JPH0827970B2 - Optical disk drive - Google Patents

Description

The present invention relates to an optical disk device such as a magneto-optical disk device for recording / reproducing information with a laser beam from a laser recording / reproducing device.

(Prior Art) In general, a laser recording / reproducing device (hereinafter abbreviated as an optical pickup) of a magneto-optical disk device has a complicated signal detection optical system, which increases the weight of the entire optical pickup and realizes high-speed access. It is a big problem when doing.

Therefore, the objective lens of this optical pickup, the actuator for driving the same, the beam raising prism, etc. are mounted on the feed mechanism to form a movable part unit that moves in the radial direction of the disc, and the fixed part unit that is the other part of the optical pickup is There is known a separation type optical system in which the weight of a movable unit is significantly reduced by fixing it to the base of a disk device, and it is possible to reduce access time and power consumption at that time. An example of this separation type optical system will be described with reference to FIG.

FIG. 2 is a configuration diagram showing an example of a conventional magneto-optical disk device. FIG. 2A is a side view and FIG. 2B is a plan view.

As shown in the figure, the conventional magneto-optical disk device 31 is
The cartridge 3 includes a magneto-optical disk 2, a feed device 5, a base 34, an optical pickup 36, and the like.

As shown in FIG. 3A, the laser light 12 emitted from the fixed unit 36-1 of the optical pickup 36 fixed to the base 34 is emitted from the optical pickup 36 movable in the arrow 5A direction by the feed device 5. The light enters the movable unit 6-2, is turned upward at a right angle by the beam raising prism 13, is focused by the objective lens 14, and is radiated to the disc 2 in a just-focused state by the objective lens driving actuator 15.

Due to the structure of the separation type optical system in the disk device 31, the moving direction (feed direction) 5A of the movable unit 6-2 and the optical axis of the laser beam 12 emitted from the fixed unit 36-1. The directions must match, which considerably limits the optical path design of the optical pickup 36.

As shown in FIG. 3B, the laser light emitted from the semiconductor laser 7 is high-frequency modulated by the high-frequency superimposing circuit 8 arranged on the back surface of the semiconductor laser 7 during reproduction, and is collimated by the collimator lens 9. After, beam shaping prism 40
Is incident on. Since the laser light emitted from the semiconductor laser 7 has a substantially elliptical cross section, this cross-sectional shape is shaped into a substantially circular shape by the beam shaping prism 40. The laser light emitted from the prism 40 enters the beam raising prism 13 via the beam splitter 11, is reflected there, and enters the objective lens 14. The objective lens 14 focuses and irradiates the laser beam on the magneto-optical disk 2.

The reflected light from the disc 2 is incident on the beam splitter 11 via the objective lens 14 and the raising prism 13.
It is reflected by the division surface 11A and heads for the signal detection system. That is, this reflected light, after passing through the half-wave plate 16, is partially reflected by the polarization beam splitter 17, and the total reflection prism 1
8, through the condenser lens 19A, the cylindrical lens 20, converted into an electrical signal by the photodiode 21A and output as a detection signal, and the rest passes through the polarization beam splitter 17 and passes through the condenser lens 19B. Then, it is converted into an electric signal by the photodiode 21B and output as a detection signal, and a reproduction RF signal is obtained from the difference between the both detection signals. The two photodiodes 21A and 21B are arranged on the same side surface side in the fixed unit 36-1.

(Problems to be Solved by the Invention) In the separation type optical system as described above, (1) even when the movable unit 6-2 is transferred to the outermost periphery of the disk 2, the fixed unit 36- Do not collide with 1. (2) The optical system can be adjusted even when the disc is mounted. (3) As described above, the movable unit 6
As shown in FIG. 2 (B), the transfer direction 5A of −2 and the optical axis direction of the laser beam 12 emitted from the fixed unit 36-1 must match. The fixed unit 36-1 will stick out from the disc 2 or the cartridge 3 in at least one direction. For example, in this figure, the fixing unit 36-1 is arranged in the transfer direction with respect to the cartridge 3.
Only dimension L ₃ protrudes in the 5A direction.

Therefore, as is clear from the figure, in the magneto-optical disk device 31 using such a separation type optical system, the length in the transfer direction 5A is set to the diameter of the disk 2 (or the length of the cartridge 3). Overhanging length L ₃ of the fixed unit 36-1
Cannot be shorter than the length added. On the other hand, the width of the disk device 31 in the width direction W perpendicular to the transfer direction 5A is the diameter of the disk 2 (or the width of the cartridge 3).
W ₂₎ or it has been said that can not be less than the larger width W ₃ of the fixed section unit 36-1, was present amount of restriction in constituting the entire apparatus.

The present invention has been made in view of the above points, and provides an optical disc device that is miniaturized by suppressing the protrusion amount of the fixed unit of the optical pickup using the separation type optical system in the moving direction of the movable unit. It is intended to be provided.

(Means for Solving the Problems) An optical disc of the present invention is provided with at least a semiconductor laser that emits a laser beam, a collimator lens that collimates emitted light from the semiconductor laser, and an information signal from a movable unit. A fixed unit including a beam splitter that sends reflected light to the signal detection system; an objective lens that focuses the laser light on the recording surface of the optical disc to obtain the reflected light; and a light flux from the fixed unit. An optical disk device for recording / reproducing information on / from the optical disk by a laser recording / reproducing device including a movable unit including a beam rising prism guided to the objective lens, wherein the semiconductor laser and the collimator lens are: Make an angle of less than 90 degrees with the optical axis of the laser beam from the fixed unit to the movable unit. Disposed above, having a first surface and a second surface between the collimator lens and the beam splitter, and the emitted light refracted and incident from the first surface is the second surface. The angle between the optical axis that is incident on the surface at a critical angle or more and is totally reflected in the same direction as the refraction direction and that is incident on the first surface and the optical axis that is totally reflected on the second surface is The prism is configured to change the optical axis direction of the laser light at an angle of less than 90 degrees.

(Example) The optical disk device of the present invention is an optical pickup using the above-mentioned separation type optical system, and an optical axis direction changing means such as a total reflection prism is provided between the conformer lens and the beam splitter. The above-mentioned object is achieved by arranging them and setting the angle formed by the optical axis of the emitted light from the semiconductor laser and the optical axis of the reflected light from the movable unit to be less than 90 degrees.

An embodiment of the present invention will be compared and described under the same conditions as in the case of the above-mentioned conventional example.

FIG. 1 is a block diagram showing an example of a magneto-optical disk device which is an embodiment of the optical disk device of the present invention.
Is a side view, and FIG. 2B is a plan view.

As shown in the drawing, a magneto-optical disk device 1 according to an embodiment of the present invention includes the magneto-optical disk 2, the base 4, the feed device 5, a fixed unit 6-1 and the movable member housed in the cartridge 3. The optical pickup 6 and the like including the sub-unit 6-2.

As described above, this disc device 1 is different from the disc device 31 of the above-mentioned conventional example in that the beam shaping prism 40 and the optical axis of the laser beam are provided between the collimating lens 9 and the split surface 11A of the beam splitter 11. A composite prism 10 in which a total reflection prism for changing the direction is integrated is arranged (in this embodiment, an example in which the beam splitter 11 is also integrated with the composite prism 10 is shown), and the output from the semiconductor laser 7 is set. Since the angle θ formed by the optical axis of the emitted light and the optical axis of the reflected light from the movable unit 6-2 is set to less than 90 degrees, the same parts as those in the conventional example are The description is omitted.

The composite prism 10 includes a beam shaping unit 10A and a total reflection unit 10B.

The laser light emitted from the collimator lens 9 is
In this beam shaping unit 10A, similar to the case of the beam shaping prism 40 in the above-mentioned conventional example, the beam shaping unit 10A
The cross-sectional shape is shaped by refraction at the laser light incident surface (first surface) of A, and the optical axis direction is changed. When a normal prism is used, the refraction angle is smaller than the incident angle, so the optical axis direction is changed (rotated) in the counterclockwise direction in the figure.

The laser beam emitted from the beam shaping section 10A is incident on the reflection surface (second surface) of the total reflection section 10B at an angle equal to or greater than the critical angle of the reflection surface. The laser light is totally reflected by the reflecting surface, and its optical axis direction is changed to the same direction as the optical axis direction changing direction on the incident surface of the beam shaping unit 10A, and further changed to the optical axis direction and the beam shaping unit 10A. The angle θ formed by the incident optical axis is 9
Changed to be less than 0 degrees. This reflected light is incident on the split surface 11A of the beam splitter 11. That is, the optical axis direction of the laser light emitted from the semiconductor laser 7 is the laser light emitted from the fixing unit 6-1 of the optical pickup 6 fixed to the base 4 by the composite prism 10. Changed to 12 optical axis directions,
The same operation as in the case of the above-mentioned conventional example is performed.

Note that, as shown in FIG. 7B, the above-mentioned angle θ is, for example, 68 degrees. In addition, both photodiodes
21A and 21B are arranged on the opposite side surfaces in the fixing unit 6-1 depending on the arrangement direction of the total reflection prism 18.

In the disk device 1 according to the embodiment of the present invention having the above-described structure, the semiconductor laser 7 and the high frequency superposing circuit 8 are arranged in the fixed unit 6-1 of the optical pickup 6 so that the photodiodes 21A and 21B are connected to each other. And the transfer direction
Since it is almost within the span in the direction of 5 A and the width direction W, this fixed unit 6-1 is made compact, and the protruding length L ₁ of the fixed unit 6-1 is the same as that of the above-mentioned conventional example. The disk device 1 can be downsized because it can be configured to be smaller than the protruding length L ₃ .
Further, the space in the width direction of the disk device, which is restricted by the larger diameter of the disk 2 or the width W ₂ of the cartridge 3, can be effectively used, and the dead space can be reduced.

(Effects of the Invention) The optical disk device of the present invention having the above-described configuration can be downsized because the fixed unit of the laser recording / reproducing device is made compact, and is particularly suitable for portable use.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a magneto-optical disk device which is an embodiment of the optical disk device of the present invention, and FIG. 2 is a block diagram showing an example of a conventional magneto-optical disk device. 1 ... Magneto-optical disk device (optical disk device), 2 ...
Magneto-optical disk (optical disk), 6 ... Optical pickup (laser recording / reproducing device), 6-1.
6-2 ... Movable unit, 7 ... Semiconductor laser, 9 ...
... Collimating lens, 10 ... Compound prism, 10A ... Beam shaping section (beam shaping prism), 10B ... Total reflection section (optical axis direction changing means), 11 ... Beam splitter, 13 ...
… Beam raising prism, 14… Objective lens.

Claims (1)

[Claims] At least a semiconductor laser that emits a laser beam, a collimator lens that collimates the emitted light from the semiconductor laser, and a beam that sends reflected light including an information signal from a movable unit to a signal detection system. A fixed unit including a splitter, at least an objective lens that focuses the laser light on the recording surface of the optical disc to obtain the reflected light, and a beam rising prism that guides the light flux from the fixed unit to the objective lens. An optical disc device for recording / reproducing information on / from the optical disc by a laser recording / reproducing device comprising the movable part unit including the semiconductor laser and the collimator lens from the fixed part unit to the movable part unit. Arranged on a line that forms an angle of less than 90 degrees with the optical axis of the laser beam, and It has a first surface and a second surface between it and the beam splitter, and the emitted light refracted and incident from the first surface is incident on the second surface at an angle equal to or greater than a critical angle. , The laser beam is totally reflected in the same direction as the refraction direction, and the angle formed between the optical axis incident on the first surface and the optical axis totally reflected on the second surface is less than 90 degrees. An optical disc device comprising a prism for changing the optical axis direction of the optical disc device.