JPS61137241A - Recording medium of optical information - Google Patents

Abstract

PURPOSE:To obtain a stable reproducing signal with a high SN ratio by providing the 1st element consisting of the 1st plane in which a unit information element guides incident light flux in the 1st direction and the 2nd element consisting of the 2nd plane guiding the incident light flux in the 2nd direction different from the 1st one. CONSTITUTION:In case of applying the titled recording medium to an optical information recording card, a recording pit part of a unit information element E formed on a transparent plastic substrate 5 has a plane 5a having 10 deg. inclined angle theta. The plastic substrate 5 having plural recording pits is formed by embossing work. Then, an aluminum film 4 is formed by vacuum evaporation and a polystyrene layer 6 (1.59 refractive index) is finally formed to form the optical information recording card.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical information recording medium applicable to optical discs, optical carts, optical tapes, and the like.

[Prior Art] Various types of media such as optical disks, optical cards, and optical tapes have been known as media for recording and reading information using light. The principles of recording or reading information in these media vary depending on the type of media material used, the optical system used for recording or reading, and the type of system, and several methods have been put into practical use. A typical example is a method of detecting a signal by changing the direction of magnetization of the medium using light, such as a magneto-optical recording medium, and changing the change in Kerr rotation angle that occurs when irradiated with read light into light intensity; Alternatively, there is a method of recording and reproducing by changing the light transmittance 2 reflectance and absorption spectrum of the medium only in the portion corresponding to information, or by changing the refractive index and shape of the information recording part of the medium and irradiating the recording part. There is a method of detecting a change in light intensity corresponding to a signal using phenomena such as diffraction and interference of reproduced light.

In all of these conventional examples, information is detected as changes in light intensity, so improving the S/N of the reproduced signal as much as possible is an important technical issue required of the media or system. .

Among these conventional optical information recording media, there is one that has a relatively simple structure and can obtain a good S/N ratio of a reproduced signal, in which unit recording areas are recorded in the form of pits. FIG. 7 is a diagram showing the structure and signal reproduction principle of an optical information recording medium in which such a recording area is composed of pits.

In the figure, numeral 21 indicates an information recording medium such as an optical disk, and numeral 22 indicates a unit recording area, which is an information portion recorded on the medium, and has concave depressions (hereinafter referred to as pits).

The pits 22 are formed as concave or convex shapes by embossing on a substrate 25 made of plastic, for example. A light reflecting film 24 is provided on the upper part of the substrate 5 including the pits 22.
is formed by vapor deposition or the like, and the light reflecting film 24 is
In the second part there is a transparent protective layer 23. To reproduce information, reproduction light 27 is focused onto pit 22 through lens 26. The focused light is diffracted by the pits 22,
Since it becomes scattered light 28 and is scattered outside the effective aperture of the lens 26, the amount of light that returns to the lens 26 changes again, and by detecting the change in the amount of light with a light detection means (not shown), it becomes possible to reproduce information. .

The method of detecting a signal by reading the decrease in the amount of reflected light due to diffraction at the edge of the concave or convex surface of the pit, or the decrease in the amount of reflected light due to interference between the bottom of the concave surface or the top of the convex surface and the surrounding surface is S. /N ratio (signal-to-noise ratio) is generally insufficient.

[Summary of the Invention] An object of the present invention is to provide an optical information recording medium having a novel structure that solves the drawbacks of the prior art. That is, the present invention provides an optical information recording medium that can obtain a stable reproduced signal with a good S/N ratio, has a wider range of applications than before, and has a structure that can be manufactured at low cost. This is what we provide.

In the optical information recording medium according to the present invention, the unit information element of the optical information recording medium representing binary information includes a first element made of a first plane that guides an incident light beam in a first direction, and a first element made of a first plane that guides an incident light beam in a first direction. The above object is achieved by providing a second element consisting of a second plane that forms a predetermined angle with the plane and guides the incident light beam in a second direction different from the first direction. be. That is, in the optical information recording medium according to the present invention, the portion where the unit information area is recorded (hereinafter simply referred to as the recording pit portion) is inclined with respect to the surrounding surface, that is, the surface without the recording pit portion. It is characterized in that the illumination light incident on the recording pit portion is reflected or transmitted in a direction different from that of the illumination light incident on the surrounding surfaces. By using such an inclined recording pit section, the light beam that is reflected or transmitted through the recording pit section and the light beam that is also reflected or transmitted through the portion without the recording pit section are reliably separated spatially, and the signal/ The noise ratio improves dramatically. The present invention will be explained in detail below.

[Embodiment] FIGS. 1A and 1B are diagrams showing an embodiment of an optical information recording medium according to the present invention, and are cross-sectional views when applied to an optical information recording card. (A) shows a cross section where a recording pit portion exists, and FIG. 1(B) shows a cross section where a recording pit portion does not exist.

The size of the unit information element L-E provided on the transparent plastic substrate 5 having a length of 54 mm, a width of 86 mm, and a thickness of 0.5 mm is 10 m x 10 IL' m, and the recording pit part has an inclination angle θ of 10 degrees. It has a flat surface 5a having an inclination angle of . A plastic substrate 5 having a plurality of such recording pit portions was formed by embossing. continue,
An aluminum An film 4 is formed to a thickness of 3000A by vacuum evaporation, and finally a polystyrene layer 6 (refractive index 1.59) is formed.
) to create an optical information recording card. FIG. 2 shows a schematic diagram of a reading optical system that illuminates and receives light from this recording card. In the figure, 7 is a light source such as an LED, 9 is the recording surface of the optical card, 10 is an optical system that projects the light beam from the light source onto the optical information recording card, 8 is a light receiving element, and 11 is the recording surface of the optical information recording card. This is an optical system that receives the light beam from the recording pit portion and forms an image on the surface of the light receiving element 8. Assuming that the angle of incidence in the air of the illumination light beam 1 from the light source 7 and the projection optical system 10 on the recording surface 9 is 33 degrees, the light beam irradiated onto the recording pit portion is reflected by the inclined surface and exits perpendicularly to the recording surface 9. The luminous flux 2 (FIG. 1A) is obtained as follows.

This light beam 2 is imaged onto the light receiving element 8 by the imaging optical system 11 and detected. On the other hand, the illumination light beam 1 irradiated onto the surface other than the recording pit portion becomes a light beam 3 (FIG. 1B) that is specularly reflected into the air at a reflection angle of 33°. Like this,
When the light beam from the recording surface 9 was received by the light receiving element 8, the signal/noise ratio (S/N ratio) was sufficient for practical use.

In the reading optical system shown in FIG. 2, the light receiving element 8 receives the reflected light from the recorded pit portion as a signal light. A configuration may be adopted in which the specularly reflected light 3 is received by the light receiving element 8.

3(A) and 3(B) are views showing other embodiments of the optical information recording medium according to the present invention, FIG. 3(A) is a sectional view of a portion where a recording pit portion is present, and FIG. (B) is a diagram showing a cross section of a portion where no recording pit portion exists. FIG. 4 is a diagram showing a reading optical system for reading information from the optical information recording medium shown in FIGS. 3(A) and (B). Components having the same numbers as those in FIGS. (A), CB) and FIG. 2 represent the same members, so their explanation will be omitted here. Vertical 54. mm
A plurality of recording pit portions as shown in FIG. 3(A) were formed by embossing on a transparent plastic substrate 5 having a width of 86 mm and a thickness of 0.5 mm. The recording pit portion has a rectangular size of 107 tm×107 t, and has a flat surface 5a with an inclination angle θ of 45°. An aluminum film 4 was obliquely deposited on the embossed plastic substrate 5 so that the film could only be formed on the inclined surface 5a of the recording pit portion and on surfaces other than the recording pit portion. Therefore, the aluminum film 4 is not provided on the surface 5b of the recording pit portion other than the inclined surface 5a. Subsequently, a PMMA layer (refractive index: 1.49) 6 was provided as a laminate layer on the aluminum film 4 to produce an optical information recording card.

Next, an optical system for reading information from this optical information recording medium will be explained using FIG. 4. Illumination light beam 1 from light source 7 is bent by beam splitter 12 and enters recording surface 9 perpendicularly. The light beam 1 irradiated onto the recording pit portion is reflected by the inclined surface 5a, and then reflected by the surface 5 on which aluminum is not vapor-deposited.
b, and becomes a light beam 2 that is emitted to the back side of the recording surface 9. Luminous flux l irradiated onto the recording surface other than the recording bit area of the recording surface 9
becomes a light beam 3 that is specularly reflected in a direction perpendicular to the recording surface 9, and after passing through the beam splitter 12,
The light is received by the light receiving element 8. In this way, the light beam irradiated to the recording pit portion almost completely passes through to the back surface, so that a very high S/N ratio can be obtained.

5(A) and 5(B) are diagrams showing other embodiments of the optical information recording medium according to the present invention, FIG. 5(A) shows a portion where a recording pit portion exists, and FIG. 5(B) indicates a cross section of a portion where no recording pit portion exists.

FIG. 6 is a diagram showing a reading optical system for reading information from the optical information recording medium shown in FIGS. 5(A) and 6. Components with the same numbers as those in the embodiment represent the same components, so a description thereof will be omitted here. Height 54mm, width 86mm, thickness 0.5
MRA polymethylmethacrylate-1 (PMMA) substrate (refractive index 1.49) was embossed to form a
) 107pm square inclined plane 5a like
A plurality of recording pit portions were formed. The inclination angle θ of the plane 5a of the recording pit portion was 35 degrees. Subsequently, a polyvinylcarbazole (PVC) layer 6 having a refractive index of 1.68 was laminated on top to produce an optical information recording card. Fifth
As shown in Figure (A), the light beam 1 incident on the recording pit portion at an incident angle of 60° is totally reflected on the inclined surface 5a between the PMMA substrate 5 and the PVC layer 6, and the traveling direction is completely different from that of the incident light beam 1. Different light beams 2 are emitted from the optical card. On the other hand, as shown in FIG. 5(B), the light beam 1 incident at an incident angle of 60° on a portion other than the recording pit portion is
The light passes through the MA substrate 5 and becomes an outgoing light beam 3 in the same direction as the incident light beam 1. In order to detect the recording pit part by utilizing the fact that the direction of the light flux incident on the recording pit part and the non-recording pit part i changes when it is emitted from the optical information recording card, the recording pit part is detected. As shown in , the luminous flux 1 from the light source 7
．． ! - The light-receiving element 8 is arranged at a position that receives the light beam 3 emitted from the optical information recording card in a substantially parallel relationship. In this example as well, a very high S/N ratio was obtained because the light beams from the recorded pit area and the non-recorded bit area could be completely separated.

In this example, the substrate on which the recording pit portions were formed was formed by embossing, but other methods include injection molding, mask exposure, or electron beam exposure. Recording pits can be formed by interference fringe exposure method or the like.

As described above, in the optical information recording medium according to the present invention, the light flux from the recording part and the light flux from the non-recording part can be well separated, so that it can be read with a very good S/N ratio. be.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an optical information recording medium according to the present invention, FIG. 2 is a diagram showing an example of a device for reading the medium shown in FIG. 1, and FIG. 3 is a diagram showing an example of an optical information recording medium according to the present invention. FIG. 4 is a diagram showing an example of a device for reading the medium shown in FIG. 3; FIG. 5 is a diagram showing a further embodiment of the optical information recording medium according to the present invention; 614 is a diagram showing an example of a device for reading the medium shown in FIG. 3, and FIG. 7 is a diagram showing a conventional optical information recording medium. 4-11 fouling layer, 5-m-substrate, 6--polystyrene layer, 6'---PMMA layer, 6'
-11 polyvinyl rubazole layer, 7---light source. 8--one light receiving element, 9-m-recording surface.

Claims (1)

[Claims] (1) In an optical information recording medium showing binary information, a unit information element has a first element formed of a first plane that guides an incident light beam in a first direction, and the first plane forms a predetermined angle. An optical information recording medium comprising: a second plane that guides an incident light beam in a second direction different from the first direction.