JPH11250491A - Optical pickup and optical disk device - Google Patents

Abstract

(57) [PROBLEMS] To provide an optical pickup and an optical disk device in which an apparent optical path length is shortened and an actual optical path length is lengthened to reduce a projection area of a light beam on an optical disk. . SOLUTION: An optical element 23 disposed in an optical path from the light source 22c of the optical pickup to the light focusing means 21.
And the optical element comprises two sets of parallel planes 23
a, 23b, 23c, and 23d, and a light beam incident from a plane 23a on one side of one set disposed in parallel with the optical disc is parallel plane of the other set disposed obliquely with respect to the optical disc. The optical pickup 13 is configured so that after being internally reflected at least twice by 23c and 23d, the light is emitted from the other flat surface 23b of one set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical pickup and an optical disk apparatus for irradiating a surface of a rotating optical disk with light and detecting the return light.

[0002]

2. Description of the Related Art Conventionally, an optical pickup for reproducing an optical disk, for example, a compact disk (CD), is configured as shown in FIG. In FIG.
The optical pickup 1 includes an objective lens 2 and a light emitting / receiving element 3
It is composed of

The objective lens 2 is a convex lens,
The light beam from the light receiving / emitting element 3 is focused on a desired track on the signal recording surface of the optical disc D that is driven to rotate.
Further, the objective lens 2 is supported by a biaxial actuator (not shown) so as to be movable in biaxial directions, that is, in a focus direction and a tracking direction.

The light-receiving / emitting element 3 has a known structure, and is formed by encapsulating a light-emitting element and a light-receiving element in a semiconductor package as an integrated optical block, for example, as shown in FIG. ing. In FIG. 5, the light emitting / receiving element 3 has a second semiconductor substrate 3b mounted on a first semiconductor substrate 3a, and a laser diode chip 3c mounted on the second semiconductor substrate 3b.

On the first semiconductor substrate 3a in front of the laser diode chip 3c, the laser diode chip 3c
A trapezoidal prism 3d having an inclined surface (light path splitting surface) on its side is disposed, and a semi-transmissive film (not shown) as a beam splitter is formed on the light path splitting surface 3e. The prism 3d has a total reflection film (not shown) formed on its upper surface, and a semi-transmissive film (not shown) formed on its lower surface. The prism 3d reflects the light beam emitted from the laser diode chip 3c upward by the optical path branch surface, and emits the light beam to the outside. The light beam emitted from the light receiving / emitting element 3 is
As shown in FIG. 4, the light enters the objective lens 2 and is focused and focused on the signal recording surface of the optical disc D by the objective lens 2.
The return light beam reflected by the optical disk D enters the prism 3d of the light receiving / emitting element 3 via the objective lens 2, and is sequentially reflected by the bottom surface and the top surface of the prism 3d, thereby forming the bottom surface of the prism 3d. At two places, the light is emitted below the prism 3d. The light detector 3 is located on the upper surface of the first semiconductor substrate 3a at a position for receiving light emitted from two places on the bottom surface of the prism 3d.
f, 3 g are formed.

[0006]

In the optical pickup 1 having such a structure, when the distance from the laser diode chip 3c, which is a light source, to the optical disk D is shortened, problems such as laser noise occur, and the This distance cannot be shortened beyond a certain degree, since the reproduction quality is impaired. For this reason, there has been a problem that the projected area on the signal recording surface of the optical disc D, that is, the spot size becomes large. On the other hand, there is an optical element that makes multiple reflections in a parallel plane in order to increase the optical path length from the light source to the optical disk. However, due to this multiple reflection, the light beam amount from the light source is greatly reduced. However, there is a problem that it is not practical.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an optical pickup and an optical disk apparatus in which the apparent optical path length is shortened and the actual optical path length is increased to reduce the projected area of a light beam on an optical disk. It is intended to provide.

[0008]

According to the present invention, there is provided a light source for emitting a light beam, light focusing means for focusing the light beam emitted from the light source on a signal recording surface of an optical disk, An optical detector including a photodetector to which a return light beam from a signal recording surface of an optical disc is incident via the light focusing means, wherein the optical pickup is disposed in an optical path from the light source to the light focusing means. The optical element has two sets of parallel planes, and a light beam incident from one side of one of the sets arranged substantially parallel to the optical disc is inclined with respect to the optical disc. This is achieved by an optical pickup configured to be internally reflected at least twice in the other set of parallel planes and then to exit from the other side of the set.

According to the above configuration, when reproducing an optical disk, the light beam emitted from the light source is focused on the signal recording surface of the optical disk via the optical element and the light focusing means, and the return light beam from the optical disk is Again enter the photodetector via the light focusing means. Thus, the reproduction signal of the optical disk, the tracking error signal, and the focus error signal are detected based on the detection signal from the photodetector.

In this case, the light beam from the light source is incident on the light focusing means by being internally reflected at least twice through the optical element, so that the apparent optical path length, that is, from the light source to the optical disk, Is relatively short, and the actual optical path length, i.e., the optical path that is internally reflected at least twice within the optical element, is relatively long. Accordingly, the entire optical pickup is configured to be small, and the projected area of the light beam from the light source on the optical disk signal recording surface, that is, the spot diameter is reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows the configuration of an optical disk device incorporating an optical pickup according to the present invention. In FIG. 1, an optical disk device 10 includes a spindle motor 12 as a driving unit that rotationally drives an optical disk 11, and an optical pickup 13. Here, the spindle motor 12 is driven and controlled by the optical disk drive controller 14, and is rotated at a predetermined rotation speed. The optical disc 11 can select and reproduce a plurality of types of optical discs.

The optical pickup 13 irradiates the signal recording surface of the rotating optical disk 11 with light to record a signal or to detect return light from the signal recording surface. A reproduced signal based on the return light is output to the signal demodulator 15.

Thus, the recording signal demodulated by the signal demodulator 15 is subjected to error correction through an error correction circuit 16 and is transmitted to an external computer or the like via an interface 17. With this, the external computer etc.
A signal recorded on the optical disk 11 can be received as a reproduction signal.

The optical pickup 13 is connected to a head access controller 18 for moving the optical pickup 13 to a predetermined recording track on the optical disk 11 by a track jump or the like. Further, a servo circuit 19 for moving the objective lens in the focusing direction and the tracking direction is connected to the biaxial actuator holding the objective lens of the optical pickup 13 at the moved predetermined position.

FIG. 2 shows a first embodiment of the optical pickup according to the present invention. In FIG. 2, an optical pickup 13 includes an objective lens 21 as a light focusing unit.
And an optical element 23 disposed between the objective lens 21 and the light emitting / receiving element 22.

The objective lens 21 is a convex lens and forms an image of a light beam from the light emitting / receiving element 22 on a desired track on a signal recording surface of the optical disk D that is driven to rotate. Further, the objective lens 21 is supported by a biaxial actuator (not shown) so as to be movable in biaxial directions, that is, in a focus direction and a tracking direction.

The light receiving / emitting element 22 is a device in which a laser diode chip as a light source and a photodetector are enclosed in a semiconductor package as an integrated optical block, and is configured, for example, as shown in FIG. 3, the light emitting / receiving element 22 has a second semiconductor substrate 22b mounted on a first semiconductor substrate 22a, and a laser diode chip 22c mounted on the second semiconductor substrate 22b.

On the first semiconductor substrate 22a in front of the laser diode chip 22c, there is provided a trapezoidal prism 22d having an inclined surface (optical path branch surface) on the side of the laser diode chip 22c. Branch surface 22e
Has a semi-transmissive film (not shown) as a beam splitter
Are formed. The prism 22d has a total reflection film (not shown) formed on its upper surface, and a semi-transmissive film (not shown) formed on its lower surface. The prism 22d reflects the light beam emitted from the laser diode chip 22c upward by the optical path branch surface, and emits the light beam to the outside. The light beam emitted from the light emitting / receiving element 22 enters the objective lens 2 as shown in FIG. 2 and is focused and focused on the signal recording surface of the optical disc D by the objective lens 2.

The return light beam reflected by the optical disk D enters the prism 22d of the light receiving / emitting element 22 via the objective lens 2, and is sequentially reflected at the bottom and top surfaces of the prism 22d, thereby forming the prism 22d. At two places on the bottom surface of the prism, the light is emitted below the prism 22d. On the top surface of the first semiconductor substrate 22a, photodetectors 22f and 22g are formed at positions where light emitted from two places on the bottom surface of the prism 22d is received. As shown in FIG. 3, the photodetectors 22f and 22g are respectively connected to the light receiving portions a, b, and c and the light receiving portions d, e, and f by two divided lines extending in the vertical direction near the center thereof. Each of the light receiving portions a, b, and
Detection signals Sa, Sb, Sc, S from c, d, e, f
d, Se, Sf, the focus error signal FE
And a tracking error signal TE.

The optical element 23 is, as shown in FIG.
It is formed of a light-transmitting material such as a glass material such as glass or a synthetic resin so as to have at least two sets of parallel planes. In the figure, a first set of parallel planes 2 of the optical element 23 is shown.
The reference numerals 3a and 23b are disposed substantially parallel to the optical disk D. Also, the second set of parallel planes 23c, 23d
Is formed so that one side is longer than the first set of parallel planes. The second set of parallel planes 23c is configured such that the angle θ in FIG. 2 is, for example, 150 degrees with respect to the first set of parallel planes 23b. The set of parallel planes 23c and 23d is disposed obliquely with respect to the optical disc D. Here, the first pair of parallel planes 23a and 23b and the second parallel plane 23
The angle between c and 23d is desirably selected as small as possible so that, for example, a light beam incident from the plane 23a can be emitted from the opposite plane 23b without being internally reflected.

Thus, the light beam emitted from the laser diode chip 22c of the light emitting / receiving element 22 is perpendicular to the optical element 2 from the first set of parallel planes 23a of the optical element 23.
After being incident on the inside 3, the light is obliquely incident on the second set of parallel planes 23c from the inside and is reflected. Thereafter, the light beam is internally reflected again on the opposite parallel plane 23d of the second set, and once again on the parallel planes 23c and 23d, and then from the other parallel plane 23b of the first set. The light is emitted vertically and reaches the signal recording surface of the optical disc D via the objective lens 21. Similarly, the return light from the optical disc D is also internally reflected twice on the parallel planes 23c and 23d in the optical element 23, and then enters the light receiving sections 22f and 22g of the light receiving and emitting element 22. ing.

Optical pickup 13 according to the present embodiment
Is configured as described above. When the optical disk D is reproduced, the light beam from the laser diode chip 22c of the light receiving / emitting element 22 is reflected by the optical path branch surface 22e, and the optical element 23 and the objective Through the lens 21,
It is focused on the signal recording surface of the optical disc D. Optical disk D
Return light from the objective lens 21 and the optical element 23 again.
Through the light receiving / emitting element 22 and the light detector 22
f, 22 g. Thereby, the photodetectors 22f,
Based on the detection signal from 22g, a reproduction signal, a focus error signal, and a tracking error signal relating to the optical disk D are detected, and the recording signal of the optical disk D is correctly reproduced.

In this case, the apparent optical path length can be reduced by arranging two sets of parallel plane optical elements 23 in the optical path between the light receiving / emitting element 22 as a light source and the objective lens 21. First parallel planes 23a and 23 of the optical element 23
The distance b is relatively short, and the actual optical path length is relatively long in the optical element 23 due to repeated internal reflection between the second parallel planes 23c and 23d. Therefore, the optical pickup 13 and the optical disk device 10 are made compact as a whole, and the optical path length becomes longer due to repeated internal reflection in the optical element 23. , Ie, the spot diameter becomes smaller. This enables accurate reproduction of higher density recording tracks. At this time, since the distance from the laser diode chip 22c of the light receiving / emitting element 22 as a light source to the optical disk D is sufficiently long, a high reproduction quality of the optical disk D can be obtained without the problem of laser noise. Become.

In the above embodiment, the optical element 23
Is configured to be internally reflected four times between the second parallel planes 23c and 23d, but is not limited thereto, and may be internally reflected once at each of the planes 23c and 23d. It is apparent that the internal reflection may be performed three times or more on each of the planes 23c and 23d. Further, in the above embodiment, the optical pickup using the light receiving / emitting element 22 in which the light source and the photodetector are integrally formed by the prism 22d so that the optical axes coincide with each other has been described. For example, even in the case of a light receiving and emitting element integrally configured so that the optical axes are aligned by a hologram, the light source and the photodetector are separately formed, and the light detection is performed in the optical path of the return light branched by the light separating means. Obviously, the present invention can be applied to an optical pickup provided with a device.

[0026]

As described above, according to the present invention, the apparent light path length is shortened and the actual light path length is lengthened to reduce the projected area of the light beam on the optical disk. A pickup and an optical disk device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical disk device incorporating an optical pickup according to the present invention.

FIG. 2 is a schematic side view showing a configuration of an embodiment of an optical pickup in the optical disk device of FIG. 1;

FIG. 3 is a schematic perspective view showing a configuration of a light emitting / receiving element in the optical pickup of FIG. 2;

FIG. 4 is a schematic side view showing a configuration of an example of a conventional optical pickup.

FIG. 5 is a schematic perspective view showing a configuration of a light receiving and emitting element in the optical pickup of FIG.

[Explanation of symbols]

10 optical disk device, 11 optical disk, 1
2 ... Spindle motor, 13 ... Optical pickup, 14 ... Optical disk drive controller, 15
... Signal demodulator, 16 ... Error correction circuit, 17 ...
Interface, 18 Head access control unit, 19 Servo circuit, 21 Objective lens, 2
2 ... light receiving / emitting element, 23 ... optical element, 23a, 2
3b: first parallel plane, 23c, 23d: second parallel plane.

Claims (3)

[Claims] A light source for emitting a light beam; a light focusing means for focusing the light beam emitted from the light source on a signal recording surface of the optical disk; and a light focusing device for returning the light beam from the signal recording surface of the optical disk. An optical pickup comprising: a light detector that enters through the means; and an optical element disposed in an optical path from the light source to the light focusing means. A light beam incident from a plane on one side of one set having a parallel plane and disposed substantially parallel to the optical disc is at least twice transmitted by the other set of parallel planes disposed obliquely to the optical disc. An optical pickup characterized in that, after being internally reflected, the light is emitted from a plane on the other side of one set. 2. The optical pickup according to claim 1, wherein the light source and the photodetector are integrally formed as a light receiving / emitting element. 3. An optical pickup for irradiating the optical disc with light through a light converging means and detecting return light from a signal recording surface from the optical disc; A biaxial actuator supporting the means so as to be movable in two axial directions; a signal processing circuit for generating a reproduction signal based on a detection signal from the optical pickup; and a light focusing means based on the detection signal from the optical pickup. A servo circuit for moving in a biaxial direction, wherein the optical pickup includes a light source that emits a light beam, and a light focusing unit that focuses the light beam emitted from the light source on a signal recording surface of an optical disc. An optical detector including a light detector from which a return light beam from the signal recording surface of the optical disk is incident via the light focusing means. An optical element disposed in an optical path from the light source to the light focusing means, the optical element having two sets of parallel planes, and one set arranged substantially parallel to the optical disc. After the light beam incident from one side of the plane is internally reflected at least twice by the other set of parallel planes obliquely arranged with respect to the optical disk, the light beam is emitted from the other side of one set. An optical disk device characterized by being constituted.