Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-05-18
2001-08-07
Young, W. R. (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S112090, C369S112200, C369S120000, C369S122000
Reexamination Certificate
active
06272097
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical head and an apparatus for recording and reproducing optical information through the use of the optical head.
As a system of reducing an optical head mounted in an apparatus for recording and reproducing optical information on and from an optical medium like an optical disk, several prior arts have been made public as disclosed in JP-A-62-58432, JP-A-64-46242, JP-A-4-255923, and JP-A-6-251410. The optical head disclosed in the publication of JP-A-62-58432 is arranged so that photo detector elements and a semiconductor laser having a Fabri-Perot horizontal resonator as a light source are integrated on the same substrate. On the other hand, the optical head disclosed in JP-A-64-46242, JP-A-4-255923, or JP-A-6-251410 employs the so-called surface emitting laser as its light source.
For the optical head disclosed in JP-A-62-58432, in order to apply the optical head to the apparatus for recording and reproducing optical information such as an optical disk drive, it is necessary to curve an optical axis of a light flux fired from a semiconductor laser by 90 degrees. The publication of JP-A-62-58432 has disclosed a method of forming a reflective mirror through the use of an etching technique, for example. However, this method burdens the manufacturing process with great difficulty. Further, since the semiconductor laser needs a different density of impurities to be implanted from the photo detector elements, if both of the semiconductor laser and the photo detector elements are formed by the same process, disadvantageously, it is difficult to obtain the sufficient characteristics of both.
If the surface emitting laser is used as a light source like the optical head disclosed in JP-A-64-46242, JP-A-4-255923, or JP-A-6-251410, no reflective mirror is required to be formed unlike the optical head disclosed in JP-A-62-58432. Hence, the use of the surface emitting laser as the light source makes the manufacturing process a bit simpler. However, at this time, the difficulty of the surface emitting laser in enhancing an output power and fixing a direction of polarization of outgoing light makes it difficult to apply such an optical laser to apply to an apparatus for recording and reproducing recordable optical information.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical head which includes a light source and photo detector elements integrated on the same substrate by a simple manufacturing process and may be applied to an apparatus for recording and reproducing recordable optical information, and an apparatus for recording and reproducing optical information through the use of the optical head.
According to the present invention, a light source is a semiconductor laser element having a vertical resonator composed by forming a light waveguide layer of column semiconductor crystal on a monocrystalline transparent substrate through the use of a selective growth technique, forming an active layer on each side of the light waveguide layer, and then forming a Bragg reflector formed of a super lattice structure high-reflection film before and after an emitting surface of the active layer so that light outgoes perpendicularly to the monocrystalline substrate. By devising the pattern of the insulating layer mask used in the selective growth technique, the photo detector element may be formed on the substrate on which the semiconductor laser beam source is formed and closer to the light source.
In the optical head according to the present invention, a light beam separating element is formed by laminating a first transparent layer on the opposed plane of the monocrystalline transparent substrate to the semiconductor laser element by means of the plasma CVD technique or the sputtering technique and forming a diffraction grating on the lower surface of the first transparent layer through the effect of a photomask exposure process and an ion exchange process. Next, a second transparent layer is laminated on the lower surface of the first transparent layer by means of the plasma CVD technique or the sputtering technique and an element of generating a phase difference corresponding to a quarter-wave plate is formed on the lower surface of the second transparent layer. In succession, a third transparent layer is laminated under the second transparent layer by means of the plasma CVD technique or the sputtering technique. Then, a light condensing element is composed by forming on the lower surface of the third transparent layer a grating lens by means of a photomask exposure process, or a index-distributed type lens or a convex lens by means of an ion exchange process or the like. Moreover, a fourth transparent layer is laminated on the lower surface of the third transparent layer by means of the plasma CVD technique or the sputtering technique. On the lower surface of the fourth transparent layer is formed a slide-resisting protective layer such as a ceramic material by means of the sputtering technique. Next, the fourth transparent layer and the slide-resisting protective layer are located close to each other as opposed to an information recording medium.
The light applied from the semiconductor laser beam source passes through the first transparent layer, the light beam separating element, the second transparent layer, the element of generating a phase difference, and the third transparent layer. Then, through the use of the light focusing element used in the fourth transparent layer, a focused spot is formed closer to the plane opposed to the information recording medium. The light reflected on the information recording medium passes through the fourth transparent layer, the light focusing element, the third transparent layer, the element of generating a phase difference, and the second transparent layer. The light passed through the second transparent layer is separated into plural fluxes of light through the effect of the light beam separating element and then the separated fluxes of light are guided to the photo detector element integrated and formed closer to the semiconductor laser beam source.
According to the present invention, like the semiconductor laser having a Fabri-Perot horizontal resonator, the semiconductor laser used as a light source has a structure of applying a flux of light from an end of the active layer. It is more advantageous in a viewpoint of enhancing an output power and controlling a direction of light of polarization than the so-called surface emitting laser. Hence, the resulting optical head may be applied to the apparatus for recording and reproducing recordable optical information. The use of the semiconductor manufacturing process such as a photomask exposure process makes it possible to form the light source, the photo detector element and the function elements except them through the use of one process, thereby reducing the size and the cost of the resulting optical head.
REFERENCES:
patent: 4993035 (1991-02-01), Laikhtman
patent: 5481386 (1996-01-01), Shimano et al.
patent: 5715226 (1998-02-01), Shimano et al.
patent: 5783844 (1998-07-01), Kobayashi et al.
patent: 5995474 (1999-11-01), Shimano et al.
patent: 62-58432 (1987-03-01), None
patent: 64-46242 (1989-02-01), None
patent: 4-255923 (1992-09-01), None
patent: 6-251410 (1994-09-01), None
patent: WO96/27880 (1998-04-01), None
Japanese Journal of Applied Physics, vol. 36, 1997, pp. 589-590.
The 15th Annual Conference on Magnetics in Japan, Paper 31pB-5 (Technical Digest), p. 310, 1991.
Proceedings of “Optical Memory Symposium '88”, pp. 35-36.
IEICE Technical Study Report of Electronics, Information and Communication Engineers of Japan, 1991, Report No. MR 91-72-79, Feb. 27, 1992.
Nakamura Shigeru
Nakao Takeshi
Shimano Takeshi
Tanaka Toshiaki
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
Young W. R.
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