JPS61269243A - Optical head - Google Patents

Abstract

PURPOSE:To simplify construction and adjustment by providing means for varying an injection direction which changes the injection direction of a luminous flux from a collimating means. CONSTITUTION:A track devication detection signal detected by a photodetector 28 is supplied via a signal processing circuit 29 to a driving circuit 30 for tracking. The circuit 30 drives a driving device 31 for tracking according to said signal to move a collimating lens 23 in the diametral direction thereof. The out-of-focus detection signal detected by the photodetector 28 is supplied via a signal processing circuit 32 to a driving circuit 33 for focusing. The circuit 33 drives a driving device 34 for focusing according to said signal to move an objective lens 25 in the optical axis direction thereof. The need for a driving device for movement in two directions is thereby eliminated and the construction and adjustment thereof are simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical head used in, for example, an optical disk device.

[Technical background of the invention and its problems]

Conventionally, the optical heads of the above type are shown in FIGS. 8 and 9.
Those configured as shown in the figure will compete. In other words, 1 in the figure
is a semiconductor laser (light source), and the laser beam emitted from this semiconductor laser 1 is passed through a collimating lens 2.
and the objective lens 4 after passing through the half prism 3 in sequence.
is focused onto the information storage medium 5 by. Further, the laser beam reflected from the information storage medium 5 passes through the objective lens 4 again and is returned to the half prism 3.

The laser beam reflected by the half prism 3 passes through a condenser lens 6 and a cylindrical lens 7 in order and is irradiated onto a photodetector 8 having four divided cells 8a to 8b. As a result, information signal detection, track deviation detection, and defocus detection are performed.

Further, the track deviation detection signal detected by the photodetector 8 is sent to the tracking drive circuit 1 via the signal processing circuit 9.
According to the signal, the tracking drive circuit 10 drives the tracking drive device 11 to move the objective lens 4 in its radial direction. Further, the focus shift detection signal detected by the photodetector 8 is supplied to the force-twisting drive circuit 13 via the signal processing circuit 12, and the force-twisting drive circuit 13 performs the force-twisting according to the signal. The objective lens 4 is moved in the direction of its optical axis by driving the optical drive device 14.

However, by moving the objective lens 4 in its optical axis direction, force tracking is performed, and by moving it in its radial direction, tracking is performed.

Therefore, the objective lens 4 can be
A driving device is required to move the device in each direction independently, and its structure and adjustment are difficult.

(Object of the Invention) The present invention has been made based on the above-mentioned circumstances, and its object is to be able to perform tracking by a collimating means and to perform force focusing by a condensing means. It is an object of the present invention to provide an optical head that does not require a drive device for movement in two directions and whose structure and adjustment are simple.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized in that tracking is performed by changing the direction of emission of the light beam from the collimating means.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 7.

Reference numeral 21 in FIG. 1 is a semiconductor laser (light source), and this semiconductor laser 21 generates a divergent laser beam beam. In this case, when writing information to the information storage medium 22, a beam of laser light whose light intensity is modulated according to the information to be written is generated, and when reading information from the information storage medium 22, a beam of light with a constant light intensity is generated. A laser beam is generated having a . And the semiconductor laser 21
The diverging laser beam generated by the laser beam is converted into a parallel beam by a collimating lens (parallelizing means) 23 and guided to a half prism 24 . After passing through the half prism 24, the laser beam guided to the half prism 24 enters an objective lens (focusing means) 25, and is focused by the objective lens 25 toward the information storage medium 22. Here, the collimating lens 23 is supported so as to be movable in a direction (radial direction) orthogonal to its optical axis direction, and the objective lens 25 is supported so as to be movable in its front axis direction. And collimating lens 2
3 and the objective lens 25 are respectively positioned at predetermined positions, the beam waist of the focused laser beam emitted from the objective lens 25 is directed to a predetermined tracking guide 22a (see FIG. 7) on the information storage medium 22. A minimum beam spot is formed on the tracking guide 22a. In this state, the collimating lens 23 is maintained in a focused state, and the objective lens 25 is maintained in an in-track state, making it possible to write and read information. When writing information, pits are formed on the tracking guide 22a on the information storage medium 22 by a laser beam whose intensity is modulated, and when reading information, a laser beam having a constant light intensity is formed. , the light intensity is modulated by the bits formed on the tracking guide 22a and reflected.

The diverging laser beam reflected from the information storage medium 22 is focused by the objective lens 2 when the collimating lens 23 focuses.
5, it is converted into a parallel beam by half prism 2.
Returned to 4. The laser beam reflected by the half prism 24 passes through a condensing lens 26 and a cylindrical lens 27 in order to form a four-part cell 28a as shown in FIG.
~28d onto a photodetector 28. As a result, information signal detection, track deviation detection, and defocus detection are performed.

Further, the track deviation detection signal detected by the photodetector 28 is supplied to the tracking drive circuit 30 via the signal processing circuit 29, and the tracking drive circuit 30 drives the tracking drive device 31 according to the signal. Then, the collimating lens 23 is moved in its radial direction. Also,
The focus shift detection signal detected by the photodetector 28 is supplied to the force-twisting drive circuit 33 via the signal processing circuit 32, and the force-twisting drive circuit 33 drives the force-twisting in accordance with the signal. The device 34 is driven to move the objective lens 25 in the direction of its optical axis.

Next, a description will be given of the tracking drive means (variable ejection direction means) 31 for moving the collimating lens 23 in its radial direction, that is, in the tracking direction.

As shown in FIGS. 3 and 4, the collimating lens 2
3 is held by a holding frame 35, and this holding frame 35 is attached to the other end of a pair of parallel leaf springs 36.degree. 36, one end of which is fixed. Therefore, the collimating lens 23 is movable in the radial direction, that is, in the tracking direction, as shown by the arrow. Further, the holding frame 35 is provided with a movable magnetic body 37, and a pair of yokes 38, 38 and a pair of yokes 38 and 38 that surround the movable magnetic body 37 and cooperate with the movable magnetic body 37 are provided in the vicinity of the movable magnetic body 37. Permanent magnet 39.
39 are fixedly arranged. Also, yoke 38.3
8 is wound with a coil 40.40. The collimating lens 23 can be moved by a predetermined amount in the radial direction by passing a current corresponding to the track deviation through the coils 40 and 40.

Next, the force pushing drive device 34 for moving the objective lens 25 in its front axis direction, that is, in the force pushing direction, will be described.

As shown in FIGS. 5 and 6, the objective lens 25 is held by a holding frame 41, which is supported by a pair of support rods 4.
2.42 is attached to one end. Further, the other ends of the support rods 42, 42 are fixed to the middle frame 43. This inner frame 43 is connected to the outer frame 45 via a pair of spiral springs 44, 44.
This allows the objective lens 25 to be freely displaced in the direction of its front axis, as shown by the arrow. Further, a coil 47 is attached to the inner frame 43 via a ring 46, while a permanent magnet 48 and yokes 49, 49, which cooperate with the coil 47, are attached to the outer frame 45.

By passing a current corresponding to the focus shift through the coil 47, the objective lens 25 can be moved by a predetermined amount in the direction of its optical axis.

Next, the tracking operation will be explained.

For example, from the focused state shown in FIG. 7(a), to the focused state shown in FIG. 7(b),
), when the collimating lens 23 is moved upward in the figure, the emission direction of the laser beam from the collimating lens 23 is tilted in the moving direction of the collimating lens 23, that is, upward in the figure, and the laser beam passes through the objective lens 25. The laser beam is focused in the moving direction of the collimator lens 23, that is, at a position shifted upward in the figure. Furthermore, as shown in FIG. 7(C), when the collimating lens 23 is moved downward in the figure, the direction of emission of the laser beam from the collimating lens 23 is the same as the moving direction of the collimating lens 23, that is, downward in the figure. The laser beam that has passed through the objective lens 25 is focused at a position shifted downward in the figure in the direction of movement of the collimating lens 23. That is, by moving the collimating lens 23 in a direction perpendicular to the optical axis direction, the direction of emission of the laser beam from the collimating lens 23 is changed, and the position where the laser beam is focused by the objective lens 25 is aligned with the optical axis. Shift in the direction perpendicular to the direction. Therefore, when the tracking guide 22a of the information storage medium 22 shifts upward in the figure, the collimating lens 22a
When the tracking guide 22a of the information storage medium 22 is shifted downward in the figure, the collimating lens 23 is moved in the direction in which the tracking guide 22a is displaced, that is, upward in the figure. Tracking can be performed by moving the

According to the above configuration, the collimating lens 23 is moved in the direction orthogonal to the front axis direction, and the collimating lens 23 is
Since tracking is performed by changing the direction of emission of the laser beam from the laser beam, tracking can be performed by the collimating lens 23, and tracking can be performed by the objective lens 25, respectively. therefore,
Since each drive device 31, 34 only needs to move in one direction, its structure and adjustment are simplified. Further, the objective lens 25 is a tracking guide 22a.
Since the direction is fixed, the spot is not disturbed by the influence of the luminance distribution of the parallel incident light beam.

〔Effect of the invention〕

As explained above, according to the present invention, there are provided a collimating means for collimating the light emitted from the light source, and a condensing means for condensing the light collimated by the collimating means onto the information storage medium. and a photodetector for detecting light that is focused on the information storage medium by the light focusing means and reflected or transmitted from the information storage medium, the optical head changing the emission direction of the light beam from the collimating means. Since the injection direction variable means is provided, tracking can be done by parallelizing means,
Forcing force can be performed by the condensing means, which eliminates the need for a drive device for moving the ball in two directions, and provides excellent effects such as simplifying its structure and adjustment. .

[Brief explanation of drawings]

Figures 1 to 7 show one embodiment of the present invention.
The figure is a schematic configuration diagram of the optical head, Figure 2 is a front view of the photodetector, Figure 3 is a plan view of the tracking drive, and Figure 4 is a sectional view of the tracking drive. , FIG. 5 is a partially sectional plan view of the force shinging drive device, FIG. 6 is a cross-sectional view of the force shinging drive device, and FIGS. 7(a) to (C) are tracking operations. FIG. 8 and FIG. 9 show a conventional example. FIG. 8 is a schematic configuration diagram of an optical head, and FIG. 9 is a front view of a photodetector. 21... Light 1 (semiconductor laser), 22... Information storage medium, 23... Collimating means (collimating lens),
25... Focusing means (objective lens), 28-... Photodetector, 31... Emission direction variable means (tracking drive device). Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 (C) Figure 7

Claims (2)

[Claims] (1) A collimating means for collimating the light emitted from the light source, a condensing means for condensing the collimated light by the collimating means on the information storage medium, and the information storage by the condensing means. and a photodetector for detecting light that is focused on a medium and reflected or transmitted from the information storage medium, further comprising an emission direction variable means for changing the emission direction of the light from the collimating means. Features an optical head. (2) The optical head according to claim 1, wherein the emission direction variable means is configured to move the collimating means in a direction perpendicular to the optical axis direction thereof.