JPH0194540A - Optical pickup - Google Patents

Abstract

PURPOSE:To read and remote-control a signal and to miniaturize the head part of the optical pickup and to reduce in weight by connecting a light source/ signal detecting part and a disk head part with an optical fiber, and separating the optical head and making it independent with the optical fiber. CONSTITUTION:A light source/signal detecting part 1 to possess a detecting system to detect a laser diode 4a to emit laser light based on an input signal 12 and the polarized wave rotation of reflected light, and a disk head part 3 to possess a disk 9 and an optical head 8 are connected with optical fibers 7a and 7b. Further, the optical head 8 of the disk head part 3 is separated and made independent by an optical fiber 14. Thus, the signal from a remote place can be read out, and the head part can be made smaller and lighter.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical pickup using an optical fiber.

[Prior art] Conventional optical pickups use bulk components such as lenses, prisms, and beam splitters for the optical system that focuses light from a light source onto a disk that stores signals and measures the reflected light. . The optical head unit was integrated with a light source, a light receiver, and an optical system for guiding waves to the disk surface, condensing light, and detecting reflected light.

[Problems to be Solved by the Invention] However, with the above-mentioned conventional optical pickup, information cannot essentially be read from or written to an optical disk from a remote location. Furthermore, alignment of optical parts such as lenses, beam splitters, beam splitters, etc. is difficult, which not only makes assembly work difficult and increases costs, but also poses problems in the stability of the optical axis against vibrations and the like. Furthermore, when moving the head, it is necessary to move not only the head but the entire optical system at once, which increases access time.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, and to provide a low-cost optical pickup that allows remote control of signal readout, facilitates alignment of the optical system, and allows the head to be made smaller and lighter. It's about doing.

[Means for Solving the Problems] The present invention provides an optical pickup that irradiates light from a laser diode onto a disk on which a signal is recorded by an optical head and measures the reflected light. A light source/signal that has a detection system that detects wave rotation, a detection unit, and a disk head that has a disk and an optical head are connected by an optical fiber, and the optical head of the disk head is separated and independent by an optical fiber. has been done.

[Function] Since the light source/signal detection section and the disk head section are connected by an optical fiber, signals can be read from a remote location. Furthermore, since the optical head facing the disk in the disk head section is separated and independent by an optical fiber, it is small and lightweight and can be easily driven.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, 4a is a laser diode, and the laser diode 4a emits a laser beam based on an input signal 12. The emitted light from the laser diode 4a is transmitted through the optical connector 6a and the polarization maintaining optical fiber (hereinafter referred to as S) of the optical cable 2.
(abbreviated as PF) 7a and an optical connector 6C to the disk head section 3. As shown in detail in FIG. 2, the light from 5PF7a is transmitted to
The light is coupled to the PF 7'a, converted into parallel light by the lens 13d, reflected by the beam splitter 16a, and sent to the coupling/branching optical system 15. The coupling/branching optical system 15 has a configuration shown in FIG. 3, and the light from the beam splitter 16a passes through the beam splitter 18 of the coupling/branching optical system 15, is focused by the lens 13f, and is polarized at the center of the multi-core optical fiber 14. It is coupled to a wavefront preserving single mode optical fiber core 14a. Note that 14b is its cladding. The light propagated through the multi-core optical fiber 14 and emitted is focused onto the disk 9 by the optical head 8 .

A part of the reflected light from the disk 9 (rotation signal of the plane of polarization received by the light by the magnetic material coated on the surface of the disk 9 as a recording signal) is coupled to the core 14a of the multi-core optical fiber '14 by the optical head 8. The emitted light is transmitted to the lens 13r1 of the coupling/branching optical system 15 and the beam splitter 18.
is guided to the beam splitter 16b via the beam splitter 16b. The reflected light from the beam splitter 16b is focused by the lens 13e,
5PF7'b, is coupled to 5PF7b of the optical cable 2 via the optical connector 6d, and further guided to the photodetection system 22 via the optical connector 6b. The photodetection system 22 has a polarizing beam splitter and a photodiode, and information on the disk 9 is read from the output signal 11 thereof.

On the other hand, another part (or scattered light) of the reflected light from the disk 9
is guided by the optical head 8 to the multimode optical fiber cores 14c to 14f of the multicore optical fiber 14. Note that 14g is a support. The light emitted from the cores 140 to 14f is sent to the mirrors 19a and 19b of the coupling/branching optical system 15.
etc., and are guided and detected via lenses 13 (1, 13h, etc.) and optical fibers 24d to 24(), respectively, to photodiodes 5d to 5g of the optical detection/servo control system 10. Multi-core optical fiber 14 A multimode optical fiber core 14 arranged symmetrically as shown in FIG.
The relative positional relationship between the optical head 8 and the disk 9 can be detected by detecting the change in optical output from 0 to 14f.

Tracking control and focusing control can be performed by driving the optical head 8 by the electronic controller 20 based on this detection information.

In this embodiment, since only the disk head section 3 has an optical pickup function, a light source (laser diode 7 and 4) is used.
b) It has a built-in photodetection system (polarizing beam splitter 23 and photodiodes 5b and 5c).

In addition, in the above embodiment, the multi-core optical fiber 14
The multi-mode optical fiber cores 14c to 14f are set to only two (for example, core 14c and core 14e), so that only the focusing signal is detected, and the tracking signal is transmitted near the disk 9 as shown in FIG. Two lenses 13i and 13j are installed, and these are connected to a photodiode 5 using multimode optical fibers 21a and 21b.
f, 5 (J) for detection.

Furthermore, instead of the quarter-wave plate 6, a half-wave plate may be installed between the coupling/branching optical system 15 and the beam splitter 16b. Further, in the above embodiment, reading of signals has been described, but recording (writing) of signals can be performed in the same manner. In this case, it is also possible to provide two laser diodes for reading and recording, or to modulate the output of one laser diode in a pulsed manner and use it in a time-division manner.

[Effect of the invention] The present invention has the following effects.

(1) Since the light source/signal detection section and the disk head section are connected with an optical fiber, signals can be read from a remote location without having to transport the disk as in the past.

(The optical head that drives the disk head section is separated and independent using optical fibers to reduce size and weight. Access time can be shortened, good tracking control and focusing control can be performed, and energy consumption can be reduced. can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of an optical pickup according to the present invention, FIG. 2 is a detailed configuration diagram of the disk head section of FIG. 1, and FIG. 3 is a configuration of the coupling/branching optical system of FIG. 2. 4 are cross-sectional views of the multi-core optical fiber shown in FIGS. 1 to 3, and FIG. 5 is a configuration diagram showing another embodiment of the present invention. In the figure, 1 is a light source/signal detection section, 2 is an optical cable, 3 is a disk head section, 4 is a laser diode, 5 is a photodiode, 6 is an optical connector, 7 is a polarization maintaining optical fiber, 8 is an optical head, 9 is a disk, 10 is a photodetection/servo control system, 11 is an output signal, 12 is an input signal, 13 is a lens, 14 is a multi-core optical fiber, 15 is a coupling/branching optical system, 16 is a beam splitter, 17 is a quarter wavelength board,
18 is a beam splitter, 19 is a mirror, 20 is a servo drive electronic circuit, 21 is a multimode optical fiber, 22 is a photodetection system, ? 3 (polarizing beam splitter, 24 is an optical fiber. Patent applicant: Hitachi Cable, Ltd. Hitachi, Ltd. Representative Patent Attorney: Nobuo Kinutani Figure 1 Figure 2

Claims (1)

[Claims] In an optical pickup that irradiates light from a laser diode onto a disk on which signals are recorded using an optical head and measures the reflected light, a light source/signal detection unit that includes a laser diode and a detection system that detects polarization rotation of the reflected light. and a disk head section having a disk and an optical head are connected by an optical fiber, and the optical head of the disk head section is separated and independent by an optical fiber.