JP2790264B2 - Optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording apparatus for recording or reproducing information by light.

[0002]

2. Description of the Related Art In recent years, magneto-optical disk devices have been replaced by hard disk devices and floppy disk devices.
It is expected as a large-capacity information storage device. Reducing the size and weight of the optical pickup of the magneto-optical disk device not only reduces the size of the entire device, but also shortens the access time and improves the performance.

A conventional optical pickup for a magneto-optical disk will be described. FIG. 7 is an explanatory diagram of a conventional optical pickup. Reference numeral 25 denotes a semiconductor laser as a light source. 26 is a collimator lens, 27 is a prism anamorphic, which converts an elliptical light beam from a semiconductor laser into a parallel circular light beam. 28 is a PBS prism, which separates the probe light and the signal light. 29
A flip-up mirror, and an objective lens 30 focuses the light beam on the disk. 31 is a disk. Numeral 32 denotes a half-wave plate for rotating the signal light deflection direction by 90 degrees. 33 is a lens. 34
Is a hologram element, and 35 is an analyzer. 36 is a 6-split photodetector and 37 is a 2-split photodetector, which converts signal light into an electric signal.

The operation of the optical pickup configured as described above will be described. The light beam from the semiconductor laser 25 is collimated by a collimator lens 26 and prism anamorphic.
27, the light is converted into a parallel circular light beam.
The light is focused on the disk 31 by the objective lens 30 via the flip-up mirror 29. The collected light flux picks up a recording signal and is reflected as signal light. At this time, since the recording signal is recorded due to the difference in the magnetization direction, the rotation direction of the deflecting surface of the signal light varies depending on the signal due to the Kerr effect.

The signal light is supplied to the objective lens 30 and the flip-up mirror 29.
After being separated off the main optical axis by the PBS prism 28, the deflection direction of the signal light is rotated 90 degrees by the half-wave plate 32 so that the deflection of the signal light becomes a TM wave with respect to the hologram element. The light is incident on the hologram element 34 at a Bragg angle while being collected. The first-order diffracted light diffracted by the hologram element 34 is
An image is formed on the six-segment photodetector 36 and used as error detection signals for focus error and tracking error. The hologram element 34 is composed of four holograms. The measurement of the focus error signal is performed by using a double knife edge method in which a change in an imaging pattern due to defocusing at the focal position is detected by a four-division sensor. Is measured using a push-pull method in which a change in light intensity incident on two holograms is detected by a two-divided sensor. Further, the zero-order diffracted light passes through an analyzer 35 and is incident on a two-divided photodetector 37 to be used for signal reading.

[0006]

However, in the above-mentioned conventional configuration, since the bulk components are combined, there is a limit in miniaturization and weight reduction of the pickup, and it is difficult to adjust the position of each component. Had a point. An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an optical pickup which is small in size and light in weight and in which optical components are integrally formed.

[0007]

To achieve the above object, according to the Invention The first invention of the present invention, a laser generator for emitting a laser beam, the incident incident light beam that has been guided from the laser generator A first reflecting surface that reflects in the same optical axis direction as the light beam; and a first reflecting surface that is provided to face the first reflecting surface, and reflects the light beam from the first reflecting surface in the same optical axis direction as the light beam.
A second reflecting surface for morphism, the light beam from said second reflecting surface and a converging optical element for condensing on the disk, the first
The area surrounded by the outer periphery of the one reflecting surface is the condensing optics.
An optical pickup included in a region surrounded by the outer peripheral portion of the element was used.

According to a second aspect of the present invention, a first reflecting surface and a condensing optical element are provided.
Is an optical pickup formed on the same surface.
In the third invention, the first reflecting surface is formed on a LiNbO ₃ substrate by a professional method.
Optical grating which is a grating manufactured by the ton exchange method
Backup. In a fourth aspect, the first reflecting surface is a condensed light.
Optical pickup formed almost in the center of the element
Was. According to a fifth aspect of the present invention, the light collecting optical element is a grating lens.
Optical pickup. The sixth invention is a laser generation
Apparatus, first reflective surface, second reflective surface and light collection optics
Is an integrated optical pickup.

[0009]

By integrally forming the optical components of the optical pickup, the light beam emitted from the semiconductor laser can reciprocate once inside the optical system.

[0010]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of an optical pickup as one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a semiconductor laser as a light source, and 2 denotes a glass element. Reference numeral 3 denotes a first reflecting surface, which is a grating manufactured on a LiNbO ₃ substrate by a proton exchange method. Reference numeral 4 denotes a grating lens for condensing a laser beam on a disk, and is formed on the same plane as the first reflection surface 3.
Reference numeral 5 denotes a second reflecting surface made of a reflecting mirror film, which has two openings for passing a light beam from the semiconductor laser 1 and light incident on the photodetector. Reference numeral 6 denotes a multi-segment photodetector.

In the optical pickup according to the present embodiment, the semiconductor laser 1 and the multi-segmented photodetector 6 are adhered and fixed by the glass element 2 and the resin 7, and the above-mentioned components are integrally formed. . Next, the grating 3 manufactured by the proton exchange method using FIG.
Will be described. The grating 3 has a structure in which a lattice 10 in which proton exchange is periodically performed on a LiNbO ₃ substrate 9 and a dielectric film 11 on the lattice 10, and has a deflection separation function. In this structure, when the thickness of the dielectric film 11 is adjusted so that a phase difference does not occur between the proton exchange region and the outside of the proton exchange region with respect to the polarized light (ordinary light) orthogonal to the crystal optical axis direction, the ordinary light 12 becomes 0 Reflected as the next diffracted light 13 and deflected light (extraordinary light) 14 in the direction of the crystal optical axis of the incident light
Are diffracted and reflected as first-order diffracted light 15.

In FIG. 3, a grating manufactured by the proton exchange method of the present embodiment has a proton exchange region 16 whose crystal optical axis direction is orthogonal to the deflection plane of the emitted light beam from the semiconductor laser, and a grating of the emitted light beam. 45 to deflection plane
A central portion 18 having at least two regions 17 inclined at an angle and having a diameter equal to 1/3 of the grating diameter is shielded so as not to reflect a light beam.

The operation of the optical pickup configured as described above will be described with reference to FIG. A light beam from the semiconductor laser 1 is first diffracted and reflected by a grating 3 manufactured by a proton exchange method. The zero-order diffracted light in the proton exchange region in which the crystal optical axis direction is orthogonal to the deflection surface of the emitted light beam from the semiconductor laser 1 is used for reproducing information of the light beam. Is the same as the direction of the light beam emitted from the semiconductor laser, and may be considered to be due to specular reflection.
The light beam diffracted and reflected here is reflected again by the second reflection surface 5, enters the grating lens 4, and is condensed on the disk 8 by the condensing action of the grating lens 4.
At this time, the direction of deflection of the light beam focused on the disk 8 is equal to the direction of deflection of the light beam emitted from the semiconductor laser 1. Further, since the central portion of the light beam incident on the grating lens 4 is shielded, the light spot condensed by the super-resolution phenomenon becomes smaller.

Next, the light beam condensed on the disk is picked up by a recording signal and reflected. The reflected light becomes a signal light 20 rotated from the deflection direction 19 of the incident light due to the Kerr effect as shown in FIG. 4, but the recording signal is recorded due to the difference in the magnetization direction. The rotation direction is reversed based on the deflection direction. After passing through the grating lens 4 and the second reflecting surface 5, the signal light enters the grating 3 manufactured by the proton exchange method,
Diffracted and reflected. Of the diffracted light, first-order diffracted light that is diffracted and reflected in a proton region in which the crystal optical axis of the grating 3 is inclined by 45 degrees with respect to the deflection surface of the light beam emitted from the semiconductor laser 1 is coupled to the multi-segmented photodetector 6. The image is read and used as an error detection signal for each of the Kerr signal reading, the focus error, and the tracking error. Since the first-order diffracted light 21 has an analyzer function in a direction in which the crystal optic axis of the grating 3 is inclined at 45 degrees with respect to the deflection of the emitted light beam from the semiconductor laser 1, it becomes a component light of the signal light 20 in the analyzer direction. . As described above, the Kerr signal is detected by changing the intensity of the first-order diffracted light in the deflection direction of the Kerr signal.

Next, FIG. 5 is an enlarged view of the multi-segmented photodetector, and the respective error detection methods of the focus error and the tracking error will be described. The multi-segment photodetector 6 is formed of four sensors. These four sensors are referred to as S1, S2, S3, and S4 for convenience, and the outputs thereof are V
1, V2, V3, and V4. The first-order diffracted light that is diffracted and reflected in two proton regions in which the crystal optical axis of the grating 3 is inclined by 45 degrees forms an image on the boundary between S1 and S3 and between S2 and S4, respectively. From this, the focus error signal is measured by using the knife edge method for detecting a change in the imaging pattern due to the defocus at the focal position of the first-order diffracted light. That is, the differential signal of the sum of S1 and S4 and the sum of S2 and S3, (V1 + V4)-(V2 + V3) is detected. For the tracking error signal,
The change in the light intensity incident on the two proton exchange regions is measured using a push-pull method that detects the change as the intensity of the first-order diffracted light. That is, the differential signal of the sum of S1 and S3 and the sum of S2 and S4, (V1 + V3)-(V2 + V4) is detected.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. The configuration of the optical pickup of this embodiment is the same as that of the embodiment shown in FIG. A grating manufactured by the proton exchange method in the second embodiment will be described with reference to FIG. This grating is a combination of at least two proton exchange regions 22 whose crystal optic axis directions are orthogonal to the deflection surface of the emitted light beam from the semiconductor laser, and a region 23 inclined at 45 degrees to the deflection surface of the emitted light beam. Consists of
Further, the central portion 24 of the grating is shielded so that the light beam is not reflected. At this time, the measurement of the focus error and the tracking error is performed in the same manner as described above, using the first-order diffracted light from the region where the crystal optic axis is orthogonal to the deflection of the emitted light beam from the semiconductor laser. The Kerr signal is detected from a region where the crystal optic axis of the grating is inclined by 45 degrees with respect to the deflection of the light beam emitted from the semiconductor laser.
This is performed in the same manner as described above by using next-order diffracted light.

[0017]

As described above, the present invention has two reflecting surfaces, the first reflecting surface of which is a grating manufactured on a LiNbO ₃ substrate by a proton exchange method, and the condensing optical element is a grating lens. By forming the laser beam on the same surface, the laser beam reciprocates once in the optical system, and all the components are integrated, so that a small, light, and compact optical pickup can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical pickup as one embodiment of the present invention.

FIG. 2 is a configuration diagram of a grating by a proton exchange method in one embodiment of the present invention.

FIG. 3 is a plan view of a grating by a proton exchange method in the first embodiment of the present invention.

FIG. 4 illustrates a signal detection method.

FIG. 5 is an enlarged view of a photodetector in one embodiment of the present invention.

FIG. 6 is a plan view of a grating formed by a proton exchange method according to a second embodiment of the present invention.

FIG. 7 is an explanatory view of a conventional optical pickup.

[Description of Signs] 1 semiconductor laser 2 glass element 3 grating 4 grating lens 5 reflection mirror film 6 multi-segment photodetector 7 resin

Claims (6)

(57) [Claims] A laser generator for emitting a laser beam;
The entering an incident light beam that has been guided from the laser generator
A first reflecting surface that reflects in the same optical axis direction as the emitted light beam, and is provided opposite to the first reflecting surface, and reflects a light beam from the first reflecting surface in the same optical axis direction as the light beam. A second reflecting surface, and a condensing optical element for condensing a light beam from the second reflecting surface on a disc , outside the first reflecting surface.
The area surrounded by the peripheral part is the outer peripheral part of the condensing optical element.
An optical pickup characterized by being included in a more enclosed area . 2. The optical pickup according to claim 1, wherein the first reflection surface and the condensing optical element are formed on the same surface. 3. The optical pickup according to claim 1, wherein the first reflection surface is a grating manufactured on a LiNbO ₃ substrate by a proton exchange method. 4. The optical pickup according to claim 1, wherein the first reflection surface is formed substantially at the center of the condensing optical element. 5. The optical pickup according to claim 1, wherein the light collecting optical element is a grating lens. 6. The optical pickup according to claim 1, wherein the laser generator, the first reflecting surface, the second reflecting surface, and the condensing optical element are integrally formed.