JP2011022389A - Diffraction structure display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffraction structure display device which can perform black-and-white inversion display according to a viewing direction in an usual observation state, can reproduce authenticity determination information by irradiation with laser beams and thereby a higher forgery prevention effect can be attained. <P>SOLUTION: In the diffraction structure display device, a first pattern area and a second pattern area are arranged in parallel with each other. The first pattern area is formed of a hologram 14 in which a first image 12 is arranged at a remote position in one direction from the center of a specific direction passing through the center O on an image surface 11 and the phase information of a Fourier transform image 13 of an original image is recorded as a depth after converting a phase datum to four or more values. The second pattern area is formed of a hologram 24 in which a second image 22 is arranged at a remote position in the other direction from the center of a specific direction passing through the center O on an image surface 21 and the phase information of a Fourier transform image 23 of the original image is recorded as a depth after converting the phase datum to four or more values. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a diffractive structure display, and more particularly to a diffractive structure display in which a black-and-white display pattern can be reversed depending on a viewing direction in a normal observation state and authentication information is reproduced when irradiated with laser light. .

  In many cases, a diffraction grating or a hologram is applied to a card such as a deposit / save card or a credit card in order to guarantee the authenticity thereof. In addition, diffraction gratings and holograms are often applied to expensive products or cases where counterfeit products are easily available, in order to guarantee their authenticity.

  The reason why diffraction gratings and holograms are applied to articles in various fields other than the above examples is because holograms and the like have difficulty in manufacturing or copying, and in appearance they are interference colors. It is easy to catch the eye and is excellent in design, and in some cases, it has the merit that it can be destroyed when trying to peel off, and it can be made a structure that can not be diverted elsewhere Because.

As such a hologram, Patent Document 1 proposes a hologram (CGH) in which phase information of a Fourier transform image of an original image is multivalued and recorded as a depth. A hologram (CGH) in which the phase information of the Fourier transform image is multi-valued and recorded as a depth is projected and reproduced on a screen surface or the like when a laser beam is applied. As shown in FIG. 10, the hologram (CGH) is obtained by sequentially performing the following steps (1) to (7).
(1) First, an original image is formed. The original image may be an arbitrarily determined image, and may be any of letters, numbers, figures or symbols, paintings, animations, photographs, and the like.
(2) Next, a Fourier transform image of the original image is created by subjecting the original image to Fourier transform processing from the original image using a computer.
(3) Amplitude = 1.
(4) Perform inverse Fourier transform.
(5) The amplitude is set to the original amplitude (the phase is left as it is).
Thereafter, returning to (2), after repeating “Fourier transform → Fourier inverse transform”, it stops when it is determined that a Fourier transform image satisfying a predetermined condition has been obtained.
(6) After stopping, extract phase data.
(7) The phase data is multivalued to obtain depth information of a predetermined number of steps.

  Multi-leveling of phase data based on the original image can be, for example, binarization, quaternarization, octarization, or 16-value conversion.

  On the other hand, Patent Literature 2 proposes a plurality of regions having a plurality of linear convex portions or concave portions having the same direction and having a plurality of light scattering ability anisotropies having different directions. As shown in FIG. 11, in the character region 20a of the number “9” and the region 20b surrounding the number “9”, the directions of a large number of linear convex portions or concave portions arranged in parallel are orthogonal to each other. When viewed from the direction perpendicular to the direction of the convex portion or concave portion of each region, the region appears to be relatively white due to scattering of ambient light, and when viewed from the direction of the convex portion or concave portion, ambient light is present in that direction. Since it is not scattered, it looks relatively black. Therefore, in the case of FIG. 11, when viewed from the upper right to the lower left, the character region 20a appears white and the surrounding region 20b appears black. When viewed from the upper left or lower right direction orthogonal thereto, the black and white are reversed, and the character region 20a appears black and the surrounding region 20b appears white.

JP 2003-122233 A JP 2008-107472 A

  Both the hologram (CGH) of Patent Document 1 and the medium having the light scattering ability anisotropy of Patent Document 2 are used as a forgery-preventing recording body or display body. It was not always sufficient in terms of design, decoration, and visual effects on the body. On the other hand, in the case of the display body of Patent Document 2, authentication information cannot be recorded as hidden information.

  The present invention has been made in view of such a situation of the prior art, and its purpose is to enable black-and-white reversal display depending on the viewing direction in a normal observation state, and to authenticate authentication information by irradiating laser light. An object of the present invention is to provide a diffractive structure display that can be reproduced and can achieve a higher anti-counterfeit effect.

  The diffractive structure display of the present invention that achieves the above object is a Fourier transform image of an original image in which a first image is arranged at a position deviating in one direction from the center in a specific direction passing through the center on the image plane. A first pattern area consisting of a hologram in which phase information is recorded as multi-valued phase data of four or more values as a depth, and a position deviating from the center in a specific direction passing through the center on the image plane in the other direction The phase information of the Fourier transform image of the original image in which the second image is arranged on the phase data is converted into a multi-level phase data of four values or more and recorded as a depth to form a second pattern region made of a hologram. It is characterized by being arranged.

  In this case, the first image and the second image are in a range of ± 45 ° across a specific direction passing through the center of the image plane, and the maximum value 2 of the image plane in the specific direction from the center is 2 It is desirable that the hologram of the first pattern area and the hologram of the second pattern area are recorded within a range of a half.

  Further, a display area composed of another diffraction grating, a display area composed of another relief hologram, densely or separated from the periphery of the display body portion in which the first pattern area and the second pattern area are arranged in parallel. At least one of them may be arranged.

  According to the present invention, black-and-white reversal display can be performed depending on the viewing direction in a normal observation state, and authentication information can be reproduced by irradiating laser light, while having design properties, decorativeness, and visual effects, A high anti-counterfeit effect can be achieved.

It is a figure for demonstrating the hologram which multi-values the phase information of the Fourier-transform image in the case of using a point light source as an original image, and records it as depth. It is a figure which shows one example of the hologram used for the diffraction structure display body of this invention. It is a figure which shows the other example of the hologram used for the diffraction structure display body of this invention. It is a figure for demonstrating the diffraction structure display body by this invention according to preparation order. It is a figure for showing arrangement of one example of a diffraction structure display object by the present invention. It is a figure for demonstrating that the black-and-white reversal observation of the diffraction structure display body of FIG. 5 is possible. It is a figure which shows the arrangement | positioning for confirming the authenticity of the diffraction structure display body by this invention. It is a figure which shows the area | region which can arrange | position an image on an original image surface. It is a figure which shows the card | curd comprised by arrange | positioning the display area which consists of another diffraction grating and another relief hologram in the diffraction structure display body by this invention. It is a figure which shows the preparation procedure of the hologram which multi-valued the phase information of the Fourier-transform image of a well-known original image, and was recorded as depth. It is a figure which shows the display body which consists of a well-known area | region with several light scattering ability anisotropy, and black and white looks reversed.

  Hereinafter, examples of the diffractive structure display of the present invention will be described based on the description of the principle thereof.

  FIG. 1 is a diagram for explaining a hologram (CGH) in which phase information of a Fourier transform image in a case where a point light source is used as an original image and recorded as a depth, and using a Fourier transform action of a positive lens. I will explain.

  A plane passing through the front focal point F of the positive lens L at the focal length f and orthogonal to the optical axis is defined as the original image plane, and a plane passing through the rear focal point of the positive lens L and orthogonal to the optical axis is defined as the hologram surface H. The optical axis of the positive lens L is taken in the horizontal direction, the x-axis in the horizontal direction orthogonal to the optical axis on the original image plane, the y-axis in the vertical direction, the p-axis in the horizontal direction perpendicular to the optical axis on the hologram surface H, and the vertical Take q-axis in direction. When the point light source P is located at a position away from the optical axis (origin) on the y-axis on the original image plane in the negative direction, that is, as the original image, a position deviated from the center of the original image plane in the vertical direction. Consider a Fourier transform image of an image where the point light source P is located. The spherical wave emitted from the point light source P is converted into a plane wave by the positive lens L, and enters the hologram surface H as a plane wave traveling in a linear direction passing through the center of the point light source P and the positive lens L. 1A is a plan view, and FIG. 1B is a side view. The equiphase surface S of the light beam converted into a plane wave by the positive lens L is parallel to the hologram surface H when viewed from the plan view. Then, the light enters the hologram surface and enters the hologram surface H at an angle when viewed from a side view. Therefore, the equiphase position (intersection (line) between the equiphase surface S and the hologram surface H) of the Fourier transform image of the point light source P recorded on the hologram surface H is a parallel line extending in the horizontal direction (p direction). . As the equiphase position, for example, when the position of phase π and its odd multiple is the deepest position, and the position of 2π and its integral multiple is the highest position, the distribution of the highest position is the horizontal direction on the hologram surface H ( Equally spaced parallel lines (interference fringes) extending in the (p direction). The same applies when the point light source P is displaced in the positive direction from the origin on the y-axis.

  It can be understood from this examination that if the point light source P is located in a predetermined direction (y-axis direction in the above example) from the center on the original image plane, the isophase lines (interference fringes) of the Fourier transform image are obtained. Is a straight line extending in a direction orthogonal to the direction of deviation (p-axis direction in the above example).

  Although the original image is not usually a point light source P, it can be considered as a set of point light sources P. Therefore, the original image is arranged on both sides of the original image plane so as to be shifted from the center on the original image plane across a predetermined direction. The Fourier transform image of an image is formed by superimposing a number of equiphase lines parallel to a direction orthogonal to the predetermined direction and isophase lines extending at a small angle in the direction orthogonal to the predetermined direction.

  FIGS. 2A and 2B are diagrams showing one actual example, where FIG. 2A is an original image, and FIG. 2B is a diagram showing a Fourier transform image. The original image deviates vertically from the center of the original image plane (+ y direction). The character “D” is located at the position where the Fourier transform image of the original image is distributed so that the equiphase lines (interference fringes) B are substantially directed in the horizontal direction (p direction). I understand that there is.

  In this way, the Fourier transform image of the original image in which the original image is located at a position deviating from the center of the image plane is a direction (specific direction) in which the equiphase lines (interference fringes) B are orthogonal to the predetermined. Alternatively, it extends at a small angle with respect to the orthogonal direction.

  Such a phase image recording medium (hologram (CGH)) is composed of a large number of curved convex portions or concave portions B extending in parallel in a specific direction, and can be said in the embodiment of FIG. For example, light incident from the front surface of the hologram (CGH) has a light scattering ability anisotropy that scatters in a direction orthogonal to the curved convex portion or concave portion B, that is, in the ± q direction (Patent Document 2). ).

  However, as will be described later, when recording the phase on the hologram (CGH), the multilevel binarization of the phase data is not binarized, but more than four values, eight values, sixteen values, etc. Then, the recorded equiphase lines (interference fringes) B are blazed, and in the case of the embodiment of FIG. 2, most of the ambient light is scattered in the + q direction, which is the bias direction of the original image “D”. Become a characteristic.

  FIG. 3 is a diagram showing another example, where (a) is an original image, (b) is a diagram showing a Fourier transform image, and the original image is vertically downward (−y direction) from the center of the original image plane. The character “GENUINE” is located at a deviated position, and the Fourier transform image of the original image has an equiphase line (interference fringe) B substantially in the horizontal direction (p direction) as in the case of FIG. It can be seen that they are distributed so as to face.

  In this way, the Fourier transform image of the original image in which the original image is located at a position deviating from the center of the image plane is a direction (specific direction) in which the equiphase lines (interference fringes) B are orthogonal to the predetermined. Alternatively, it extends at a small angle with respect to the orthogonal direction.

  Such a phase image recording medium (hologram (CGH)) is composed of a large number of curved convex portions or concave portions B extending in parallel in a specific direction. In the embodiment of FIG. Light incident from the front surface of (CGH) has light scattering ability anisotropy that scatters in a direction orthogonal to the curved convex portion or concave portion B, that is, in the ± q direction (Patent Document 2). The same applies to the embodiment of FIG.

  However, as will be described later, when recording the phase on the hologram (CGH), the multilevel binarization of the phase data is not binarized, but more than four values, eight values, sixteen values, etc. Then, the recorded equiphase lines (interference fringes) B are blazed, and in the case of the embodiment of FIG. 2, most of the ambient light is scattered in the + q direction, which is the bias direction of the original image “D”. In the case of the embodiment of FIG. 3, the characteristic is that most of the ambient light is scattered in the −q direction, which is the bias direction of the original image “GENUINE”.

  In the present invention, the phase information of the Fourier transform image of the original image in which the original image is located at a position deviating from the center of the image plane in such a manner is interfered by converting the phase data into four or more values. Two holograms (CGH) recorded with blazed fringes are used.

  Hereinafter, the diffractive structure display according to the present invention will be described in the order of its production. As shown in FIGS. 4 (a) / (1) and (b) / (1), original images as shown in FIGS. 2 (a) and 3 (a) are prepared. In other words, the original image 12 shown in FIGS. 4A and 4A has the character “D” located at a position that is out of the center O of the original image plane 11 in the vertical upward direction (+ y direction). Yes, in the original image 22 of FIGS. 4B / 4, the vertically inverted character “GENUINE” is located at a position deviating vertically from the center O of the original image plane 21 (−y direction). Is.

Fourier transform images 13 and 23 obtained by performing Fourier transform on the original image surfaces 11 and 21 in the same manner as in (1) to (6) of Patent Document 1, respectively, are shown in FIGS. (2) has phase data as shown, and the curve schematically shows an equiphase line, but the original images 12 and 22 are respectively shown in FIGS. 2 (b) and 3 (b). Such isophase lines B are distributed. And each Fourier-transform image 13 and 23 is performed like (7) of patent document 1, respectively, and a phase as shown to FIG. 4 (a) / (3) and (b) / (3), respectively is shown. Holograms (CGH) 14 and 24 in which the data is converted into multi-values having four or more values are obtained.

  4 (a) / (4) and (b) / (4) are schematic sectional views taken along a straight line AA ′ parallel to the q-axis of the holograms (CGH) 14 and 24, respectively. The cross-sectional shape of the equiphase line B indicating the phase distribution of the holograms (CGH) 14 and 24 is a sawtooth cross-section of each convex portion, and is transmitted through the holograms (CGH) 14 and 24. Whether used in a mold, or in a reflective mold with a reflective coating applied to the relief surface, etc., the slope of the serrated cross-sectional surface acts as a refracting surface or reflecting surface, and diffracted light in the same way as a blazed surface of a diffraction grating. Alternatively, the scattered light is concentrated in a specific direction, and the hologram (CGH) 14 shown in FIGS. 4 (a) / (3) and (4) has + q on the original image 12 side. Scatters with bias in the direction. On the other hand, the holograms (CGH) 24 shown in FIGS. 4B / 4, 3 and 4 scatter light that is incident from the front side in the -q direction, which is the original image 22 side.

  Therefore, in the present invention, for example, as shown in FIG. 5, two regions of the display body are arranged in parallel, inside and outside the letter “A” in FIG. 5, in this embodiment, inside the letter “A”. A hologram (CGH) 14 in which the phase data of FIG. 4A / (3) is converted into multi-values of four or more values is arranged in the region 31, and FIG. 4B / (3) is placed in the outer region 32 of the character “A”. The display body 1 is configured by arranging a hologram (CGH) 24 in which the phase data of 4) is converted into four or more values.

  When such a display body 1 is observed from diagonally below in FIG. 5, the hologram (CGH) 14 in the inner region 31 of the letter “A” mainly tilts ambient light incident from the front side of the display body 1. Since it scatters upward, it does not reach the observer's eyes obliquely below and looks relatively dark, and the hologram (CGH) 24 in the outer region 32 of the letter “A” is ambient light incident from the front side of the display body 1. Is scattered obliquely downward, so that it reaches the eyes of the observer below and appears relatively bright. Therefore, when the display body 1 is observed obliquely from below, the character “A” can be observed as a black character on a relatively white background as shown in FIG.

  This time, when the display body 1 is rotated 180 ° and viewed upside down, the hologram (CGH) 14 in the inner region 31 of the letter “A” is mainly obliquely below the ambient light incident from the front side of the display body 1. Therefore, the hologram (CGH) 24 in the outer region 32 of the letter “A” is mainly oblique to ambient light incident from the front side of the display body 1. Since it scatters upward, it does not reach the eyes of the observer below and appears relatively dark. Therefore, when the display body 1 is observed obliquely from below (or when observed from obliquely above in FIG. 5), as shown in FIG. 6B, the letter “A” (upside down “A”) is relatively black. It can be observed as white letters on the background.

  Therefore, the display body 1 of the present invention is used when the observer observes with the naked eye, when the display body 1 is observed in a normal state, and when the display body 1 is rotated 180 ° and viewed upside down. The black and white of the pattern determined by the relative arrangement of the two holograms (CGH) 14 and 24 appears to be reversed, and the design, decoration, and visual effects are high.

Then, the authenticity proof method will be described taking the card 10 using such a display body 1 as an example. As shown in FIG. 7, the diffractive structure display body 1 for authenticity proof according to the present invention has a laser light source 41. Is used to irradiate laser light 42, which is coherent light having a predetermined wavelength, from directly above. The beam diameter of the laser beam 42 may be smaller than the regions 31 and 32 of the diffractive structure display 1, but the size of both the regions 31 and 32 is preferable. By this irradiation, the original images “D” and “GENUINE” recorded as depth information information previously multi-valued in the hologram (CGH) 14 in the region 31 and the hologram (CGH) 24 in the region 32 are diffracted light 44a. , 44b. By comparing the reconstructed image with a reference image prepared in advance and determining whether they are the same or different, the authenticity can be confirmed.

  Therefore, assuming a certain face 43 away from the display body 1 to some extent, for example, the recorded image “D” of the hologram (CGH) 14 in the area 43a on the right side and the hologram (CGH) in the area 43b on the left side. ) Since 24 recorded images “GENUINE” can be observed, the surface 43 is an upper plate of the box, and includes a laser light source 41 and a fixing base (not shown) of the diffraction structure display 1 for authenticity verification. If the instrument is prepared and a transmissive screen is provided in each of the areas 43a and 43b on the upper plate of the box, it is possible to determine the reproduced image using this instrument. It is possible to easily confirm the authenticity of the diffractive structure display 1 for authenticity verification.

  In the description of FIGS. 2 and 3, images (characters) “D” and “GENUINE” recorded as holograms (CGH) 14 and 24 at positions deviated from the center of the image plane in the + y direction or −y direction of the y axis. However, it did not explain how much the image may spread in the direction orthogonal to the y-axis. The smaller the spread in the direction perpendicular to the y-axis, the more the phase of the equiphase line (interference fringe) B is directed in the direction perpendicular to the y-axis, and the scattering direction at the equiphase line (interference fringe) B Therefore, the black and white inversion of the region 31 of the hologram (CGH) 14 and the region 32 of the hologram (CGH) 24 can be remarkably observed, which is desirable.

  FIG. 8 shows an area in which an image can be arranged as a hatch area when the image actually deviates from the center O of the original image planes 11 and 21 in the + y direction. If an image to be recorded as a Fourier transform image is arranged in a range of ± 45 ° from the center O of the original image planes 11 and 12 with the y-axis in between, black and white inversion can be easily observed. Further, it is desirable to arrange within the range of 1/2 of the maximum value of the original image planes 11 and 12 in the + y direction from the center O. Exceeding the half of the maximum value in the + y direction from the center O is not preferable because the images (“D” and “GENUINE” in FIG. 7) reproduced from the holograms (CGH) 14 and 24 are distorted.

  By the way, in the diffraction structure display according to the present invention, the phase of the Fourier transform image of the original image in which the image is arranged at a position deviated in one direction from the center in the specific direction passing through the center on the image surface as described above. A hologram in which information is recorded as depth by multi-leveling four or more values of phase data, and an original is formed by arranging an image at a position deviating from the center in a specific direction passing through the center on the image plane in the other direction. As shown in FIG. 9, the phase information of the Fourier transform image of the image is not limited to the display body 1 configured in parallel with the hologram in which the phase data is multivalued into four or more values and recorded as the depth. The display area 3 consisting of the above diffraction grating and the display area 2 consisting of another relief hologram are arranged densely or apart from each other around the display body 1, thereby forming a card 10 having a complicated and higher design effect display body. You can do it .

  The principle and examples of the diffractive structure display of the present invention have been described above. However, the present invention is not limited to these examples, and various modifications can be made.

  According to the present invention, black-and-white reversal display can be performed depending on the viewing direction in a normal observation state, and authentication information can be reproduced by irradiating laser light, while having design properties, decorativeness, and visual effects, A high anti-counterfeit effect can be achieved.

f ... Focal length L ... Positive lens F ... Front focus H ... Hologram surface P ... Point light source S ... Equiphase surface B ... Equiphase line (interference fringe, convex or concave)
O ... center of original image plane 1 ... display body 10 ... card 11, 21 ... original image plane 12, 22 ... original image 13, 23 ... Fourier transform image 14, 24 ... hologram (CGH)
20a ... character region 20b ... region 31 surrounding character region ... inner region 32 ... outer region 41 ... laser light source 42 ... laser light 43 ... surface 43a ... right region 43b ... left region 44a, 44b ... diffracted light

Claims (3)

The phase information of the Fourier transform image of the original image in which the first image is arranged at a position deviating in one direction from the center of the specific direction passing through the center on the image plane is converted into multi-values of four or more phase data. The first pattern area consisting of the hologram recorded as depth and the Fourier of the original image in which the second image is arranged at a position deviating from the center in the specific direction passing through the center on the image plane in the other direction A diffractive structure display body characterized in that phase information of a converted image is arranged in parallel with a second pattern region formed of a hologram in which phase data is multivalued into four or more values and recorded as a depth. . The first image and the second image are in a range of ± 45 ° across a specific direction passing through the center of the image plane, and are half of the maximum value of the image plane in the specific direction from the center. 2. The diffractive structure display body according to claim 1, wherein the hologram of the first pattern area and the hologram of the second pattern area are recorded within the range of the first pattern area. At least one of a display area consisting of another diffraction grating and a display area consisting of another relief hologram densely or apart from each other around the display body portion in which the first pattern area and the second pattern area are arranged in parallel The diffractive structure display body according to claim 1, wherein the diffractive structure display body is disposed.

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