JPH0574134B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical information recording medium in which the amount of recorded information is increased by laminating a plurality of films having different polarization characteristics, and the optical information recording medium. Regarding writing/reading methods.

(Prior Art) Various methods for optically recording information have been proposed. For example, there is a method in which intermittent laser light is applied to a disk with a metal coating, and the coating is evaporated and dissipated by the thermal energy of the light to record the data.As another example, there is a method in which color changes due to light energy are recorded in the metal structure. There are methods that generate and record the differences.

In recent years, there has been an increasing demand for increasing the amount of recorded information per unit area of such recording media.

(Problems to be Solved by the Invention) In the conventional system, the amount of recorded information on a recording medium and the area occupied by it were in direct proportion. Therefore, in order to increase the amount of recorded information within a unit area of the recording medium, it is necessary to reduce the area occupied by the recorded unit information.

However, there are many physical factors that make it difficult to achieve significant improvements. For example, it is possible to minimize the writing light beam diameter, but currently the diameter is around 1 μm, and it is not possible to make the light beam diameter smaller than that in the optical system.

An object of the present invention is to provide an optical information recording medium that can satisfy the demand for increasing the amount of recorded information by laminating a plurality of films having different polarization characteristics, and a writing/writing method for the optical information recording medium.
The purpose is to provide a reading method.

(Means for Solving the Problems) In order to achieve the above object, an optical information recording medium according to the present invention includes two or more heat mode recording media having different polarization directions sandwiched between an isotropic medium. .

A writing method for an optical information recording medium is a writing method for an optical recording medium in which two or more heat mode recording media having different polarization directions are arranged with an isotropic medium in between, wherein the polarization direction of each heat mode recording medium and Information is written by selectively irradiating the optical information recording medium with a light beam having the same polarization direction to erase the polarization characteristic of the heat mode recording medium having a polarization direction different from the polarization direction of the light beam. It is said that

A method for reading an optical information recording medium is to use an optical information recording medium in which two or more heat mode recording media having different polarization directions are placed with an isotropic medium in between.
In the method for reading an optical information recording medium in which information is written by selectively eliminating the polarization characteristics of each of the heat mode recording media, the optical recording medium is irradiated with a light beam to selectively eliminate the polarization characteristics. The recorded information is read by a combination of the area in which the information is written and the polarization direction of the heat mode recording medium.

(Examples) Hereinafter, the present invention will be described in detail with regard to examples with reference to the drawings and the like.

FIG. 1 is a diagram showing a first embodiment of an optical information recording medium according to the present invention.

In FIG. 1, 10 is a substrate, 11A, 11B
is a polarizing film.

As shown in FIG. 1, the basic shape of the optical information recording medium 1 is such that polymeric polarizing films 11A and 11B are uniformly coated on an optically isotropic and transparent substrate 10 constituting an isotropic medium. Use pasted discs. As the polymer polarizing films 11A and 11B, for example, PVA (polyvinyl alcohol) is used.
is used.

In this embodiment, the optical information recording medium 1 will be explained as a disk, but the same effect can be obtained in the form of a band, sheet, or card, so a description of the shape of the band, sheet, or card will be omitted hereinafter.

FIG. 2 is a diagram showing a writing device for writing information on an optical information recording medium according to the present invention, and FIG.
The figure shows the principle of the information writing process using a light beam.

In FIG. 2, 21A and 21B are laser diodes, 22A and 22B are polarizing filters, 23 is a focal length correction lens system, 24 is a half mirror, 2
5 is a lens system.

Laser light from a laser diode 21A, which is a light source, is passed through a polarizing filter 22 so that it has a linearly polarized plane in a fixed direction. This laser light is made into a narrow beam (about 1 μm in diameter) through a half mirror 24 and a lens system 25, and is irradiated onto the optical information recording medium 1, which is a polarizing film disk. The optical information recording medium 1 includes polarizing films 11A and 11 on a substrate 10.
B are pasted together so that their polarization directions are perpendicular to each other.

In this case, the light source from the laser diode 21A is connected to the polarizing film 1 by the polarizing film 22A.
The polarizing film 11A has a polarization direction perpendicular to the polarizing film 1B, and the polarizing film 11A has a polarization direction that is the same as the polarization direction when the light from the laser diode 21A is passed through the polarizing film 22A. At this time, the laser diode 2
The light energy (thermal energy) from 1A cannot pass through the polarizing film 11B.
Absorption occurs on the 1B plane and generates heat.

When the polarizing film 11B rapidly generates heat in this way, the polarizing film 1
Only the light beam spot portion 1B melts and shrinks or evaporates to form a hole. Since it is sufficient that the polarization property is simply lost due to heat generation without physically forming a hole, the minute regions that have lost their polarization property will be collectively referred to as holes hereinafter. As a result, the light changed to completely pass through and a signal was recorded. On the other hand, since another film 11A on the same line has the same polarization direction as the light source, the light beam energy is transmitted and does not generate heat, so it remains as it is. As a result, only the polarized light component of the polarizing film 11A remains in the portion through which this light beam passes.

Similarly, by the laser diode 21B,
The polarizing film 11B remains, and the polarizing film 11A
The holes will open and allow light to pass through. As a result, only the polarized component of the polarizing film 11B remains (second
Figure 3b).

As a result, recording can be selectively performed on two sides of the polarizing films 11A and 11B by making holes on the sides.

FIG. 4 is a diagram for explaining the information recording state of the first embodiment of the optical information recording medium according to the present invention.

In the optical information recording medium 1 in which films having two types of polarization directions are bonded together as shown in FIG.
By turning on and off the laser diodes 21A and 21B, a total of four signals can be recorded in one beam spot area, as shown in FIG.

FIG. 5 is a diagram showing a reading device for reading information written on an optical information recording medium according to the present invention, and FIG. 6 is a diagram showing a first embodiment of the optical information recording medium according to the present invention. FIG. 3 is a diagram for explaining a reading state.

In FIG. 5, 31 is a laser diode;
2 and 33 are lens systems, 34 are half mirrors, 35
A and 35B are polarizing filters, and 36A and 36B are photodiodes.

When reading a signal written on the optical information recording medium 1, a light beam from the laser diode 31 is irradiated through the lens system 32 onto the optical information recording medium 1 placed on the detector side. The light beam that has passed through the optical information recording medium 1 is split into two directions by a half mirror 34, and is detected by photodiodes 36A and 36B through polarization filters 35A and 35B for each polarization direction.

Note that the light source uses circularly polarized or randomly polarized laser light, but it is not limited to these, and any laser light that has multiple polarization directions of the polarization film may be used, as well as natural light. do not have.

Next, the reading state will be explained with reference to FIG. The light source is represented by ↑↓←→, meaning that it has both polarization planes of the polarizing films 11A and 111B. The polarizing film 1A transmits only the beams indicated by ←→, and does not transmit the beams indicated by ↑↓. The polarizing film 11B transmits only the beams indicated by ↑↓, and does not transmit the beams indicated by ←→.

FIG. 6a shows a state in which both the polarizing films 11A and 11B are not recorded, that is, they are not perforated. At this time, only ↑↓ is transmitted by the polarizing film 11B, but ↑↓ cannot be transmitted through the polarizing film 11A, so no signal appears on the detector side. That is, [0,0] is detected as the information.

FIG. 6b shows a state in which only the polarizing film 11B is perforated. At this time, both polarized light components ↑↓←→ are transmitted through the polarizing film 11B, but ↑↓ is blocked by the polarizing film 11A, and only ←→ is transmitted. That is, [0, 1] is detected as the information.

FIG. 6c shows a state in which only the polarizing film 11A is perforated. At this time, the polarized light components ↑↓ are transmitted through the polarizing film 11B, but they are transmitted through the polarizing film 11A as they are. That is, [1, 0] is detected as the information.

In FIG. 6d, the polarizing films 11A and 11B are both perforated, and since both polarized light components ↑↓←→ are transmitted, [1, 1] is detected as information.

Note that, as in the writing device shown in Figure 2, two light sources are used to alternately irradiate beams with mutually orthogonal polarization components, and a single reading device reads them to generate light with each polarization component. A similar result can be obtained by detecting the on/off state of .

FIG. 7 is a diagram showing another embodiment of the substrate used in the optical information recording medium according to the present invention.

As the substrate 10, it is also possible to use an opaque substrate with minute holes. Basically, any type of substrate can be used, even if it does not transmit light, as long as small holes are continuously and regularly drilled in the substrate. in this case,
An isotropic medium can be thought of as air within its pores.

Small holes 10a are regularly drilled in advance in an opaque substrate 10, and polarizing films 11A and 11B are uniformly pasted on both surfaces of the substrate 10. In the region of the small hole 10a that becomes transparent, the same effect as that of a transparent substrate can be obtained.

Note that the same effect can be obtained even if continuous long holes are used instead of the small holes 10a.

It is also possible to attach two or more polarizing films to one side of the transparent substrate 10, but in this case, the air in the gaps between the polarizing films that are in contact with each other is considered to be an isotropic medium.

FIG. 8 is a diagram showing a second embodiment of the optical information recording medium according to the present invention.

In the second embodiment, as an extension of the first embodiment, a three-layer structure is shown.

In FIG. 8, 10 is a substrate, 11A to 11C
is a polarizing film. The arrows indicate the polarization direction of each of the polarizing films 11A to 11C.

Note that when three polarizing films 11A to 11C with their polarization directions rotated by 60 degrees are stacked to form an optical information recording medium, writing light having only a polarization component in a direction perpendicular to the polarization direction of the polarization film 11A is irradiated. do. At this time, the energy of the writing light is selectively irradiated with different levels of energy to ensure that writing is possible, so that the energy of the writing light is too high and writing is not performed on the polarizing films 11B and 11C. There is.

FIG. 9 is a diagram showing a third embodiment of the optical information recording medium according to the present invention.

In the third embodiment, as an extension of the first embodiment, a structure is provided in which recording polarizing films 11A and 11B attached to the front and back surfaces of a substrate 10 are sandwiched between optically isotropic transparent substrates 12 and 12. This is what I did. This is to protect the surfaces of the polarizing films 11A and 11B.

FIG. 10 is a diagram showing another writing device for writing information on an optical information recording medium according to the present invention.

In this example, one laser diode 41 is used with polarizing filters 42A and 42B exchanged.

Note that when the recording plate is shaped like a disk, each polarizing filter must be rotated in the same direction in synchronization with the rotation of the disk. The preset position is also determined by an address signal or the like.

Further, although the embodiments of the present invention have been described as transmission type recording media, a reflection type may be used in which the beam is reflected after passing through both polarizing films and the reflected light is detected.

(Effects of the Invention) As explained in detail above, according to the present invention,
It is possible to improve the recording density with respect to the occupied area by at least twice or more. Moreover, there is no need to reduce the diameter of the light beam in any way, and the conventionally used diameter of about 1 μm can be used.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of an optical information recording medium according to the present invention. FIG. 2 is a diagram showing a writing device for writing information on an optical information recording medium according to the present invention, and FIG. 3 is a diagram showing the principle of the information writing process using a light beam. FIG. 4 shows the first optical information recording medium according to the present invention.
FIG. 3 is a diagram for explaining the information recording state of the embodiment. FIG. 5 is a diagram showing a reading device for reading information written on an optical information recording medium according to the present invention, and FIG. 6 is a diagram showing a first embodiment of the optical information recording medium according to the present invention. FIG. 3 is a diagram for explaining a reading state. FIG. 7 is a diagram showing another embodiment of the substrate used in the optical information recording medium according to the present invention. FIG. 8 is a diagram showing a second embodiment of the optical information recording medium according to the present invention.
FIG. 9 is a diagram showing a third embodiment of the optical information recording medium according to the present invention. FIG. 10 is a diagram showing another writing device for writing information on an optical information recording medium according to the present invention. 10...Substrate, 11A-11D...Polarizing film, 21A, 21B...Laser diode, 22
A, 22B...Polarizing filter, 23...Focal length correction lens system, 24...Half mirror, 25...
Lens system, 31...Laser diode, 32,3
3...Lens system, 34...Half mirror, 35
A, 35B...Polarizing filter, 36A, 36B...
...Photodiode, 41...Laser diode, 42A, 42B...Polarizing filter.

Claims (1)

[Scope of Claims] 1. An optical information recording medium in which two or more heat mode recording media having different polarization directions are arranged with an isotropic medium in between. 2. The optical information recording medium according to claim 1, wherein the isotropic medium is an optically isotropic plate or gas. 3. In a method for writing an optical recording medium in which two or more heat mode recording media having different polarization directions are arranged with an isotropic medium in between, a light beam having a polarization direction equal to that of each of the heat mode recording media is directed to the optical recording medium. Writing information on an optical information recording medium, characterized in that the information is written by selectively irradiating the information recording medium to erase the polarization characteristics of the heat mode recording medium in a polarization direction different from the polarization direction of the light beam. Method. 4. An optical information recording medium in which two or more heat mode recording media with different polarization directions are arranged with an isotropic medium in between, and information is written by selectively erasing the polarization characteristics of each heat mode recording medium. In a method for reading an information recording medium, the optical recording medium is irradiated with a light beam, and the polarization characteristics are selectively erased to combine the area in which information is written and the polarization direction of the heat mode recording medium, A method for reading an optical information recording medium, comprising reading the recorded information.