Patent Description:
According to the existing hologram techniques, a light source having a coherence length such as a laser is used to cause reference light and object light to interfere with each other, and a resultant interference fringe is recorded on a photoreactive polymer or the like, thereby recording optical phase information and intensity information of the object light. The object light can be reconstructed by emitting the reference light into the recorded photopolymer.

There are optical films and the like that are structurally controlled based on optical interference computed by a computer, which are called computer-generated holograms or the like. The object light can also be reconstructed by these computer-generated holograms.

Especially for computer-generated holograms, PTL <NUM> already discloses that the intensity of interference waves of reference light and object light is computed by a computer to produce an interference fringe.

There have also been disclosed a technique by which to produce actually such a hologram for use in a display (PTL <NUM>) and a technique by which to read reconstructed information from a hologram to perform authenticity verification (PTL <NUM>).

PTL <NUM> describes a laminar substrate which includes at least one area bearing a hologram. The substrate includes a carrier web and a hot-melt adhesive. An embossable coating is interposed between the carrier web and the hot-melt adhesive. The side of the coating adjacent to the hot-melt adhesive is embossed with a holographic microtexture in the areas. The hologram produces virtual images above and below the focal plane.

PTL <NUM> describes an hologram image sensor formed with a double gate type mold thin-film transistor structure comprising a semiconductor layer, a insulating layer, a top gate insulation film, a top gate electrode, and a bottom gate electrode.

See also PTL <NUM>, <NUM>, <NUM> and <NUM>.

As described above, there are disclosed methods for performing authenticity verification by visual inspection of reconstructed information from a hologram or via a reading device or the like. However, in the case of performing authenticity verification on a hologram using a reading device, after the visual inspection, the reconstructed information in an authentic article can be imitated and read by the reading device. Thus, the authenticity verification become ambiguous according to this method.

Three-dimensional spatial information in the reconstructed information from a hologram can be visually checked. However, such three-dimensional spatial information in the reconstructed information is hard to collectively acquire by a reading device or the like which can acquire two-dimensional information.

The present invention has been devised in view of the foregoing circumstances. An object of the present invention is to provide a hologram that allows easy acquisition of three-dimensional spatial distribution information in reconstructed information, a detection device, and a method for verifying authenticity of a hologram.

Specifically, with the detection device of claim <NUM>, it possible to implement a small-sized detection set in which a reference light source, a sensor, and a hologram are coaxially arranged in this order and to further miniaturize the detection device and laminate image sensors as described later.

According to the aspects of the present invention described above, it is easy to acquire three-dimensional spatial distribution information in reconstructed information from a hologram.

Hereinafter, not claimed embodiments and embodiments according to the claimed invention will be described in detail with reference to the drawings. Components that exhibit identical or similar functions are denoted by the same reference signs throughout the drawings, and redundant description thereof is omitted. Features of the present disclosure can be combined to form configurations. Therefore, the features, configurations, aspects, and embodiments of the present disclosure can be combined with one another, and the combinations can perform synergistic functions and produce synergistic effects.

First, referring to <FIG>, basic configurations of detection sets according to embodiments of the claimed invention will be described. <FIG> are diagrams describing the basic configurations of the detection sets according to the embodiments of the claimed invention.

The detection set <NUM> shown in <FIG> includes a detection device <NUM> and a hologram <NUM>. The detection device <NUM> includes a point light source <NUM> and an image sensor <NUM>. The detection device <NUM> emits reference light <NUM> from the point light source <NUM> into the hologram <NUM>. The image sensor <NUM> receives light <NUM> of an image reconstructed by the hologram <NUM>, converts the received light into an electric signal, and outputs the electric signal. On the other hand, a detection set 1a shown in <FIG> includes a detection device 2a and the hologram <NUM>. The detection device 2a includes the point light source <NUM> and an image sensor 5a. The point light source <NUM> emits reference light <NUM> that passes through the image sensor 5a and enters the hologram <NUM>. Then, the image sensor 5a receives the light <NUM> of an image reconstructed by the hologram <NUM>, converts the received light into an electric signal, and outputs the electric signal. The detection set <NUM> or the detection set 1a are configured as described above. Hereinafter, the hologram <NUM>, the image sensor <NUM> or the image sensor 5a, and the detection device <NUM> or the detection device 2a will be described.

<FIG> are partial cross-sectional views of instances of cross-section structures of a hologram according to an aspect of the claimed invention. The hologram <NUM> shown in <FIG> corresponds to the hologram <NUM> shown in <FIG>. As shown in <FIG>, the hologram <NUM> includes a formation layer <NUM> and a reflection layer <NUM>. The reflection layer <NUM> covers the formation layer <NUM>. An optical phase modulation structure <NUM> is formed on an interface <NUM> between the formation layer <NUM> and the reflection layer <NUM>. The hologram <NUM> shown in <FIG> has the reflection layer <NUM> like the hologram <NUM> shown in <FIG> and further has an additive layer <NUM>. That is, the hologram <NUM> shown in <FIG> is a hologram that includes the formation layer <NUM> and the reflection layer <NUM> laminated on each other. The formation layer <NUM> has the optical phase modulation structure <NUM> on the interface <NUM> (first interface) in contact with the reflection layer <NUM>. The interface <NUM> is a boundary surface between the formation layer <NUM> and the reflection layer <NUM>. The formation layer <NUM> is a layer that forms the optical phase modulation structure <NUM>. The formation layer <NUM> is a structure formation layer.

The formation material for the formation layer <NUM> can be a light-permeable polymer. The light-permeable polymer can be a thermoplastic resin, a thermal cross-linking resin, an ultraviolet cross-linking resin, or a thermoplastic ultraviolet cross-linking resin. Types of the polymer include acrylic resins such as a urethane-modified acrylic resin and an epoxy-modified acrylic resin, and an epoxy resin. The formation material for the formation layer <NUM> may be an inorganic material that transmits light, such as quartz, titanium oxide, or magnesium fluoride.

When the formation material for the formation layer <NUM> is a polymer, the formation layer <NUM> can be formed by applying the formation material to a substrate. The formation material can be applied to the substrate by gravure coating, die coating, lip coating, spin coating, dip coating, or spray coating. Otherwise, the formation layer <NUM> may be formed by a printing technique such as gravure printing or screen printing. Further, if the formation material is an organic material formable by evaporation such as a parylene, the formation layer <NUM> may be formed by evaporation.

When the formation material for the formation layer <NUM> is an inorganic material, the substrate can be coated with the formation material by dry coating techniques such as vacuum evaporation, sputtering, and atomic layer deposition, or wet coating techniques such as a sol-gel process.

The optical phase modulation structure <NUM> formed on the interface <NUM> is a hologram. The hologram can be a relief hologram with a concave-convex structure on its surface. The optical phase modulation structure <NUM> may have a plurality of unit blocks arranged. The unit blocks each have a convex or concave cubic shape. Phases of light from reconstruction points are calculated in correspondence with the locations of unit blocks, and phase angles are calculated based on the phases and recorded on the corresponding unit blocks. The unit blocks can be arranged to have a length half or less the wavelength of light. The intervals between the unit blocks can be <NUM> or more to <NUM>. The length of one side of each unit block can be half or less the wavelength of the light. The length of one side of each unit block can be <NUM> or more to <NUM>. The height (depth) of each unit block can be about half the wavelength of the light in a medium when the optical phase modulation structure <NUM> is used for light reflection. The retardation of each unit block can be approximately equal to the wavelength of the light when the phase modulation structure <NUM> is used for light transmission. The height (depth) of each unit block can be <NUM> or more to <NUM> or less when the optical phase modulation structure <NUM> is used for light reflection, and can be <NUM> or more to <NUM> or less when the optical phase modulation structure <NUM> is used for light transmission. In either case, the height (depth) of each unit block can be <NUM> or more to <NUM> or less.

The hologram can be a Fourier transform hologram, a computer-generated hologram, or a kinoform. The optical phase modulation structure <NUM> can be the phase modulation structure described in <CIT>. Otherwise, the optical phase modulation structure <NUM> may be projections and recesses in the phase angle recording layer <NUM> described in <CIT>. The hologram can be a volume hologram in which the refractive index in the formation layer is modulated. The volume hologram can be a Lippmann hologram. The material for the volume hologram can be a photopolymer. The photopolymer can contain vinyl acetate, epoxy, acryl, or urethane. The volume hologram can be duplicated by a contact copying process using laser. These structures are formed such that interference fringes formed by a designed reconstruction image (corresponding to, for example, first information <NUM> and second information <NUM> shown in <FIG>) and reference light is computed and a structure to be formed on the interface <NUM> of the hologram <NUM> is computed from the interference fringes. In this disclosure, the information used for designing the reconstruction image or designing the optical phase modulation structure <NUM> is called fourth information. The fourth information can be used for comparison with the reconstructed information from the hologram <NUM> acquired by the detection devices <NUM> and 2A shown in <FIG> to determine the correctness of the reconstructed information (whether the hologram has been correctly produced).

The optical phase modulation structure <NUM> formed on the interface <NUM> has a multistep shape referring to <FIG>. The steps may be rounded. In addition, the optical phase modulation structure <NUM> may not have a multistep shape but may have a slope shape. The optical phase modulation structure <NUM> may not have a multistep shape but may have a binary shape. In either case, the optical phase modulation structure <NUM> is structured to reconstruct the reconstruction image on an interface <NUM> (second interface) different from the interface <NUM> in the hologram <NUM>. This makes it easy to detect the reconstructed image described later. The interface <NUM> is a boundary surface between the formation layer <NUM> and a gas phase or vacuum or protective layer. The reference light from a point light source not shown enters the interface <NUM>.

<FIG> is a plan view of an example of the optical phase modulation structure <NUM> formed on the interface <NUM>. The structure shown in <FIG> is an example of a multistep structure used in the hologram <NUM> shown in <FIG>.

The optical phase modulation structure <NUM> can be formed by thermal pressing with a stamper. The stamper can be obtained by electrocasting a plate with projections and recesses formed by laser lithography, electronic beam lithography, ion-beam lithography, or the like. The use of these methods makes it possible to reproducibly form the computed optical phase modulation structure <NUM>. As another method, two-photon lithography using a femtosecond laser may be applied. In the case of using two-photon lithography, the optical phase modulation structure <NUM> may be formed directly on the formation layer <NUM>.

When the formation layer <NUM> is formed from an organic material, the optical phase modulation structure <NUM> can be formed by any of various methods such that an original plate formed by any of the lithographic methods described above is turned into a metal plate by electrocasting or the like, and the formation layer <NUM> is pressed and embossed by the structure on the metal plate. When the organic material for the formation layer <NUM> is a thermoplastic or thermosetting resin, the formation layer <NUM> is embossed under thermal pressure. When the organic material for the formation layer <NUM> is a photosetting resin, the formation layer <NUM> is embossed while being photo-cured under pressure by the use of a light source that emits light conducive to photocuring such as ultraviolet (UV) light.

When the formation layer <NUM> is formed from an inorganic material, the formation layer <NUM> is directly subjected to lithographic treatment by using any of the lithographic methods described above, and then is subjected to chemical etching treatment or physical etching treatment to form the optical phase modulation structure <NUM> on the formation layer <NUM>. Each of these treatments is a wet process or dry process so that etching is performed in a manner suited for the processing method. If the inorganic material can be subjected to a wet process such as a sol-gel process, the formation layer <NUM> can be formed by embossing with a metal plate. The thickness of the formation layer <NUM> can be <NUM> or more to <NUM> or less.

The reflection layer <NUM> can be formed from a material different from the formation layer <NUM> in refractive index. The difference in refractive index between the formation layer <NUM> and the reflection layer <NUM> generates reflection on the interface therebetween, thereby improving reflectance.

The reflection layer <NUM> can be formed from a metallic material and inorganic compound. The reflection layer may be a monolayer or a multilayer. The reflection layer <NUM> may be formed by accumulation. The accumulation may be physical accumulation, chemical accumulation, or both. The physical accumulation may be vacuum evaporation or sputtering. The metallic material may be aluminum, gold, silver, copper, nickel, or the like. The inorganic compound may be oxide, metallic nitride, or metallic sulfide. The oxide may be silicon dioxide (SiO2), titania (TiO2), zirconia (ZrO2), or the like.

The metallic nitride may be titanium nitride (TiN), CaN, or the like. The metallic sulfide may be ZnS or the like. Using these materials for the reflection layer <NUM> improves the reflectance on the interface <NUM> with the formation layer <NUM> as described later. The improvement of the reflectance makes it easy to verify the first information <NUM> and the second information <NUM> reconstructed by the hologram <NUM> described later. The thickness of the reflection layer <NUM> can be <NUM> or more to <NUM> or less.

The additive layer <NUM> can be provided to attach the hologram <NUM> to another medium of base material. The material for the adhesive layer can be a thermoplastic resin. An instance of the thermoplastic resin can be an acrylic resin. The thickness of the adhesive layer can be <NUM> or more to <NUM> or less. The hologram <NUM> having the additive layer <NUM> can be a label. The label can be attached to printed matter. The printed matter with the label can be a banknote, card, booklet page, tag, poster, sign, advertisement, or board.

The hologram <NUM> shown in <FIG> may further be provided with a protective layer on the interface <NUM> side. This protects the hologram <NUM> from physical impact or scratches.

Instances of reconstructed information include graphics, photograph, character, symbol, sign, mark, logo, image, landmark, or code. The code can be a digital code. The code may be machine-readable.

<FIG> are respectively a birds'-eye view and an XZ cross-sectional view of the first information <NUM> that is reconstructed from the hologram <NUM> shown in <FIG>. <FIG> is an XZ cross-sectional view of the first information <NUM> and second information <NUM> that are reconstructed from the hologram <NUM>. The first information <NUM> described in <FIG> is an image that is reconstructed by the optical phase modulation structure <NUM> on the interface <NUM> shown in <FIG> when reference light emitted from a predetermined point light source enters the hologram <NUM> through the interface <NUM> described in <FIG>.

The second information <NUM> described in <FIG> is another image that is reconstructed by the optical phase modulation structure <NUM> on the interface <NUM> shown in <FIG> when reference light emitted from a predetermined point light source enters the hologram <NUM> through the interface <NUM> described in <FIG>. The reconstructed image can be reconstructed using the light obtained through modulation of the reference light incident on the hologram <NUM> by the optical phase modulation structure <NUM>. The first information <NUM> can be formed from a plurality of reconstruction points <NUM>. The second information <NUM> can be reconstructed from a plurality of reconstruction points <NUM>. In other words, the first information <NUM> can be recorded as the plurality of reconstruction points <NUM>. The second information <NUM> can be recorded as the plurality of reconstruction points <NUM>. The hologram information can be digital data.

The digital data can be recorded on a group of reconstruction points, where the individual reconstruction points are bits and the positions of the reconstruction points are bit addresses.

The bits can be recorded, indicating the presence or absence of the reconstruction points, and the brightness, shapes, colors, and others of the reconstruction points. One or two or more bits may be recorded on each of the reconstruction points. One bit on each of the reconstruction points is a single bit, and two or more bits on each of the reconstruction points are multi-bits.

<FIG> describes the first information <NUM> including the reconstruction points <NUM> from the hologram <NUM>. The reconstruction points <NUM> can be arranged along a curved line 30a and a curved 30b to reconstruct the first information <NUM>.

<FIG> show that the first information <NUM> is reconstructed along the curved line 30a and the curved line 30b. However, the reconstruction points <NUM> may be arranged along not curved lines but straight lines to reconstruct the first information <NUM>. In addition, some of the reconstruction points <NUM> may be arranged along axial directions. Specifically, some of the reconstruction points <NUM> may be arranged along a Z axis direction. In this case, the reconstruction of the second information <NUM> is unlikely to be subject to spatial constrains as described later.

Referring to <FIG>, the first information <NUM> is reconstructed at a higher position than the interface 20a that is flush with the interface <NUM> of the hologram <NUM> along the Z axis direction. However, part of the first information <NUM> may be reconstructed at a lower position than the interface 20a. This means that all or part of the first information <NUM> may be reconstructed at a higher position than the interface 20a.

In this case, if the reference light emitted from a predetermined point light source not shown enters through the interface <NUM> different from the interface <NUM> of the formation layer <NUM>, the entirety or part of an image to be reconstructed by the optical phase modulation structure <NUM> on the interface <NUM> is reconstructed as the first information <NUM> on the point light source side relative to the interface <NUM> (or the interface 20a).

<FIG> is an XZ cross-sectional view of the first information <NUM> that is reconstructed from the hologram <NUM>. <FIG> describes the reconstruction points <NUM> that constitute part of the first information <NUM> along the curved line 30c. The reconstruction points <NUM> can be arranged at positions at different distances D1 and D2 from the interface 20a.

Referring to <FIG>, the reconstruction points <NUM> are arranged at the positions at the different distances D1 and D2. However, the reconstruction points <NUM> may be arranged at the same distance. Referring to <FIG>, the first information <NUM> is part of an image that is to be reconstructed from the reconstruction points <NUM> by the optical phase modulation structure <NUM>. The reconstruction points <NUM> each are point information representing dot-like images. The first information <NUM> (part of an image to be reconstructed by the optical phase modulation structure <NUM>) can be reconstructed from the plurality of pieces of point information. The reconstruction points <NUM> as point information can be positioned at the predetermined distances D1, D2, and the like from the interface <NUM> (or the interface 20a).

<FIG> is an XZ cross-sectional view of the reconstruction points <NUM> that are arranged along the curved line 30d as the second information <NUM> behind the interface 20a of the hologram <NUM>, that is, as a virtual image.

This enhances the flexibility of reconstructed information from the hologram <NUM> so that more complicated reconstructed information can be obtained.

Referring to <FIG>, the second information <NUM> is reconstructed behind the interface 20a. However, part of the second information <NUM> may be reconstructed in front of the interface 20a.

The first information <NUM> and the second information <NUM> as the reconstructed information of the hologram <NUM> can be a combination of the reconstruction points <NUM> and <NUM> that are positioned along any of the X, Y, and Z directions. Thus, the reconstructed information can be a three-dimensional image that floats in space. The reconstructed information can be readable or recognizable. The readable reconstructed information can be single characters, numerals, symbols, or a combination of these. The recognizable reconstructed information can be a geometric pattern. The readable reconstructed information and the recognizable reconstructed information may be combined.

The readable reconstructed information can be read visually. The recognizable reconstructed information can add aesthetic features to the hologram <NUM>.

As shown in <FIG>, the reconstruction points <NUM> and <NUM> can be freely arranged in the Z axis direction. Thus, if character information is reconstructed from the reconstruction points <NUM> and <NUM> at different heights on the Z axis, the character information can vary in moving direction or moving amount, or both of them, depending on the observation direction of the hologram <NUM>.

In this case, when the reference light emitted from a predetermined point light source not shown enters through the interface <NUM> different from the interface <NUM> of the formation layer <NUM>, the entirety or part of an image to be reconstructed by the optical phase modulation structure <NUM> on the interface <NUM> is reconstructed as the first information <NUM> on the point light source side relative to the interface <NUM> (or the interface 20a) as described above, and the entirety or part of an image to be reconstructed by the optical phase modulation structure <NUM> on the interface <NUM> is reconstructed as the second information <NUM> on a side opposite to that facing the point light source of the interface <NUM> (or the interface 20a).

As shown in <FIG>, the second information <NUM> is part of an image that is reconstructed from the reconstruction points <NUM> by the optical phase modulation structure <NUM>. The reconstruction points <NUM> each are point information representing dot-like images. The second information <NUM> (part of an image to be reconstructed by the optical phase modulation structure <NUM>) can be reconstructed from the plurality of pieces of point information. The reconstruction points <NUM> as point information can be positioned at the predetermined distances from the interface <NUM> (or the interface 20a).

<FIG> describes that the reconstruction points <NUM> are acquired by an image sensor <NUM> when light from a point light source LS is applied to the hologram <NUM> shown in <FIG>. The point light source LS and the image sensor <NUM> may be separately installed or are desirably incorporated in the detection device. The point light source LS shown in <FIG> corresponds to the point light source <NUM> shown in <FIG>. The image sensor <NUM> shown in <FIG> corresponds to the image sensor <NUM> shown in <FIG>.

The point light source LS and the image sensor <NUM> are installed in such a manner as to form a specific angle. The angle is designed at the computation of the optical phase modulation structure <NUM> for reconstructing the hologram <NUM>. Referring to <FIG>, the reconstruction points <NUM> arranged in a specular direction of the point light source LS are acquired by the image sensor <NUM>. However, the point light source LS, the reconstruction points <NUM>, and the image sensor <NUM> may be in an angular relationship under a condition other than specular reflection. The angular relationship is designed during computation of the optical phase modulation structure <NUM>.

The point light source LS can be a miniature bulb or a light-emitting diode (LED) light source. The LED light source has a narrow wavelength width and a small size, thereby to sharpen a reconstructed image. The LED light source as the point light source LS can reconstruct the reconstruction information (the first information <NUM>, the second information <NUM>, and the like) contained in the hologram <NUM> detectable by the image sensor. The LED light source can be the point light source LS in colors of red, blue, green, and the like so that the reconstruction information (the first information <NUM>, the second information <NUM>, and the like) of the hologram <NUM> can be colored.

The image sensor <NUM> is a one-dimensional image sensor or, according to the claimed invention, a two-dimensional image sensor that is capable of measuring light intensity. The two-dimensional image sensor can capture an image of a certain aspect of the reconstructed information from the hologram <NUM>. The two-dimensional image sensor can be a charge-coupled device (CCD) two-dimensional image sensor, a complementary metal oxide semiconductor (CMOS) two-dimensional image sensor, or, according to the claimed invention, a thin film transistor photosensor. As such an image sensor, the image sensor <NUM> can receive and detect the reconstruction points <NUM>. The image sensor has a plurality of pixels that detect light intensity. The thin film transistor photosensor is a double-gate thin film transistor photosensor.

In a not claimed embodiment, the image sensor <NUM> may not be a one-dimensional image sensor or a two-dimensional image sensor but may be a phototransistor or a photodiode. A plurality of phototransistors or photodiodes may be aligned.

The image sensor <NUM> is a sensor formed on a substrate. The sensor on the substrate is a photosensor. The photosensor is formed from a thin film transistor. The thin film transistor can be a circuit of amorphous silicon or polysilicon. The thin film transistor is formed with the photosensor as pixels. The pixels in the photosensor are disposed in an array. When the substrate of the image sensor <NUM>, as for the claimed invention, is a transparent substrate, one surface of the substrate can be a light-receiving surface that receives an image of a hologram and the other surface can be an entrance surface through which the reference light enters. Using a transparent substrate as the substrate of the image sensor <NUM> makes it possible to obtain a transmissive image sensor. Each pixel in the photosensor is a transmissive image sensor <NUM> that is formed from a double-gate thin film transistor photosensor. The double-gate thin film transistor photosensor can adjust a dynamic range or light sensitivity, or both of them. Thus, the double-gate thin film transistor photosensor can adjust the dynamic range or sensitivity, or both of a hologram image with large brightness differences according to the brightness of the hologram, thereby accomplishing image capture at a high S/N ratio.

The image sensor <NUM> is based on the transmissive image sensor <NUM> that is formed on the transparent substrate as shown in <FIG> and <FIG> and includes a thin film transistor photosensor with one surface of the substrate as a light-receiving surface and the other surface through which the reference light enters. The transmissive image sensor <NUM> corresponds to the image sensor <NUM> shown in <FIG> or the image sensor 5a shown in <FIG>. This provides light transparency to the two-dimensional image sensor. Thus, the interface of the two-dimensional image sensor (for example, a light-receiving interface <NUM> shown in <FIG>) constitutes a two-dimensional scan surface to perform scanning with intermittent position changes in the height direction. Accordingly, when the reconstruction points <NUM> for reconstructing the first information <NUM> concentrate on the two-dimensional scan surface, the concentrating reconstruction points <NUM> and the other reconstruction points <NUM> can be separately acquired.

<FIG> are respectively a partially enlarged cross-sectional view (<FIG>) of the image sensor <NUM> and the reconstruction points <NUM> shown in <FIG> and a plan view of a light-receiving interface <NUM> of the image sensor <NUM> (<FIG>).

<FIG> describes that reconstructed points 40a, 40b, and 40c are applied to the light-receiving interface <NUM> of the image sensor <NUM>. <FIG> also shows an example in which the reconstruction point 40c is focused on the light-receiving interface <NUM>. The reconstruction points 40a and 40b can both focused on a portion in front of the light-receiving interface <NUM>. The reconstruction point 40c can be focused on the light-receiving interface <NUM>. The reconstruction points 40a, 40b, and 40c can be focused on corresponding reconstruction points via light paths <NUM>.

<FIG> describes the intensity distribution of the reconstruction points 40a, 40b, and 40c shown in <FIG> on the light-receiving interface <NUM>. The regions where the light of the reconstruction points is detected on the light-receiving interface <NUM> are light-receiving regions. The light-receiving regions corresponding to the reconstruction points 40a, 40b, and 40c are respectively regions 45a, 45b, and 45c. Since the reconstruction point 40c is focused on the light-receiving interface <NUM> as shown in <FIG>, the region 45c is the smallest in size and high in intensity. On the other hand, the reconstruction point 40a is focused on the corresponding region 45a at a position separated from the light-receiving interface <NUM>, and thus the region 45a is large in size and low in intensity. Thus, the distances between the reconstruction points and the light-receiving interface <NUM> can be measured. The positions of the reconstruction points on the light-receiving interface <NUM> can be measured from the centers of the corresponding light-receiving regions.

In this manner, the positions of the reconstruction points <NUM> can be detected by the center positions of the light-receiving regions, the sizes of the light-receiving regions <NUM> (the regions 45a, 45b, and 45c) on the light-receiving interface <NUM>, and the intensities of the regions <NUM>. This makes it possible to detect the spatial positions of the reconstruction points <NUM> constituting the first information <NUM> obtained from the hologram <NUM> by a combination of the point light source LS and the image sensor <NUM>.

<FIG> are respectively a schematic cross-sectional view of a double-gate thin film transistor in a double-gate thin film transistor sensor, an equivalent circuit diagram, and a schematic circuit diagram of the transmissive image sensor <NUM>. The double-gate thin film transistor sensor is the transmissive image sensor <NUM>.

<FIG> is a schematic cross-sectional view of a structure of the double-gate thin film transistor. As shown in <FIG>, the double-gate thin film transistor <NUM> includes a semiconductor layer <NUM>, a source electrode <NUM>, a drain electrode <NUM>, a transparent insulating film <NUM>, a top gate insulating film <NUM>, a bottom gate insulating film <NUM>, ohmic contact layers <NUM> and <NUM>, an insulating substrate <NUM>, a protective insulating film <NUM>, a top gate electrode <NUM>, and a bottom gate electrode <NUM>.

The semiconductor layer <NUM> includes amorphous silicon in which electron-hole pairs are generated when visible light is incident thereon. The source electrode <NUM> and the drain electrode <NUM> are respectively formed on the ohmic contact layers <NUM> and <NUM>. The ohmic contact layers <NUM> and <NUM> are provided on ends of the semiconductor layer <NUM>. The top gate electrode <NUM> is formed above the semiconductor layer <NUM> with the transparent insulating film <NUM> therebetween. The bottom gate electrode <NUM> is formed under the semiconductor layer <NUM> with the bottom gate insulating film <NUM> therebetween. The protective insulating film <NUM> is provided on the top gate electrode <NUM>.

Referring to <FIG>, the top gate electrode <NUM>, the top gate insulating film <NUM>, the bottom gate insulating film <NUM>, and the protective insulating film <NUM> are all formed from materials with high transmittance of visible light exciting the semiconductor layer <NUM>. On the other hand, the bottom gate electrode <NUM> is formed from a material blocking transmission of the visible light. Accordingly, the double-gate thin film transistor <NUM> is structured to detect only the irradiation light entering from the upper side shown in the diagram. Specifically, the double-gate thin film transistor <NUM> has on the insulating substrate <NUM> a structure in which two metal oxide semiconductor (MOS) transistors are combined with the semiconductor layer <NUM> as a common channel region. The two MOS transistors include: an upper MOS transistor formed from the semiconductor layer <NUM>, the source electrode <NUM>, the drain electrode <NUM>, and the top gate electrode <NUM>; and a lower MOS transistor formed from the semiconductor layer <NUM>, the source electrode <NUM>, the drain electrode <NUM>, and the bottom gate electrode <NUM>. The insulating substrate <NUM> is a transparent substrate such as a glass substrate or a film substrate. This double-gate thin film transistor <NUM> is generally represented by an equivalent circuit as shown in <FIG>. In the circuit diagram, TG denotes the top gate terminal, BG the bottom gate terminal, S the source terminal, and D the drain terminal.

The bottom gate electrode <NUM> may be formed from a material blocking transmission of visible light. The image sensor can be a transmissive image sensor if the pattern width is hard to visually recognize, specifically <NUM> or less, or if the aperture ratio with a two-dimensional array of the double-gate thin film transistors <NUM> is <NUM>% or more.

Next, the transmissive image sensor <NUM> formed by two-dimensionally arraying the double-gate thin film transistors <NUM> will be briefly described with reference to the drawings. <FIG> is a schematic configuration diagram of the transmissive image sensor <NUM> formed by two-dimensionally arraying the double-gate thin film transistors <NUM>. As shown in <FIG>, the transmissive image sensor <NUM> is also called a photosensor set and roughly includes a photosensor array <NUM>, top gate lines <NUM>, bottom gate lines <NUM>, a top gate driver <NUM>, a bottom gate driver <NUM>, data lines <NUM>, and an output circuit unit <NUM>.

The photosensor array <NUM> is formed by aligning a large number of double-gate thin film transistors <NUM> in a matrix with n rows and m columns. In this case, one double-gate thin film transistor <NUM> constitutes one pixel. The plurality of top gate lines <NUM> connects top gate terminals TG of the plurality of double-gate thin film transistors <NUM> in the corresponding columns in the column direction. The plurality of bottom gate lines <NUM> connects bottom gate terminals BG of the plurality of double-gate thin film transistors <NUM> in the corresponding columns in the column direction. The top gate lines <NUM> are connected to the top gate driver <NUM>. The bottom gate lines <NUM> are connected to the bottom gate driver <NUM>. The plurality of data lines <NUM> connects drain terminals D of the plurality of double-gate thin film transistors <NUM> in the corresponding rows in the row direction. The data lines <NUM> are connected to the output circuit unit <NUM>.

In this configuration, the transmissive image sensor <NUM> implements the function of a photosensor by applying a voltage from the top gate driver <NUM> to the top gate terminals TG, and implements the reading function by applying a voltage from the bottom gate driver <NUM> to the bottom gate terminals BG and receiving detection signals into the output circuit unit <NUM> via the data lines <NUM> and outputting the signals as serial data. That is, one double-gate thin film transistor <NUM> serves as a double-gate thin film transistor photosensor that constitutes one pixel in the image sensor.

The double-gate thin film transistors each can implement a highly sensitive photosensor with a high S/N ratio in a simple pixel circuit on the light-transmissive substrate such as a glass substrate, thereby realizing a high-performance and high-transmittance image sensor <NUM>. The double-gate thin film transistors can be formed from amorphous silicon.

The transmissive image sensor <NUM> shown in <FIG> is incorporated into detection devices <NUM> and <NUM> described later with reference to <FIG> and <FIG> such that the point light source is positioned on the insulating substrate <NUM> side and the hologram <NUM> is positioned on the protective insulating film <NUM> (the light-receiving interface <NUM>) side in <FIG>. The detection device <NUM> shown in <FIG> corresponds to the detection device <NUM> shown in <FIG>, and the detection device <NUM> shown in <FIG> corresponds to the detection device 2a shown in <FIG>.

Setting the insulating substrate <NUM> as a transmissive substrate formed from a thin glass plate, a light-transmissive resin film, or the like makes it possible to reduce the thickness of the entire transmissive image sensor <NUM> and laminate a plurality of transmissive image sensors <NUM> as in the claimed invention and as described later. This achieves the simplified internal configuration and miniaturization of the detection device <NUM> and others.

<FIG> schematically show a positional relationship between the detection device <NUM> and the hologram <NUM> on the XZ cross section when the point light source LS and the transmissive image sensor <NUM> are used. The detection device <NUM> shown in <FIG> includes the point light source LS and the transmissive image sensor <NUM>.

<FIG> shows the hologram <NUM> and the transmissive image sensor <NUM> that are provided parallel with each other. <FIG> shows the hologram <NUM> and a transmissive image sensor 60a that are inclined to face each other at an angle θ. <FIG> shows, according to the claimed invention, transmissive image sensors 60b, 60c, and 60d that are laminated in the Z axis direction. The point light source LS shown in <FIG> corresponds to the point light source <NUM> shown in <FIG>. The transmissive image sensors 60a to 60d shown in <FIG> are configured in the same manner as the transmissive image sensor <NUM> shown in <FIG>. The transmissive image sensors <NUM>, 60a and a transmissive image sensor group <NUM> correspond to the image sensor 5a shown in <FIG>.

Referring to <FIG>, the image sensor has light transparency, whereby the point light source LS and the transmissive image sensor <NUM> can be placed on the same optical axis. This achieves miniaturization and simplification of the detection device <NUM>.

Referring to <FIG>, it is possible to obtain by the transmissive image sensor <NUM> an XY plan view based on first information <NUM> reconstructed from the hologram <NUM> on the light-receiving interface <NUM> on the side where the transparent gate electrode (the top gate electrode <NUM>) is provided. The first information <NUM> corresponds to the first information <NUM> shown in <FIG> and others.

The Z position of the light-receiving interface <NUM> can be altered by changing the distance between the hologram <NUM> and the transmissive image sensor <NUM>, which makes it possible to acquire a plurality of XY plan views at different Z positions based on the first information <NUM>.

Spatial information in the first information <NUM> can be acquired by sequentially changing the distance between the hologram <NUM> and the transmissive image sensor <NUM> by the use of the detection device <NUM> shown in <FIG>. This distance can be shifted by a device that controls the position of the transmissive image sensor <NUM> in the detection device <NUM>. The spatial information can be a set of values associated with coordinates in a three-dimensional space. The spatial information is implemented as a hologram that reconstructs reconstruction points in the space. The spatial information reconstructed by a hologram is not planar information but three-dimensional information that varies depending on illumination conditions and other factors. Thus, the spatial information cannot be copied from a two-dimensional captured image of the hologram. The spatial information reconstructed by a hologram cannot be copied by a photocopier unlike a printable QR code (registered trademark). Therefore, it is possible to prevent illicit copying and abuse of the spatial information reconstructed by a hologram.

Referring to <FIG>, the transmissive image sensor 60a is inclined at the angle θ relative to the hologram <NUM>, which makes it possible to acquire the first information <NUM> corresponding to the light-receiving interface 61a.

Configuring the detection device <NUM> as shown in <FIG> makes it possible to acquire the spatial information of the first information <NUM> only by changing the X, Y positions of the hologram <NUM>. This eliminates the need to provide an adjuster for the transmissive image sensor <NUM> in the detection device <NUM> and allows the detection device <NUM> to be installed at a fixed position.

Referring to <FIG>, the inclination angle θ of the transmissive image sensor 60a is greater than <NUM> degree and equal to or smaller than <NUM> degrees, and, more specifically, can be <NUM> to <NUM> degrees inclusive. When the inclination angle θ is <NUM> degrees or more, its sin is <NUM> or more so that information on height equivalent to half a length L of the transmissive image sensor 60a can be acquired. When the inclination angle θ is <NUM> degrees, information on height corresponding to the length L of the transmissive image sensor 60a can be acquired. The spatial information of the first information <NUM> can be acquired using the detection device <NUM> shown in <FIG> by sequentially changing the XY positions of the detection device <NUM> or by sequentially changing the XY positions of the hologram <NUM>.

Referring to <FIG>, the detection device <NUM>, the detection device according to the claimed invention, has the transmissive image sensor group <NUM> in which transmissive image sensors 60b, 60c, and 60d are laminated therein. This makes it possible to acquire collectively the spatial information of the first information <NUM>. Referring to <FIG>, the three transmissive image sensors are laminated. However, the transmissive image sensor group <NUM> may include at least two or more transmissive image sensors.

<FIG> is a hardware block diagram, which shows a detection device <NUM> as a configuration example of the detection devices <NUM> and <NUM>. The detection device <NUM> corresponds to the detection devices <NUM> and 2a shown in <FIG>.

As shown in <FIG>, the detection device <NUM> can include a sensor unit <NUM>, a light source unit <NUM>, a control unit <NUM>, and an operation unit <NUM>. The sensor unit <NUM>, the light source unit <NUM>, the control unit <NUM>, and the operation unit <NUM> can be connected together via a bus <NUM>. The bus <NUM> can electrically connect various functional units to transfer data or the like.

The sensor unit <NUM> optically reads the first information <NUM>, <NUM>, and <NUM> (<FIG>) and the third information <NUM> (<FIG>) reconstructed by the hologram <NUM> or the like, and converts the read information into electrical signals. The sensor unit <NUM> corresponds to the image sensors <NUM> and 5a shown in <FIG>.

The light source unit <NUM> is used to read optical information by the sensor unit <NUM>. The light source unit <NUM> corresponds to the point light source <NUM> shown in <FIG>.

The control unit <NUM> controls the detection device <NUM>. The control unit <NUM> can include a main control unit <NUM> containing a central processing unit (CPU) and others, a power source unit <NUM>, a communication unit <NUM>, and a storage <NUM>.

The storage <NUM> may be provided with a read only memory (ROM) <NUM> or a random access memory (RAM) <NUM>, or both of them. The ROM <NUM> is a nonvolatile memory that can store basic information such as programs. The RAM <NUM> is a volatile memory as a work memory where the main control unit <NUM> reads and executes programs and data. The RAM <NUM> can store various kinds of information such as data acquired by the sensor unit <NUM> and data having undergone predetermined conversion processing. The RAM <NUM> also store data having been processed by external terminals as necessary. The RAM <NUM> may be a flash memory or an external memory medium.

The operation unit <NUM> may receive operation instructions. The operation unit <NUM> may be a touch panel. The operation unit <NUM> may display information and input data.

<FIG> describes verification of authenticity of reconstructed information from a hologram <NUM> at the time of production, and <FIG> describes verification of authenticity of reconstructed information from a hologram <NUM> attached to a medium <NUM>. The hologram <NUM> and the hologram <NUM> are configured in the same manner as the hologram <NUM> and correspond to the hologram <NUM> shown in <FIG>.

Referring to <FIG>, the detection device <NUM> is provided to, when a carrier film <NUM> including the holograms <NUM> is conveyed at the time of production, detect and examine the reconstructed information from the holograms <NUM>. The detection device <NUM> has the point light source LS and the image sensor <NUM> incorporated therein. When the light from the point light source LS is applied to the hologram <NUM>, the reconstructed information from the hologram <NUM> can be acquired by the image sensor <NUM> or the transmissive image sensor <NUM>.

<FIG> shows that the reconstructed information from the hologram <NUM> attached to the display medium <NUM> is acquired by the detection device <NUM>. The detection device <NUM> has the point light source LS and the transmissive image sensor <NUM> coaxially incorporated therein.

As shown in <FIG> and <FIG>, the reconstructed information from the holograms <NUM> and <NUM> on the display media at or after the production can be acquired by the detection devices <NUM> and <NUM>.

Thus, acquiring the information visually observed from the holograms <NUM> and <NUM> by the detection devices <NUM> and <NUM> and comparing the acquired reconstructed information to design information corresponding to the fourth information used at the computation of the optical phase modulation structure <NUM> constituting the holograms <NUM> and <NUM> makes it possible to determine whether the holograms <NUM> and <NUM> have been correctly manufactured.

Both the first information <NUM> reconstructed in front of the interface 20a of the holograms <NUM> and <NUM> and the second information <NUM> reconstructed behind the interface 20a can be inspected by visual observation of the holograms <NUM> and <NUM>. On the other hand, the first information <NUM> or only part of the first information <NUM> can be acquired by the use of the detection devices <NUM> and <NUM>.

This makes the information obtained by the visual inspection and the information obtained by the detection devices <NUM> and <NUM> different. Counterfeiting of the holograms <NUM> and <NUM> would require producing holograms that reconstruct both the information obtained by visual inspection and the information obtained by detection devices. Since it is hard to produce such holograms, the holograms <NUM> and <NUM> are highly counterfeit- resistant.

<FIG> describes a hologram <NUM> that, when irradiated with reference light from above in the Z axis direction, reconstructs the first information <NUM> and the third information <NUM> in a positive direction along the Z axis from the interface 20a of the hologram and reconstructs second information <NUM> in a negative direction. The hologram <NUM> is configured in the same manner as the hologram <NUM>, and corresponds to the hologram <NUM> described in <FIG>. The first information <NUM> corresponds to the first information <NUM> and the first information <NUM>, and the second information <NUM> corresponds to the second information <NUM>.

Reconstruction points <NUM> are positioned along a curved line 90a to reconstruct the first information <NUM>, reconstruction points <NUM> are positioned along a curved line 90b to reconstruct the second information <NUM>, and reconstruction points <NUM> are positioned along a straight line 90c to reconstruct the third information <NUM>. The surface shapes formed by the curved line 90a, 90b and the straight line 90c are not limited to curved surface or planar surface but may be any surface shapes that are capable of indicating the first information <NUM>, the second information <NUM>, and the third information <NUM>, respectively.

The positions of the reconstruction points <NUM> constituting the first information <NUM> and the reconstruction points <NUM> constituting the third information <NUM> can be substantially the same on the XY plane of the reconstruction points <NUM> and <NUM> (they overlap in the horizontal direction), and the distance between the reconstruction points <NUM> and the reconstruction points <NUM> along the Z axis can be within <NUM>, more specifically, within <NUM>. This makes it possible to conceal and hide the third information <NUM> behind the first information <NUM> at the time of visual observation of the hologram <NUM>.

If the first information <NUM> is reconstructed at random on the XY plane by the plurality of reconstruction points <NUM>, the third information <NUM> may also be reconstructed at random by the plurality of reconstruction points <NUM> so that the reconstruction points <NUM> are arranged at substantially the same positions as the reconstruction points <NUM> constituting the first information <NUM> on the XY plane. This also makes it possible to conceal and hide the third information <NUM> behind the first information <NUM> at the time of visual observation of the hologram <NUM>.

The hologram <NUM> shown in <FIG> can be verified for authenticity by the detection devices <NUM> and <NUM> in such a manner as to acquire the first information <NUM> and the third information <NUM> at the same time by the detection devices <NUM> and <NUM> and use the third information <NUM> having been hidden at the time of visual observation as the key element of the authenticity verification. The hologram <NUM> can be verified for authenticity by collating the third information <NUM> and the first information <NUM>. The third information <NUM> can be generated based on the first information <NUM>. The third information <NUM> can be generated based on the first information <NUM> by the use of a secret key. The third information <NUM> and the first information <NUM> can be collated by the use of a public key corresponding to the secret key. The secret key can be made unidentifiable from the public key within a realistic time frame. The third information <NUM> may be generated based on the first information <NUM> by the use of a hash function.

As described above, the authenticity of the hologram <NUM> can also be judged by comparing and analyzing the design information corresponding to the fourth information used at the computation of the optical phase modulation structure <NUM> included in the hologram <NUM> and the information acquired by the detection devices <NUM> and <NUM>.

In this case, when reference light emitted from a predetermined point light source not shown enters through the interface <NUM> different from the interface <NUM> of the formation layer <NUM>, all or part of an image to be reconstructed by the optical phase modulation structure <NUM> on the interface <NUM> is reconstructed as the first information <NUM> on the curved line 90a (curved surface (first surface) along the interface <NUM> in the two-dimensional cross section) positioned on the point light source side relative to the interface <NUM> (or the interface 20a). Further, all or part of an image to be reconstructed by the optical phase modulation structure <NUM> on the interface <NUM> is reconstructed as the third information <NUM> on the curved line 90a (planar surface (second surface) along the interface <NUM> in the two-dimensional cross section) on the point light source side relative to the interface <NUM> (or the interface 20a). The first surface and the second surface are different from each other.

As shown in <FIG>, the first information <NUM> is part of an image to be reconstructed by the optical phase modulation structure <NUM> and can be recorded as the reconstruction points <NUM>. The reconstruction points <NUM> are each point information so that the first information <NUM> (part of an image to be reconstructed by the optical phase modulation structure <NUM>) can be recorded as a plurality of pieces of point information. The second information <NUM> is part of an image to be reconstructed by the optical phase modulation structure <NUM> and can be recorded as the reconstruction points <NUM>. The reconstruction points <NUM> are each point information so that the second information <NUM> (part of an image to be reconstructed by the optical phase modulation structure <NUM>) can be recorded as a plurality of pieces of point information. The third information <NUM> is part of an image to be reconstructed by the optical phase modulation structure <NUM> and can be recorded as the reconstruction points <NUM>. The reconstruction points <NUM> are each point information so that the third information <NUM> (part of an image to be reconstructed by the optical phase modulation structure <NUM>) can be recorded as a plurality of pieces of point information. The reconstruction points <NUM> as point information can be arranged at predetermined distances from the interface <NUM> (or the interface 20a). The reconstruction points <NUM> as point information can be arranged at the predetermined distances from the interface <NUM> (or the interface 20a). The reconstruction points <NUM> as point information can be positioned at the predetermined distances from the interface <NUM> (or the interface 20a).

When the reconstruction points <NUM> constituting the first information <NUM> and the reconstruction points <NUM> constituting the third information <NUM> are at substantially the same positions on the XY plane (they overlap in the horizontally direction), the horizontal positions of all or some of the plurality of pieces of point information for reconstructing the first information <NUM> relative to the interface <NUM> (or the interface 20a) and the horizontal positions of all or some of the plurality of pieces of point information for reconstructing the third information <NUM> relative to the interface <NUM> (or the interface 20a) can overlap each other.

The hologram will be described based on experimental results shown in <FIG>.

<FIG> is a photograph of the hologram <NUM> that is irradiated with reference light from a point light source, which is an image of the outer appearance of the hologram <NUM> when visually observed. The hologram <NUM> can reconstruct a star pattern as an example of the first information <NUM> and can reconstruct a moon pattern as an example of the second information <NUM>.

The hologram <NUM> as shown in <FIG> can be produced in the manner as described below. First, drawing data of the optical phase modulation structure <NUM> is computed by a computer such that the hologram <NUM> reconstructs the star pattern as the first information <NUM> and the moon pattern as the second information <NUM>. The drawing data obtained from the computation results is used to draw the mold of the optical phase modulation structure <NUM> on a resist plate by electron-beam lithography and form it into a glass substrate. Then, the glass substrate is subjected to electrocasting, thereby obtaining a metal plate.

Next, a carrier film is coated with resin to form a pre-mold film, and the pre-mold film is embossed with the metal plate to produce a molded film with the optical phase modulation structure <NUM>. Then, a reflection layer is deposited on the molded film to obtain the hologram <NUM>.

The point light source LS and the transmissive image sensor <NUM> are coaxially provided on the upper surface of the produced hologram <NUM>. The hologram <NUM> and the transmissive image sensor <NUM> are brought into close contact with each other. Then, the first information <NUM> reconstructed by the hologram <NUM> is obtained via the transmissive image sensor <NUM> at different distances of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> between the hologram <NUM> and the transmissive image sensor <NUM>. <FIG> shows image information acquired by the transmissive image sensor <NUM> at the different distances between the hologram <NUM> and the transmissive image sensor <NUM>.

The star pattern as the first information <NUM> observed as shown in <FIG> can be acquired by the transmissive image sensor <NUM> as shown in <FIG>. On the other hand, the moon pattern as the second information <NUM> is not acquired.

Referring to <FIG>, the star pattern as the first information <NUM> can be acquired without blurring at the distance of <NUM> between the hologram <NUM> and the transmissive image sensor <NUM>. The distance of <NUM> matches the position of the reconstructed information of the star pattern corresponding to the first information <NUM> that was set at the time of computation of the optical phase modulation structure <NUM> constituting the hologram <NUM>, so that it can be seen that the hologram <NUM> is properly produced.

A detection set will be described with reference to <FIG>.

<FIG> describes that a star-shaped three-dimensional image corresponding to the first information <NUM>, <NUM> or the third information <NUM> is constructed by irradiating the hologram <NUM> with light from a point light source at a position separated by a distance D from the topmost surface of the hologram <NUM>.

<FIG> describe that the holograms <NUM> are attached to the medium <NUM>. <FIG> describes that the transmissive image sensor <NUM> in the detection device <NUM> is substantially parallel to the medium <NUM> and the hologram <NUM> and that part of the star-shaped three-dimensional image is acquired by the light-receiving interface <NUM> of the transmissive image sensor <NUM>.

Similarly, referring to <FIG>, the transmissive image sensor <NUM> is positioned along a direction orthogonal to the medium <NUM>, which makes it possible to acquire information at the intersection of the light-receiving interface <NUM> of the transmissive image sensor <NUM> and the star-shaped three-dimensional image. Referring to <FIG>, the elevation and azimuth of the transmissive image sensor <NUM> take specific values, which makes it possible to acquire information at the intersection of the light-receiving interface <NUM> of the transmissive image sensor <NUM> and the star-shaped 3D image as in the case described above.

The hologram <NUM> can be reconstructed by using the fourth information that was used to design the first information <NUM>, <NUM> or the third information <NUM>. The use of the fourth information makes it possible to estimate information corresponding to the azimuth and elevation of the transmissive image sensor <NUM> shown in <FIG> and <FIG>. Collating the estimated information and the information actually obtained by the transmissive image sensor <NUM> makes it possible to determine whether the hologram <NUM> and the medium <NUM> are authentic.

In the case of verification of the hologram <NUM> and the medium <NUM> by using the detection device <NUM>, the change in one or both of the elevation and azimuth of the transmissive image sensor <NUM> in the detection device <NUM> can be used as one key element. This provides complexity to the information to be verified.

The foregoing example has components and procedures as described below. Specifically, the detection device <NUM> and the detection device <NUM> shown in <FIG> and others include the transmissive image sensor <NUM> capable of measuring light intensity (the image sensor of the of the claimed invention comprises two or more laminated, two-dimensional, transmissive image sensors) and the point light source LS, and detect, by the transmissive image sensor <NUM>, the first information <NUM> reconstructed by the hologram <NUM> and the like, the third information <NUM> and the like reconstructed by the holograms <NUM>, <NUM>, and the like. The transmissive image sensor <NUM> can be a one-dimensional image sensor or, as claimed, a two-dimensional image sensor. The transmissive image sensor <NUM> is a a double-gate image sensor that has pixels formed from double-gate transistor photosensors.

As shown in <FIG>, the transmissive image sensor <NUM> is a two-dimensional image sensor that has pixels formed from double-gate thin film transistor photosensors having the top-gate electrode <NUM> (light-transmissive gate electrode) and the bottom-gate electrode <NUM> (non-light-transmissive gate electrode) on the insulating substrate <NUM> (light-transmissive substrate). The pixels are each configured such that the protective insulating film <NUM> and the top-gate electrode <NUM> (light-transmissive gate electrode) are arranged in this order on the front surface of the transmissive image sensor <NUM> facing the hologram <NUM>, <NUM> and that the top gate insulating film <NUM> and the transparent insulating film <NUM> (insulating films), the semiconductor layer <NUM> (semiconductor film), the bottom gate insulating film <NUM> (insulating film), and the bottom gate electrode <NUM> (non-light-transmissive gate electrode) are arranged in this order from the front surface of the transmissive image sensor <NUM>. The insulating substrate <NUM> (light-transmissive substrate) is an insulating substrate or the like formed of a thin glass plate. The insulating substrate <NUM> (light-transmissive substrate) is an insulating substrate or the like formed of a light-transmissive resin film.

In the detection device <NUM> shown in <FIG>, <FIG>, and others, the optical axis direction of the point light source LS and the normal direction of the transmissive image sensor <NUM> (two-dimensional image sensor) with pixels formed from double-gate thin film transistor photosensors are coaxially positioned as shown in <FIG>, <FIG>, and others.

In the detection device <NUM> shown in <FIG>, <FIG>, and others, according to the claimed invention, two or more transmissive image sensors <NUM> (two-dimensional image sensors) with pixels formed from double-gate thin film transistor photosensors are laminated as shown in <FIG>.

The detection device <NUM> shown in <FIG>, <FIG>, and others includes the transmissive image sensor <NUM> (two-dimensional image sensor) and the point light source LS, and detects the light intensity of the point information for reconstructing the first information <NUM> or the third information <NUM> from the hologram <NUM> or the like shown in <FIG> by the transmissive image sensor <NUM> (image sensor), thereby to acquire the position of the point information along the normal direction of the two-dimensional image sensor.

According to the method for verifying authenticity of a hologram described above with reference to <FIG>, <FIG>, and others, the detection device <NUM> or <NUM> includes the transmissive image sensor <NUM> (image sensor) capable of measuring light intensity and the point light source LS, the transmissive image sensor <NUM> (image sensor) is a two-dimensional image sensor with pixels formed from double-gate transistor photosensors, and the detection device <NUM> or <NUM> detecting by the transmissive image sensor <NUM> (image sensor) the first information <NUM> reconstructed by the hologram <NUM> or the like shown in <FIG> is used to determine whether the first information <NUM> is authentic via the steps of: acquiring position information of the point information in the first information <NUM>; and comparing the first information <NUM> acquired by the detection device <NUM> or <NUM> with the fourth information used to design the optical phase modulation structure <NUM> for reconstructing the first information <NUM>. The information detected by the image sensor is part of the information recorded as the hologram <NUM>. Thus, it is hard to obtain information for reconstructing the hologram <NUM> from the detected information. On the other hand, it is easy to generate information to be detected by the image sensor from the information recorded on the hologram <NUM>. Thus, a person having the information recorded on the hologram <NUM> can generate the information to be detected by the image sensor and compare the information actually detected by the image sensor with the generated information to verify whether the information detected by the image sensor is authentic.

This prevents counterfeiting of the hologram <NUM> from the detected information. The reconstruction points of the hologram <NUM> is arranged three-dimensionally. This makes it harder to reconstruct the information of the hologram <NUM> from the detected information.

According to the method for verifying authenticity of a hologram described above with reference to <FIG>, <FIG>, and others, the detection device <NUM> or <NUM> includes the image sensor <NUM> capable of measuring intensity and the point light source LS. The image sensor is the transmissive image sensor <NUM>. The transmissive image sensor <NUM> is a two-dimensional image sensor that has pixels formed from double-gate transistor photosensors and comprises, according to the claimed invention, two or more laminated two-dimensional image sensors. The hologram <NUM> can be authenticated by using the detection device <NUM> or <NUM> configured to detect, using the image sensor <NUM>, the third information <NUM> reconstructed from the hologram <NUM> as shown in <FIG> via the step of verifying the authenticity of the third information <NUM>.

According to the method for verifying authenticity of a hologram described above with reference to <FIG>, <FIG>, and others, a detection device <NUM> or <NUM> including the image sensor <NUM> capable of measuring intensity and the point light source LS can be used. The image sensor is the transmissive image sensor <NUM>. The transmissive image sensor <NUM> is a two-dimensional image sensor with pixels formed from double-gate transistor photosensors and comprises, according to the claimed invention, two or more laminated two-dimensional image sensors. The hologram <NUM> described in <FIG> can be authenticated by the use of the detection device <NUM> or <NUM> configured to detect by the image sensor <NUM> the third information <NUM> reconstructed from the hologram <NUM> via the steps of: moving one or both of the elevation and azimuth of the image sensor <NUM> at a specific angle; acquiring by the image sensor <NUM> the first information <NUM> or the third information <NUM> reconstructed from the hologram <NUM> or the like shown in <FIG>; computing prediction information obtained by the image sensor <NUM> from the information of the elevation and azimuth based on the fourth information used to design the optical phase modulation structure <NUM> for reconstructing the first information; and comparing the prediction information with the first information <NUM> or the third information <NUM> obtained by the image sensor <NUM> to verify authenticity of the information obtained by the image sensor <NUM> (image sensor).

The hologram, used in the claimed detection set, makes different the information obtained by a person's visual observation and the information obtained by a reading device such as a detection device. Therefore, the hologram can be applied to provide optical effects for anti-counterfeiting, detection devices, and methods for verifying authenticity, and can be used as a hologram that protects securities, certificates, brand-name goods, high-priced merchandise, electronic devices, and values and information contained in articles such as personal authentication media. Encoding the information added to the hologram as a bar code makes it possible to obtain a mechanical authentication set using a reading device with a photographing function, such as cameras, mobile phones, and smartphones.

The detection device according to the present disclosure can be miniaturized and thus can be used not only as a detection device for authenticity verification but also as a device for product quality control of holograms at the time of production.

The present disclosure also allows visual observation of three-dimensional reconstructed information and thus is applicable to purposes other than the anti-counterfeiting described above. For example, it is also applicable to toys, educational tools, decorative accessories of merchandise, posters, and others.

The foregoing embodiments relate to a detection set comprising a hologram applied to, for example, a hologram recording optical phase information in space computed in advance by a computer, a detection device that acquires spatial information obtained from the optical phase information, and a method for determining authenticity of the hologram. In addition, the foregoing embodiments relate to a detection set comprising a hologram, a detection device, and a method for verifying authenticity of a hologram which make it easy to acquire reconstructed information from conventional holograms and computer-generated holograms by combination of a light source and a photo-sensitive sensor and acquire three-dimensional spatial distribution information of the reconstructed information. Specifically, according to the foregoing embodiments, it is easy to acquire the three-dimensional spatial distribution information of the reconstructed information from the holograms.

The terms "part", "element", "pixel", "segment", "unit", "printed matter", and "article" used in the present disclosure denote physical existence. The physical existence can refer to a substantial form or a spatial form surrounded by substances. The physical existence can be a structure. The structure can have a specific function. A combination of structures having specific functions can produce synergistic effects by a combination of the functions of the structures.

Claim 1:
A detection device (<NUM>) comprising:
an image sensor (<NUM>, 5a) capable of measuring light intensity; and
a point light source (<NUM>), wherein
the image sensor comprises
a two-dimensional image sensor with a pixel formed from a double-gate transistor photosensor (<NUM>) and is adapted to detect the information reconstructed by a hologram (<NUM>),
the two-dimensional image sensor has on a light-transmissive substrate (<NUM>), on which the pixel is formed from a double-gate thin film transistor photosensor with a light-transmissive gate electrode (<NUM>) and a non-light-transmissive gate electrode (<NUM>),
the pixel is configured such that the light-transmissive gate electrode (<NUM>) is arranged on a front surface (<NUM>) of the image sensor, and an insulating film (<NUM>, <NUM>),
a semiconductor film (<NUM>), an insulating film (<NUM>), and the non-light-transmissive gate electrode (<NUM>) are arranged in this order from a front surface of the image sensor to the light-transmissive substrate (<NUM>),
and two or more of the two-dimensional image sensor are laminated, forming the image sensor (<NUM>, 5a).