusing spot 520...Spindle 521...Optical pickup access direction 601
... Mirror 602 ... Collimator lens 603 ... Rotatable mirror 604 ... Actuator 605 ... Rotatable mirror rotation direction 606 ...
Housing 607...Flip-up mirror 608...Access direction 609...Light focus spot or above Applicant Seiko Epson Corporation Representative Patent Attorney Mogami Tsutomu 1 person o7 /I! 76 ''' Figure 2 (b) (Kun

Claims (2)

[Claims] (1) The main components include a light source, a lens that condenses light from the light source, and a mirror that reflects the light from the light source and guides it to the lens, and the mirror is displaced in the optical axis direction of the lens. A focusing mechanism that is characterized by the ability to (2) An optical pickup comprising the focusing mechanism described in item 1.