JPS6236753A - Waveguide type optical pickup head - Google Patents

Abstract

PURPOSE:To improve the matching properties between the substrate materials together with the facilitated molding and the reduction of cost and to attain the tracking at a high speed, by using a semiconductor laser having a function to deflect the output light to a light source. CONSTITUTION:A planar type waveguide 12 is formed on an LiNbO3 sybstrate 11 with dispersion of Ti and a semiconductor laser, i.e., a beam scanning laser BSL13 having a deflecting function for output light is provided at the light incident end of the waveguide 12. While a waveguide lens for instance, runeburg lens, geographic lens, etc. 14 and a grating 15 are provided in the middle of the waveguide 12 from the light incident end through the light output end together with a photodetector 16 set near the output end. The BSL13 is set at the focal point position of the lens 14. Thus the light delivered from the BSL13 is transmitted through the waveguide 12 and made incident on the lens 14. The light made incident on the lens 14 is collimated and made incident on the grating 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveguide type optical pick-up device for recording and reproducing information on an optical disk, and particularly to means for simplifying the structure.

[Prior art]

Optical disk systems, which are high-density information recording systems using laser light, are attracting attention as information systems that will support the rapidly developing information society. Active research and development is being conducted to further improve the functionality of optical disc systems, including video discs, which have already been put into practical use. The optical pickup head in such an optical disk system corresponds to the pickup cartridge of an analog grayer, and can be said to be an extremely important component for the optical F4 disk system.

The optical pickups that have been developed so far! The heads are all semiconductor lasers, lenses, and mirrors.

Individual optical elements such as polarizing beam slits are arranged on a metal substrate. Therefore, it is difficult to make it smaller and lighter, and it has the disadvantage of having a large number of parts.

As a means to solve these problems, an optical pickup head using a waveguide has been proposed, for example, as disclosed in Japanese Patent Application Laid-open No. 59-151129.

FIG. 12 is a diagram showing an outline of the structure. As shown in the figure, a LINbO3 substrate 2 is placed on a silicon substrate 1, and a waveguide 2a is formed in the upper layer thereof. A semiconductor laser 3 is installed at the light input end of the waveguide 2a, and an integrated lens 4 is bonded to the light output end. In the middle of the waveguide 21, from the light input end side to the light output end side,
A collimating lens 5 collimates the light emitted from the semiconductor laser 3, a crossed electrode 6 generates a surface acoustic wave for Bragg diffraction of the collimated light beam, and polarizes the diffracted light within the cross section of the waveguide 2a. Grating lenses 7 are sequentially arranged. In addition, a photodetector 8 consisting of six photodiodes is mounted on one side of the silicon substrate l.
is the provision. A control circuit 9 composed of a microcomputer is provided on the upper surface of the silicon substrate 1, and includes the integrated lens 4, crossed electrodes 6. grating lens 7,
It is electrically connected to the photodetector 8 and the like. In this way, the laser light emitted from the semiconductor laser 3 propagates through the waveguide 2a, and the propagated light beam is converted into light 7'' by the integrated lens e4.
The condensed light is irradiated onto pits (not shown) on the fourth screen 10. The reflected light from the optical f4 disk 10 is received by a photodetector 8, and the state of the optical curvature formed on the optical disk 10, that is, focusing information, tracking information, and king information, etc. is detected. .

[Problem that the invention seeks to solve]

However, the conventional optical big-wave device with the above structure has the disadvantage that the matching between the silicon forming the substrate of the control circuit 9 and the L1NbOs forming the substrate of the waveguide 2a is poor. are doing. In addition, since the waveguide 2a is provided with intersecting electrodes 6 and grating lenses 7 for generating surface acoustic waves for Bragg diffraction of light, an extremely complicated manufacturing process is required, and it is difficult to reduce costs. It had the disadvantage of being difficult. Furthermore, a semiconductor laser 3 which is a light source is mounted on the same substrate. It is difficult to integrate the photodetector 8 etc. with the waveguide 2a;
In this respect as well, there was a problem in that manufacturing was difficult and the cost was inevitably high.

Here, the present invention provides a waveguide type optical picker and an f-head that are free from problems of consistency between substrate materials, are extremely easy to manufacture, can reduce costs, and can perform high-speed tracking. The purpose is to

[Means for solving problems]

In order to solve the above problems and achieve the objects, the present invention is characterized by taking the following measures. That is, a waveguide is provided to guide the light incident from the light input end to the light output end, a semiconductor laser having an output light polarization function is installed at the light input end of this waveguide, and the output light from the semiconductor laser is A collimating lens is provided within the waveguide to form a parallel beam of light, and the collimating lens diffracts the collimated light to convert the emitted light into a spot, which is emitted from the light emitting end of the waveguide toward the optical disk. A grating having diffraction gratings having different spatial frequencies is provided in the waveguide, and a detection means is provided to receive reflected light from the optical disk and detect focus information and tracking information.

[Effect]

Since a semiconductor laser with the function of deflecting the emitted light is used as a light source, it is only necessary to provide a collimating lens and grating in the waveguide on the substrate formed of a single material.
There is no need to provide intersecting electrodes for surface acoustic wave generation for Bragg diffraction. Moreover, a semiconductor laser as a light source and a photodetector can be integrated with the waveguide, and tracking can be performed by deflection scanning of the semiconductor laser.

〔Example〕

FIG. 1 is a perspective view showing the overall configuration of a first embodiment of the present invention. In FIG. 1, reference numeral 1 indicates a L i Nb Os substrate, on which a Brehner-type ring wave path 12 formed by TI diffusion is provided.

At the light transmission end of this waveguide 120, there is a semiconductor laser, that is, a beam scanning laser (hereinafter referred to as BS), which has an output light deflection function.
A waveguide lens 14 (abbreviated as L) 13 is provided in the middle of the waveguide 12 from the light input end to the light output end.
A grating 15 is provided, and a photodetector 16 is provided near the output end. Naori SL￥=
#/ will be explained in detail later.

The waveguide lens is installed at the focal point of e14. The laser light emitted from the BSL 13 propagates through the waveguide 12 and enters the lens 14. The light incident on the lens 14 is collimated and then incident on the grating 15.

Since this grating 15 is formed so that the spatial frequency of the diffraction grating is different at each position, the diffraction angle at each position changes, and an original spot is formed on the optical disk 10. The reflected light from the optical disk 10 is incident on a photodetector 16 attached near the output end of the substrate 11, and focusing information and tracking information of the optical spot on the optical disk 10 are detected.

Next, the 17 (BSL) 13 shown in FIG. 1 will be explained.

Semiconductor laser beams are generally classified into two types depending on their waveguide mechanism: refractive index waveguide type and gain waveguide type. The former is
It has a mechanism in which light is guided by the refractive index in both the perpendicular and parallel directions to the junction surface of the active layer of a semiconductor laser, whereas the latter depends on the carrier density injected into the active layer. It has a mechanism based on the property that light is guided along areas with high gain.

BSL 1 j actively utilizes this gain waveguide mechanism. That is, the distribution in the active layer of a typical gain waveguide l-type semiconductor laser is symmetrical with respect to the center of the active layer because the current injection electrode is uniformly formed on the active layer. On the other hand, in the case of BSL 1 j, two divided electrodes are formed on the active layer,
Furthermore, since current can be independently injected into this pair of electrodes, the gain distribution within the active layer can be made asymmetric.

Figure 2 is a perspective view showing an example of the structure of BSL IJ;
Literature rD, R, 5clfr@+s ApI)l phy
s L@tt 33(8), 702, 1978J.

As shown in FIG. 2, an n-type G
a, 5At (15As cladding layer 22, p-type G & 11
95Atao sAl active layer 23, p type” (LSAtl
lL5AJ cladding layer 24 and! The lff1GaAa cap layer 25 is provided with forward electrodes 27a*27b. In other words, the electrodes 27 and 27bFi are separated at the electrode dividing portion 28, and the pair of leads 111
129 fields.

Currents I, , I2 can be injected independently through 29b. Further, the electrode 27h of the casso layer 25
, 27b are provided with Zn diffusion regions 30h and 30b, respectively.
The current excitation region injected from b is limited.

The asymmetric gain distribution in the active region 31 of the active layer 237 is achieved by changing the ratio of the injection currents I, , I, described above.

That is, if the injection current is made asymmetrical (I, I, )K, then
The density of carriers injected into the active layer 23 is higher on the electrode side where the injection current is larger.

For example, when It>I, more carriers are injected from the electrode 27m side, and the gain in the active region 3 becomes higher on the 11 side. Therefore, the gain distribution O peak is 27agIIK
It shows a biased distribution as shown in Figure 3 (,). Reverse KIt
When <Is, the gain in the active region 3 becomes higher on the side 27b, resulting in a distribution as shown in FIG. 3(b) in which the peak of the gain distribution is biased toward the side 27b. Figure 3(a), (
It can be seen that when the gain distribution shown in b) is formed, the phase of the wavefront of the optical mode of the active layer 23 becomes a tilted wavefront as shown in FIG. 4(,)(b). Indicates the direction parallel to the slope of the wavefront.

The direction of the laser emitted light has a peak in the direction in which the light within the active layer 23 is deflected by a predetermined angle.

This emitted light peak position is the peak position of the output light to the active layer 23.
The characteristic of the operation of J as a light source is that the peak P of the intensity distribution of the emitted light is determined by the injection current ratio It
/I! (by variable operation) can be continuously deflected as shown by the arrow.

Therefore, as shown in FIG. 6(b), BSL 7 J
By placing the laser output end face on the focal point of the lens (f is the focal length), the parallel light beam after passing through the lens 3 is translated in parallel as shown by the arrow V in response to the beam deflection movement of the laser beam as shown by arrow V. It becomes possible to do so.

In other words, due to the combination of BSL I J and lens 14, υ,
By simply performing beam scanning of the BSL IJ light source, parallel movement of the parallel light beam can be easily realized without using a surface acoustic wave generating element.

Since the beam scanning frequency of Naori SL 13 is possible up to the modulation frequency range of a semiconductor laser,
Capable of high-speed tracking. Next, focusing and tracking information detection means will be explained.

7 Orcusing information is detected by detecting the light spot position of the reflected light irradiated onto the photodetector 16 attached near the output end of the waveguide 12, as shown in FIG.
It is done. In other words, the distance t between the light output end of the waveguide 12 and the optical disc 10 is determined by the reflected light beam I, as shown in FIG. If the initial setting is made so that the beam is irradiated to the center position of the photodetector 16, the defocused A
Alternatively, in the case of B, the light beams are formed at positions shifted from the center to the left and right.

Further, the spot diameter of the reflected light at that time becomes smaller in case A where the distance t is shorter than during focusing, but becomes larger in case B where the distance t is longer. Therefore, focusing information can be detected by detecting the spot position and spot diameter.

On the other hand, tracking information detection is carried out by utilizing the mutual interference of reflected light between parts of the optical disc 10 with and without bits. That is, when the light spot deviates from the center, the light is reflected by nearly 100 pixels, whereas when the light spot irradiates a part of the center, the reflectance decreases and the light amount changes by one reflected light. Therefore, tracking information can be detected by monitoring the change in the amount of light and detecting the minimum amount of light. If a tiger or king error occurs, BS
Beam scanning is performed by changing the current ratio injected into L 13, and the parallel light beam after passing through the lens 14 is moved in parallel, and the diffraction direction of the incident parallel light beam is changed by making it incident on a grating with a different spatial frequency.
The optical spot can be tracked at the top.

Next, a second embodiment shown in FIG. 8 will be described. This second embodiment differs from the first embodiment in that the reflected light from the optical disk 10 is made to enter the waveguide 12 again and then detected. That is, the light reflected from the optical disk 100 is coupled to the waveguide 12 by the coupling prism 17 and re-enters the waveguide 12. The light is then condensed by a condensing lens 18 provided within the waveguide 12, and enters a photodetector 19 installed at the light incidence end of the waveguide 12, where it is detected.

Focusing and tracking information detection in this embodiment are performed as follows. In focusing information detection, as shown in FIG. 9, in the case of -focus A and H, the incident position with respect to the lens 8VC is different after the waveguide 7 is irradiated, and it is detected by the photodetector 19. This will cause a change in the amount of light. Therefore, flashing information is detected from changes in the amount of light on the elephant. On the other hand, the tracking information is detected after the focusing information is detected by utilizing the fact that, as described above, a change in the amount of light occurs due to the interference of reflected light between parts of the optical disc 10 where bits are present and where there are no bits.

Next, a third embodiment of the present invention shown in FIGS. 10 and 11 will be described. This third embodiment differs from the second embodiment by combining a doubling prism 12 with an optical path changing prism 20, so that the optical path of the reflected light from the optical disk 10 can be changed as shown in FIG. Convert
This is because the reflected light is efficiently made to enter the waveguide 12 again. Since the parts other than this point plate are the same as those in the previous embodiment, the explanation will be omitted.

It goes without saying that the present invention is not limited to the embodiments described above, and that various modifications can be made without departing from the spirit of the present invention.

〔Effect of the invention〕

According to the present invention, since a semiconductor laser having the function of deflecting the emitted light is used as a light source, a collimating lens and a grating are installed in a waveguide on a substrate formed of a single material. There is no need to provide intersecting electrodes for generating surface acoustic waves for diffraction. Furthermore, a semiconductor laser as a light source and a photodetector can be integrated with the waveguide, and a waveguide type optical pickup head that can perform H-tracking can be provided by deflection scanning of the semiconductor laser.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the overall configuration of the first embodiment of the present invention, FIG. 2 is a perspective view showing the BSL of the same embodiment, and FIG.
a) (b) to Figures 5 (,) (b) are diagrams showing the characteristics of the same BSL, Figure 6 (,) (b) are diagrams showing the action of the same BSL, and Figure 7 (a) (b) ) is a diagram showing the focusing and tracking information detection means of the same embodiment, FIGS. 8 and 9 are diagrams showing the second embodiment of the present invention, and FIGS. 10 and 11 are diagrams showing the third embodiment of the present invention. It is a figure showing an example. FIG. 12 is a perspective view showing a conventional example. 10... Optical disk, 11... Substrate, J2... Waveguide, J,? BSL (beam scanning laser), 14... Collimating lens, 15... Grating, 16... Photodetector, 17... Coupling prism, 18... Condensing lens, 19... - Photodetector, 20... optical path conversion prism. Applicant's representative Patent attorney Atsushi Tsuboi Figure 1 Figure 2 (a) (b) Figure 3 (a) (b) Fourth cause (a) (b) Figure 5] Figure 6 Exit 1! Figure 7■ 8th F! ! J 9th r! 1 Figure 10 Figure 11 Country Figure 12 1vI4n, 90.91' 18c11, Indication of the case Japanese Patent Application No. 175510/1982 2, Name of the invention Waveguide type optical female assode head 3, Person making the amendment ・Relationship with the case Patent applicant name (037) Olympus Optical [+AV, Residents Association 714
, agent

Claims (4)

[Claims] (1) A waveguide provided to guide light incident from a light input end to a light output end, a semiconductor laser installed at the light input end of the waveguide and having an emitted light deflection function, and this semiconductor laser A collimating lens is provided in the waveguide so as to collimate the light emitted from the waveguide, and the collimating lens diffracts the collimated light to make the emitted light into a spot from the light output end of the waveguide. A grating including diffraction gratings with different spatial frequencies provided in the waveguide so as to emit light toward the optical disk, and a detection means for receiving reflected light from the optical disk and detecting focus information and tracking information. A waveguide type optical pickup head characterized by the following. (2) The waveguide type optical pickup head according to claim 1, wherein the semiconductor laser is installed at the focal position of the collimating lens. (3) The light guide according to claim 1, wherein the detection means is equipped with a photodetector in which photodiodes are arranged in a two-dimensional matrix near the light output end of the waveguide. Wave-type optical pickup head. (4) The detection means re-enters the reflected light into the waveguide via the coupling prism and performs a predetermined process, and then
2. The waveguide type optical pickup head according to claim 1, further comprising means for detecting with a photodetector.