JP2709090B2 - Waveguide type optical head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical head used for an optical pickup unit such as an optical disk or a magneto-optical disk, and more particularly, to a waveguide type optical head using an optical waveguide.

(Prior art) As an optical pickup unit such as a read-only optical disk such as a compact disk or a laser disk, a write-once optical disk, or a magneto-optical disk capable of recording and reproducing information utilizing a magneto-optical effect. Conventionally, as shown in FIG. 5, an optical head combined with a bulk type optical component has been used.

In the optical head shown in FIG. 5, a semiconductor laser (LD) or the like is used as a light source 12, and a laser beam emitted from the light source 12 is deflected toward a recording medium 11 such as an optical disc by a deflection beam splitter 14 or a half mirror. After that, the laser light is focused on the surface of the recording medium 11 by the objective lens 13, and the reflected light from the surface of the recording medium 11 is passed through the objective lens 13, the deflecting beam splitter 14, the condenser lens 15, etc. ) And the like, and condensed on the photodetector 16 to perform information reproduction, position shift detection in the track direction T, position shift detection in the focus direction F, and the like.

However, in an optical head as shown in FIG. 5,
As shown, a plurality of optical components (light source 12, lenses 13, 15,
Since the optical head is configured by combining the deflection beam splitter 14 and the photodetector 16), the entire optical head becomes large and heavy, and it is difficult to reduce the size of the apparatus. In addition, since optical components are combined, the configuration of the apparatus becomes complicated, and assembling and adjustment are troublesome. In addition, there is a problem that the production cost increases because the number of components is large.

In order to solve such a problem of the conventional optical head, a waveguide type optical head in which an optical waveguide is formed on a substrate and a lens element, a light emitting element, a light receiving element and the like are integrated on the substrate is proposed. (See, for example,
-217434).

In this waveguide type optical head, since an optical waveguide, a lens element, a light emitting element, a light receiving element, and the like are integrated on a substrate, each element can be accurately positioned at the time of manufacturing, and can be adjusted during assembly. Is unnecessary, and the detection accuracy is improved. Further, the number of parts is greatly reduced, so that the production cost can be significantly reduced.

(Problems to be Solved by the Invention) By the way, in the waveguide type optical head, the sixth type
As shown in the figure, an optical waveguide 19 is formed on a substrate 18, light is emitted from an end face 19a of the optical waveguide 19, the light is condensed on a recording medium 21 via an objective lens 20, and the recording is performed. The reflected light from the medium 21 is condensed again through the objective lens 20, and the reflected light is made to enter the optical waveguide 19 from the end face portion 19a of the optical waveguide 19, and is reflected by the light receiving element on the substrate 18 through the optical waveguide 19. It was configured to guide light.

However, in the waveguide type optical head 17 that emits and enters light from the end face portion 19a of the optical waveguide 19, if the incident position of the reflected light is shifted from the waveguide end face 19a due to the displacement of the recording medium 21 or the like, the optical waveguide There is a problem that the incidence efficiency of the reflected light to the light source 19 is significantly reduced, and the detection accuracy is significantly reduced.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a waveguide type optical head which can surely guide reflected light from a recording medium such as an optical disk to an optical waveguide and can perform stable signal detection.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an optical waveguide in which a lens element, a light emitting element, and a light receiving element are integrated on an optical waveguide layer laminated on one surface of a substrate. Wherein the optical waveguide constituting the optical waveguide has a uniform layer thickness waveguide layer having a uniform layer thickness, and a uniform layer thickness at the connection portion connected to the uniform layer thickness waveguide layer. A tapered waveguide layer having the same layer thickness as the waveguide layer and having a gradually decreasing layer thickness from the connection portion toward the end of the light-wave-wrapping layer; And the converging position with respect to the width direction of the optical waveguide by the lens element, and the converging position of the incoming waveguide light is emitted to the substrate side by the tapered waveguide layer and emitted from the end face of the substrate. Consistent with the focusing position in the thickness direction of the optical waveguide by the waveguide layer It is characterized in that it is set to be performed.

(Operation) The waveguide type optical head of the present invention is one in which a lens element, a light emitting element, and a light receiving element are integrated on an optical waveguide layer laminated on one surface of a substrate to form an optical waveguide. In particular, since the guided light can be focused in the width direction of the optical waveguide by the lens element formed in the optical waveguide layer,
The optical waveguide layer can be formed wider in the width direction of the optical waveguide, whereby the light emitting element, the light receiving element, and the lens element are arranged on the optical waveguide layer laminated on one surface of the substrate. An optical waveguide including the outward and return paths of light can be formed. Then, in the waveguide type optical head of the present invention, the tapered waveguide layer of the optical waveguide layer emits the guided light propagating through the uniform thickness waveguide layer to the substrate side, and the guided light is emitted from the end face of the substrate. It acts so as to be emitted, and acts so as to introduce reflected light reflected from a recording medium such as an optical disk and incident from the end face of the substrate into the uniform-thickness waveguide layer.

Further, by setting the focus position of the guided light by the lens element in the width direction of the optical waveguide and the focus position by the tapered waveguide layer in the thickness direction of the optical waveguide, the non-focus position at the focus position is set. Occurrence of astigmatism is prevented, and signal detection accuracy is improved.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 is a perspective view showing a schematic configuration of a waveguide type optical head showing an embodiment of the present invention, FIG. 2 is a schematic plan configuration diagram of the same waveguide type optical head, and FIG. The schematic side configuration diagrams of the optical head are respectively shown.

1 to 3, a waveguide type optical head 1 according to the present invention has optical elements other than an objective lens 9 integrated on the same substrate, and is laminated on one surface of a substrate 2. This is a waveguide side optical head in which optical elements such as a lens element 8, a light emitting element 4, and light receiving elements 5, 6 are integrated on the formed optical waveguide layer 3 to form an optical waveguide.

Here, the substrate 2 has a plane for forming an optical waveguide layer,
It has a lower refractive index than the optical waveguide layer and is transparent to guided light.

The optical waveguide layer 3 is laminated on one surface of the substrate 2. The optical waveguide layer 3 has a uniform layer thickness waveguide layer 3 b having a uniform layer thickness and a uniform layer thickness waveguide layer 3 b. The tapered waveguide layer 3a which is connected to the layer 3b and has a uniform thickness at the connection portion and has the same layer thickness as the waveguide layer 3b, and the layer thickness gradually decreases from the connection portion toward the end of the optical waveguide layer. The waveguide light propagating through the uniform thickness waveguide layer 3b is transmitted to the substrate 2 by the tapered waveguide layer 3a.
The light is emitted to the side and emitted from the end face 2 a of the substrate 2.

1 to 3, a semiconductor laser (LD) is usually used for the light emitting element 4, and is loaded on one end face of the substrate 2 and the end face of the optical waveguide layer 3 on the side of the uniform thickness waveguide layer 3b. From the optical waveguide layer 3.

The lens element 8 is a well-known condensing lens for an optical waveguide of a geodesic type, a Luneburg type, or the like.
Are provided integrally. The light receiving elements 5 and 6 each include a photodiode (PD) or the like, and are installed so as to receive light diffracted in two directions by an error detecting coupler 7 such as a grating coupler formed in the optical waveguide layer 3. I have.

Further, the objective lens 9 installed outside the substrate 2 is provided so as to be movable in the focus direction F and the track direction T of the recording medium.
The focus direction F and the track direction T are configured to be aligned.

Now, in the waveguide type optical head 1 configured as described above, light emitted from the semiconductor laser 4 transmits light from the end face of the optical waveguide layer 3 on the substrate 2 on the side of the uniform thickness waveguide layer 3b. The light enters the wave layer 3, is guided as two-dimensional diffused light in the waveguide layer 3b having a uniform thickness, and is collected by the condenser lens 8 in the waveguide layer.

Here, the light condensed by the condensing lens 8 is
The light is emitted toward the substrate 2 by the tapered waveguide layer 3a of the optical waveguide layer 3, and is emitted to the outside from the end face 2a on the substrate 2 side.

Then, the light emitted to the outside from the end face 2a on the substrate 2 side is condensed through the objective lens 9, and is focused on a recording medium surface (not shown) such as an optical disk.

The light focused on the recording medium surface and reflected and diffracted by the medium surface is incident on the substrate 2 again from the end face 2a of the substrate 2 through the reverse process, and is evenly distributed by the tapered waveguide layer 3a of the optical waveguide layer 3. It is guided into the thicker waveguide layer 3b. Then, the reflected light guided into the waveguide 3b having a uniform thickness passes through the condenser lens 8,
The light is diffracted in two directions by the error detecting coupler 7 and condensed on the light receiving surfaces of the photodiodes 5 and 6 installed in the respective diffraction directions.

Then, the received light amount of each of the photodiodes 5 and 6,
Detection of a recording signal and detection of an error signal such as a focusing error and a tracking error are performed based on the light condensing position and the like, and the actuator of the objective lens 9 is controlled based on the error signal, so that a deviation of the recording medium surface can be obtained. Adjustment of a focus position, a track position, and the like corresponding to the center runout is performed.

The configuration and operation of the waveguide type optical head 1 according to the present invention have been described above with reference to FIGS. 1 to 3, but in the waveguide type optical head according to the present invention, the optical components excluding the objective lens 9 are described. Since the optical elements are integrated into the element 2 and integrated on the substrate 2, the relative positions of these optical elements can be accurately determined, so that the operation such as adjustment after manufacturing is not required at all. In addition, by integrating the optical element on the substrate 2, it is possible to easily reduce the size and weight of the entire optical head as compared with an optical head formed of bulk optical components. Further, since the structure itself is simplified, assembling is easy, aging does not easily occur, and an inexpensive and high-performance optical head can be obtained.

By the way, in the case of the conventional waveguide type optical head, when the reflected light from the recording medium surface is received, the reflected light is incident on the waveguide layer due to the displacement of the medium surface due to the core deflection or the surface deflection of the recording medium surface. When the position is shifted, there is a problem that the efficiency of incidence of the reflected light on the waveguide layer is significantly reduced, and the detection accuracy is reduced.

However, in the waveguide type optical head according to the present invention, the optical waveguide layer 3 has a uniform thickness and a uniform thickness.
And a taper which is connected to the uniform layer thickness waveguide layer 3b and has a thickness equal to that of the uniform layer thickness waveguide layer 3b at the connection portion and gradually decreases from the connection portion toward the end of the optical waveguide layer. Waveguide layer 3a, so that guided light propagating through the uniform layer thickness waveguide layer 3b is radiated to the substrate side by the tapered waveguide layer 3a and emitted from the end face 2a of the substrate 2. Light reflected from the recording medium surface enters the substrate from the end face 2a of the substrate 2 and is guided into the uniform thick waveguide layer 3b by the tapered waveguide layer 3a of the optical waveguide layer 3. Even if the incident position of the reflected light slightly shifts due to the displacement of the recording medium, etc., the reflected light is incident from the large substrate-side end face 2a, and the tapered waveguide is formed. Since the light is guided into the waveguide layer 3b having a uniform thickness by the layer 3a, the influence on the above-mentioned shift is small, and the detection of the reflected light is ensured. Is performed.

By the way, the optical waveguide layer 3 has a uniform thickness and a uniform thickness.
3b and a tapered waveguide layer 3a, and the guided light propagating through the uniform thickness waveguide layer 3b is
When the light is radiated to the substrate 2 side by 3a and is emitted from the end face 2a of the substrate 2, the tapered waveguide layer 3a as shown in FIG. When the focus position a of the light is shifted from the focus position b of the light guided by the condenser lens 8 in the width direction W of the optical waveguide as shown in FIG. 4B, the light is focused on the recording medium surface. There is a problem that astigmatism occurs in the converged light that is emitted and the converged light of the reflected light that is condensed on the light receiving element, and the detection accuracy is greatly reduced. That is, there is a problem of matching at the light entrance and exit portions.

Therefore, in the present invention, the focus position b of the light guided by the condenser lens 8 in the width direction W of the optical waveguide coincides with the focus position a of the tapered waveguide layer 3a in the thickness direction Z of the optical waveguide. The focusing position by the condensing lens and the tapered waveguide layer is adjusted so as to perform the focusing. That is, the focusing position by the condenser lens 8 and the focusing position by the tapered waveguide layer 3a are set so that the two focusing positions a and b coincide with each other. Then, by setting as described above, by taking the consistency at the light entrance and exit portions, the occurrence of astigmatism at the focusing position on the recording medium surface and the light receiving elements 5 and 6 is prevented, and recording signal detection and That is, the error signal is detected with high accuracy.

In the illustrated embodiment, the case where the light converging positions b and a by the condensing lens 8 and the tapered waveguide layer 3a are set at the same position in the substrate 2 is shown. The coincidence point may be set outside the substrate. Further, the various optical elements loaded on the substrate and the arrangement positions thereof are not limited to those shown in the drawings, and various implementations are possible.

(Effects of the Invention) As described above with reference to the illustrated embodiment, the waveguide type optical head according to the present invention includes a lens element, a light emitting element, a light emitting element, and an optical waveguide layer laminated on one surface of a substrate. An optical waveguide is formed by integrating a light receiving element. In particular, since the guided light can be focused in the width direction of the optical waveguide by the lens element formed on the optical waveguide layer, the optical waveguide is formed by the optical waveguide. The light emitting element, the light receiving element, and the lens element are arranged on the optical waveguide layer laminated on one surface of the substrate, so that the forward and backward paths of light can be formed. It is possible to form an optical waveguide including the optical waveguide. And since it is a waveguide type optical head using the optical waveguide as a main component, it is easy to assemble, and adjustment after assembling is unnecessary, so that production cost can be greatly reduced.

Further, since the optical waveguide layer, the optical element, the light receiving element, and the like are provided integrally on the same substrate, the size and weight of the entire optical head can be easily reduced.

In the waveguide type optical head according to the present invention,
The optical waveguide layer comprises a uniform thickness waveguide layer, and a tapered waveguide layer whose thickness gradually decreases from a connection portion of the uniform thickness waveguide layer toward an end of the optical waveguide layer. It is configured such that guided light propagating through the thick waveguide layer is emitted to the substrate side by the tapered waveguide layer and emitted from the end face of the substrate, and reflected light from the recording medium surface is Since the light is incident into the substrate from the end face of the substrate and guided into the uniform-thickness waveguide layer by the tapered waveguide layer of the optical waveguide layer, the reflected light is displaced by the recording medium side or the like. Even if a slight shift occurs in the incident position, the reflected light is incident from the end face on the substrate side having a large area and is guided by the tapered waveguide layer into the uniform-thickness waveguide layer. ,
Detection of the reflected light is reliably performed.

In the present invention, the focus position of the guided light by the lens element in the optical waveguide layer in the width direction of the optical waveguide is set to coincide with the focus position of the tapered waveguide layer in the thickness direction of the optical waveguide. As a result, astigmatism is prevented from occurring at the focal position on the recording medium surface and the light receiving element, and the detection accuracy at the time of recording signal detection and error signal detection is greatly improved.

Therefore, according to the present invention, it is possible to provide a small-sized, light-weight, and inexpensive waveguide-type optical head. A waveguide optical head can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a waveguide type optical head showing one embodiment of the present invention, FIG. 2 is a schematic plan view of the same waveguide type optical head, and FIG. FIG. 4 (a) is a schematic side view of the head, FIG. 4 (a) is an explanatory view showing the focusing position of light in the thickness direction of the optical waveguide by the tapered waveguide layer of the above-mentioned waveguide type optical head, and FIG. FIG. 5 is an explanatory view showing a focus position of light in a width direction of an optical waveguide by a lens element of the waveguide optical head, FIG. 5 is a schematic side view showing an example of a conventional bulk optical head, and FIG. FIG. 3 is a schematic side view of a main part of the waveguide type optical head, showing positions where light enters and exits from the waveguide type optical head. DESCRIPTION OF SYMBOLS 1 ... Waveguide type optical head, 2 ... Substrate, 2a ... Substrate end face, 3 ... Optical waveguide layer, 3a ... Tapered waveguide layer, 3b ...
Uniformly thick waveguide layer, 4 …… Light-emitting element, 5,6 …… Light-receiving element,
7: Coupler for error detection, 8: Lens element, 9:
Objective lens.

Claims (1)

(57) [Claims] 1. A waveguide type optical head in which a lens element, a light emitting element, and a light receiving element are integrated on an optical waveguide layer laminated on one surface of a substrate to form an optical waveguide. The optical waveguide layer constituting the waveguide layer has a uniform layer thickness and a uniform thickness, and the connecting portion has the same layer thickness as the uniform thickness waveguide layer at a connection portion. And a tapered waveguide layer whose thickness gradually decreases toward the end of the optical waveguide layer, and guided light propagating through the uniform thickness waveguide layer is radiated to the substrate side by the tapered waveguide layer. And the focusing position in the width direction of the optical waveguide of the guided light by the lens element and the focusing position in the thickness direction of the optical waveguide by the tapered waveguide layer. The waveguide type optics is characterized by being set to match. Good.