JPH03273545A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To read even a signal of a minute inversion magnetic domain in the way of reproducing with a semiconductor laser of a shorter wavelength than recording and to contrive high densification by constituting a light source out of two kinds of semiconductor lasers having different wavelengths. CONSTITUTION:At the time of recording, provided the wavelength of the semi conductor laser 1 is longer than the wavelength of the semiconductor laser 2, laser light emitted from the long wavelength semiconductor laser 1 is formed into a light spot on a recording medium 12 via a collimator lens 3, and the temp. of the the recording medium in the light spot part is raised. A signal to be recorded is modulated by a magnetic field of a magnetic head positioned opposite to an optical head via the recording medium. At the time of reproduc ing the information, the recording medium 12 is irradiated with laser light from the short wavelength semiconductor laser 2. Thus, since the recording medium can be irradiated with large laser power by using the long wavelength laser at the time of recording, the transfer speed of information is raised, and since the short wavelength laser is used at the time of reproducing, the light spot diameter of the irradiating laser light is so diminished that even a signal in a minute inversion magnetic domain can also be read out satisfactorily.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a magneto-optical recording and reproducing device using an overridable magnetic field modulation system. Although magneto-optical disks are expected to be used in many fields as
However, in optical modulation recording, the upper limit of the frequency of the recorded signal is limited by the wavelength of the semiconductor laser, and short-wavelength signals are limited by the wavelength of the semiconductor laser. In view of the above-mentioned problems, the present invention had the drawback that it was difficult to increase the density because the area of the recording domain was small compared to the effective area of the laser beam spot during reproduction, and the signal level decreased. The present invention provides a recording/reproducing device capable of high-density recording.

Means for Solving the Problems In order to solve the above problems, the magneto-optical recording/reproducing apparatus of the present invention employs a magnetic field modulation method in which the frequency of the recording signal is not limited to the wavelength of the laser, in order to modulate the recording signal into the applied magnetic field. The light source is composed of two types of semiconductor lasers with different wavelengths, with the short wavelength semiconductor laser used for reproduction and the long wavelength high power semiconductor laser used for recording.

Effect of the present invention With the above-described configuration, the frequency of the recorded signal does not depend on the wavelength of the laser even during recording, and reproduction is performed using a short wavelength semiconductor laser. Although signals can be sufficiently read out and high density is possible, the embodiments of the present invention will be described below without reference to the drawings. Even in the configuration diagram, in Fig. 1, 1 is a semiconductor laser a,
2 is semiconductor laser b, 3 is collinouching lens X
4 is a circular correction prism, 5 is a polarizer, 6 is a beam splitter, 17 is an objective lens, and 8 is a beam splitter.
19 is an analyzer, 10 is a condensing lens, 11 is a light detection a
12 is a recording medium & 13 is a magnetic head a The wavelength of semiconductor laser a is longer than the wavelength of semiconductor laser b. When recording, the laser beam emitted from the long-wavelength semiconductor laser a passes through a collimating lens 3 and a circular correction prism 4. It becomes a parallel laser beam with a circular cross section, and is linearly polarized by a polarizer 5. A beam splitter Although it passes through −6, the laser beam enters objective lens 7.
A light spot is formed on the recording medium 12, and the temperature of the recording medium at the light spot portion is increased. Even though the signal to be recorded is modulated by the magnetic field of the magnetic head located opposite to the optical head across the recording medium, when reproducing information, a short wavelength semiconductor laser b is sent to the recording medium 12 along the same optical path as for recording.
Irradiate on top. The laser light reflected here returns through the objective lens 7 and is separated from the incident light by the beam splitter 6.
The separated reflected laser beam 1 is further separated by a beam splitter 8 into a reproduction laser beam and a servo laser beam. The reproduction laser beam (passes through an analyzer 9, is focused by a condensing lens 10, is photoelectrically converted by a photodetector 11, and a signal is detected.

FIG. 2 shows a comparison of the recording bit length and dependence of the reproduced signal level in this embodiment and the conventional example.

As is clear from FIG. 2, there is no significant drop in the reproduced signal level.According to this embodiment, a large laser power is irradiated onto the recording medium by using a long wavelength laser during recording. It is possible to increase the rotational speed of the disc, increasing the speed of information transfer. Furthermore, by using a short-wavelength laser during reproduction, the diameter of the spot of the irradiated laser beam becomes smaller, making it possible to read out signals of minutely inverted magnetic domains. Semiconductor t/-
By using a semiconductor laser with a shorter wavelength than that used during recording, it is possible to read out signals from minutely inverted magnetic domains, achieving higher density.Furthermore, since it uses a magnetic field modulation method, a semiconductor laser with a long wavelength and high power is used during recording. Since a laser can be used, it is also possible to increase the number of rotations of the disk, thereby realizing an excellent magneto-optical recording and reproducing device that can achieve the effect of increasing the information transfer speed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an optical head in an embodiment of the present invention. FIG. 2 is a diagram showing the dependence of the reproduced signal level on recording bit length in an embodiment of the present invention. 1...Semiconductor laser a, 2...Semiconductor laser b, 3...Corinouching lens X4--round correction lens X5...Polarizer, 6...Beam splitter-
7...Objective lens X 8...Beam splitter-9...
Analyzer, 10... Condensing lens, 11... Photodetector 12... Recording medium image 13... Magnetic head.

Claims (2)

[Claims] (1) A magneto-optical recording and reproducing device characterized in that, in magneto-optical recording using a magnetic field modulation method, the wavelength of a light source such as a semiconductor laser on the medium surface is shorter during reproduction than during recording. (2) The magneto-optical recording and reproducing apparatus according to claim 1, wherein the light source is composed of two types of semiconductor lasers having different wavelengths.