JPH07320297A - Optical recording medium and optical recording medium reproducing device - Google Patents

Abstract

PURPOSE:To enable super-high resolution reproduction by changing a polarization state changing layer in such a manner that the inside and outside polarization states of a reading out light spot vary with the intensity distribution of the reading out light by irradiation with the reading out light or a temp. distribution. CONSTITUTION:The optical disk 1 consists of a polycarbonate substrate 2, an SiN layer 3 which is a dielectric (protective) layer, a GdFeCo alloy layer 4 as a magneto-optical (MO) mask layer which is a polarization state changing layer, a ZnO-SiO2 layer 5 which is a dielectric protective layer, a Ge2Sb2Te5 layer 6 which is a phase transition recording layer for recording the information, a ZnO-SiO2 layer 7 which is a dielectric (protective) layer, an Al layer 8 which is a reflection layer and 2P overcoating layer which protects the respective layers described above. The perpendicular magnetization directions of all the regions of the MO mask layer 4 of the optical disk are made into the same direction when an initializing magnetic field Hini is impressed on the disk in an initial state. The temp. of part of the irradiated regions AR rises to the Curie temp. or above and the magnetization direction is inverted when the disk is irradiated with the beam spot BS of the reading out light while the reproducing magnetic field Hr is impiessed thereon at the time of reproducing. The plane of polarization of the reading out light is then rotated by a Faraday effect and the information is reproduced via a polarizing filter, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and a reproducing apparatus therefor, and more particularly to recording information having a spatial frequency exceeding the spatial frequency defined by the wavelength of read light at the time of reproduction and the numerical aperture of an objective lens. Also, the present invention relates to an optical recording medium using a phase change recording medium as an information recording layer and a reproducing apparatus therefor.

[0002]

2. Description of the Related Art Conventional CD (Compact Disk) and LD (La
ROM (Read Only Memory) represented by ser disk)
Type optical discs, a photodetector is used to detect a decrease in the amount of reflected light that is caused by diffraction or scattering when the spot of read laser light is applied to the uneven (phase) pits or changes in the optical constants of the pits. Therefore, the information corresponding to the presence or absence of the pit was taken out. More specifically, when the read laser beam spot is irradiated onto the pits (see FIG. 7A), the amount of return light due to reflection due to scattering or the like is small, and the read laser beam spot is present between the pits. When it is irradiated (see FIG. 7B), information is read out by utilizing the large amount of returning light.

A phase change type optical disk is known as an overwrite (rewritable) type optical disk. In this phase change type optical disk, an amorphous portion of a recording layer is formed as a pit and a crystalline portion is formed. Information corresponding to the presence or absence of pits was taken out by detecting the difference in reflectance with a photodetector.

FIG. 8 shows a sectional view of a conventional phase change type disk. As shown in FIG. 8, the phase-change optical disk has a polycarbonate substrate (1.2 mm), a ZnO—SiO ₂ layer (200 nm) that is a dielectric protection layer, and a Ge ₂ layer-change recording layer that records information. Sb ₂ Te ₅ layer (20n
m), a ZnS—SiO ₂ layer (15 nm) that is a dielectric (protection) layer, and an Al layer (200 nm) that is a reflective layer.
And a 2P (Photo-Polymeriyzation) overcoat layer (20 μm) for protecting the dielectric (protective) layer, the phase change recording layer and the reflective layer as a whole.
The numerical values in the parentheses show an example of the thickness of each layer.

The reproduction resolution of the above-mentioned conventional optical disk is determined by the wavelength λ of the read laser light and the numerical aperture NA of the objective lens.
However, there is a problem in that it is not possible to reproduce information having frequency components limited by the spatial frequency f _C = 2NA / λ.

In order to solve this, the MSR (Ma
Super resolution reproduction such as gnetically induced Super Resolution) has been proposed. The MSR will be described here.

It has been conventionally known in the world of microscopes that the resolution is increased by providing an optical mask such as a pinhole at the position of an object. Therefore, the MSR does not provide a physical mask on the medium surface of the magneto-optical disk, but uses the temperature distribution on the medium to generate an effective mask in the medium to effectively reproduce the spatial frequency at the reproduction limit. Is to increase.

As a result, the recording density can be improved by about 1.5 to 3 times. Various magneto-optical disks to which such MSR is applied have been proposed, and an example of the structure is shown in FIG.

The magneto-optical disk comprises a substrate B ', a reproducing layer P'which is in-plane magnetized at room temperature and changes to a perpendicular magnetized state at a temperature higher than a predetermined reproducing temperature, and a recording layer in which information is perpendicularly magnetically recorded. R ', and is comprised.

The reproducing layer P'is formed of, for example, a GdFeCo-based magneto-optical film. The recording layer R'is, for example, D
It is formed of a yFeCo-based magneto-optical film. Next, the recording operation of the magneto-optical disk will be described.

When the temperature of the recording layer R'is raised above the Curie temperature, the magnetic domain of the recording layer R'at that position disappears, and when the temperature is lowered after the disappearance of the magnetic domain, it is applied when the temperature becomes below the Curie temperature. It is magnetized in the direction of perpendicular magnetization of the external magnetic field.

Therefore, by repeating the operation of raising the temperature of the recording layer R ', applying an external magnetic field according to the information to be recorded, and then lowering the temperature, the information is converted into the magnetization direction and recorded in the recording layer. Will be done.

Next, the reproducing operation of the optical disk will be described. When the temperature of the reproduction layer P'is raised above the reproduction temperature,
The reproduction layer P ′ is in the perpendicular magnetization state, and has the same magnetization direction as the recording layer corresponding to the reproduction position.

At this time, when reproducing light which is linearly polarized is irradiated to the reproducing position, since the periphery of the reproducing position is in-plane magnetized state and only the reproducing position is vertically magnetized, deflection due to the magnetic Kerr effect is caused. By detecting the rotation of the surface, the perpendicular magnetization state at the reproduction position can be determined, and the recorded information can be reproduced.

[0015]

By the way, in the above-mentioned conventional phase-change type optical disk, super-resolution reproduction similar to that performed in the above-mentioned magneto-optical disk of MSR is performed only by combining the phase-change phases. It was difficult.

Therefore, the object of the present invention is defined by the wavelength λ of the read laser beam at the time of reproduction and the numerical aperture NA of the objective lens in the optical recording medium using the phase change recording medium as the recording layer and the reproducing apparatus thereof. Spatial frequency f _C = 2NA /
An object of the present invention is to provide an optical recording medium on which information having a spatial frequency exceeding λ is recorded and an optical recording medium reproducing apparatus capable of reproducing the optical recording medium.

[0017]

In order to solve the above problems, the first invention is an optical recording medium using a phase change recording medium as an information recording layer, and the optical recording medium is irradiated from the outside. Corresponding to the intensity distribution of the reading light or the temperature distribution accompanying the irradiation of the reading light, the first polarization state of the reflected light in the first region in the reading light spot on the information recording surface is set to the reading light. A polarization state changing layer that changes the reflected light in the second region, which is the other region in the spot, to be different from the second polarization state is provided.

A second aspect of the present invention is an optical recording medium reproducing apparatus for reproducing recorded information from the optical recording medium of the first aspect of the invention, which is a light irradiating means for irradiating the optical recording medium with read light.
From the reflected light of the irradiated reading light of the optical recording medium,
Separation means for separating only one of the read light having the first polarization state and the read light having the second polarization state, and the read light separated by the separation means is received and output as a read signal. The light receiving means and the reproducing means for reproducing the recorded information on the optical recording medium based on the read signal are provided.

[0019]

According to the first aspect of the invention, the polarization state changing layer is provided within the reading light spot on the information recording surface in accordance with the intensity distribution of the reading light irradiated from the outside or the temperature distribution accompanying the irradiation of the reading light. The first polarization state which is the polarization state of the reflected light in the first area of the
It is changed so as to be different from the second polarization state which is the polarization state of the reflected light in the area.

Therefore, by receiving only one of the read light having the first polarization state and the read light having the second polarization state, the first region within the read light spot on the information recording surface is received. Alternatively, it is possible to reproduce the information of only the phase pits (recording information) recorded in any one of the second areas.

According to the second aspect of the invention, the light irradiating means irradiates the optical recording medium with the reading light, and the separating means selects from the reflected light of the irradiated reading light the optical recording medium. 1
Either the reading light having the polarization state of 1 or the reading light having the second polarization state is separated.

As a result, the light receiving means receives the read light separated by the separating means and outputs it as a read signal to the reproducing means, and the reproducing means reproduces the record information of the optical recording medium based on the read signal.

Thus, either the read light having the first polarization state from the first region or the read light having the second polarization state from the second region, each of which is part of the read light spot. It is possible to reproduce only the recorded information included in the read light spot, and it is possible to reproduce the information having a high spatial frequency as in the case where a plurality of read light spots exist.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described with reference to the drawings. FIG. 1 shows a sectional view of the optical disc of the embodiment.

As shown in FIG. 1, the optical disc 1 includes a polycarbonate substrate 2 (1.2 mm) and a dielectric (protection).
SiN layer 3 (90 nm) which is a layer, a GdFeCo alloy layer 4 (10 nm) which is a magneto-optical (MO) mask layer which is a polarization state change layer, and ZnO- which is a dielectric (protection) layer.
An SiO ₂ layer 5 (150 nm), a Ge ₂ Sb ₂ Te ₅ layer 6 (20 nm) which is a phase change recording layer for recording information,
ZnO-SiO ₂ layer 7 is a dielectric (protective) layer (15n
m), an Al layer 8 (200 nm) as a reflection layer, and 2P (Photo-Polymeriyzation) for protecting the above layers.
And an overcoat layer (20 μm). The numerical values in the parentheses show an example of the thickness of each layer. Further, in this case, the rotation of the polarization state is mainly due to the Faraday effect.

Now, the MO mask layer (GdFeCo alloy layer) 4 will be described. The composition of the GdFeCo alloy layer 4 as the MO mask layer of the optical disc of FIG. 1 is represented by the following composition formula.

Gd _X (Fe _1-Y Co _Y ) _1-X where X: 0.2 to 0.3 and Y: 0 to 0.3, and the thickness is preferably 3.5 to 40 nm.

This allows the read light to pass therethrough, and
This is a condition under which the magnetization direction is reversed by the initializing magnetic field at room temperature, and the magnetization direction is again reversed by the reproducing magnetic field at the reproducing temperature.

FIG. 2 shows a sectional view of an optical disk of another embodiment. As shown in FIG. 2, the optical disk 10 includes a polycarbonate substrate (1.2 mm) 11, a SiN layer 12 (90 nm) that is a dielectric (protection) layer, and a magneto-optical (MO) mask layer that is a polarization state change layer. Pt / Co laminated layer 13 (10 nm) as a layer and ZnO- which is a dielectric (protection) layer.
SiO ₂ layer 14 (170 nm) and Ge ₂ Sb ₂ Te ₅ layer 15 (20 nm) which is a phase change recording layer for recording information.
And a ZnO—SiO ₂ layer 16 that is a dielectric (protection) layer
(15 nm) and the Al layer 17 (200 n
m) and a 2P overcoat layer 18 (20 μm) for protecting each of the above layers. The numerical values in the parentheses show an example of the thickness of each layer, and in this case also, the rotation of the polarization state is mainly due to the Faraday effect.

Now, the MO mask layer (Pt / Co laminated layer) 13 will be described. The Pt / Co laminated layer 13 as the MO mask layer of the optical disc of FIG.
Each Pt layer has a thickness of 0.5 to 2 nm, and each Co layer has a thickness of 0.
The thickness is preferably 2 to 1 nm. In this case, P
It is preferable that the t / Co layer is laminated 5 to 10 times so that the total thickness of the Pt / Co laminated layer is 3 to 40 nm.

This allows the read light to pass therethrough, and
This is a condition under which the magnetization direction is reversed by the initializing magnetic field at room temperature, and the magnetization direction is again reversed by the reproducing magnetic field at the reproducing temperature.

Here, the magneto-optical disk in the present embodiment
The reproduction principle of is described with reference to FIG. initial state
By an initialization magnetizing means such as a permanent magnet not shown in FIG.
Initializing magnetic field H _iniIs applied, the MO mass of the optical disk
The perpendicular magnetization directions of all regions of the
(Upward in the drawing) (see FIG. 3B).

When reproducing, as shown in FIG. 3B, when the reproducing magnetic field H _r is applied and the beam spot BS having the output of the read light adjusted is irradiated (see FIG. 3A), The perpendicular magnetization direction of the region AR is reversed by raising the temperature of at least a part of the region AR irradiated with the beam spot to the Curie point temperature (T _C ) or higher.

As a result, in the area AR where the perpendicular magnetization direction is reversed in the beam spot, the plane of polarization of the read light is changed by a predetermined angle (+ θ) depending on the MO mask layer due to the Faraday effect which is a magneto-optical effect. Rotate.

Further, in the area XAR other than the area AR in the beam spot, the MOF is similarly increased by the Faraday effect.
The plane of polarization of the readout light rotates counterclockwise with respect to the inside of the area AR by a predetermined angle (-θ) depending on the mask layer.

Therefore, if the read light from the area AR and the read light from the area XAR are separated using a separating means such as a polarization filter or a differential optical system, the area AR or the area XA is separated.
Information of only one of R can be selectively reproduced.

This means that a pinhole having an opening smaller than the diameter r of the reading light spot defined optically by the wavelength λ of the reading light and the numerical aperture NA of the objective lens is provided on the information recording surface of the optical disk. This is equivalent to the above, and it becomes possible to reproduce the information of a pit having a minute size such that a plurality of pits exist in the reading light spot, that is, a pit having a high spatial frequency f (f> f _C ).

FIG. 4 shows the structure of the main part of the optical disk reproducing apparatus. The optical disk reproducing device 20 includes a laser diode 21 that emits a laser beam that is a reading beam, and a beam splitter 22 that transmits the laser beam incident from the laser diode 21 and reflects the laser beam incident from a mirror described later.
A mirror 23 for guiding the laser beam, and an objective lens 24 for condensing the laser beam on the information recording surface of the optical disc DK.
And a half-wave plate for adjusting the ratio of the reflected light amount and the transmitted light amount of the laser light from the non-reading area of the laser light (reproduction light) reflected by the beam splitter 22 to the polarization beam splitter described later. 25,
The polarization beam splitter 26 that transmits only the polarized light having the predetermined polarization state and reflects the other light, and the polarized light reflected by the polarized beam splitter are received, and the first read signal R ₁
The first light receiving element 27a for outputting as (RF signal) and the polarized light transmitted through the polarization beam splitter 16 are received and
The second light receiving element 27b for outputting as the read signal R ₂ (RF signal), the reproducing circuit 28 including a decoder, an amplifier and the like for converting the read signal R into the reproduced signal S and outputting the same, and the perpendicular magnetization direction of the optical disk DK. aligned in a direction (hereinafter, referred to as initialization.) magnet MG ₁ and (initializing magnetic field H _ini), reproducing magnet MG ₂ (reproducing magnetic field aligned in the opposite direction to the initializing magnet MG ₁ a perpendicular magnetization direction of the optical disc DK at the time of reproduction H _r ),
It is configured with.

In this case, assuming that the coercive force of the MO mask layer is H _C , the initialization magnetic field H _ini and the reproducing magnetic field H
_r is preferably 500 oersted <H _ini <3000 oersted 300 oersted <H _r <3000 oersted, and more preferably H _r <H _C <H _ini .

Next, the operation of this embodiment will be described with reference to FIGS. 4 and 5. First, an external magnetic field H _ini is applied to the magneto-optical layer of the optical disk DK by using an initialization magnet MG ₁ to initialize the perpendicular magnetization direction before reading recorded information to a fixed direction (initialization: upward direction in the drawing). Do. Further, if necessary, the perpendicular magnetization directions of all the areas of the optical disk DK are initialized in advance by the magnet MG ₁ , the perpendicular magnetization direction for reading is reversed by the magnet MG ₂ , and then initialized again by the magnet MG _1. May be.

In the following description, an optical disc is used in advance.
The perpendicular magnetization direction of all areas of the disk DK is changed to the magnet MG.₁By
The case of initialization is described below. Laser diode
Reading light (laser light) that is linearly polarized light emitted from 21
The spot LB of the mirror 23, the beam splitter 2
2. Information recording on the optical disk DK via the objective lens 24
The light is focused on the surface and, as shown in FIG.
₁A beam spot BS is formed on top of this beam spot
To BS is track T due to rotation of disk DK₁Move up
Move.

By the way, on the track T ₁ , the spatial frequency f _C = 2NA / λ, which is defined by the wavelength λ of the reading light and the numerical aperture NA of the objective lens 24, is exceeded (f> f).
A pit having f _C ) is formed. In particular,
There are a plurality of pits P ₂ and P ₃ in the beam spot BS, and the information of these pits P ₂ and P ₃ cannot be separated as they are, and correct reproduction cannot be performed. Similarly, as shown in FIG. 5B, a plurality of tracks T ₀ ′, T ₁ ′, T ₂ ′ are provided in the beam spot BS.
Even if such a character is included, correct reproduction cannot be performed.

Therefore, when the output of the reading light is adjusted, the result shown in FIG.
As shown in (c), the temperature of the MO mask layer is the temperature T at which the coercive force H _C of the MO mask layer becomes smaller than the reproducing magnetic field H _r in the area AR behind the beam spot BS.
(For example, 150 ° C.) or higher (T <Cu Curie temperature T _C of the MO mask layer) and, for example, in the case shown in FIG. 5A, the magnetic domain in the region AR where the pit P ² exists is the reproducing magnetic field. Invert by H _r .

As a result, in the area AR where the magnetic domains are reversed, the polarization plane of the reproduction light, which is the reflection light of the readout light by the information recording surface, is changed from the polarization plane of the readout light by the magneto-optical effect.
With a predetermined angle (+ θ) rotation depending on the mask layer,
It returns to the light receiving elements 27a and 27b side. On the other hand, in the area XAR where the pits P ₃ are present in the beam spot BS except the area AR, the polarization plane of the reproduction light is dependent on the MO mask layer due to the magneto-optical effect as compared with the polarization plane of the read light. The light returns to the side of the light receiving elements 27a and 27b in a state in which it is rotated by a predetermined angle (−θ) in the direction opposite to the rotation in AR.

Although the reproduction light from the area AR and the area XAR reaches the light receiving elements 27a and 27b in a mixed state, the amount of the reproduction light from the area XAR is adjusted by adjusting the half-wave plate 25 and the like. And the second light receiving element 27b are set so as to be incident in equal amounts, the first read signal R ₁
And the second read signal R ₂ (differential output), the area X
The signal component due to the reproduction light from the AR is canceled out, and the area XA
R is apparently shielded. Therefore, in the reproducing circuit 28, the area AR, that is, the pit P ₂
It becomes possible to read out only the information of, and the reproduction signal S contains only the information of the pit P ₂ .

As described above, according to this embodiment,
In an optical disc using a phase change recording medium, a spatial frequency f exceeding a spatial frequency f _C (= 2NA / λ) defined by the wavelength λ of the reading light and the numerical aperture NA of the objective lens 14.
It becomes possible to reproduce the information having

When performing continuous reproduction, an external magnetic field H _ini is applied to the magnet MG ₁ during reproduction so that the perpendicular magnetization direction becomes the same as the initialized state in the process of cooling the area AR. It suffices to provide a second magnet and perform re-initialization after reading the information.

Further, the optical system in the above embodiment is equivalent to the rewritable magneto-optical disk recording / reproducing apparatus which is widely used at present, so that the apparatus can be shared.

Furthermore, since the apparently shielded area can be set by adjusting the half-wave plate 25, etc., as shown in FIG. 5B, not only the pit row direction but also the track pitch. Even if the optical disc is densified in the direction as well, the occurrence of crosstalk between tracks and crosstalk between pits can be reduced or neglected, so that information of only desired pits can be accurately reproduced. . Experimental Example Next, a reproduction experiment in which the optical disk of FIG. 1 (Example a) and the optical disk of FIG. 2 (Example b) were actually prepared and compared with the conventional optical disk of FIG. 9 will be described.

The measurement conditions are shown below. Objective lens numerical aperture NA: 0.55 Laser light wavelength λ: 680 nm The entire optical disc is initialized in advance, and then a differential output is taken as a parameter of the reproduction laser light to obtain C / N.
(Carrier to Noise ratio) was measured by changing the recording mark length. The result is shown in FIG.

Using the above optical system, the pit length corresponding to the limit of the reproduction resolution of the conventional phase change type optical disk of FIG. 9 is about 0.3 μm. By applying the present invention, the conventional reproducing method can be used. Very small size (0.
(Less than 3 μm), that is, it is possible to detect information carried by pits having a high spatial frequency.

Further, in each of the above embodiments, the laser light emitted from the laser diode 11 is directed to the beam splitter 1.
Although the information recording surface of the optical disk DK was directly irradiated via the mirror 2, the objective lens 14 and the mirror 2, a polarizing plate is provided in the optical path between the laser diode 11 and the beam splitter 12 in order to improve linear polarization. The optical disc DK may be provided and irradiated onto the optical disc DK via a polarizing plate.

Furthermore, in each of the above embodiments,
Although the case where the readout light is linearly polarized light has been described, it may be configured to use elliptically polarized light. Also,
Since the polarization states are not limited to two types, the reproduction light having one polarization state may be separated from the reproduction light having a plurality of polarization states.

[0054]

According to the first aspect of the present invention, the polarization state change layer has the read light on the information recording surface corresponding to the intensity distribution of the read light irradiated from the outside or the temperature distribution accompanying the irradiation of the read light. The first polarization state, which is the polarization state of the reflected light in the first area within the spot, is changed to the second polarization state, which is the polarization state of the reflected light in the second area that is another area within the read light spot. Since it is changed so as to be different from that, the reading light spot on the information recording surface is received by receiving only one of the reading light having the polarization state of the first polarization state and the reading light having the second polarization state. It becomes possible to reproduce only the information of the pits (recording information) recorded in either the first area or the second area.

According to the second invention, the read light having the first polarization state from the first region or the second polarization state from the second region, each of which is a part of the read light spot. It is possible to reproduce only the recorded information contained in only one of the read light beams having the read light, and it is possible to reproduce the information having a high spatial frequency as in the case where a plurality of read light spots exist. Become.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a detailed structure of an optical disc of an example (example a).

FIG. 2 is a cross-sectional view showing a detailed structure of an optical disc (Example b) of another example.

FIG. 3 is a diagram illustrating the principle of reproducing an optical disc.

FIG. 4 is a configuration diagram of a main part of an optical disc reproducing apparatus according to an embodiment.

FIG. 5 is an explanatory diagram of a reproduction operation.

FIG. 6 is an explanatory diagram of a reproduction experiment.

FIG. 7 is an explanatory diagram of an information reading principle of a conventional ROM type optical disc.

FIG. 8 is a sectional view showing a detailed structure of a conventional optical disc.

FIG. 9 is a cross-sectional view showing the structure of a conventional MSR optical disc.

[Explanation of symbols]

1 ... optical disc 2 ... polycarbonate substrate 3 ... dielectric layer (SiN layer) 4 ... magneto-optical mask layer (GdFeCo alloy layer) 5 ... dielectric layer (ZnS-SiO ₂ layer) 6 ... phase change recording phase 7 ... dielectric layer (ZnS-SiO ₂ layer) 8 ... Reflective layer (Al layer) 9 ... 2P overcoat layer 10 ... Optical disc 11 ... Polycarbonate substrate 12 ... Dielectric layer (SiN layer) 13 ... Magneto-optical mask layer (Pt / Co laminated layer) 14 ... dielectric layer (ZnS-SiO ₂ layer) 15 ... phase change recording phase 16 ... dielectric layer (ZnS-SiO ₂ layer) 17 ... reflective layer (Al layer) 18 ... 2P overcoat layer 20 ... optical disk reproducing apparatus 21 ... Laser diode 22 ... Beam splitter 23 ... Mirror 24 ... Objective lens 25 ... Half wave plate 26 ... Beam splitter 27a ... First light receiving element 27b ... Second light receiving Element 28 ... reproducing circuit MG ₁ ... initialization magnet MG ₂ ... Play magnets BS ... beam spot P ₁ to P ₄ ... Pit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Yoneda 6-1-1, Fujimi, Tsurugashima City, Saitama Pioneer Research Institute

Claims (2)

[Claims] 1. An optical recording medium using a phase change recording medium as an information recording layer, wherein the intensity distribution of read light externally applied to the optical recording medium or the temperature distribution associated with the irradiation of the read light. Correspondingly,
The first polarization state of the reflected light in the first area in the reading light spot on the information recording surface is changed to the second polarization of the reflected light in the second area which is another area in the reading light spot. An optical recording medium, characterized in that a polarization state change layer for changing the state to be different from the state is provided. 2. An optical recording medium reproducing apparatus for reproducing recorded information from the optical recording medium according to claim 1, wherein the optical recording medium is irradiated with read light, and a light irradiation unit for irradiating the irradiated read light is used. From the reflected light of the optical recording medium,
Separation means for separating only one of the read light having the first polarization state and the read light having the second polarization state, and the read light separated by the separation means is received and output as a read signal. An optical recording medium reproducing apparatus comprising: a light receiving unit; and a reproducing unit that reproduces recorded information on the optical recording medium based on the read signal.