JP2002278433A - Hologram assemblage and program for setting computer to execute computer hologram designing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form holograms which make it possible to obtain good reconstructed images and makes authenticity decision easy and sure by diffracting a plurality of diffracted light from one hologram block without lowering the density of the diffracted light constituting the reconstructed images. SOLUTION: The light quantity of the diffracted light relating to each of the plural images, the sizes of the divided holograms, the orders of diffraction, etc., are set and the phase distributions corresponding to the grating fringes of the diffraction gratings are calculated relating to the information on such diffracted light arrangement, by which the data of the many-valued two-dimensional phase type computer holograms is obtained and the grooves of the optical depths corresponding to the calculated phase values are formed as phase modulation plates on a hologram recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a program for causing a computer to execute a hologram assembly and a computer-generated hologram design method, and more particularly to a program for attaching or embedding a card, a product package, a bill, a document, etc., to a forged product. The present invention relates to a design of a computer generated hologram for use in authenticity judgment.

[0002]

2. Description of the Related Art A conventional hologram is designed such that the inside of a pattern such as a character or a figure to be displayed is completely filled with a binary one-dimensional phase type diffraction grating (JP-A-6-33762).
No. 2 and US Pat. No. 5,032,003), when the angle of the diffraction grating is changed for each pattern and the angle of the hologram with respect to the light source or the observation point is changed, a plurality of reproduced images are obtained. Are switched to be displayed on the same plane.

FIG. 12 is a schematic diagram showing an embodiment in which the inside of a figure of a character A is divided into several blocks, and the blocks are filled with the same binary one-dimensional phase type diffraction grating, and an enlarged view of the blocks. is there. Further, FIG.
FIG. 3 is a schematic diagram showing a cross-sectional structure of a binary one-dimensional phase-type diffraction grating in a block as viewed on a plane AB in a vertical direction. Here, the size of one block is about several hundred microns,
P is the pitch of the binary one-dimensional phase type diffraction grating 3 and is equal to 0.1.
W is about 5 to several microns, W is the pattern width of the binary one-dimensional phase type diffraction grating 3 and is about half the pitch, G
Is the depth of the binary one-dimensional phase type diffraction grating 3 and is generally about 0.1 to 1 micron.

FIG. 14 is a schematic diagram showing a state of diffraction by a binary one-dimensional phase type diffraction grating. The binary diffraction grating divides the phase of the illumination light into two parts, 0 and π, and forms a step having an optical depth corresponding to the phase. As shown in FIG. 14, the binary one-dimensional phase type diffraction grating 3 having such a simple structure returns diffracted light in the direction perpendicular to the direction of the diffraction grating with respect to the vertically incident light.

FIG. 15 is a schematic diagram showing a hologram designing method using a binary one-dimensional diffraction grating for realizing the display of A and the display of Y on the same plane. As shown in the figure on the left side of FIG. 15, the pattern A is first divided into blocks, and the inside of the blocks is filled with a binary one-dimensional phase type diffraction grating 3 in a checkered pattern. Next, as shown in the middle diagram of FIG. 15, the Y pattern is divided into blocks, and the inside of the blocks is filled with a checkered pattern in a direction different from the diffraction grating of the A pattern. In this example, the direction of the binary one-dimensional phase type diffraction grating 3 of the A pattern and the Y pattern is arranged to be orthogonal. At this time, in order to prevent the A-pattern and the Y-pattern from overlapping, as shown in the right side of FIG. 15, the checkered patterns are shifted from each other by one block in the vertical and horizontal directions.

FIG. 16 is a schematic diagram showing the directions and manner in which diffracted light can be seen when the hologram arranged as shown on the right side of FIG. In this example, since two types of patterns are arranged so that the diffraction gratings are orthogonal to each other, the directions in which the diffracted light can be seen differ by 90 degrees depending on the patterns as shown in FIG. That is, when the observation angle is changed by 90 degrees from the direction in which one pattern can be observed, the pattern is switched to another.

[0007]

In order to reproduce a plurality of images on the same plane as described above, a conventional diffraction grating combines binary one-dimensional phase type diffraction gratings in different directions as shown in FIG. A plurality of hologram blocks. When this method is used and two types of images A and B are reproduced, as shown in the diagram on the left side of FIG.
The hologram blocks can be arranged in a checkered pattern, and the corners of four hologram blocks of the same type can be in contact with each other. In this case, the diffracted lights constituting the reproduced image are densely arranged, and a smooth reproduced image can be obtained.

On the other hand, when reproducing three types of images A, B, and C, hologram blocks are arranged as shown in the middle diagram of FIG. 17. In this case, hologram blocks of the same type are Because they touch each other at two corners,
Compared to the two types of image configuration shown in the diagram on the left side of FIG. 17, the diffracted light forming the reproduced image has a sparser arrangement, and a striped dark portion occurs in the reproduced image. And 4 of A, B, C, D
When reproducing a type of image, hologram blocks are arranged as shown in the right side of FIG. 17, but in this case, the hologram blocks of the same type have no contact portions, and the diffracted light constituting the reproduced image Becomes a more sparse array, and the reproduced image deteriorates roughly. As described above, when three or more types of reproduced images are used, the same type of hologram / block arrangement is sparse, and there is a problem that the reproduced image is deteriorated.

An object of the present invention is to obtain a good reproduced image without diffracting a plurality of diffracted lights from one hologram block and reducing the density of the diffracted lights constituting the reproduced image.

[0010]

In order to achieve the above object, according to the present invention, the amount of diffracted light, the size of a divided hologram, the order of diffraction, etc. for each of a plurality of images are set, and these diffracted light beams are set. by calculating the phase distribution corresponding to the lattice stripes of the diffraction grating with respect to the arrangement information, to obtain data of the multi-level 2-dimensional phase type computer hologram, a phase modulation plate grooves optical depth corresponding to the calculated phase value Is formed.

That is, according to the present invention, diffracted light is emitted in a plurality of different directions according to the observation angle in response to light irradiation so that one of a plurality of images is reproduced in accordance with the observation angle. A hologram aggregate in which a plurality of holograms respectively emitted are recorded on a hologram recording medium in a large number of planes, and each of the plurality of holograms has a depth corresponding to a phase value for emitting a plurality of the diffracted lights. The hologram assembly provided with the phase modulation plate which has the groove | channel of this invention is provided.

According to the present invention, the hologram assembly is irradiated with light to generate a plurality of diffracted lights so that one of the plurality of images is reproduced according to the observation angle. A computer which divides each of the images to form a pixel array, records a multi-valued two-dimensional phase type computer generated hologram corresponding to each of the plurality of divided images on a hologram recording medium, and generates the hologram aggregate A program for causing a computer to execute a hologram design method, the program corresponding to each pixel array of the plurality of images on the hologram recording medium when dividing each of the plurality of images into a pixel array. A calculating step of calculating a phase value; and a phase modulation plate having a groove having a depth corresponding to each of the calculated phase values. And forming, the program for executing the computer generated hologram design method with the computer is provided.

Further, the multi-value two-dimensional phase-type computer generated hologram on the hologram recording medium is used for image adjustment for generating diffracted light in a direction different from an individual direction set for each of the plurality of images. Allocating a hologram for reference diffraction light to the hologram recording medium,
Referring to the diffracted light generated by the image adjustment reference diffracted light hologram and balancing at least one of the image reproduction diffracted lights corresponding to the plurality of images. Is a preferred embodiment of the present invention.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A program for causing a computer to execute a hologram assembly and a computer generated hologram design method of the present invention will be described below with reference to the drawings. Figure 1 is a schematic diagram showing an example of four images prepared for practicing the present invention. 4 types of images #
1, # 2, # 3, and # 4 are divided into 100 pixels in 10 rows and 10 columns. FIG. 2 shows a pixel array in which an image is divided into 100 pixels in 10 rows and 10 columns. The vertical and horizontal sizes (size of one pixel) of the individual holograms, which are the dividing elements, are, for example, a and b. In the above example, the number of divisions is 100 pixels, but the number of divisions can be any number.

Prepare a plurality of images as shown in FIG.
Divide the image into multiple pixels. This image may have been produced by photography or computer graphics. In the case of a photograph, the image is converted into a digital image by a scanner or the like, and the amount of light for each pixel is digitized. The program for causing a computer to execute the hologram assembly and the computer generated hologram design method of the present invention is to design a multi-valued two-dimensional phase type computer generated hologram capable of reproducing the amount of light of each of these pixels as diffracted light, Arrange.

A multi-valued two-dimensional phase type computer generated hologram is arranged in the same number of matrices as the pixel division of the image, and for each multi-valued two-dimensional phase type computer generated hologram, diffracted light corresponding to the light amount of a pixel located in the same matrix is generated. Diffract. For example, FIG.
Are designed so as to diffract diffracted light corresponding to the amount of light of the pixels located in each of the rows # 2 and # 2 of the images # 1 to # 4. I do.

Further, it is possible to set a desired diffraction angle for each diffraction angle of the diffracted light corresponding to the light quantity of the pixels located in the same matrix. FIG. 3 is a schematic diagram showing an example in which the respective diffraction angles of the diffracted light corresponding to the light amounts of the pixels located in the same matrix are set to desired diffraction angles. For example, as shown in FIG. 3, the diffraction angle of the diffracted light corresponding to the image of # 1 is set to (−10 degrees, 5 degrees). Similarly, the diffraction angle of # 2 is (−5 degrees, 5 degrees), and the diffraction angle of # 3 is (−10 degrees).
Degrees, -5 degrees) and # 4 diffraction angles are set to (-5 degrees, -5 degrees). In this way, a multi-value two-dimensional phase computer hologram corresponding to all pixels is designed, and a hologram aggregate of a multi-value two-dimensional phase computer hologram having a pixel array as shown in FIG. 2 is obtained.

[0018] FIG. 4 is a schematic diagram showing a reproduced image obtained at each angle of diffraction when the incident perpendicularly illumination light to the hologram assembly. When the illumination light is vertically incident on the hologram assembly, the image # 1 in FIG. 4 is reproduced when observed from a position (−10 degrees, 5 degrees) with respect to the incident light.
Similarly, the image of # 2 in FIG. 4 is observed from the position (-5 degrees, 5 degrees) with respect to the incident light, and the image of # 3 in FIG. 4 is observed from the position (-10 degrees, -5 degrees) with respect to the incident light. Is (-5 degrees, -5
When observed from the position (degree), the image # 4 in FIG. 4 is observed. As shown in FIG. 2, when the vertical and horizontal sizes of the individual holograms, which are the dividing elements, are a and b, the diffraction order and the diffraction angle of the diffracted light can be obtained by using the following Expressions 1 and 2. .

[0019]

(Equation 1)

[0020]

(Equation 2)

In the above equation (1), M is the diffraction angle order in the horizontal direction: M = ± 1, ± 2, ± 3,..., In the above equation (2), N is the diffraction angle order in the vertical direction: N = ± 1,
± 2, ± 3, which is .... Λ is the wavelength of the illumination light.

Here, a = b = 80 μm, λ = 0.5 μ
If the diffraction angle of the diffracted light corresponding to the image of # 1 is assumed to be (−10 degrees, 5 degrees) from Equations 1 and 2 when assuming m, the diffraction orders in the horizontal and vertical directions (M, N) ) To (-28
Next, 14th order) can be set. Similarly,
The diffraction orders (M, N) corresponding to the diffraction angles (−5 degrees, 5 degrees) of the image # 2 are (−14 orders, 14 orders), and the diffraction angles (−10 degrees, −5 degrees) of the image # 3. ) Corresponding to the diffraction order (M,
N) is set to (-28th order, -14th order), and the diffraction orders (M, N) corresponding to the diffraction angles (-5 degrees, -5 degrees) of the # 4 image are set to (-14th order, 14th order). do it.

As described above, the amount of diffracted light, the size of the divided hologram, and the order of diffraction are set, and the Fourier inverse transform is performed on the information on the arrangement of the diffracted light using a computer.
By calculating the phase distribution corresponding to the grating fringes of the diffraction grating, data of a multi-value two-dimensional phase type computer generated hologram is obtained. The calculated phase value takes an arbitrary value from 0 to 2π, and a computer generated hologram is formed by forming a groove having an optical depth corresponding to this phase value on a medium as a phase modulation plate.

The grooves of the computer generated hologram formed by the above method are transferred to a medium after the grooves are once formed on the substrate by applying a semiconductor manufacturing technique. Also, it is very difficult to etch any depth at any place. Therefore, quantization for rounding the phase to a specific value is required.

For example, by quantizing a multi-value two-dimensional phase computer hologram into four phases of 0, 1 / 2π, π and 3 / 2π, a four-value two-dimensional phase computer hologram can be created. . FIG. 5 shows that the phase is 0, 1/2.
FIG. 1 shows a hologram aggregate having a side of 80 μm quantized to four values of π, π, and 3 / 2π;
It is the figure which expanded a part of side 8 micrometers square. The hologram aggregate 1 in FIG. 5 is displayed in a gray scale having a luminance of 0 to 255. The phase 0 is the gray level 0, the phase 1 / 2π is the gray level 85, the phase π is the gray level 170, and the phase 3 / 2π corresponds to gray level 255.

FIG. 6 is a cross-sectional view of a line segment AB in an enlarged view of a part of one side of 8 μm square from the hologram assembly shown in FIG. As shown in FIG. 6, the cross section of the hologram has a phase of 0 phase where no phase modulation is performed, a 1 / 2π phase where 1 / 2π phase modulation is performed, a π stage where π phase modulation is performed, and a 3 / 2π phase. It has four optical depths corresponding to the quaternary phase of 3 / 2π for performing the modulation. In addition, regarding the calculation algorithm of the computer generated hologram,
Oplus E, 96, have been disclosed in, November p83.

For example, as shown in FIG. 3, when four diffracted lights are diffracted from one hologram aggregate 1 as shown in FIG. become. For example, when the sum of diffraction energies is 100, # 1, # 2, #
Even if the design light amounts of the reproduced images # 3 and # 4 are 100, respectively, the actual light amounts are 25 respectively. Also, # 1, #
The design light amounts of the reproduced images # 2, # 3, and # 4 are 0,
In the case of 0, 0, and 10, the actual diffraction energies are 0, 0, 0, and 100, respectively. For this reason, the amount of light as designed is not reproduced, and an unclear reproduced image may be generated. Thus, as shown in FIG. 3, the reference diffracted light for image adjustment is diffracted at a position different from the image reproduction angle to balance the total amount of light. At this time, the relative light amount R of the reference diffraction light for image adjustment is calculated using the following equation (3).

[0028]

(Equation 3)

In the above equation (3), d is the number of diffracted lights for image reproduction, and D _i is a light quantity design value of the individual image diffracted lights standardized with the maximum value being 1. Although the number of reference diffracted lights for image adjustment is one in the examples of FIGS. 3 and 4, for example, a plurality of reference diffracted lights may be provided. In the case of a plurality, the relative light amount R may be designed so as to be shared by the plurality. Diffraction angle of the image adjustment reference diffracted light is set to a position away from the image reproducing diffracted light, so as not to interfere with the image reproduced at the time of image observation. Further, the calculation of the diffraction angle is performed by the equations (1) and (2) as described above, and the light amount, the hologram size, and the diffraction order of the reference diffraction light for image adjustment and the diffraction light for image reproduction are set. By performing a Fourier inverse transform using a computer and calculating a phase distribution corresponding to the lattice fringes of the diffraction grating, a multivalued two-dimensional phase type computer-generated hologram capable of clearly reproducing a reproduced image can be designed.

Further, the multi-level two-dimensional phase type computer-generated hologram of the present invention and the conventional type two-dimensional one-dimensional phase type diffraction grating are mixed and allocated on the same plane, so that the visibility and design of the reproduced hologram image are improved. Can be increased. FIG.
FIG. 1 is a schematic diagram showing an example in which a conventional binary one-dimensional phase type diffraction grating is mixed around a multilevel two-dimensional phase type computer generated hologram of the present invention. FIG. 8 is a schematic diagram showing an example of a reconstructed image of a conventional binary one-dimensional phase type diffraction grating mixed around a multi-level two-dimensional phase type computer generated hologram of the present invention. By changing the angle, the reproduced image in FIG.
It can be changed as shown in FIG. 8, and the design of the hologram reproduced image can be improved. In FIG. 7, the two-dimensional one-dimensional phase type diffraction grating 3 is arranged so as to surround the periphery of the multi-valued two-dimensional phase type computer generated hologram 2, but these arrangement positions can be set to arbitrary positions. It is.

The hologram is affixed to a gift certificate, a cash voucher, a card, or the like, and is used for authenticity determination thereof. A general authentication method is a method of irradiating a hologram with illumination light and recognizing a reproduced image with the naked eye. But,
If the person performing the authenticity determination has never seen the true hologram reproduced image, it may be difficult to determine the authenticity. In that case,
Safer authentication can be performed by mechanically recognizing the hologram with an optical hologram reader and outputting the result of the authentication by the machine.

Therefore, it is preferable that the multi-value two-dimensional phase type computer generated hologram 2 according to the present invention is designed so as to be compatible with either the naked eye or machine recognition by a hologram reader. FIG. 9 is a schematic diagram illustrating an example in which one image # 5 for reader recognition is further added to the four images # 1 to # 4 illustrated in FIG. In FIG. 9, the number of reader recognition images is one, but a plurality of images can be prepared in practice.

The reader recognition image # 5 is set to diffract a uniform light amount. Therefore, the hologram assembly is divided into the hologram array as shown in FIG. 2 1
, The same amount of diffracted light is returned even if any of the constituent holograms is irradiated with the illuminating light, which facilitates recognition by a hologram reader shown in FIG. FIG.
FIG. 10 is a schematic diagram showing an example of setting a diffraction angle when setting the reproduced image of FIG. 9 as a hologram. For example, the diffraction angle of the reader recognition image # 5 is set to (0 degree, -5 degrees).

FIG. 11 is a schematic diagram showing an example of a hologram reader. The hologram reader 4 includes an illumination unit 5, a diffracted light receiving unit 6, and a diffracted light recognition unit 7. The illumination unit 5 includes a coherent light irradiation unit such as a laser and an objective lens, and the diffracted light receiving unit 6 includes, for example, a phototransistor, a CMOS, a CC,
It is composed of a two-dimensional sensor such as D. Also,
The diffracted light recognizing means 7 is composed of means for comparing the light quantity and position information output from the light receiving means with the light quantity and the diffraction angle of the image design value for reader recognition, and judges the authenticity of the hologram. For example, in this hologram reader,
When authenticating the image by recognizing the reader recognition image # 5,
The illuminating means and the diffracted light receiving means are set so as to have a suitable positional relationship with respect to the diffraction angle (0 degree, -5 degrees) of the reader recognition image # 5. Should be returned.

[0035]

As described above, according to the present invention,
By setting the amount of diffracted light, the size of the divided hologram, the diffraction order, and the like for each of the plurality of images, and calculating the phase distribution corresponding to the lattice fringes of the diffraction grating with respect to these pieces of diffracted light arrangement information, the multi-value 2 is obtained. Since the data of the hologram is obtained and a groove having an optical depth corresponding to the calculated phase value is formed on the hologram recording medium as a phase modulation plate, a plurality of diffracted lights can be obtained from one hologram block. A good reproduced image can be obtained without lowering the density of the diffracted light that diffracts and forms the reproduced image.

As a result, according to the present invention, it is possible to form a hologram in which the authenticity can be easily and reliably determined.
If formed on a D card, a product package, a license, or the like, it becomes possible to prevent forgery of these cards and the like and to use them as a part of a product design.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of four types of images prepared when executing the present invention.

FIG. 2 is a pixel array in which an image is divided into 100 pixels in 10 rows and 10 columns.

FIG. 3 is a schematic diagram illustrating an example in which each diffraction angle of diffracted light corresponding to the light amount of a pixel located in the same matrix is set to a desired diffraction angle.

FIG. 4 is a schematic diagram showing reproduced images obtained at respective diffraction angles when illumination light is vertically incident on a hologram assembly.

FIG. 5 is a diagram showing a hologram aggregate having a side of 80 μm quantized into four values of 0, 1 / 2π, π, and 3 / 2π, and a diagram enlarging a part of a side of 8 μm from the hologram aggregate; It is.

6 is a cross-sectional view of a line segment AB in an enlarged view of a part of a square having a side of 8 μm from the hologram assembly shown in FIG. 5;

FIG. 7 is a schematic diagram showing an example in which a conventional binary one-dimensional phase type diffraction grating is mixed around a multi-level two-dimensional phase type computer generated hologram of the present invention.

FIG. 8 is a schematic diagram showing an example of a reconstructed image obtained by mixing a conventional binary one-dimensional phase type diffraction grating around a multi-level two-dimensional phase type computer generated hologram of the present invention.

9 is a schematic diagram showing an example in which one image # 5 for reader recognition is further added to the four reproduced images # 1 to # 4 shown in FIG.

10 is a schematic diagram showing an example of setting a diffraction angle when setting the reproduced image of FIG. 9 in a hologram.

FIG. 11 is a schematic diagram illustrating an example of a hologram reader.

FIG. 12 is a schematic diagram showing an embodiment in which the inside of the figure of the character A is divided into several blocks and the blocks are filled with the same binary one-dimensional phase type diffraction grating, and an enlarged view of the blocks.

FIG. 13 is a schematic diagram showing a cross-sectional structure of the binary one-dimensional phase type diffraction grating in one block shown in FIG. 12 as viewed on the AB plane in the vertical direction.

FIG. 14 is a schematic diagram showing a state of diffraction by a binary one-dimensional phase type diffraction grating.

FIG. 15 is a schematic diagram showing a hologram design method using a binary one-dimensional diffraction grating that realizes the display of A and the display of Y on the same plane.

FIG. 16 is a schematic diagram showing the directions and manner in which diffracted light can be seen when illuminating light is applied to a hologram arranged as shown in the right side of FIG.

FIG. 17 is a schematic diagram showing an arrangement of a plurality of hologram blocks in which binary one-dimensional phase type diffraction gratings are combined in different directions.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 hologram aggregate 2 multi-level two-dimensional phase computer hologram 3 two-dimensional one-dimensional phase diffraction grating 4 hologram reader 5 illumination means 6 diffracted light receiving means 7 diffracted light recognition means

Claims (3)

[Claims] 1. One of a plurality of images according to an observation angle.
A hologram aggregate in which a plurality of holograms each emitting diffracted light in a plurality of different directions corresponding to the observation angle in response to light irradiation so as to reproduce one hologram is recorded on a hologram recording medium in a large number of planes. A hologram assembly, wherein each of the plurality of holograms includes a phase modulation plate having a groove having a depth corresponding to a phase value for emitting the plurality of diffracted lights. 2. A method according to claim 1, wherein the hologram assembly is irradiated with light to generate a plurality of diffracted light beams, so that one of the plurality of images is reproduced according to an observation angle. A computer-generated hologram design method for recording a multi-valued two-dimensional phase-type computer-generated hologram corresponding to each of the plurality of divided images on a hologram recording medium and generating the hologram aggregate is performed by a computer. A program for executing, when dividing each of the plurality of images into a pixel array, calculating a phase value corresponding to each pixel array of the plurality of images on the hologram recording medium. Forming a phase modulation plate having a groove having a depth corresponding to each of the calculated phase values on the hologram recording medium. A program for executing a computer hologram design method on a computer having. 3. An image adjustment apparatus according to claim 1, wherein said multi-valued two-dimensional phase-type computer generated hologram on said hologram recording medium generates diffracted light in a direction different from an individual direction set for each of said plurality of images. Allocating a reference diffracted light hologram to the hologram recording medium; and referring to the diffracted light generated by the image adjustment reference diffracted light hologram, among the image reproducing diffracted lights corresponding to the plurality of images. A program for causing a computer to execute the computer generated hologram design method according to claim 2, further comprising the step of: balancing at least one of the amounts of light.