JPS61246935A - Optical head - Google Patents

Abstract

PURPOSE:To make a driving device for moving in two directions unnecessary by providing an angle of incidence changing device that changes angle of incidence of luminous flux that goes to points at the same distance from the optical axis of a converging device. CONSTITUTION:By moving a semiconductor laser 21 that generates divergent flux of laser light L in the direction of optical axis, angle of incidence of flux of laser light L that goes to points at the same distance from the optical axis on an objective 25 changes and thereby the position at which the flux of laser light L is converged by the objective 25 moves back and forth in the direction of the optical axis. Accordingly, when an information storing medium 23 gets near the objective 25, the semiconductor laser 21 is brought away from the objective 25, and when the information storing medium 22 gets away from the objective 25, the semiconductor 21 is brought close to the objective 25. Thereby, focused state can be maintained. Accordingly, a driving device for shifting in two directions becomes unnecessary.

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.
There is one configured as shown in the figure. In other words, 1 in the figure
is a semiconductor laser (light source), and a laser beam emitted from this semiconductor laser 1 is focused onto an information storage medium 5 by a sharp objective lens 4 that passes through a half prism 3. 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. A driving device 14 is driven to move the objective lens 4 in the direction of its forward axis.

However, by moving the objective lens 4 in its forward axial 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.

Also, when force tucking is performed using objective lens 4,
Due to dust, scratches, external vibrations, etc. on the information storage medium 5, the force pushing operation cannot be performed, and there is a risk that the objective lens 4 will move instantaneously and collide with the information storage medium 5.

(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 light condensing means and to perform force focusing by a light source. This eliminates the need for a driving device to move the light in the direction, which not only simplifies its structure and adjustment, but also eliminates the need to move the light focusing means in the direction of its optical axis, so even if a focus shift occurs, the light focusing means can be moved. An object of the present invention is to provide an optical head that is free from the risk of colliding with an information storage medium.

[Summary of the invention]

In order to achieve the above object, the present invention changes the angle of incidence of the luminous flux incident on a point on the condensing means at the same distance from the optical axis by moving the light source in the optical axis direction. It is characterized in that it performs force tsusing.

[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 21 (light source), and this semiconductor laser 21 generates a diverging laser beam. Here, when writing information to the information storage medium 22, a laser beam beam 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 constant light intensity is generated. A laser beam is generated having a . And semiconductor laser 2
The diverging laser beam emitted from 1 is guided to the half prism 24, and after passing through the half prism 24, the laser beam guided to the half prism 24 is directed to the objective lens (focusing means) 25. The light is incident on the information storage medium 22 and focused by the objective lens 25 . Here, the semiconductor laser 21 is supported so as to be movable in the optical axis direction, and the objective lens 25 is supported so as to be movable in the direction (radial direction) perpendicular to its front axis.

And semiconductor laser 21. tj and objective lens 25
are positioned at their respective predetermined positions, this objective lens 2
The waist of the focused laser beam emitted from 5 is set on a predetermined tracking guide (
Not shown. ) and a minimum beam spot is formed on the tracking guide. In this state, the semiconductor laser 21 is kept in a focused state, and the objective lens 25 is kept in a focused state, so that writing and reading of information becomes possible. And when writing information,
A bit is formed on a tracking guide 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 used to form a bit on a tracking guide on the information storage medium 22. It is reflected with intensity modulation.

The divergent laser beam reflected from the information storage medium 22 passes through the objective lens 25 and returns to the half prism 24.
will be returned to. The laser beam reflected by the half prism 24 passes through the condensing lens 26 and the cylindrical lens 2.
7 sequentially through the four-divided cells 28a to 28a as shown in FIG.
28d is illuminated 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 objective lens 25 is moved in its radial direction. Further, the focus shift detection signal detected by the photodetector 28 is sent to a force shifting drive circuit 33 via a signal processing circuit 32.
and the force-twisting driving circuit 33 drives the force-twisting driving device 34 according to the signal,
The semiconductor laser 21 is moved in the optical axis direction.

Next, a description will be given of the tracking drive device 31 that moves the objective lens 25 in its radial direction, that is, in the tracking direction.

As shown in FIGS. 3 and 4, the objective lens 25 is held by a holding frame 35, which is attached to the other ends of a pair of parallel plate springs 36, 36, one end of which is fixed. Therefore, the objective lens 25 is movable in its 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 in the vicinity of this movable magnetic body 37, a pair of yokes 38, 38 and a pair of yokes 38 and 38, which surround this and cooperate with this movable magnetic body 37, are provided. A permanent magnet 39° 39 is fixedly arranged. Further, coils 40, 40 are wound around the yokes 38, 38.

The objective lens 25 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-twisting drive device (luminous flux state converting means) 34 for moving the semiconductor laser 21 in the optical axis direction, that is, the force-twisting direction, will be described.

As shown in FIGS. 5 and 6, the semiconductor laser 21
is held by a holding frame 41, which is attached to one end of a pair of support rods 42, 42. Further, the other ends of the support rods 42, 42 are fixed to the middle frame 43. This middle frame 43 is supported by an outer frame 45 via a pair of spiral springs 44, 44, so that the semiconductor laser 21 can be freely displaced in the optical axis direction as shown by the arrow. Roughly speaking, 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 semiconductor laser 21 can be moved by a predetermined amount in the optical axis direction.

Next, the force thudding operation will be explained.

When the semiconductor laser 21 is moved away from the objective lens 25 from the state shown in FIG. 7(a) to as shown in FIG. 7(b), the laser beam passing through the objective lens 25 approaches the objective lens 25. Focuses light at a certain position. Also, Figure 7 (
As shown in C), the semiconductor laser 21 is connected to the objective lens 2.
5, the laser beam passing through the objective lens 25 is focused at a position away from the objective lens 25. That is, by moving the semiconductor laser 21 in the optical axis direction, the angle of incidence of the laser beam that is incident on a point on the objective lens 25 at the same distance from the optical axis changes, and as a result, the angle of incidence of the laser beam beam on the objective lens 25 changes. The position where the light is focused by 25 moves back and forth in the optical axis direction. Therefore, when the information storage medium 22 approaches the objective lens 25, the semiconductor laser 21 is moved away from the objective lens 25, and when the information storage medium 22 moves away from the objective lens 25, the semiconductor laser 21 is moved closer to the objective lens 25. A focused state can be maintained.

According to the above configuration, by moving the semiconductor laser 21 in the optical axis direction, the incident angle of the laser beam incident on a point on the objective lens 25 at the same distance from the optical axis is changed, and thereby the focus is adjusted. Since tracking is performed by the objective lens 25, tracking can be performed by the semiconductor laser 21, and force tracking can be performed by the semiconductor laser 21. Therefore, each drive device 31, 34
Since it is only necessary to move in one direction, its structure and adjustment are simple. Further, since there is no need to move the objective lens 25 in the direction of its front axis, there is no risk that the objective lens 25 will collide with the information storage medium 22 even if a focus shift occurs.

〔Effect of the invention〕

As explained above, according to the present invention, an optical head capable of reading at least information from an information storage medium using focused light includes a light source and a light beam emitted from the light source that is read onto the information storage medium. A light collecting means for collecting light, a photodetector for detecting the light beam emitted from the information storage medium, and changing the angle of incidence of the light flux incident on a point on the light collecting means at the same distance from the optical axis. Since the incident angle variable means is configured to move the light source, tracking can be performed by the condensing means and force focusing can be performed by the light source. 2
This eliminates the need for a driving device to move the light in the direction, which not only simplifies its structure and adjustment, but also eliminates the need to move the light focusing means in the direction of its optical axis. This provides excellent effects such as no risk of collision with the information storage medium.

[Brief explanation of the drawing]

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 drive device for force tweezing, FIG. 6 is a sectional view similarly showing the drive device for force tweezing, FIG. 7 is an explanatory diagram of the force tweezing operation, and FIG. 8 and 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 source, 22... Information storage medium, 25...
Condensing means (objective lens), 28... photodetector, 34.
...Incidence angle variable means (driving device for force thrusting @). Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 Figure 8

Claims (2)

[Claims] (1) A light source capable of reading at least information from an information storage medium using focused light, including a light source, a light condensing means for condensing a luminous flux emitted from the light source onto the information storage medium, and the above-described light source. comprising a photodetector for detecting the light flux emitted from the information storage medium, and an incident angle variable means for changing the incident angle of the light flux incident on a point on the light collecting means at the same distance from the optical axis, An optical head characterized in that the incident angle variable means is configured to move the light source. (2) The optical head according to claim 1, wherein the incident angle variable means is configured to move the light source in the optical axis direction.