JP2009099192A - Information recording medium, information reproducing method, information recording method, and information recording and/or reproduction apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information recording medium for recording multivalued information in a recording portion by a simple geometric structure, and to provide an information reproducing method, an information recording method, and an information recording and/or reproducing apparatus for the information recording medium. <P>SOLUTION: The multivalued information recorded in the recording portion is read out from the information recording medium by irradiating the recording portion with reading light and sensing reflected light from the recording portion. In the recording portion, inclined reflection surfaces having predetermined areas and predetermined inclination angles are formed so that the surfaces form a plurality of azimuth angles corresponding to the multivalued information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an information recording medium, an information reproducing method, an information recording method, an information recording and / or reproducing apparatus, and in particular, an information recording medium that utilizes the reflection characteristics of polarized light and supports the recording and / or reproducing of multilevel information, The present invention relates to an information reproducing method, an information recording method, an information recording and / or reproducing apparatus.

  In recent years, with the increase in the amount of information processed by information equipment or audiovisual equipment, etc., information recording such as an optical disk, which is easy to access data, can store large amounts of data, and can cope with downsizing of equipment. The medium is drawing attention. In order to improve the in-plane recording density of an information recording medium such as an optical disc, the objective lens used for information reproduction has a large numerical aperture NA (Numerical Aperture) and the wavelength of the reading light to be used is shortened. It is effective to reduce the spot diameter of the light condensed by, for example, an information recording system including an optical system including a laser light source having a wavelength of about 405 nm and a condensing lens having a numerical aperture NA of 0.85. In addition, an information recording medium in which information is recorded and / or reproduced using a reproducing apparatus has been proposed (Blu-ray Disc standard).

  Further, in an information recording medium capable of recording / reproducing using a high NA optical system typified by Blu-ray Disc, a plurality of signal surfaces are provided, and a multilayer type information in which the capacity is further increased by stacking the signal surfaces. A recording medium can be realized. For example, in the Blu-ray Disc standard, it is possible to store data having a capacity of about 25 GB for a single recording layer and about 50 GB for a two-layer recording layer.

In recent years, both the increase in the numerical aperture (NA) of objective lenses and the shortening of the wavelength of reading light are approaching the limits, so that multi-value information can be recorded three-dimensionally to greatly break the current situation. A hologram type information recording medium has also been proposed (see, for example, Patent Document 1).
JP 2007-225964 A

  However, many holographic methods have been proposed as information recording media for recording multi-value information. For example, information recording for recording multi-value information with a simple configuration having a geometric shape in the recording unit. No media was proposed. If an information recording medium that records multi-value information with a simple configuration having a geometric shape in the recording unit can be realized, for example, a conventional information processing medium that can be reproduced by a stamper, imprint, or the like is applied to a conventional shape processing method. It can be easily realized without significant changes. A recordable information recording medium can also be realized. Furthermore, an information reproducing method, information recording method, information recording and / or reproducing apparatus corresponding to multilevel information can be realized by using polarized light.

  The present invention has been made in view of the above, and an information recording medium for recording multilevel information with a simple configuration having a geometric shape in a recording unit, an information reproducing method and information corresponding to such an information recording medium It is an object to provide a recording method, an information recording and / or reproducing apparatus.

  In order to achieve the above object, according to a first aspect of the invention, reading light is applied to a recording unit, and reflected light reflected by the recording unit is detected, whereby multi-value information recorded on the recording unit is read. In the information recording medium, an inclined reflection surface having a predetermined area and having a predetermined inclination angle is formed on the recording unit so as to form a plurality of types of azimuth angles corresponding to the multi-value information. It is characterized by that.

  According to a second aspect of the present invention, there is provided an information recording medium in which multi-value information recorded in the recording unit is read by irradiating the recording unit with reading light and detecting reflected light reflected by the recording unit. The recording unit is characterized in that an inclined reflecting surface having a predetermined area and having a predetermined azimuth angle is formed so as to form a plurality of types of inclination angles corresponding to the multi-value information.

  According to a third aspect of the present invention, there is provided an information recording medium in which multi-value information recorded in the recording unit is read by irradiating the recording unit with reading light and detecting reflected light reflected by the recording unit. In the recording unit, an inclined reflecting surface having a predetermined region is formed in combination so as to form a plurality of types of inclination angles and a plurality of types of azimuth angles corresponding to the multi-value information. And

  According to a fourth aspect of the present invention, there is provided an information recording medium for reading multi-value information recorded in the recording unit by irradiating the recording unit with reading light and detecting reflected light reflected by the recording unit. The recording unit is characterized in that one or a plurality of inclined reflecting surfaces having a predetermined area and having a predetermined azimuth angle are formed.

  According to a fifth aspect of the present invention, multi-value information is recorded by irradiating the recording light with the recording light, and the recording light on which the multi-value information is recorded is irradiated with reading light and reflected by the recording part. An information recording medium from which the multi-value information recorded in the recording unit is read by detecting light, and has an inclined reflection surface having one or more predetermined inclination angles having a predetermined area. And a recording layer made of a material to which optical anisotropy is added on the inclined reflecting surface.

  According to a sixth aspect of the present invention, a multi-value information is recorded by applying a recording magnetic field or a recording electric field to the recording unit, and the recording unit on which the multi-value information is recorded is irradiated with reading light, and the recording unit An information recording medium from which the multi-value information recorded in the recording unit is read by detecting reflected light reflected by the recording unit, and is inclined at one or more predetermined inclination angles having a predetermined area It has a reflective surface, and has a recording layer made of a material to which optical anisotropy is added on the inclined reflective surface.

  7th invention is the information recording medium which concerns on 1st invention, The said recording part has a corner cube whose said predetermined inclination | tilt angle which makes a reciprocating optical path with three said inclined reflective surfaces is 45 degrees, The ridge line of the corner cube is formed so as to form a plurality of types of azimuth angles corresponding to the multi-value information.

  According to an eighth aspect of the present invention, in the information recording medium according to the first aspect, the recording unit has the inclined reflecting surface whose predetermined inclination angle is 30 °, and the inclined reflecting surface is the multi-value information. Correspondingly, it is formed so as to form a plurality of types of azimuth angles.

  According to a ninth aspect of the present invention, in the information recording medium according to the first aspect, the recording unit has a V-groove having a predetermined inclination angle of 45 ° that forms a reciprocating optical path between the two inclined reflection surfaces, The ridge line of the V groove is formed so as to form a plurality of types of azimuth angles corresponding to the multi-value information.

  According to a tenth aspect of the invention, in the information recording medium according to any one of the first to ninth aspects, total reflection of a dielectric is used as the inclined reflection surface.

  According to an eleventh aspect of the present invention, in the information recording medium according to any one of the first to ninth aspects, a back surface reflection of a dielectric is used as the inclined reflection surface.

  A twelfth aspect of the invention is that the recording unit of the information recording medium according to any one of claims 1 to 11 is irradiated with reading light in a known polarization state and is reflected by the recording unit. It is an information reproducing method for detecting the state and reading the multi-value information recorded in the recording unit by specifying the predetermined tilt angle and / or the predetermined azimuth angle from the detected polarization state. Features.

  A thirteenth invention is characterized in that, in the information reproducing method according to the twelfth invention, the polarization state of the reading light is circularly polarized light, and the polarization state of the reflected light is elliptically polarized light.

  A fourteenth aspect of the invention is the information reproducing method according to the twelfth or thirteenth aspect of the invention, wherein the reading light is the first reading light whose polarization state is right circular polarization and the polarization state is left circular polarization. And a second reading light, wherein the first reading light and the second reading light are irradiated so as to form a predetermined half space.

  In a fifteenth aspect of the invention, the recording layer of the information recording medium according to claim 5 is irradiated with recording light, and optical anisotropy is added to the material of the recording layer, whereby multi-value information is recorded on the recording layer. It is the information recording method to do.

  According to a sixteenth aspect of the present invention, a recording magnetic field or a recording electric field is applied to the recording layer of the information recording medium according to claim 6 to add optical anisotropy to the recording layer material. It is an information recording method for recording multi-value information.

  According to a seventeenth aspect of the present invention, there is provided reading light irradiating means including a light source that irradiates the recording unit of the information recording medium according to any one of the first to eleventh aspects with reading light having a known polarization state. Reflected light detection means for detecting the polarization state of the reflected light reflected by the recording unit, and based on the detection result of the reflected light detection means, the predetermined tilt angle and / or the predetermined azimuth angle By specifying the information, the information recording and / or reproducing apparatus reads multi-value information recorded in the recording unit.

  According to an eighteenth aspect of the present invention, in the information recording and / or reproducing apparatus according to the seventeenth aspect of the invention, the polarization state of the reading light is circularly polarized light, and the polarization state of the reflected light is elliptically polarized light.

  According to a nineteenth aspect of the present invention, in the information recording and / or reproducing apparatus according to the seventeenth or eighteenth aspect of the invention, the reading light includes the first reading light whose polarization state is right circular polarization, and the polarization state which is left. The second reading light is circularly polarized light, and the first reading light and the second reading light are irradiated so as to form a predetermined half space.

  According to the present invention, an information recording medium for recording multi-value information with a simple configuration having a geometric shape in a recording unit, an information reproducing method, an information recording method, an information recording and / or an information recording medium corresponding to such an information recording medium. Alternatively, a playback device can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In the recording portion of the information recording medium according to the present invention, the inclined reflecting surface having a predetermined area and having a predetermined inclination angle is formed so as to form a plurality of types of azimuth angles corresponding to the multi-value information. Or, in the recording portion of the information recording medium according to the present invention, the inclined reflection surface having a predetermined area and having a predetermined azimuth angle is formed so as to form a plurality of types of inclination angles corresponding to the multi-value information. . Or, in the recording part of the information recording medium according to the present invention, the inclined reflection surface having a predetermined area is combined so as to form a plurality of types of inclination angles and a plurality of types of azimuth angles corresponding to the multi-value information. Is formed.

  Alternatively, the recording portion of the information recording medium according to the present invention is formed with one or a plurality of inclined reflecting surfaces having a predetermined area and a predetermined azimuth angle. Alternatively, the information recording medium according to the present invention is made of a material having one or a plurality of inclined reflection surfaces having a predetermined inclination angle and having a predetermined region, and optical anisotropy is added on the inclined reflection surface. It has a recording layer.

  The inclined reflecting surface formed in the recording portion of the information recording medium according to the present invention is irradiated with polarized light having a known controlled bias (for example, right circularly polarized light) from above, and the polarization state of the reflected light (for example, elliptical) The multi-value information recorded in the recording unit can be read by detecting (polarized light) and specifying a predetermined tilt angle and / or a predetermined azimuth angle based on the detection result.

  The present invention is based on the well-known universal physical phenomenon of reflection on the surface of polarized material. That is, for example, in the case of circularly polarized light incidence, by detecting the ellipticity of the elliptically polarized light reflected by the reflecting surface and the azimuth angle of the ellipse, the incident angle and the azimuth of the incident surface defined by the geometric shape of the reflecting surface are detected. Focused on the ability to determine the corner. In principle, the method uses the change in the polarization state as compared with the method using the change in reflectance of the prior art, and thus has many features.

  The first feature of the present invention is high detection sensitivity. In the prior art, since the recording part (low reflectance dark part) is provided in the unrecorded part (high reflectance bright part) on the surface of the information recording medium, the detection is simple light intensity detection, and the detection optical system In the visual field, the dark part signal is detected in the bright field formed by the bright background. On the other hand, in the present invention, a filter (for example, a linear analyzer in FIG. 22 described later) for separating the polarization state is inserted before the final light intensity detection. In the irradiating unit, right or left circularly polarized light is incident on the surface of the information recording medium, and the specularly reflected light is converted into elliptically polarized light having a predetermined azimuth by a reflecting surface provided in a predetermined shape on the surface of the information recording medium. In this case, as is well known, other than the reflected light of the recording part, that is, the regular reflected light from the plane of the information recording medium non-recording part is left or right circularly polarized light whose polarization state is orthogonal to the incident circularly polarized light. Thus, the polarization state from the recording unit is different.

  Therefore, the detection unit can efficiently separate the signal components and relatively reduce the signal level from the unrecorded portion. In the field of view of the detection optical system, since the recording part (bright part) is provided in the unrecorded part (dark part) of the information recording medium surface, the detection is a bright part signal detection in the dark part, and the S / N of the detection is remarkably high. improves. Further, the reflected signal of the unrecorded portion is a left (right) circular polarization component that is extinguished by the right (left) circular polarizer that generates incident right (left) circularly polarized light so that the polarization state is orthogonal, Since it can be used as a reference signal for the playback position and playback state on the surface of the recording medium, the detection unit can be used as an event signal that guarantees that the playback position and playback state are in the specified playback position, signal amplification system gain signal, and tracking signal. it can. That is, even if the reflection intensity of the recording unit varies depending on the surface condition, the reproduction position, etc., it is possible to ensure that stable signal reproduction is performed by automatically adjusting the gain, so that high detection sensitivity can be maintained as an overall characteristic.

  The second feature of the present invention is that it is resistant to disturbance. In the present invention, in principle, for example, circularly polarized light is irradiated to detect the polarization state of reflected light from a recording unit having a predetermined tilt angle and azimuth angle. The change in the polarization state due to reflection is a phenomenon that occurs due to reflection on the slope of the recording unit, and is a function of the incident angle. Therefore, as long as the incident angle does not change, the polarization state does not change due to disturbances such as parallel movement of the reflecting surface before and after, left and right. This means that it is insensitive to parallel movement in a three-dimensional direction. For example, in an information recording and / or reproducing apparatus corresponding to an information recording medium such as a DVD, a defocus margin and a detrack margin are wide. Means.

  Further, except for the reflection phenomenon at the recording unit, the polarization state does not change during the propagation of light. Both the incident polarized light and the reflected outgoing polarized light pass through a uniform medium such as air or a protective film, so that the polarization state of light does not change during propagation. Therefore, regardless of the operating environment, for example, in the case of register applications, road sign reflectors and in-vehicle readers, the distance variation (mm, m, km, etc.) between the information recording medium and the detector head of the device is significant. There is a major feature that it is not affected by (distance change). Here, the operating environment is an operating environment including fluctuations of an electric field and a magnetic field, or an environmental medium such as a gas, a liquid, and a solid in addition to a temperature, a humidity, and a pressure.

  The third feature of the present invention is that the working distance (WD) is long. The information reproducing method according to the present invention is, in principle, a detection optical system using specularly reflected light on a flat slope, so-called zero-order diffracted light, and the numerical aperture (NA) of the detection optical system is optical according to the prior art. It can be set smaller than the system. Therefore, since the distance between the information recording medium and the detection unit head can be increased, the practicality can be greatly improved.

  The fourth feature of the present invention is high fusion with magneto-optical recording. In the present invention, since the change in the polarization state due to reflection is used, both recording and reading by magneto-optical recording have high fusion and applicability. That is, in conventional magneto-optical recording, recording and reading are performed using the magneto-optical anisotropy of the magnetic recording medium. In the present invention, the geometric shape of the surface of the information recording medium is independent of the recording and reading. The optical anisotropy is caused by the change of. Since the magneto-optical anisotropy and the geometric anisotropy according to the configuration of the present invention are completely independent of each other and can be controlled independently, for example, recording with a fusion of geometric shape and magnetic anisotropy A reading method can be configured. Further, for example, the geometric anisotropy according to the present invention is added to an information recording medium for magneto-optical recording, and a constant bias due to the geometric anisotropy is given to the polarization state, so that the optical recording is comprehensively performed. It is expected to realize a configuration for improving the detection S / N of magnetic recording.

  The fifth feature of the present invention is sensitization of the optical anisotropy of the reflecting surface. In the oblique reflection of light which is an embodiment of the present invention, the anisotropy of reflection when the reflecting surface is made of an isotropic homogeneous material is used. In oblique reflection, when the reflection surface has a slight optical anisotropy, reflection characteristics sensitive to the optical anisotropy can be configured by selecting the incident angle and the polarization state of the incident polarized light. Therefore, for example, by constructing the reflective slope according to the present invention with a material having optical anisotropy such as liquid crystal, it is possible to use oblique reflection that cannot be constituted by reflection by normal incidence on a surface having optical anisotropy. It can also be expected to construct a recording and reading system.

  The principle of the present invention will be described. Light (generally electromagnetic waves) has a “bias” property as its basic characteristic. On the other hand, in the reflection of light on the material surface, since the amplitude and phase of light generally change, the reflection characteristic can be described by complex amplitude reflectance. Taking into account the light bias, the complex amplitude reflectivity is the p component, which is the component of the bias in the incident surface (defined by the surface including the normal of the incident light ray and the reflecting surface), and perpendicular to the incident surface (on the surface). It takes different values for the s component.

When the complex amplitude reflectivity of the p component of incident light is denoted by r _p and the complex amplitude reflectivity r _s of the s component is written, when polarized light, which is polarized light, is reflected on the material surface, the electric vector of the light Since the changes in amplitude and phase are different between the p component and the s component, the polarization state changes in the reflected light. The standard of change is in the plane of incidence. This change in polarization state is a monotonous function with respect to the incident angle, as will be described later. In the present invention, an information recording medium corresponding to multi-value information, an information reproducing method, and the like are realized by utilizing a difference in polarization state of reflected light, in particular, an inclination angle and / or an azimuth angle of elliptically polarized light.

  The inclined reflecting surface formed on the recording portion of the information recording medium according to the present invention will be specifically described. FIG. 1 is a diagram exemplifying elliptically polarized light that is reflected when circularly polarized light is irradiated onto a V-groove constituted by a slope inclined by 45 °. In FIG. 1, 1 is a circularly polarized incident light irradiated to the recording unit, 2a and 2b are V grooves formed in the recording unit, 3a and 3b are incident surfaces, and 4a and 4b are reflected by the V grooves 2a and 2b. Elliptical polarizations 5a and 5b are the main axes of the ellipse. Here, the incident surface refers to a surface including incident light and the normal line of the reflecting surface. FIG. 1A and FIG. 1B are views of V-grooves 2a and 2b formed in the recording portion when viewed from an oblique direction, and the V-grooves 2a and 2b are information recording media on which no recording portion is formed. It is composed of an inclined surface having an inclination angle of 45 ° with respect to a plane (reference surface of the inclination angle). Further, the arrows schematically show how incident light 1 is reflected by the V grooves 2a and 2b. 1A and 1B, the V-groove 2a and the V-groove 2b have different azimuth angles. The azimuth angle reference will be described later in the description of FIG. FIG. 1C shows the elliptically polarized light 4a reflected by the V-groove 2a of FIG. 1A viewed from the direction perpendicular to the surface of the information recording medium where no recording portion is formed (a method in which reflected light travels). FIG. 1 (d) shows the elliptically polarized light 4b reflected by the V-groove 2b of FIG. 1 (b) from a direction perpendicular to the surface of the information recording medium where the recording portion is not formed (a method in which reflected light travels). FIG.

  As shown in FIG. 1, the recording portion is reflected in a configuration in which the V-groove 2a (2b) is configured by an inclined surface (inclined reflecting surface) having an inclination angle of 45 ° and is reflected vertically by two reflections. In the elliptically polarized light 4a (4b), the inclination of the principal axis 5a (5b) of the ellipse changes depending on the azimuth angle of the V groove 2a (2b) on the information recording medium surface. The azimuth angle of the ellipse main axis 5a (5b) is in a 1: 1 proportional relationship with the azimuth angle of the V groove 2a (2b). For example, an Al layer is formed on the surface of the V groove 2a (2b) to In the standard configuration in which the surface of the recording medium is covered with a transparent protective layer, as shown in FIG. 1, the azimuth angle of the ellipse main axis 5a (5b) is always 48 ° left from the azimuth angle of the V-groove 2a (2b). Rotate to.

The rotation of the elliptical principal axis 5a (5b) of the elliptically polarized light 4a (4b) that is the reflected light occurs as a result of two reflections on the Al surface of the circularly polarized light that is the incident light 1. In the case of circularly polarized light incidence, the azimuth angle and ellipticity angle of the reflected elliptically polarized light 4a (4b) have a simple linear relationship with the azimuth angle of the incident surface 3a (3b) and the incident angle of circularly polarized light. Therefore, the change in the azimuth angle and the incident angle of the inclined reflecting surface on the surface of the information recording medium can be read as the change in the polarization state (the major axis orientation and ellipticity of the ellipse). The ellipticity angle is tan ⁻¹ (B / A) when the major axis length of the ellipse is A and the minor axis length is B. In the present application, the ellipticity angle is taken into consideration in the polarization direction, and a positive ellipticity angle indicates clockwise polarization, and a negative ellipticity angle indicates counterclockwise polarization.

  FIG. 2 is a diagram showing an example of forming a recording portion having an inclined surface formed on the information recording medium according to the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. The recording portion having the inclined surface shown in FIGS. 2A to 2C is a portion corresponding to one pit in the case of a CD, for example. In FIG. 2A to FIG. 2C, the arrows schematically show how incident light 1 is reflected by a recording unit having an inclined reflection surface. FIG. 2A shows an example of forming an inclined surface constituting a part of a triangular pyramid (hereinafter referred to as a triangular pyramid) when the number of reflections of light on the information recording medium is three. In FIG. 2A, 6 is a triangular pyramid for three reflections. The triangular pyramid 6 is a corner cube having a tilt angle of 45 ° with respect to the plane of the information recording medium on which the recording portion is not formed. The ridge line of the corner cube represents a predetermined direction. It is formed so as to form a plurality of types of azimuth angles corresponding to the multi-value information. The corner cube is a combination of three inclined reflecting surfaces at an angle of 90 °, and the reflected light travels back to the incident light by reflecting the incident light once at each inclined reflecting surface (reciprocating optical path). ).

  FIG. 2B is an example of forming an inclined surface constituting the V groove when the number of reflections of light on the information recording medium is two. In FIG. 2B, a V-groove 2b is a V-groove having an inclination angle of 45 ° with respect to the plane of the information recording medium on which the recording portion is not formed. A ridge line 2b (longitudinal direction of the inclined reflecting surface) represents a predetermined azimuth, and is formed so as to form a plurality of types of azimuth angles corresponding to multi-value information. FIG. 2C shows an example of forming an inclined surface when the number of reflections of light on the information recording medium is one. In FIG.2 (c), 7 is a slope for 1 time reflection. The inclined surface 7 is, for example, an inclined reflecting surface with an inclination angle of 30 ° with respect to the information recording medium plane on which no recording portion is formed, and the longitudinal direction of the inclined reflecting surface represents a predetermined direction, and is multi-valued. A plurality of kinds of azimuth angles are formed corresponding to information. Actually, a recording unit having an inclined reflecting surface as illustrated in FIGS. 2A to 2C has a plurality of types of inclination angles and / or a plurality of types of azimuth angles corresponding to multi-value information. For example, like a pit of a CD, it is formed in, for example, a concentric circle shape, a spiral shape, a straight line shape, etc. at a predetermined interval and a predetermined track pitch.

  When the circularly polarized incident light 1 is irradiated onto the recording unit having the inclined surface shown in FIGS. 2A to 2C, the reflected light has an amplitude reflectance ratio angle Ψ and a phase difference between p-polarized light and s-polarized light. Since Δ changes, the polarization state changes. In addition, in the example of forming the inclined surface when the number of reflections shown in FIG. 2C is one, it is necessary to make one of the incident light 1 and the reflected light obliquely incident. In addition, the optical path of the incident light 1 and the optical path of the reflected light are spatially separated so as to be reflected obliquely by the recording unit. FIG. 2C shows a configuration in which the incident light 1 that is the irradiation light is obliquely incident and the optical axis of the reflected light that is the detection light is perpendicular to the surface of the information recording medium.

  In the case of detecting the light reflected back by the recording unit, it is necessary to configure it by two or three reflections as shown in FIG. 2 (a) or 2 (b). In this case, the reflection can be a reflection of a metal surface used in the prior art. Furthermore, in the present invention, a simple information recording medium configuration using the total reflection of the transparent substance can be used.

  FIG. 1 and FIG. 2 are examples in which the inclined reflecting surface having a predetermined area and having a predetermined inclination angle is formed so as to form a plurality of types of azimuth angles corresponding to the multi-value information. In the recording section of the information recording medium according to the present invention, the inclined reflection surface having a predetermined area and having a predetermined azimuth angle may be formed so as to form a plurality of types of inclination angles corresponding to the multi-value information. Or the inclined reflective surface which has a predetermined area | region may be combined and formed so that several types of inclination angles and several types of azimuth angles may be made | formed corresponding to multi-value information.

  For example, if the information recording medium is rotated and read out as in the case of a DVD playback device, when the recording unit has information recorded by providing a plurality of types of azimuth angles with a constant inclination angle, The length of each recording unit in the track direction is made constant. Further, in the case where a recording unit in which information is recorded by providing a plurality of inclination angles is provided, the length in the track direction may be variable. In this case, in the method of rotating and reading the information recording medium as in the DVD reproducing apparatus, the time interval (frequency) of the signal is fixed in the configuration in which the length in the track direction is constant, so that the lock-in In a configuration in which a signal processing system that improves S / N, such as detection, can be used and the length in the track direction is variable, the polarization state is detected by reading a plurality of polarization states and determining the signal intensity ratio between channels. be able to.

  The information recording medium on which the recording portion having the inclined reflection surface shown in FIG. 2 is formed, for example, the inclined reflection surface (for example, V-groove or corner cube) formed on the information recording medium is formed by inverting the unevenness. Thus, a master stamper can be manufactured and, as is well known, a large amount can be manufactured by transferring and replicating the stamper by injection molding. Furthermore, a metal film such as Al is formed on the transferred information recording medium as needed.

  In order to produce a master stamper, first, for example, an inclined reflecting surface (unevenness is not reversed) is formed on glass or the like. Formation of the inclined reflecting surface on glass or the like can be realized by, for example, FIB (Focused Ion Beam) processing. As is well known, FIB (Focused Ion Beam) processing is a processing method that uses a finely focused Ga (gallium) ion beam, and a complicated shape can be produced with submicron level accuracy. In addition, the inclined reflecting surface is formed on the glass or the like, for example, on a glass or the like (or after a metal thin film is formed on the glass or the like by a sputtering method or the like), and a tip of a prism type (V groove) or a triangle having a tip of 45 ° in advance. You may produce by pressing the diamond processed into the cone etc. with a suitable pressure. A well-known nanoimprint technique can also be used.

  Next, for example, nickel or the like is formed into a thickness on the order of several millimeters on the glass on which the inclined reflection surface is formed by, for example, a sputtering method or an electroless plating method. A stamper as a master is manufactured by peeling the deposited nickel or the like from glass or the like.

  In addition, in an information recording medium manufactured by injection molding using a stamper, for example, there is a possibility that partial roundness or a flat surface may be formed at a corner of an inclined reflecting surface such as a V groove or a corner cube. However, if the reflecting surface is formed, the partial deformation at the edge of the reflecting surface does not greatly affect the reading of recorded information. Therefore, in the present specification, claims, and drawings, the term “V-groove”, “corner cube”, etc., including those having partial deformation at the edge of the reflecting surface.

  Hereinafter, the principle of reflection of polarized light used for recording and reproduction will be described in detail with reference to the drawings, taking the single reflection shown in FIG. 2C as an example. In the two-time or three-time reflection shown in FIG. 2A or 2B, the characteristic of the one-time reflection is superimposed a predetermined number of times. The principle described below is valid for electromagnetic waves of all wavelengths. The light used may be a wavelength used for any of CD, DVD, and BD (Blu-ray Disc), and may be another wavelength. Furthermore, white light in which these lights are mixed may be used.

  In general, the change in the polarization state of reflection due to oblique incidence can be formulated as follows according to the complex refractive index of the substance. Below, first, the relationship between the polarization state observed and the ratio (Formula 1) of the ps component of the complex amplitude reflectance at a certain reflection point on the inclined surface on the information recording medium is shown.

複素変数ρは、周知の偏光解析法（エリプソメトリー）のパラメータであり、実際に計測される実変数Ψ、Δは複素変数ρの極座標表示に相当する。ｚ方向に進行する光の偏光状態を、光の電気ベクトルの水平成分Ｅ_ｘと垂直成分Ｅ_ｙを成分とするジョーンズベクトル、式（数２）で表現し、ジョーンズ計算を用いて偏光状態の変化を説明する。入射偏光は式（数３）に示す右回りの円偏光とする。

The complex variable ρ is a well-known ellipsometric parameter, and the actual variables Ψ and Δ actually measured correspond to polar coordinate display of the complex variable ρ. The polarization state of the light traveling in the z direction is expressed by the Jones vector, which is composed of the horizontal component E _x and the vertical component E _y of the light electric vector, and the change in the polarization state using the Jones calculation. Will be explained. The incident polarized light is clockwise circularly polarized light represented by the formula (Equation 3).

まず、情報記録媒体の記録部が情報記録媒体上で成す傾斜面の方位角が変化した時、傾
斜面での１回の鏡面反射によって情報記録媒体表面に垂直な読み取り光学系へ反射される
光の偏光状態がどのように変化するかを考える。図３は、入射面の方位角θでの入射光と
反射光とを模式的に示す図であり、ｘ−ｙ平面内の動径方向に入射角φが０°〜９０°ま
で変化した状態を示している。図３において、ｚ軸は読み取り光軸の方向であり、ｘ軸は
記録部が連続的に形成される方向、ｙ軸はｘ軸及びｚ軸と垂直な方向である。例えば、ＤＶＤのように記録部が同心円状又は螺旋状に形成されていれば、ｘ軸は記録部の連続する方向（トラック方向）に対する接線方向であり、記録部が直線状に形成されていれば、ｘ軸は記録部の連続する方向（前記直線の方向）である。また、予め基準方位を示す記録部が設けられている情報記録媒体の場合には、ｘ軸は基準方位を示す記録部の方向である。このように、記録部の方位角の基準方位は、ｘ軸方向である。

First, when the azimuth angle of the inclined surface formed on the information recording medium by the recording unit of the information recording medium changes, the light reflected to the reading optical system perpendicular to the information recording medium surface by a single mirror reflection on the inclined surface Consider how the state of polarization changes. FIG. 3 is a diagram schematically showing incident light and reflected light at an azimuth angle θ of the incident surface, where the incident angle φ changes from 0 ° to 90 ° in the radial direction in the xy plane. Is shown. In FIG. 3, the z-axis is the direction of the reading optical axis, the x-axis is the direction in which the recording unit is continuously formed, and the y-axis is the direction perpendicular to the x-axis and the z-axis. For example, if the recording part is formed concentrically or spirally like a DVD, the x-axis is a tangential direction with respect to the continuous direction of the recording part (track direction), and the recording part is not formed linearly. For example, the x-axis is the direction in which the recording unit continues (the direction of the straight line). In the case of an information recording medium in which a recording unit indicating a reference azimuth is provided in advance, the x axis is the direction of the recording unit indicating the reference azimuth. Thus, the reference azimuth of the azimuth angle of the recording unit is the x-axis direction.

  As shown in FIG. 3, when the reading optical axis is fixed as the z-axis direction, light rays that are incident on the inclined surface of the recording unit and reflected in the z direction are the surfaces formed by the normal lines of the respective inclined surfaces and the reflected light rays. It is in the incident plane defined. At this time, the incident surface includes the z axis and is perpendicular to the xy plane. Further, from the law of reflection in specular reflection, the incident light ray is in the incident surface, and the incident angle is equal to the reflection angle. Therefore, when the angle formed with the x axis of the incident surface is defined as the azimuth angle θ, the azimuth angle θ is equal to the angle formed by the projection component of the normal of the inclined surface onto the xy plane with the x axis. As shown in FIG. 3, when an xz plane having an azimuth angle θ = 0 is taken as one of the incident surfaces and the incident angle φ is taken in the radial direction, the incident angle φ changes from 0 ° to 90 °. At that time, the incident light beam is incident on each inclined surface at an angle shown by a thick line in FIG.

  FIG. 4 is a diagram exemplifying a change in the polarization state of the reflected light reflected from the incident surface of various azimuth angles θ from the Al reflecting surface depending on the incident angle φ. The “left” in the center of FIG. 4 indicates that left circularly polarized light is reflected, and the “right” in the periphery indicates that right circularly polarized light is reflected. As in the prior art, if the Al surface is covered with a transparent protective film, the polarization state changes at each incident angle φ at the azimuth angle θ = 0 as shown on the x-axis in FIG. FIG. 4 shows a case where the angle θ formed by the normal of the inclined surface changes from the reference azimuth x-axis (0 °) to 150 ° every 30 ° in the information recording medium surface. These polarization changes can be calculated as follows:

で表される。ここで、

It is represented by here,

は、座標系の回転に伴う角度θの旋光子行列、

Is the optical rotator matrix of angle θ as the coordinate system rotates,

は、偏光状態の記述の基準方位をx方向として、入射面がｘ方向を向いた傾斜面での入射角φ_１における偏光の反射を表すジョーンズ行列である。ここで、ρ_１は

Is a Jones matrix that represents the reflection of polarized light at an incident angle φ _{1 on} an inclined surface with the incident surface oriented in the x direction, where the reference direction of the description of the polarization state is the x direction. Where ρ ₁ is

と書ける。円偏光は、Ｔ_−θで変化しないから

Can be written. Circularly polarized light does not change with T- _θ

となる。式（数８）は、右辺のジョーンズベクトルで表わされる楕円偏光が、回転行列Ｔ_ーθ１で回転されることを示し、楕円の主軸の傾きが方位角−θ_１だけ回転される。反射された楕円は、エリプソメトリーの手法でその形を容易に決定できる。通常のエリプソメトリー技術では、楕円の方位角θの計測精度は、０．０１°から０．００１°である。

It becomes. Equation (8) is elliptical polarization represented by the right-hand side of the Jones vector, indicates that it is rotated by the rotation matrix T _{over .theta.1,} the inclination of the major axis of the ellipse is rotated by the azimuth angle - [theta] _1. The shape of the reflected ellipse can be easily determined by ellipsometry techniques. In the normal ellipsometry technique, the measurement accuracy of the azimuth angle θ of the ellipse is 0.01 ° to 0.001 °.

  The ellipse shape that changes depending on the complex refractive index of the reflecting surface on the right side of Equation (Equation 8) is the Jones vector.

で記述され、反射面の材質が決まれば、式（数７）によるρ_１として次に述べるように特性を計算できる。反射偏光の入射角依存性を決めるρ_１は、式（数７）のフレネル振幅反射係数の比で記述できて、透明体でも吸収体でもバルク物質の場合は共通の式で

If the material of the reflecting surface is determined, the characteristic can be calculated as ρ ₁ by the equation (Equation 7) as described below. Ρ ₁ that determines the incident angle dependency of the reflected polarized light can be described by the ratio of the Fresnel amplitude reflection coefficient in the equation (Equation 7), and is a common equation in the case of a transparent material, an absorber, and a bulk material.

と書ける。但し、φ′は複素屈折角であり、スネルの法則

Can be written. Where φ 'is the complex refraction angle and Snell's law

でバルク物質の複素屈折率Ｎ＝ｎ−ｉｋの関数である。また、ｎ_ａは媒質の屈折率で、情報記録媒体の透明樹脂保護膜では、１．５８程度である。一般に、媒質は透明で屈折率は実数であり、入射角も実数だから、スネルの法則の左辺は実数である。従って、右辺も実数となる必要があり、傾斜面が金属反射面などの吸収のある物質で構成されている場合は、屈折角も複素数となる。式（数１０）の関数は、以下の計算例に示すように、入射角に対して単純な関数であり、物質ごとに容易に校正曲線を得ることができる。

The function of the complex refractive index N = n−ik of the bulk material. Further, the n _a refractive index of the medium, the transparent resin protective layer of an information recording medium, is about 1.58. In general, since the medium is transparent, the refractive index is a real number, and the incident angle is also a real number, the left side of Snell's law is a real number. Therefore, the right side also needs to be a real number, and when the inclined surface is made of an absorbing material such as a metal reflecting surface, the refraction angle is also a complex number. As shown in the following calculation example, the function of the formula (Equation 10) is a simple function with respect to the incident angle, and a calibration curve can be easily obtained for each substance.

FIG. 5 is a diagram showing the incident angle dependence of the intensity reflectance of the ps component of the Al reflecting surface. 5, the intensity reflectance for _{r p} is p component, _{r s} is the intensity reflectance for the s component, 405 nm wavelength of the incident light, the complex refractive index of the Al reflecting surfaces N = n-ik = 0.6 Calculated as -5.04i. Intensity reflectance r _p and r _s are kept together 75% higher than the value, incident angle dependence is small. However, as explained below, the polarization state of the reflected light varies greatly with the incident angle.
FIG. 6 is a diagram illustrating the incident angle dependence of the complex amplitude reflectance ratio of the p-s component on the Al surface in a complex plane display. In FIG. 6, Re is a real axis, Im is an imaginary axis, and the complex amplitude reflectance ratio ρ (= r _p / r _s ) is the same as in FIG. The refractive index is calculated as N = n−ik = 0.6−5.04i. As shown in FIG. 6, when the incident angle φ increases from 0 ° to 90 ° (= π / 2), ρ changes monotonically from −1 to 1 on the complex plane. This property utilized by the present invention is a property common to all substances. That is,
I. The complex amplitude reflectivity ratio ρ is −1 at an incident angle φ = 0 and 1 at φ = π / 2.
II. When the incident angle φ changes from 0 to π / 2, ρ changes monotonically from −1 to 1 on the complex plane, and the real part of ρ is 0 along the imaginary axis (Δ = ± π / 2). Be sure to pass through.

  For example, in a transparent body to be described later, ρ is always a real number and monotonously changes on the real axis from −1 to 1. In the example of the Al reflecting surface, both the p-polarized light and the s-polarized light maintain high reflectivity, as assumed from the change in intensity reflectivity in FIG. 6, so that Ψ representing the amplitude reflectivity ratio angle is approximately 40 °. Constant between 45 °. On the metal surface, as shown in FIG. 6, on the complex plane, it may be considered to move from left to right on a semicircle having a radius of about 1.

  When the inclined surface of Al shown in FIG. 6 is irradiated with right circularly polarized light, the polarization state changes from left circularly polarized light to right circularly polarized light, respectively. Further, while the incident angle changes from 79 ° to 80 °, it passes through the main incident angle where the real part of ρ is 0. At the main incident angle, the reflected light is linearly polarized light. In terms of the ellipticity angle of an ellipse, it increases monotonically from −45 ° to + 45 ° due to a change in incident angle. The negative ellipticity angle indicates counterclockwise polarization, and the positive indicates clockwise polarization. The monotonic change can be easily understood by displaying ρ in polar coordinate format.

  FIG. 7 is a diagram showing the incident angle dependence of the reflected polarization parameter of the Al reflecting surface, and the incident angle dependence of FIG. 6 is shown by Ψ and Δ. In FIG. 7, Ψ and Δ are reflection polarization parameters, and the wavelength of incident light is 405 nm, and the complex refractive index of the Al reflecting surface is N = n−ik = 0.6−5, as in FIGS. 5 and 6. .04i. Due to the common property of materials that the s-polarized reflectivity is higher than the p-polarized reflectivity, the maximum value of Ψ may be considered to be 45 °. As shown in FIG. 7, in general, in a metal body or the like having a large absorption, there is a large change in Δ from 180 ° (corresponding to −1 on the complex plane) to 0 ° (corresponding to +1 on the complex plane). Occur. When right circularly polarized light is incident, the polarized light reflected by a metal surface such as Al is generally elliptically polarized light. At this time, the principal axis of the elliptically polarized light is tilted from the incident plane by an azimuth angle equal to Ψ. In the example shown in the figure, the inclination is always approximately 45 °, and the halfway ellipse and linearly polarized light are uniformly inclined by 45 ° as shown in FIG. 4 (even if the circle is inclined).

In the calculation of elliptically polarized light in FIG. 4, it is assumed that the reflection is twice on the Al reflecting surface. In double reflection, the change in polarization state due to reflection is ρ ² = tan ² Ψ · exp (i2Δ), and the change in ellipticity angle is doubled. FIG. 8 is a diagram illustrating a phase change due to twice reflection at the same incident angle on the Al surface. FIG. 8A shows changes in Δ with respect to the incident angle, and FIG. 8B shows changes in Ψ and Δ with respect to the incident angle. As shown in FIG. 8 (a), the ellipticity angle of the polarization ellipse of the reflected light is 312 ° due to twice reflection at an incident angle of 45 °, and the polarization ellipse is an ellipse of −48 ° as shown in FIG. It becomes.

  Next, consider the numerical aperture of the irradiation optical system. Here, it is assumed that the converging light is collected from the irradiation optical system onto the recording unit, assuming a two-way reflection optical path arrangement by the configuration of the present invention. In this case, when the incident angle of the first surface is reduced, the incident angle of the second surface is increased, and the effect of canceling the incident angle change in a complementary manner is produced. Specifically, by reflection twice,

となる。

It becomes.

  FIG. 9 is a diagram illustrating the change of the polarization state due to the deflection angle due to twice reflection on the Al reflecting surface having an apex angle of 90 °. In FIG. 9, a deflection angle of 0 ° indicates the optical axis of circularly polarized light. Further, the right scale indicates ψ, the left scale indicates Δ, and the shaded portion indicates a range of Ψ = 39.5 ± 0.5 °. As shown in FIG. 9, Ψ falls within the range of 39.5 ± 0.5 ° indicated by the hatched portion in the range of the deflection angle of ± 36 °. In addition, when the light is incident on the Al reflecting surface whose apex angle shown in FIG. 1 of the present invention is fixed at 90 °, when the convergence angle of the convergent light irradiated to the first surface is taken around the optical axis, the Al surface The sum of the incident angles of the two-time reflection becomes 90 °, and the reflection polarization characteristic changes symmetrically about the optical axis. Similar angle compensation occurs in a three-reflection configuration.

  One embodiment of the present invention is multi-value recording in which the change in the inclination angle (azimuth angle) θ of the main axis of the ellipse is multi-value information. Here, in the configuration of the present invention, the offset value of the inclination of the main axis changes with Ψ, and Δ gives a variation in the ellipticity angle. Therefore, as shown in FIG. 9, Ψ = 39.5 ° ± 0.5 ° in the range where the convergence angle of the luminous flux is ± 36 °, and the fluctuation of the inclination angle (azimuth angle) θ of the main axis of the ellipse is 1 Enter within °. This variation in Δ in the convergence angle range varies the ellipticity angle, but does not constitute an error in the azimuth angle θ used for data recording. In other words, the configuration of the present invention essentially uses the incident angle dependence of the reflection of polarized light, but the change due to the incident angle spread of the irradiated light is compensated by the configuration of the round-trip optical path, and is defined by the apex angle of the reflecting surface. Constant value. From this characteristic, sufficiently uniform reflected polarized light can be obtained even with NA = 0.6 (convergence angle ± 36.9 °) corresponding to the converging optical system used for DVD.

  Equations (10) and (11) describe the case where the surface of the information recording medium can be regarded as a bulk. In the method according to the present invention, when the surface of the information recording medium is different from the bulk, for example, the surface is covered with an optically isotropic oxide film, an optically anisotropic magnetic thin film, a liquid crystal thin film, or the like. It is also effective in some cases. In this case, the reflecting surface may be optically modeled to calculate the complex variable ρ, and associated with the observed change in polarization state. The methodology used in conventional ellipsometry can be used as is for this analytical calculation part. In other words, as long as the reflected light can be measured and the change in the polarization state can be measured, an ellipsometry technique may be introduced as to how to use the measurement value and what kind of information to extract.

  In the explanation so far, the explanation has been focused on the case where circularly polarized light is used as the polarization state of the incident light for reading. However, in principle, if the polarization state of the irradiation light (reading light) is known, For example, elliptical polarized light or linearly polarized light may be used as irradiation light. Moreover, the axially symmetric polarized beam (Axisymmetrically polarized beam, Yuichi Ozawa, Shunichi Sato, Optics 35 No. 12 (2006) pp. 9-18) that has been reported recently can also be used as irradiation light. Furthermore, non-polarized light having no bias can be used as irradiation light. In the case of non-polarized illumination, the change in polarization state due to reflection is more generalized, and reflection including scattering can also be handled.

  The theoretical treatment depends on the Stokes parameter and Mueller matrix that can describe non-polarized light and partially polarized light, as shown below. The equation corresponding to the above equation (Equation 4) is obtained by using a standardized Stokes parameter in which the intensity is normalized to 1 in Mueller calculation.

となる。ここで座標系の回転に伴う角度θの旋光子行列は

It becomes. Where the optical rotator matrix of angle θ with the rotation of the coordinate system is

入射面が水平な鉛直試料面での入射角φ_１における偏光の反射を表すミューラー行列は

The Mueller matrix representing the reflection of polarized light at the incident angle φ ₁ on the vertical sample surface where the incident surface is horizontal is

これらを式（数１３）に代入して

Substituting these into the equation (Equation 13)

となる。すなわち、入射面の傾きθ_１による変化は、ポアンカレ球上でＳ_３を回転軸としてＳ_１、Ｓ_２座標をθ_１回転するだけで、楕円率角の変化は伴わない。非偏光を入射した場合は、入射ストークスパラメーターを非偏光に置きなおして、

It becomes. That is, the change due to the inclination θ ₁ of the incident surface is merely a rotation of the S ₁ and S ₂ coordinates by θ ₁ around S ₃ on the Poincare sphere, and the ellipticity angle is not changed. If unpolarized light is incident, change the incident Stokes parameter back to unpolarized,

となる。非偏光入射では、反射の位相角の情報は失われるが、ｐ−ｓ成分の強度反射率の変化を示すΨ_１が４５°に等しい場合以外はθ_１を計測できる。θ_１の計測精度は、Ψ_１が４５°から小さくなれば上がるため、反射面は金属による反射に代えて、消衰係数ｋが小さく、ｐ−ｓ成分の反射振幅比角Ψが小さい誘電体などを用いることになる。

It becomes. With non-polarized incidence, information on the phase angle of reflection is lost, but θ ₁ can be measured except when Ψ ₁ indicating a change in intensity reflectance of the ps component is equal to 45 °. Since the measurement accuracy of θ ₁ increases as Ψ ₁ decreases from 45 °, the reflective surface is a dielectric having a small extinction coefficient k and a small reflection amplitude ratio angle Ψ of the p-s component instead of reflection by metal. Etc. will be used.

  As already described, even when the recording surface is transparent, the reflection law of FIG. 1 is established. In addition, in the grazing incidence with the incident angle φ = 90 °, the polarization state of the incident light is not changed by reflection. Further, at the vertical incidence of φ = 0 °, the traveling direction of light is reversed by reflection, so that the rotation direction of polarized light is reversed, and the clockwise circular polarized light becomes counterclockwise circular polarized light. Since these properties are caused by the geometric properties of the space, they can be established for both transparent bodies and absorbers and do not depend on the sample material.

  The incident angle dependence of the polarization state moves from -1 to 1 on the real axis in the complex plane display of FIG. 6 when the sample is transparent. FIG. 10 is a diagram exemplifying a change due to the incident angle of the polarization state in the case of oblique reflection on the dielectric surface. For example, on a Si reflecting surface having a small extinction coefficient k, the change corresponding to FIG. 10, the azimuth angle of the principal axis of the ellipse is always perpendicular to the incident surface. However, the principle of measuring the azimuth angle of the recording unit is the same. Corresponding to the case of Al taken as an example of the metal surface, the optical characteristics will be described with reference to the drawings by taking Si having a relatively high reflectance as an example of the dielectric surface. In the calculation, a protective film was added with a complex refractive index N = n−ik of Si having a wavelength of 405 nm of 5.42−0.25i.

FIG. 11 is a diagram illustrating the incident angle dependence of the intensity reflectance of the p-s component on the Si surface. 11, the intensity reflectance for _{r p} is p component, _{r s} is the intensity reflectance for the s component, 405 nm wavelength of the incident light, the complex refractive index of the Al reflecting surface N = n-ik 5.42 It is calculated as -0.25i. As shown in FIG. 11, since the intensity reflectance of the p-s component has a small extinction coefficient, a decrease in the reflectance of the p component at the polarization angle appears remarkably. On the other hand, the intensity reflectance of the s component increases monotonously.

FIG. 12 is a diagram illustrating the incident angle dependence of the complex amplitude reflectance ratio of the p-s component on the Si surface in a complex plane display. In FIG. 12, Re is a real axis, Im is an imaginary axis, and the complex amplitude reflectance ratio ρ (= r _p / r _s ) is 405 nm for the wavelength of incident light, and N = n for the complex refractive index of the Al reflecting surface. -Ik = 5.42-0.25i As shown in FIG. 12, the complex amplitude reflectance ratio ρ of the ps component representing the shape of the reflected polarized light substantially monotonously changes on the real axis from −1 to +1 on the complex plane. This is a feature of the dielectric already described.

  FIG. 13 is a diagram illustrating the incident angle dependence (real part and imaginary part) of the complex amplitude reflectance ratio of the p-s component on the Si surface. As shown in FIG. 13, the incident angle dependence of the amplitude reflectance ratio of the p-s component on the Si surface is clear when the real part and the imaginary part in FIG. 12 are taken out, and the change in the real part is dominant. is there. When right circularly polarized light is incident, the light changes monotonously from clockwise circularly polarized light to counterclockwise circularly polarized light via linearly polarized light near the polarization angle. Since the real part is about −0.9 at an incident angle of 45 ° and about 0.8 after two reflections, the ellipticity angle of the reflection ellipse is about 38.7 °.

  Further, when a dielectric is used, total reflection can be used in a configuration in which light is incident and exited perpendicularly to the inclined surface of a right-angle prism shape. FIG. 14 is a schematic diagram illustrating a configuration example of a recording pit and a reading method. In FIG. 14A, 8a shows a cross section of the information recording medium. The two straight arrows show that light hitting the outside of the pit is transmitted with almost no reflection, and the arrow whose direction has changed on the slope is reflected by the light hitting the slope of the pit. This shows how the direction changes. In FIG. 14B, 9a schematically shows an example of an irradiation spot irradiated on the recording unit. Further, 10a to 10p schematically show examples of reflected light corresponding to the arrangement of recording pits and the ridge direction, and the straight line in the circle of the reflected light 10a to 10p is the ridge direction (= the principal axis direction of the reflection ellipse). is there. In the case of a metal surface, the information recording medium cross section shown in FIG. In addition, when the light hits the outside of the pit enters the clockwise circularly polarized light, it is reflected by the counterclockwise circularly polarized light. In the case of total reflection, the amplitude reflectance ratio angle of the p-s component is always 45 °, and the change due to the incident angle is a difference in the relative phase jump between the p-s components. To calculate specifically, Fresnel amplitude reflectivity

と書くと、全反射条件では、式（数１１）のスネルの法則に対して両辺が実数であり、屈折角φ′に関する式（数１８）、式（数１９）の係数ｃｏｓφ′が純虚数となることから、いずれも（ａ−ｉｂ）／（ａ＋ｉｂ）の形式となりｅｘｐ（−｛２ｔａｎ^―１（ｂ／ａ）｝）と変形できる。従って、反射光の振幅は常に入射光の振幅と等しく、位相のみが２ｔａｎ^―１（ｂ／ａ）だけ遅れる。ｐ成分とｓ成分では入射角依存性が異なるので、一般に全反射条件ではｐ成分とｓ成分間に位相差が生じ、

In the total reflection condition, both sides are real numbers with respect to Snell's law of Expression (11), and the coefficient cos φ ′ of Expression (Expression 18) and Expression (Expression 19) relating to the refraction angle φ ′ is a pure imaginary number. Therefore, both are of the form (a−ib) / (a + ib) and can be transformed to exp (− {2tan ⁻¹ (b / a)}). Therefore, the amplitude of the reflected light is always equal to the amplitude of the incident light, and only the phase is delayed by 2 tan ⁻¹ (b / a). Since the incidence angle dependency is different between the p component and the s component, generally, a phase difference occurs between the p component and the s component under the total reflection condition.

より、ｐ−ｓ成分間の移相変化は、

Thus, the phase shift change between p-s components is

と書ける。

Can be written.

In the configuration of FIG. 14, for example, if the information recording medium formed with a polycarbonate substrate of n _{a =} 1.58, the right-angle prism convex surface and form a ridge line at a predetermined azimuth angle arrangement, total reflection from the rear surface In the configuration in which the record is read out by using, δ _P −δ _s is −48 °. In total reflection, the ellipticity angle of the reflected elliptically polarized light is equal to a half angle and thus becomes 24 °, so that a flat ellipse having a major axis to minor axis ratio of approximately 2: 1 is obtained. In this configuration, total reflection occurs in the recording part, but the unrecorded part is in a transparent state and becomes a bright signal in the dark part. Therefore, if the spot diameter by the converging optical system is equal to the distance between the recording pits Well, compared to the prior art, since the projection of the irradiation light from the pits can be allowed, a wide irradiation light spot can be used. This feature is common to the present invention, as will be explained below.

  FIG. 15 is a diagram schematically illustrating the feature of signal detection according to the present invention with high detection sensitivity in comparison with the state of signal detection in the prior art. FIG. 15A shows an example of signal detection (detection of a bright signal in a dark field) according to the present invention. In FIG. 15A, 9a schematically shows an example of an irradiation spot irradiated on the recording unit. Reference numerals 11a to 11f schematically show examples of reflected light corresponding to the arrangement of recording pits and the ridge direction, and straight lines in the circles of the reflected light 11a to 11f are ridge directions (= the principal axis direction of the reflection ellipse). is there. In addition, a pulse waveform 12a in FIG. 15A shows an image of a detected signal example, and a portion with a high signal level corresponds to a recording pit portion.

  FIG. 15B shows an example of signal detection (dark signal in a bright field) according to the prior art. 9b schematically shows an irradiation spot irradiated to the recording portion. Reference numerals 11g to 11l schematically show examples of reflected light corresponding to the arrangement of recording pits, and a pulse waveform 12b shows an image of an example of a detected signal. The low signal level portion of the pulse waveform 12b corresponds to the recording pit portion.

  In the present invention, as described above, for example, right circularly polarized light is irradiated. At this time, the pits of the recording site have different azimuth angles θ for each pit and have multiple bit information. Reflected light from each recording pit is elliptically polarized light having a constant ellipticity angle but different azimuth angles. In the detection optical system, the signal level of the unrecorded portion decreases due to the difference in polarization state, and in the field of the detection optical system shown in FIG. 15, signal detection is performed for the bright signal in the dark field as shown in FIG. It becomes the arrangement of detection. Further, although the polarization state changes for each pit, the intensity reflectance at the recording site is maintained at a high level. In the bright signal detection in the dark field, the tolerance of the spot size can be increased as compared with the following dark signal detection in the bright field, so that there is an advantage that a low NA optical system that is easy to use and excellent in practicality can be configured. .

  In the prior art, a signal is detected by utilizing a decrease in reflectance at the pit portion. Since the detection signal is a signal proportional to simple reflection intensity and the reflectance at the pit periphery is high, the detection optical system shown in FIG. 15 has a dark field in the bright field as shown in FIG. This is an arrangement for signal detection. In this arrangement, for example, the irradiation spot size needs to be suppressed to be equal to or smaller than the pit size of the recording site. The protrusion of the spot size or the mixing of disturbance light pushes up the dark signal level of the pit portion, and as a result, the S / N is deteriorated. Therefore, in the prior art, a configuration using a high NA detection optical system is indispensable in order to keep the spot size small. In a high-NA detection optical system, it is inevitable that the configuration becomes complicated due to various limitations.

As described above, the configuration of the present invention has a common feature that S / N is high because polarized light is used. Among the configurations of the present invention, the configuration using total reflection shown in FIG. 14 has a particularly high S / N. In the first place, most of the light is transmitted through the unrecorded portion of the transparent body, and the reflectance is as low as several percent, so the influence on the signal of the recording portion is greatly reduced. Therefore, the spot size of the irradiation optical system easily allows at least twice that of the prior art. For example, 1/2 of NA 0.85 of a Blu-ray disc is NA 0.425. Comparing with this, the configuration of NA 0.3 is, for example, assuming that n _a = 2.15 of _a high refractive index glass or a ceramic material (such as Lumicera) at _a wavelength of 405 nm, the total reflection angle φ _T is sin ⁻¹ (1 / N _a ) = 27.7 °, the available convergence angle within the critical angle of total reflection is ± 17.3 ° and NA is 0.3. Considering that it is sufficient to be able to detect the recording pit points that emit light in the dark field, and to separate the adjacent recording pits and detect the polarization state of the light from each light emitting point, the configuration of the present invention. Multiple bit recording can be expected with a pit size of about 405 nm, which corresponds to a Blu-ray disc. In any case, a high-refractive index total reflection material having a small total reflection angle is suitable for reducing the recording pit.

  Furthermore, another feature of this configuration is that the information recording medium can be configured without adding anything to a transparent substrate, so that the manufacturing process is greatly simplified. Therefore, the recording capacity of CD and DVD can be greatly increased and the production cost can be reduced. Since the recording is made of a single transparent material, it has excellent long-term storage characteristics, and is ideal for applications that do not like environmental degradation such as temperature, humidity, and pressure.

  As has been clarified above, the present invention provides a simple and general-purpose optical information recording and reading method by combining specific structures by utilizing the reflection characteristics on the inclined surface of polarized light. As an optimal shape, a circularly polarized light is perpendicularly incident on the information recording medium, and a reading device that observes the polarization state of the specularly reflected light from the recording unit composed of a specific slope formed in a predetermined recording direction by a stamper or the like, Although the basic configuration for reading the inclination (recording direction) of the slope forming the recording unit has been described, the embodiment of the present invention is not limited to this and can be modified in many ways.

  First, the configuration in which the circularly polarized light is perpendicularly incident has a feature that can be combined with the conventional technology, but essentially the circularly polarized light only needs to be irradiated uniformly from the periphery of the recording unit. In this case, many angles other than 45 degrees can be selected for reflection at the recording unit. As shown in FIG. 3, in the single reflection arrangement, since the reading direction is fixed, the incident angle of the reflection surface of the recording unit may be set in the recording information. By adding a plurality of incident angles as a recording multiplicity information in addition to a plurality of azimuth angles, the multiplicity of recording bits can be further increased. That is, in addition to the azimuth angle θ of the reflecting surface constituting one bit of the recording unit, the incident angle φ can be used as multilevel recording information.

  Similarly to the configuration using total reflection in FIG. 14, when the configuration is such that the transparent substrate or protective film having a high refractive index is transmitted and reflected on the back surface, the observation direction is fixed in the vertical direction, and the reflection is used once. The incident angle that can be obtained is 45 ° or less. In a transparent medium system that enters from a high refractive index to a low refractive index, the Fresnel reflection coefficient is a real number up to the total reflection angle, and when the total reflection angle is exceeded, the cosine of the refraction angle becomes a forward imaginary number. Therefore, the change from −1 to +1 on the complex plane is compressed into the incident angle region from the incident angle 0 ° to the total reflection angle. This characteristic is advantageous when the incident angle dependence of Ψ of reflected light is used in a single reflection.

FIG. 16 is a diagram illustrating the incident angle dependence of the intensity reflectance of a transparent recording medium having a refractive index n = 2.145. The incident angle ranges from normal incidence φ = 0 ° to total reflection angle φ _T = 27. The characteristic when changing up to 8 ° is shown. 16, the intensity reflectance for _{r p} is p component, _{r s} is the intensity reflectance for the s component, is calculated 405nm wavelength of incident light, the refractive index of the transparent recording medium as n = 2.145 . As shown in FIG. 16, the total reflection region (φ _T = 27.8 °) the intensity reflectance _r s, _{r p} are both 1.

FIG. 17 is a diagram illustrating the incident angle dependence of the complex amplitude reflectance ratio of a transparent recording medium having a refractive index n = 2.145 as a complex plane display. In FIG. 17, Re is a real axis, Im is an imaginary axis, and the complex amplitude reflectance ratio ρ (= r _p / r _s ) is 405 nm for the wavelength of incident light, and n = 2. It is calculated as 145. In FIG. 17, ρ (= r _p / r _s ) moves to the right on the real axis from normal incidence φ = 0 ° to the total reflection angle φ _T = 27.8 °, and the declination is negative in the total reflection region Changes to a unit circle.

  FIG. 18 is a diagram illustrating the incident angle dependence (real part and imaginary part) of the complex amplitude reflectance ratio of a transparent recording medium having a refractive index n = 2.145. In FIG. 18, Im (ρ) and Re (ρ) are calculated assuming that the wavelength of incident light is 405 nm and the refractive index of the transparent recording medium is n = 2.145.

As shown in FIGS. 16 to 18, taking the refractive index n = 2.145 as an example, the intensity reflectance of the ps component of the transparent recording medium having the refractive index n = 2.145 (FIG. 16), p−. When the complex plane display of the complex amplitude reflectance ratio of the s component (FIG. 17) and the real part and imaginary part (FIG. 18) of the complex amplitude reflectance are calculated, both the normal incidence φ = 0 ° and the total reflection angle φ _T = 27. The incident angle dependence is compressed in the region of .8 °. In the complex plane display of FIG. 17, the total reflection region changes in the lower right region of the unit circle. The change due to total reflection in the equation (Equation 22) appears in this part. In FIG. 18, it appears as a simultaneous change of the real part and the imaginary part at an angle larger than the total reflection angle. In FIG. 18, the polarization state of the reflected light when the right circularly polarized light is uniformly irradiated from the periphery is added. While the incident angle φ changes from 0 ° to the total reflection angle, it changes monotonically from left circularly polarized light to right circularly polarized light, and a 1: 1 correspondence can be taken.

  Next, specific embodiments of the optical system will be described.

  FIG. 19 is a schematic diagram illustrating a configuration example of a recording pit and a reading method when using reflection on the back surface of a high refractive index medium. In FIG. 19A, 8b shows a cross section of the information recording medium (a cross section of the highly refractive substrate). The arrows schematically show how the light incident on the pit portion is reflected by the inclined reflecting surface and changes its direction. In FIG. 19 (b), 13a to 13q schematically show examples of reflected light corresponding to the arrangement and ridge directions of the recording pits, and the arrows in the circles of the reflected light 13a to 13q indicate the direction of the inclined reflecting surface. (= The minor axis direction of the reflection ellipse). Further, the length of the arrow indicates a change in ellipticity.

In FIG. 19 (a), when the right circularly polarized light is irradiated uniformly from the upper air side, the light is refracted on the surface of the substrate and enters the substrate, and the inclined reflecting surface facing each predetermined azimuth angle in the vertical direction. Only the component reflected by the light beam goes to the detection system of the polarization state, and multiplex recording readout as shown in FIG. 19B is realized. In the reflection of the transparent body, the minor axis of the reflection ellipse coincides with the incident surface direction, and the ellipticity angle changes as a function of the incident angle. The ellipticity angle coincides with tan ^-1 ρ including the sign. The real part in FIG. 18 is equal to ρ = tan Ψ · cos Δ because Δ is 0 or π, and is equal to the ellipticity of the observed ellipse. Therefore, a positive ellipse is reflected in the positive direction, and a counterclockwise ellipse is reflected in the negative direction.

  As shown in FIG. 19B, the recorded information can be schematically represented as a projection of the normal of the inclined reflecting surface, the direction of the normal vector coincides with the minor axis of the ellipse, and the length of the vector is The change in ellipticity is shown. In this configuration, the azimuth angle and the incident angle of the normal line constituting the recording of the recording pit are independent variables, and information per pit such as an optical disk can be doubled. Furthermore, by combining with an optical system of a microscopic polarization camera that two-dimensionally detects the polarization state, an information recording / reproducing system using a large information tag or chip can be configured without a movable part.

  In the configuration shown in FIG. 19, the incident angle on the vertical incident side until just before total reflection can be used. As shown in FIG. 18, the incident angle change (the real part of the complex amplitude reflectance ratio) of the polarization state of the reflected light is compressed and collected on the vertical incident side up to the critical angle of total reflection. When total reflection is not used, using the half space in front of the information recording medium and fixing the optical axis of the reflected light in the normal direction of the information recording medium, the usable incident angle is limited to a range of ± 45 °. When the incident angle is higher than that, irradiation light from the back side of the information recording medium surface is required.

  Such a restriction is eliminated in the configuration of the back surface reflection of the dielectric shown in FIG. This is a major feature of the present invention, and is the most advantageous configuration that can achieve a density 20 times that of the conventional method. In the case of a multi-layered disk, for example, in the case where a tilt angle (± 90 °) and an azimuth angle (± 90 °) of a minute mirror are divided by 1024 and recording information of binary 10 bits is placed, 20 layers of multi-layer discs are placed. This is equivalent to a high density equivalent to that of the case. It is relatively easy to further increase the number of divisions several times.

  Next, a recordable information recording medium (RAM) will be described. The writing operation according to the present invention is roughly classified into recording by mechanical (geometrical optical) deformation driving and physical optical recording by light, electric field or magnetic field. In recording by mechanical (geometrical optical) deformation driving, which is one form of the writing operation according to the present invention, the operation of controlling the posture of the inclined reflecting surface of the recording unit is performed. Specifically, an operation of controlling inclination and azimuth rotation or inclination in the xy2 direction is performed. If the input is an electric signal, a control operation of a minute slope (mirror surface) can be realized by applying the MEMS technology. Alternatively, driving by a piezo element and rotation by a micromotor may be combined.

  An example of the control operation will be described with reference to FIG. FIG. 20 is a diagram illustrating an example of a control operation for one posture among minute slopes constituting the recording unit, and illustrates the case of driving the in-plane azimuth angle and the incident angle. The recording unit shown in FIG. 20A includes a fixed unit 15 and a cylindrical movable unit 16 having a mirror surface as an end surface. Further, the recording section shown in FIG. 20B is composed of a fixed section 15 and a spherical movable section 17 that is partially flat. In FIG. 20A and FIG. 20B, the arrows indicate the direction in which the movable part moves. The drive shaft that drives the movable portion 16 and the movable portion 17 may be a double structure as long as it can be controlled ± 90 ° independently. Any two of the three orthogonal axes may be used as the rotation axis.

  In physico-optical recording by light, electric field or magnetic field, which is another form that realizes the write operation of a recordable information recording medium (RAM), the posture of the slope is kept constant, and reflection on this slope The reflected polarization state is controlled by electric signal input. In this case, recording is performed on a tilted surface by causing a change in reflection optical characteristics (specifically, Δ and Ψ) by using an electric field, a magnetic field, or a phenomenon caused by electromagnetic waves (light) having a wavelength different from that of readout.

  Even when the reflection optical characteristic change induced by the recording / writing operation is small, if sufficient reproducibility is obtained, the read polarization sensitivity is increased by optimizing the readout arrangement of the optical characteristics related to the reflection on the recording surface. be able to. In other words, a sufficiently large change in read signal can be obtained with a predetermined write change. As described above, in the writing operation according to the present invention, the recording surface is slanted to increase the sensitivity of multilevel recording by the polarization state as compared with the conventional technology such as a magnetic disk in which the recording surface is horizontal. Can do.

  The optimum configuration for reading can be described by the optical properties of the recording surface in a state covered with a magnetic film or the like. First, the incident polarized light is linearly polarized light having an azimuth angle equal to the main azimuth angle of the recording surface at the wavelength of the reading light, that is, the amplitude reflectance ratio angle of the p-polarized light and the s-polarized light, and the intensities of both components are equal after reflection. Incident. The angle of the inclined surface is the main incident angle of the recording surface at the wavelength of the reading light. The main incident angle is defined by the relative phase difference Δ of reflection between p-polarized light and s-polarized light being ± 90 °. In the irradiation of the linearly polarized light with the main azimuth angle, the reflected light at the main incident angle becomes circularly polarized light.

  FIG. 21 is a diagram illustrating an example of forming a recording portion having an inclined surface and a recording layer, which is formed on an information recording medium. FIG. 21A shows an example in which a recording layer 19a made of a coating film for controlling optical anisotropy is formed on a V-groove on which an Al layer is formed, and is covered with a transparent protective layer 18a. In FIG. 21A, black circles indicate 58 °, arrows indicate how incident light is reflected, and hatched arrows indicate the direction of the magnetic field or electric field during writing.

  In FIG. 21B, the recording layer 19b made of a coating film for controlling optical anisotropy is formed on the dielectric 18b in which the V-groove is formed, and the total reflection on the back surface of the dielectric is utilized. In this example, Δ is ± 90 ° in total of two reflections. In FIG. 21B, the black circles indicate 45 °, the arrows indicate the manner in which incident light is reflected, and the hatched arrows indicate the direction of the magnetic field or electric field during writing. FIG. 21C shows a case where a recording layer 19c made of a coating film for controlling optical anisotropy is formed on a dielectric 18c having an inclined surface, which uses mirror reflection on the back surface of the dielectric. This is an example of detecting the polarization state of reflected light by circular reflection. In FIG. 21 (c), an arrow indicates a state in which incident light is reflected, and a hatched arrow indicates the direction of a magnetic field or an electric field at the time of writing.

  For example, as shown in FIG. 21 (a), in the case of the surface reflection of the Al surface, referring to FIG. 8 (a) showing the Δ of the double reflection, Δ = 270 ° (= −90 °) The incident angle is 58 degrees. Therefore, in the V-groove two-reflection configuration, if the apex angle formed by the V-groove ridge is 58 × 2 = 116 °, the optical axis of the reading light and the optical axis of the irradiation light are each from the normal of the surface of the recording medium. 116−90 = 26 ° may be inclined.

  In the RAM configuration, the direction of the V-groove is fixed. For example, since it is fixed in parallel with the track direction (perpendicular to the paper surface of FIG. 21), only one irradiation light is required. The writing operation is recorded by a change in the strength of the magnetic field or electric field. Or you may control by changing the direction of a magnetic field or an electric field (direction of the arrow of the oblique line in FIG. 21). Under these conditions, the polarization state is greatly changed by applying a thin film on the reflective surface or the low refractive index side (air side) surface of total reflection and adding a slight optical anisotropy. Therefore, the resolution for writing the record information can be increased.

  For example, when information is written by applying existing technology of magneto-optical recording and liquid crystal display using a magnetic film or a liquid crystal film, the surface of the writing medium is mainly for the wavelength of the reading light of the medium. The incident angle. That is, the inclination angle is a specific value determined by the medium. As a method of adding optical anisotropy to the reflecting surface, in addition to the above method, optical phenomena described in academic books on optical properties such as a photochromic thin film can be used. What is necessary is just to write record information using optical properties of writing light having a wavelength different from that of reading light, and to cause a change in reflected polarization characteristics by a predetermined optical process.

  The principle and the embodiment of the invention in the present invention have been described above. In the present invention, information is recorded and read out using two variables, the shape of elliptically polarized light, that is, the inclination of the principal axis of the ellipse and the ellipticity of the ellipse. Since information is basically detected by detecting the polarization state, the conventional technique of ellipsometry can be used. Further, a polarization reading optical system technique used in a magneto-optical recording reading optical system can also be applied. When these known techniques are applied to the present invention as elements, it is necessary to select and apply based on the measurement principle described below.

In the polarization state to be detected in the present invention, the required configuration is roughly divided.
(1) One variable configuration for detecting the azimuth angle θ of an ellipse having a predetermined ellipticity angle.
(2) Two-variable configuration that detects both ellipticity angle and azimuth angle.
There are two cases.
In the case of (1), the detection is performed on the Poincare sphere by detecting the value of S ₁ or S ₂ or the ratio thereof on a plane perpendicular to the S ₃ axis having a constant ellipticity angle. In (2), the recording positions where the azimuth angle and ellipticity angle are distributed at predetermined intervals on the Poincare sphere, and the values of S ₁ , S ₂ and S ₃ or the ratio thereof are detected on the Poincare sphere.

In (1), information of the S ₃ or because it does not require the rotation direction of the information of the ellipse, 1/4 rotation polariser method belongs detection technology that does not use phase elements such as wave plates, in (2), A detection technique belonging to a rotational phaser method that includes a phase element such as a quarter-wave plate for discriminating the rotation direction of the ellipse including S ₃ in the detection optical system and can detect the Stokes parameter is used.

  In applications that require high-speed reading, it is desirable that the mechanical drive unit be eliminated even in the case of (1) rotating element type detection. For this purpose, a configuration in which the polarization state is modulated using a polarization modulation element using various polarization modulation effects such as the Faraday effect, the Kerr effect, the Pockels effect, and the phase angle of the cos θ signal is determined and detected by a lock-in detection method. It can also be taken. However, a method of detecting the polarization state by dividing the reflected light into a plurality of spaces and allocating a plurality of polarizers capable of detecting a specific polarization state is more excellent from the viewpoint of speeding up.

For example, a linear polarizer having a different azimuth angle θ is assigned to each channel of a detector having a plurality of channels, a rotational phaser signal is simultaneously detected, and the phase angle of the cos θ signal (azimuth angle of the main axis of the ellipse) is detected by signal processing. ) As a multi-value signal. The number of channels is at least three, which is the same as the bit multiplicity. Further, the detection azimuth angle that each channel is responsible for is based on an arrangement that is as far apart as possible and equidistant from each other on the S ₂ and S ₃ surfaces of the Poincare sphere. In the case of three channels, the detection azimuth is 60 ° on the Poincare sphere as a reference, and is, for example, 0 ° (= 180 °), 60 ° (240 °), 120 ° (300 °). The azimuth angle of the real space is ½, 0 °, 30 °, and 60 °.

  Although it is possible to employ a configuration in which a linear polarizer is used at these azimuth angles, in the configuration (1) of the present invention, since the ellipticity of elliptically polarized light is fixed, a phase shifter such as a quarter wavelength plate is used. The signal contrast for each channel can also be optimized by arranging a predetermined elliptical polarizer in each channel. Further, the channel specification and number are set to match the reference azimuth setting value of multiple bits, and only the channel with a predetermined bit angle outputs the phase angle zero of the cos θ signal with respect to the reference average output 0.5 of all channels. It is also possible to configure a high-speed parallel output circuit having a predetermined number of bits by making use of the fact that the other channel forms a numerical value at a predetermined azimuth angle of the cos θ signal at the level of the signal 1.

  In the Stokes parameter detection method (2), in principle, it is necessary to obtain a signal in which the phase of the polarization state is changed using a phase shifter such as a quarter-wave plate. Also in this case, for high-speed reading, a configuration in which a mechanical drive unit for detection of the rotational phaser type is excluded is desirable. The configuration of the detection system is in principle the same as the configuration in (1), and specific polarizers are arranged in a plurality of channels. The polarizer in this case is an elliptical polarizer that is orthogonal to a specific elliptical polarization state, including a linear polarizer and a circular polarizer. The optimum arrangement can be devised in the distribution region so that the maximum sensitivity can be obtained with respect to the distribution of the polarization state to be detected on the Poincare sphere. In this case, the number of detection channels on the Poincare sphere is at least three based on the principle of triangulation.

Each channel is located at a specific detection coordinate on the Poincare sphere, and the channel output may be considered to be proportional to the distance from the detection coordinate. For example, choosing right circular photons (S _3-axis = Arctic) channel, the intensity for the left circularly polarized light (-S _3-axis = Antarctica) perpendicular on the Poincare sphere 0 (quenching), the intensity in the right circularly polarized light A signal of 1 (maximum value) is obtained. For elliptically polarized light, the intensity increases as the ellipticity decreases in the counterclockwise ellipse of the southern hemisphere, the intensity increases by 0.5 for linearly polarized light on the equator, and the ellipticity angle increases for elliptically polarized light entering the northern hemisphere and clockwise. The strength increases as you go. That is, the intensity increases as the point on the Poincare sphere representing elliptically polarized light approaches the North Pole.

When the polarization state covers all over the Poincare sphere, three axes that are orthogonal to each other on the Poincare sphere may be taken. For example, S ₁ , S ₂ , S ₃ , a point on the axis may be taken, but an ellipse in the region of −S ₁ , −S ₂ , −S ₃ , for example, azimuth angle −67.5 °, ellipticity It should be noted that the output signal intensity decreases for an ellipse centered on a left-handed elliptical polarization with an angle of −22.5 °. In the configuration of FIG. 19 of the present invention, is irradiated from the peripheral the right circularly polarized light, polarized light component to be detected that is reflected vertically are mostly elliptically polarizing groups left rotation, detected intensity level, S ₃ is negative Located in the Southern Hemisphere. In this case, in addition to the linear polarizers of the equal triaxial 0 ° (= 180 °), 60 ° (240 °), and 120 ° (300 °) described in (1), the left circular polarizer of −S ₃ is used. A four-channel configuration that adds is an optimal solution.

  Similarly, the parallel output configuration by the parallel circuit processing described in the case of (1) can be configured by a predetermined elliptical polarizer in which a quarter-wave plate and a linear polarizer are combined at a predetermined azimuth with respect to the reflected light. If the linear polarizer is composed of a polarizing beam splitter, a symmetric point on the Poincare sphere is selected as the output point as two outputs for two orthogonal polarization states, and all reflected signal light is effectively used for signal processing. it can.

  In order to divide the reflected light into a plurality of spaces and guide them to each channel, a method of dividing the reflected light along the optical axis of the reflected light using a beam splitter may be used. A method of dividing into multiple parts can also be used. In this case, for example, a bundle of polarization detection fibers may be used, but the method of spatial division with a minute mirror surface using the polarization characteristics of the reflection surface disclosed in the present invention can be used. Alternatively, the total reflection, which is another configuration of the present invention, may be used to guide the reflected light in a ring shape and detect it with a detector arranged in a ring shape. Specific embodiments of the information recording and / or reproducing apparatus including irradiation of incident circularly polarized light are illustrated in FIGS.

  FIG. 22 is a diagram showing a schematic configuration example of an information recording and / or reproducing apparatus according to the present invention. FIG. 22A is a cross-sectional view schematically showing a cross section of a configuration example of the irradiation optical system and the polarization detection optical system, and FIG. 22B is a translucent mirror 30a viewed from the condenser lens 40a side. FIG. 6 is a plan view schematically showing the arrangement of a horizontal linear polarizer 60a, a 45 ° linear polarizer 60b, a circular polarizer 60c0, and detectors 70a to 70d. The information recording and / or reproducing apparatus shown in FIG. 22A includes a circularly polarized light generating means 20a, a translucent mirror 30a, a condensing lens 40a, a horizontal linear polarizer 60a, a 45 ° linear polarizer 60b, a circular polarizer 60c0, It consists of detectors 70a to 70d. The circular polarizer 60c0 includes a phase shifter 60c1 and a linear polarizer 60c. A solid line arrow indicates reading light (incident circularly polarized light), a broken line arrow indicates reflected light, and 300 indicates an information recording medium.

  Note that a condensing lens for enlarging and projecting the recording surface onto the detectors 70a to 70d at an appropriate magnification may be inserted in front of the detectors 70a to 70d in the optical path of the reflected light. In FIG. 22, the circularly polarized light generating means 20a, the translucent mirror 30a, and the condenser lens 40a are examples of reading light irradiating means including a light source for irradiating the recording portion of the information recording medium 300 with reading light. The linear polarizer 60a, the 45 ° linear polarizer 60b, the circular polarizer 60c0, and the detectors 70a to 70d are examples of reflected light detection means for detecting reflected light reflected by the recording unit.

  In FIG. 22A, a circularly polarized light generating means 20a is a means for generating circularly polarized read light. For example, a light source such as a laser diode or a light emitting diode, a collimator lens, a linear polarizer, a quarter wavelength plate. Etc. The translucent mirror 30a is a translucent mirror that transmits the reading light and bends the optical path of the reflected light by, for example, 90 °. The condensing lens 40 a is a lens that condenses the circularly polarized reading light generated by the circularly polarized light generating unit 20 a on the recording unit of the information recording medium 300. The horizontal linear polarizer 60a is a linear polarizer in which the transmission axis direction of a linear polarizer is arranged at an azimuth angle of 0 °, and transmits only a linearly polarized light component having an azimuth angle of 0 °. The 45 ° linear polarizer 60b is a linear polarizer in which the transmission axis direction of the linear polarizer is arranged at an azimuth angle of 45 °, and transmits only a linearly polarized light component having an azimuth angle of 45 °. The circular polarizer 60c0 is a right circular polarizer obtained by combining the phase shifter 60c1 and the linear polarizer 60c, and transmits only the right circular polarization component. For example, the circular polarizer 60c is formed by inclining 45 ° of the fast axis of light among the neutral axes of the phase shifter 60C1, which is a quarter-wave plate, with respect to the transmission axis direction of the linear polarizer 60c. It can be realized by arranging. The detectors 70a to 70d are detectors that convert the intensity of light entering each detector into the strength of an electric signal. For example, a photodiode or a CCD can be used.

  The information recording medium 300 is an information recording medium according to the present invention. That is, the recording portion of the information recording medium 300 is formed with an inclined reflecting surface having a predetermined area and having a predetermined inclination angle so as to form a plurality of types of azimuth angles corresponding to the multi-value information. Alternatively, the recording portion of the information recording medium 300 is formed with an inclined reflective surface having a predetermined area and having a predetermined azimuth so as to form a plurality of types of inclination angles corresponding to the multi-value information. Alternatively, the recording part of the information recording medium 300 is formed with an inclined reflection surface having a predetermined area combined so as to form a plurality of types of inclination angles and a plurality of types of azimuth angles corresponding to multi-value information. Yes.

  In FIG. 22 (a), the reading light, which is circularly polarized light generated by the circularly polarized light generating means 20a, passes through the semitransparent mirror 30a, and is collected by a condensing lens 40a to a recording unit (not shown) of the information recording medium 300. Focused. The condensed light is reflected by the recording unit, passes through the condensing lens 40a again as elliptically polarized reflected light having recording information, and changes its path by, for example, 90 ° by the semi-transparent mirror 30a, thereby detecting the detectors 70a to 70d. Proceed in the four directions in which is placed. The reflected light traveling in the four directions enters the horizontal linear polarizer 60a, the 45 ° linear polarizer 60b, and the circular polarizer 60c0, respectively, and the predetermined components corresponding to the characteristics of the respective polarizers are transmitted through the detector 70a. It is converted into an electric signal corresponding to each light intensity at ˜70d. In addition, although a phase shifter and a polarizer are not arranged between the semitransparent mirror 30a and the detector 70d, the detector 70d is a detection for the purpose of detecting the total intensity of the reflected light. Because it is a vessel. However, the total intensity of the reflected light is not an essential detection item. Further, when the translucent mirror 30a has a change in polarization state that cannot be ignored with respect to reflected light or transmitted light, it may have a compensating action.

  The electrical signals output from the detectors 70a to 70d are input to a signal processing unit configured by a microcomputer or the like, and the Stokes parameters can be determined by a known ellipsometry method from the signal intensity ratio of the electrical signals. The tilt angle and / or azimuth angle of the recording unit of the information recording medium 300 can be specified. As a result, the recorded information can be read. FIG. 22 shows an example in which the recording unit of the information recording medium 300 is irradiated without bending the optical path of the reading light generated by the circularly polarized light generating unit 20a. However, the reading light generated by the circularly polarized light generating unit 20a is used. The optical system may be configured such that the light path is bent by, for example, 90 ° with the semi-transparent mirror 30a and irradiated to the recording unit of the information recording medium 300 and guided to the detectors 70a to 70d without bending the optical path of the reflected light. .

  FIG. 23 is a diagram showing another schematic configuration example of the information recording and / or reproducing apparatus according to the present invention, which is a configuration example using circularly polarized uniform irradiation and a one-time reflection recording unit. Further, the optical axis of the circularly polarized light irradiation needs to be arranged in the incident surface of the inclined surface of the recording unit. FIG. 23A is a cross-sectional view schematically showing a cross-section of a configuration example of the irradiation optical system and the polarization detection optical system, and FIG. 23B is a total reflection prism phase viewed from the condenser lens 40d side. It is a top view which shows typically arrangement | positioning of the polarizer 30b, the linear polarizers 60d-60g, and the detectors 70a-70d. In the figure, the same components as those in FIG. 22 are denoted by the same reference numerals, and description thereof is omitted.

  The information recording and / or reproducing apparatus shown in FIG. 23 includes a right circularly polarized light generating unit 20b, a left circularly polarized light generating unit 20c, a total reflection prism phaser 30b, condensing lenses 40b to 40d, linear polarizers 60d to 60g, and a detector. 70a to 70d. A solid line arrow indicates reading light (left and right circularly polarized light), a broken line arrow indicates reflected light, and 300 indicates an information recording medium. In FIG. 23, for convenience, two circularly polarized light generating means, that is, a right circularly polarized light generating means 20b and a left circularly polarized light generating means 20c, are shown. However, actually, the irradiated light is recorded on the recording unit of the information recording medium 300. It is necessary to install a light source at a position that is reflected by the inclined surface toward the detectors 70a to 70d in accordance with the set number of azimuth angles.

  Note that a condensing lens for enlarging and projecting the recording surface onto the detectors 70a to 70d at an appropriate magnification may be inserted in front of the detectors 70a to 70d in the optical path of the reflected light. In FIG. 23, the right circularly polarized light generating means 20b, the left circularly polarized light generating means 20c, and the condensing lenses 40b and 40c are reading light irradiating means including a light source that irradiates the recording portion of the information recording medium 300 with reading light. As an example, the total reflection prism phase shifter 30b, the condenser lens 40d, the linear polarizers 60d to 60g, and the detectors 70a to 70d are examples of reflected light detection means for detecting reflected light reflected by the recording unit.

  In FIG. 23A, right circularly polarized light generating means 20b is means for generating right circularly polarized read light. For example, a light source such as a laser diode or a light emitting diode, a collimator lens, a linear polarizer, and 1/4. It can be composed of a wave plate or the like. The left circularly polarized light generating means 20c is a means for generating left circularly polarized read light, and can be composed of, for example, a light source such as a laser diode or a light emitting diode, a collimator lens, a linear polarizer, a quarter wavelength plate, or the like. Note that right circularly polarized light is generated by tilting the axis of the light wave speed faster among the neutral axes of the quarter-wave plate with respect to the transmission axis direction of the linear polarizer by 45 °. Left circularly polarized light is generated by placing the axis of the neutral wavelength of the quarter-wave plate tilted at 45 ° with respect to the transmission axis direction of the polarizer at 45 °. The reason for having two circularly polarized light generating means, that is, a right circularly polarized light generating means 20b and a left circularly polarized light generating means 20c, is that the recording of the azimuth angle is distinguished by the rotational direction of the elliptically polarized light reflected by the recording unit of the information recording medium 300 This is because the angle is expanded from the half space of 180 ° to the entire space of 360 °.

  The total reflection prism phase shifter 30b is an optical element that is made of a prism material and generates a predetermined reflection phase angle δ determined by the refractive index and the reflection angle of the prism material. Specifically, the incident elliptically polarized light is decomposed into two orthogonal components of the p-direction component and the s-direction component of the prism reflection, and a phase difference of δ is generated between the respective components. The azimuth angle changes. The linear polarizers 60d to 60g can constitute an arbitrary elliptical polarizer by combining with the total reflection prism phase retarder 30b. For example, with respect to the azimuth angle of the reflected light entering the linear polarizers 60d to 60g from the total reflection prism phase plate 30b, the transmission axis directions of the linear polarizers 60d to 60g are set to predetermined values as in the case of FIG. Thus, a horizontal linear polarizer that transmits only a linearly polarized light component with an azimuth angle of 0 °, a 45 ° linear polarizer that transmits only a linearly polarized light component with an azimuth angle of 45 °, and a right circular polarizer that transmits only a right circularly polarized light component. A left circular polarizer that transmits only the left circularly polarized light component can be realized.

  In FIG. 23A, the reading light (incident circularly polarized light) generated by the right circularly polarized light generating unit 20b and the left circularly polarized light generating unit 20c is a recording unit (not shown) of the information recording medium 300 by the condenser lenses 40b and 40c. Light). The condensed light is reflected by the recording unit, passes through the condensing lens 40d as elliptically polarized reflected light having recording information, and changes its path, for example, by 90 ° by the total reflection prism phase shifter 30b, thereby detecting the detectors 70a to 70a. A predetermined reflection phase angle δ is generated while proceeding in four directions in which 70d is arranged. The reflected light traveling in the four directions enters the linear polarizers 60e to 60g, respectively, and a predetermined polarization component determined by the combination of the total reflection prism phase retarder 30b and each of the linear polarizers (60e to 60g) is transmitted. 70a to 70d are converted into electrical signals corresponding to the respective light intensities.

  The electrical signals output from the detectors 70a to 70d are input to a signal processing unit configured by a microcomputer or the like, and the Stokes parameters can be determined by a known ellipsometry method from the signal intensity ratio of the electrical signals. The tilt angle and / or azimuth angle of the recording unit of the information recording medium 300 can be specified. As a result, the recorded information can be read. In FIG. 23 (a), by using two circularly polarized light generating means, that is, a right circularly polarized light generating means 20b and a left circularly polarized light generating means 20c, the elliptically polarized light reflected at an inclination angle of ± 90 ° is converted into each elliptical light. The direction of rotation can be distinguished.

  FIG. 24 is a diagram showing another schematic configuration example of the information recording and / or reproducing apparatus according to the present invention. FIG. 24A is a cross-sectional view schematically showing a cross section of a configuration example of the irradiation optical system and the polarization detection optical system, and FIG. 24B is a view of the detectors 70a˜ 70 viewed from the condenser lens 40a side. It is a top view which shows typically arrangement | positioning of 70f, the polarization irradiation fibers 90a-90f, and the polarization detection fibers 90g-90l. In the figure, the same components as those in FIGS. 22 and 23 are denoted by the same reference numerals, and the description thereof is omitted.

  The information recording and / or reproducing apparatus shown in FIG. 24A includes a light source 25, a condenser lens 40a, detectors 70a to 70f, polarization irradiation fibers 90a to 90f, and polarization detection fibers 90g to 90l. Reference numeral 300 denotes an information recording medium. In addition, although the polarization detection device (phaser, linear polarizer) is not illustrated, between the polarization detection fibers 90g to 90l and the detectors 70a to 70f arranged corresponding to the polarization detection fibers 90g to 90l, Or it can install between the condensing lens 40a and the polarization detection fibers 90g-90l. In addition, the polarization detection fibers 90g to 90l may have an action as a polarization detection device (phase shifter, linear polarizer). The detectors 70a to 70f may be integrated to form a detector array. Further, the polarization irradiation fibers 90a to 90f and the polarization detection fibers 90g to 90l may be replaced with minute mirror surfaces.

  Note that a condensing lens for enlarging and projecting the recording surface onto the detectors 70a to 70f at an appropriate magnification may be inserted before the detectors 70a to 70f in the optical path of the reflected light. In FIG. 24, the light source 25, the polarization irradiation fibers 90a to 90f, and the condensing lens 40a are examples of reading light irradiation means including a light source that irradiates the recording portion of the information recording medium 300 with reading light. The polarization detection device (phaser, linear polarizer), polarization detection fibers 90g to 90l, and detectors 70a to 70f are examples of reflected light detection means for detecting reflected light reflected by the recording unit.

  In FIG. 24A, a light source 25 is a light source such as a laser diode or a light emitting diode. The polarization irradiation fibers 90 a to 90 f are fibers that generate circularly polarized read light from the light emitted from the light source 25 and guide it to the condenser lens 40 a, and make the circularly polarized light incident on the information recording medium 300. The polarization detection fibers 90g to 90l are fibers that guide the reflected elliptically polarized light to the detectors 70a to 70f. In the example of FIG. 24, six detectors 70a to 70f are used. As described above (see the description of FIG. 22), the number of normalized Stokes parameters to be read is 3 (reflected light). Therefore, by using six detectors, the signal output can correspond to the positive and negative azimuths of each axis, and the detection accuracy can be further improved. . Note that six detectors may be integrated to form one detector array. In addition, as described with reference to FIGS. 22 and 23, the polarization detecting device (phaser, linear polarizer) (not shown) combines the phaser and linear polarizer, and with respect to the azimuth angle of the reflected light entering the linear polarizer. By setting the transmission axis direction of the linear polarizer to a predetermined value, an arbitrary elliptical polarizer can be obtained.

  In FIG. 24A, the light emitted from the light source 25 passes through the polarization irradiation fibers 90a to 90f, and is read as circularly polarized read light to the recording unit (not shown) of the information recording medium 300 by the condenser lens 40a. Focused. The condensed light is reflected by the recording unit and passes through the condensing lens 40a again as elliptically polarized reflected light having recording information, and the polarization detection fibers 90g to 90l and a polarization detection device (not shown) (phaser, straight line). A predetermined component corresponding to the characteristics of each polarization detection device (phase shifter, linear polarizer) is transmitted through the polarizer, enters the detectors 70a to 70f, and the respective lights are detected by the detectors 70a to 70f. It is converted into an electrical signal corresponding to the intensity.

  The electrical signals output from the detectors 70a to 70f are input to a signal processing unit configured by a microcomputer or the like, and the Stokes parameters can be determined by a known ellipsometry technique from the signal intensity ratio of the electrical signals. The tilt angle and / or azimuth angle of the recording unit of the information recording medium 300 can be specified. As a result, the recorded information can be read. In addition, in the example which isolate | separates polarization | polarized-light with the polarization detection fibers 90g-901 shown in FIG. 24, there also exists the characteristic that arrangement | positioning of the detectors 70a-70f or the detector array which integrated them can be designed freely.

  FIG. 25 is a diagram showing another schematic configuration example of the information recording and / or reproducing apparatus according to the present invention. FIG. 25A is a cross-sectional view schematically showing a cross section of a configuration example of the irradiation optical system and the polarization detection optical system, and FIG. 25B is a total reflection phase shifter viewed from the condenser lens 40a side. 30c is a plan view schematically showing the arrangement of 30c, detectors 70a to 70l, detector holding unit 71, linear polarizer ring 100a, and condenser lenses 110a to 110l. In the figure, the same components as those in FIGS. 22 to 24 are denoted by the same reference numerals, and the description thereof is omitted.

  The information recording and / or reproducing apparatus shown in FIG. 25A includes a circularly polarized light generating means 20a, a total reflection phase shifter 30c, condenser lenses 40a, 110a to 110l, detectors 70a to 70l, a detector holding unit 71, a straight line. It is composed of a polarizer ring 100a. Reference numeral 300 denotes an information recording medium. The polarization detectors 70a to 70l may be integrated to form a detector array. In FIG. 25, the circularly polarized light generating means 20a and the condenser lens 40a are examples of reading light irradiation means including a light source for irradiating the recording portion of the information recording medium 300 with reading light. The condenser lenses 110a to 110l, the linear polarizer ring 100a, and the detectors 70a to 70l are examples of reflected light detection means for detecting reflected light reflected by the recording unit.

  In FIG. 25A, a total reflection phase shifter 30c is an optical element whose phase angle changes according to the elliptically polarized light to be detected. The linear polarizer ring 100a is a polarizer that can constitute an arbitrary elliptical polarizer by combining with the total reflection phase retarder 30c, and can change the characteristics for each region in accordance with the elliptically polarized light to be detected. The condensing lenses 110a to 110l are condensing lenses for enlarging and projecting the recording surface on the detectors 70a to 70l at an appropriate magnification. In the example of FIG. 25, twelve detectors 70a to 70l are used. As described above (see the description of FIG. 22), the number of normalized Stokes parameters to be read is 3 (reflected light). Therefore, the detection accuracy can be further improved as compared with the case where the six detectors shown in FIG. 24 are used. Note that twelve detectors may be integrated into one detector array.

  In FIG. 25 (a), the reading light, which is circularly polarized light generated by the circularly polarized light generating means 20a, is condensed on a recording unit (not shown) of the information recording medium 300 by the condenser lens 40a. The condensed light is reflected by the recording unit, passes through the condenser lens 40a again as elliptically polarized reflected light having recording information, and changes its path, for example, by 90 ° by the total reflection phase shifter 30c. Enter the linear polarizer ring 100a via ~ 110l. A predetermined polarization component determined by the combination of the total reflection phase shifter 30c and the linear polarizer ring 100a is transmitted, and is converted into an electrical signal corresponding to each light intensity by the detectors 70a to 70l.

  The electrical signals output from the detectors 70a to 70l are input to a signal processing unit configured by a microcomputer or the like, and the Stokes parameters can be determined by a known ellipsometry technique from the signal intensity ratio of the electrical signals. The tilt angle and / or azimuth angle of the recording unit of the information recording medium 300 can be specified. As a result, the recorded information can be read.

  FIG. 25C is a diagram schematically illustrating a cross section of a configuration example of the irradiation optical system and the polarization detection optical system, and the condensing lens 40a, the condensing lenses 110a to 110l, and the entire configuration illustrated in FIG. This is an example of an optical system using a collective optical element 200a in which a reflection phase shifter 30c is integrally molded. It is possible to reduce the size and cost of the optical system.

  FIG. 26 is a diagram showing another schematic configuration example of the information recording and / or reproducing apparatus according to the present invention. FIG. 26A is a cross-sectional view schematically showing a cross section of a configuration example of an irradiation optical system and a polarization detection optical system, and FIG. 26B is a total reflection phase shifter viewed from the condenser lens 40a side. 30C is a plan view schematically showing the arrangement of 30c and 30d, detectors 70a to 70l, detector holding unit 71, linear polarizer ring 100b, and condenser lenses 110a to 110l. In the figure, the same components as those in FIGS. 22 to 25 are denoted by the same reference numerals, and the description thereof is omitted.

  The information recording and / or reproducing apparatus shown in FIG. 26A includes a circularly polarized light generating means 20a, a total reflection phase shifter 30c, condensing lenses 40a, 110a to 110l, detectors 70a to 70l, a detector holding unit 71, a straight line. It is composed of a polarizer ring 100b. Reference numeral 300 denotes an information recording medium. The polarization detectors 70a to 70l may be integrated to form a detector array. In FIG. 26, circularly polarized light generating means 20a and condenser lens 40a are examples of reading light irradiating means including a light source for irradiating the recording portion of information recording medium 300 with reading light. Total reflection phase shifter 30c, 30d, condensing lenses 110a to 110l, linear polarizer ring 100b, and detectors 70a to 70l are examples of reflected light detection means for detecting reflected light reflected by the recording unit.

  In FIG. 26 (a), total reflection phase shifters 30c and 30d are optical elements whose phase angles change in accordance with the elliptically polarized light to be detected. It has the feature of increasing the degree of freedom of the set phase angle in the angle design. The linear polarizer ring 100b is a polarizer that can be combined with the total reflection phase shifters 30c and 30d to form an arbitrary elliptical polarizer, and the characteristics can be changed for each region in accordance with the elliptically polarized light to be detected. it can. The condensing lenses 110a to 110l are condensing lenses for enlarging and projecting the recording surface on the detectors 70a to 70l at an appropriate magnification.

  In FIG. 26 (a), the reading light, which is circularly polarized light generated by the circularly polarized light generating means 20a, is condensed on the recording unit (not shown) of the information recording medium 300 by the condenser lens 40a. The condensed light is reflected by the recording unit, passes through the condensing lens 40a again as elliptically polarized reflected light having recorded information, and changes its path by, for example, 90 ° by the total reflection phase shifter 30c. At 30d, the path is further changed by 90 °, for example, and enters the linear polarizer ring 100b via the condenser lenses 110a to 110l. A predetermined polarization component determined by the combination of the total reflection phase shifters 30c and 30d and the linear polarizer ring 100b is transmitted and converted into electrical signals corresponding to the respective light intensities by the detectors 70a to 70l.

  The electrical signals output from the detectors 70a to 70l are input to a signal processing unit configured by a microcomputer or the like, and the Stokes parameters can be determined by a known ellipsometry technique from the signal intensity ratio of the electrical signals. The tilt angle and / or azimuth angle of the recording unit of the information recording medium 300 can be specified. As a result, the recorded information can be read. In FIG. 26, the reading light which is circularly polarized light may be configured to be incident from the detector portion instead of the central portion.

  FIG. 27 is a diagram showing another schematic configuration example of the information recording and / or reproducing apparatus according to the present invention. FIG. 27A is a cross-sectional view schematically showing a cross section of a configuration example of the irradiation optical system and the polarization detection optical system, and FIG. 27B is a collective optical element 200b as viewed from the information recording medium 300 side. FIG. 6 is a plan view schematically showing the arrangement of detectors 70a to 70l, detector holding unit 71, and linear polarizer ring 100b. In the figure, the same components as those in FIGS. 22 to 26 are denoted by the same reference numerals, and the description thereof is omitted.

  The information recording and / or reproducing apparatus shown in FIG. 27A includes a circularly polarized light generating means 20a, a collective optical element 200b, detectors 70a to 70l, a detector holding unit 71, and a linear polarizer ring 100b. The collective optical element 200b is an optical element in which the condenser lens portion 200b1 and the total reflection phase shifter portion 200b2 are integrally molded. Reference numeral 300 denotes an information recording medium. The polarization detectors 70a to 70l may be integrated to form a detector array.

  In FIG. 27, circularly polarized light generating means 20a and collective optical element 200b are examples of read light irradiating means including a light source for irradiating the recording portion of information recording medium 300 with read light. The polarizer ring 100b and the detectors 70a to 70l are examples of reflected light detection means for detecting reflected light reflected by the recording unit.

  In FIG. 27A, a total reflection phase shifter 200b2 of the collective optical element 200b is an optical element whose phase angle changes in accordance with the elliptically polarized light to be detected. The linear polarizer ring 100b is a polarizer that can form an arbitrary elliptical polarizer by being combined with the total reflection phase shifter 200b2 of the collective optical element 200b, and has a characteristic for each region according to the elliptically polarized light to be detected. Can be changed.

  In FIG. 27A, the reading light which is circularly polarized light generated by the circularly polarized light generating means 20a is condensed on a recording unit (not shown) of the information recording medium 300 by the condensing lens unit 200b1 of the collective optical element 200b. Is done. The condensed light is reflected by the recording unit, passes through the condensing lens unit 200b1 of the collective optical element 200b again as elliptically polarized reflected light having recording information, and is a total reflection phase shifter unit 200b2 of the collective optical element 200b. The path is changed twice at, for example, 90 ° and enters the linear polarizer ring 100b. A predetermined polarization component determined by the combination of the total reflection phase shifter 200b2 of the collective optical element 200b and the linear polarizer ring 100b is transmitted and converted into electrical signals corresponding to the respective light intensities by the detectors 70a to 70l. .

  The electrical signals output from the detectors 70a to 70l are input to a signal processing unit configured by a microcomputer or the like, and the Stokes parameters can be determined by a known ellipsometry technique from the signal intensity ratio of the electrical signals. The tilt angle and / or azimuth angle of the recording unit of the information recording medium 300 can be specified. As a result, the recorded information can be read.

  FIG. 28 is a cross-sectional view showing another schematic configuration example of the information recording and / or reproducing apparatus according to the present invention. In the figure, parts that are the same as those in FIGS. 22 to 27 are given the same reference numerals, and descriptions thereof are omitted.

  The information recording and / or reproducing apparatus shown in FIG. 28 includes a circularly polarized light generating means 20a, a condenser lens 40a, a translucent mirror 30a, a polarizing beam splitter 30e, and detectors 70a and 70b. The polarization detectors 70a and 70b may be integrated to form a detector array. Further, in the optical path of the reflected light, a condensing lens may be inserted in front of the detectors 70a and 70b for enlarging and projecting the recording surface onto the detectors 70a and 70b at an appropriate magnification. The information recording medium 310 is formed with a recording unit (not shown) having a plurality of azimuth angles (inclination angles are constant) within a range of 0 ° to 90 ° representing the recorded information, and the optical system of FIG. Can detect only azimuth angles in the range of 0 ° to 90 °.

  In FIG. 28, the circularly polarized light generating means 20a, the translucent mirror 30a, and the condenser lens 40a are examples of reading light irradiation means including a light source for irradiating the recording portion of the information recording medium 310 with reading light. The beam splitter 30e and the detectors 70a and 70b are examples of reflected light detection means for detecting reflected light reflected by the recording unit. In FIG. 28, a polarization beam splitter 30e is a filter that separates incident light by its polarization component, transmits a p-polarization component, and reflects an s-polarization component.

  In FIG. 28, the reading light, which is circularly polarized light generated by the circularly polarized light generating means 20a, passes through the semi-transparent mirror 30a, and is condensed on the recording unit (not shown) of the information recording medium 310 by the condenser lens 40a. The The condensed light is reflected by the recording unit, passes through the condensing lens 40a again as elliptically polarized reflected light having recording information, changes its path by, for example, 90 ° by the semitransparent mirror 30a, and enters the polarizing beam splitter 30e. enter. Of the light entering the polarizing beam splitter 30e, the p-polarized component is transmitted and enters the detector 70a. Further, the s-polarized component is reflected and enters the detector 70b. The detectors 70a and 70b convert the signals into electrical signals corresponding to the respective light intensities.

  The electrical signal output from the detectors 70a70b is input to a signal processing unit configured by a microcomputer or the like, and the azimuth angle of the recording unit of the information recording medium 310 can be specified from the signal intensity ratio of the electrical signal. . As a result, the recorded information can be read. In FIG. 28, it is also possible to configure one detector 70a and specify the azimuth angle from the signal intensity of the electric signal detected by the detector 70a (the electric signal intensity varies depending on the azimuth angle). is there.

  As described above, the embodiments of the information recording and / or reproducing apparatus according to the present invention have been illustrated in FIGS. 22 to 28. However, the present invention is applied to various media, methods, apparatuses, and the like as described below, for example. be able to. However, it is not necessarily limited to the following application examples.

  First, the present invention relates to a read-only information recording medium and information reproducing apparatus to which the technology of CD-ROM, DVD, Blu-ray Disc (BD) is applied, and an information recording card, an information recording chip, etc. based on the same principle It can be applied to the information recording and / or reproducing apparatus. For example, it is possible to realize an information recording medium in which the recording unit on the information recording medium is constituted by two or three folded optical path reflecting surfaces, and multi-valued information is recorded using the in-plane azimuth angle as recording information. In addition, the reflected light reflected on the information recording section of the information recording medium is incident on the information recording medium substantially perpendicularly and reflected as elliptically polarized light having a predetermined ellipticity. An information recording and / or reproducing apparatus that reads recorded information by detecting and outputting the polarization state can be realized. At this time, the folded optical path reflecting surface may be configured by using total reflection, or the folded optical path reflecting surface may be configured by substantially using metal surface reflection.

  An information recording medium for recording multi-value information, wherein the recording unit on the information recording medium is composed of a single reflecting surface, and the azimuth angle of the normal to the reflecting surface and the incident angle formed by the reflecting surface are used as recording information. realizable. Reflected light that is incident on the information recording medium obliquely from the periphery and reflected perpendicularly by the recording reflecting surface is irradiated with right (left) circularly polarized light on the recording portion of the information recording medium. By detecting and outputting the polarization ellipse, it is possible to realize an information recording and / or reproducing apparatus that reads multi-value information.

  Also, it is possible to realize an information recording medium in which the recording portion on the information recording medium is configured by reflecting surfaces having different p-component and s-component intensity reflectivities, and multi-value information is recorded using the azimuth angle of the reflecting surface as recording information. In addition, the information recording portion of the information recording medium is incident on the information recording medium as non-deflected or right (left) circularly polarized light with substantially no bias, and is perpendicularly reflected from the recording reflecting surface. By detecting and outputting the elliptical azimuth angle of the elliptically polarized light, an information recording and / or reproducing apparatus that reads multi-value information can be realized.

  Second, the present invention can also be applied to an information recording medium capable of recording multilevel information. As described above, the principle of the information reproducing method according to the present invention is that the recording portion of the information recording medium is irradiated with light having a known polarization state, and the polarization state of the reflected light reflected by the recording portion corresponds to the recording information. The information recorded on the recording unit of the information recording medium is read by detecting the polarization state of the reflected light. Therefore, in order to realize a recordable information recording medium, it is sufficient to use a phenomenon that causes a change in reflection optical characteristics (specifically, Δ and Ψ) before and after recording. By forming a recording layer having, for example, a magnetic film, a liquid crystal film, a photochromic thin film, etc., by sputtering or the like on a substrate formed by FIB processing or the like. realizable. Information can be read by detecting the polarization state of the reflected light reflected by the recording unit and specifying a predetermined azimuth angle from the detected polarization state, as in the case of a read-only information recording medium. .

  Third, the present invention can be applied to a rotation sensor, an azimuth angle sensor, a deformation sensor, and the like. For example, for the purpose of detecting the rotation angle or azimuth angle of an object irradiated with light having a known polarization state, the reflection surface is a part of the object or a reflection surface attached to a part of the object with a predetermined azimuth angle. An angle sensor that identifies the angle by detecting the polarization state of the reflected polarized light can be realized.

  In addition, for the purpose of detecting the rotation angle or azimuth angle of the object, the angle sensor is composed of a sensor head unit fixedly attached to the object and a detection unit that reads the rotation angle or azimuth angle of the head unit. An angle sensor can be realized by configuring one device with a head unit that reflects or emits polarized light in a polarization state having an azimuth angle and a detection unit that detects and outputs the azimuth angle of a predetermined polarization. Here, the detection unit includes a mechanism capable of irradiating circularly polarized light, the head unit is configured by two or three folded optical path reflection surfaces, and when the circularly polarized light emitted from the detection unit is incident, You may make it detect the elliptical polarization of the specific ellipticity and azimuth angle which are reflected.

  Fourthly, the present invention can be applied to information tags such as products, information chips, door locks, and the like. For example, since multi-value recording can be performed with a V-groove formed by a simple stamper, a simple recording / reproducing method can be realized in place of the bar code recording / reading method for recording / reproducing product information. The information tag is separated by a two-dimensional imaging type polarization camera, etc., without requiring the "scanning" operation of the laser beam, which is indispensable in the barcode method, because it is a recording with a geometric shape. You can also read from. For example, the recording is made up of a predetermined number of recording portions within a predetermined area, a recording portion indicating the reference orientation of the recording portion is arranged at a specific portion, for example, four corners, and the azimuth angle of the other recording portions is set as the reference orientation. The recorded information can be obtained by accurately reading the data.

  Since this reading uses a change in the polarization state due to reflection occurring in the tag portion, it is insensitive to a change in measurement distance due to the feature of the present invention that it is resistant to disturbance. From these features, an inexpensive and easy-to-use information tag recording / reading apparatus can be configured. Furthermore, it can be applied to information search cards, information chips, and the like in which library searches and service data are recorded in detail. Since a sufficiently large amount of complicated information can be recorded on a chip-like or card-like information recording medium, it can also be applied to personal identification cards in large-scale facilities. In this case, a reading unit can be installed in the door, and a door lock using a chip or a card as a key can be configured at the same time. The key information is complex enough, but many keys can be manufactured at a low cost.

  In these applications, records need to be stored stably and reliably. In the recording method according to the present invention, information is recorded as a geometric shape on an information recording medium. Therefore, compared with other methods using a semiconductor memory using magnetic recording or electrons, the stability and storability are much superior. There is no problem even if a magnet is brought into contact (strong magnetic field), exposed to discharge or charging (strong electric field), or passed through X-ray inspection (radiation) at an airport or the like. There is no problem if it is dropped into liquids such as water, oil, detergent, etc., or dropped on the floor. It is stable and unaffected in all situations where normal people live. At the same time, erasing information can be done by simple methods such as consciously scratching the surface with sharp corners or striking with a stone. Since there is information on the shape, it is easy to recycle the material, and it is also an important advantage not to pollute the environment.

Fifth, the present invention can be applied to an information recording medium that can be recorded and reproduced without having an operating part. For example, the tilt angle (± 90 °) and azimuth angle (± 90 °) of a minute mirror are each divided by 1024 to place binary 10-bit recording information. The 1024 division corresponds to 0.176 ° with respect to 180 °. However, since the ellipsometry measurement accuracy is 0.01 ° to 0.001 °, there is sufficient angular resolution. Since the tilt angle and azimuth angle can be set independently of each other, if 1.25 bytes of multi-value recording is placed on each, 20 mirrors of binary, that is, 2.5 bytes that is 20 times the conventional method Multi-value information can be recorded. Since the area of one mirror is considered to be about the readout wavelength, if the diameter is 1/2 μm, about 1500 pieces (maximum 2000) are arranged in 1 mm, and 1500 × 1500 = 2.25 × 10 in an area of 1 mm ^{2. Six} mirrors can be placed. Accordingly, this results in a recording density of 2.5 × 2.25M = 5.6 Mbyte / mm ² . This is imaged on a two-dimensional image sensor by a magnifying optical system and read out to provide a new multi-value information recording medium. If the size of one mirror surface is matched with a magnification optical system of about 4 times according to the size of 2 μm of one pixel of a two-dimensional image sensor by a magnification optical system of about 4 times, in the current technology, the 10M pixel surface (4 mm ²⁾ 10M × 2.5 bytes = 25 Mbytes of information can be recorded and read without moving parts.

  Sixth, the present invention can be applied to reflector parts such as road signs and reflectors installed on the road surface. Essentially, it is information recording by the polarization state using the optical anisotropy between the p-s components inherent in the reflection of the inclined surface, and it can be used more actively that it is not affected by disturbance. The change in the polarization state due to reflection is sensitive to the azimuth angle and reflection angle of the reflecting surface, and there is no sensitivity to horizontal shift and vertical shift components caused by vibrations due to disturbance. Therefore, it is suitable for reading in a normal environment. For example, if the present invention is applied to a reflector such as a road sign or a reflection device installed on a road surface, information can be read from a long distance, so that a small portable reading device or an in-vehicle device information system is constructed. it can. In this case, the wavelength to be used can be arbitrarily selected. For example, it is possible to select a wavelength that is not easily affected by scattering in the optical path in the middle due to fog or the like. In addition, the irradiation unit can be standardized by using a car headlight as circularly polarized light.

  Seventh, the present invention can be applied to a rotational motion sensor suitable for precise rotational angle measurement in a normal environment. In the information recording, for example, in the recording portion of the V-groove, the rotation angle in the ridge direction corresponds 1: 1 with the principal axis direction of the ellipse of the reflected polarized light. Therefore, the rotation angle can be accurately read using the recording unit as a sensor. The accuracy of measurement is 0.01 ° to 0.001 ° in terms of Δ and ψ in a normal ellipsometry technique. In addition, as described above, the change in the incident angle due to the change in the attitude of the sensor unit is the first when the incident angle of the first surface is reduced when the right angle prism type V-groove is constituted by two reflections. The incident angle of the two surfaces is increased, and the sum of the two reflections is 90 °. As a result, the incident angle change is compensated. Therefore, it is possible to configure a sensor that is insensitive to the incident direction of light and that is specifically sensitive to the rotational direction.

  Eighth, in the present invention, the recording unit can be used as an inclination sensor by using a two-dimensional recording system such as a polarization camera as a reading device. Since time changes can be easily recorded, it is suitable for attitude control dynamics observation. In the application of tilt measurement, the observation target with the recording unit is irradiated with circularly polarized light uniformly from the periphery. Under this condition, the sensor only needs to be a reflection surface, and since the observation direction is fixed, the inclination of the reflection surface normal and the reflection angle of light can be continuously measured simultaneously. Therefore, by recording the time change, it is possible to configure a sensor for local fine deformation in the image. For example, the deformation dynamics in the observation area can be recorded and analyzed by fixing the sensor unit with a predetermined position distribution in the camera recording area and recording the deformation. It can develop into applications such as capturing precursor phenomena.

  Ninthly, the present invention can be applied to detection of deformation of the ground surface by satellite images, detection of deformation of the ocean surface, and the like. In this case, the irradiation light is sunlight from an infinite distance, and the observation is performed by reversing the light beam direction of FIG. 3, but the principle of reflection is the same. Furthermore, it can be applied to measurement by radio waves.

  10thly, this invention is applicable also to the application which observes the shape and dynamics of the liquid surface to which a recording part is miniaturized as a sensor and arrange | positioned on an interface or a surface, and other methods are difficult to apply. The interface can be generalized to a liquid in gas or a gas interface in liquid. Similarly, the application can be extended to all material interfaces that can cause reflection, such as solid-liquid interfaces, and liquids in liquids with different densities, gases in gases, solids in solids, and the like. These are objects that are impossible or difficult to measure by conventional interference measurement methods.

  Eleventh, since the present invention is a remote sensing method, the measurement and dynamics of the shape of a regular or irregular object in an environment where it is difficult to apply a normal method such as high temperature or high pressure. It can also be applied to measurement.

  In addition, all electromagnetic waves can be used in the information recording medium, information reproducing method, information recording method, information recording and / or reproducing apparatus according to the present invention. In particular, the wavelength is not limited, and white light can be used as it is. The recording unit of the information recording medium according to the present invention uses the incident angle dependency of polarized reflection. Therefore, more information can be recorded if wavelength characteristics are given to the reflection of the recording unit. Features that are not limited to wavelengths further span the entire range of electromagnetic waves, from ultraviolet light to microwaves. A necessary requirement is that the electromagnetic wave is specularly reflected on the inclined surface of the recording unit, and it is sufficient that the area of the mirror surface has at least about a wavelength.

  Thus, according to the present invention, an information recording medium for recording multilevel information with a simple configuration having a geometric shape in the recording unit, an information reproducing method corresponding to such an information recording medium, an information recording method, An information recording and / or reproducing apparatus can be provided.

  The preferred embodiment of the present invention has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made to the above-described embodiment without departing from the scope of the present invention. And substitutions can be added.

  For example, the information recording and / or reproducing apparatus according to the present invention illustrated in FIGS. 22 to 28 has a configuration that does not include a signal processing unit. However, the information recording and / or reproducing apparatus is predetermined from an electrical signal corresponding to light intensity output from the detector. A tilt angle and / or a predetermined azimuth angle may be specified, and a signal processing unit that reproduces recorded multi-value information may be included. In this case, it is a reflected light detection means including a signal processing part.

It is a figure which illustrates the elliptically polarized light reflected when a circularly polarized light is irradiated to the V groove comprised by the 45-degree inclined slope. It is a figure which shows the example of formation of the recording part which has the inclined surface formed on an information recording medium. It is a figure which shows typically the incident light and reflected light in the azimuth angle (theta) of an incident surface. It is a figure which illustrates the change by the incident angle (phi) of the polarization state of the reflected light reflected by the incident surface of various azimuth angles (theta) from Al reflective surface. It is a figure which shows the incident angle dependence of the intensity | strength reflectance of the ps component of Al reflective surface. It is a figure which illustrates the incident angle dependence of the complex amplitude reflectance ratio of the p-s component of Al surface by complex plane display. It is a figure which shows the incident angle dependence of the reflective polarization parameter of Al reflective surface. It is a figure which illustrates the phase change by twice reflection in the same incident angle on the Al surface. It is a figure which illustrates the change by the deflection angle of the polarization state by twice reflection in the Al reflective surface of 90 degrees of apex angles. It is a figure which illustrates the change by the incident angle of the polarization state in the case of oblique reflection on the dielectric surface. It is a figure which illustrates the incident angle dependence of the intensity | strength reflectance of the p-s component of Si surface. It is a figure which illustrates the incident angle dependence of the complex amplitude reflectance ratio of the p-s component of Si surface by complex plane display. It is a figure which illustrates the incident angle dependence (real part and imaginary part) of the complex amplitude reflectance ratio of the p-s component of Si surface. It is a schematic diagram which shows the structural example of a recording pit and a read-out system. It is a figure which illustrates typically the feature of signal detection concerning the present invention that detection sensitivity is high compared with the state of signal detection in the prior art. It is a figure which illustrates the incident angle dependence of the intensity | strength reflectance of the transparent recording medium of refractive index n = 2.145. It is a figure which illustrates the incident angle dependence of the complex amplitude reflectance ratio of the transparent recording medium of refractive index n = 2.145 by complex plane display. It is a figure which illustrates the incident angle dependence (real part and imaginary part) of the complex amplitude reflectance ratio of the transparent recording medium of refractive index n = 2.145. It is a schematic diagram which shows the structural example of the recording pit and reading method in the case of utilizing the reflection on the back surface of a high refractive index medium. It is a figure which shows the example of control operation | movement about one attitude | position among the micro slopes which comprise a recording part. It is a figure which shows the example of formation of the recording part which has the inclined surface and recording layer which are formed on an information recording medium. It is a figure which shows the structural example of the outline of the information recording and / or reproducing | regenerating apparatus concerning this invention. It is a figure which shows the other structural example of the outline of the information recording and / or reproducing | regenerating apparatus concerning this invention. It is a figure which shows the other structural example of the outline of the information recording and / or reproducing | regenerating apparatus concerning this invention. It is a figure which shows the other structural example of the outline of the information recording and / or reproducing | regenerating apparatus concerning this invention. It is a figure which shows the other structural example of the outline of the information recording and / or reproducing | regenerating apparatus concerning this invention. It is a figure which shows the other structural example of the outline of the information recording and / or reproducing | regenerating apparatus concerning this invention. It is a figure which shows the other structural example of the outline of the information recording and / or reproducing | regenerating apparatus concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Incident light irradiated to a recording part 2a, 2b V groove 3a, 3b incident surface 4a comprised in a recording part 4a Elliptical polarized light reflected by V groove 2a 4b Elliptical polarized light reflected by V groove 2b 5a, 5b Main axis 6 Triangular pyramid for three-time reflection 7 Slope for one-time reflection 8a, 8b Cross section of information recording medium 9a, 9b Irradiation spot irradiated to recording unit 10a-10p Recording pit arrangement and ridge direction 11a-11f Recording pit Arrangement and ridge direction 11g to 11l Recording pit arrangement 12a, 12b Image of detected signal example 13a to 13q Recording pit arrangement and ridge direction 15 Fixed portion 16, 17 Movable portion 18a Transparent protective layer 18b, 18c Dielectric 19a -19c Recording layer 20a-20c Circularly polarized light generating means 25 Light source 30a Translucent mirror 30b Total reflection prism phaser 30c, 30d Total reflection phaser 0e Polarizing beam splitter 40a-40d, 110a-110l Condensing lens 60a Horizontal linear polarizer 60b 45 ° linear polarizer 60c Linear polarizer 60c0 Circular polarizer 60c1 Phaser 60d-60g Linear polarizer 70a-70l Detector 71 Detector Holding unit 90a to 90f Polarization irradiation fiber 90g to 90l Polarization detection fiber 100a, 100b Linear polarizer ring 200a Collective optical element 200b Collective optical element 200b1 Condensing lens part 200b2 Total reflection phase retarder part 300, 310 Information recording medium

Claims (19)

An information recording medium on which multi-value information recorded on the recording unit is read by irradiating the recording unit with reading light and detecting reflected light reflected on the recording unit,
An information recording medium characterized in that the recording section has an inclined reflection surface having a predetermined area and having a predetermined inclination angle so as to form a plurality of types of azimuth angles corresponding to the multi-value information. . An information recording medium on which multi-value information recorded on the recording unit is read by irradiating the recording unit with reading light and detecting reflected light reflected on the recording unit,
The information recording medium, wherein the recording unit is formed with an inclined reflection surface having a predetermined area and having a predetermined azimuth angle so as to form a plurality of types of inclination angles corresponding to the multi-value information. . An information recording medium on which multi-value information recorded on the recording unit is read by irradiating the recording unit with reading light and detecting reflected light reflected on the recording unit,
In the recording unit, an inclined reflecting surface having a predetermined region is formed in combination so as to form a plurality of types of inclination angles and a plurality of types of azimuth angles corresponding to the multi-value information. To record information. An information recording medium on which multi-value information recorded on the recording unit is read by irradiating the recording unit with reading light and detecting reflected light reflected on the recording unit,
The information recording medium is characterized in that the recording unit is formed with one or a plurality of inclined reflecting surfaces having a predetermined area and having a predetermined azimuth angle. Multi-value information is recorded by irradiating the recording light onto the recording unit, the recording unit on which the multi-value information is recorded is irradiated with reading light, and reflected light reflected by the recording unit is detected. The multi-value information recorded in the recording unit is read by the information recording medium,
An information recording comprising one or a plurality of inclined reflecting surfaces having a predetermined inclination angle having a predetermined region, and a recording layer made of a material to which optical anisotropy is added on the inclined reflecting surface. Medium. Multi-value information is recorded by applying a recording magnetic field or a recording electric field to the recording unit, and the recording unit on which the multi-value information is recorded is irradiated with reading light and reflected by the recording unit. Is an information recording medium from which the multi-value information recorded in the recording unit is read,
An information recording comprising one or a plurality of inclined reflecting surfaces having a predetermined inclination angle having a predetermined region, and a recording layer made of a material to which optical anisotropy is added on the inclined reflecting surface. Medium.   The recording unit includes a corner cube having a predetermined inclination angle of 45 ° that forms a round-trip optical path between the three inclined reflecting surfaces, and the ridge line of the corner cube has a plurality of types of orientations corresponding to the multi-value information. 2. The information recording medium according to claim 1, wherein the information recording medium is formed to form a corner.   The recording unit includes the inclined reflection surface having the predetermined inclination angle of 30 °, and the inclined reflection surface is formed to form a plurality of types of azimuth angles corresponding to the multi-value information. The information recording medium according to claim 1.   The recording unit includes a V-groove having a predetermined inclination angle of 45 ° that forms a round-trip optical path between the two inclined reflecting surfaces, and the ridge line of the V-groove has a plurality of types of orientations corresponding to the multilevel information. 2. The information recording medium according to claim 1, wherein the information recording medium is formed to form a corner.   10. The information recording medium according to claim 1, wherein a total reflection of a dielectric is used as the inclined reflection surface.   The information recording medium according to claim 1, wherein a back surface reflection of a dielectric is used as the inclined reflection surface.   12. The information recording medium according to claim 1, wherein the recording unit is irradiated with reading light having a known polarization state, and the polarization state of the reflected light reflected by the recording unit is detected and detected. An information reproducing method for reading the multi-value information recorded in the recording unit by specifying the predetermined tilt angle and / or the predetermined azimuth angle from the polarized state.   13. The information reproducing method according to claim 12, wherein the polarization state of the reading light is circularly polarized light, and the polarization state of the reflected light is elliptically polarized light.   The reading light includes first reading light whose polarization state is right circular polarization, and second reading light whose polarization state is left circular polarization, and the first reading light and the second reading light. 14. The information reproducing method according to claim 12, wherein the reading light is irradiated so as to form a predetermined half space.   6. An information recording method for recording multi-value information on the recording layer by irradiating the recording layer of the information recording medium according to claim 5 with recording light and adding optical anisotropy to the material of the recording layer.   A multi-value information is recorded on the recording layer by applying a recording magnetic field or a recording electric field to the recording layer of the information recording medium according to claim 6 and adding optical anisotropy to the material of the recording layer. Information recording method. A reading light irradiating unit including a light source for irradiating the recording unit of the information recording medium according to any one of claims 1 to 11 with a reading light in a known polarization state, and a reflection reflected by the recording unit. Reflected light detection means for detecting the polarization state of the light,
An information recording and / or reproducing apparatus for reading multi-value information recorded in the recording unit by specifying the predetermined inclination angle and / or predetermined azimuth angle based on a detection result of the reflected light detection means.   18. The information recording and / or reproducing apparatus according to claim 17, wherein the polarization state of the reading light is circularly polarized light, and the polarization state of the reflected light is elliptically polarized light.   The reading light includes first reading light whose polarization state is right circular polarization, and second reading light whose polarization state is left circular polarization, and the first reading light and the second reading light. 19. The information recording and / or reproducing apparatus according to claim 17, wherein the reading light is irradiated so as to form a predetermined half space.

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