JPH05197996A - Optical recording and reproducing device for optical disk device - Google Patents

Abstract

PURPOSE:To enable the reduction in the thickness of an optical device in the case of incorporation into the optical disk device. CONSTITUTION:A beam splitter 4 is so constituted that the length of the side of its incident surface parallel with the rear surface of an optical disk 22 is >=2 times the length of the side perpendicular thereto. A laser beam having an elliptical section is made incident on the beam splitter 4 in such a manner that the major axis of the beam parallels with the long side of the incident surface. The laser beam passes a rising prism 5 of the same height size as the height of the beam splitter 4 and an objective lens 6. The recording surface of the optical disk 22 is irradiated with the laser beam as a light spot 7 of the elliptical shape, the minor diameter side of which is parallel with the recording tracks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing device incorporated in an optical disk device.

[0002]

2. Description of the Related Art In recent years, optical disk devices have been widely used. An optical recording / reproducing device including a laser oscillator, a photodiode, an objective lens, and the like is incorporated in this optical disc device. FIG. 2 is an explanatory diagram of a recording / reproducing operation principle of an optical disc device in which the optical recording / reproducing device of FIGS. 1 and 4 described later is incorporated.

As shown in the figure, a conventional optical disc device 31 comprises an optical recording / reproducing device 11, an optical disc 22, a spindle motor 23 and the like. The optical disk 22 is rotationally driven at a predetermined speed by a spindle motor 23 fixed to a base (not shown).
Information is recorded / reproduced on / from the disc 22 by a laser beam from the optical recording / reproducing device 11 arranged below the disc 22.

The optical recording / reproducing apparatus 11 is composed of a laser oscillator 2, a collimator lens 3, a beam splitter 14, a rising prism 15, an objective lens 6, a condenser lens 8, a photodiode 9 and the like. The laser light emitted from the laser oscillator 2 is collimated by the collimator lens 3 and then shaped into a circular beam cross-section by a beam shaper (not shown). It is incident on 15. The laser light reflected upward at a right angle by the rising prism 15 is irradiated onto the recording track on the recording surface of the optical disc 22 as a light spot 17 having a minute diameter by the objective lens 6. This light spot 17
An output control device (not shown) of the laser oscillator 2 controls the device so that the device 31 has a light intensity suitable for recording when operating in the recording mode, and has a light intensity suitable for reproducing when operating in the reproducing mode. Controlled.

In the case of this recording mode, the laser beam from the laser oscillator 2 is interrupted on the basis of the digital signal corresponding to the recording data, whereby the recording of this digital signal is performed. In the reproduction mode, the laser light reflected on the recording surface of the optical disc 22 is reflected by the beam splitter 14 via the objective lens 6 and the rising prism 15, and is condensed by the condenser lens 8. Then, it is converted into an electric signal by the photodiode 9 and output as a detection signal. The relationship between the objective lens 6 and the laser light will be described in more detail with reference to FIG. FIG. 3 is an explanatory diagram for explaining the relationship between the objective lens and the laser light in the optical recording / reproducing apparatus of FIGS. 1 and 4 described later.

As shown in the figure, when the effective diameter of the objective lens 6 is D ₀ and the luminous flux incident on the objective lens 6 from the raising prism 15 is d on the principal surface of the objective lens 6, The larger d / D ₀ , the more objective lens 6
The spot diameter φ of the light spot 17 at the focal point can be reduced. Therefore, as the incident light beam diameter d is increased with respect to the effective diameter D ₀ , the spot diameter φ is increased.
Can be reduced, and the spatial frequency characteristic of the optical disk device can be improved. However, when the incident light beam diameter d is increased, the utilization efficiency of the laser light is deteriorated, and each optical element between the laser oscillator 2 and the objective lens 6 is increased in size, and the entire optical recording / reproducing apparatus is increased in size. Since there are some points, the balance design is usually performed in consideration of the above points. Incidentally, the ISO format of a 3.5-inch optical disc specifies d / D ₀ ≧ 1.

The above-mentioned optical recording / reproducing apparatus 11 in FIG. 2 is for explaining the operation principle, but the actual configuration is as shown in FIG. FIG. 4 is a perspective view showing an example of a conventional optical recording / reproducing apparatus for an optical disk device. As shown in the figure, a conventional optical recording / reproducing apparatus 11
Is composed of the laser oscillator 2, the collimator lens 3, the beam shaper 20, the beam splitter 14, the rising prism 15, the objective lens 6, and the like.

The laser beam emitted from the laser oscillator 2 has an elliptical cross section whose long diameter side is oriented in a direction perpendicular to the lower surface of an optical disk (not shown), and has a numerical aperture NA _C.
Is 0.3 and the focal length f _C is 6 mm, the major axis as the half-value diameter on the entrance surface of the collimator lens 3 is 5.4 mm and the minor axis is 1.8 mm. The laser beam having the elliptical cross section is shaped into a circle by enlarging the minor axis side by the beam shaper 20, and the luminous flux diameter (corresponding to the above-mentioned luminous flux diameter d) on the incident surface of the beam splitter 14 is effective. Has a half-value diameter of 5.4 mm, but the effective diameter of the collimating lens 3 causes the end portion to be 3.6 mm. The side length of the incident surface of the beam splitter 14 is 5 mm square.

The laser light having the circular cross section is incident on the objective lens 6 through the rising prism 15 having the same height as the beam splitter 14. The objective lens 6 has an effective diameter D ₀ of 3.3 mm and a numerical aperture NA ₀ of 0.
55, the focal length f ₀ is 3 mm, and the spot diameter φ of the circular light spot 17 is 0.81 μm in half value diameter.
The height dimension b from the upper surface of the objective lens 6 to the lower surface of the rising prism 15 is 10 mm. In addition, in FIG. 4 described above, regarding the detection optical system described in FIG.
Omitted.

[0010]

A conventional optical recording / reproducing apparatus 11 for an optical disk apparatus having the above-mentioned structure.
Is the rising prism 15 from the upper surface of the objective lens 6 described above.
Since the height dimension b to the lower surface of the optical disc device is large, there is a problem that when the device 11 is incorporated into the optical disc device 31, it is difficult to reduce the thickness of the optical disc device 31. The present invention has been made in view of the above points, and an object thereof is to provide a compact and thin optical recording / reproducing apparatus for an optical disk device, which can be thinned when incorporated in the optical disk device. To do.

[0011]

An optical recording / reproducing apparatus for an optical disk device according to the present invention includes at least a laser oscillator which emits a laser beam having an elliptical cross section whose optical axis is parallel to the lower surface of the optical disk, and a laser from the laser oscillator. A rising prism that converts the optical axis of the light to a right angle upward, an objective lens that irradiates the laser light from the rising prism as a light spot perpendicularly to the recording surface of the optical disc, the laser oscillator and the rising prism. In an optical recording / reproducing apparatus for an optical disc device, which is inserted between the optical disc and the beam splitter for sending the reflected light from the optical disc to a detection optical system, the beam splitter has a side length perpendicular to the lower face of the optical disc. And the height of the rising prism is the same as this beam splitter. By the laser beam cross-section whose major axis is arranged to be incident on the beam splitter in parallel with the long sides of the entrance surface, it is to achieve the foregoing objects.

[0012]

EXAMPLES Examples of the present invention will be compared and explained under the same conditions as those of the above-mentioned conventional example. As shown in FIG. 2 described above, the optical disk device 21 in which the optical recording / reproducing apparatus 1 for an optical disk device according to an embodiment of the present invention is incorporated has a beam splitter 4, which is larger than the optical disk device 31 of the conventional example described above. Optical recording / reproducing apparatus 1 including rising prism 5 and the like
(7 is a light spot by the laser beam from the device 1) is different, and the description of the same parts as those in the above-mentioned conventional example will be omitted.

The optical recording / reproducing apparatus 1 in FIG. 2 is for explaining the operation principle, but the actual configuration is as shown in FIG. FIG. 1 is a perspective view showing an embodiment of an optical recording / reproducing apparatus for an optical disk device of the present invention.
As shown in the figure, an optical recording / reproducing apparatus 1 according to an embodiment of the present invention includes the laser oscillator 2, the collimating lens 3,
The beam splitter 4, the rising prism 5, the objective lens 6 and the like are provided, and the mounting angle of the laser oscillator 2 and the beam shaper 20 are different from those of the optical recording / reproducing apparatus 11 of the conventional example described above. Delete, beam splitter 4
Since only the shape of the rising prism 5 is different from that of the rising prism 5, the description of the same parts as those in the above-described conventional example will be omitted.

The laser beam emitted from the laser oscillator 2 has an elliptical cross section whose major axis side is oriented parallel to the lower surface of the optical disk (not shown), and the major axis as the half value diameter on the entrance surface of the collimator lens 3 is. 5.4m
m, the minor axis is 1.8 mm. Due to the effective diameter of the collimator lens 3, the end on the major axis side is eclipsed and the major axis is 3.6 m.
A laser beam with a substantially elliptical cross section of m and a minor axis of 1.8 mm is
It is incident on the beam splitter 4. The incident surface of the beam splitter 4 has a side length of 5 mm parallel to the lower surface of the optical disk (not shown) and a vertical side length of 2 mm. The laser beam having an elliptical cross section has its major axis parallel to the long side of the incident surface. As described above, the light is incident on the central portion of the incident surface of the beam splitter 4.

The laser light having the elliptical cross section is incident on the objective lens 6 through the rising prism 5 having the same height as the beam splitter 4. This objective lens 6
The laser beam emitted from the laser beam is emitted as an elliptical light spot 7 whose minor axis side is parallel to the recording track and whose minor axis size φ is 0.81 μm on the recording surface of an optical disk (not shown). The height a from the upper surface of the objective lens 6 to the lower surface of the rising prism 5 is 7 mm.

As described above, the optical recording / reproducing apparatus 1 for an optical disk apparatus according to the embodiment of the present invention having the above-described configuration is started up from the upper surface of the objective lens 6 as described above, as compared with the case of the conventional example. Since the height a to the lower surface of the prism 5 is shortened, when the device 1 is incorporated into the optical disc device 21, the spatial frequency characteristic equivalent to that of the conventional example is ensured and the optical disc device 21 is thin. It becomes possible. Further, since the beam shaper 20 is deleted, the cost can be reduced.

[0017]

The optical recording / reproducing apparatus for an optical disk apparatus according to the present invention can be thinned and the cost can be reduced. Therefore, the optical disk apparatus incorporating this apparatus can be thinned and the cost can be reduced. Improves performance.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an optical recording / reproducing apparatus for an optical disk device of the present invention.

FIG. 2 is an explanatory diagram of a recording / reproducing operation principle of an optical disc device in which the optical recording / reproducing device of FIGS. 1 and 4 is incorporated.

FIG. 3 is an explanatory diagram illustrating a relationship between an objective lens and laser light in the optical recording / reproducing device of FIGS. 1 and 4.

FIG. 4 is a perspective view showing an example of a conventional optical recording / reproducing device for an optical disc device.

[Explanation of Codes] 1 optical recording / reproducing device 2 laser oscillator 4 beam splitter 5 rising prism 6 objective lens 7 light spot 21 optical disc device 22 optical disc

Claims (1)

[Claims] 1. A laser oscillator which emits a laser beam having an elliptical cross section whose optical axis is parallel to the lower surface of the optical disc, and a rising prism which converts the optical axis of the laser beam from the laser oscillator to a right angle upward, Inserted between the laser oscillator and the rising prism, the objective lens that irradiates the laser light from the rising prism perpendicularly to the recording surface of the optical disk as a light spot, and the reflected light from the optical disk to the detection optical system. In an optical recording / reproducing apparatus for an optical disk device, which is provided with a beam splitter for sending in, the beam splitter has a side length of its incident surface parallel to the lower surface of the optical disk at least twice the vertical side length, and the rising prism is The height of the beam splitter is the same as that of the beam splitter, and the major axis of the laser beam with the elliptical cross section is parallel to the long side of this incident surface. An optical recording / reproducing device for an optical disk device, which is characterized in that the beam is incident on the beam splitter.