JPH0461637A - Recorder for optical disk - Google Patents

Abstract

PURPOSE:To execute write with high density by light of a small output and short wavelength by raising a temperature of the information recording surface to immediately before a recording temperature by condensing irradiation of second light, heating the information recording surface to the recording temperature or above by condensing irradiation of first light. CONSTITUTION:Irradiation optical systems 2-6 emit first light and second light whose wavelength is longer than that of first light. Condensing optical systems 7, 12 condense first light and second light as a spot of the prescribed diameter and as a spot being larger than the prescribed diameter, respectively on the information recording surface of an optical disk D. Subsequently, write processing systems 11-14 execute write of information to the information recording surface irradiated with first light. In such a way, a temperature of the information recording surface is raised to immediately before a recording temperature by condensing irradiation of second light, the information recording surface is heated to the recording temperature or above by condensing irradiation of first light, and write of information to the information recording surface is executed. Accordingly, write of high density can be executed by light of a small output and short wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a recording device for optical disks (including magneto-optical disks and phase change disks).

BACKGROUND ART Writing on an erasable magneto-optical disk usually uses a laser beam with a wavelength of about 830 nm as the writing light, and focuses the writing light on a spot of about 1 μm to write on the film surface (information recording surface) of the optical disk. The film surface is heated by irradiation,
Recording bits are formed by reversing the direction of magnetization using a weak external magnetic field.

By the way, in order to increase the density of recorded information in optical discs, it is necessary to make recording bits smaller. For this purpose, it is necessary to use a laser beam with a shorter wavelength as the writing light.

For example, if the wavelength of the writing light is 400 nm, the bit length and bit width of the recording bits will each be reduced to about 1/2, making it possible to quadruple the recording density.

However, at present, the shorter the wavelength, the more difficult it is to increase the output of a laser light source, and it is difficult to realize a laser light source with a short wavelength and high output.

Summary of the Invention [Object of the Invention] Therefore, an object of the present invention is to provide an optical disc recording device that enables high-density writing using light with a small output and a shorter wavelength.

[Structure of the Invention] An optical disk recording device according to the present invention includes an irradiation optical system that emits first light and a second light having a longer wavelength than the first light, and an irradiation optical system that emits the first light and the second light having a longer wavelength than the first light. a condensing optical system that condenses the first light as a spot with a predetermined diameter and the second light as a spot larger than the predetermined diameter; and an information recording surface that is irradiated with the first light. The configuration consists of a writing processing system that writes information to the computer.

[Operation of the Invention] In the optical disc recording device according to the present invention, first light and second light having a longer wavelength are used, and the information recording surface is recorded by condensed irradiation of the second light. The temperature is raised to just below the temperature, and the information recording surface is heated to the recording temperature or higher by condensed irradiation of the first light, and information is written on the information recording surface.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 1, primary light (light source light) having a wavelength of 830 nm, for example, emitted from a light source 1 such as a semiconductor laser is condensed by a condenser lens 2 and enters a fiber type optical wavelength conversion element 3. This optical wavelength conversion element 3 is a fiber type SHG (Second HG) using a second-order nonlinear optical effect.
d Harmonies Generator (second harmonic generation element), which employs Cerenkov radiation type phase matching. According to this method, it is possible to generate a second harmonic (SR) whose phase is almost automatically matched.

The primary light emitted from the core of this fiber type 5HG3 and the SR light (wavelength converted light) whose wavelength has been converted by the fiber type 5HG3 and whose wavelength is half that of the primary light (415 nm).
is, for example, a truncated cone-shaped axicon lens 4 on the same optical axis.
incident on . In the truncated conical axicon lens 4, 1
The secondary light passes through the parallel glass section 4a, and the SR light passes through the conical section 4b.
pass through. When the primary light passes through the parallel glass section 4a, spherical aberration occurs depending on its thickness, and when the SR light passes through the conical section 4b, it is converted into parallel light.

This primary light and the SR destination pass through the beam splitter 5 because the polarization plane is P polarization, and the polarization plane is changed from linear polarization to circular polarization by the λ/4 plate 6 and enters the objective lens 7.

The objective lens 7 has two wavelengths (in this example, 830
415 nm) with slightly different focal lengths are used. Due to the action of this objective lens 7, the wavelength λ2 (λ2-2-830
The primary light with a long n is a short SR light with a wavelength λ1 (λ+-415 nm) as a spot about twice the target bit diameter.
are respectively focused on the information recording surface of the optical disc D as spots with a target bit diameter. An electromagnet 8 that generates a DC magnetic field for writing or erasing information on the information recording surface of the optical disc D is provided on the back side of the optical disc D, and the polarity of the electromagnet 8 is determined by a magnetic field modulation circuit 9 according to the recording signal. It is designed to be reversed.

As the power of the primary light (wavelength: 830 nm) emitted from the light source 1, different power values are set by the power control circuit 10 during recording and during reproduction. For example, the write power during recording is 9mW.

The read power during reproduction is set to 1 to 1.5 mW.

During reproduction, the reflected light based on the SR light from the optical disc D passes through the objective lens 7, and the plane of polarization is changed from circularly polarized light to linearly polarized light by the λ/4 plate 6, and then enters the beam splitter 5. Here, the incident light of the beam splitter 5 passes through the λ/4 plate 6 twice on the outbound and return passes, so that the polarization plane becomes S-polarized light, so it is reflected by the beam splitter 5 and further reflected by the dichroic mirror 11. be done. This SR light is passed through a condensing lens 12 to a photodetector 13.
The light is focused on the light receiving surface. The output of the photodetector 13 is directly converted into a read RF signal and is supplied to the information reproducing processing circuit 14, where signal processing such as demodulation processing is performed, and the signal is derived as a reproduced output.

Examples of optical discs on which information is recorded/reproduced by such a recording/reproducing device include -
A transparent substrate 31 made of PMMA or the like serves as a read-only recording layer on which a bit string 32 corresponding to predetermined information is preformed on the main surface 31a, and a transparent substrate 31 made of a dielectric multilayer film of Ge, MgF2-ZnS, etc. Tb-Fe-C and a selective reflection film 33 that reflects one of the irradiated lights having different wavelengths and transmits the other light irradiated from the other principal surface 31b side.

For example, an optical disc may be used that has a structure in which a recordable layer 34 and a protective layer 35 are stacked in this order, and these layers are laminated in order. The possible layer 34 is the target of recording/reproduction.

In the case of a Curie point recording medium in a magneto-optical recording medium, as shown in FIG. 4, the temperature of the medium is heated to a temperature of 200° C. or higher at which the coercive force Hc disappears. Then, a recording bit is formed by reversing the direction of magnetization using a weak external magnetic field. Generally, the medium temperature near room temperature is heated to over 200°C at once, so in the case of a spot diameter of about 1 μm,
Writing light with a power of about 10 mW is required (in the case of high-density recording, the spot diameter becomes even smaller).

Therefore, in the above-mentioned recording and reproducing apparatus, the temperature is raised to about 150 degrees Celsius with the long primary light spot with wavelength λ2, and the remaining 50 to 80
By heating at °C, high-density writing can be performed with a short wavelength and low output.

In the above embodiments, a case where the present invention is applied to a recording/reproducing device has been described, but the present invention can also be applied to a recording device itself.

As described in detail, the optical disc recording device according to the present invention uses a first light and a second light having a longer wavelength, and collects information by condensing the second light. Since the configuration is such that the temperature of the recording surface is raised to just before the recording temperature, and the information recording surface is heated to the recording temperature or higher by condensed irradiation of the first light, information is written on the information recording surface.
High-density writing is possible with low-output, shorter-wavelength light.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a convergence state of short SH light with a wavelength λ1 and long primary light with a wavelength λ2, and FIG. 3 is a diagram showing the configuration of an optical disc. FIG. 4, which is a sectional view showing an example, is a characteristic diagram showing the relationship between medium temperature and coercive force in a magneto-optical disk. Explanation of symbols of main parts 3... Fiber type 5HG 4... Frustoconical axicon lens 5...
・Beam splitter 7...Objective lens 11...Dichroic mirror 13...
・Photodetector

Claims (2)

[Claims] (1) an irradiation optical system that emits a first light and a second light having a longer wavelength than the first light; and a spot having a predetermined diameter on the information recording surface of an optical disc, a condensing optical system that condenses the second light into a spot larger than the predetermined diameter; and a writing processing system that writes information on the information recording surface irradiated with the first light. An optical disc recording device comprising: (2) The irradiation optical system includes a fiber-type optical wavelength conversion element that converts the wavelength of the light source light and emits it as parallel secondary light along the same optical axis as the light source light, and converts the secondary light into 2. The optical disc recording apparatus according to claim 1, wherein the light source light is used as the second light as the first light.