JPH0414628A - Optical head device - Google Patents

Abstract

PURPOSE:To make the device small and light in weight by using 1st and 2nd mirrors whose reflecting faces are opposite in parallel and which are subject to drive control integrally with an objective lens so as to introduce a reflected light from a disk to an optical system while the rotary axis of the objective lens and the optical axis are made coincident. CONSTITUTION:A laser beam L outputted from a semiconductor laser 26 is deflected by a half mirror 25 and reaches an objective lens 21 via mirrors 24, 23 and is made incident on a recording track formed on an optical disk at a proper focusing. Then the reflected light from the disk D reaches again the half mirror 25 while the rotary axis of the objective lens and the optical axis are made coincident, is transmitted through the half mirror 25 as it is and made incident on a 2-split detector 28. Thus, an optical head and a servo control actuator are made small and light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical head device that outputs a recording or reading laser beam to a recording medium and detects the reflected light as a reproduction signal. It is.

[Summary of the Invention] The present invention provides an optical head device that obtains a tracking error signal using a push-pull method. A first mirror whose rotation is controlled integrally is provided, and a second mirror whose reflective surface always faces parallel to the first mirror and is located on the rotation axis of the objective lens is provided. A second mirror causes the optical axis of the disk reflected light to substantially coincide with the rotating axis of the objective lens, and the reflected light is introduced into the optical system for detecting the reflected light, so that the optical axis of the disk reflected light is irradiated onto the detector for obtaining a tracking error signal. This is so that the position of the spot will not change due to rotation of the objective lens.

[Prior Art] In optical recording and reproducing devices, the push-pull method and the three-spot (side-spot) method are mainly used as tracking methods to make the beam spot irradiated onto the optical disk accurately follow the track on the optical disk. has been done.

The push-pull method has a simple optical system configuration because only one beam is needed to irradiate the optical disc and there is no need to provide a dedicated detector for tracking error signal detection. However, if the optical head device is constructed by moving only the objective lens in the disk radial direction for tracking control and fixing the other optical systems, the optical head device shown in FIG. 4(a) As shown in FIG. 2, as the objective lens OL moves, the spot SP moves on the two-split detector, for example, as shown by the dotted line.

As a result, a shift due to the DC offset occurs on the tracking error signal as shown in FIG. 4(b), making accurate tracking control difficult.

Therefore, when adopting the push-pull method, it is necessary to integrally drive the objective lens and the optical system for tracking using a swing arm method as shown in FIG.

That is, a semiconductor laser 1, a beam splitter 2, a collimator lens 3, an objective lens 4, and a detector 5 are built into a lens barrel 6 to form an optical system 7, which is mounted at the tip of a rotating arm 9 provided on a base 8. Attach to. A cylindrical excitation coil 10 is fixed to the middle part of the rotating arm 9, and an arc-shaped magnet 12 whose both ends are supported by columns 11 on the base 8 passes through the excitation coil 10. By doing so, the excitation coil 10 becomes the arc-shaped magnet 1
It is possible to move along 2.

In this case, since the positional relationship between the objective lens 4 and the optical system 7 is always constant, the objective lens 4 is
Even if the detector 5 is moved in the radial direction of the disk D,
The spot (disc reflected light) irradiated on the disc does not move.

[Problems to be Solved by the Invention] However, if the optical system is configured with such a swing arm in order to adopt the push-pull method, the configuration of the optical head becomes complicated and the processing of the signal system becomes difficult. In other words, there is a problem in that the advantages of the push-pull method are eliminated.

Furthermore, since the entire optical system is rotated, the rotation mechanism becomes large and responsiveness deteriorates. Furthermore, since the driven portion becomes heavier, power consumption also increases.

[Means for solving the problems] The present invention has been made in view of these problems.
An object of the present invention is to provide an optical head device in which a spot on a detector does not move with respect to movement of an objective lens.

For this purpose, a first mirror that is rotationally controlled integrally with the objective lens that is rotatably supported by a support member is provided on the optical axis of the objective lens, and the reflective surface is rotated together with the first mirror. A second mirror is provided which always faces parallel to each other and is located on the rotation axis of the objective lens, and these first and second mirrors align the optical axis of the disk reflected light approximately with the rotation axis of the objective lens. The optical head device is configured to match the reflected light and introduce it into the optical system for detecting reflected light.

[Operation] As shown in FIG. 1 as a principle diagram, by keeping the first mirror M and the second mirror M2 always parallel to each other, the optical axis of the reflected light from the disk D is aligned with the objective. If the lens OL is made to substantially match the rotational axis J of the lens OL and introduced into the detection optical system (detector Dt) as it is, the optical axis will not change in the optical system due to movement of the objective lens OL.

[Example 1] FIG. 1 shows an example of the optical head device of the present invention.

21 is an objective lens, and 22 is a support member that supports the objective lens 21 so as to be movable in the radial direction of the disk and in the direction perpendicular to the disk surface. That is, objective lens 2
The lens support section 22a on which the lens 1 is mounted is vertically hinge-coupled to the rotating base section 22b at the hinge section H8.
The objective lens 21 is rotatable in the radial direction of the disk D (tracking control direction) with the hinged portion as the rotation axis J, and furthermore, the rotation base 22b is connected to the support portion 22e.
The plate body 22 is connected to the horizontal hinge portion Hb.
c, by being supported via 22d, the disk D
It is possible to move in the direction toward and away from the surface of the board (in the orcus control direction).

23 is a mirror provided at the lower part of the objective lens 21 (on the optical system side), and has a reflecting surface at an angle of 45 degrees with respect to the optical axis of the light passing through the objective lens 21, thereby deflecting the traveling direction of the laser beam by 90 degrees. let This mirror 23 is configured to be driven integrally with the objective lens 21 when it moves in the radial direction of the disk D under tracking control, so that the reflected light from the disk D passes through the objective lens 21 and is then moved to the mirror 23. 23, it is always deflected in the direction of the rotation axis J.

Reference numeral 24 denotes a mirror located on the rotation axis J, and the mirror 24 and the mirror 23 face each other with their respective reflecting surfaces always kept in a parallel state. In other words, the mirror 24 is rotated integrally with the mirror 23 on the rotation axis J as the objective lens 21 is rotated. The traveling direction of the laser beam is deflected by 90 degrees by this mirror 24, so that the disk D
The optical axis of the reflected light from the rotation axis J substantially coincides with the rotation axis J.

25 is a half mirror; 126 is an optical system such as a beam splitter and a collimator lens; 27 is a semiconductor laser; and 28 is a two-split detector.

In the optical head device configured in this way, the laser beam output from the semiconductor laser 27 is deflected by the half mirror 25, and further by the mirror 24. mirror 2
3, the light beam reaches the objective lens 22, and is incident on the recording track formed on the optical disk D in a proper focused state. Then, the reflected light from the disk D passes through the objective lens 21 again, is deflected by the mirrors 23 and 24, reaches the half mirror 25 with the optical axis aligned with the rotation axis J, and is transmitted through the half mirror 25 as it is. and enters the two-split detector 28. It is well known that a tracking error signal can be obtained by taking the difference between the detection outputs of the divided detectors.

In this embodiment, even if the objective lens 21 moves in the tracking direction, the optical axis of the reflected light reaching the optical system is always rotated due to the action of the mirrors 23 and 24 that move at the same time. The spot that is irradiated onto the two-split detector 28, which coincides with the axis J, rotates as the objective lens moves, but its irradiation position does not change. Therefore, it is not necessary to drive the entire optical system by the swing arm mechanism, and the optical head device and the servo control actuator can be made smaller and lighter. Note that when the reflected light whose rotational axis and optical axis are aligned with each other by the mirror 24 passes through the half mirror 25,
Depending on the thickness of the half mirror 25, it will be slightly offset from the rotation axis as shown in the figure, but the two-split detector 2
8 is arranged taking into account the deviation of the optical axis, there is no particular problem.

FIG. 3 shows another embodiment of the present invention, in which the optical system is constructed from an integrated light emitting/receiving composite element. That is, the optical system 30 includes a detector, a semiconductor laser element, and a laser beam emitted by the semiconductor laser element on a semiconductor substrate, and guides the laser light emitted by the semiconductor laser element to the outside so that it is incident on an optical disk, and also directs the reflected light from the optical disk to a photodetector. A device equipped with a guiding prism is used.

In the case of this embodiment as well, the same effects as in the embodiment shown in FIG. It becomes possible to do so.

In addition, in the embodiments shown in FIGS. 2 and 3, the mirror 2
Although the reflective surface in 3.24 was explained as 45°, the rotation axis J
If the optical axis of the reflected light coincides with the angle of 45°, each reflecting surface is
It doesn't have to be.

[Effects of the Invention] As explained above, in the optical head device of the present invention, the rotation from the disk is controlled by the first and second mirrors whose rotation is controlled integrally with the objective lens and whose reflecting surfaces are parallel to each other. Since the reflected light is introduced into the detection optical system with the rotational axis of the objective lens and the optical axis approximately aligned, the spot position on the detector does not change due to the movement of the objective lens, and the tracking error signal is No shift occurs. Therefore, with the optical head device of the present invention, it is possible to use a method of driving only the objective lens to perform servo control in combination with a push-pull method, which simplifies the configuration, reduces size and weight, and design of the optical recording/reproducing device. This has the excellent effect of making it easier.

[Brief explanation of the drawing]

FIG. 1 is a detailed explanation of the principle of the present invention, and FIG. 2 is an explanatory diagram of an embodiment of the optical head device of the present invention. FIG. 3 is an explanatory diagram of another embodiment of the optical head device of the present invention, and FIGS. 4(a) and 4(b) show spot movement on the detector and tracking error signal D
FIG. 5 is an explanatory diagram of a swing arm type actuator. 21 is an objective lens, 22 is a support member, 23°, 24 is a mirror, 25 is a half mirror, and 127 is a semiconductor laser 1.28
30 is a two-split detector, 30 is an integrated light emitting/receiving composite element,
J indicates the rotation axis.

Claims (1)

[Claims] A tracking error signal is obtained by a push-pull method,
In an optical head device that performs tracking control by rotating an objective lens rotatably supported by an objective lens support member in a disk radial direction based on the tracking error signal, the objective lens and a first mirror that is located on the rotation axis of the objective lens and is rotated together with the first mirror, and whose reflective surface is aligned with the first mirror. and a second mirror that always faces parallel to each other, and the second mirror causes the optical axis of the disk reflected light to substantially coincide with the rotating axis of the objective lens, and introduces the reflected light into the optical system for detecting the reflected light. An optical head device characterized by: