JP2726524B2 - Optical disk recording / reproducing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording / reproducing method, and more particularly, to an optical disk recording / reproducing method for recording / reproducing information with a laser beam.

[Conventional technology]

An optical disc for recording and reproducing information by irradiating a focused laser beam is expected as a large-capacity file.

Generally, an optical disk is normally rotated at a constant angular velocity to perform recording and reproduction. For this reason, since the linear velocities are different between the inner circumference side and the outer circumference side of the disk, when recording the signal of the same frequency, the interval between the recording marks in the track direction (circumferential direction) is different, and the density becomes dense on the inner circumference side. It becomes sparse on the outer peripheral side.

FIG. 3 is a perspective view for explaining an example of the related art, and FIG. 4 is a top view showing the shape of the light beam spot shown in FIG.

In the optical disk recording / reproducing method shown in FIG. 3, the optical disk 1 has a center hole 2 for rotating the optical disk in the center, and a track guide 3 is formed substantially concentrically in the disk surface.

The track guide 3 and the normal groove used, both inner and outer circumferences, the track guide pitch P ₀ is in the normal 1.6 [mu] m. A focused laser beam is usually used as a light beam for recording and reproducing data on and from the optical disc 1, and a spot A of the light beam has a circular shape as shown in FIG.

[Problems to be solved by the invention]

However, the above-described conventional optical disk recording / reproducing method has a drawback that there is a limit in improving the recording density because the track guide pitch is the same on the outer peripheral side and the inner peripheral side.

[Means for solving the problem]

In the optical disk recording / reproducing method of the present invention, the track guide pitch on the outer peripheral side of the optical disk having the track guide is made smaller than the track guide pitch on the inner peripheral side, and the shape of the light beam spot for recording / reproducing is changed in the radial direction on the outer peripheral side. It is configured to perform recording and playback after shortening.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view for explaining one embodiment of the present invention,
2 (a) and 2 (b) are top views showing the shape of the light beam spot shown in FIG.

In the optical disk recording / reproducing method shown in FIG. 1, a center hole 2 used for rotation is provided at the center of the optical disk 1, and a track guide 3 is provided concentrically with the center hole 2 as a center. The track guide pitch P ₁ on the outer circumference is smaller than the track guide pitch P ₀ on the inner circumference of the optical disc 1. Since it is possible to increase only the number of tracks amount to the track guide pitch P ₁ of the outer peripheral portion is narrowed can increase the recording density.

However, as shown in FIGS. 1 and 2 (a), than the same size of the light beam spot and the light beam spot A that covers the track guide pitch P ₀ of the inner circumferential side has been used on the outer peripheral side, The light beam spot A on the inner peripheral side has the same size as the light beam spot A in the conventional example shown in FIG. However, the light beam spot B on the outer peripheral side is formed into an ellipse whose radial direction is short in order to cover only the track guide pitch P1, as shown in FIGS. ₁ and 2b. (This amount, the length in the circumferential direction is longer than when the circular.) Therefore, even by narrowing the track guide pitch P ₁ of the track guide 3 on the outer peripheral side, is insensitive to track the next be able to.

The shape of such a light beam spot can be easily formed by setting the optical components of the optical head.

Next, a specific example of the embodiment shown in FIG. 1 will be described.

On the optical disc 1 having a diameter of 200 mm and a thickness of 1.2 mm, the track guide pitch P ₀ is set on the inner circumference from φ120 mm to φ150 mm.
9375 track guide grooves of 1.6μm are provided.
Track guide pitch P ₁ 1.48μm on the outer circumference up to 180mm
10135 track guide grooves are provided, and a protective layer made of a transparent derivative, a magneto-optical recording layer made of an amorphous alloy of a rare earth transition metal and an iron group transition metal, and a protective layer are sequentially stacked thereon to form an optical disk medium. Produced.

The optical disk 1 was rotated at 2400 rpm, and a semiconductor laser having a wavelength of 830 nm was irradiated through the substrate to record at a recording frequency of 10 MHz. At this time, the recording mark interval at the innermost circumference (φ120 mm) is 1.5 μm.

The optical head is provided separately for the inner peripheral side and the outer peripheral side, and the shape of the light beam spot A on the inner peripheral side is about 1.5.
The light beam spot B on the outer peripheral side is an ellipse of about 1.4 μm (radial direction) × 1.6 mμ (circumferential direction).

The C / N ratio of the recording / reproducing signal was good, crosstalk was not a problem, and the storage capacity was 612 MB.

As a comparative example, in the case where recording and reproduction were performed only with a circular optical head having a light beam spot shape of about 1.5 μmφ using the same medium as in the above-described embodiment, crosstalk became a problem in the region from φ150 mm to φ180 mm, and it was practically used. I didn't.

Since the storage capacity is 588 MB when the track guide pitch is 1.6 μm in the entire region, it has been confirmed that the present invention can realize 612 MB, so that even if the same recording film is used, high density can be achieved.

〔The invention's effect〕

The optical disk recording / reproducing method according to the present invention is characterized in that the track guide pitch on the outer peripheral side of the optical disk is made narrower than the track guide pitch on the inner peripheral side, and the shape of the light beam spot for recording / reproducing is shortened in the radial direction on the outer peripheral side. In addition, there is an effect that the recording density can be increased even when the same recording film is used.

[Brief description of the drawings]

FIG. 1 is a perspective view for explaining one embodiment of the present invention, FIGS. 2 (a) and 2 (b) each show the shape of the light beam spot shown in FIG. 1, and FIG. FIG. 4 is a perspective view for explaining one example, and FIG. 4 is a top view showing the shape of the light beam spot shown in FIG. 1 ...... optical disc, 2 ...... center hole, 3 ...... track guide, P _0, P ₁ ...... track guide pitch, A, B ...... light beam spot.

Claims (1)

(57) [Claims] 1. An optical disk recording / reproducing method for performing recording / reproduction by rotating an optical disk at a constant angular velocity, wherein a track guide pitch on an outer peripheral side of the optical disk having a track guide is narrower than a track guide pitch on an inner peripheral side, The shape of the recording / reproducing light beam spot on the outer peripheral side is made elliptical, and the width of the recording / reproducing light beam spot on the outer peripheral side in the radial direction of the optical disk is changed to the radial direction of the recording / reproducing light beam spot on the inner peripheral side. An optical disk recording / reproducing method, wherein recording / reproducing is performed with a width shorter than a width of the optical disk.