JP2007200394A - Optical information recording method and optical information reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording method and an optical information reproducing method improved in the reliability of holographic recording/reproducing and increased in versatility and applicability by widening the range of an operation temperature. <P>SOLUTION: The optical information recording method records interference fringes of information light and recording reference light in the hologram recording layer 2 of a recording medium by applying the information light 21 spacially modulated based on an information light space modulation pattern 12 and the recording reference light 22 formed in a reference light pattern 13 to be converged. Temperature conditions of the recording medium are detected, magnifications of the information light space modulation pattern 12 and the reference light pattern 13 in the incident pupil surface 15 of an objective lens are changed based on the temperature conditions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical information recording method and a hologram recording layer for recording information fringes by irradiating a recording medium with information light carrying information and a recording reference light by an objective lens to cause interference in the hologram recording layer of the recording medium The present invention relates to an optical information reproducing method for reproducing information from interference fringes recorded in the above.

  Holographic recording in which information is recorded on a recording medium using holography is generally performed by superimposing information light having image information and reference light inside the recording medium, and forming interference fringes generated at that time. Is done by writing to At the time of reproducing the recorded information, the image information is reproduced by diffraction by interference fringes by irradiating the recording medium with reference light.

  In recent years, volume holography, particularly digital volume holography, has been developed and attracted attention in practical areas in order to achieve ultra-high data density in holographic recording. Volume holography is a method of writing interference fringes three-dimensionally by actively utilizing the thickness direction of the recording medium. Digital volume holography is a recording medium and recording method similar to those used for volume holography. The image information to be recorded is a computer-oriented holographic recording method limited to a binarized digital pattern. In this digital volume holography, for example, image information such as an analog picture is once digitized, developed into two-dimensional digital pattern information, and recorded as image information. At the time of reproduction, the digital pattern information is read and decoded so that the original image information is restored and displayed. As a result, even if the S / N ratio (signal to noise ratio) is somewhat poor at the time of reproduction, the original information is reproduced very faithfully by performing differential detection or encoding binary data and performing error correction. It becomes possible.

  An example of recording on the hologram recording layer by volume holography is that the information light carrying the information to be recorded and the recording reference light simultaneously form a thickness direction interference fringe in the hologram recording layer for a predetermined time from the transparent substrate side. The information is recorded as a three-dimensional hologram by irradiating and fixing the interference fringe pattern three-dimensionally in the hologram recording layer (Patent Document 1 and Patent Document 2).

  Further, as an optical information recording method, there are a method in which the optical axis of the information light and the optical axis of the reference light for recording intersect with each other at a certain angle (two-beam interference method), and the information light There is a method (collinear method) in which the axis and the optical axis of the recording reference light are coaxially arranged and irradiated and interfered so as to converge from the same direction by the objective lens.

  The collinear method is regarded as promising as being more suitable for volume holography as described above (see, for example, Patent Document 3).

JP-A-2004-362750 JP 2003-99952 A Japanese Patent Laid-Open No. 10-124872

  A hologram recording layer having a sufficiently large thickness compared to the interval between interference fringes is called a thick hologram, and is distinguished from a thin hologram having the same properties as a diffraction grating. A thick hologram cannot be reproduced unless, in principle, light having the same wavelength as the recording reference light used for recording is incident from the same direction as that for recording. In other words, in order to reproduce, it is necessary to irradiate the reproduction reference light which is basically the same as the recording reference light at the time of recording.

  Since interference fringes recorded by volume holography are recorded as thick holograms, in order to reproduce the recorded information, reproduction reference light having the same wavefront as the recording reference light is irradiated in the same state as at the time of recording. I had to.

  In Patent Document 1, both information light and recording reference light are spatially modulated according to two-dimensional pattern information, and information light and recording reference light are coaxially irradiated onto a recording medium by an objective lens. It is disclosed that the formed collinear interference fringes are recorded on a hologram recording layer. Conventionally, in order to reproduce information from this hologram recording layer, the reproduction reference light is spatially modulated by the same two-dimensional pattern information at the same wavelength as the recording reference light, and the same focal point disposed at the same position. Had to be illuminated by a distance objective.

  Further, in order to record and reproduce the hologram, it is necessary to keep the temperature uniform during recording and reproduction. This is because the hologram recording layer of the recording medium expands or contracts due to a temperature change, so that the interval between recorded interference fringes becomes wide or narrow. That is, when recording is performed at a temperature higher than normal temperature, since the hologram recording layer is expanded by heat, interference fringes are recorded on the expanded hologram recording layer. When the recording medium returns to room temperature after recording the interference fringes, the expanded hologram recording layer contracts, so that the recorded interference fringes also shrink and the interval between the interference fringes becomes narrow. Conversely, when recording is performed at a temperature lower than normal temperature, interference fringes are recorded on the holographic recording layer in a contracted state. Therefore, when the temperature returns to normal temperature, the hologram recording layer expands and the recorded interference fringes spread. It is. Further, when the temperature during reproduction is high, the hologram recording layer expands, so that the interval between recorded interference fringes becomes wide.When the temperature is low, the hologram recording layer shrinks, so that the interval between recorded interference fringes becomes small. Narrow.

  In the two-beam interference type interference fringes, reproduction becomes difficult when the reproduction temperature changes by ± 2 ° C. or more compared to the recording temperature. The collinear interference fringes have a wider temperature range than the two-beam interference fringes, but are still in the range of about ± 6 ° C. In addition, since laser is used as a light source in holographic recording / reproducing, when recording / reproducing is performed continuously, the temperature of the recording medium changes due to the heat of the laser, and the interference fringes recorded on the hologram recording layer of the recording medium. There was also a possibility that the interval of would change.

  As described above, holographic recording / reproduction, which can be reproduced only at the same temperature as the recording temperature, is unreliable and lacks versatility and applicability because a practical operating temperature cannot be secured. It was a thing.

  In view of the above-described problems, the present invention provides an optical information recording method and an optical information reproduction method that improve reliability and widen the operating temperature range and improve versatility and applicability in holographic recording and reproduction. For the purpose.

  In order to achieve the above object, an optical information recording method of the present invention records information light spatially modulated by a spatial modulation pattern for information light and recording reference light formed into a reference light pattern by an objective lens. An optical information recording method for recording interference fringes between the information light and the recording reference light in a hologram recording layer of the recording medium by irradiating the medium so as to converge, wherein the temperature condition of the recording medium is set And detecting and changing the magnification of the information light spatial modulation pattern of the information light and the reference light pattern of the recording reference light on the entrance pupil plane of the objective lens based on the temperature condition. .

  Further, in the optical information recording method, it is preferable that the information light spatial modulation pattern and the reference light pattern on the entrance pupil plane are reduced when the temperature condition is increased, and are enlarged when the temperature condition is lowered. .

  Further, in the optical information recording method, the information light and the recording reference light are generated by a spatial light modulator on which the information light spatial modulation pattern and the reference light pattern are displayed, The magnification of the information light spatial modulation pattern and the reference light pattern may be changed by an optical system arranged between the spatial light modulator and the entrance pupil plane of the objective lens.

  In the optical information recording method, the information light and the recording reference light are generated by a spatial light modulator on which the information light spatial modulation pattern and the reference light pattern are displayed. The magnifications of the information light spatial modulation pattern and the reference light pattern may be changed by changing display magnifications of the information light spatial modulation pattern and the reference light pattern in the spatial light modulator. .

  Further, in the optical information recording method, the temperature condition of the recording medium may be detected by reproducing interference fringes recorded in advance on the hologram recording layer of the recording medium, or provided in the optical information recording apparatus. May be detected by a detected temperature sensor.

  Further, the optical information reproducing method of the present invention is recorded on the hologram recording layer of the recording medium by irradiating the reproducing reference light shaped into the reference light pattern so as to converge on the recording medium by the objective lens. An optical information reproducing method for reproducing information from interference fringes, wherein a temperature condition of the recording medium is detected, and the reference light pattern of the reproduction reference light on the entrance pupil plane of the objective lens based on the temperature condition The magnification is changed.

  Further, in the optical information reproducing method, it is preferable that the reference light pattern on the entrance pupil plane is reduced when the temperature condition is high and is enlarged when the temperature condition is low.

  Furthermore, in the optical information reproducing method, the reproduction reference light is generated by a spatial light modulator on which the reference light pattern is displayed, and the magnification of the reference light pattern on the entrance pupil plane is determined by the spatial light. It may be changed by an optical system arranged between the modulator and the entrance pupil plane of the objective lens.

  In the optical information reproduction method, the reproduction reference light is generated by a spatial light modulator on which the reference light pattern is displayed, and the magnification of the reference light pattern on the entrance pupil plane is determined by the spatial light. It may be changed by changing the display magnification of the reference light pattern in the modulator.

  Further, in the optical information reproducing method, the temperature condition of the recording medium may be detected by reproducing interference fringes recorded in advance on the hologram recording layer of the recording medium, or provided in the optical information recording apparatus. May be detected by a detected temperature sensor.

  In the optical information recording method of the present invention, the volume change of the hologram recording layer of the recording medium due to the temperature change can be corrected, and the interval between the interference fringes in the hologram recording layer when returning to the normal temperature state is within a certain range. Therefore, reliability can be improved. And since the operating temperature range of the optical information recording apparatus is expanded, versatility and applicability are enhanced.

  Further, in the optical information reproducing method of the present invention, since the volume change of the hologram recording layer of the recording medium due to the temperature change can be corrected and reproduced, the reliability can be improved. And since the operating temperature range of the optical information reproducing apparatus is expanded, versatility and applicability are enhanced.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. First, the optical information recording method will be described with reference to FIGS. 1 and 2, and then the optical information reproduction method will be described with reference to FIG.

  1 and 2 are diagrams for explaining the outline of the optical information recording method of the present invention. (A) is a standard temperature condition, (B) is a high temperature condition, and (C) is a low temperature condition. This is the case of temperature conditions. FIG. 1 shows the overall rays of the information beams 21a to 21c and the recording reference beams 22a to 22c. FIG. 2 shows one pixel 16a in the information beams 21a to 21c and the recording reference beams 22a to 22c. -C, the light rays 23a-c and 17a-c from 17a-c are shown. In FIGS. 1 and 2, the pattern on the entrance pupil plane 15 of the objective lens 14 is shown on the upper side, and the cross-sectional structure is shown on the lower side.

  In FIG. 1 and FIG. 2, information light 21 a to c and recording reference light 22 a to c are irradiated so as to converge on the recording medium 1 by the objective lens 14, and the information light 21 and the recording reference light 22 Interference fringes 7a to 7c formed between them are recorded on the hologram recording layers 2a to 2c of the recording medium 1. Here, the recording medium 1 shown in FIGS. 1 and 2 is provided with hologram recording layers 2a to 2c, a gap layer 3, a reflective layer 4, a substrate 5, and a protective layer 6.

  The information lights 21a to 21c are spatially modulated by the information light spatial modulation patterns 12a to 12c. For example, the information lights 21a to 21c display the information light spatial modulation patterns 12a to 12c on a spatial light modulator having a plurality of pixels arranged in two dimensions, and irradiate the display surface of the spatial light modulator with light. Is generated by

  The spatial modulation patterns 12a to 12c for information light are composed of a plurality of pixels 16 and modulate the spatial distribution of light intensity, phase, etc. by changing the intensity, phase, etc. of the cross section of the light beam for each pixel. Is. The information light spatial modulation patterns 12a to 12c include two-dimensional pattern information in which information to be recorded is coded. In FIG. 1, the spatial modulation patterns 12a to 12c for information light show only the outline, the pattern by each pixel is omitted, and in FIG. 2, only one pixel 16a to 16c is shown.

  The contours of the recording reference beams 22a to 22c are formed into reference light patterns 13a to 13c, respectively, and are formed into an annular shape in FIG. For example, the recording reference lights 22a to 22c display the reference light patterns 13a to 13c on a spatial light modulator having a plurality of pixels arranged in two dimensions, and irradiate the display surface of the spatial light modulator with light. Is generated by Further, the recording reference light can be formed by using a mask having an opening in the shape of the reference light patterns 13a to 13c. When the spatial light modulator is used, the information light spatial modulation patterns 12a to 12c are displayed on a part of the spatial light modulator and the reference light patterns 13a to 13c are displayed on the other part. Information light and recording reference light can be simultaneously generated by the spatial light modulator.

  The intensity, phase, and the like of the recording reference beams 22a to 22c may be uniform in the reference beam patterns 13a to 13c, but are spatially modulated by the pixels 17 like the information beams 21a to 21c. You can also When the recording reference beams 22a to 22c are spatially modulated, they cannot be reproduced unless the reference beams spatially modulated in the same pattern are used, and therefore can be used as a key for reproduction.

  In FIG. 1 and FIG. 2, information light 21 a to 21 c are arranged at the center on the entrance pupil plane 15 of the objective lens 14, and recording reference lights 22 a to 22 c are arranged around the information light 21 a to c. A collinear method is employed in which the axis and the optical axes of the recording reference beams 22a to 22c are located on the same line. However, the recording reference light may be arranged at the center and the information light may be arranged around the recording reference light. Alternatively, the recording reference light may be divided and arranged at the center and the circumference, and the information light may be arranged annularly between them. Also good.

The objective lens 14 irradiates the hologram recording layers 2a to 2c of the recording medium 1 so that interference fringes 7a to 7c are formed by the interference of the information beams 21a to 21c and the recording reference beams 22a to 22c. The information beams 21a to 21c and the recording reference beams 22a to 22c are irradiated so as to converge on the recording medium 1 by the objective lens 14 as shown in FIG. By the way, as shown in FIG. 2, the information light 23a-c and the recording reference light 24a-c corresponding to the pixels 16 and 17 of the information light spatial modulation patterns 12a-c and the reference light patterns 13a-c are recorded. Since the light is diffracted by the pixels 16 and 17 to generate diffracted light, it is incident on the objective lens 14 as diffused light. For this reason, since the light 23a to c and 24a to c corresponding to one pixel are converted into parallel light by the objective lens 14, the information light 21a to c and the recording reference light 22a to c arranged coaxially are the objective lens 14. Even if the same focal point is irradiated, the light 23a- _c and 24a- _c corresponding to each pixel intersect at _a certain angle [theta] _a- [theta] _c , so that the interference fringes 7a- _c can be formed. In FIG. 2, the recording reference beams 22a to 22c are also spatially modulated by the respective pixels 17. However, even when only the information beams 21a to 21c are spatially modulated, the recording reference beams 22a. Interference fringes can be formed by crossing ~ c.

  In FIG. 2, the light 23 a to c and 24 a to c corresponding to one specific pixel 16 and 17 has been described, but actually, a plurality of lights corresponding to each pixel of the information light spatial modulation patterns 12 a to 12 c. Are combined to form the information light 21a to 21c, and a plurality of lights corresponding to the respective pixels of the recording reference light 22a to 22c are combined to form the recording reference light 22a. Interference fringes are formed between the corresponding information light and the recording reference light corresponding to each pixel. The crossing angle θ differs depending on the combination of pixels, and a complicated interference fringe is formed.

  In the optical information recording method of the present invention, the information light spatial modulation patterns 12a to 12c of the information light 21a to c and the reference light patterns 13a to 13c of the recording reference light 22a to c on the entrance pupil plane 15 of the objective lens 14 are obtained. The magnification is changed based on the temperature condition of the recording medium 1. When the hologram recording layers 2a to 2c of the recording medium 1 are made of a material having a positive thermal expansion coefficient that expands due to heat, the spatial modulation pattern for information light and the reference light pattern are reduced when the temperature condition during recording is high. When the temperature condition is low, each pattern is enlarged. For a hologram recording layer having a negative coefficient of thermal expansion, the pattern may be enlarged at high temperatures and reduced at low temperatures. Since the hologram recording layers 2a to 2c of the recording medium 1 generally have a positive thermal expansion coefficient, a case where the hologram recording layers 2a to 2c have a positive thermal expansion coefficient will be described below.

  The interval δ of the interference fringes formed by the two intersecting rays depends on the intersection angle θ of the two rays. If the intersection angle θ increases, the interval δ of the interference fringes decreases, and if the intersection angle θ decreases. The interval δ of the interference fringes becomes wide.

As shown in FIG. 2A, in the case of a normal temperature condition, the light beam 23a from the specific pixel 16a in the information light 21a and the light beam 24a from the specific pixel 17a in the recording reference light 22a have an angle θ _a in crossed, forming interference fringes 7a intervals [delta] _a. In this specification, the normal temperature condition is an arbitrary temperature or a temperature range set as a standard temperature in the apparatus, and does not indicate a specific temperature.

When the temperature condition becomes higher than the standard temperature to be corrected, as shown in FIGS. 1B and 2B, normal patterns 12a and 13a are formed on the entrance pupil plane 15 of the objective lens 14. The information light spatial modulation pattern 12b and the reference light pattern 13b are reduced and displayed or imaged. When the information light spatial modulation pattern 12b and the reference light pattern 13b are reduced, as shown in FIG. 2B, a specific pixel 16b in the information light 21b and a specific pixel 17b in the recording reference light 22b , And the angle θ _b formed by the corresponding information beam 23b and recording reference beam 24b is smaller than the normal angle θ _a . As a result, the interval [delta] _b of the interference fringe 7b formed by the recording reference light 24b with the information light 23b corresponding to the pixel becomes wider than the interval [delta] _a of the normal.

Since the hologram recording layer 2b is expanded in a high temperature state, _if the interference fringes 7b having a wider interval δb than usual are recorded on the hologram recording layer 2b, then when the temperature of the recording medium 1 decreases, fringe 7b recorded with expanded holographic recording layer is contracted also shrinks, so also narrowed the interval [delta] _b, it is possible to correct the influence of the thermal expansion of the hologram recording layer 2b. Incidentally, the magnification of the information light spatial modulation pattern 12b and the reference light pattern 13b, when the temperature of the recording medium 1 after the recording is decreased to the normal temperature condition, the interval [delta] _b of the interference fringe 7b became narrow, normal is set to be the same extent as the interval [delta] _a of the recorded interference fringes 7a at temperature conditions.

When the temperature condition is lower than the standard temperature to be corrected, as shown in FIGS. 1C and 2C, normal patterns 12a and 13a are formed on the entrance pupil plane 15 of the objective lens 14. The information light spatial modulation pattern 12c and the reference light pattern 13c are enlarged and displayed or imaged. When the information light spatial modulation pattern 12c and the reference light pattern 13c are enlarged, as shown in FIG. 2C, one specific pixel 16c in the information light 21c and one specific pixel 17c in the recording reference light 22c And the angle θ _c formed by the corresponding information beam 23c and recording reference beam 24c is larger than the normal angle θ _a . As a result, the interval δ _c between the interference fringes 7 c formed by the information light 23 c corresponding to the pixel and the recording reference light 24 _c is narrower than the normal interval δ _a .

In low-temperature conditions, for holographic recording layer 2c is contracted, by recording the interference pattern 7c closely spaced [delta] _c than usual holographic recording layer 2c, then, when the temperature of the recording medium 1 is raised, interference pattern 7c recorded with contracted holographic recording layer 2c is expanded also enlarged, so even wider the interval [delta] _c, it is possible to correct the influence of the thermal shrinkage of the holographic recording layer 2c. Note that the magnification of the spatial modulation pattern 12c for information light and the reference light pattern 13c is such that when the temperature of the recording medium 1 rises to a normal temperature condition after recording, the interval δ _c of the widened interference fringes 7c becomes normal. is set to be the same extent as the interval [delta] _a of the recorded interference fringes 7a at temperature conditions.

  As described above, in the optical information recording method of the present invention, the volume change of the hologram recording layers 2a to 2c of the recording medium 1 due to the temperature change can be corrected, and the hologram recording layer when returning to the normal temperature state Since the interval between the interference fringes 7a to 7c can be within a certain range, the reliability can be improved. And since the operating temperature range of the optical information recording apparatus is expanded, versatility and applicability are enhanced.

  In FIG. 1 and FIG. 2, since the information beams 21a to c and the recording reference beams 22a to 22c are concentrated in the vicinity of the focal point of the objective lens 14, the intensity of the interference fringes increases, so that the hologram recording layers 2a to 2c. A large amount of the photosensitive material is consumed, and the multiplicity (the number of interference fringes that can be written at the same location) is reduced. Furthermore, if interference fringes with high intensity are recorded in the hologram recording layers 2a to 2c, there is a possibility that noise is generated for other interference fringes. For this reason, it is preferable to focus the objective lens 14 at a position other than the hologram recording layers 2a to 2c. In FIG. 1, a gap layer 3 is provided between the hologram recording layers 2a to 2c and the reflective layer 4, and the surface of the reflective layer 4 is focused so that a high-intensity interference fringe near the focal point is generated on the hologram recording layer 2a. -C is not recorded. Further, the size of the interference fringes in the hologram recording layer 2 can be changed depending on the position of the focal point of the objective lens 14, and the size of the interference fringes can be reduced by focusing on the surface of the reflection layer 4.

  Next, the optical information reproducing method will be described with reference to FIG. FIG. 3 is a diagram for explaining the outline of the optical information reproducing method of the present invention. (A) is a standard temperature condition, (B) is a high temperature condition, and (C) is a low temperature condition. Is the case. FIG. 3 shows the overall rays of the reproduction reference beams 25a to 25c and the reproduction beams 26a to 26c. In FIG. 3, the upper side shows the reference light patterns 18a to 18c on the entrance pupil plane 15 of the objective lens 14 and the spatial modulation patterns 19a to 19c of the reproduction lights 26a to 26c reproduced on the exit pupil plane 15, and the lower side. Indicates a cross-sectional structure.

  In FIG. 3, the reproduction reference beams 25 a to 25 c are irradiated from the objective lens 14 so as to converge on the recording medium 1, and from the interference fringes 7 a to 7 c recorded on the hologram recording layers 2 a to c of the recording medium 1. Reproduction lights 26a-c are generated. The generated reproduction lights 26a to 26c are imaged on the exit pupil plane 15 of the objective lens 14 by the objective lens 14, and then detected by detection means (not shown). Since the reproduction reference beams 25a to 25c and the reproduction beams 26a to 26c are opposite in the direction of incidence on the objective lens 14, the entrance pupil plane 15 for the reproduction reference beams 25a to 25c and the emission to the reproduction beams 26a to 26c are emitted. The pupil plane 15 is the same plane. In FIG. 3, the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description there applies mutatis mutandis.

  The contours of the reproduction reference beams 25a to 25c are formed into reference beam patterns 18a to 18c, and are formed in an annular shape in FIG. For example, the reproduction reference lights 25a to 25c display the reference light patterns 18a to 18c on a spatial light modulator having a plurality of pixels arranged in two dimensions, and irradiate the display surface of the spatial light modulator with light. Is generated by Further, the reproduction reference light can be formed by using a mask having an opening in the shape of the reference light patterns 18a to 18c. The reference light patterns 18a to 18c of the reproduction reference light 25a to c are the same as the reference light pattern of the recording reference light on which the interference fringes 7a to c are recorded.

  When the temperature condition becomes higher than the standard temperature to be corrected, as shown in FIG. 3B, the reference pupil light 15 is used for the reference light on the entrance pupil plane 15 of the objective lens 14 as shown in FIG. The pattern 18b is reduced and displayed or imaged. In a high temperature state, since the hologram recording layer 2b is expanded, the interval between the interference fringes 7b is wider than usual. When the reference light pattern 18b is reduced, as shown in FIG. 3B, the angle at which the reproduction reference light 25b is incident on the recording medium 1 is smaller than the normal angle, so that it is larger than the normal time interval. The interference fringes 7b having a wide interval can be interfered with, and the reproduction light 26b can be generated from the interference fringes 7b.

  When the temperature condition is lower than the standard temperature to be corrected, as shown in FIG. 3C, the reference pupil light 15 is used for the reference light on the entrance pupil plane 15 of the objective lens 14 as shown in FIG. The pattern 18c is enlarged and displayed or imaged. In a low temperature state, since the hologram recording layer 2c is contracted, the interval between the interference fringes 7c is narrower than usual. When the reference light pattern 18c is reduced, as shown in FIG. 3C, the angle at which the reproduction reference light 25c is incident on the recording medium 1 becomes larger than the normal angle. The interference fringes 7c having a narrow interval can be interfered with, and the reproduction light 26c can be generated from the interference fringes 7c.

  Note that the magnification of the reference light patterns 18b, c at high or low temperatures is an interference in which the angle at which the reproduction reference lights 25b, c are incident on the recording medium 1 is changed by expansion or contraction of the hologram recording layers 2b, c. What is necessary is just to adjust so that it may respond | correspond to the space | interval of the stripes 7b and c.

  As shown in FIG. 3, the spatial modulation patterns 19a to 19c of the reproduced reproduction lights 26a to 26c are also changed in magnification according to the intervals of the interference fringes 7a to c. ˜c may be detected by the detecting means, or may be detected after changing the magnification so that the spatial modulation patterns 19a to 19c have a uniform size before the detecting means.

  The temperature condition may have a certain range during recording or reproduction. For example, a range of 16 ° C. or more and less than 24 ° C. is a normal temperature condition, a range of 24 ° C. or more and less than 30 ° C. is a first high temperature condition, a range of 30 ° C. or more and less than 36 ° C. is a second high temperature condition, and a temperature of 36 ° C. or more is third. The magnification may be set by setting a range of 10 ° C. or more and less than 16 ° C. as a first low temperature condition, a range of 4 ° C. or more and less than 10 ° C. as a second low temperature condition, and a temperature of less than 4 ° C. as a third low temperature condition. The temperature range in each condition may be set from the temperature range in which recording / reproduction can be performed according to the pattern of the magnification. In addition, the method of changing a magnification according to temperature may be used.

  As described above, in the optical information reproducing method of the present invention, the volume change of the hologram recording layers 2a to 2c of the recording medium 1 due to the temperature change can be corrected and reproduced, so that the reliability can be improved. . And since the operating temperature range of the optical information reproducing apparatus is expanded, versatility and applicability are enhanced.

  In the optical information recording method and the optical information reproducing method of the present invention, the temperature condition of the recording medium is detected, and based on the temperature condition, the spatial modulation pattern for information light and / or the reference light on the entrance pupil plane of the objective lens The pattern magnification must be changed. Hereinafter, a means for detecting the temperature condition of the recording medium and a means for changing the magnification will be exemplified.

  As a means for detecting the temperature condition of the recording medium, a temperature sensor provided in the optical information recording / reproducing apparatus can be used. The temperature of the recording medium can be directly measured and detected by a temperature sensor, or the temperature in the optical information recording / reproducing device is measured, and the temperature of the recording medium or hologram recording layer is estimated from that temperature and detected indirectly. You can also

  The temperature condition of the recording medium can also be detected by reproducing interference fringes recorded in advance on the hologram recording layer of the recording medium. For example, interference fringes are recorded in the hologram recording layer of the recording medium in advance under normal temperature conditions, and the recording reference fringes are recorded on the entrance pupil plane of the reproduction reference light during recording or reproduction. If reproduction is performed by changing the magnification of the light pattern, the optimum magnification, that is, the temperature condition can be detected from the intensity of the reproduction light, the SN ratio, and the like. In addition, a plurality of interference fringes are recorded in advance by changing the temperature conditions in the hologram recording layer of the recording medium. If the reproduction reference light formed on the reference light pattern under the temperature condition is irradiated and reproduced, the optimum interference fringes can be identified from the intensity of the reproduction light, the SN ratio, etc., so when the interference fringes are recorded The temperature condition of the recording medium can be detected from the temperature condition.

  The magnification of the information light spatial modulation pattern and / or the reference light pattern on the entrance pupil plane of the objective lens is changed by changing the magnification of the information light spatial modulation pattern and / or the reference light pattern displayed on the spatial light modulator. Can be changed. For example, one pixel of the spatial modulation pattern for information light and / or the reference light pattern is displayed by 3 pixels × 3 pixels of the spatial light modulator under normal temperature conditions, and the spatial light modulator of the spatial light modulator is displayed under high temperature conditions. One pixel of each pattern may be displayed by 2 pixels × 2 pixels, and one pixel of each pattern may be displayed by 4 pixels × 4 pixels of the spatial light modulator under a low temperature condition.

  In addition, as a spatial light modulator that generates information light and recording reference light, a spatial light modulator that can change the dimensions of the pixels is used to increase the magnification of the spatial modulation pattern for information light and / or the reference light pattern. It may be changed. A liquid crystal spatial light phase modulator (for example, PAL-SLM manufactured by Hamamatsu Photonics) can be used as the spatial light modulator capable of changing the pixel dimensions.

  As another means, the magnification of the spatial modulation pattern for information light and / or the pattern for reference light on the entrance pupil plane of the objective lens is determined by an optical system disposed between the spatial light modulator and the entrance pupil plane of the objective lens. Can be changed. For example, the magnification can be changed by using a zoom lens as the optical system or by using a pair of relay lenses to increase the optical path length between the relay lenses. 4 to 7 are schematic views showing an embodiment of an optical information recording / reproducing apparatus having an optical system in which the magnification can be changed.

  4 to 6 are schematic diagrams of an optical information recording / reproducing apparatus 30 using a zoom lens. FIG. 4 shows an optical path during recording, FIG. 5 shows an optical path during reproduction, and FIG. 6 shows a recording medium. 1 shows an optical path for reading information on 1 and positioning information (hereinafter referred to as “medium information”).

  As shown in FIGS. 4 to 6, the optical information recording / reproducing apparatus 30 includes a light source 32 for recording / reproduction, a collimator lens 33, a polarization beam splitter 34, a spatial light modulator 35, a zoom lens 36, a dichroic in a pickup 31. A mirror 37, a quarter-wave plate 38, an objective lens 39, and light detection means 40 are provided. 4 to 6, the recording medium 1 has a wavelength selective reflection layer 8 in addition to the hologram recording layer 2, the gap layer 3, the reflection layer 4, the substrate 5, and the protective layer 6. The medium information is recorded or can be recorded. The pickup 31 shown in FIGS. 4 to 6 is provided with a medium information element 41 and a medium information reading light collimator lens 42.

  The pickup 31 irradiates information light and recording reference light for recording information at a specific recording position of the recording medium 1, or reproduces reference light for reproducing information from a specific reproduction position of the recording medium 1. Or the like. The pickup 31 is preferably provided so as to be movable with respect to the recording medium 1 because access to the recording position or the reproduction position becomes easy. In FIG. 4, the recording optical system and the reproducing optical system are provided in one pickup 31, but the recording pickup and the reproducing pickup may be provided separately.

  The recording / reproducing light source 32 emits light for forming information light for recording information and light for forming reference light for recording and light for forming reference light for reproduction for reproducing information. As the light source 32, for example, a semiconductor laser that generates a coherent linearly polarized light beam can be used. As the recording / reproducing light source 32, a shorter wavelength is advantageous in order to perform high-density recording, and it is preferable to employ a green laser (for example, a wavelength of 532 nm) or a blue laser (for example, a wavelength of 410 nm). A solid-state laser can also be used as the light source 32.

  The collimator lens 33 makes the divergent light bundle from the recording / reproducing light source 32 substantially parallel.

  The polarization beam splitter 34 has a semi-reflective surface that reflects or transmits linearly polarized light (for example, P-polarized light) and transmits or reflects linearly polarized light (for example, S-polarized light) perpendicular to the polarized light. In FIG. 4, the polarization beam splitter 34 reflects the light beam emitted from the recording / reproducing light source 32 toward the spatial light modulator 35, and the information light whose polarization direction is rotated 90 degrees by the spatial light modulator 35. And recording reference light is transmitted. In FIG. 5, the polarization beam splitter 34 reflects the light beam emitted from the recording / reproducing light source 32 toward the spatial light modulator 35, and the polarization direction is rotated by 90 degrees by the spatial light modulator 35. The reproduction reference light is transmitted, and the reproduction light generated from the interference fringes of the recording medium 1 is reflected toward the light detection means 40.

  As the spatial light modulator 35, a transmissive or reflective spatial light modulator that has a plurality of pixels and can modulate the phase or / and intensity of the emitted light for each pixel can be used. As the spatial light modulator 35, a DMD (digital micromirror device) or a matrix type liquid crystal element can be used. The DMD can spatially modulate the intensity by changing the reflection direction of the incident light for each pixel, or spatially modulate the phase by changing the reflection position of the incident light for each pixel. The liquid crystal element can spatially modulate the intensity and phase of incident light by controlling the alignment state of the liquid crystal for each pixel. For example, the phase of the light can be spatially modulated by setting the phase of the emitted light for each pixel to one of two values that differ from each other by π radians. 4 to 6, the spatial light modulator 35 is of a reflective type, and rotates the polarization direction of outgoing light by 90 ° with respect to the polarization direction of incident light.

  Then, if the information light spatial modulation pattern is displayed in the information light region of the display surface of the spatial light modulator 35 and the light is spatially modulated by the displayed information light spatial modulation pattern, the information light is Can be generated. The spatial modulation pattern for information light includes two-dimensional pattern information obtained by encoding information to be recorded, and is expressed by two-dimensionally arranging pixels whose attributes are changed in multiple stages. For each pixel of the spatial modulation pattern for information light, for example, the state of light such as phase and intensity is changed in multiple stages. In the following description, a method of changing the light intensity for each pixel in two steps of on (white pixel) and off (black or shaded pixel) will be described. However, the method is not limited to this method. Absent. For example, the phase of the light may be changed, or may be changed to three or more stages instead of two stages.

  Furthermore, if the reference light pattern is displayed in the reference light region of the display surface of the spatial light modulator 35 and the light is spatially modulated by the displayed reference light pattern, the recording reference light or the reproduction light Reference light can be generated. The recording reference light and the reproduction reference light may be spatially modulated or may not be spatially modulated. When the recording reference light is spatially modulated, multiple recording can be performed by changing the spatial modulation pattern of the recording reference light, and information illegality can be obtained by using the spatial modulation pattern of the recording reference light as a key. Access security can be improved. When spatially modulating the reference light, the reference light pattern displayed on the spatial light modulator 35 may be spatially modulated.

  In the spatial light modulator 35, the information light region and the reference light region are arranged so that the center of the information light region and the center of the reference light region are the same, and the optical axis of the information light and the recording reference light are coaxial. It is preferable. A spatial light modulator that generates information light and recording reference light may be provided separately. For example, the light from the light source 32 is divided by a beam splitter or the like, one light is spatially modulated by a first spatial light modulator to generate information light, and the other light is masked or second spaced. The reference light may be generated by forming a reference light pattern with an optical modulator. In this case, since the information light spatial modulation pattern and the reference light pattern need to be imaged on the entrance pupil surface 39a of the objective lens 39, a spatial light modulator that generates information light and a mask that generates reference light or The spatial light modulator is conjugated and propagated to the entrance pupil plane 39 a of the objective lens 39 by the zoom lens 36.

  The zoom lens 36 is disposed between the spatial light modulator 35 and the objective lens 39, and the pattern displayed on the spatial light modulator 35 can be enlarged or reduced on the entrance pupil plane 39a of the objective lens 39. It is arranged to make it image. In FIG. 4, the zoom lens 36 includes a pair of convex lenses 36a and 36d and a pair of concave lenses 36b and 36c movably disposed therebetween. In the state of FIG. 4, since the lenses 36a to 36d are arranged symmetrically, an equal-magnification pattern can be formed on the entrance pupil surface 39a. When enlarging the pattern, the concave lenses 36b and 36c are moved to the spatial light modulator 35 side (right side in FIG. 4), respectively, and when reducing the pattern, they are moved to the objective lens 39 side (left side in FIG. 4). .

  In FIG. 4, the zoom lens 36 is arranged so that the detection means 40 forms an image of the reproduced light pattern reproduced on the exit pupil plane 39 a of the objective lens 39 so as to be enlarged or reduced. 4 to 6, the spatial light modulator 35 and the detection means 40 are arranged so as to have a conjugate relationship. The configuration of the zoom lens 36 is not limited to the lens group shown in FIGS.

  The dichroic mirror 37 reflects the recording or reproducing light from the recording / reproducing light source 32, transmits the medium information reading light from the medium information element 41, and reads the recording or reproducing light and the medium information. It is arranged to irradiate light at the same position. 4 to 6, the wavelength λ1 of the light emitted from the recording / reproducing light source 32 and the wavelength λ2 of the light emitted from the medium information element 41 are made different so that the reflection surface of the dichroic mirror 37 has the wavelength λ1. The reflective surface that reflects the light of the wavelength and transmits the light of wavelength λ2 is employed. In this case, the recording medium 1 also has a wavelength selective reflection layer 8 that reflects the recording or reproducing light having the wavelength λ1 and transmits the medium information reading light having the wavelength λ2. Media information can be recorded, and positioning can be performed during recording or reproduction. When the medium information element 41 or the like is not provided, the dichroic mirror 37 is unnecessary.

  The quarter-wave plate 38 is a phase plate that changes the optical path difference of polarized light that vibrates in directions perpendicular to each other by a quarter wavelength. The P-polarized light (S-polarized light) is converted into circularly-polarized light by the quarter-wave plate, and when the circular-polarized light reflected by the recording medium 1 passes through the quarter-wave plate, S-polarized light (P-polarized light). ) Will be changed. By changing the polarization of the return light by the quarter-wave plate 38, the reproduction light generated at the time of reproduction can be reflected by the polarization beam splitter 34 and directed to the detection means 40.

  At the time of recording, the objective lens 39 irradiates the recording medium 1 with information light and recording reference light imaged on the entrance pupil surface 39a, and causes the hologram recording layer 2 to interfere to record interference fringes. At the time of reproduction, reproduction reference light imaged on the entrance pupil plane 39a is irradiated onto the recording medium 1, and reproduction light generated from the hologram recording layer 2 of the recording medium 1 is incident to form an image on the exit pupil plane 39a. It is something to be made.

  The light detection means 40 has a plurality of light receiving pixels, and can detect the intensity and phase of light received for each light receiving pixel. As the light detection means 40, a CCD solid-state image sensor or a MOS solid-state image sensor can be used. Further, as the light detection means 40, a smart optical sensor in which a MOS type solid-state imaging device and a signal processing circuit are integrated on one chip (for example, a document “O plus E, September 1996, No. 202, Nos. 93 to 93”). (See page 99). Since this smart optical sensor has a high transfer rate and a high-speed calculation function, it is possible to perform high-speed reproduction by using this smart optical sensor, for example, reproduction at a transfer rate on the order of G (giga) bits / second. Can be performed.

  In FIG. 4, the reflective layer 4 of the recording medium 1 includes information on the recording medium 1 such as recording capacity, recording / reproducing method, track width, address information, tracking servo information, focus servo information, etc. as medium information. Information for positioning is recorded. As shown in FIG. 4, the medium information may be recorded by pits due to the uneven shape on the surface of the reflective layer 4, or may be recorded by other methods, for example, pits having different reflectivities.

  Further, the wavelength selective reflection layer 8 reflects the recording or reproducing light having the wavelength λ1 and transmits the medium information reading light having the wavelength λ2. The wavelength selective reflecting layer 8 responds to the recording or reproducing light having the wavelength λ1. Functions as a reflective layer. When the information light, the recording reference light, the reproduction reference light, or the reproduction light reaches the reflection layer 4, it may be modulated or scattered by the medium information recorded on the reflection layer 4 and may cause recording or reproduction noise. This noise can be reduced by the wavelength selective reflection layer 8.

  In the case of using a disk-shaped recording medium as the recording medium 1 and performing recording and reproduction while rotating, a disk drive mechanism used in a CD drive or DVD drive can be used. It is also preferable because compatibility with a CD drive or a DVD drive can be easily provided. However, the shape of the recording medium 1 is not limited to a disk shape, and for example, a card shape can also be used. Further, it is preferable to record or reproduce while rotating or moving the recording medium because the transfer rate becomes faster. However, recording or reproducing may be performed while the recording medium is stopped.

  The medium information element 41 reproduces medium information recorded on the reflective layer 4 of the recording medium 1, and a light source that generates medium information reading light, for example, a semiconductor laser, and light returned from the recording medium 1. And a photodetector for receiving light. The light source of the medium information element 41 preferably does not affect the hologram recording layer 2 of the recording medium 1, and preferably has a wavelength λ2 different from the wavelength λ1 of the recording / reproducing light source 32.

  For example, as a combination of the wavelength λ1 of the information light, the recording reference light and the reproduction reference light and the wavelength λ2 of the medium information reading light, (λ1, λ2) = (410 nm, 650 nm), (410 nm, 780 nm), (532 nm, 650 nm), (532 nm, 780 nm) can be used.

  The medium information reading light collimator lens 42 has a divergent light beam emitted from the medium information element 41 as a substantially parallel light beam, but a light beam whose focal point is positioned on the reflection layer 4 by the objective lens 39. It is more preferable.

  The operation of the optical information recording / reproducing apparatus 30 will be described below. FIG. 6 is a diagram for explaining the operation when reading the medium information. In FIG. 6, only the medium information reading light is shown, but interference fringes may be recorded on the hologram recording layer 2 or information may be reproduced from the interference fringes of the hologram recording layer 2 while reading the medium information.

  The medium information reading light emitted from the medium information reading element 41 passes through the medium information reading light collimator lens 42, passes through the dichroic mirror 37 and the quarter-wave plate 38, and is applied to the recording medium 1 by the objective lens 39. Irradiated. Here, it is preferable that the medium information reading light is irradiated so as to converge on the reflection layer 4 of the recording medium 1 by the medium information reading light collimator lens 42 and the objective lens 39. The medium information reading light irradiated on the recording medium 1 passes through the protective layer 6, the hologram recording layer 2, the gap layer 3 and the wavelength selective reflection layer 8 of the recording medium 1 and is reflected by the reflection layer 4. The reflected medium information reading light is modulated by the medium information recorded on the reflection layer 4 and carries the medium information. Then, the medium information reading light passes through the wavelength selective reflection layer 8, the gap layer 3, the hologram recording layer 2 and the protective layer 6 of the recording medium 1, and the objective lens 39, the quarter wavelength plate 38, the dichroic mirror 37 and The light is detected by the photodetector of the medium information element 41 through the medium information reading light collimator lens 42, and the medium information is reproduced.

  The medium information is sent to a control means (not shown), and the control means sets the recording and reproduction conditions according to the conditions of the recording medium, or moves the pickup 31 to a specific recording position or reproduction position for positioning.

  Next, the operation when recording interference fringes on the hologram recording layer will be described with reference to FIG. First, the temperature condition of the recording medium 1 is detected from the above-described temperature sensor, interference fringes or the like recorded in advance on the recording medium 1, and a magnification corresponding to the temperature condition is selected. The detection of the temperature condition is preferably performed at the beginning of the recording, and it is preferable to detect the temperature condition periodically thereafter. Then, light is emitted from the light source 32, and the emitted light is made into a substantially parallel light beam by the collimator lens 33, reflected by the polarization beam splitter 34, and incident on the spatial light modulator 35, and the information light and the recording reference Light is generated. The information light and the recording reference light pass through the polarization beam splitter 34 and are reflected by the dichroic mirror 37 on the way, but are imaged on the entrance pupil plane 39 a of the objective lens 39 at a magnification selected by the zoom lens 36. Thereafter, the recording medium 1 is irradiated by the objective lens 39 through the quarter-wave plate 38. Here, as described above, it is preferable to focus the information light and the recording reference light on a position other than the hologram recording layer 2.

  The information light and the recording reference light irradiated onto the recording medium 1 pass through the protective layer 6 of the recording medium 1, and interference fringes between the information light and the recording reference light are recorded in the hologram recording layer 2, and the gap layer 3 is reflected by the wavelength selective reflection layer 8. The reflected information light and recording reference light pass through the gap layer 3 to record interference fringes between the information light reflected by the hologram recording layer 2 and the reflected recording reference light. It passes through and is ejected from the recording medium 1.

  Further, the operation when reproducing the interference fringes recorded on the hologram recording layer 2 will be described with reference to FIG. First, the temperature condition of the recording medium 1 is detected, and a magnification corresponding to the temperature condition is selected. The detection of the temperature condition is preferably performed at the beginning of the regeneration, and it is preferable that the temperature condition is detected periodically thereafter. The light emitted from the light source 32 is converted into a substantially parallel light beam by the collimator lens 33, reflected by the polarization beam splitter 34, and incident on the spatial light modulator 35, thereby generating reproduction reference light. The reproduction reference light passes through the polarization beam splitter 34 and is reflected by the dichroic mirror 37 halfway, but forms an image on the entrance pupil plane 39 a of the objective lens 39 at a magnification selected by the zoom lens 36. Thereafter, the recording medium 1 is irradiated by the objective lens 39 through the quarter-wave plate 38. Here, the reproduction reference light is irradiated so that the focal point is located at the same position as the focal point of the recording reference light.

  The reproduction reference light irradiated on the recording medium 1 passes through the protective layer 6 of the recording medium 1 and interferes with interference fringes recorded on the hologram recording layer 2 to generate reproduction light. Thereafter, the reproduction reference light is reflected by the wavelength selective reflection layer 8 through the gap layer 3. The reflected reproduction reference light passes through the gap layer 3 and again interferes with the interference fringes in the hologram recording layer 2 to generate reproduction light. The reproduction light exits the recording medium 1, passes through the objective lens 39, changes its polarization by the quarter-wave plate 38, is reflected by the dichroic mirror 37, passes through the zoom lens 36, and then enters the spatial light modulator 35. It is changed to the same magnification as it was displayed. Then, the light is reflected by the polarization beam splitter 34 and detected by the light detection means 40, and the information of the reproduction light is reproduced.

  FIG. 7 shows an optical information recording / reproducing apparatus 70 that can change the magnification by using a pair of relay lenses to increase the optical path length between the relay lenses. In FIG. 7, the same components as those of the recording / reproducing apparatus 30 of FIGS. 4 to 6 are denoted by the same reference numerals, and description thereof is omitted. The optical information recording / reproducing apparatus 70 of FIG. 7 has a pickup 71, and a pair of relay lenses 72 and 73 are provided between the spatial light modulator 35 and the objective lens 39.

  The pair of relay lenses 72 and 73 are arranged so as to form an image of the pattern displayed on the spatial light modulator 35 on the entrance pupil plane 39 a of the objective lens 39. That is, the distance from the spatial light modulator 35 to the first relay lens 72 is the focal length f1 of the first relay lens 72, and the distance from the second relay lens 73 to the entrance pupil plane 39a of the objective lens 39 is the first. And the distance between the first and second relay lenses 72 and 73 is the sum of the focal length f1 of the first relay lens 72 and the focal length f2 of the second relay lens 73. It is arranged to be.

  Further, the pickup 71 is provided with a moving portion 74 in which optical components from the second relay lens 73 to the objective lens 39 are arranged, and the distance between the pair of relay lenses 72 and 73 can be changed. It is. In FIG. 7, in addition to the second relay lens 73, the dichroic mirror 37, the quarter-wave plate 38, and the objective lens 39, the moving unit 74 includes a medium information element 41 and medium information reading light. A collimator lens 42 is also arranged.

  In the pickup 71 of FIG. 7, when the pattern is enlarged, the moving unit 74 is moved in the direction of increasing the distance between the pair of relay lenses 72 and 73 (left in FIG. 7). The moving unit 74 may be moved (right in FIG. 7). Note that the moving distance of the moving unit 74 is set in accordance with the magnification, but can be imaged on the entrance pupil plane 39a of the objective lens 39 within the range of the focal depth of the second relay lens 73. Therefore, it is preferable.

  7 is basically the same as the operation of the optical information recording / reproducing apparatus 30 in FIGS. 4 and 5, and the optical information recording / reproducing apparatus 70 in FIG. 4 and FIG. In the optical information recording / reproducing apparatus 70 in FIG. 7, the reproduction apparatus 30 changes the magnification by changing the distance between the pair of relay lenses 72 and 73 by the moving unit 74. It is different.

  In addition, this invention is not limited to the said embodiment, It can change as needed.

(A) is a standard temperature condition, (B) is a high temperature condition, and (C) is a schematic explanatory diagram of the optical information recording method of the present invention under a low temperature condition. (A) is a standard temperature condition, (B) is a high temperature condition, and (C) is a schematic explanatory diagram of the optical information recording method of the present invention under a low temperature condition. (A) is a standard temperature condition, (B) is a high temperature condition, (C) is a schematic explanatory diagram of the optical information reproducing method of the present invention under a low temperature condition. Schematic configuration diagram for explaining the operation during recording in one embodiment of the optical information recording / reproducing apparatus of the present invention FIG. 1 is a schematic configuration diagram for explaining an operation during reproduction in an embodiment of the optical information recording / reproducing apparatus of the present invention. Schematic configuration diagram for explaining the operation at the time of reading medium information in one embodiment of the optical information recording / reproducing apparatus of the present invention Schematic configuration diagram showing another embodiment of the optical information recording / reproducing apparatus of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording medium 2 Hologram recording layer 12 Spatial modulation pattern 13 for information lights Reference pattern 14 Objective lens 15 Entrance pupil surface 21 Information light 22 Reference light for recording

Claims (12)

The hologram of the recording medium is irradiated with the information light spatially modulated by the spatial modulation pattern for information light and the recording reference light formed into the reference light pattern so as to converge on the recording medium by the objective lens. An optical information recording method for recording interference fringes between the information light and the recording reference light in a recording layer,
Detecting the temperature condition of the recording medium;
The optical information recording characterized by changing the magnification of the information light spatial modulation pattern of the information light and the reference light pattern of the recording reference light on the entrance pupil plane of the objective lens based on the temperature condition Method.   2. The light according to claim 1, wherein the spatial modulation pattern for information light and the reference light pattern on the entrance pupil plane are reduced when the temperature condition is high, and are enlarged when the temperature condition is low. Information recording method. The information light and the recording reference light are generated by a spatial light modulator on which the information light spatial modulation pattern and the reference light pattern are displayed,
The magnification of the spatial modulation pattern for information light and the reference light pattern on the entrance pupil plane is changed by an optical system disposed between the spatial light modulator and the entrance pupil plane of the objective lens. The optical information recording method according to claim 1 or 2, characterized in that: The information light and the recording reference light are generated by a spatial light modulator on which the information light spatial modulation pattern and the reference light pattern are displayed,
The magnification of the spatial modulation pattern for information light and the reference light pattern on the entrance pupil plane is changed by changing the magnification of display of the spatial modulation pattern for information light and the reference light pattern on the spatial light modulator. 3. The optical information recording method according to claim 1, wherein the optical information recording method is changed.   5. The light according to claim 1, wherein the temperature condition of the recording medium is detected by reproducing an interference fringe recorded in advance on the hologram recording layer of the recording medium. Information recording method.   6. The optical information recording method according to claim 1, wherein the temperature condition of the recording medium is detected by a temperature sensor provided in the optical information recording apparatus. An optical information reproducing method for reproducing information from interference fringes recorded on a hologram recording layer of the recording medium by irradiating the reference light for reproduction shaped into a reference light pattern so as to converge on the recording medium by an objective lens Because
Detecting the temperature condition of the recording medium;
An optical information reproducing method, wherein the magnification of the reference light pattern of the reproduction reference light on the entrance pupil plane of the objective lens is changed based on the temperature condition.   The optical information reproducing method according to claim 7, wherein the reference light pattern on the entrance pupil plane is reduced when the temperature condition is increased, and is enlarged when the temperature condition is decreased. The reproduction reference light is generated by a spatial light modulator on which the reference light pattern is displayed,
9. The magnification of the reference light pattern on the entrance pupil plane is changed by an optical system disposed between the spatial light modulator and the entrance pupil plane of the objective lens. The optical information reproducing method according to 1. The reproduction reference light is generated by a spatial light modulator on which the reference light pattern is displayed,
9. The magnification of the reference light pattern on the entrance pupil plane is changed by changing a magnification of display of the reference light pattern on the spatial light modulator. Optical information reproduction method.   11. The light according to claim 7, wherein the temperature condition of the recording medium is detected by reproducing interference fringes recorded in advance on the hologram recording layer of the recording medium. Information reproduction method. The optical information reproducing method according to claim 7, wherein the temperature condition of the recording medium is detected by a temperature sensor provided in the optical information recording apparatus.

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