JPS61246937A - Optical head - Google Patents

Abstract

PURPOSE:To eliminate possibility of collision of a condensing means against an information storing medium even when focus deviation occurred, by moving a light source block tat emits light source passed through a condenser as divergent light in the direction of the optic axis. CONSTITUTION:When a light source block 21 that emits luminous flux passed through a condenser 21b as divergent light is put away from an objective 25, laser light flux L that passed through the objective 25 is condensed at a position approached the objective 25. When the light source block 21 is brought close to the objective 25, the flux L of laser light that passed through the objective 25 is condensed at a position off from the objective 25. That is, by moving the light source block 21 is the direction of optic axis, angle of incidence of laser light flux L incident to points at equal distance from the optic axis on the objective 25 changes and thereby the position at which laser light flux L is condensed by the objective 25 moves back and forth in the direction of optic axis. Accordingly, the condensing device does not collide against the information recording medium even when focus deviation occurred.

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 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.

Then, the laser beam reflected by the half prism 3 is irradiated onto the photodetector 8, which is provided with four-divided cells 88 to 8b, through the condensing lens 6 and the cylindrical lens 7 in sequence. 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. In addition, the focus shift detection signal detected by the photodetector 8 is supplied to the force shifting drive circuit 13 via the signal processing circuit 12, and the force shifting drive circuit 13 responds 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 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.

In addition, when force shinging is performed using objective lens 4,
Dust, scratches, external vibrations, etc. on the information storage medium 5 may prevent the forcing operation, and there is a risk that the objective lens 4 will move instantaneously and collide with the information storage medium 5.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its purpose is to be able to perform tracking using a light condensing means and force focusing using a light source block, thereby allowing movement in two directions. There is no need for a drive or device to perform this, which simplifies the structure and adjustment, and there is no need to move the condensing means in the direction of its optical axis.
It is an object of the present invention to provide an optical head in which there is no possibility that a light converging means will collide with an information storage medium even if a focus shift occurs.

[Summary of the invention]

In order to achieve the above object, the present invention includes a light source and a condensing lens that condenses the luminous flux emitted from the light source,
By moving the light source block configured to emit the light flux that has passed through the condensing lens in the direction of the optical axis, the light flux is incident on a point on the converging means at the same distance from the optical axis. It is characterized by changing the angle and thereby performing focusing.

[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 light source block, and this light source block 21 includes a semiconductor laser 21a (light source) that generates a diverging laser beam and condenses the laser beam emitted from the semiconductor laser 21a. Condensing lens 21
b, these semiconductor laser 21a and condensing lens 2
It has a frame 21C that integrally supports the laser beam 1b, and is configured to emit the laser light beam that has passed through the condenser lens 21b as diverging light. Here, when writing information to the information storage medium 22, a laser beam whose light intensity is modulated according to the information to be written is generated from the semiconductor laser 21a, and when reading information from the information storage medium 22, A laser beam having a constant light intensity is generated from the semiconductor laser 21a. The diverging laser beam emitted from the light source block 21 is guided to the half prism 24, and after passing through the half prism 24, the laser beam guided to the half prism 24 passes through the objective lens (condenser). means) 25, and the information storage medium 2 is detected by this objective lens 25.
Focused on 2. Here, the light source block 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 the optical axis. When the light source block 21 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 guided to a predetermined tracking guide (not shown) on the information storage medium 22.

) and a minimum beam spot is formed on the tracking guide. In this state, the light source block 21
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 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 pits on the tracking guide on the information storage medium 22. The light intensity is modulated and reflected by the bits formed on the tracking guide.

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 unit M31 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 light source block 21 is moved in the optical axis direction.

Next, a description will be given of the tracking driving mechanism M31 for moving 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 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. Three 39° permanent magnets are fixedly arranged. Further, a coil 40.40 is wound around the yoke 38.38. And coil 40.4
The objective lens 25 can be moved by a predetermined amount in the radial direction by applying a current corresponding to the track deviation to zero.

Next, a force driving device (
The luminous flux state converting means) 34 will be explained.

As shown in FIGS. 5 and 6, the light source block 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 inner frame 43 is connected to the outer frame 4 through a pair of spiral springs 44, 44.
5, so that the light source block 21 can be freely displaced in the optical axis direction 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 light source block 21 can be moved by a predetermined amount in the direction of its optical axis.

Next, the force thudding operation will be explained.

When the light source block 21 is moved away from the objective lens 25 as shown in FIG. 7(b) from the state shown in FIG. 7(a), the laser beam passing through the objective lens 25 approaches the objective lens 25. Focuses light at a certain position. Also, Fig. 7 (C
), when the light source block 21 is brought close to the objective lens 25, 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 light source block 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 that is incident 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 light source block 21 is moved away from the objective lens 25, and when the information storage medium 22 moves away from the objective lens 25, the light source block 21 is moved closer to the objective lens 25. A focused state can be maintained.

According to the above configuration, by moving the light source block 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, thereby causing a force Since tracking is performed by the objective lens 25, tracking can be performed by the light source block 21, and tracking can be performed by the light source block 21.

Therefore, each of the drive devices 31, 34 only needs to move in one direction, which simplifies the structure and adjustment. Furthermore, since there is no need to move the objective lens 25 in the direction of its optical 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, in an optical head capable of reading at least information from an information storage medium using focused light, a light source block and a light beam emitted from the light source block are transmitted to the information storage medium. a light condensing means for condensing light upward; a photodetector for detecting the light beam emitted from the information storage medium; The light source block has a light source and a condensing lens that condenses the light beam emitted from the light source, and converts the light beam that has passed through the condenser lens into diverging light. Since the incident angle variable means is configured to move the light source block, tracking can be performed by the light condensing means and force focusing can be performed by the light source block. This eliminates the need for a driving device to move the light to the center, which simplifies its structure and adjustment, and 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 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 block, 21a... Light source (semiconductor laser), 21t)... Condensing lens, 22... Information storage medium, 25... Condensing means (objective lens), 28.
. . . Photodetector, 34 . . . Incident angle variable means (drive device for force thrusting). Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 GS4 Figure #E51a Figure 6H Figure 7 1c Figure 88 Figure 9

Claims (2)

[Claims] (1) In an apparatus capable of reading at least information from an information storage medium using focused light, a light source block and a light condensing means for condensing a luminous flux emitted from the light source block onto the information storage medium; , comprising a photodetector for detecting the light beam emitted from the information storage medium, and an incident angle variable means for changing the incident angle of the light beam incident on a point on the light collecting means at the same distance from the optical axis. The light source block has a light source and a condensing lens that condenses the luminous flux emitted from the light source, and is configured to emit the luminous flux that has passed through the condensing lens as diverging light, and the incident angle is variable. An optical head characterized in that the means is configured to move the light source block. (2) The optical head according to claim 1, wherein the incident angle variable means is configured to move the light source block in the direction of its optical axis.