JPH06119654A - Optical pickup - Google Patents

Abstract

PURPOSE:To provide an optical pickup by which a device using an optical pickup is miniaturized and a light beam is effectively utilized to perform a highly efficient light detection. CONSTITUTION:On the surface of a substrate 1 with a through-hole 7, a clad layer 2 is formed and also an optical waveguide 3 with a tapered part 10 on the edge from one opening part of the through-hole 7 of the substrate 1 to one side edge part is provided. Then, a light beam emitted from a laser diode 6 that is provided in the other opening of the hole 7 is transmitted through the hole 7 and the clad layer 2, emitted from the center part of a quadripartite photodiode 4, and converged on an optical disk D through an objective lens 9 to read out information. After that, the reflected light from this optical disk D is converged on the center of the quadripartite diode 4 through the objective lens 9; and this converged reflected light is taken in the optical waveguide 3 from the tapered part 10 of the waveguide 3 and is detected by means of photodetectors 5a, 5b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup using an optical waveguide type optical element for transmitting and branching laser light and the like.

[0002]

2. Description of the Related Art In recent years, as an optical pickup used in an optical disc player such as a CD (Compact Disc) player, an optical pickup using an optical waveguide type optical element as shown in FIG. 4 has been proposed.
The one shown in this figure is disclosed in Japanese Patent Laid-Open No. 64-60831, and is constructed as follows.

In FIG. 4, reference numeral 21 is a silicon substrate, and an optical waveguide 22 is formed on the surface of the silicon substrate 21 via a buffer layer. A grating beam splitter 23 and a grating coupler 24 are formed on the surface of the optical waveguide 22. A laser diode 25 as a light source is provided at one end of the optical waveguide 22.
Is provided, and the photodetectors 26a, 26a are sandwiched by the paths of the guided light emitted from the laser diode 25.
b are arranged to face each other.

When reproduction of the compact disc is started, a laser beam is emitted from the laser diode 25, and the emitted laser beam is emitted from the laser diode 2.
5 is transmitted to the optical waveguide 22 which is end-face coupled with 5 to become guided light, which passes through the grating beam splitter 23 and reaches the grating coupler 24.

In the grating coupler 24, the guided light that has arrived is diffracted into a condensed beam, which is irradiated onto the optical disk 27. On the signal surface of the optical disk 27, a minute spot (focus point) is generated by the above-mentioned focused beam,
The reflected light again enters the grating coupler 24 and becomes reflected guided light.

This reflected guided light is diffracted by the grating beam splitter 23 and transmitted toward the photodetectors 26a and 26b. Photodetectors 26a and 26
b outputs a reproduction signal, a focus error signal and a tracking error signal based on the detected reflected guided light, and the focus error signal and the tracking error signal among these signals are fed back to a drive mechanism (not shown). As a result, the optical pickup 20
The distance between the optical disc 27 and the optical disc 27 is always kept at an appropriate distance, and the focal point of the focused beam is tracked so as not to deviate from the tracking of the optical disc 27.

However, the above-described optical pickup of FIG. 4 requires extremely advanced fine processing technology and design / production technology to form the grating beam splitter 23 and the grating coupler 24, and it is difficult to reduce the cost of the product and mass produce it. There is a problem to say. Therefore, in order to solve such a problem, for example, Japanese Patent Laid-Open No. 3-209204
There is a proposal as disclosed in Japanese Patent Publication No. JP-A-2003-242242, which discloses an optical pickup avoiding the use of a grating. The structure shown in this publication is configured as shown in FIG.

In the figure, 31 is a substrate made of gallium arsenide or the like, 32 is a first optical waveguide formed on the substrate 31, and 33 is a substantially L-shaped second optical waveguide formed on the substrate 31. is there. One end 32a of the first optical waveguide 32
And the bent portion 33a of the second optical waveguide 33 is a boundary surface 34
Through.

The first and second optical waveguides have different refractive indexes. Reference numeral 41 denotes a laser diode, and the light emitted from the laser diode 41 enters the optical waveguide 32 from the end portion 32b of the optical waveguide 32 and reaches the end portion 33b of the optical waveguide 33 through the boundary surface 34.

A four-divided photodiode 4 is provided at the end 33b.
3 is provided. The four-division photodiode 43 is
It is configured by joining four square plate-shaped photodiode cells with one side being in contact with each other with their sides in contact with each other, and a minute transmission hole for passing a laser beam from the laser diode 41 is formed in the center. Has been done. Therefore, the light is condensed from the transmission hole of the four-division photodiode 43 toward the objective lens 42, and a minute spot is generated on the optical disc D.

The signal light reflected on the recording surface of the optical disc D passes through the objective lens 42 again and is condensed toward the center of the four-division photodiode 43, and is transmitted from the transmission hole of the four-division photodiode 43 to the end of the optical waveguide 33. It is incident on the portion 33b. Then, a part of the incident signal light is reflected by the boundary surface 34 and transmitted to the end portion 33c, and the rest passes through the boundary surface 34 and is transmitted to the end portion 32b. The reflected signal light is detected by the photodiodes 44a and 44b provided at the end 33c.

[0012]

However, the above-described optical pickup having the structure shown in FIG. 5 has a vertically long structure extending in a direction intersecting with the disc surface of the optical disc D. There is a limit to the downsizing of devices that employ pickups, and it is difficult to meet the recent demand for downsizing and thinning of various devices including CD players.

When the light emitted from the laser diode 41 is applied to the optical disc D through the optical waveguides 32 and 33, the light other than the central portion of the four-divided photodiode 43, that is, the light passing through the transmission hole. Other than that, it is cut off by being blocked by the 4-division photodiode 43,
The laser light emitted from the laser diode, which is the light source, has not been effectively used. Therefore, when reading information from the optical disc D, the output of the light source must be increased,
There is a lot of waste. And, this means that a light source with a large output is unnecessarily required at a practical level, which leads to an increase in the cost of the device and also goes against energy saving.

In the process of manufacturing the pickup,
Each pickup has to be bonded to each laser diode, which is troublesome and lacks mass productivity.

The present invention has been made in consideration of such a situation, and an object thereof is optimum for downsizing of an apparatus and high efficiency by effectively utilizing output light of a light source. An object is to provide an optical pickup capable of detecting light. Another object of the present invention is to provide an optical pickup that is easy to manufacture and has high mass productivity.

[0016]

In order to achieve the above object, the present invention provides a plate-shaped substrate having a through hole penetrating both surfaces and a clad layer formed on the surface thereof, and the transparent substrate on the substrate. A light guide body which is provided from one opening of the hole to one side edge and has a taper portion of a predetermined angle formed at an end corresponding to the one opening of the through hole; A multi-divided light receiving element which is provided with a center located in one opening of the through hole, and in which light receiving elements are arranged around the center and a light transmitting hole is provided in the center, A light source provided in the other opening of the through hole, a condensing lens that imparts astigmatism to the light from the light source and condenses the light into the light transmitting hole of the multi-segment light receiving element, and Astigmatism of light emitted through the center of the split photodetector A lens system for correcting and condensing the reflected light from the information recording medium into a light transmitting hole of the multi-divided light receiving element, and a taper portion of the light guide from the multi-divided light receiving element And a photodetector for detecting the light transmitted through.

Secondly, each surface emitting laser element of the surface emitting laser array includes a surface emitting laser array in which a large number of surface emitting laser elements are formed on one substrate and a pickup including a substrate, a clad layer and a light guide. Using a plurality of pickup arrays formed with a positional relationship corresponding to, the pickup array is bonded and integrated on the surface emitting laser array, and then the array is divided into individual element units.

[0018]

As a result of taking the above means, the following effects occur. That is, in the case of the first configuration, the light emitted from the light source is sent to the opposite surface through the through hole formed in the substrate, where the lens system collects the light on the signal surface of the information recording medium to read the information. At the same time, a light guide is provided from one opening of the through hole to one side edge, and a tapered portion formed at an end of the light guide is used to take in reflected light from the information recording medium. The distance from the information recording medium to the information recording medium depends only on the thickness of the substrate and the clad layer and the focal length of the lens system. As a result, the conventional optical pickup having a vertical configuration with respect to the information recording medium. The size of the device can be greatly reduced as compared with the case of using. Further, since the light is focused on the central portion of the multi-divided light receiving element by the condenser lens, the light from the light source can be effectively used, and thus highly efficient light detection can be performed.

Further, the condensing lens imparts astigmatism to the light, and the lens system has a characteristic that only the light reflected from the information recording medium becomes light having astigmatism. Therefore, the focus error signal can be detected by the astigmatism method, which has good detection sensitivity of the focus point and can downsize the optical system. It can be detected accurately.

Further, according to the second structure, the light source and the optical waveguide pickup are arrayed and joined, respectively, and then cut into individual elements to be separated, whereby the laser diode as a light source is individually separated. Since it is not necessary to adhere to, the manufacturing efficiency can be greatly improved. This makes it possible to obtain an optical pickup that is easy to manufacture and highly productive.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1A is a perspective view showing the structure of an optical pickup according to the first embodiment of the present invention. Further, FIG. 1 (b) shows I in FIG. 1 (a).
It is sectional drawing by -I '.

In FIG. 1, 1 is a rectangular silicon (S
i) A substrate, and a through hole 7 for light transmission that penetrates the silicon substrate 1 is formed in the center of the silicon substrate 1. Moreover, for example, SiO2 is formed on the surface of the silicon substrate 1.
A clad layer 2 made of glass is formed. At the center of the surface of the clad layer 2, a four-division photodiode 4 having a hole for transmitting light in the center is attached.

A laser diode (LD) 6 serving as a light source is attached at the position of the through hole 7 on the back surface of the silicon substrate 1. Further, inside the through hole 7, there is provided a condenser lens 8 for condensing the light emitted from the laser diode 6 at the center of the four-divided photodiode 4. The condenser lens 8 has astigmatism.

The clad layer 2 is provided with an optical waveguide 3 having a predetermined width from the central portion where the four-divided photodiode 4 is attached to one side edge portion. The optical waveguide 3 is for guiding light and is made of, for example, barium alumina borosilicate glass such as Corning 7059 manufactured by Corning Incorporated, USA. And 4 of this optical waveguide 3
A taper portion 10 is formed at the end portion on the side of the divided photodiode 4 so that the elevation angle with respect to the surface of the silicon substrate 1 has a predetermined angle.

The tapered portion 10 is located between the four-divided photodiode 4 and the laser diode 6, and the angle formed by the boundary with the cladding layer 2 is vertically incident from the objective lens 9 through the four-divided photodiode 4. The optimum angle is set in advance so that a part of the returned light can be taken into the optical waveguide 3.

The four-divided photodiode 4 is formed by joining four rectangular plate-shaped photodiode cells with one side being in contact with each other with their sides in contact with each other, and the laser beam from the laser diode 6 is placed at the center. A minute transmission hole 4a for passing through is formed.

Reference numeral 9 denotes an objective lens, which is used for transmitting the incident light through the transmission hole 4a of the four-division photodiode 4 to the optical disk D
At the same time, the reflected light (return light) from the optical disc D is condensed toward the central transmission hole 4a of the four-divided photodiode 4. The objective lens 9 has a characteristic of correcting the astigmatism of only the incident light from the condenser lens 8. 5a and 5
Reference numerals b are photodetection photodiodes, which are provided in the silicon substrate 1 in contact with one end of the optical waveguide 3.

Now, in such a structure, the light emitted from the laser diode 6 is made incident on the condenser lens 8 to become light having a predetermined astigmatism, and this light is transmitted through the through hole 7.
Then, the light passes through the clad layer 2 and is condensed on the central portion of the four-divided photodiode 4, and is emitted upward through the transmission hole 4a in the central portion. The emitted light is the objective lens 9
After being corrected by the astigmatism so as to remove the astigmatism, the light is focused on the optical disc D to form a minute spot on the information recording surface.

On the other hand, the return light due to the reflection from the optical disk D is incident on the objective lens 9 again and is condensed on the transmission hole 4a in the central portion of the four-division photodiode 4. At this time, the return light has astigmatism, and when the distance between the objective lens 9 and the optical disc D changes, the defocus due to the change appears as a change in beam shape on the 4-division photodiode 4 and 4-division. Since it is detected by the photodiode 4, a detection signal due to this change is obtained as a focus error signal.

A part of the return light that has passed through the transmission hole 4a of the four-division photodiode 4 is part of the tapered portion 1 of the optical waveguide 3.
It is reflected at 0, the rest is transmitted and goes straight. Tapered part 10
The return light reflected by is taken into the optical waveguide 3 as guided light, is transmitted to the photodiodes 5a and 5b for detecting light in the optical waveguide 3, and is detected as a reproduction signal. At this time, a tracking error signal is also detected, and the detected tracking error signal is fed back to an optical pickup driving mechanism (not shown) for tracking servo control.

The optical pickup driving mechanism adjusts tracking by driving the entire optical pickup according to the polarity of the supplied tracking error signal. The tracking error signal is detected by, for example, the push-pull method.

On the other hand, the focus error signal detected by the four-division photodiode 4 is fed back to an objective lens driving mechanism (not shown) and used for focusing servo control. The objective lens drive mechanism is
Focusing is adjusted by driving the objective lens 9 in the optical axis direction according to the polarity of the supplied focus error signal.

As described above, in the first embodiment, the cladding layer 2 made of SiO 2 glass is formed on the surface of the silicon substrate 1 and the through holes 7 penetrating both sides of the silicon substrate 1 are formed, and the silicon substrate 1 is also formed. An optical waveguide 3 made of barium alumina borosilicate glass having a refractive index different from that of SiO2 glass is provided from one opening of the through hole 7 to one side edge, and in this state, the through hole 7 of the silicon substrate 1 is formed. The light emitted from the laser diode 6 provided in the other opening of the optical disc D is sent to the opposite surface through the through hole 7 and the cladding layer 2, and the objective lens 9 is used to drive the optical disc D.
The information is read by forming a minute spot on the information recording surface, and the reflected light from the optical disc D is reflected at the boundary between the taper portion 10 formed at the end of the optical waveguide 3 and the SiO2 glass 2. Since the light is taken in the optical waveguide 3, the distance from the laser diode 6 as the light source to the optical disk D depends only on the thickness of the Si substrate 1 and the cladding layer 2 and the focal length of the objective lens 9. As a result, the device can be significantly downsized as compared with the case of using the conventional vertical type optical pickup. Further, since the laser light from the laser diode 6 which is the light source is focused on the central portion of the four-division photodiode 4 by the condenser lens 8 provided on the emission side of the laser diode 6, the laser light is emitted from the laser diode 6. The emitted light can be effectively utilized, which enables highly efficient light detection.

Further, astigmatism is given to the light by using the condenser lens 8, and only the returning light from the optical disk D is made incident on the four-division photodiode 4 as the light having the astigmatism by the objective lens 9. The focus error signal can be detected by the astigmatism method, which has good focus point detection sensitivity and allows the optical system to be miniaturized. The behavior of D in the vertical direction can be detected with higher accuracy than in the past. (Second embodiment)

As described above, the miniaturization can be realized, the utilization efficiency of the emitted light of the light source can be improved, and the light source having a small light emission output can be sufficiently provided, and energy saving and cost reduction can be achieved. It was a possible example. next,
A second embodiment will be described as an embodiment of an optical pickup which has a simple structure and is easy to manufacture, and is thus highly productive.

FIG. 2 is a perspective view showing an example using a surface emitting laser element as a light source. The structure is basically the same as that of FIG. 1. Therefore, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

In FIG. 2, the light source 6 shown in FIG.
Instead of this, a surface emitting laser element 11 is used. The surface emitting laser element 11 is obtained by dividing it from an array as shown in FIG.

FIG. 3 shows a surface-emission laser array as one manufacturing step. A surface-emission laser array 16 in which a plurality of such surface-emission laser devices 11 are formed on a single substrate is prepared in advance. Keep it. Further, a pickup array 17 is prepared in which a plurality of optical waveguide pickups not provided with a light source are formed as an array.

That is, the pickup array 17 is a surface emitting laser array 16 which is an optical waveguide pickup including a silicon substrate 1 having the configuration shown in FIG. 1, a cladding layer 2 having the configuration shown in FIG. 1 and an optical waveguide 3 having the configuration shown in FIG. A plurality of surface emitting laser elements 11 are formed in such a positional relationship as to correspond one-to-one.

Then, the pickup array 17 is bonded onto the surface emitting laser array 16. As a result, the optical waveguide pickups are bonded on the surface-emitting laser element 11 so as to form a pair, so that the pickup module is completed by dividing the array into individual elements.

As described above, the light source and the optical waveguide pickup are arrayed and joined together, and then cut into individual elements to be separated, so that it is not necessary to individually bond the laser diodes as the light source, and it is possible to greatly It is possible to improve manufacturing efficiency. This makes it possible to obtain an optical pickup which has a simple structure and is easy to manufacture, and is thus highly productive.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention. For example, the clad layer and the optical waveguide are formed on the silicon substrate, but a substrate other than the silicon substrate can be used, and the 4-division photodiode is not limited to the photodiode, and other light receiving elements can be used. Besides, the number of divisions is not limited to four.

[0044]

As described in detail above, according to the present invention, a clad layer is formed on the surface of a silicon substrate having through holes penetrating both sides thereof, and at the same time, one opening of the through hole is formed on the substrate. A light guide body is provided which extends over one side edge and has a taper portion with a predetermined angle formed at an end portion corresponding to one opening portion of the through hole, and in this state, is provided in the other opening portion of the through hole of the substrate. The light from the light source is sent to the opposite surface through the through hole and the clad layer, where a minute spot is generated on the signal surface of the information recording medium by the lens system to read the information, and the light from the information recording medium light is emitted. Since the reflected light is taken into the light guide body and detected by the taper portion, the device can be significantly downsized as compared with the case where the conventional vertical optical pickup is adopted.

A four-division photodiode provided on the surface of the clad layer corresponding to one opening of the through hole,
A condenser lens is provided between the light source provided in the other opening of the above-mentioned through hole, and the condenser lens collects the light in the center of the four-division photodiode, so that the light from the light source is effective. Can be used for high efficiency light detection.

Further, the condensing lens is provided with astigmatism, and the lens system is provided with the characteristic that only the reflected light from the information recording medium becomes light with astigmatism. It becomes possible to detect the behavior of the recording medium in the vertical direction with higher accuracy than in the past.

Furthermore, an array having a large number of light guides (optical waveguides) and an array having a large number of surface-emitting laser elements are prepared, and the both are bonded together and then cut into element-by-element divisions. By doing so, the pickup can be manufactured efficiently and the cost can be reduced.

[Brief description of drawings]

1A and 1B are views showing a configuration of an optical pickup according to a first embodiment of the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a sectional view.

FIG. 2 is a sectional view showing a configuration of an optical pickup according to a second embodiment of the present invention.

FIG. 3 is a drawing for explaining the manufacturing process of the optical pickup according to the second embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of an optical pickup according to a conventional example.

FIG. 5 is a perspective view showing a configuration of an optical pickup according to a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon (Si) substrate 2 ... Clad layer 3 ... Optical waveguide 4 ... 4-division photodiode 4a ... Transmission hole 5a, 5b ... Photodetection photodiode 6 ... Laser diode (LD) 7 ... Transmission hole 8 ... Condensing lens Reference numeral 9 ... Objective lens 10 ... Tapered portion 11 ... Surface emitting laser element 16 ... Surface emitting laser array 17 ... Pickup array D ... Optical disk.

Claims (1)

[Claims] 1. A plate-shaped substrate having a through-hole penetrating both sides and having a clad layer formed on the surface thereof, and provided from one opening of the through-hole on the substrate to one side edge portion, And a light guide body having a tapered portion formed at a predetermined angle at an end portion corresponding to one opening portion of the through hole; and a light guide body having a center located at the one opening portion of the through hole on the clad layer surface. At the same time, a multi-divided light receiving element is formed by arranging light receiving elements around the center and providing a light transmitting hole in the center, and a light source provided in the other opening of the through hole of the substrate, A condensing lens that imparts astigmatism to the light from the light source to condense it in the light transmitting hole of the multi-segment light receiving element, and light emitted through the center of the multi-segment light receiving element by the condensing lens. The astigmatism of is corrected and condensed on the information recording medium. A lens system for condensing reflected light from a recording medium into a light transmitting hole of the multi-divided light receiving element, and a light detection for detecting light transmitted from the multi-divided light receiving element through a tapered portion of the light guide. An optical pickup having a container.