JP3284591B2 - Optical disc recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording method.

[0002]

2. Description of the Related Art Usually, in recording and reproducing of CD-R,
780 which is the easiest to use due to the spectral sensitivity characteristics of the disk medium
nm-band semiconductor lasers are used as light sources. FIG.
FIG. 4 and FIG. 4 show spectral sensitivity characteristics of two types of optical disks A and B satisfying the CD-R standard. The vertical axis indicates the proportion of the light beam emitted from the laser light source that is reflected by the optical disk and returns, that is, the reflectance. Here, the reflectivity is mainly a ratio of a component transmitted through the optical disk and reflected on the upper surface and returned, and substantially corresponds to the transmittance. Light in the 800 nm band or more passes through the optical disk medium without being absorbed, and thus cannot be used as a recording light source. For recording and reproduction, appropriate absorption and reflection are necessary. In this sense, conventionally, the reflectance is sufficiently large and the absorption is about 10 to 20%.
An 80 nm band laser light source is used for recording and reproduction.

On the other hand, as the functional requirements for optical discs have increased, there has been a demand for light sources, for example, to have higher recording power. This is because higher output power is required for high-speed recording, and the function level of the optical recording / reproducing apparatus is considered to depend on the output level of the laser light source.

[0004]

However, increasing the recording output power of the laser light source for high-speed recording on an optical disk or the like causes an increase in the size of the optical pickup and an increase in the driving current. The present invention has been made in view of such a point, and enables recording at a power of, for example, less than the conventional reproducing power without increasing the size of the optical pickup or increasing the driving current, and further achieves higher-density recording than the conventional. It is an object of the present invention to provide a recording method of an optical disk which is enabled.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a recording method for a CD-R type optical disk, which has a shorter wavelength than a reproducing laser beam and an absorptivity of 50% or more on the optical disk. Recording is performed at a lower power than the output power of the reproduction laser light using the reproduction laser light.

[0006]

According to the present invention, recording is performed by using a laser light source in a short wavelength region having a very high absorptivity on an optical disc as compared with the conventional one, in other words, a short wavelength region having a very small reflectance. It becomes possible to make the laser light source power at the time of recording smaller than the power at the time of conventional reproduction. As a result, the size of the optical pickup can be reduced and the current consumption of the drive circuit can be reduced. Further, by shortening the recording wavelength, high-density recording can be performed as compared with the related art.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an optical system of an optical disk recording / reproducing apparatus according to one embodiment of the present invention. The optical disc 1 is a CD-R type disc. An optical pickup unit for recording and reproducing the optical disk 1 includes a semiconductor laser 2, a collimator lens 3, a half mirror 4, an objective lens 5, a condenser lens 6, and a photodiode 7. Although the optical system of the actual device is more complicated to perform tracking control and the like, only the basic elements necessary for recording and reproduction are shown here.

The light beam from the semiconductor laser 2 is converted into parallel light by a collimator lens 3, and is applied to the lower surface of the optical disk 1 via a half mirror 4 and an objective lens 5. The reflected light beam from the optical disc 1 passes through the objective lens 5, is reflected by the half mirror 4,
Is collected on the photodiode 7.

The semiconductor laser 2 is a short-wavelength laser whose absorptance in the optical disk 1 is 50% or more. Specifically, a semiconductor laser having a wavelength of 750 nm or less is used for an optical disk having a spectral sensitivity as shown in FIG. 3 or FIG. The output power of the semiconductor laser 2 at the time of recording is set to be equal to or less than the power at the time of reproduction from a conventional CD-R disc. That is, conventionally, the power during recording is about 6 to 8 mW, and the power during reproduction is about 5 mW. On the other hand, in this embodiment, a short-wavelength laser in the 680 nm band is used as the semiconductor laser 2, and the recording power is set to 1.5 mW.
This is a result of considering a loss of about 50% which is equal to or less than the conventional reproducing power. Also, the power during playback is
Since it is necessary to prevent data destruction, it is necessary to set the power to a value lower than the recording enable power, and it is set to about 0.2 mW.

According to this embodiment, the power of the laser light source at the time of recording can be made smaller than the power at the time of conventional reproduction, whereby the size of the optical pickup can be reduced and the current consumption of the drive circuit can be reduced. . Further, by shortening the recording wavelength, high-density recording can be performed as compared with the related art. By the way, in this embodiment, if the same wavelength is used during reproduction, the power during reproduction becomes extremely small due to the short wavelength and low power of the recording light source, and stable laser oscillation may not be obtained.

FIG. 2 shows a schematic configuration of an optical system of an optical disk recording / reproducing apparatus according to another embodiment which solves this problem. 1 are assigned the same reference numerals as in FIG. In this embodiment, the recording light source and the reproduction light source are separated. That is, the recording semiconductor laser 2
a, reproduction semiconductor laser 2 separately from collimator lens 3a
b, a collimator lens 3b is prepared, these are switched and driven to irradiate the optical disk 1 via the half mirror 8. The recording semiconductor laser 2a is a semiconductor laser having a wavelength of 750 nm or less, for example, 680 nm, as in the previous embodiment. The recording power is set to, for example, 1.5 mW as in the previous embodiment. On the other hand, the reproducing semiconductor laser 2b is, for example, a conventional 780 nm semiconductor laser. The power during reproduction is about 5 mW.

According to this embodiment, the effect of shortening the wavelength of the recording laser light source can be obtained while securing the stability of the laser light source during reproduction.

[0013]

As described above, according to the present invention,
Shortening the wavelength of the recording laser light source enables recording at a power lower than the conventional reproducing power without increasing the size of the optical pickup or increasing the drive current, and recording on optical discs that enables higher density recording than before. A method can be provided.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration of an optical system of an optical disk recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 shows a schematic configuration of an optical system of an optical disk recording / reproducing apparatus according to another embodiment of the present invention.

FIG. 3 is a diagram showing a reflectance spectrum of a CD-R type optical disc A;

FIG. 4 is a diagram showing a reflectance spectrum of a CD-R type optical disc B;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Semiconductor laser, 3 ... Collimator lens, 4 ... Half mirror, 5 ... Objective lens, 6 ... Condensing lens, 7 ... Photodiode, 2a ... Recording semiconductor laser, 2b ... Reproduction semiconductor laser, 3a , 3b ... collimator lens.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-199630 (JP, A) JP-A-2-278519 (JP, A) JP-A-2-29931 (JP, A) JP-A-3-297 292630 (JP, A) JP-A-61-40194 (JP, A)

Claims (1)

(57) [Claims] 1. A recording method for a CD-R type optical disc, wherein the wavelength is shorter than a reproducing laser beam and the optical disc absorbs light.
A recording method for an optical disk, wherein recording is performed with a power lower than the output power of the reproduction laser light using a recording laser light having a yield of 50% or more.