JPS63263644A - Optical recording and reproducing disk - Google Patents

Abstract

PURPOSE:To enable multi-layered high-density recording by determining the min. size of pits and the optical spacing of recording surfaces so as to satisfy prescribed conditions. CONSTITUTION:The 1st and 2nd recording pits of the min. pit size (a) are recorded on the respective 1st and 2nd recording surfaces of a disk for making optical recording and reproducing. The probability of error generation based on recording of the reproduction signal of the surface 2 on the surface 1 is decreased and the multi-layered high-density recording is enabled if the relation between the size (a) and the optical spacing (d) between the surfaces 1 and 2 is so determined as to satisfy the condition d>1.5a.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing disc, particularly a multilayer optical recording/reproducing disc.

2. Description of the Related Art In recent years, optical recording/reproducing disks have been widely applied, ranging from read-only compact disks to erasable magneto-optical disks. Interest is now in the direction of higher density.

Possible methods for increasing the density include using light with a short wavelength and creating multiple layers on the recording surface. A problem with multilayer recording is interference from other surfaces.

Problems to be Solved by the Invention In multilayer discs, it is desirable that the distance between the recording surfaces be small in order to increase the recording density.

The present invention provides an optical recording/reproducing disk having a minimum interplanar spacing for increasing the recording density during multilayer recording.

Means for Solving the Problems In order to solve the above problems, the optical recording/reproducing disc of the present invention has a disc for optically recording/reproducing, in which the minimum pit size is a, and the optical distance between the recording surfaces is d. ,
□ It is characterized by satisfying the condition of d>15・a.

The above-mentioned optical spacing is a spacing that has been corrected for refractive index and the like.

Function: With the above-described configuration, the present invention can suppress interference between a plurality of recording surfaces to a level that does not pose a practical problem.

Embodiments Hereinafter, optical recording/reproducing discs according to embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram showing the structure of a two-layer optical recording/reproducing disk according to a first embodiment of the present invention. Although FIG. 1 shows the case of a two-layer disc, the same applies even if the number of recording layers is further increased. In FIG. 1, 1 is the first recording surface, 2 is the second recording surface.
3 is a recording pit on the second recording surface, 4 is a recording focus on the second recording surface, and 5 is incident light. Further, let the distance between recording surfaces be d, and the minimum bit size for recording be a. A method for reproducing signals on the disc configured as described above will be explained.

In FIG. 1, incident light 5 is focused on recording pits on the second recording surface. At this time, since the light passes through the recording pits 3 on the first recording surface, the reproduced signal obtained from the reflected light or the transmitted light is influenced by the recording pits 3 on the first recording surface. The degree of this was evaluated by the error rate. FIG. 2 shows some of the actual measurement results. Curve 21 shows the minimum pit size al) < 0.5/1 m1 reproduction wavelength (λ
) is 1.2 μm, curve 22 is the case when the minimum bit size a is 0.5 μm1 reproduction wavelength (λ) is 0.8 μm, and curve 23 is the case when the minimum focus size a is 1.0 μm.
, when the reproduction wavelength (λ) is 0.8 μm. The horizontal axis represents the square of the distance Md, and the vertical axis represents the error rate. As can be seen from FIG. 2, as d becomes smaller, the error rate deteriorates rapidly below a certain value. And that point is unrelated to the reproduction wavelength (λ), and d = 16.3 ・a (
1). Note that this relationship was almost unrelated to the depth of focus.

FIG. 3 shows a schematic diagram of the structure of an optical recording/reproducing disk according to a second embodiment of the present invention. In Figure 3,
31 and 32 are glass substrates, and 33 and 34 are special amorphous tellurium oxide (T e Ox )-based writable recording media deposited on the glass substrates 31 and 32, respectively. This recording medium has a property that the refractive index changes with light of about 20 mw to 3o1). First, the first recording surface 33
Then, the recording surface 34 of the rear cylinder 2 recorded on the second recording surface 34 is reproduced. The intensity of the reproduction signal from the second recording surface 34 is generally smaller than that of the reproduction signal from the first recording surface 33, and its intensity is set to 1/of that of the first recording surface 33. The black portions of the recording surfaces 33 and 34 in FIG. 3 indicate that the refractive index is different from the white portion. Distance between recording surfaces -
There is a breaking point in the relationship between d and the minimum focus size a as shown in FIG. 2, but the relationship changes depending on the intensity. The relationship is d = 18.8 ・J T −a
(2) It was found that -.

The above relationship also holds true in the case of multiple layers of two or more layers. Therefore, the spacing between each layer may be determined using the above formula.

There is a slight difference in the coefficients between equations (1) and (2), but this is thought to be due to the difference in the properties of the pits on the disk. In both the first and second embodiments, there is no practical problem even if the distance between the recording surfaces is somewhat smaller than the distance (d) between the bending points.

in general d〉15・√(k)・a It is better to choose from the above.

Effects of the Invention As described above, the optical recording/reproducing disk of the present invention satisfies the condition that d>15・a, where the minimum pit size of the disk for optically recording and reproducing is a, and the optical distance of the recording surface is d. This enables multilayer high-density recording.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the structure of a two-layer optical recording/reproducing disk according to the first embodiment of the present invention;
FIG. 3 is a diagram illustrating the measurement results of the measurement results shown in FIG. 3, and FIG. l...First recording surface 1.2...Second recording surface, 3...Recording bits on the second recording surface, 4
... Recording pit on the second recording surface, 5...
・Incoming light. Name of agent: Patent attorney Toshio Nakao Haka1 person! -Ol's i! Yarimen 2'''' year old 2's 1i! Record 5 - Incident light figure 2

Claims (2)

[Claims] (1) An optical recording and reproducing disc characterized in that the minimum pit size of the disc for optically recording and reproducing is a, the optical interval of the recording surface is d, and the condition d>15·a is satisfied. (2) Let the minimum pit size of a disc for optical recording and reproduction be a, the optical distance between recording surfaces be d, and the reproduction signal intensity ratio between recording surfaces during reproduction be k (k>1), d>15. √(k
)・a Claim No. (
1) The optical recording/reproducing disc described in item 1).