JPH0246535A - Optical pickup device - Google Patents

Abstract

PURPOSE:To miniaturize an optical pickup by forming a diffraction element, a light waveguide path and a photodetector on the surface of an optical lens. CONSTITUTION:A light irradiating from a semiconductor laser 1, while a radiation angle is widened by a divergent leans 2, is collected to the surface of an optical disk 4 by a convergent lens 3. A laser beam reflected on the surface of the optical disk 4 is made divergent in a reverse direction, made incident on the convergent lens 3 and converted to the converging light. A part of the converging light is coupled through a light diffraction element 6 to a light waveguide path formed on the surface of the divergent lens 2 and divided into 4 directions in the light waveguide path 5 and propagated. The light to propagate the light waveguide path 5 arrives at a photodetector 7 and a signal stored in the optical disk 4, a focusing signal and a tracking signal are detected. Thus, the distance from the semiconductor laser 1 to the convergent lens 3 is <=5mm and the title device can be made miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information processing device for recording and reading out information stored in an optical storage medium such as an optical disk or a magneto-optical disk using a laser beam. This relates to optical pickups.

Conventional technology Conventionally, optical pickups that use laser light to record and read out information stored on optical storage media such as optical disks and magneto-optical disks use a semiconductor laser as a light source and a light source that uses the light emitted from the semiconductor laser. An optical lens to focus the laser beam onto the storage medium, a beam splitter to guide the laser beam reflected by the optical storage medium to a light receiving element, and a beam splitter to add astigmatism to the reflected light from the medium so that the laser beam is focused onto the optical storage medium. a cylindrical lens for detecting the defocus of the light and forming an image on the light receiving element; and a light receiving element for receiving the reflected light and detecting the defocus, the tracking deviation, and the information stored in the optical storage medium. It is composed of:

Normal optical pickups use a beam splitter to guide the laser light reflected by the optical storage medium to the light receiving element, and add astigmatism to the reflected light, causing the focus of the light converged on the optical storage medium to shift. Since a cylindrical lens or the like is required to enable detection of the image and form an image on the photodetector, the number of optical components increases, making it difficult to align the optical axis, making the manufacturing cost expensive, and making the optical pickup smaller. Therefore, in order to achieve miniaturization, an optical integrated pink amplifier was proposed, which uses an optical integrated circuit that combines the functions of the lens, beam splinter, and light receiving element. Ta. (References, back page, Journal of the Institute of Electronics and Communication Engineers Vol., Jes-C
, 8031985) The outline of this optical big amplifier is shown in FIG. The light emitted from the semiconductor laser 61 propagates through the optical waveguide 53 formed on the Si substrate 52, and
A condensing grating coupler 54 formed on the Δ-/' optical waveguide 53 condenses the light onto the surface of the optical disk 5.6.

Then, the light that is reflected and spread by the surface of the optical disk with an intensity corresponding to the recorded information reaches the condensing grating coupler 64 again and is converted into waveguide light, and a part of it is transmitted to the semiconductor laser 6.
1, a part of it is split into two other directions by a condensing beam splitter 56, and is imaged on two pairs of light receiving elements 67 formed on the Si substrate 52. Using the Foucault method, the focus is shifted and the I-ranking is determined. A signal of the deviation and information recorded on the optical recording medium is detected.

Furthermore, in order to achieve miniaturization, an optical pickup has been developed in which a hologram element that can simultaneously perform both the functions of a beam splitter and a cylindrical lens in a conventional optical pickup is used. (References, Mokuma et al., 22nd Micro-Optics Research Group Paper Vol. 14, 2
28.1986) A schematic diagram of this hologram type optical pickup is shown in FIG. The light emitted from the semiconductor laser 61 passes through the hologram lens 62 and enters the imaging lens 61\
-/63, the light is focused on the surface of the optical disk 64.

The light that is reflected and spread by the surface of the optical disk 64 with an intensity corresponding to the recorded information is converged again by the imaging lens 63, and part of it returns to the semiconductor laser 61, but part of it is transmitted to two regions (R1
, R2) is divided into two directions by the hologram element 62, and the image is focused on the four-divided light receiving element 66, and the focus shift, tracking shift, and the signal of the information stored in the optical storage medium are detected by the so-called Knifezi method. Detected.

Problems to be Solved by the Invention However, in the above-mentioned optical integrated pickup, strict precision is required for the focusing grating coupler 64 in order to focus the light sufficiently onto the optical disk, and also due to fluctuations in the wavelength of the semiconductor laser. However, it also had the disadvantage of deteriorating its light-condensing properties. Furthermore, in this optical integrated optical pink-up, a portion of the light emitted from the semiconductor laser 51 is diffracted by the beam splitter 56 before reaching the focusing grating coupler 54, resulting in poor light utilization efficiency. In addition, in the hologram type 7 I-no optical pick amplifier shown in Fig. 6, it is necessary to place a hologram element between the semiconductor laser and the converging (imaging) lens, and the light emitted from the laser is transferred onto the optical disk. In order to narrow down the diffraction limit to 1 μm or less, it is necessary to separate the converging lens and the semiconductor laser by about 1 a or more, increase the beam diameter once, and then narrow down the beam using a converging lens with a large NA. Therefore, there are limits to the miniaturization of optical pickups.

The present invention overcomes the problems of conventional optical pickups as described above and provides a compact optical pickup amplifier.

Means for Solving the Problems The present invention provides a laser light source for emitting light, an optical lens for diverging the light emitted from the laser, and an optical lens for converging the diverging light onto an optical storage medium. ,
The structure includes an optical waveguide formed with a diffraction element that combines light reflected by the optical storage medium, and a light receiving element for detecting the light propagating through the optical waveguide, and the diffraction element, the optical waveguide, and the light receiving element detect the light propagating through the optical waveguide. The present invention provides an optical pickup in which a light receiving element is formed on the surface of the diverging or converging optical lens.

The present invention also provides a laser light source that emits light, an optical lens for diverging the light emitted from the laser, an optical lens for converging the diverging light onto an optical storage medium, and the optical storage medium. an optical waveguide formed with a diffraction element for coupling light reflected by the optical waveguide; an element for emitting light propagating through the optical waveguide; and a light receiving element for detecting the emitted light; A diffraction element, an optical waveguide, and a coupling element for radiating the light propagating through the optical waveguide to the outside are formed on the surface of the diverging or converging lens, and a light receiving element is disposed near the laser light source. Pick-up is provided. The present invention also provides a semiconductor laser light source that emits light, a diverging lens that diverges the light emitted from the semiconductor laser, and an optical lens that converges the diverging light onto an optical storage medium,
The reflected light from the optical storage medium returns to the diverging lens and passes through the optical waveguide 9 formed on the surface of the diverging lens.
The reflected light is coupled to the optical waveguide via a diffraction grating, propagates through the optical waveguide, is radiated out of the optical waveguide by a diffraction grating formed separately from the diffraction grating, and is guided to a light receiving element; The semiconductor laser light source and the light receiving element are arranged on the same mount, and the semiconductor laser and the light receiving element are sealed by a diverging lens in which an optical waveguide and a diffraction grating are formed.

Function The present invention reduces the distance between the semiconductor laser and the converging lens by narrowing down the laser beam that reaches the converging lens onto the optical disk through an optical lens having a diverging effect, and also reduces the reflection that contains the signal. By guiding light to a light receiving element using an optical waveguide, the size of the optical pickup can be reduced.

Examples The details of the present invention will be explained using examples. An outline of an embodiment of the first invention is shown in FIG. The arrows indicate the propagation state of light. The radiation angle of the light emitted from the semiconductor laser 1 is widened by 10 cm by a diverging lens (concave lens) 2, and it is focused onto the surface of an optical disk 40 by a converging lens (convex lens) 3. be done. The laser beam reflected on the surface of the optical disk 4 is then diverged in the opposite direction, enters the converging lens 3, and is converted into condensing light.

A part of this condensing light passes through the diverging lens 2 and returns to the semiconductor laser 1, but a part of the light is sent to the grating coupler, that is, the optical waveguide 5 formed on the surface of the diverging lens 2.
Two optical diffraction elements e (ea, eb.

6C, 6d), and propagates in four directions in the optical waveguide 6. The light propagating through the optical waveguide 6 is transmitted through four light receiving elements 7 (7N, 7b, 7C) made of, for example, amorphous silicon.

7d), the signals stored on the optical storage medium (optical disk 4), focusing signals, and tracking signals are detected.

FIG. 2(a) is a diagram schematically showing the surface of the diverging lens shown in FIG. 1 in which four optical diffraction elements 6a to 6d are formed in the center, and FIG. 2(b) is a diagram showing the outline of the surface of the diverging lens shown in FIG. It is a 1' line sectional view. A dielectric loading layer having a bending and chirping structure is formed on the optical waveguide 6 to form a light 1 1 ''-7 diffraction element 6, that is, a grating coupler. It has a function of guiding the condensing light that is intended to be condensed toward the optical waveguide and condensing it onto the light receiving element in the optical waveguide as indicated by the arrow l.

Furthermore, among these grating couplers, that is, optical diffraction elements (ea, 6b, ec, sd), elements 6a and 6
In C, the optical disc is in just focus (the distance between the optical disc 4 and the converging lens 3 is maintained so that the emitted light from the semiconductor laser has the minimum spot diameter on the optical disc), and it is also slightly away from the converging lens. On the other hand, 6b and 6d are set so that the coupling efficiency is maximized when the optical disk approaches just focus. Therefore, if the outputs of the four light receiving elements 7iL, 7b, 0, 7d are A, B, C, D, a focus signal is obtained by (A+C) (B+D), and (A+B) - (C+D).
'), the tracking signal is obtained. Also A-1-B
-1-C-1-D is a recording signal O In this embodiment, an optical waveguide, a grating coupler, a light receiving element, etc. are formed on the upper surface of the concave lens 2.
It may be formed on the lower surface of the concave lens 2.

In addition, grating couplers are configured to converge convergent light onto a light receiving element on the optical waveguide, but the light receiving element is placed at the periphery, and the light is diverged from the center to the periphery within the waveguide. It is also possible to configure the grating coupler in a similar manner.

Moreover, the optical waveguide 5. The grating coupler 6 and the light receiving element 7 may be formed on either surface of the converging lens 3.

The pickup shown in FIG. 1 uses a diverging lens 2 and uses a configuration in which a grating coupler, an optical waveguide, and a light receiving element are formed on the surface of the lens, so the distance between the semiconductor laser 1 and the converging lens 3 can be as small as 6 or less times. Miniaturization can be achieved.

FIG. 3 (+L) shows a second embodiment of the present invention. Hikari Pi 1
3H.-/ The general configuration of the pickup and the principle of signal detection are the same as in the previous embodiment. However, the reflected light that reaches the element 6, which is the grating coupler, propagates through the optical waveguide 5' as diverging light toward the outside of the lens, and is connected to the space (in this case S emitted to the lower side) and placed around the periphery of the semiconductor laser.
The light is irradiated onto the light receiving element 8 of i, and a signal is detected.

The feature of this embodiment is that an ordinary Si semiconductor photodetecting element can be used as the light receiving element 8, so that
It is possible to read signals at a high speed of about t/s, and the reliability is also high.

In the present invention, a grating coupler is used to guide the light propagating through the optical waveguide 5' to the light receiving element 8. However, it is not necessary to use a grating coupler, and a prism coupler or a reflecting mirror may be used. The light emitted from the end face may be detected. Furthermore, in this embodiment, the optical waveguide is formed on the semiconductor laser side of the concave lens 2;
It may be formed on the optical disk side. Example 14'./ in this case is shown in FIG. 3(b).

FIG. 4 shows an example of a semiconductor laser device that can be used in the optical pickup according to the second embodiment of the present invention. (a) is a top view, and (b) is a cross-sectional view of the device seen from the side. In FIG. 4, the same functional parts as in FIG. 3 are given the same numbers, and the lens 3 and disk 4 are common and are omitted from the drawing.

1 is a semiconductor laser, 42 is a Si submount, 8 is a light receiving element, 2 is a concave lens, and an optical waveguide 5' and a grating coupler 6.9 are installed.

Further, 49 is a mount, 60 is a cap on which the concave lens 45 is installed, the inside is filled with an inert gas such as nitrogen, and 61 is an electrode terminal.

The light emitted from the semiconductor laser 1 is further emitted to the outside as diverging light by the concave lens 2.

On the other hand, convergent light including a signal from the outside, such as an optical disk, is coupled to the optical waveguide 5' by the grating coupler 9, and the light propagating through the optical waveguide 5' reaches the light receiving element 8 via the grating coupler 9. detected.

15 Vane In this embodiment, the light propagating through the optical waveguide reaches the light receiving element via the grating coupler, but the light receiving element may be formed on the optical waveguide.

The semiconductor laser device shown in FIG. 4 can realize a compact optical pink-up by applying it to the optical pink-up as described above, and the light-receiving element 8 and the semiconductor laser 1 are mounted on the same mount 4.
9, it is easy to align and assemble them. Cap 51. It is sealed with the concave lens 2 and has extremely high reliability.

Effects of the Invention As shown above, the present invention overcomes the problems of conventional optical pickups and provides a small and lightweight optical pink-up, which is of great value.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical pickup according to an embodiment of the present invention, and FIGS. 2(a) and (b) are plan views of a diverging lens equipped with an optical waveguide used in the same embodiment, along line m-n'. 3(a) and 3(b) are schematic diagrams of an optical pickup device according to another embodiment of the present invention, and FIGS. 4(a) and 4(b) are another example of a semiconductor laser device of the present invention. Schematic plan view of ■■′
The line cross-sectional views, FIGS. 5 and 6, are schematic diagrams of a conventional optically integrated pink-up and hologram type optical pickup. 1... Semiconductor laser, 2... Diverging lens, 3... Converging lens, 4... Optical disk, 5.5'... Mark optical waveguide, 6 ...Light diffraction element, 7... Light receiving element. Name of agent Patent attorney Shigetaka Awano Haga 1 person

Claims (3)

[Claims] (1) A laser light source that emits light, an optical lens for diverging the light emitted from the laser, an optical lens for converging the diverging light onto an optical storage medium, and a laser light source that emits light that is reflected by the optical storage medium. The structure includes an optical waveguide formed with a diffraction element for coupling light into the waveguide, and a light receiving element for detecting the light propagating through the optical waveguide, and the diffraction element, the optical waveguide, and the light receiving element are connected to each other. An optical pickup device characterized in that it is formed on the surface of the diverging or converging optical lens. (2) A laser light source that emits light, an optical lens for diverging the light emitted from the laser, an optical lens for converging the diverging light onto an optical storage medium, and reflecting by the optical storage medium. An optical waveguide formed with a diffraction element for coupling light; an element for emitting light propagating through the optical waveguide; and a light receiving element for detecting the emitted light; An optical waveguide and a coupling element for radiating the light propagating through the optical waveguide to the outside are formed on the surface of the diverging or converging lens,
An optical pickup device characterized in that a light receiving element is arranged near the laser light source. (3) a semiconductor laser light source that emits light, a diverging lens that diverges the light emitted from the semiconductor laser light source, and an optical lens that converges the diverging light onto an optical storage medium;
The reflected light from the optical storage medium returns to the diverging lens, the reflected light is coupled to an optical waveguide formed on the surface of the diverging lens via a diffraction grating, and propagates through the optical waveguide, and the diffraction grating The semiconductor laser light source and the light receiving element are disposed on the same mount, and the semiconductor laser light source and the light receiving element are arranged on the same mount, and the light is emitted out of the optical waveguide by a diffraction grating formed separately from the optical waveguide and guided to the light receiving element. An optical pickup device characterized in that the semiconductor laser light source and the light receiving element are sealed by a formed diverging lens.