JP5087774B2 - Liquid crystal image display device and liquid crystal image display method - Google Patents

Description

  The present invention relates to a liquid crystal image display device and a liquid crystal image display method in which image data displayed on a liquid crystal display screen is encrypted, and in particular, to a liquid crystal image display device and a liquid crystal display device of a visual decryption type encryption using polarized light. The present invention relates to an image display method.

  In recent years, with the development of the mobile computing environment, usage forms for performing work using information terminals such as personal computers in public transportation such as trains and airplanes have become widespread. In such a situation, there is a growing concern that confidential information of companies and the like is leaked when information displayed on the screen is accidentally or intentionally viewed by an unspecified number of people not intended by the user.

  On the other hand, it is expected that the need for improving the same security will increase also in a terminal installed in a public place and connected to a display (for example, a terminal of a financial institution or a terminal installed in a public office).

  As described above, security technology for maintaining confidentiality of information and preventing leakage is important. In order to ensure security, various encryption technologies are being developed for communication, and personal authentication technologies are being developed for connection and access to information. On the other hand, some protection is also required for the image information that is finally displayed on the screen through these procedures, but no progress has been made in this field. For example, even if connection is established through communication encryption or personal authentication, there is a possibility of being seen from the surroundings when displayed on the screen. On the other hand, the leakage electromagnetic wave of the image signal transmitted from the computer or the like to the monitor may be intercepted, and the image information may be acquired and reproduced.

  For example, as a technique for preventing leakage of information included in image data displayed on a liquid crystal display such as a computer or a cellular phone, a filter sheet that restricts the viewing angle is attached to the surface of the liquid crystal display, thereby making visible space There are known methods for limiting. Also, directional image display, parallax barrier type, 3D-LCD (polarized glasses type or no glasses type) using patterned retardation film, integral type, super multi-view, volume display, holography application, etc. Has also been considered.

  Further, Patent Document 1 discloses a liquid crystal image display device capable of limiting the viewing angle. As shown in FIG. 1, in this liquid crystal image display device, a driving liquid crystal panel 1 is arranged on the observer side (upper side in the figure), and on the opposite side (lower side in the figure) of the driving liquid crystal panel 1 to the observer. The compensation liquid crystal panel 2 is laminated on the driving liquid crystal panel 1. One polarizing plate 3 and 4 is disposed on the viewer side and the counter-viewer side of these liquid crystal panels, respectively. A driving circuit 5 for applying a driving voltage is connected to the driving liquid crystal panel 1 via an electrode (not shown), and a viewing angle is changed to the compensation liquid crystal panel 2 via a transparent electrode (not shown). A compensation voltage application circuit 6 for applying a voltage for the purpose is connected. The driving liquid crystal panel 1 has a transmissive or transflective pixel structure and displays an image. The compensation liquid crystal panel 2 can apply a voltage independently of the driving liquid crystal panel 1. Further, by appropriately dividing the electrodes of the compensating liquid crystal panel 2, the viewing angle characteristics corresponding to the use environment and the contents to be displayed are selectively displayed in each part within the display surface of the same liquid crystal image display device. can do.

In these methods, by restricting the viewing angle, only the user himself / herself can normally browse from a specific position, and information displayed on the display screen cannot be viewed from other positions and angles. Peeping can be prevented.
JP 2005-265930 A JP 2001-274971 A JP 2005-517218 A Han-Yen Tu, Chau-Jern Cheng and Mao-Ling Chen; Optical image encryption based on polarization encoding by liquid crystal spatial light modulators; Journal of Optics A: Pure and Applied Optics; 2004; 6; pp.524-528. http://www.iop.org/EJ/abstract/1464-4258/6/6/005>

  However, since the liquid crystal image display device inherently includes image data, the above method cannot counter eavesdropping due to interception of leaked electromagnetic waves.

  On the other hand, a printed matter using visual decryption secret sharing is known (Patent Document 2). Image encryption using the visual decryption secret sharing method, image information is divided into multiple dot patterns that can only be seen as noise, printed on transparent films, and the images are restored by overlaying the transparent films. It is what is done. However, since this method uses a plurality of pixels to express one point, there is a problem that the resolution, brightness, and contrast are halved.

  Further, Non-Patent Document 1 discloses a proposal for encrypting a black-and-white binary image such as a character displayed on a liquid crystal display using the visual decryption secret sharing method. As shown in FIG. 2, this liquid crystal display includes two liquid crystal layers 7 and 8 for an input signal and a decryption key. Then, as shown in FIG. 3, with respect to the liquid crystal layer 7 for input signals and the liquid crystal layer 8 for decryption key, the alignment of the liquid crystal is divided into two directions, vertical and parallel, and these liquid crystal layers are superposed to form a phase of the liquid crystal layer. Decoding is performed by exclusive OR (XOR) using a delay. Thus, the image information itself can be encrypted by visual decryption encryption using polarized light, which is one of optical encryption techniques. For this reason, even if leaked electromagnetic waves are intercepted, the image data is encrypted, and therefore information cannot be reproduced unless there is decryption information. However, this method can be applied only to a black and white binary image, and there is a problem that a multi-tone image such as a gray scale or full color display cannot be decoded.

  On the other hand, Patent Document 3 discloses a liquid crystal display in which a liquid crystal layer of a liquid crystal display is divided into two, and encryption and decryption are performed by polarization rotation of a liquid crystal cell. Although this liquid crystal display can be encrypted in units of cells at the polarization rotation angle, it cannot limit the observation area, but cannot be effectively excluded from peeping from the back or side. It was.

  The present invention has been made in view of such problems. The main object of the present invention is to realize a liquid crystal image display device and a liquid crystal display device that simultaneously realize visual decryption of an encrypted image and restriction of a viewing angle, and have excellent contrast even when a high-resolution multi-value image is encrypted. It is to provide an image display method.

In order to achieve the above object, a first liquid crystal image display device according to the present invention is a liquid crystal image display device capable of displaying given image data in gradation, and the image data is converted into a visual decryption type encryption. An encryption unit that performs encryption based on the data, a decryption key generation unit that generates decryption key data for decrypting the encrypted data encrypted by the encryption unit, a pixel structure, and a polarization rotation element for each pixel An encryption liquid crystal panel for displaying the encrypted data generated by the encryption means, an encryption operating voltage application means for driving the polarization rotation element of the encryption liquid crystal panel, and a pixel structure, and the pixel pitch is The liquid crystal panel is smaller than the encryption liquid crystal panel, has a polarization rotation element for each pixel, and displays the decryption key liquid crystal panel for displaying the decryption key data generated by the decryption key generation means, and the polarization of the decryption key liquid crystal panel A decryption key operating voltage applying means for driving the rolling element, the encryption liquid crystal panel and the decryption key liquid crystal panel are arranged to be spaced apart from each other at a predetermined distance and correspond to each pixel, and the encryption means The encrypted data obtained by encrypting the image data based on the visual decryption type encryption is generated by changing the polarization rotation angle of the polarization rotation element for each pixel, and the decryption key generating means Generates decryption key data in which the polarization rotation angle for decrypting the image data according to the rotation angle is generated, displays the encrypted data by driving the encryption liquid crystal panel with the encryption operating voltage applying means, and decrypting the encrypted data Appropriate polarization rotation corresponding to the image data by displaying the decryption key data by driving the decryption key liquid crystal panel with the key operating voltage application means and superimposing the encryption data and the decryption key data for each pixel A degree is given for each pixel, and on the viewing surface side, the light that has passed through the corresponding pixels of the encryption liquid crystal panel and the decryption key liquid crystal panel can be reconstructed only in the observation area The reconstructed image is reproduced in the observation area, and a dummy image can be displayed in the area outside the observation area . As a result, multi-gradation display image data such as color and gray scale can be encrypted and displayed for each pixel, so that information leakage can be effectively prevented. In particular, since the restored image data itself is not directly displayed on the liquid crystal panel, information cannot be obtained even if the display data itself is intercepted. For example, even if image restoration is attempted by intercepting leaked electromagnetic waves, it is encrypted. Since only the data can be displayed and the contents cannot be confirmed, it is possible to secure effective security against such eavesdropping. In addition, by limiting the viewing angle, it is possible to limit the viewing range and the observation area, and it is possible to effectively prevent peeping from the side and the back.

  In the second liquid crystal image display device, the cryptographic liquid crystal panel has a first cryptographic liquid crystal layer having a predetermined pixel pitch and an aperture ratio, and a pixel pitch and an aperture ratio substantially equal to the first cryptographic liquid crystal layer. A second encryption liquid crystal layer spaced apart from the first encryption liquid crystal layer by a certain distance and arranged so as to overlap; the encryption means sends the encryption data to the first encryption liquid crystal layer; Dividing the data into second encrypted data for the second liquid crystal, giving the first encrypted data to the first encrypted liquid crystal layer and the second encrypted data to the second encrypted liquid crystal layer, The encrypted data can be encrypted via the second encryption liquid crystal layer. Thereby, by setting the installation interval, the pixel pitch, and the aperture ratio of the first encryption liquid crystal layer and the second encryption liquid crystal layer, the observation area where the decoded image can be observed can be three-dimensionally limited. It is possible to effectively deal with sneaking from the side or from behind.

  Further, in the third liquid crystal image display device, the decryption key liquid crystal panel includes a first decryption key liquid crystal layer having a predetermined pixel pitch and an aperture ratio, and a pixel pitch and aperture substantially equal to the first decryption key liquid crystal layer. And a second decryption key liquid crystal layer that is spaced apart from the first decryption key liquid crystal layer by a certain distance, and is disposed so as to overlap, and the decryption key generating means receives the decryption key data. , The first decryption key data for the first decryption key liquid crystal layer and the second decryption key data for the second decryption key liquid crystal are divided into the first decryption key liquid crystal layer and the first decryption key liquid crystal layer. By providing the two decryption key data to the second decryption key liquid crystal layer, the encrypted data can be decrypted via the first decryption key liquid crystal layer and the second decryption key liquid crystal layer. Thus, by setting the installation interval, the pixel pitch, and the aperture ratio of the first decryption key liquid crystal layer and the second decryption key liquid crystal layer, an observation region in which the decrypted image can be observed is three-dimensionally displayed. It can be limited and can effectively cope with snooping from the side or snooping from behind.

Furthermore, the fourth liquid crystal image display device is a liquid crystal image display device capable of displaying gradation of given image data, and encryption means for encrypting the image data based on visual decryption encryption, A decryption key generating means for generating decryption key data for decrypting the encrypted data encrypted by the encryption means; a backlight light source disposed on the opposite side of the observation surface; and a first light source disposed on the observation surface side. One polarizing plate, a second polarizing plate disposed apart from the first polarizing plate and having a polarization direction orthogonal or parallel to the first polarizing plate, and disposed between the first polarizing plate and the second polarizing plate, A liquid crystal panel having a rotation element, which has a pixel structure, has a polarization rotation element for each pixel, is arranged so as to overlap the first polarizing plate, and displays encrypted data generated by the encryption means LCD panel for encryption and pixel structure The pixel pitch is smaller than that of the encryption liquid crystal panel, each pixel has a polarization rotation element, and is arranged to match the encryption liquid crystal panel for each pixel, and is generated by the decryption key generation means Decryption key liquid crystal panel for displaying key data, encryption operating voltage applying means for driving the polarization rotation element of the encryption liquid crystal panel, and decryption for driving the polarization rotation element of the decryption key liquid crystal panel And a key operating voltage applying means, and the encryption liquid crystal panel and the decryption key liquid crystal panel are arranged so as to be spaced apart from each other by a certain distance and correspond to each pixel, and the encryption means has a polarization rotation element for each pixel. The encrypted data obtained by encrypting the image data based on the visual decryption type encryption is generated by changing the polarization rotation angle, and the decryption key generation means responds to the polarization rotation angle of the encrypted data for each pixel. Generating decryption key data in which the polarization rotation angle for decrypting the image data is set, driving the encryption liquid crystal panel by the encryption operation voltage application means to display the encryption data, and applying the decryption key operation voltage By displaying the decryption key data by driving the decryption key liquid crystal panel by means, and overlapping the encrypted data and the decryption key data for each pixel, an appropriate polarization rotation angle corresponding to the image data is given to each pixel. The light passing through the corresponding pixels of the encryption liquid crystal panel and the decryption key liquid crystal panel through the first and second polarizing plates was given to the observation surface side through the backlight light source only in the observation region. An image can be reconstructed, and the reconstructed image can be reproduced in the observation region, while a dummy image can be displayed in a region outside the observation region . In addition, by limiting the viewing angle, it is possible to limit the viewing range and the observation area, and it is possible to effectively prevent peeping from the side and the back.

  Furthermore, the fifth liquid crystal image display device can be configured such that there are three or more encryption liquid crystal panels and decryption key liquid crystal panels. As a result, it is possible to further enhance the security by adding encryption.

  Furthermore, the sixth liquid crystal image display device can be configured such that the encrypted data generated by the encryption means changes with time. This makes it more difficult to decrypt encrypted data that changes over time.

  Furthermore, the seventh liquid crystal image display device can change the encryption pattern for each frame constituting the moving image in displaying the moving image. As a result, it is possible to further enhance the security by adding encryption.

Furthermore, the eighth liquid crystal image display device is a liquid crystal image display device capable of displaying given image data in gradation, and an encryption means for encrypting the image data based on visual decryption encryption, The backlight light source disposed on the side opposite to the observation surface side, the first polarizing plate disposed on the observation surface side, and the first polarizing plate are spaced apart from each other and are orthogonal or parallel to the first polarizing plate. A second polarizing plate having a polarization direction, disposed between the first polarizing plate and the second polarizing plate, having a pixel structure, having a polarization rotation element for each pixel, and disposed so as to overlap the first polarizing plate, The liquid crystal panel for encryption for displaying the encrypted data generated by the encryption means, the encryption operation voltage application means for driving the polarization rotation element of the encryption liquid crystal panel, and the polarization rotation angle for each pixel are different. And a retardation plate arranged in The encoding means generates encrypted data obtained by encrypting the image data for each pixel based on the visual decryption type encryption according to the polarization rotation angle for each pixel of the phase difference plate, and encrypts it with the encryption operation voltage applying means. The liquid crystal panel is driven to display the encrypted data, and the encrypted data is overlapped on each pixel to obtain a polarization rotation angle corresponding to the image data for each pixel. Light that has passed through corresponding pixels of the encryption liquid crystal panel and the decryption key liquid crystal panel through the first and second polarizing plates to the observation surface side through the light source can be reconstructed only in the observation area. The reconstructed image is reproduced in the observation area, and a dummy image can be displayed in the area outside the observation area . As a result, multi-gradation display image data such as color and gray scale can be encrypted and displayed for each pixel, so that information leakage can be effectively prevented. In particular, since the restored image data itself is not directly displayed on the liquid crystal panel, information cannot be obtained even if the display data itself is intercepted. For example, even if image restoration is attempted by intercepting leaked electromagnetic waves, it is encrypted. Since only the data can be displayed and the contents cannot be confirmed, it is possible to secure effective security against such eavesdropping.

  Furthermore, the ninth liquid crystal image display device can include a plurality of retardation plates. The polarization rotation element by the retardation plate can be freely attached and detached, and the number of layers can be changed according to the situation.

  Furthermore, in the tenth liquid crystal image display device, the retardation plate can be configured to be detachable. As a result, security can be further enhanced by replacing the phase difference plate with a pattern having a different polarization rotation angle or changing the number of phase difference plates.

Furthermore, the eleventh liquid crystal image display device is a liquid crystal image display device capable of displaying given image data in gradation, and encryption means for encrypting the image data based on visual decryption encryption, Decryption key generation means for generating decryption key data for decrypting the encrypted data encrypted by the encryption means, and a pixel structure, a polarization rotation element for each pixel, and encrypted data generated by the encryption means A liquid crystal panel for encryption, an encryption operating voltage applying means for driving a polarization rotation element of the encryption liquid crystal panel, and a pixel structure, each pixel having a polarization rotation element and generating a decryption key A decryption key liquid crystal panel for displaying the decryption key data generated by the means, and a decryption key operating voltage application means for driving the polarization rotation element of the decryption key liquid crystal panel, The key-key liquid crystal panel is arranged at a fixed distance and corresponding to each pixel, and the pixel pitch of each corresponding pixel of the decryption key liquid-crystal panel is relatively reduced as compared with the encryption liquid-crystal panel. In this way, the displayed decryption key data pattern is reduced, or the encrypted data pattern is enlarged, and the encryption means changes the polarization rotation angle of the polarization rotation element for each pixel to visually decode the image data. In addition to generating encrypted data encrypted based on the encryption, the decryption key generating means generates decryption key data in which a polarization rotation angle for decrypting image data is set for each pixel according to the polarization rotation angle of the encrypted data. The encrypted liquid crystal panel is driven by the encryption operating voltage applying means to display the encrypted data, and the decryption key liquid crystal panel is driven by the decryption key operating voltage applying means to generate the decryption key data. By displaying the data and superimposing the encrypted data and the decryption key data for each pixel, an appropriate polarization rotation angle corresponding to the image data is given to each pixel, and the encryption liquid crystal panel and the decryption are provided on the observation surface side. The light that has passed through the corresponding pixel with the key liquid crystal panel is configured so as to be able to reconstruct the image given only within the observation area, while reproducing the reconstructed image within the observation area, while observing In an area outside the area, a dummy image can be displayed . As a result, multi-gradation display image data such as color and gray scale can be encrypted and displayed for each pixel, so that information leakage can be effectively prevented. In particular, since the restored image data itself is not directly displayed on the liquid crystal panel, information cannot be obtained even if the display data itself is intercepted. For example, even if image restoration is attempted by intercepting leaked electromagnetic waves, it is encrypted. Since only the data can be displayed and the contents cannot be confirmed, it is possible to secure effective security against such eavesdropping. In addition, by limiting the viewing angle, it is possible to limit the viewing range and the observation area, and it is possible to effectively prevent peeping from the side and the back. In particular, the pixel pitch of the decryption key liquid crystal panel and the encryption liquid crystal panel is not changed by hardware, and the pattern of the decryption key data and the pattern of the encryption data are reduced / enlarged, so that the relative pitch of the pixels can be reduced. The change can be executed in software, and the spatial observation area can be limited at a lower cost.

Furthermore, a twelfth liquid crystal image display method includes an encryption unit that encrypts image data based on visual decryption encryption, a backlight light source disposed on the opposite side of the observation surface, and an observation surface side. Between the first polarizing plate and the second polarizing plate, the first polarizing plate disposed, the second polarizing plate disposed apart from the first polarizing plate and having a polarization direction orthogonal or parallel to the first polarizing plate. A liquid crystal panel arranged and having a polarization rotation element, having a pixel structure, having a polarization rotation element for each pixel, and being arranged so as to overlap the first polarizing plate, the encrypted data generated by the encryption means And a first encryption liquid crystal layer having a predetermined pixel pitch and an aperture ratio, and a first encryption liquid crystal panel having a pixel pitch and an aperture ratio substantially equal to the first encryption liquid crystal layer. When separated by a certain distance from the layer And an encryption liquid crystal panel having a second encryption liquid crystal layer arranged so as to overlap with each other, and a pixel structure, the pixel pitch is smaller than that of the encryption liquid crystal panel, and each pixel has a polarization rotation element. The liquid crystal panel for encryption is arranged for each pixel, and the liquid crystal panel for decryption key for displaying the decryption key data generated by the decryption key generation means and the polarization rotation element of the liquid crystal panel for encryption are driven. A liquid crystal type image display device capable of gradation display of given image data, and an encryption operation voltage application means of the above and a decryption key operation voltage application means for driving the polarization rotation element of the liquid crystal panel for decryption key A liquid crystal image display method for displaying image data, wherein the encryption means encrypts the image data based on the visual decryption encryption by changing the polarization rotation angle of the polarization rotation element for each pixel. In addition to generating encrypted data, the roughly encrypted data is divided into first encrypted data for the first encrypted liquid crystal layer and second encrypted data for the second liquid crystal, and the decryption key generating means encrypts each pixel. A step of generating decryption key data in which a polarization rotation angle for decrypting image data is set in accordance with the polarization rotation angle of the data; and an encryption liquid crystal panel is driven by an encryption operation voltage applying means to generate the encrypted data. In order to display, the first encryption data is supplied to the first encryption liquid crystal layer and the second encryption data is supplied to the second encryption liquid crystal layer, and the decryption key operating voltage applying means drives the decryption key liquid crystal panel to perform the decryption. An appropriate polarization rotation angle corresponding to the image data is provided for each pixel, and observation is performed through the backlight light source. On the face side The light that has passed through the corresponding pixels of the encryption liquid crystal panel and the decryption key liquid crystal panel through the first and second polarizing plates can reconstruct an image provided only in the observation area. While the reconstructed image is reproduced, a dummy image can be displayed in an area outside the observation area . As a result, multi-gradation display image data such as color and gray scale can be encrypted and displayed for each pixel, so that information leakage can be effectively prevented. In particular, since the restored image data itself is not directly displayed on the liquid crystal panel, information cannot be obtained even if the display data itself is intercepted. For example, even if image restoration is attempted by intercepting leaked electromagnetic waves, it is encrypted. Since only the data can be displayed and the contents cannot be confirmed, it is possible to secure effective security against such eavesdropping. In addition, by limiting the viewing angle, it is possible to limit the viewing range and the observation area, and it is possible to effectively prevent peeping from the side and the back.

Further, the thirteenth polarization operation type image display device is a polarization operation type image display device capable of displaying gradation of given image data, and encrypting means for encrypting the image data based on visual decryption encryption. And a decryption key generation means for generating decryption key data for decrypting the encrypted data encrypted by the encryption means, a pixel structure, a polarization rotation element for each pixel, and an encryption generated by the encryption means And a decryption key data having a pixel structure, a pixel pitch smaller than that of the encryption panel, a polarization rotation element for each pixel, and generated by a decryption key generation means Is provided so that the encryption panel and the decryption key panel are spaced apart from each other by a certain distance and correspond to each pixel, and the encryption means is provided for each pixel. The encrypted data obtained by encrypting the image data based on the visual decryption type encryption is generated by changing the polarization rotation angle of the light rotation element, and the decryption key generation unit responds to the polarization rotation angle of the encrypted data for each pixel. Generating decryption key data with a polarization rotation angle for decrypting the image data, displaying the encrypted data on the encryption panel, displaying the decryption key data on the decryption key panel, and By overlapping the encrypted data and the decryption key data, an appropriate polarization rotation angle corresponding to the image data is given for each pixel, and the observation panel side passes through the corresponding pixels of the encryption panel and the decryption key panel. light, are reconstructed configured to be able to image provided only in the observation area, while reproducing an image in which the reconstructed in the observation area, in the off-observation region area, dummy Image can be capable of displaying. With the above configuration, the video signal can be encrypted so as to be expressed by adding the polarization rotation angle based on the visual decryption secret sharing method, and the security against leakage and interception of image data can be improved. In addition, the observation area can be limited by the correspondence of the pixel position of the encrypted data, and it can be set so that the image data can be viewed only at the observation position limited to a specific distance, improving security against peeping from the side or behind Can do. Further, by using polarized light, multi-gradation expression is possible, and high-definition display with increased expressive power compared to the conventional encrypted image display device can be realized.

  Furthermore, the fourteenth polarization operation type image display apparatus can use liquid crystal as a polarization rotation element. Thus, encryption can be easily performed for each pixel.

  Furthermore, the fifteenth polarization operation type image display device is a retardation plate in which a polarization rotation element is patterned. As a result, it is possible to realize field-of-view restriction and encryption at low cost.

  Furthermore, in the sixteenth polarization operation type image display device, the total number of encryption liquid crystal panels and decryption key liquid crystal panels can be three or more. As a result, it is possible to further enhance the security by adding encryption.

Furthermore, the seventeenth polarization calculation type image display method is a polarization calculation type image display method for displaying image data on a polarization calculation type image display device capable of gradation display of given image data, and visually displaying the image data. Based on the decryption-type encryption, encrypted data that is encrypted so as to change the polarization rotation angle of the polarization rotation element for each pixel is generated, and the approximate encryption data is converted into the first encryption data for the first encryption layer, the second encryption data, and the second encryption data. A step of generating decryption key data in which the polarization rotation angle for decrypting the image data is set for each pixel according to the polarization rotation angle of the encrypted data, and divided into second encryption data for the encryption layer, and encryption In order to display the encrypted data on the encryption panel for displaying data, the first encrypted data is given to the first cryptographic layer and the second encrypted data is given to the second cryptographic layer, while the decryption key data is given. table Displaying the decryption key data on the decryption key panel for performing the above process, and by overlapping the encrypted data and the decryption key data for each pixel, an appropriate polarization rotation angle corresponding to the image data is obtained for each pixel. Given light passing through the corresponding pixels of the encryption panel and the decryption key panel through the first polarizing plate arranged on the observation surface side and the second polarizing plate arranged on the opposite surface side is observed. An image provided only within the region can be reconstructed, and the reconstructed image can be reproduced within the observation region, while a dummy image can be displayed in a region outside the observation region . As a result, multi-gradation display image data such as color and gray scale can be encrypted and displayed for each pixel, so that information leakage can be effectively prevented. In particular, since the restored image data itself is not directly displayed on the liquid crystal panel, information cannot be obtained even if the display data itself is intercepted. For example, even if image restoration is attempted by intercepting leaked electromagnetic waves, it is encrypted. Since only the data can be displayed and the contents cannot be confirmed, it is possible to secure effective security against such eavesdropping. Furthermore, by setting the installation interval of the first encryption liquid crystal layer and the second encryption liquid crystal layer, the pixel pitch, and the aperture ratio, the observation area where the decoded image can be observed can be limited three-dimensionally. It is possible to effectively cope with the snooping from the rear or the snooping from the rear.

  According to the liquid crystal image display device and the liquid crystal image display method of the present invention, visual decryption of an encrypted image and restriction of a viewing angle can be realized at the same time, and deterioration of resolution and luminance can be reduced. Compared with conventional privacy protection filters that are attached to liquid crystal displays such as personal computers and mobile phones, in particular, the use of an algorithm that realizes visual decryption encryption using polarized light not only limits the viewing angle, but also images. Even if leaked electromagnetic waves are intercepted by signal encryption, image data cannot be constructed, and security can be further strengthened. Furthermore, the observation position can be three-dimensionally limited by the left and right and depth, and peeping from the rear as well as from the side can be prevented, and not only data leakage in the middle but also information leakage at the final output stage can be dealt with.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below exemplify a liquid crystal image display device and a liquid crystal image display method for embodying the technical idea of the present invention, and the present invention is a liquid crystal image display device and a liquid crystal. The formula image display method is not specified as follows. Further, the present specification by no means specifies the members shown in the claims to the members of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the embodiments are not intended to limit the scope of the present invention unless otherwise specified, and are merely explanations. It is just an example. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same name and symbol indicate the same or the same members, and detailed description thereof will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing.

  The present inventors applied a visual decoding type secret sharing method to a display as a countermeasure against peeping of a liquid crystal display device such as a liquid crystal display, and based on a screen display with a white and black dot pattern and a transmission and shading pattern. Research on an apparatus for restoring an image by superimposing a decoding mask was repeated (see FIGS. 11 and 12). With this technology, the image itself displayed on the screen is encrypted, so even if a leaked electromagnetic wave is intercepted, it can be seen as simple noise and information can be concealed. Furthermore, the observation area where the image is restored can be limited by adjusting the size of the mask and the installation distance with respect to the screen. However, this method has a problem that the resolution, brightness, and contrast are reduced because a plurality of pixels are used to display one light spot. In order to solve this problem, the present inventors have conducted intensive research on the visual decoding secret sharing method using polarized light and have come up with the present invention.

  The liquid crystal image display device has a configuration in which a polarization rotation element, that is, a liquid crystal layer is sandwiched between two polarizing plates. The polarization rotation element is divided into a plurality of layers, and the plurality of layers are overlapped for each pixel to restore image data. The liquid crystal layer divided into a plurality of layers functions as a set of an encryption liquid crystal panel and a decryption key liquid crystal panel, and image data cannot be reproduced by themselves, but image data can be reproduced by combining them. As a result, the target image is recognized by the user's eyes, but the image signal itself displayed on the liquid crystal layer remains encrypted and is not decrypted as data. Even if intercepted by some means, image data cannot be constructed. Thereby, electronic wiretapping using the leaked electromagnetic wave can be effectively eliminated.

In addition, a configuration in which image data is reproduced by combining a plurality of layers can be realized by a combination of a liquid crystal layer and a retardation plate in addition to a liquid crystal layer. In other words, if the liquid crystal layer is used, an arbitrary polarization rotation angle can be set. On the other hand, if all the data of each layer is intercepted, there is a possibility that the data will be decrypted. Such a configuration using a hardware decryption panel increases security because it cannot be decrypted only with electronic information. Moreover, since it is only necessary to add a physical phase difference plate, the hardware configuration can be simplified and an inexpensive encryption can be realized. As described above, by using a part of the polarization rotator as a retardation plate pattern, it is possible to further reduce the possibility that an image signal to the polarization rotator is intercepted and restored. If a plurality of retardation plates are used, restoration can be made more difficult. For example, when a plurality of people have a phase difference plate, the decoded data can be visually recognized and information access can be physically restricted only while each person is bringing the phase difference plate. Furthermore, the image display device can be configured with only a retardation plate.
(Viewing angle control)

  Furthermore, the peeping from the side can be prevented by intentionally narrowing the viewing angle and limiting the observation area. The observation area is three-dimensionally determined by the installation interval of the polarization rotation elements of each layer, the pixel pitch, and the aperture ratio. When viewed from within the observation region, the target image is recognized, but when viewed from outside the observation region, the pixels of the polarization rotation elements of each layer are displaced, and thus a normal image is not recognized. As a result, it is possible to prevent sneaking from seeing in an oblique direction from the surroundings.

  Furthermore, not only the viewing angle is limited, but also the distance from the liquid crystal image display device can be limited. This also prevents the act of magnifying from a distance. In this way, secret sharing by using a plurality of key images for decryption keys can be used to enhance the secret.

  In this specification, for convenience, they are called encryption / decryption keys. However, since they are actually secret sharing, both are equivalent, and the encryption and decryption keys can be interchanged. Displaying the decryption key data on the decryption key liquid crystal panel may be display data generated based on the decryption key data (for example, an inverted pattern of the decryption key data) in addition to displaying the decryption key data itself. In image encryption by secret sharing, information is dispersed into a plurality of images, and each image is called a “share image”. In this specification, at least one of the shared images is “encryption” and at least one is “decryption key”. Particularly when moving images are targeted, the “encryption” can be changed for each screen or one frame. The “decryption key” can use a single pattern or a plurality of patterns. Of course, it goes without saying that the decryption key may be changed for each screen. In particular, when encrypting a video, if the random number sequence that is the key for generating the encryption is fixed, that is, if the pattern of the encryption data that is the key is fixed, by storing the encrypted data sent from the information sender, There is a possibility that encryption data as a key is estimated. Therefore, when displaying a moving image, security can be improved by encrypting based on a random number sequence unique to each frame. In this case, it is preferable to use a liquid crystal as a polarization rotation element rather than a retardation plate.

Hereinafter, a liquid crystal image display device according to an embodiment of the present invention will be described with reference to FIG. The liquid crystal image display device 100 shown in FIG. 4 includes a backlight light source 10, a first polarizing plate 20, an encryption liquid crystal panel 30, a decryption key liquid crystal panel 40, and a second polarizing plate 50. The liquid crystal image display device 100 is of a transmissive type in which the backlight emitted from the backlight light source 10 is controlled to pass / non-pass through the polarizing plates 20 and 50 and the liquid crystal panels 30 and 40. The liquid crystal image display device 100 employs an active matrix system, and can display gradation of image data such as full color and gray scale. However, it is also possible to adopt a reflective type that does not use a backlight, or a transflective type that uses a backlight and reflected light in combination.
(Light source 10 for backlight)

As the backlight light source 10, a CCFL (Cold-Cathode Fluorescent Lamp) or an LED (Light-Emitting Diode) that is generally used as a liquid crystal backlight can be suitably used.
(First polarizing plate 20, second polarizing plate 50)

  The polarizing plate has a bias in the vibration direction of light, and is a filter that extracts light oscillating in a certain direction from natural light oscillating in all directions. The polarization of light includes linearly polarized light and circular / elliptical polarized light depending on its direction, and an element that changes to linearly polarized light is particularly called a polarizer. Linearly polarized light is often converted into circular or elliptically polarized light by a retardation plate or the like, and these are called a circularly polarized plate and an elliptically polarizing plate.

The 1st polarizing plate 20 and the 2nd polarizing plate 50 are polarizing filters which make a direction orthogonal to each other a polarization direction, as shown in FIG. As shown in FIG. 5, in the liquid crystal image display device, the first and second polarizing plates 20 and 50 are arranged orthogonally, and the light passing through the polarizing plate on one side changes the polarizer on the opposite side according to the alignment state of the liquid crystal. The display is controlled by changing the alignment state of the liquid crystal according to the voltage. That is, in a state where no operating voltage is applied to the liquid crystal, the liquid crystal is twisted so that it is aligned with the polarization direction of the polarizing plates arranged orthogonally, and the light incident from one polarizing plate is twisted by the liquid crystal, and the other polarization Can pass through the board. That is, it can be turned on. On the other hand, when the liquid crystal is aligned by applying the operating voltage to the liquid crystal by the operating voltage applying means, the light is not twisted, and the light incident from one polarizing plate cannot be transmitted through the other polarizing plate and is turned off. The OFF state represents black without light emission. In this way, the liquid crystal functions as a shutter to control ON / OFF of light emission. Furthermore, colorization and multi-valued imaging can be realized by using a color filter. In this example, 256 gradation display is possible.
(Encryption liquid crystal panel 30 and decryption key liquid crystal panel 40)

  The liquid crystal panel includes an encryption liquid crystal panel 30 for displaying encrypted data and a decryption key liquid crystal panel 40 for displaying decryption key data. Each liquid crystal panel has a polarization rotation element for each pixel. Each liquid crystal panel is installed so that the corresponding positions of the pixels provided in the polarization rotation elements of the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40 coincide with each other.

  As the liquid crystal panel, twisted nematic liquid crystal, super twisted nematic liquid crystal, parallel-arranged nematic liquid crystal, or the like can be used as appropriate. The liquid crystal alignment in the liquid crystal panel can change the polarization state and optical rotation direction of incident light such as vertical alignment, parallel alignment (uniaxial alignment), antiparallel alignment, twist alignment, and hybrid alignment, and to the panel. All the liquid crystal display modes that can change the degree of change of the polarization state and the optical rotation direction of incident light by applying the voltage can be used.

  In particular, in the case of hybrid alignment, since there is no threshold characteristic, the liquid crystal alignment changes gradually with voltage application, birefringence adjustment is easy, and viewing angle control can be performed accurately. It is. Further, in the case of the twisted orientation, display can be performed by changing the optical rotation, so that a display with a high contrast ratio can be obtained and display quality can be improved. Further, in the case of parallel alignment (uniaxial alignment) and vertical alignment, it is easy to analyze the alignment state, and it is easy to optimize the optical characteristic design and the applied voltage of the decryption key liquid crystal panel 40 and the encryption liquid crystal panel 30. And viewing angle control can be easily performed.

  As the liquid crystal material in the encryption liquid crystal panel 30, any liquid crystal material can be used as long as it has birefringence and the alignment direction can be changed by an electric field. In addition, regarding the polarizing plate described above, when the vibration plane of polarized light rotates 90 ° when no voltage is applied to the liquid crystal layer, the transmission direction of the polarizing plate is orthogonal and transmits light (normally white), Any of the types in which the transmission direction of the polarizing plate is parallel and does not transmit light (normally black) can be used.

  As the liquid crystal material in the decryption key liquid crystal panel 40, any liquid crystal material can be used as long as it has birefringence and the orientation direction can be changed by an electric field. The liquid crystal alignment in the decryption key liquid crystal panel 40 can change the polarization state and optical rotation direction of incident light such as vertical alignment, parallel alignment (uniaxial alignment), antiparallel alignment, twist alignment, and hybrid alignment. In addition, all liquid crystal display modes that can change the degree of change in the polarization state and optical rotation direction of incident light by applying a voltage to the panel can be used.

In particular, when the decryption key liquid crystal panel 40 is in a hybrid orientation, it does not have a threshold characteristic in its voltage dependence, so that it undergoes a gradual change in liquid crystal orientation with respect to voltage application, and birefringence can be easily adjusted. The viewing angle control can be performed with high accuracy. Furthermore, the hybrid alignment is particularly suitable in that it compensates for the influence of liquid crystal molecules that do not respond to voltage application existing near the transparent electrode interface of the encryption liquid crystal panel 30 and widens the viewing angle.
(Encryption operation voltage application means 60, decryption key operation voltage application means 70)

The encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40 are connected to the encryption operation voltage application means 60 and the decryption key operation voltage application means 70, respectively, and an operation voltage for driving a polarization rotation element included in the liquid crystal panel. Is applied to drive. This operating voltage application means constitutes a liquid crystal drive driver that is driven by controlling ON / OFF and gradation independently for each pixel. Further, the encryption operation voltage application means 60 and the decryption key operation voltage application means 70 are connected to the encryption means 80 and the decryption key generation means 90 that control the respective operations.
(Encryption means 80)

  The encryption unit 80 generates encrypted data based on image data input from the outside. Based on the generated image data, the encryption operation voltage applying means 60 is controlled, and the liquid crystal of the encryption liquid crystal panel 30 is driven to perform ON / OFF control.

In order to display desired image data on the liquid crystal image display device, the polarization rotation angle is given to the polarization rotation elements of the corresponding pixels of the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40. The polarization rotation angle is given at a random ratio for each pixel. Thus, the image data can be reproduced by combining the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40. On the other hand, since only the data before decoding remains in each liquid crystal panel, even if these data are acquired by leaked electromagnetic waves or the like, the image data is not reproduced.
(Decryption key generation means 90)

  The decryption key generation unit 90 generates decryption key data corresponding to the encrypted data. By superimposing the encrypted data and the decryption key data, a correct rotation angle of the polarization plane for expressing the original image data can be obtained.

In the above example, the decryption is difficult by using an encryption pattern in which the polarization rotation angle is changed for each pixel. Further, the encryption pattern is not constant, and can be changed with time, for example. For example, when a moving image is displayed on a liquid crystal image display device, the decryption can be made more difficult by changing the encryption pattern for each frame.
(Visual decryption encryption)

  In the present embodiment, a visual decryption secret sharing method (visual decryption encryption) is adopted as an encryption technique. Secret sharing is a secret management method in which secret information is distributed over multiple keys, and access to the secret information is permitted only after a certain number of keys are available. There is an effect to reduce. Visual decryption cryptography is a new type of secret sharing, and is a cryptographic method proposed by Naor and Shamir in 1994 to distribute secret information into a plurality of encrypted images. In the conventional visual decryption type encryption, since one pixel is composed of a plurality of pixels (for example, 4 pixels), there is a problem that the resolution, brightness, and contrast are inferior and the image quality is lowered. On the other hand, in the present embodiment, a polarization-type visual decryption type encryption using rotation of the polarization plane is constructed, and the image data desired to be kept secret is distributed to the encrypted data and the decryption key data. Well, the reduction of contrast is prevented.

  This state will be described with reference to FIG. FIG. 6 shows (a) a backlight, (b) a first polarizing plate 20, (c) an encryption liquid crystal panel 30, (d) a decryption key liquid crystal panel 40, (e) a second polarizing plate 50, and (f). The output light pattern is shown. Among these, (b) the first polarizing plate 20 and (e) the second polarizing plate 50 indicate the transmission direction of polarized light, (c) the encryption liquid crystal panel 30 and (d) the decryption key liquid crystal panel 40 are polarized. The rotation of the surface is shown. Here, for the sake of explanation, it is assumed that a binary image is displayed in a block pattern of 4 pixels, and image data to be displayed in the pattern shown in (f) is input. (B) The 1st polarizing plate 20 and the (e) 2nd polarizing plate 50 are being fixed to the polarization direction which mutually orthogonally crosses. (C) The encryption liquid crystal panel 30 and the (d) decryption key liquid crystal panel 40 each have a polarization rotation angle pattern of 0 and 90 ° as shown in FIG. When passing through these two liquid crystal panels, the left half of the four pixels is 90 °, and the right half is zero. As a result, in the left half, (e) the light incident on the polarizing plate from the backlight (b) passes through (c) the encryption liquid crystal panel 30 and (d) the decryption key liquid crystal panel 40. Passing through the plate 50, (f) the left half of the output light pattern is “bright”. On the other hand, in the right half, light is not transmitted and becomes “dark”. In this way, by controlling the polarization rotation angle of the liquid crystal panel, encryption is performed for each pixel to ensure the security of information display.

  In the above example, the polarization rotation angle of the pixel is set to either 0 or 90 ° for simplification, but it goes without saying that intermediate values such as ± 45 ° and 30 ° can also be taken. In particular, as shown in FIG. 4, the use of an arbitrary polarization rotation angle can further increase the accuracy of encryption.

  Next, based on FIG. 4, a state in which optical computation is performed with the polarization visual decryption type encryption will be described. In this liquid crystal image display device 100, it is assumed that the polarization rotation element is a super twisted nematic liquid crystal, and the polarization rotation angle of each liquid crystal panel can be controlled from 0 to 180 ° and 256 gradations. In addition, the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40 are arranged in three dimensions in a one-dimensional direction so that the pixels overlap each other. The polarization rotation angles of the encryption liquid crystal panel 30 are 60 °, 10 °, and 45 ° from the left, while the polarization rotation angles of the decryption key liquid crystal panel 40 are 30 °, 80 °, and 45 ° from the left. As a result, the polarization obtained by transmitting through the second polarizing plate 50 is 90 ° in all three pixels, so that the light is transmitted and becomes 1, that is, “bright” or ON. The same effect can be obtained by setting the angle to 270 ° in addition to the total angle of 90 ° by optical calculation.

  On the other hand, in both of the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40, the obtained data is not the image data itself, but the encrypted data and the decryption key data. The data cannot be restored. Accordingly, since complete image data does not exist even inside the liquid crystal image display device, even if this data is intercepted, information is not leaked, and security can be improved.

  In the example of FIG. 4, the decryption key liquid crystal panel 40 is disposed below the encryption liquid crystal panel 30. However, the present invention is not limited to this configuration, and the decryption key liquid crystal panel may be disposed on the encryption liquid crystal panel. A similar effect can be obtained.

  In addition to the encryption liquid crystal panel and the decryption key liquid crystal panel being constituted by a single sheet, these can be constituted by a plurality of liquid crystal panels. For example, as in the modification shown in FIG. 7, the encryption liquid crystal panel 30 includes a first encryption liquid crystal layer 31 and a second encryption liquid crystal layer 32, and the polarization rotation element of the first encryption liquid crystal layer 31 and the second encryption liquid crystal layer 31. The encrypted data is constructed by overlapping the polarization rotation element of the encryption liquid crystal layer 32. The encryption unit 80 distributes the encrypted data to the first encryption liquid crystal layer and the second encryption liquid crystal layer. Thereby, it becomes more difficult to perform decryption with the data of each liquid crystal layer, and security can be improved.

  Similarly, the decryption key liquid crystal panel can be formed of a plurality of layers. FIG. 8 shows an example in which the decryption key liquid crystal panel 40 includes a first decryption key liquid crystal layer 41 and a second decryption key liquid crystal layer 42. In this case, the decryption key generation means 90 distributes the decryption key data to the first decryption key liquid crystal layer and the second decryption key liquid crystal layer, and constructs the decryption key data by superimposing them. Even in this configuration, it is possible to improve the security by making it difficult to decode only the data of each liquid crystal layer.

Thus, by configuring the liquid crystal panel with a plurality of liquid crystal layers, the accuracy of encryption is increased, and decryption is more difficult and security can be improved. However, if a large number of liquid crystal layers are provided, the amount of light is reduced. Therefore, the number of liquid crystal layers and the like are appropriately determined according to the luminance required for the liquid crystal used.
(Polarization rotation angle)

  Next, the total number of combination patterns for encryption is calculated from the possible values of the polarization rotation angle. In the liquid crystal image display device according to FIG. 8, when the polarization rotation element is a super twisted nematic liquid crystal, it is assumed that each layer can control a polarization rotation angle of 0 to 180 ° and 256 gradations. When the polarization rotation angle in a certain pixel when displaying using a general liquid crystal display is θs, the polarization rotation angle when the liquid crystal image display device according to FIG. 8 is used can be expressed as follows.

In the above equation (1), the combination of (Φm1 + Φm2 + Φd) has a free value for Φm1 and Φm2, and there are two Φd satisfying the above equation between 180 ° and 256 × 256 × 2 = 131072. .
(When θs = 30 °, (Φm1 + Φm2 + Φd) has six possible values of 30 °, 150 °, 210 °, 330 °, 390 °, and 510 °.)

By using polarization visual decryption encryption in this way, one pixel of the secret image can be expressed by one pixel of the liquid crystal panel for encryption and the liquid crystal panel for decryption key, so there is no degradation in resolution and the image after decryption The effect of improving the contrast is obtained.
(Viewing angle control)

  In the above example, the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40 are arranged so that the corresponding pixels coincide with each other. A wide viewing angle can be secured by arranging the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40 close to each other. On the other hand, it is desired to intentionally narrow the viewing angle in order to prevent peeping from the surroundings. As a method for limiting the viewing angle, the pitch of the liquid crystal layer is changed between the encryption liquid crystal layer and the decryption key liquid crystal layer, and the distance between the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40 is constant. By limiting the viewing angle by separating the distance, the viewing range can be limited.

This example will be described with reference to FIG. In this example, by separating the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40, the rotation angle of the polarization plane can be correctly obtained in the front area. On the other hand, in the right region, as a result of the pixels being visually recognized as being shifted by the spacing between the liquid crystal panels, the encryption liquid crystal panel 30 and the decryption key liquid crystal panel 40 do not have the correct pixel combination, and the polarization plane is rotated. As a result of adding different angles, it cannot be visually recognized as normal image data. Similarly, even in the left region, as a result of being viewed with the pixels shifted, it cannot be viewed as correct image data. As a result, it can be visually recognized as correct image data only at the front position, and as a result, the viewing angle is limited, and it cannot be correctly viewed from the top, bottom, left and right, and peeping from nearby positions can be prevented.
(Dummy image display)

  In the above example, the image data is designed to be reproduced only in front of the liquid crystal image display device, so that a normal image cannot be displayed in a region outside the visual field range (left and right regions in FIG. 9). It is composed. Here, as a modified example, it is possible to display intentionally different images in the left and right regions while displaying a normal image at the front position. For example, in a liquid crystal display that displays a personal identification number, a dummy number that is not a personal identification number is intentionally displayed in the right region or the left region, so that a person who has seen a sneak can be disturbed. In addition, a dummy number is set as a special notification number, and when this number is entered, an alarm is issued that there is a possibility that there is a person who has seen it, or a process such as notifying the appropriate department is performed. Such a person may be detected.

Furthermore, in addition to the configuration for reproducing the image data in the front, as another modification, the image data can be intentionally reproduced at any of the upper, lower, left, and right positions. For example, correct image data can be displayed only in the right region in FIG. 9, and dummy image data can be displayed in the front and left regions. As a result, it is possible to believe that the image seen from the front is correct data, and to disturb the snooping action.
(Phase difference plate 45)

  In the above example, both the encrypted data and the decryption key data are set using a liquid crystal panel capable of controlling the polarization rotation angle. In this configuration, there is an advantage that the encryption pattern can be changed for each pixel and for each time. On the other hand, by using two liquid crystal panels, two liquid crystal drive drivers are required. One liquid crystal panel can be used together for compensation, etc., and the hardware burden can be reduced. However, since a plurality of liquid crystals and their driving circuits are required, the circuit becomes complicated and the cost is reduced. Become high.

  On the other hand, by providing a retardation pattern corresponding to the decryption key data on a phase difference plate with a fixed polarization rotation angle, visual decryption encryption can be realized without increasing the number of liquid crystal panels. This example will be described with reference to FIG. 10 showing a liquid crystal image display device according to Embodiment 2 of the present invention. A liquid crystal image display device 200 shown in FIG. 10 includes a backlight light source 10, a first polarizing plate 20, a cryptographic liquid crystal panel 30, a retardation plate 45, and a second polarizing plate 50. The same members as those in FIG. 4 and the like are denoted by the same reference numerals, and detailed description thereof is omitted. The liquid crystal image display device 200 shown in this figure includes a phase difference plate 45 in place of the decryption key liquid crystal panel 40. The phase difference plate 45 is a phase difference film that compensates for the phase difference generated by the liquid crystal (for example, prevention of coloring). Some retardation films have an optical compensation function for widening the viewing angle. In the present embodiment, the viewing angle can be determined according to the purpose of use, and a retardation film can be used for the adjustment.

  Since the phase difference plate 45 is used as a decryption key panel, a polarization rotation angle is provided for each pixel. The polarization rotation angle is not uniform, and it is difficult to perform decryption by disposing differently for each pixel. On the other hand, according to the polarization rotation angle pattern for each pixel provided on the decryption key panel, the encryption unit 80 generates an encryption pattern in which the polarization rotation angle is adjusted for each pixel of the image data. As a result, the encrypted data generated according to the encryption pattern is displayed on the encryption liquid crystal panel 30, and the phase difference plate 45 is superimposed on the encryption liquid crystal panel 30 and observed from the observation surface side. The light that has passed through the corresponding pixels with the plate 45 reconstructs the image given only within the observation area, that is, the decoded image data can be visually recognized.

  The polarization rotation angle of the phase difference plate 45 cannot be physically changed and is fixed. However, by making the retardation plate 45 detachable from the liquid crystal image display device, the encryption pattern can be physically changed by preparing and replacing the retardation plate 45 with different polarization rotation angles. .

Furthermore, if a plurality of retardation plates 45 can be attached, the number of layers of the retardation plate 45, that is, the decryption panel can be changed, and not only the encryption pattern but also the encryption accuracy can be changed according to the intended use and purpose. You can also. As described above, a display capable of reproducing intermediate colors that are not binary images by the XOR operation and limiting the observation area is realized.
(Visual decryption encryption)

Hereinafter, the principle of achieving both encryption of the display image and restriction of the observation area by visual decryption encryption will be described. FIG. 11 is an explanatory diagram showing how a monochrome image is encrypted. Here, each of the black pixels and white pixels constituting the secret image to be encrypted is represented by a combination of pixels composed of 2 × 2 auxiliary pixels. Since the pixel value is determined by the combination of the display image and the decryption key data, only the display image or the decryption key data does not leak any secret image information. An example in which an encryption pattern is configured by this method is shown in FIG. The decrypted image is obtained by copying the decryption key data pattern onto a transparent sheet such as an OHP sheet and overlaying it on the display image. Decryption does not require any computation. By reducing the size of the decryption key panel and placing it at a certain distance from the image display surface as shown in FIG. 13, the viewpoint position at which the display pixels and the decryption key panel pixels can be viewed in one-to-one correspondence is limited. Therefore, the viewing area of the display can be limited simultaneously with the encryption of the display image. The example of FIG. 13 shows an example in which image information is distributed and encrypted in two images. One of the two images is a decryption mask and the other is a display image, and is observed according to the pitch of the decryption mask and the installation distance. The position can be limited. This configuration has an effect of limiting the viewing distance as well as simply limiting the viewing angle.
(Restriction of observation area)

The encrypted image is decrypted by observing the auxiliary pixel of the decryption key panel and the auxiliary pixel of the display image from a viewpoint position corresponding to one to one. As shown in FIG. 14, the pitch of the decryption key panel is reduced compared to the pixel pitch of the display image, and the decryption key panel is installed at a certain distance from the image display surface. The pitch of the auxiliary pixel on the decryption key panel is P _M , the pitch of the auxiliary pixel on the display screen is P _D , the distance from the display screen to the observation position is Z _E , and the distance from the display screen to the decryption key panel is Z _M In this case, it is necessary to install a decryption key panel at a position where the following relationship of Equation 2 is established.

The configuration of FIG. 14 can deal with multi-tone images and color images. However, in the state of FIG. 14, there is only one observable position depending on the pitch and the arrangement interval. That is, the observation area is too limited, and there is only one position where the secret image can be observed without missing pixels and without crosstalk, and cannot be observed simultaneously with both eyes. Therefore, since it is necessary to enlarge the observation area, a black area is introduced around the light emitting portion of the display image. Here, FIGS. 15 and 16 show a configuration in which an aperture ratio is introduced in order to obtain an observation region. In these drawings, FIG. 15 shows a region without a chip and FIG. 16 shows a region without a crosstalk. Here, when the opening width is W and the pitch is P, the opening ratio a can be obtained by a = W / P. 15 and 16, the opening width of the auxiliary pixel of the display image is W _D , the opening ratio is a _D , the opening width of the auxiliary pixel of the decryption key panel is W _M , the opening ratio is a _M, and the width of the observation region Ask for. As shown in FIG. 15, the width V _dx of the region in which the entire pixel can be seen is determined from the light beam connecting the encryption panel and the opening of the auxiliary pixel of the display image, and the following formula 3 is established.

Also, as shown in FIG. 16, the width V _cx of the region where no crosstalk occurs is as follows.

Given in. Since the width of the observation region is limited by two types of conditions, crosstalk and pixel defect, in order to maximize the width of the observation region, the right sides of Equation 3 and Equation 4 must be equal. As a result, a _M = 1 is obtained, and it is understood that the optimum condition is that the aperture ratio of the auxiliary pixel of the decryption key panel is 1. The depth of the observation area is limited as shown in Equation 5 below.

From the 1 / (N-1) linear approximation, the condition that the right sides of Equation 5 and Equation 6 are equal is a _M = 1. When the aperture ratio of the auxiliary pixel is set to 1, the right side of Equations 3 and 4 is 0, but the observation area shown in Equations 3 and 4 can be obtained by reducing the aperture ratio of the auxiliary pixel of the display image. Both have the effect of expanding. Alternatively, the observation area is enlarged by bringing P _M closer to P _D. From Equation 2, this means that the decryption key panel is brought closer to the image display surface, which coincides with the fact that the observation area is not limited by the close contact. Even if the aperture ratio of the display image is limited by the specifications of the realized hardware, the observation area can be adjusted by the pitch of the decryption key panel and the installation distance. As described above, it is possible to obtain a design guideline for geometrically deriving the observation area and realizing an observation area of a desired size.

  Even if the pattern of the decryption key panel is fixed, different images can be displayed by setting the polarization rotation angle (x, y) according to the pixel value of the secret image. However, from the viewpoint of security, there is an increased risk that a key pattern is estimated by accumulating a large number of display images and analyzing the appearance frequency. In the case of displaying a moving image, it is desirable that the key pattern changes from frame to frame in the implementation shown in FIG.

  As described above, the liquid crystal image display device can realize the limitation of the viewing angle and the decryption of the encrypted image data at the same time by using the rotation of the polarization plane by the liquid crystal. Even security can be increased. Further, there is an advantage that the observation area can be restricted simultaneously with the encryption of the display image.

Note that it is possible to set the mode in which the image data is displayed as it is after decryption, or the viewing angle is adjusted as necessary. That is, by configuring the viewing angle control and / or encryption ON / OFF so as to be switchable, it is possible to selectively use according to the purpose of use and application.
(Prototype liquid crystal image display device)

  Next, a liquid crystal image display device was created, and an observation image in the observation region was observed, thereby demonstrating a polarization operation by stacking liquid crystal panels. Here, a liquid crystal panel having a structure in which a liquid crystal panel from which an output-side polarizing film is removed and a liquid crystal panel from which an incident-side polarizing film is removed is laminated, that is, a polarizing film-liquid crystal panel-liquid crystal panel-polarizing film structure. Was made. The manufactured laminated liquid crystal panel is shown in FIG. 18, as a screen display example, a color sample display example on a black background is shown in FIG. 19, and a color sample display example on a white background is shown in FIG. Here, the interval between the two liquid crystal panels is 1 cm. In the screen display example, as shown in FIGS. 19 and 20, when the polarization rotation angle in the background liquid crystal panel is 0 ° (black if the liquid crystal panel is single), each pixel displayed in the foreground is a pixel. The light intensity increases monotonously with the value. On the other hand, when the polarization rotation angle in the background liquid crystal panel is 90 ° (white if the liquid crystal panel is single), the light intensity monotonously decreases with respect to the pixel value of each pixel displayed on the foreground liquid crystal panel. . Table 1 shows the relationship between these colors, that is, the relationship between the background or foreground color displayed on the laminated liquid crystal panel and the observed color. From Table 1, when the polarization rotation angle in the background liquid crystal panel is 0 °, the color displayed in the foreground is observed as it is, and when the polarization rotation angle in the background liquid crystal panel is 90 °, the color displayed in the foreground As a result, the color change due to the rotation of the polarized light and the multi-gradation display principle were confirmed.

  FIG. 21 shows an example of an encrypted image subjected to encryption that enables decryption based on polarization as image data to be displayed on the liquid crystal display. Each pixel is expressed in white and black. For comparison, FIG. 22 also shows the result of decoding this image based on the conventional intensity calculation (white: transmission, black: shielding). Further, FIG. 23 shows the result displayed on the laminated liquid crystal panel in which the polarization rotation angle is added (white: polarization rotation angle 90 °, black: polarization rotation angle 0 °).

  From these figures, in the liquid crystal image display device, when comparing the image in the observation area, that is, the decoded image visually recognized in the front and the image visually recognized outside the observation area, the encryption / decryption key is polarized. Since it was used, it was confirmed that white was displayed brightly in the observation area. In particular, in the conventional method shown in FIG. 22, the white portion of the “TU” character, which is the decoding result, is expressed in black and white random dots (grain pattern), whereas the decoding according to this embodiment shown in FIG. As a result, it was confirmed that white / black was determined for each pixel, and the contrast between the white portion and the black portion was improved. Further, FIG. 24 shows a state in which this liquid crystal display is observed from outside the observation region. In FIG. 24, (a) shows a state seen from above, (b) shows a state seen from below, (c) shows a state seen from the right, and (d) shows a state seen from the left. . As shown in these figures, the “TU” character that is the decoding result is not visible outside the observation region. From these results, it was confirmed that the effectiveness of decryption by adding the rotation angle of the polarization plane and the limitation of the observation area can be realized.

  In this way, by using the secret sharing method, the secret data is distributed into n pieces (n is 2 or more) of encrypted data, and k pieces (k is 2 or more and n or less) of them are overlapped to form the secret data. It is possible to encrypt so as to be decrypted. Decryption can be made more difficult by distributing the encrypted data to a plurality of sheets. Note that there is no distinction in terms of operation function among a plurality of pieces of encrypted data in which secret data is distributed. That is, the encryption layer for displaying the encrypted data and the decryption key layer for displaying the decryption key data can be arbitrarily set. For example, a polarization rotation element that displays encrypted data transmitted from an information sender is used as an encryption layer, and a polarization rotation element that displays encryption data held by a user is used as a decryption key layer. The transmission data side can be a decryption key layer.

  In the secret sharing method, secret data is distributed to a plurality of pieces of encrypted data based on a random number sequence unique to each user. At this time, a part of the plurality of sheets can be used as decryption data serving as a decryption key. For example, when the secret data is distributed to two pieces of encrypted data, the user owns one piece of encrypted data, and the information sender owns the other piece. For arbitrary secret data, the information sender can configure encrypted data to be communicated so that it can be decrypted by the encrypted data held by the user. When the secret data is distributed to three or more pieces of encrypted data, a combination of one piece of encrypted data to be communicated with two pieces of decryption data, or a combination of two pieces of encrypted data to be communicated with one piece of decryption data. Is possible. When there are two or more pieces of decryption data, a plurality of keys can be used so that decryption is performed only when a plurality of users bring the decryption data. On the other hand, when there are multiple pieces of encrypted data to be communicated, access to the encrypted data can be controlled by using a plurality of servers with different access authorities or by transmitting encrypted data through different communication paths. It can be strictly limited as compared with the case of using data. If this is used, it can be suitably applied to applications that require the approval of a plurality of supervisors for information access.

  In addition, although the example applied to the liquid crystal type image display apparatus was demonstrated in the above example, polarization calculation type image display apparatuses other than a liquid crystal can also be used. For example, a phase difference plate, a magneto-optic spatial light modulator, an electro-optic spatial light modulator, or the like can be used.

It is sectional drawing which shows the structure of the conventional liquid crystal display device. It is sectional drawing which shows the structure of the other conventional liquid crystal display device. It is a schematic diagram explaining a mode that the encryption using a polarization is implement | achieved by exclusive OR of a two-dimensional plane. It is sectional drawing which shows the liquid crystal type image display apparatus which concerns on embodiment of this invention. It is a perspective view which shows the state which the orientation direction of a 1st polarizing plate and a 2nd polarizing plate and the light permeate | transmit. It is a schematic diagram explaining a mode that it encrypts with the pattern of a polarization rotation angle. It is sectional drawing which shows the liquid crystal type image display apparatus which concerns on the modification of this invention. It is sectional drawing which shows the liquid crystal type image display apparatus which concerns on the other modification of this invention. It is sectional drawing which shows the liquid crystal type image display apparatus which concerns on the further another modification of this invention. It is sectional drawing which shows the liquid crystal type image display apparatus concerning Embodiment 2 of this invention. It is explanatory drawing which shows a mode that a binary image is encrypted. It is explanatory drawing which shows a mode that an observation area | region is limited. It is explanatory drawing explaining visual decoding type | mold encryption. It is explanatory drawing which shows the relationship between the pitch of a panel for decoding keys, and installation distance. It is explanatory drawing which shows the area | region where a secret image is decoded and observed without the lack of a pixel. It is explanatory drawing which shows the area | region where a secret image is decoded and observed without crosstalk. It is explanatory drawing which shows the mode of the decoding of the polarization encryption by lamination | stacking of a liquid crystal panel. It is a perspective view which shows the laminated liquid crystal panel of the liquid crystal type image display apparatus which concerns on an Example. It is an image figure which shows the example of a display of the color sample in the black background displayed in FIG. It is an image figure which shows the example of a display of the color sample in the white background displayed in FIG. It is an image figure which shows the example of a visual decoding type | mold encryption. It is an image figure which shows the decoding result by the intensity | strength calculation which is the conventional visual decoding type | mold encryption. It is an image figure which visually recognizes the decoding result based on the Example of this invention from the inside of an observation area | region. It is an image figure which visually recognizes the decoding result based on the Example of this invention from the outside of an observation area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100, 200 ... Liquid crystal type image display apparatus 1 ... Drive liquid crystal panel 2 ... Compensation liquid crystal panel 3 ... Observer side polarizing plate 4 ... Anti-observer side polarizing plate 5 ... Drive circuit 6 ... Compensation voltage application circuit 7 ... Input signal liquid crystal layer 8 ... Decryption key liquid crystal layer 10 ... Backlight light source 20 ... First polarizing plate 30 ... Encryption liquid crystal panel 31 ... First encryption liquid crystal layer 32 ... Second encryption liquid crystal layer 40 ... Decryption key Liquid crystal panel 41... First decryption key liquid crystal layer 42. Second decryption key liquid crystal layer 45... Phase difference plate 50... Second polarizing plate 60 .. Encrypting operation voltage applying means 70. Encryption means 90 ... Decryption key generation means

Claims (17)

A liquid crystal image display device capable of gradation display of given image data,
Encryption means for encrypting image data based on visual decryption encryption;
Decryption key generation means for generating decryption key data for decrypting the encrypted data encrypted by the encryption means;
A liquid crystal panel for encryption having a pixel structure, having a polarization rotation element for each pixel, and displaying encrypted data generated by the encryption means;
An encryption operation voltage applying means for driving the polarization rotation element of the encryption liquid crystal panel;
Decryption key liquid crystal having a pixel structure, having a pixel pitch smaller than that of the encryption liquid crystal panel, having a polarization rotation element for each pixel, and displaying the decryption key data generated by the decryption key generation means A panel,
A decryption key operating voltage applying means for driving the polarization rotation element of the decryption key liquid crystal panel;
With
The encryption liquid crystal panel and the decryption key liquid crystal panel are spaced apart from each other by a predetermined distance and arranged to correspond to each pixel,
The encryption means generates encrypted data obtained by encrypting image data based on visual decryption encryption by changing the polarization rotation angle of the polarization rotation element for each pixel,
The decryption key generating means generates decryption key data in which a polarization rotation angle for decoding image data is set for each pixel according to the polarization rotation angle of the encrypted data;
The encryption operation voltage applying means drives the encryption liquid crystal panel to display the encrypted data, and the decryption key operation voltage application means drives the decryption key liquid crystal panel to display the decryption key data. Then, by overlapping the encrypted data and the decryption key data for each pixel, an appropriate polarization rotation angle corresponding to the image data is given to each pixel, and the encryption liquid crystal panel and the decryption key liquid crystal are provided on the observation surface side. The light that has passed through the corresponding pixels with the panel is configured to reconstruct an image given only within the observation area ,
A liquid crystal image display device configured to reproduce a reconstructed image in an observation area while displaying a dummy image in an area outside the observation area . The liquid crystal image display device according to claim 1,
The encryption liquid crystal panel is
A first encryption liquid crystal layer having a predetermined pixel pitch and an aperture ratio;
A second cryptographic liquid crystal layer having a pixel pitch and an aperture ratio substantially equal to the first cryptographic liquid crystal layer, spaced apart from the first cryptographic liquid crystal layer by a certain distance, and disposed so as to overlap;
Have
The encryption means divides encrypted data into first encrypted data for the first encrypted liquid crystal layer and second encrypted data for the second liquid crystal;
By providing the first encrypted data to the first encrypted liquid crystal layer and the second encrypted data to the second encrypted liquid crystal layer, the encrypted data is transmitted via the first encrypted liquid crystal layer and the second encrypted liquid crystal layer. A liquid crystal image display device configured to be encrypted. The liquid crystal image display device according to claim 1 or 2,
The decryption key liquid crystal panel comprises:
A first decryption key liquid crystal layer having a predetermined pixel pitch and aperture ratio;
A second decryption key liquid crystal having a pixel pitch and an aperture ratio substantially equal to those of the first decryption key liquid crystal layer, spaced apart from the first decryption key liquid crystal layer by a certain distance, and arranged so as to overlap. Layers,
Have
The decryption key generating means divides the decryption key data into first decryption key data for the first decryption key liquid crystal layer and second decryption key data for the second decryption key liquid crystal,
By providing the first decryption key data to the first decryption key liquid crystal layer and the second decryption key data to the second decryption key liquid crystal layer, the first decryption key liquid crystal layer and the second decryption key use A liquid crystal image display device configured to decrypt encrypted data through a liquid crystal layer. A liquid crystal image display device capable of gradation display of given image data,
Encryption means for encrypting image data based on visual decryption encryption;
Decryption key generation means for generating decryption key data for decrypting the encrypted data encrypted by the encryption means;
A backlight light source disposed on the opposite side of the observation surface;
A first polarizing plate disposed on the observation surface side;
A second polarizing plate disposed apart from the first polarizing plate and having a polarization direction orthogonal or parallel to the first polarizing plate;
A liquid crystal panel disposed between the first polarizing plate and the second polarizing plate and having a polarization rotation element;
A liquid crystal panel for encryption having a pixel structure, having a polarization rotation element for each pixel, arranged to overlap the first polarizing plate, and displaying encrypted data generated by the encryption means;
The decryption key generation has a pixel structure, the pixel pitch is smaller than that of the encryption liquid crystal panel, a polarization rotation element is provided for each pixel, and the pixel is aligned with the encryption liquid crystal panel for each pixel. A decryption key liquid crystal panel for displaying the decryption key data generated by the means;
An encryption operation voltage applying means for driving the polarization rotation element of the encryption liquid crystal panel;
A decryption key operating voltage applying means for driving the polarization rotation element of the decryption key liquid crystal panel;
With
The encryption liquid crystal panel and the decryption key liquid crystal panel are spaced apart from each other by a predetermined distance and arranged to correspond to each pixel,
The encryption means generates encrypted data obtained by encrypting image data based on visual decryption encryption by changing the polarization rotation angle of the polarization rotation element for each pixel,
The decryption key generating means generates decryption key data in which a polarization rotation angle for decoding image data is set for each pixel according to the polarization rotation angle of the encrypted data;
The encryption operation voltage applying means drives the encryption liquid crystal panel to display the encrypted data, and the decryption key operation voltage application means drives the decryption key liquid crystal panel to display the decryption key data. Then, by superimposing the encrypted data and the decryption key data for each pixel, an appropriate polarization rotation angle corresponding to the image data is given to each pixel, and the first light is transmitted to the observation surface side through the backlight light source. And the light that has passed through the corresponding pixels of the encryption liquid crystal panel and the decryption key liquid crystal panel through the second polarizing plate is configured to be able to reconstruct an image given only within the observation region ,
A liquid crystal image display device configured to reproduce a reconstructed image in an observation area while displaying a dummy image in an area outside the observation area . A liquid crystal image display device according to any one of claims 1 to 4,
3. A liquid crystal image display device, comprising a total of three or more encryption liquid crystal panels and decryption key liquid crystal panels. A liquid crystal image display device according to any one of claims 1 to 5,
The liquid crystal image display device characterized in that the encrypted data generated by the encryption means changes over time. A liquid crystal image display device according to any one of claims 1 to 6,
A liquid crystal image display device, wherein a moving image is displayed by changing an encryption pattern for each frame constituting the moving image. A liquid crystal image display device capable of gradation display of given image data,
Encryption means for encrypting image data based on visual decryption encryption;
A backlight light source disposed on the opposite side of the observation surface;
A first polarizing plate disposed on the observation surface side;
A second polarizing plate disposed apart from the first polarizing plate and having a polarization direction orthogonal or parallel to the first polarizing plate;
A cipher disposed between the first polarizing plate and the second polarizing plate, having a pixel structure, having a polarization rotation element for each pixel, and disposed so as to overlap the first polarizing plate, and generated by the encryption unit An encryption LCD panel for displaying digitized data;
An encryption operation voltage applying means for driving the polarization rotation element of the encryption liquid crystal panel;
A retardation plate arranged so that the polarization rotation angle is different for each pixel,
The encryption means generates encrypted data obtained by encrypting image data on a pixel-by-pixel basis based on visual decryption encryption according to the polarization rotation angle for each pixel of the retardation plate, and the encryption operation voltage applying means The encryption liquid crystal panel is driven to display the encrypted data, and the phase difference plate is superimposed on the encrypted data for each pixel to obtain a polarization rotation angle corresponding to the image data for each pixel. The light passing through the corresponding pixels of the encryption liquid crystal panel and the decryption key liquid crystal panel through the first and second polarizing plates is given to the observation surface side through the backlight light source only in the observation region. It is configured to allow image reconstruction ,
A liquid crystal image display device configured to reproduce a reconstructed image in an observation area while displaying a dummy image in an area outside the observation area . The liquid crystal image display device according to claim 8,
A liquid crystal image display device comprising a plurality of the retardation plates. The liquid crystal image display device according to claim 8 or 9, wherein
A liquid crystal image display device, wherein the retardation plate is configured to be detachable. A liquid crystal image display device capable of gradation display of given image data,
Encryption means for encrypting image data based on visual decryption encryption;
Decryption key generation means for generating decryption key data for decrypting the encrypted data encrypted by the encryption means;
A liquid crystal panel for encryption having a pixel structure, having a polarization rotation element for each pixel, and displaying encrypted data generated by the encryption means;
An encryption operation voltage applying means for driving the polarization rotation element of the encryption liquid crystal panel;
A decryption key liquid crystal panel having a pixel structure, having a polarization rotation element for each pixel, and displaying the decryption key data generated by the decryption key generation unit;
A decryption key operating voltage applying means for driving the polarization rotation element of the decryption key liquid crystal panel;
With
The encryption liquid crystal panel and the decryption key liquid crystal panel are spaced apart from each other by a predetermined distance and arranged to correspond to each pixel,
The displayed decryption key data pattern is reduced or the encrypted data pattern is enlarged so that the pixel pitch for each corresponding pixel of the decryption key liquid crystal panel is relatively smaller than that of the encryption liquid crystal panel. And
The encryption means generates encrypted data obtained by encrypting image data based on visual decryption encryption by changing the polarization rotation angle of the polarization rotation element for each pixel,
The decryption key generating means generates decryption key data in which a polarization rotation angle for decoding image data is set for each pixel according to the polarization rotation angle of the encrypted data;
The encryption operation voltage applying means drives the encryption liquid crystal panel to display the encrypted data, and the decryption key operation voltage application means drives the decryption key liquid crystal panel to display the decryption key data. Then, by overlapping the encrypted data and the decryption key data for each pixel, an appropriate polarization rotation angle corresponding to the image data is given to each pixel, and the encryption liquid crystal panel and the decryption key liquid crystal are provided on the observation surface side. The light that has passed through the corresponding pixels with the panel is configured to reconstruct an image given only within the observation area ,
A liquid crystal image display device configured to reproduce a reconstructed image in an observation area while displaying a dummy image in an area outside the observation area . Encryption means for encrypting image data based on visual decryption encryption;
A backlight light source disposed on the opposite side of the observation surface;
A first polarizing plate disposed on the observation surface side;
A second polarizing plate disposed apart from the first polarizing plate and having a polarization direction orthogonal or parallel to the first polarizing plate;
A liquid crystal panel disposed between the first polarizing plate and the second polarizing plate and having a polarization rotation element;
An encryption liquid crystal panel having a pixel structure, having a polarization rotation element for each pixel, arranged to overlap the first polarizing plate, and displaying encrypted data generated by the encryption means. ,
A first encryption liquid crystal layer having a predetermined pixel pitch and an aperture ratio;
A second cryptographic liquid crystal layer having a pixel pitch and an aperture ratio substantially equal to the first cryptographic liquid crystal layer, spaced apart from the first cryptographic liquid crystal layer by a certain distance, and disposed so as to overlap;
An encryption liquid crystal panel having
The decryption key generation has a pixel structure, the pixel pitch is smaller than that of the encryption liquid crystal panel, a polarization rotation element is provided for each pixel, and the pixel is aligned with the encryption liquid crystal panel for each pixel. A decryption key liquid crystal panel for displaying the decryption key data generated by the means;
An encryption operation voltage applying means for driving the polarization rotation element of the encryption liquid crystal panel;
A decryption key operating voltage applying means for driving the polarization rotation element of the decryption key liquid crystal panel;
A liquid crystal image display method for displaying image data on a liquid crystal image display device capable of gradation display of given image data,
The encryption means generates encrypted data obtained by encrypting image data based on visual decryption encryption by changing the polarization rotation angle of the polarization rotation element for each pixel, and also generates almost encrypted data as the first encryption data. Dividing the first encrypted data for the liquid crystal layer and the second encrypted data for the second liquid crystal;
The decryption key generating means generating decryption key data in which a polarization rotation angle for decoding image data is set for each pixel according to the polarization rotation angle of the encrypted data; and
In order to display the encrypted data by driving the encryption liquid crystal panel by the encryption operation voltage applying means, the first encryption data is displayed on the first encryption liquid crystal layer, and the second encryption data is displayed on the second encryption liquid crystal. Providing each of the layers, and driving the decryption key liquid crystal panel with the decryption key operating voltage applying means to display the decryption key data;
By overlapping the encrypted data and the decryption key data for each pixel, an appropriate polarization rotation angle corresponding to the image data is given to each pixel, and the first light source is supplied to the observation surface side through the backlight light source. The light that has passed through the corresponding pixels of the encryption liquid crystal panel and the decryption key liquid crystal panel through the first and second polarizing plates can reconstruct an image given only within the observation region ,
A liquid crystal image display method characterized in that a dummy image can be displayed in an area outside the observation area while reproducing the reconstructed image in the observation area . A polarization operation type image display device capable of gradation display of given image data,
Encryption means for encrypting image data based on visual decryption encryption;
Decryption key generation means for generating decryption key data for decrypting the encrypted data encrypted by the encryption means;
An encryption panel having a pixel structure, having a polarization rotation element for each pixel, and displaying encrypted data generated by the encryption means;
A decryption key panel having a pixel structure, having a pixel pitch smaller than that of the encryption panel, having a polarization rotation element for each pixel, and displaying the decryption key data generated by the decryption key generation means; ,
With
The encryption panel and the decryption key panel are spaced apart from each other by a certain distance, and arranged to correspond to each pixel,
The encryption means generates encrypted data obtained by encrypting image data based on visual decryption encryption by changing the polarization rotation angle of the polarization rotation element for each pixel,
The decryption key generating means generates decryption key data in which a polarization rotation angle for decoding image data is set for each pixel according to the polarization rotation angle of the encrypted data;
The encrypted data is displayed on the encryption panel, the decryption key data is displayed on the decryption key panel, and the encrypted data and the decryption key data are overlapped for each pixel so that the appropriate polarization corresponding to the image data is displayed. A rotation angle is given for each pixel, and on the observation surface side, the light that has passed through the corresponding pixels of the encryption panel and the decryption key panel can be reconstructed only in the observation area. Has been
A polarization operation type image display device configured to reproduce a reconstructed image in an observation area while displaying a dummy image in an area outside the observation area . The polarization calculation type image display device according to claim 13,
A polarization operation type image display apparatus, wherein the polarization rotation element is a liquid crystal. The polarization calculation type image display device according to claim 13,
A polarization calculation type image display apparatus, wherein the polarization rotation element is a patterned retardation plate. The polarization operation type image display device according to any one of claims 13 to 15,
3. A polarization operation type image display apparatus, wherein there are three or more encryption panels and decryption key panels in total. A polarization calculation type image display method for displaying image data on a polarization calculation type image display device capable of displaying gradation of given image data,
Encrypted image data is generated on the basis of visual decryption encryption so that the polarization rotation angle of the polarization rotation element is changed for each pixel, and the almost encrypted data is used as the first encrypted data for the first encryption layer. And divided into second cipher data for the second cipher layer,
A step of generating decryption key data in which a polarization rotation angle for decrypting image data is set for each pixel according to the polarization rotation angle of the encrypted data;
In order to display the encrypted data on the encryption panel for displaying the encrypted data, the first encrypted data is given to the first encrypted layer and the second encrypted data is given to the second encrypted layer, Displaying the decryption key data on a decryption key panel for displaying the decryption key data;
Including
By superimposing the encrypted data and the decryption key data for each pixel, an appropriate polarization rotation angle corresponding to the image data is given to each pixel, and the first polarizing plate disposed on the observation surface side and the opposite surface The light that has passed through the corresponding pixels of the encryption panel and the decryption key panel through the second polarizing plate arranged on the side can reconstruct the image given only in the observation region ,
A polarization calculation type image display method characterized in that a dummy image can be displayed in a region outside the observation region while the reconstructed image is reproduced in the observation region .