JP4355585B2 - Personal authentication method, personal authentication system, and optical information recording medium - Google Patents

Description

  The present invention relates to an optical information recording medium in which personal authentication information is recorded as a hologram, a personal authentication method and a personal authentication system using the optical information recording medium.

  In a system using a credit card or a bank cash card, the card owner (user) is identified from the identification number (ID) information such as the membership number, name and affiliation written on the card, and the card reading terminal Whether the user is the cardholder himself, that is, authentication is performed based on the personal identification number or password entered by the operator (user).

  On the other hand, with the development of information technology in recent years, not only system developers but also the information technology of anti-social organizations that try to exploit this has become more sophisticated, and the damage caused by unauthorized use due to card theft, forgery, and decryption of PIN numbers has increased rapidly. ing.

  As countermeasures, technologies such as encryption of information described on a card and the like, biometric authentication using biometric information such as fingerprints and iris patterns have been developed.

  For example, Patent Document 1 discloses an IC card that holds security information in the form of a hologram or the like that is different from magnetically recorded ID information.

  Patent Document 2 discloses an authentication system that transmits biometric authentication information to an IC card for verification.

Japanese Patent No. 3475304 JP 2001-67399 A

  The IC card of Patent Document 1 is obtained by pasting an image obtained by encoding security information on an IC card as a hologram. When this encoding method is stolen, security information is easily extracted from the hologram. There is a problem that.

  Further, the IC card disclosed in Patent Document 2 also has a problem that authentication information can be extracted from the IC card if the data encoding algorithm is recognized.

  Further, the authentication system for the ID card as described above can improve safety by using advanced encryption technology, but on the other hand, the amount of information processing necessary for system operation and the infrastructure for it are large. There is a trade-off that the scale is reduced and the convenience is reduced.

  The present invention has been made in view of the above problems, and can easily change the security level without significantly changing the scale of the system and the amount of information processing compared to the conventional system, and can extract authentication information. An object of the present invention is to provide an optical information recording medium, a personal authentication method, and a personal authentication system that are extremely difficult.

  As a result of diligent research, the present inventor, when recording information with reference light and object light on an optical information recording medium such as an IC card having a holographic recording section, converts the reference light into user biometric information. Based on the encryption authentication information for recording based on the above, spatial light modulation is performed by reproducing biometric information directly from the user during reproduction, and the reference light for reproduction is spatially modulated by the encrypted authentication authentication information obtained thereby. , It is very difficult to extract authentication information by a system that verifies whether or not the user is authentic from the playback information at that time, and the security level can be easily changed without significantly changing the scale of the system. I understood that I could do it.

  That is, the following object can be achieved by the present invention described below.

(1) The holographic recording unit of an optical information recording medium having a holographic recording unit is irradiated with object light and reference light that are spatially modulated according to information to be recorded, and information is recorded by the interference fringes. And a personal authentication method for authenticating the user by irradiating the interference fringes with the reference light for reproduction to reproduce the object light, and at the time of recording the information, the user The reference light is spatially modulated by the encrypted authentication information for recording based on the biometric information of the information, and at the time of reproduction, the reference for reproduction is obtained by the encrypted authentication information for verification based on the biometric information obtained directly from the user. the light modulating spatial light, said by imaging the predetermined coding scheme biometrics information, to form the recording enciphered authentication information and the collation encrypted authentication information This image is used as a modulation pattern of reference light and reproduction reference light, and the encoding method divides an original image displaying biometric information into a plurality of pixel blocks each including a plurality of pixels, and Detecting the number of ON pixels or OFF pixels in each pixel block, and converting the pixels in each pixel block in advance for each number of ON pixels or OFF pixels according to the detected number into a pixel pattern, the steps of the bitmap image representing the recording enciphered authentication information and the collation encrypted authentication information, personal authentication method comprising Tona Rukoto.

(2) the pixel block, and consists of six or more even number of pixels, the conversion pixel pattern is described wherein the ON pixels and OFF pixels are set to be equal (1) Personal authentication method.

( 3 ) The personal authentication method according to (1) or ( 2), wherein the reference light and the reproduction reference light are subjected to phase spatial light modulation.

( 4 ) A holographic recording unit is provided, and the holographic recording unit is responsive to the reference light that is spatially light-modulated by the recording authentication information based on the biometric information of the user and the information to be recorded. An optical information recording medium on which a hologram is formed by interference fringes at the time of irradiation of object light that has been subjected to spatial light modulation, a biometric information sensor capable of acquiring biometric information directly from the user, An information processing apparatus using biometric information acquired by an information sensor as verification authentication authentication information, and diffracted light generated by irradiating the holographic recording unit with reference light for reproduction similar to the reference light at the time of recording A reproduction optical system that reproduces the recorded information, and a spatial light modulator that modulates the reproduction reference light using the verification encryption authentication information. Based on the information reproduced by the reproducing optical system, as well as checking whether the user is correct, it has a, an arithmetic unit for outputting a signal allowing or rejecting users by matching result The recording encryption information and the verification encryption information are modulation patterns obtained by imaging the biometric information by a predetermined encoding method, and the recording encryption information and the verification encryption information. The encryption information is obtained by dividing the original image displaying the biometric information into a plurality of pixel blocks each including a plurality of pixels, and detecting the number of ON pixels or OFF pixels in each pixel block. For each block, a bitmap formed by converting into a conversion pixel pattern set in advance for each number of ON pixels or OFF pixels according to the detected number. Personal authentication system that characterized in that it is a flop image.

( 5 ) The personal authentication system according to ( 4 ), further comprising hardware that allows or rejects a user based on a signal indicating permission or rejection from the arithmetic device.

( 6 ) The biological information sensor, the information processing device, the reproduction optical system, and the spatial light modulator are provided on the client server side, and the arithmetic device is provided on the host server side. The client server and the host server are provided ( 4 ) or ( 5 ), wherein the connection is made by a line, the reproduced personal authentication information is output from the client server, and the permission or rejection signal is output from the host server. ) Personal authentication system.

(7) the pixel block, and consists of six or more even number of pixels, the conversion pixel pattern is described wherein the ON pixels and OFF pixels are set to be equal (6) Personal authentication system.

( 8 ) The personal authentication system according to any one of ( 4 ) to ( 7 ), wherein the hologram is an interference fringe between object light and phase spatial light modulated reference light.

( 9 ) It has a holographic recording unit, and the holographic recording unit is based on the reference light that is spatially light-modulated by the encryption authentication information for recording based on the biometric information of the user and the information to be recorded. A modulation pattern formed by imaging the biometric information by a predetermined encoding method, wherein a hologram is formed by interference fringes at the time of irradiation of the spatially modulated object light. The recording encryption information is obtained by dividing the original image displaying the biometric information into a plurality of pixel blocks each including a plurality of pixels, and the number of ON pixels or OFF pixels in each pixel block. For each pixel block, a conversion image set in advance for each number of ON pixels or OFF pixels according to the detected number is detected. The optical information recording medium, which is a bitmap image that is formed by converting the pattern.

(10) the pixel block, and consists of six or more even number of pixels, the conversion pixel pattern is described wherein the ON pixels and OFF pixels are set to be equal (9) Optical information recording medium.

( 11 ) The optical information recording medium according to ( 9 ) or ( 10), wherein the hologram is an interference fringe between an object beam and phase spatial light modulated reference beam.

  In the present invention, when personal authentication information is recorded and reproduced as a hologram, the user's biometric information is used as encrypted authentication information, and the reference light during recording and reproduction is spatially modulated based on this information. Therefore, the extraction of authentication information by a third party is very difficult, and the security level can be easily changed without significantly changing the scale of the system or the like as compared with the conventional system.

  When irradiating the holographic recording part of the optical information recording medium with the object light and the reference light, the reference light is spatially light-modulated by the encrypted authentication information for recording based on the biometric information of the user, and at the time of reproduction, The reproduction reference light is spatially modulated by the verification encryption authentication information based on the biometric information directly obtained from the user, and it is determined whether the user is authentic or not by the diffracted light generated from the hologram. The information is imaged by a predetermined encoding method and is used as the encryption authentication information for recording and the encryption authentication information for verification, thereby achieving the above object.

  Next, the personal authentication system according to the first embodiment of the present invention will be described.

  As shown in FIG. 1, the personal authentication system 10 includes an optical information recording medium 12 having a holographic recording unit 13 capable of forming a hologram, such as an IC card, and a fingerprint, iris pattern, voiceprint, A biometric information sensor 14 capable of acquiring biometric information such as a vein pattern, an information processing device 16 using the biometric information acquired by the biometric information sensor 14 as verification authentication authentication information, and the holographic recording A reproduction optical system 18 that reproduces information recorded from the generated diffracted light by irradiating the reference light for reproduction to the unit 13, and phase space light that modulates the reproduction reference light with the verification authentication information for verification Whether the user is correct based on the information reproduced by the modulator 28 (see FIG. 3) and the reproduction optical system 18 (see FIG. 3). With matching or is configured to have the arithmetic unit 22 for outputting a signal allowing or rejecting users by matching result.

  Reference numeral 23 in FIG. 1 denotes a loading device for mounting or removing the card-like optical information recording medium 12. 1 indicates a card insertion slot for inserting the optical information recording medium 12.

  As shown in FIG. 2, the optical information recording medium 12 has the holographic recording unit 13 embedded in a card substrate 12A. The holographic recording unit 13 is configured by laminating a hologram protective layer 13A, a hologram information layer 13B, and an absorption layer 13C from the reproduction reference light incident side. In FIG. 2, reference numeral 12B denotes a printed layer, and 12C denotes a coating layer.

  The reproduction optical system 18 irradiates the holographic recording unit 13 with reproduction reference light. As shown in FIG. 3, the reproduction optical system 18 emits a laser light source 24 composed of, for example, a laser diode and the laser light source 24. A beam expander 26 for enlarging the beam diameter of the laser light, the phase spatial light modulator 28 for phase-modulating the laser light with the expanded beam diameter, a mirror 30, and a focal point of the optical information recording medium 12. And a Fourier lens 32 for Fourier transforming the reproduction reference light reflected by the mirror 30 from the Fourier lens 32 side to the holographic recording unit 13 side. With respect to the polarizing beam splitter 34 and the quarter wave plate 36 arranged in order, The imaging lens 38 and the imaging device 40 arranged on the reflection optical path to the side of the light incident from the quarter wavelength plate 36 side, and the signal obtained by the imaging device 40 are processed to reproduce the image. And a signal processing device 41.

  FIG. 4 shows a polarizing beam splitter 34, a quarter-wave plate 36, and the optical information recording medium 12 in the reproducing optical system 18.

  Next, the reference light is spatially modulated on the holographic recording unit 13 of the optical information recording medium 12 by using the recording authentication authentication information based on the biometric information of the user, and interference is caused by irradiation of the reference light and the object light. An apparatus and process for forming a hologram by fringes will be described.

  As shown in FIG. 5, the optical information recording device 42 for forming a hologram in the holographic recording unit 13 of the optical information recording medium 12 includes a laser light source 44 and laser light emitted from the laser light source 44. In the beam expander 46 for expanding the beam diameter, the mirror 48 for reflecting the laser beam whose beam diameter has been expanded, the polarization beam splitter 50 on which the reflected light from the mirror 48 is incident, and the polarization beam splitter 50 The reference optical system 52 that guides the reflected laser light as recording reference light to the holographic recording unit 13 and the laser light transmitted through the polarization beam splitter 50 as object light from the opposite side to the recording reference light. An object optical system 54 for guiding to the holographic recording unit 13, and a phase spatial light modulator 5 for modulating the recording reference light An amplitude spatial light modulator 58 that modulates the object light, an information processing device 57 for inputting encrypted authentication information for recording based on user biometric information to the phase spatial light modulator 56, and a holographic And a recording control device 59 that outputs a signal to be modulated based on information such as personal information to be recorded in the recording unit 13 to the amplitude spatial light modulator 58. In FIG. 5, reference numeral 52A denotes a quarter-wave plate, 52B and 54A denote Fourier lenses, and 52C, 54B and 54C denote mirrors, respectively.

  Next, the process of modulating the recording reference light in the phase spatial light modulator 56 will be described with reference to FIG.

  First, biometric information such as fingerprints, iris patterns, vein patterns, voiceprints, and the like of the legitimate owner (user) of the optical information recording medium 12 is acquired by the biometric information sensor 14, and the interface 17 displays, for example, as shown in FIG. Assume that an original image 60 to be obtained is obtained.

  The original image 60 is converted by the information processing device 57 into pixel blocks each consisting of four pixels by the conversion pixel pattern indicated by reference numeral 62, and the bit as recording authentication authentication information indicated by reference numeral 64. Map image.

  The conversion by the conversion pixel pattern 62 will be described in more detail. This conversion pixel pattern 62 is the number of ON pixels shown in white in the figure in a pixel block consisting of four pixels in the original image 60. Corresponding to 0, 1, 2, 3 or 4 is set in advance.

  Accordingly, for example, a pixel block consisting of four pixels in the upper left corner of the original image 60 has two ON pixels, and is thus replaced with a pixel pattern indicated by “2” in the conversion pixel pattern 62.

  As a result, the original image 60 is converted into a bitmap image 64. Further, in the phase spatial light modulator 56 in the optical information recording device 42, the recording reference light is phase-modulated by the bitmap image 64 (encryption information for recording) by the information processing device 57, and in this state, the recording is performed. The holographic recording unit 13 is irradiated with the object light on which information to be placed is placed, and a hologram with interference fringes is formed here.

  The information processing device 16 also converts the original image obtained from the biometric information sensor 14 using the same conversion pixel pattern 62 as that used for recording in the optical information recording device 42 to obtain verification encrypted information. The bitmap image is obtained.

  Next, the process of personal authentication of the user of the optical information recording medium 12 will be described.

  First, the biometric information similar to that at the time of recording is directly acquired from the user by the biometric information sensor 14, and this is converted into an original image similar to the above by the information processing device 16. The original image is converted to form a bitmap image similar to the above.

  Next, the information processing device 16 phase-modulates the reproduction reference light by the phase spatial light modulator 28 based on the bitmap image, and makes the reference beam incident on the polarization beam splitter 34.

  The reproducing reference light that has entered the polarization beam splitter 34 passes through the quarter-wave plate 36 and enters the holographic recording unit 13, and generates diffracted light in the reverse direction. The diffracted light passes through the quarter-wave plate 36, is reflected by the polarization beam splitter 34, passes through the imaging lens 38, and enters the imaging device 40. The information processing device 16 converts the diffracted light into object light during recording. Corresponding object light is reproduced.

  In the arithmetic unit 22, if the reproduction is incomplete, it is determined that the authentication is impossible. If the reproduction is possible, the user is authenticated as a genuine user, and the signal is output to the outside through the interface 17.

  Even if the information of the bitmap image 64 is illegally acquired by a third party, the original image 60 cannot be specified from the bitmap image 64.

  That is, the original image 60 is always converted into a specific bitmap image 64 by the conversion pixel pattern 62. Even if the bitmap image 64 is given and the encoding method by the conversion pixel pattern 62 is known, the original image 60 is converted. The conversion pixel pattern 62 cannot uniquely return to the original image 60. This means that “1: many” image conversion is established, and biological information cannot be extracted from the hologram.

  When reproducing a hologram, it is necessary to display the image displayed on the phase spatial light modulator 56 at the time of recording again on the phase spatial light modulator 28. As described above, biographies such as fingerprints and irises are used. It is possible only by imaging the metric information by a predetermined encoding method and using this image as a modulation pattern of the reproduction reference light.

  Therefore, even if any of the three of biometric information, encoding method, and hologram is missing, normal reproduction cannot be performed, so that data safety is high. In the first embodiment, the phase spatial light modulators 56 and 28 are used during recording and reproduction, but this may be an amplitude spatial light modulator. That is, even if the reference light is amplitude-modulated, it is difficult to restore the original biometric information from only the hologram.

  When phase spatial light modulation is used, it is impossible to restore the original biometric information. This is because the phase information of light is not a physical quantity that can be observed independently, but can be visualized only by interference with coherent light, and there are innumerable phase modulation patterns that irradiate the same interference pattern. .

  Even when the reference light is amplitude-modulated, in order to visualize it, it is necessary to know the recorded information and its encoding method, which is not easy. Furthermore, when biometric information is converted into a bitmap image by an amplitude modulation method, the above-mentioned “1: many” correspondence can be used to make the conversion irreversible in practice.

  In the first embodiment, the image block at the time of image conversion is composed of four pixels, but the present invention is not limited to this. For example, as shown in FIG. The pixels may be a single pixel block. Further, an even number of pixels of 8 or more may be used as one pixel block.

  In the second embodiment, the bitmap image indicated by reference numeral 65 is encoded based on the conversion pixel pattern indicated by reference numeral 63 in accordance with the number of ON pixels in every six pixel blocks in the original image 60. To form.

  The conversion pixel pattern 63 is set so that the number of ON pixels and OFF pixels is the same, and in the holographic recording / reproduction, the uniformity of the light amounts of the recording reference light and the reproduction reference light can be satisfied. .

  This is because if the number of ON pixels in the bitmap image 65, that is, the amount of light of the entire reference light is changed, the interference fringe contrast due to the reference light and the signal light (object light) is lowered to prevent good recording. The contrast necessary for good recording / reproduction, that is, the allowable variation in the number of ON pixels depends on the design of the optical system and the recording medium, the necessary recording density, and the data transfer rate.

  In the second embodiment, since the conversion pixel pattern 63 includes three ON pixels and three OFF pixels, the converted bitmap image 65 is constant regardless of the number of ON pixels in the original image 60. Of ON pixels (50% of all pixels).

  The pixel block is composed of six pixels, but this may be an even number of 6 or more. As the pixel block size is larger, the confidentiality of biometric information (original image) is improved.

  Next, a third embodiment of the present invention shown in FIG. 8 will be described.

  The personal authentication system 70 according to the third embodiment includes a client server 72 including the biological information sensor 14, the information processing device 16, the reproduction optical system 18, and the spatial light modulator 20 similar to those in the first embodiment, and the client The host server 76 is connected to the server 72 via a line 74.

  Based on the information reproduced by the reproduction optical system 18, the host server 76 collates whether or not the user is correct, and outputs a signal for accepting or rejecting the user based on the collation result. And a database 79.

  The client server 72 is provided with hardware 80 that accepts or rejects a user in response to an allowance or rejection signal from the computing device 78. The hardware 80 is, for example, a gate that performs entry / exit management, a bank cash dispenser, or the like.

  In the personal authentication system 70, the process of acquiring the original image 60 from the user's biometric information and forming a bitmap image with the conversion pixel pattern is the same as in the first embodiment.

  The basic configuration of the personal authentication system 70 is the same as that of the personal authentication system 10 of the first embodiment. However, the ID information taken into the playback optical system 18 as a playback image on the client server 72 side is processed again as information processing. It is sent to the device 16, undergoes signal processing such as error correction and decoding, and is sent as digital information to the host server 76 via the line 74, and the user is verified in the arithmetic device 78.

  The result is output from the arithmetic unit 78 via the line 74. When the user is permitted, the hardware 80 is operated, and when the user is rejected, the notification is made through the interface.

  Here, in general, it is a network line such as the line 74 that has a high risk of information leakage, but only the ID information and the operation instruction command are communicated through the line 74 as described above. Therefore, there is no possibility that the authentication information is eavesdropped at least.

1 is a block diagram showing a personal authentication system according to Embodiment 1 of the present invention. Sectional drawing which shows typically the optical information recording medium used in the personal authentication system Optical system diagram showing a reproducing optical system for reproducing and authenticating a hologram of an optical information recording medium in the first embodiment A perspective view showing a part of the reproducing optical system and an optical information recording medium Optical system diagram showing an optical information recording apparatus for forming a hologram on the optical information recording medium The top view which shows typically the process in which the original image obtained with the optical information recording device and the spatial light modulator of the reproducing optical system is encoded to form a bitmap image In Example 2, the top view which shows typically the process in which an original image is encoded and a bitmap image is formed Block diagram showing a personal authentication system according to a third embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,70 ... Personal authentication system 12 ... Optical information recording medium 13 ... Holographic recording part 14 ... Biological information sensor 16 ... Information processing apparatus 18 ... Reproduction optical system 22, 78 ... Calculation apparatus 28, 56 ... Phase spatial light modulator 40 ... Image sensor 42 ... Optical information recording device 57 ... Information processing device 58 ... Amplitude spatial light modulator 59 ... Recording control device 60 ... Original image 62, 63 ... Conversion pixel pattern 64, 65 ... Bitmap image 72 ... Client server 74 ... Line 76 ... Host server 80 ... Hardware

Claims (11)

Irradiating the holographic recording unit of the optical information recording medium having the holographic recording unit with object light and reference light that are spatially modulated in accordance with information to be recorded, and recording information by the interference fringes; and , A personal authentication method for authenticating a user by irradiating the interference fringes with reference light for reproduction to reproduce object light,
At the time of recording the information, the reference light is spatially light modulated by the encryption authentication information for recording based on the biometric information of the user, and at the time of reproduction, verification based on the biometric information directly obtained from the user The reproduction reference light is spatially modulated by the encryption authentication information for use ,
The biometric information is imaged by a predetermined encoding method to form the recording encryption authentication information and the verification encryption authentication information, and this image is modulated with reference light and reproduction reference light. As a pattern,
The encoding method includes dividing an original image displaying biometric information into a plurality of pixel blocks including a plurality of pixels and detecting the number of ON pixels or OFF pixels in each pixel block. When,
The pixels in each pixel block are converted into a conversion pixel pattern set in advance for each number of ON pixels or OFF pixels according to the detected number, and the encryption authentication information for recording and the encryption for verification are converted. A process of making a bitmap image representing authentication information;
Personal authentication method which is characterized in Tona Rukoto. In claim 1 ,
The pixel block is composed of an even number of pixels of 6 or more, and the conversion pixel pattern is set so that the number of ON pixels and OFF pixels is the same. In claim 1 or 2 ,
A personal authentication method, wherein the reference light and the reference light for reproduction are subjected to phase spatial light modulation. The holographic recording unit includes a reference light that is spatially light-modulated by the encryption authentication information for recording based on the biometric information of the user and a spatial light according to the information to be recorded. An optical information recording medium on which a hologram is formed by interference fringes when irradiated with modulated object light;
A biometric information sensor capable of acquiring biometric information directly from the user;
An information processing apparatus using biometric information acquired by the biometric information sensor as verification authentication authentication information;
A reproduction optical system that reproduces the recorded information from diffracted light generated by irradiating the holographic recording unit with a reproduction reference light similar to the reference light at the time of recording,
A spatial light modulator that modulates the reproduction reference light with the verification encryption authentication information;
Based on the information reproduced by the reproduction optical system, it is verified whether or not the user is correct, and an arithmetic device that outputs a signal that allows or rejects the user according to the verification result;
Ri name have,
The recording encryption information and the verification encryption information are modulation patterns obtained by imaging the biometric information by a predetermined encoding method,
The recording encryption information and the verification encryption information are obtained by dividing an original image displaying the biometric information into a plurality of pixel blocks each including a plurality of pixels, and the ON pixels or Bitmap image formed by detecting the number of OFF pixels and converting each pixel block into a conversion pixel pattern preset for each number of ON pixels or OFF pixels in accordance with the detected number personal authentication system that characterized in that it is. In claim 4 ,
A personal authentication system comprising hardware for accepting or rejecting a user in response to an acceptance or rejection signal from the computing device. In claim 4 or 5 ,
The biological information sensor, the information processing device, the reproduction optical system, and the spatial light modulator are provided on the client server side, and the arithmetic device is provided on the host server side, and the client server and the host server are connected by a line. The personal authentication system is characterized in that the reproduced personal authentication information is output from a client server, and the acceptance or rejection signal is output from a host server. In claim 6 ,
The personal authentication system, wherein the pixel block is composed of an even number of pixels of 6 or more, and the conversion pixel pattern is set so that the number of ON pixels and OFF pixels is the same. In any of claims 4 to 7 ,
The hologram is an interference fringe between an object beam and phase spatial light modulated reference beam. The holographic recording unit includes a reference light that is spatially modulated by the encryption authentication information for recording based on the biometric information of the user and a spatial light based on the information to be recorded. A hologram with interference fringes at the time of irradiation of the modulated object light is formed ,
The recording encryption information is a modulation pattern formed by imaging the biometric information by a predetermined encoding method,
The recording encryption information is obtained by dividing the original image displaying the biometric information into a plurality of pixel blocks including a plurality of pixels and detecting the number of ON pixels or OFF pixels in each pixel block. ,
Light that is a bitmap image formed by converting into a conversion pixel pattern set in advance for each number of ON pixels or OFF pixels according to the detected number for each pixel block Information recording medium. In claim 9 ,
An optical information recording medium, wherein the pixel block is composed of an even number of pixels of six or more, and the conversion pixel pattern is set so that the number of ON pixels and OFF pixels is the same. In claim 9 or 10 ,
2. The optical information recording medium according to claim 1, wherein the hologram is an interference fringe between an object beam and phase spatial light modulated reference beam.

Images