JPS61104333A - Optical recording system - Google Patents

Abstract

PURPOSE:To increase the recording capacity by equalizing depths of holes, where information are recorded, to erase recorded information and forming holes different in depth again to record information again. CONSTITUTION:A medium where 8 various recording layers 3-10 are laminated on a substrate 2 is shown in the figure. The recording layer where holes should be formed is varied to form holes different in depth. In the example shown in the figure, upper 4 layers of the medium formed with 8 layers are used to form 4 kinds of hole different in depth. The recording capacity is increased double in comparison with a medium where information is recorded with only presence/absence of holes. The recording capacity is increased more according as the number of layers is increased. Depths of all holes are equalized to the depth of the deepest hole of information recorded on 4 layers to erase information as shown in the figure. For example, light is irradiated to each hole again and the strength or the time of light irradiation is varied, thereby equalizing depths of holes.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an optical recording system.

(Prior art and problems) There are various methods for recording information by focusing a laser beam onto a minute spot using a condensing lens and irradiating it onto the surface of a recording medium to form a hole in the surface of the recording medium. is proposed. However, in the recording method based on the presence or absence of holes, the density within the plane of the medium is determined by the diameter of the beam spot irradiated onto the medium, so it is difficult to increase the recording density within the plane without changing the beam spot diameter. As a solution to this problem, a method has been proposed in which the recording capacity is increased by stacking recording layers in the thickness direction of the medium. (Proceedings of the 1981 National Conference of the Institute of Electronics and Communication Engineers, S5-12). In this method, the medium consists of layers of a blue color former, a red color former, a green color former, and a color developer above and below the three light absorption layers, and each of the three light absorption layers is irradiated with light. By doing so, blue, red, and green coloring layers are obtained. That is, recording and reproduction in each absorption layer is performed by changing the focal position of the beam spot in the depth direction.

However, K, which distinguishes each absorption layer by the difference in focal depth of the beam spot, requires that the interval between each absorption layer be 10 μm or more. This is because if the layer spacing is closer than this, crosstalk will occur and it will be difficult to reproduce each layer independently. Therefore, it is required to form each layer uniformly with a thickness of 100 mm, but it is difficult to form a recording medium with a wide area. The beam spot also needs to be moved by 10 μm or more in the depth direction, which has the drawback that control of the spot position becomes complicated.

Furthermore, the recording method using the above-mentioned medium has the drawback that it cannot be rewritten, that is, information once recorded cannot be erased and rerecorded.

(Objective of the Invention) An object of the present invention is to provide a new optical recording system which can eliminate the above-mentioned drawbacks, increase the recording capacity, and enable erasing and re-recording of information.

(Specific means for solving the problem) The optical recording system of the present invention is an optical recording system in which information is recorded by forming holes with different depths from the recording medium surface by light irradiation.
The feature is that the recorded information is erased by making all the holes in which information is recorded the same depth, and the information is re-recorded by forming holes with different depths again.

FIG. 1 is a diagram showing holes of different depths formed in a single layer of recording medium 1. 2 is a substrate. Such holes can be formed by changing the light irradiation time and irradiation power.

Further, since the depth is 1 μm or less, there is no need to change the position of the focal point of the beam spot in the depth direction.

FIG. 2 shows a medium in which four different recording layers 3 to 10 are stacked on a substrate. Holes of different depths can be formed by changing the recording layer in which the holes are formed. In FIG. 2, holes of four different depths are formed using the top four layers of the eight-layer medium. It can be seen that the recording capacity is twice as large as when information is recorded simply by the presence or absence of holes.

If the number of layers is further increased, the capacity can theoretically be further increased.

Figure 3 shows the case where the information recorded in the four layers shown in Figure 2 is erased by aligning the depth of all the holes with the depth of the deepest hole. . The depth of the holes can be made constant by, for example, irradiating each hole with light again and changing the intensity or time of the light irradiation. Figure 4 is the third
Keep all the holes as shown below with a constant medium.
This is an example of re-recording different information using layers. As described above, the optical recording method of the present invention not only has the effect of simply increasing the recording density, but also enables erasing and re-recording. This method can be applied in various ways to the one having a single recording layer as shown in FIG. 1, but for example, it can be carried out by changing the amount of reflected light. - Due to the interference effect between the light reflected from the surface of the medium where no holes are formed and the inside of the hole, the amount of light changes as shown in Figure 4 with respect to the depth of the hole. The amount of light is minimum at the depth below the wavelength. Therefore, if the depth of the hole is shallower than this, the depth can be detected by the difference in the amount of reflected light.

As a single layer medium, in order to obtain a thickness of about 1 μm, an organic medium such as vanadyl 7-thalocyanine or a material in which a metal such as Ts is dispersed in polystyrene can be used, which is formed on a substrate by vapor deposition or the like. . Or TI, TIOX
, T, etc., and a multilayer medium in which j metals and dielectrics are sequentially laminated can be used. The depth of the hole can be changed by changing the light irradiation power between 1 and 1QmW.

By changing the light irradiation power using the above medium, the depth of the hole is changed and information is recorded, and by changing the light irradiation energy again, the depth of all the holes is made constant, and each hole is further adjusted to correspond to different information. By changing the light irradiation energy, information was recorded at different depths.

In the above description, the method of recording with various hole depths was described, but the erasing and re-recording method of the present invention can also be applied to a method of recording depending on the presence or absence of holes. In this case, the holes may be formed by K so that a portion of the recording layer in the area where the holes are to be formed remains in the thickness direction.

(Effects of the Invention) According to the present invention, it is possible to provide an optical recording system which has a higher recording capacity than conventional optical recording systems and which allows recording to be erased and rerecorded.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a recording medium having a single recording layer used in the present invention, and FIG. 2 is a diagram showing a recording medium having multiple recording layers used in the present invention. FIG. 3 is a diagram of a recording medium showing an erased state of a small amount of recording according to the present invention, and FIG. 4 is a diagram of a recording medium on which data has been rerecorded. FIG. 5 is a diagram showing changes in the amount of reflected light depending on the depth of the hole.

Claims (1)

[Claims] In the optical recording method, information is recorded by forming holes with different depths from the surface of the recording medium through light irradiation. An optical recording method characterized by erasing information and re-recording information by forming holes with different depths.