JP7172023B2 - Light modulation device and authenticity determination device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical modulation element that reproduces an optical image by modulating the phase of incident light, and an authenticity determination device including the optical modulation element.

Various types of light modulation elements have been proposed as light modulation elements such as holograms capable of reproducing an original image.

For example, US Pat. Such holograms diffract light over the entire visible wavelength band to reconstruct a light image. Therefore, when these holograms are observed with white light incident thereon, as shown in FIG. Such a hologram reproduces the same optical image as the optical image obtained when white light is incident even when light in a specific wavelength range is incident.

JP-A-8-353694 Japanese Patent Application Laid-Open No. 2003-205316

However, in order to identify (for example, determine authenticity) the light modulation element and to improve the design of the light modulation element, it is desired to realize the light modulation element having the following characteristics. In other words, the intended light image can be obtained only when light in a specific wavelength range is filtered, or when light in a specific wavelength range is filtered out of the reproduction light, or when image analysis of the reproduction light is performed. is obtained, and in other cases (for example, when light including light of various wavelength ranges such as white light is incident), an optical image different from the intended optical image is obtained.

The present invention has been made in view of the above circumstances. To provide an optical modulation element capable of obtaining an intended optical image only when image analysis is performed, and obtaining an optical image different from the intended optical image in other cases.

The light modulation element according to this embodiment includes an element element that reproduces an optical image by modulating the phase of incident light,
The element element has an uneven surface with three or more different heights,
A first optical image is obtained by light in the first wavelength range, and a second optical image is obtained in a position overlapping the first optical image by light in a second wavelength range different from the first wavelength range.

In this case, the elementary elements may be configured as Fourier transform holograms.

Further, the element element reproduces the first optical image with light in the first wavelength band, and reproduces the second optical image point-symmetrically with the first optical image with light in the second wavelength band. good too.

Alternatively, a first element element that reproduces the first optical image with light in the first wavelength band and a second element element that reproduces the second optical image with light in the second wavelength band may be provided. good.

In this case, the first element element and the second element element may be arranged side by side on the same plane.

Also, the first wavelength range and the second wavelength range may be from 380 nm to 780 nm.

Further, the authenticity determination device of the present embodiment is
the light modulation element described above;
A light source device that emits light containing one of the light in the first wavelength range and the light in the second wavelength range and excluding the other, and the other containing the light in the first wavelength range and the light in the second wavelength range and at least one of a filter that transmits light that does not contain and an image analysis device that captures light that contains one of the light in the first wavelength band and the light in the second wavelength band and does not contain the other.

According to the present disclosure, only when light in a specific wavelength range is filtered, when light in a specific wavelength range is filtered out of the reproduction light, or when image analysis of the reproduction light is performed It is possible to provide an optical modulation element that obtains an intended optical image, and in other cases obtains an optical image different from the intended optical image.

FIG. 1 is a schematic plan view showing a typical example of an optical modulator holder. FIG. 2 is a cross-sectional view taken along line II-II of FIG. FIG. 3 is a conceptual diagram showing a planar structure of an optical modulation element. FIG. 4 is a cross-sectional view of an element element showing an outline of an example of a stepped structure of an uneven surface. FIG. 5 is a cross-sectional view of an element element schematically showing another example of the stepped structure of the uneven surface. 6 is a diagram for explaining a light image obtained when white light is incident on the light modulation element shown in FIG. 3. FIG. FIG. 7 is a diagram for explaining a light image obtained in the authenticity determination device including the light modulation element shown in FIG. FIG. 8 is a graph showing an example of the relationship between the wavelength distribution of 1st-order diffracted light and -1st-order diffracted light and diffraction efficiency in each element element. 9A is a diagram showing an example of a first optical image obtained by light in the first wavelength band in the light modulation element shown in FIGS. 6 and 7. FIG. 9B is a diagram showing an example of a second optical image obtained by light in the second wavelength band in the light modulation element shown in FIGS. 6 and 7. FIG. 9C is a diagram showing an example of a third light image obtained by light in the third wavelength band in the light modulation element shown in FIGS. 6 and 7. FIG. FIG. 10 is a graph showing another example of the relationship between the wavelength distribution of 1st-order diffracted light and −1st-order diffracted light and diffraction efficiency in each element element. FIG. 11 is a graph showing still another example of the relationship between the wavelength distribution of the 1st-order diffracted light and -1st-order diffracted light and the diffraction efficiency in each element element. FIG. 12 is a graph showing still another example of the relationship between the wavelength distribution of the 1st-order diffracted light and -1st-order diffracted light and the diffraction efficiency in each element element. FIG. 13 is a graph showing still another example of the relationship between the wavelength distribution of the 1st-order diffracted light and -1st-order diffracted light and the diffraction efficiency in each element element. FIG. 14 is a conceptual diagram showing a planar structure of an optical modulation element according to a modification. 15A shows an example of a first optical image obtained by light in the first wavelength range and a third optical image obtained by light in the second wavelength range in the first element element constituting the light modulation element shown in FIG. 14. FIG. FIG. 4 is a diagram showing; 15B shows an example of a fourth light image obtained by light in the first wavelength range and a second light image obtained by light in the second wavelength range in the second element element constituting the light modulation element shown in FIG. 14; FIG. 4 is a diagram showing; FIG. 16 is a diagram for explaining a light image obtained when white light is incident on the light modulation element according to the comparative example. FIG. 17 is a graph showing an example of the relationship between the wavelength distribution of the 1st-order diffracted light and −1st-order diffracted light and the diffraction efficiency in each element element constituting the light modulation element shown in FIG.

Hereinafter, an optical modulation element and an authenticity determination device according to embodiments of the present disclosure will be described with reference to the drawings. In the drawings attached to this specification, for the convenience of illustration and ease of understanding, the scale and the ratio of vertical and horizontal dimensions are changed and exaggerated from those of the real thing.

In addition, terms such as "parallel", "perpendicular", "identical", length and angle values, etc. that specify shapes and geometric conditions and their degrees used in this specification are strictly It is interpreted to include the extent to which similar functions can be expected without being bound by any particular meaning.

The optical modulation elements of the following embodiments have element elements that reproduce an optical image by modulating the phase of incident light. The elemental elements are composed of diffraction gratings. Concretely, the element element is composed of a hologram structure, particularly a Fourier transform hologram. A Fourier transform hologram is a hologram produced by recording wavefront information of a Fourier transform image of an original image, and functions as a so-called Fourier transform lens. In particular, the phase modulation type Fourier transform hologram is a hologram with an uneven surface that is produced by recording the phase information of the Fourier transform image into multiple values and recording it as depth on the medium. is used to reproduce a light image of the original image from the reproduction light. This Fourier transform hologram, for example, is advantageous in that it can reproduce a desired optical image (that is, the original image) with high precision and that it can be produced relatively easily. However, the element elements of the light modulation element to which the present invention can be applied are not limited to Fourier transform holograms, and the present invention can be applied to light modulation elements having other structures such as holograms that reproduce optical images by other methods. can be applied.

In the following description, unless otherwise specified, it is assumed that the incident angle of incident light with respect to the light modulation element is 0° (that is, the angle along the normal direction of the incident surface of the light modulation element). Further, the specific values of the refractive index shown in this specification are based on light with a wavelength of 589.3 nm unless otherwise specified. In the following description, unless otherwise specified, the refractive index and uneven surface characteristic values shown for the light modulation element are based on the assumption that the light modulation element is used in an air environment with a refractive index of 1.0. is a value derived from

As shown in FIG. 6, the light modulator is a reflective light modulator intended for observation of diffracted light due to reflection on the light modulator, with the observer and the light source arranged on the same side with respect to the light modulator. and a transmissive light modulation element intended for observing diffracted light due to transmission of the light modulation element, in which the observer and the light source are arranged on different sides of the light modulation element. . As a reflective light modulation element, for example, in addition to a structure provided with an additional layer for reflecting reproduced light, such as the reflective layer 2 shown in FIG. There is a structure in which the uneven surface 1a of is exposed to the air and the reproduction light is reflected by utilizing the difference in refractive index between the hologram layer 1 made of UV curable resin or the like and the air. On the other hand, a transmissive optical modulation element is not provided with such a reflective layer. However, since the hologram layer 1 is formed with an uneven surface 1a and a desired optical image is reproduced by the diffraction phenomenon caused by the difference in the optical path length of the uneven surface 1a, the reflection-type light modulation element and the transmission-type light modulation element are common. As for the specific depth of unevenness of the uneven surface 1a, there is an optimum value for each of the transmissive optical modulation element and the reflective optical modulation element. In the following, unless otherwise specified, descriptions of only one of the reflective optical modulation element and the transmissive optical modulation element basically refer to the reflective optical modulation element and the transmissive optical modulation element. It is applicable to both devices.

In this specification, the concept of two or more light images having the same shape includes not only two or more light images having the same size and the same shape (overall shape), but also two or more light images having the same shape (overall shape). It also includes two or more optical images whose reproduced sizes are slightly different from each other due to the different constituent wavelengths of the images.

In this specification, the concept of two light images having a "point symmetry" relationship includes not only two light images having the same size and the same shape (overall shape), but also two light images having the same size. Also included are two optical images that are different from each other and have the same shape. That is, it does not matter whether two optical images having the same shape have the same size as long as the shape is the same and the reproduction position and the reproduction direction have point symmetry. Therefore, for example, two light images having a relationship of similarity to each other and having point symmetry in the reproduction position and direction of reproduction correspond to "two light images having a relationship of point symmetry with each other". . Therefore, if two or more optical images reproduced in different sizes due to different constituent wavelengths of the optical images have the same shape, and the reproduced position and orientation of the optical images are point symmetric, It corresponds to "two optical images having a point-symmetrical relationship with each other".

Hereinafter, the optical modulation element of this embodiment will be described in detail with reference to the drawings.

The light modulation element of the present embodiment is used when light in a specific wavelength range is filtered, or when light in a specific wavelength range is filtered out of the reproduced light, or image analysis of the reproduced light is performed. It is devised so that an intended optical image can be obtained only in certain cases, and an optical image different from the intended optical image can be obtained in other cases. Such an optical modulation element is excellent in identification (for example, authenticity determination) and designability.

First, the structure of the light modulation element 11 will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a schematic plan view showing a typical example of the light modulation element holder 10. FIG. FIG. 2 is a cross-sectional view taken along line II-II of FIG.

The light modulation element holder 10 shown in FIGS. 1 and 2 includes a hologram layer 1, a reflective layer 2 laminated on one surface of the hologram layer 1, and a substrate laminated on the other surface of the hologram layer 1. material 4; A reflective optical modulation element 11 is provided on a part of the optical modulation element holder 10 . In this light modulation element 11, one surface of the hologram layer 1 forms an uneven surface 1a, and the reflective layer 2 covering this uneven surface 1a also has an uneven shape. The uneven surface 1a of the light modulation element 11 has an uneven pattern corresponding to the Fourier transform image of the original image, and has an uneven depth corresponding to each pixel of the Fourier transform image. For example, a resin (for example, a UV curable resin or a thermoplastic resin) that constitutes the hologram layer 1 is formed on a substrate 4 (for example, PET: polyethylene terephthalate) by coating, and the resin that constitutes the hologram layer 1 is , UV curing treatment, heat pressure treatment, and uneven _shaping treatment in which the uneven surface of the original plate is pressed. , the light modulation element holder 10 shown in FIGS. 1 and 2 can be manufactured. Although illustration is omitted, other members such as an adhesive material, an adhesive, and/or a heat seal layer may be further formed on the reflective layer 2 .

When light or sunlight from a parallel light source composed of a point light source or a laser light source is incident on the light modulation element 11, a light image (that is, an original image) corresponding to the uneven pattern of the uneven surface 1a is reproduced. be. This type of light modulation element does not require a screen or the like for projecting an optical image, and reproduces an optical image particularly well when light from a specific light source such as a point light source or a parallel light source is incident. , design applications, security applications such as authenticity determination, and other applications with good convenience and a wide range of uses. The optical image that can be reproduced by such an optical modulation element is not particularly limited, and for example, characters, symbols, line drawings, pictures, patterns, combinations thereof, etc. can be used as the original image and the optical image that can be reproduced.

FIG. 3 is a conceptual diagram showing the planar structure of the light modulation element 11. As shown in FIG. The light modulation element 11 of this embodiment includes a plurality of element elements (also called “hologram cells”) 21 that are regularly arranged two-dimensionally. Each element element 21 has the uneven surface 1a described above, and has a planar size of several nanometers to several millimeters square (for example, 2 millimeters square), and modulates the phase of reproduction light to reproduce an optical image.

The uneven surface 1a has a multi-step shape and includes three or more steps of different heights. The number of steps of the uneven surface 1a is not particularly limited as long as it includes three or more steps of different heights. When reproducing an original image having a complicated composition with high definition, it is preferable that the uneven surface 1a includes four or more different heights.

4 and 5 are cross-sectional views of the element element 21 showing the outline of the stepped structure of the uneven surface 1a. FIG. 4 shows an uneven surface 1a with eight different heights, and FIG. 5 shows an uneven surface 1a with four different heights. Although FIG. 4 and FIG. 5 show the element elements 21 having the same stepped uneven surface 1a, the actual uneven surface 1a is stepped according to the reproduced optical image (that is, the original image). have a shape. The pitch of the uneven pattern of the uneven surface 1a (that is, the pixel pitch (see the symbol "P" shown in FIGS. 4 and 5)) is in the range of 0.1 μm to 80.0 μm from the viewpoint of accurately reproducing the optical image. It is preferably 1 μm or more, and usually preferably 1 μm or more.

FIG. 6 is a diagram for explaining a light image obtained when white light is made incident on the light modulation element 11 shown in FIG. In FIG. 6, reference numeral "151" indicates a white light source device. FIG. 7 is a diagram for explaining an optical image obtained when light in a specific wavelength range is made incident on the light modulation element in the authenticity determination device provided with the light modulation element shown in FIG. In FIG. 7, reference numeral "300" indicates an authenticity determination device, and reference numeral "251" indicates an authenticity determination light source device provided in the authentication device.

The authenticity determination device 300 shown in FIG. 7 includes an optical modulation element 11 and an authenticity determination light source device 251 . The authenticity determination light source device 251 emits light that includes one of light in a first wavelength range including the first wavelength and light in a second wavelength range including the second wavelength but does not include the other. Here, "including one but not including the other" also applies to the case where the luminous flux of one light is less than 10% and the other light is included. In the example shown in FIG. 7, the authenticity determination light source device 251 emits light that includes light in the first wavelength band and does not include light in the second wavelength band. Especially in the example shown in FIG. 7, since the authentication device 300 includes the light modulation element 11 having the diffraction efficiency characteristic shown in FIG. and emits light that does not include light in the second wavelength band and light in the third wavelength band that includes the third wavelength.

As shown in FIG. 7, the light modulation element 11 can obtain a clear optical image 200a of the character "OK" when the light from the light source device 251 for authenticity determination enters the authenticity determination device 300. FIG. On the other hand, when white light is incident on the light modulation element 11, an optical image 100 different from the optical image 200a is obtained as shown in FIG. The characteristics of the light modulation elements shown in FIGS. 6 and 7 will be described in more detail below with reference to FIGS. 8 to 9C.

FIG. 8 is a graph showing the wavelength distribution of 1st-order diffracted light and -1st-order diffracted light at the element element 21 constituting the light modulation element 11 for incident light in the wavelength range of 380 nm or more and 780 nm or less. In FIG. 8, the horizontal axis indicates the wavelength [unit: nm], and the vertical axis indicates the diffraction efficiency [unit: %]. The diffraction efficiency is expressed by dividing the radiant flux of light diffracted in a certain direction [unit: μW or μJ/cm ² ] by the radiant flux of light incident on each element element 21, and is the diffracted radiant flux in a certain direction. is represented by P, and the incident radiant flux is represented by P0, the diffraction efficiency η is a dimensionless number represented by "η=P/P0". In FIG. 8 and FIGS. 10 to 13 described later, the wavelength distribution of the 1st order diffracted light is indicated by "W1", and the wavelength distribution of the -1st order diffracted light is indicated by "W-1".

In FIG. 9A, light in the first wavelength band (specifically, light in the wavelength band including the first wavelength of 520 nm) is made incident on the light modulation element 11 composed of the element elements 21 having the diffraction efficiency characteristics shown in FIG. It shows a first optical image 200a obtained when In FIG. 9B, light in the second wavelength band (specifically, light in the wavelength band including the second wavelength of 665 nm) is applied to the optical modulation element 11 composed of the element elements 21 having the diffraction efficiency characteristics shown in FIG. A second optical image 200b obtained when the light is incident is shown. In FIG. 9C, light in the third wavelength band (specifically, light in the wavelength band including the third wavelength of 420 nm) is made incident on the light modulation element 11 composed of the element elements 21 having the diffraction efficiency characteristics shown in FIG. It shows a third optical image 200c obtained when

Of the light diffracted by the element element 21, the 1st-order diffracted light and -1st-order diffracted light mainly contribute to the reproduction of the optical image 200a and the optical images 200b and 200c shown in FIGS. 9A and 9B, respectively. Higher-order diffracted light of the second order or higher at the element element 21 does not contribute to clear reproduction of the optical images 200a, 200b, and 200c. Part of the incident light incident on the element element 21 is transmitted through the element element 21 without being diffracted by the element element 21 and becomes 0th-order light, but the 0th-order light only generates a light image of a point. , and does not contribute to the reproduction of the optical images 200a, 200b, and 200c.

As shown in FIG. 8, the element elements 21 forming the optical modulation element 11 exhibit specific diffraction efficiencies according to wavelengths. Specifically, the element element 21 exhibits high diffraction efficiency with respect to first-order diffracted light for light in the first wavelength band (specifically, light in a wavelength band including the first wavelength of 520 nm). This indicates that the element element 21 efficiently diffracts the first-order diffracted light in the first wavelength band. The 1st-order diffracted light at the element element 21 is light in the first wavelength band, and reproduces the first optical image 200a of the character "OK" shown in FIG. 9A. The light in the first wavelength band reproduces the first optical image 200a, but does not reproduce the second optical image 200b and the third optical image 200c. In the present specification, "reproducing" an optical image means generating an optical image by first-order diffracted light or −1st-order diffracted light diffracted with a diffraction efficiency of 50% or more in the element element 21. . Therefore, for example, in the example shown in FIG. 8, light in the first wavelength band is light with a wavelength of 500 nm or more and 545 nm or less.

In addition, the element element 21 constituting the light modulation element 11 has a high light in a second wavelength band different from the first wavelength band (specifically, light in a wavelength band including the second wavelength of 665 nm) with respect to the −1st order diffracted light. Diffraction efficiency is shown. This indicates that the element element 21 efficiently diffracts the −1st order diffracted light in the second wavelength region. The −1st-order diffracted light at the element element 21 is light in the second wavelength band, and reproduces the second optical image 200b of the characters “OK” shown in FIG. 9B. As understood from FIGS. 9A and 9B, the second optical image 200b is an image point-symmetrical to the first optical image 200b. The light in the second wavelength region reproduces the second optical image 200b, but does not reproduce the first optical image 200a and the third optical image 200c. In the example shown in FIG. 8, light in the second wavelength range is light with a wavelength of 630 nm or more and 705 nm or less.

Also, the second optical image 200b is reproduced at a position overlapping the first optical image 200a. As a result, when light including light in the first wavelength region and light in the second wavelength region, such as white light, is incident on the light modulation element 11, the first optical image 200a and the second optical image 200b are formed. By overlapping, an optical image different from the first optical image 200a is obtained.

In the example shown in FIG. 8, the element element 21 constituting the light modulation element 11 is light in a third wavelength range different from the first wavelength range and the second wavelength range (specifically, includes the third wavelength 420 nm). wavelength band) also exhibits high diffraction efficiency with respect to -1st order diffracted light. This indicates that the element element 21 efficiently diffracts the −1st order diffracted light even in the third wavelength region. The −1st-order diffracted light at the element element 21 is light in the third wavelength band, and reproduces the third optical image of the characters “OK” shown in FIG. 9C. As understood from FIGS. 9A and 9C, the third optical image 200c is point-symmetrical to the first optical image. The light in the third wavelength band reproduces the third optical image 200c, but does not reproduce the first optical image 200a and the second optical image 200b. Further, the light in the third wavelength range is light with a wavelength of 410 nm or more and 440 nm or less.

Further, as shown in FIG. 6, the third optical image 200c is also reproduced at a position overlapping the first optical image 200a. Accordingly, when light including light in the first wavelength band and light in the third wavelength band, such as white light, is incident on the light modulation element 11, the first optical image 200a and the third optical image 200c are formed. By overlapping, an optical image different from the first optical image 200a is obtained.

As can be understood from the above, in the example shown in FIG. 8, the optical image 100 shown in FIG. and the third optical image 200c overlap each other.

In the authenticity determination device 300 shown in FIG. 7, the light modulation element 11 configured by the element elements 21 having the diffraction efficiency characteristics shown in FIG. When light that does not contain light is incident, a first light image 200a of characters "OK" as shown in FIG. 7 is clearly observed. On the other hand, as shown in FIG. 6, when white light is incident on the light modulation element 11, the optical images 200a, 200b, and 200c are superimposed, and an optical image 100 different from the first optical image 200a is observed. .

The diffraction efficiency characteristic shown in FIG. It is obtained when the element element 21 is designed as 390 nm. However, the light modulation element 11 that obtains the first optical image with the light in the first wavelength range and obtains the second optical image with the light in the second wavelength range different from the first wavelength range is designed as described above. It is not limited to the optical modulation element 11 that is provided.

For example, the element element 21 constituting the light modulation element 11 is made of a material with a refractive index n of 1.5, and the light modulation element 11 is formed by setting the number of steps on the uneven surface 1a to 4 and the depth of each step to 400 nm. When designed, the elemental element 21 has diffraction efficiency characteristics as shown in FIG. That is, the element element 21 exhibits high diffraction efficiency with respect to first-order diffracted light for light in the first wavelength range (specifically, light in the wavelength range of 510 nm or more and 550 nm or less including the first wavelength of 520 nm). Further, the element element 21 emits light in the second wavelength range (specifically, light in the wavelength range of 655 nm or more and 710 nm or less including the second wavelength of 680 nm) and light in the third wavelength range (specifically, the third wavelength of 430 nm light in the wavelength range of 425 nm or more and 450 nm or less including ) exhibits high diffraction efficiency with respect to −1st order diffracted light.

Even with the light modulation element 11 composed of the element elements 21 having the diffraction efficiency characteristics shown in FIG. , and the −1st-order diffracted light at the optical modulation element 11 forms a second optical image 200b shown in FIG. 9B with light in the second wavelength band, and a third optical image 200c shown in FIG. can be played. Therefore, in the authentication device 300 shown in FIG. 7, the light modulation element 11 contains light in the first wavelength band (specifically, light in the wavelength band of 510 nm or more and 550 nm or less), but light in the second wavelength band (specifically, When light that does not include light in the wavelength range of 655 nm or more and 710 nm or less) and light in the third wavelength range (specifically, light in the wavelength range of 425 nm or more and 450 nm or less) is made incident, as shown in FIG. A first optical image 200a of characters "OK" is clearly observed. On the other hand, as shown in FIG. 6, when white light is incident on the light modulation element 11, the optical images 200a, 200b, and 200c are superimposed, and an optical image 100 different from the optical image 200a is observed (see FIG. 6). 6).

Further, the element element 21 constituting the light modulation element 11 is made of a material having a refractive index n of 1.5, and the element element 21 is designed such that the number of steps on the uneven surface 1a is 8 steps and the depth of each step is 200 nm. In this case, the element element 21 has diffraction efficiency characteristics as shown in FIG. That is, the element element 21 exhibits high diffraction efficiency with respect to first-order diffracted light for light in the first wavelength range (specifically, light in the wavelength range of 510 nm or more and 550 nm or less including the first wavelength of 530 nm). Further, the element element 21 exhibits high diffraction efficiency with respect to -1st order diffracted light for light in the second wavelength range (specifically, light in the wavelength range of 650 nm or more and 710 nm or less including the second wavelength of 680 nm).

Even with the light modulation element 11 composed of the element elements 21 having the diffraction efficiency characteristics shown in FIG. , and the −1st-order diffracted light at the optical modulation element 11 can reproduce the second optical image 200b shown in FIG. 9B with the light in the second wavelength region. Therefore, in the authentication device 300 shown in FIG. 7, the light modulation element 11 contains light in the first wavelength band (specifically, light in the wavelength band of 510 nm or more and 550 nm or less), but light in the second wavelength band (specifically, When light that does not include light in the wavelength range of 650 nm or more and 710 nm or less is incident on the light, a first optical image 200a of the letters "OK" as shown in FIG. 7 is clearly observed. On the other hand, as shown in FIG. 6, when white light is incident on the light modulation element 11, the optical images 200a and 200b are superimposed and an optical image different from the optical image 200a is observed.

Further, the element element 21 constituting the light modulation element 11 is made of a material with a refractive index n of 1.5, and the element element 21 is designed so that the uneven surface 1a has four steps and the depth of each step is 190 nm. In this case, the element element 21 has diffraction efficiency characteristics as shown in FIG. That is, the element element 21 exhibits high diffraction efficiency with respect to first-order diffracted light for light in the first wavelength range (specifically, light in the wavelength range of 420 nm or more and 490 nm or less including the first wavelength of 460 nm). In addition, the light modulation element 11 exhibits high diffraction efficiency with respect to -1st order diffracted light for light in the second wavelength region (specifically, light of 690 nm or more and 780 nm or less including the second wavelength of 750 nm).

Even with the light modulation element 11 composed of the element elements 21 having the diffraction efficiency characteristics shown in FIG. , and the −1st-order diffracted light at the optical modulation element 11 can reproduce the second optical image 200b shown in FIG. 9B with the light in the second wavelength region. Therefore, the optical modulation element 11 contains light in the first wavelength range (specifically, light in the wavelength range of 420 nm or more and 490 nm or less) in the authenticity determination device 300 shown in FIG. 780 nm or less), the first optical image 200a of the character "OK" as shown in FIG. 7 is clearly observed. On the other hand, as shown in FIG. 6, when white light is incident on the light modulation element 11, the optical images 200a and 200b are superimposed and an optical image different from the optical image 200a is observed.

Further, the element element 21 constituting the light modulation element 11 is made of a material having a refractive index n of 1.5, and the element element 21 is designed such that the uneven surface 1a has four steps and the depth of each step is 280 nm. In this case, the element element 21 has diffraction efficiency characteristics as shown in FIG. That is, the element element 21 exhibits high diffraction efficiency with respect to first-order diffracted light for light in the first wavelength range (specifically, light in the wavelength range of 625 nm or more and 710 nm or less including the first wavelength of 650 nm). In addition, the element element 21 exhibits high diffraction efficiency with respect to -1st order diffracted light for light in the second wavelength range (specifically, light in the wavelength range of 460 nm or more and 495 nm or less including the second wavelength of 480 nm).

Even with the light modulation element 11 configured by the element elements 21 having the diffraction efficiency characteristic shown in FIG. , and the −1st-order diffracted light at the optical modulation element 11 can reproduce the second optical image 200b shown in FIG. 9B with the light in the second wavelength region. Therefore, in the authentication device 300 shown in FIG. 7, the optical modulation element 11 contains light in the first wavelength range (specifically, light in the wavelength range of 625 nm or more and 710 nm or less), but light in the second wavelength range (specifically, When light that does not include light in the wavelength range of 460 nm or more and 495 nm or less is incident on the light, a first optical image 200a of the characters "OK" as shown in FIG. 7 is clearly observed. On the other hand, as shown in FIG. 6, when white light is incident on the light modulation element 11, the optical images 200a and 200b are superimposed and an optical image different from the optical image 200a is observed.

Note that the authenticity determination device 300 may include the light modulation element 11 and a filter that transmits light that does not include either the light in the first wavelength band or the light in the second wavelength band. Also in this case, by filtering the light diffracted by the light modulation element 11 with a filter, the first optical image 200a or the second optical image 200b can be obtained. Of course, when the light modulation element 11 is composed of the element elements 21 having the diffraction efficiency characteristics shown in FIG. 8 or FIG. It may be a filter that transmits light that does not contain light in one or more wavelength bands selected from among, for example, a filter that transmits light that does not contain light in the second wavelength band and light in the third wavelength band. It's okay.

Further, the authenticity determination device 300 may include the light modulation element 11 and an image analysis device that captures light including one of the light in the first wavelength band and the light in the second wavelength band and excluding the other. In this case as well, the first optical image 200a or the second optical image 200b can be obtained by selectively taking in the light diffracted by the light modulation element 11 with the image analyzer. Of course, when the light modulation element 11 is composed of the element elements 21 having the diffraction efficiency characteristics shown in FIG. 8 or FIG. It may capture light excluding light in one or more wavelength bands selected from the band, for example capturing light excluding light in a second wavelength band and light in a third wavelength band. It's okay.

Note that the optical images 200a, 200b, and 200c shown in FIGS. 9A to 9C are merely examples of optical images that can be reproduced by the light modulation element 11 of this embodiment, and the light modulation element 11 can be used for other shapes of light. It may be one that reproduces an image.

Further, in the above-described embodiments, the wavelength range of the incident light was 380 nm or more and 780 nm or less, so the first wavelength range and the second wavelength range were also 380 nm or more and 780 nm or less. In this case, the optical images 200a, 200b, 200c and the optical image 100 can be visually recognized. However, the first wavelength range and the second wavelength range are not limited to the wavelength ranges described above, and may be wavelength ranges outside the so-called visible light range. In particular, when the authenticity determination device 300 includes the image analysis device described above, the optical images 200a, 200b, 200c, and 100 may not be visually recognized, and may be grasped by the analysis results of the image analysis device.

Next, an example of a method for manufacturing the light modulation element 11 (especially the uneven surface 1a) will be described. The method described below is merely an example, and other methods capable of appropriately manufacturing the light modulation element 11 including the desired uneven surface 1a can be adopted. Moreover, the manufacturing method described below can be applied to both the reflective optical modulator and the transmissive optical modulator.

First, a two-dimensional image of an original image is read by a computer (Step 1). Then, the computer obtains a two-dimensional complex amplitude image by setting each pixel value of the read two-dimensional image as an amplitude value and assigning a random value between 0 and 2π to each pixel as a phase value ( Step 2). The computer then obtains a two-dimensional Fourier transform image by performing a two-dimensional Fourier transform on this two-dimensional complex amplitude image (Step 3). Note that the computer may perform arbitrary optimization processing, such as an iterative Fourier transform method or a genetic algorithm, if necessary (Step 4). Then, the computer converts the phase value of each pixel of the two-dimensional Fourier transform image into multiple stages (for example, four stages of "0", "π/2", "π" and "3π/2", or "0", " π/4”, “π/2”, “3π/4”, “π”, “5π/4”, “3π/2” and “7π/4”) (Step 5).

Then, the light modulation element 11 (in particular, the uneven surface 1a) corresponding to the two-dimensional Fourier transform image is produced so that each pixel has a depth corresponding to the corresponding discretized phase value (Step 6). For example, when the pixel values of the two-dimensional Fourier transform image are discretized into four levels in Step 5 described above, an uneven surface 1a (see FIG. 5) having four levels of depth is formed on the hologram layer 1 in Step 6. be. The depth of the concave-convex surface 1a is determined by considering not only the diffraction efficiency characteristics to be achieved but also various other related parameters (for example, the refractive index of the material constituting the light modulation element 11 (especially the hologram layer 1)). determined by Note that the reflective optical modulation element 11 and the transmissive optical modulation element 11 each have a unique depth structure of the uneven surface 1a. A specific value of the depth of the uneven surface 1a of the element 11 differs between the reflective type and the transmissive type.

The apparatus for manufacturing the light modulation element 11 is not particularly limited, and may be, for example, an apparatus controlled by a computer that executes Steps 1 to 5 described above, or may be an apparatus provided separately from the computer. . Further, if necessary, a matrix (that is, a master original) corresponding to the structure of the light modulation element 11 (especially the concave-convex surface 1a) may be made using an exposure apparatus, an electron beam lithography apparatus, or the like based on photolithography technology. (Step 7). For example, a liquid ultraviolet curable resin is dropped onto the matrix, and the ultraviolet curable resin sandwiched between the substrate film (for example, PET film (polyethylene terephthalate film)) and the matrix is irradiated with ultraviolet rays. Then, the substrate film and the ultraviolet curable resin are peeled off from the master mold, whereby the light modulation element 11 having the desired uneven surface 1a can be produced. As other methods, for example, a method using a thermoplastic ultraviolet curable resin, a method using a thermoplastic resin, a method using a thermosetting resin, and a method using an ionizing radiation curable resin may be employed. By using the matrix in this way, it is possible to easily and mass-produce the light modulation elements 11 having the desired uneven surface 1a.

In the case of the reflective optical modulation element 11, a reflective layer 2 (for example, a reflective layer made of Al or ZnS or a reflective layer (high refractive index layer) made of TiO ₂ ) is further formed on the uneven surface 1a by a manufacturing apparatus. may be formed. However, in the case of the light modulation element 11 that reflects the reproduced light by utilizing the difference in refractive index between the hologram layer 1 and air, the reflective layer 2 is not additionally provided, and the uneven surface of the hologram layer 1 is used. 1a may remain exposed to the air. Furthermore, other functional layers such as an adhesive layer (for example, a heat seal layer, a primer layer for enhancing adhesion between adjacent layers, etc.) may be formed on the hologram layer 1 as necessary. Further, for example, when the reflective layer 2 is formed on the uneven surface 1a of the hologram layer 1, an adhesive layer is formed on the uneven surface of the reflective layer 2 (the surface opposite to the hologram layer 1), The recesses on the surface of the reflective layer 2 may be filled with the layer.

It should be noted that the color (wavelength band) of the optical image reproduced by the above-described light modulation element 11 assumes that it is used in an air environment with a refractive index of 1.0. When an observer observes the optical image 100 reproduced by the above-described light modulation element 11, the uneven surface 1a of the hologram layer 1 is arranged on the opposite side of the observer, and the observer can see the uneven structure ( That is, the uneven surface 1a) is observed. When the uneven surface 1a of the hologram layer 1 is arranged on the same side as the observer, the reflected image from the light modulation element 11 observed by the observer is formed by the light reflected on the surface without passing through the hologram layer 1. Therefore, the image is unrelated to the diffraction phenomenon based on the refractive index of the hologram layer 1 and is not the desired image.

According to the embodiment as described above, the light modulation element 11 includes the element element 21 that reproduces an optical image by modulating the phase of incident light, and the element element 21 includes three or more different heights. It has an uneven surface 1a, a first optical image 200a is obtained by light in a first wavelength range, and a second optical image 200a is obtained at a position overlapping the first optical image 200a by light in a second wavelength range different from the first wavelength range. 200b is obtained

According to such an optical modulation element 11, when light including one of the light in the first wavelength band and the light in the second wavelength band and excluding the other is made incident on the optical modulation element 11, as shown in FIG. , one of the first optical image 200a and the second optical image 200b can be clearly obtained. On the other hand, according to the light modulation element 11, when light including light in the first wavelength band and light in the second wavelength band (for example, light including light of various wavelengths such as white light) is incident, , an optical image in which the first optical image 200a and the second optical image 200b are overlapped as shown in FIG. 6 is obtained. The light modulation element 11 having such properties obtains specific optical images 200a and 200b only when light containing one of the light in the first wavelength range and the light in the second wavelength range and excluding the other is incident. Therefore, it can be used for identification (for example, authenticity determination) of the light modulation element holder 10 . Further, according to the light modulation element 11 having such properties, when light including one of the light in the first wavelength band and the light in the second wavelength band and excluding the other is incident, the light in the first wavelength band Since a different optical image can be obtained when light including light in the second wavelength band (for example, light such as white light) is incident, the design of the light modulation element holder 10 can be improved. can.

Further, in the light modulation element 11 of this embodiment, each element element 21 is configured as a Fourier transform hologram. Thereby, the element element 21 capable of reproducing the desired optical images 200a and 200b with high accuracy can be produced relatively easily.

Further, in the light modulation element 11 of the present embodiment, the element element 21 reproduces the first optical image 200a with the light in the first wavelength band, and reproduces the first optical image 200a with the light in the second wavelength band. Two optical images 200b are reproduced. As a result, the optical images 200a and 200c obtained when the light including one of the light in the first wavelength band and the light in the second wavelength band and excluding the other is incident on the light modulation element 11, and It is easy to make the optical image different from that obtained when light including light in one wavelength band and light in a second wavelength band (for example, light such as white light) is incident.

Further, in the optical modulation element 11 of the present embodiment, the first wavelength range and the second wavelength range are 380 nm or more and 780 nm or less. In this case, changes in the optical images 100, 200a, and 200b obtained by the diffracted light from the light modulation element 11 can be visually recognized.

Further, according to the above-described embodiment, the authenticity determination device 300 emits light containing one of the light in the first wavelength band and the light in the second wavelength band and excluding the other light from the light modulation element 11 described above. light source device 251, a filter that transmits light including one of light in the first wavelength band and light in the second wavelength band and excluding the other, and one of the light in the first wavelength band and the light in the second wavelength band and at least one of an image analysis device that captures light, including and excluding the other. According to such an authenticity determination device 300, it is easy to perform authenticity determination.

[Modification]
Modifications of the embodiment shown in FIGS. 1 to 13 will now be described with reference to FIGS. 14 to 15B. In the examples shown in FIGS. 1 to 13, each of the element elements constituting the light modulation element contributes to both the reproduction of the first optical image and the reproduction of the second optical image. However, in the light modulation element of this modified example, the element element that contributes to the reproduction of the first optical image and the element element that contributes to the reproduction of the second optical image are different. Hereinafter, the light modulation element of this modified example will be described in detail with reference to the drawings.

FIG. 14 is a diagram showing the configuration of the light modulation element of this modified example. 15A and 15B are diagrams for explaining optical images obtained by the first element element and the second element element that constitute the light modulation element of FIG. 14. FIG.

As shown in FIG. 14, the light modulation element 11 of this modification includes a first element element 121 that reproduces a first optical image 300a with light in the first wavelength band, and a second optical image 300a with light in the second wavelength band. and a second element element 221 for reproducing 300b. In the example shown in FIG. 14, a plurality of first element elements 121 and a plurality of second element elements 221 are arranged in a checkered pattern on the same plane.

The first element element 121 and the second element element 221 shown in FIG. 14 are made of a material with a refractive index n of 1.5, and the uneven surface 1a has eight steps, each step having a depth of 200 nm. is. The first element element 121 and the second element element 221 have diffraction efficiency characteristics shown in FIG.

Further, in the first element element 121 shown in FIG. 14, when light including light in the first wavelength band and light in the second wavelength band such as white light is incident, as shown in FIG. Light (specifically, light in a wavelength range of 510 nm or more and 550 nm or less) is diffracted to reproduce the first optical image 300a of the letter "O", and light in a second wavelength range (specifically, 650 nm or more and 710 nm). light in the following wavelength ranges) is diffracted to reproduce a third optical image 300c of the letter "O" that is point-symmetrical to the first optical image 300a. In addition, in the second element element 221 shown in FIG. 14, when light including light in the first wavelength band and light in the second wavelength band such as white light is incident, as shown in FIG. Light (specifically, light in the wavelength range of 510 nm or more and 550 nm or less) is diffracted to reproduce the fourth optical image 300d of the letter "K", and light in the second wavelength range (specifically, 650 nm or more and 710 nm light in the following wavelength ranges) is diffracted to reproduce a second optical image 300b of the letter "K" that is point-symmetrical to the fourth optical image 300d. Then, it is obtained at a position where the first optical image 300a and the second optical image 300b overlap, and at a position where the third optical image 300c and the fourth optical image 300d overlap.

With such an optical modulation element 111, the same effect as that of the optical modulation element 11 shown in FIG. 3 can be obtained. That is, in the authenticity determination device 300, light in a first wavelength range (specifically, light in a wavelength range of 510 nm to 550 nm) and light in a second wavelength range (specifically, light in a wavelength range of 650 nm to 710 nm) are applied to the optical modulation element 111. Either one of the first optical image 300a and the second optical image 300b can be obtained by entering light that includes one of the wavelength bands and does not include the other. At the same time, either one of the fourth optical image 300d and the third optical image 300c can be obtained. Therefore, by inputting light that includes one of the light in the first wavelength band and the light in the second wavelength band and does not include the other, the first optical image 300a and the fourth optical image 300d are reproduced, or the second The optical image 300b and the third optical image 300c are reproduced, and an optical image of characters "OK" as shown in FIG. 7 can be obtained. On the other hand, when light including light in the first wavelength band and the second wavelength band (for example, light such as white light) enters the light modulation element 111, the first optical image 300a and the second optical image 300b are superimposed. An optical image and an optical image in which the third optical image 300c and the fourth optical image 300d are superimposed are obtained.

14, the first element element 121 and the second element element 221 are arranged in a checkered pattern on the same plane. 221 is not particularly limited. For example, the light modulation element 11 may include the first element element 121 and the second element element 221 arranged in stripes on the same plane.

As described above, the light modulation element 111 of this modification includes the first element element 121 that reproduces the first optical image 300a with the light in the first wavelength band and the second optical image 300b with the light in the second wavelength band. and a second element element 221 . According to such an optical modulation element 111, by causing light in a specific wavelength range (that is, light in the first wavelength range or light in the second wavelength range) to enter the optical modulation element 111, One of the shown first optical image 300a and second optical image 300b can be clearly obtained. On the other hand, according to the light modulation element 111 as described above, by allowing light including light in the first wavelength band and light in the second wavelength band (for example, light such as white light) to enter the light modulation element 111, The first optical image 300a and the second optical image 300b overlap to obtain an optical image different from the first optical image 300a and the second optical image 300b. The light modulation element 111 having such properties can be used for identifying the light modulation element holder 10 (for example, authenticity determination), and can improve the design of the light modulation element holder 10 .

[Use]
The light modulation elements 11 and 111 and the light modulation element holder 10 described above are not particularly limited in usage and application, and can be used for entertainment purposes such as reproduction of character images and design purposes, for example. In security applications, the optical modulation elements 11 and 111 can be applied to, for example, the following objects. When the light modulation element holder 10 is used as an information recording medium, various types of information such as passports, ID cards, banknotes, credit cards, cash vouchers, gift certificates, other tickets, official documents, personal information and confidential information can be stored. The light modulation element according to the present invention can be applied to other recorded media, other media with monetary value, etc., and counterfeiting of these media can be prevented. The ID card referred to here includes, for example, a national ID card, a driver's license, a membership card, an employee card, and a student card. In the light modulation element holder 10, the base material for holding the light modulation elements 11 and 111 (see reference numeral 4 in FIG. 2) can be made of, for example, paper, resin, metal, synthetic fiber, or a combination thereof. . Further, when an opening (see reference numeral 4a in FIG. 2) is formed in the base material, the entire area of the opening may be covered with the light modulation elements 11 and 111, or only a part of the opening may be covered. Light modulation elements 11 and 111 may be arranged. The light modulation elements 11 and 111 can be configured as transparent members in appearance. For example, a point light source is arranged on the back side of the light modulation element holder 10 holding the transmissive light modulation elements 11 and 111, and the observer passes through the light modulation elements 11 and 111 from the front side of the light modulation element holder 10. , the observer can visually recognize the security information recorded in the light modulation elements 11 and 111 by observing a point light source or the like in a specific wavelength range. This security information can be used, for example, to determine the authenticity of the light modulation element holder 10 .

Further, the optical modulation element according to the present invention can be applied to the optical modulation element holder 10 described above by any method. Techniques such as pasting, sandwiching, or embedding can be used to hold the optical modulator according to the present invention on any object (that is, the optical modulator holder 10). Therefore, the light modulation elements 11 and 111 may be formed using a part of the members constituting the light modulation element holder 10, or the light modulation elements 11 and 111 may be added to the light modulation element holder 10. can be set

Further, the light modulation element 11 described above may be used alone for various purposes, or may be used together with other functional layers such as a printed layer for various purposes.

[Constituent material of hologram layer]
The material forming the hologram layer 1 is not particularly limited, but the hologram layer 1 can be formed from various resins as described above. Specific examples of various resins are listed below.

Examples of thermosetting resins constituting the hologram layer 1 include polycarbonate (PC), polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PET-G), polyvinyl chloride (PVC), unsaturated polyester resins, and acrylic-modified resins. Examples include urethane resins, epoxy-modified acrylic resins, epoxy-modified unsaturated polyester resins, alkyd resins, phenol resins, and the like. Examples of the thermoplastic resin forming the hologram layer 1 include acrylic acid ester resin, acrylamide resin, nitrocellulose resin, polystyrene resin, and the like. These resins may be homopolymers or copolymers composed of two or more constituents. Moreover, these resins may be used alone, or two or more of them may be used in combination.

The above-mentioned thermosetting resins or thermoplastic resins include various isocyanate compounds, metallic soaps such as cobalt naphthenate and zinc naphthenate, organic peroxides such as benzoyl peroxide and methyl ethyl ketone peroxide, benzophenone, acetophenone, anthraquinone, naphthoquinone, A thermal or ultraviolet curing agent such as azobisisobutyronitrile, diphenyl sulfide, etc. may be included.

Examples of the ionizing radiation-curable resin constituting the hologram layer 1 include epoxy-modified acrylate resins, urethane-modified acrylate resins, acrylic-modified polyester resins, and the like. A urethane-modified acrylic resin represented by a chemical formula shown in a publication is preferred.

When curing the ionizing radiation-curable resin, a monofunctional or polyfunctional monomer, oligomer, or the like can be used in combination for the purpose of adjusting the crosslinked structure and viscosity. Examples of the monofunctional monomer include mono(meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, hydroxyethyl (meth)acrylate, vinylpyrrolidone, (meth)acryloyloxyethyl succinate, and (meth)acryloyloxyethyl phthalate. etc. In addition, as the bifunctional or higher monomers, when classified by the skeleton structure, polyol (meth)acrylate (e.g., epoxy-modified polyol (meth)acrylate, lactone-modified polyol (meth)acrylate, etc.), polyester (meth)acrylate, epoxy (meth)acrylate, ) acrylates, urethane (meth)acrylates, polybutadiene-based, isocyanuric acid-based, hydantoin-based, melamine-based, phosphoric acid-based, imide-based, and phosphazene-based poly(meth)acrylates having a skeleton. In addition, various monomers, oligomers and polymers that are UV and electron beam curable are available.

More specifically, examples of bifunctional monomers and oligomers include polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth) acrylates and the like. Examples of trifunctional monomers, oligomers, and polymers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and aliphatic tri(meth)acrylate. Examples of tetrafunctional monomers and oligomers include pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and aliphatic tetra(meth)acrylate. Penta- or higher-functional monomers and oligomers include, for example, dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate. Also included are (meth)acrylates having a polyester skeleton, a urethane skeleton, and a phosphazene skeleton. The number of functional groups is not particularly limited, but when the number of functional groups is less than 3, the heat resistance tends to decrease, and when the number of functional groups exceeds 20, the flexibility tends to decrease. Those within the range of 3 to 20 are preferred.

Although the content of the monofunctional or polyfunctional monomers and oligomers as described above can be adjusted as appropriate, it is usually preferably 50 parts by weight or less with respect to 100 parts by weight of the ionizing radiation curable resin, especially 0.5 parts by weight. parts to 20 parts by weight is preferred.

Further, the hologram layer 1 may optionally contain a photopolymerization initiator, a polymerization inhibitor, a deterioration inhibitor, a plasticizer, a lubricant, a coloring agent such as a dye or a pigment, a surfactant, an antifoaming agent, a leveling agent, and Additives such as thixotropic agents may be added as appropriate.

When the hologram layer 1 has self-supporting properties, the film thickness of the hologram layer 1 is preferably in the range of 0.05 mm to 5 mm, more preferably in the range of 0.1 mm to 3 mm. On the other hand, when the hologram layer 1 is formed on a transparent substrate without self-supporting properties, the film thickness of the hologram layer 1 is preferably in the range of 0.1 μm to 50 μm, more preferably in the range of 2 μm to 20 μm. It is preferable to Also, the size of the hologram layer 1 (for example, the size in plan view) can be appropriately set according to the use of the light modulation element 11 .

[Other Modifications]
The light modulation elements 11 and 111 used in each of the above-described embodiments and modifications each include a plurality of element elements 21 or a plurality of first element elements 121 and a plurality of second element elements as shown in FIGS. Although it is composed of the element 221 , the light modulation elements 11 and 111 may be composed of a single element element 21 or a single first element element 121 and a single second element element 221 .

Also, the planar view size and planar view shape of each element element 21, 121, 221 are not particularly limited, and each element element 21, 121, 221 can have any size and shape. For example, the plane view shape of each of the element elements 21, 121, 221 may be square, rectangle, trapezoid, other polygonal shape (for example, triangle, pentagon, hexagon, etc.), perfect circle, ellipse, other circle, star. It may have a mold shape, a heart shape, or the like, and the light modulation elements 11 and 111 may have two or more types of element elements 21 having a plan view shape.

Any functional layer may be added to the light modulation elements 11 and 111, for example, the light modulation elements 11 and 111 may be covered with a transparent deposition layer. In particular, by providing a transparent deposition layer that does not have gloss, the light modulation elements 11 and 111 can be prevented from being glossy and can be concealed. From the viewpoint of concealing the light modulation elements 11 and 111, the total light transmittance of such a transparent deposition layer is preferably 80% or more, and more preferably 90% or more. Further, in the case of the reflection type light modulation elements 11 and 111, the light modulation elements 11 and 111 can be covered with a reflective deposition layer (see the reflection layer 2 in FIG. 2). Examples of constituent materials of the reflective deposition layer include Mg, Al, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Se, Rb, Pd, Ag, Cd, In, Sn, Sb, Te, Metals such as Au, Pb, or Bi can be used. Further, examples of the constituent material of the transparent deposition layer include oxides of the above metals. These materials may be used alone to form the vapor deposition layer, or two or more materials may be combined to form the vapor deposition layer.

The thickness of the deposited layer provided on the hologram layer 1 (especially on the uneven surface 1a) can be set as appropriate from the viewpoint of desired reflectivity, color tone, design and application, and is, for example, within the range of 50 Å to 1 μm. It is preferably within the range of 100 Å to 1000 Å. In particular, when the transparency of the deposited layer is given priority, the thickness of the deposited layer is preferably 200 Å or less, while when the concealability of the deposited layer is given priority, the thickness of the deposited layer is more than 200 Å. is preferred. As a method for forming the vapor deposition layer, a general method for forming a vapor deposition layer can be employed, and examples thereof include a vacuum vapor deposition method, a sputtering method and an ion plating method.

[Comparative example]
Next, a comparative example of the above embodiment will be described with reference to FIGS. 16 and 17. FIG.

FIG. 16 is a diagram showing an optical modulation element of this comparative example. FIG. 17 is a graph showing the diffraction efficiency characteristics of the element elements forming the light modulation element of this comparative example.

The light modulation element 311 shown in FIG. 16 is a conventional light modulation element. In the example shown in FIG. 17, the element elements forming the light modulation element 311 are made of a material with a refractive index n of 1.5, and the uneven surface 301a has four steps. The step d per step is 46.25 nm. Elemental elements forming the light modulation element 311 have diffraction efficiency characteristics as shown in FIG. That is, each element diffracts the first-order diffracted light with a diffraction efficiency of approximately 50% or more over the entire wavelength range of 380 nm or more and 780 nm or less. This is the same as the light image 400 obtained when white light is incident on the light modulation element 311 shown in FIG. It shows that an optical image can be obtained. On the other hand, each element diffracts −1st-order diffracted light with a diffraction efficiency of 10% or less over the entire wavelength range from 380 nm to 780 nm. Therefore, it is impossible to observe the optical image by the -1st order diffracted light at the light modulation element 311 even if the light in any wavelength range of 380 nm or more and 780 nm or less is incident. Depending on the light modulation element 311, different optical images can be obtained depending on whether light in a specific wavelength range is incident or light including various wavelengths such as white light is incident. Can not.

The invention is not limited to the embodiments and variants described above. For example, various modifications may be made to each element of the embodiments and modifications described above. Forms including components and/or methods other than the components and/or methods described above may also be included in embodiments of the present invention. Forms that do not include some of the components and/or methods described above may also be included in embodiments of the present invention. In addition, a form including some components and/or methods included in one embodiment of the present invention and some components and/or methods included in other embodiments of the present invention may also be included in the present invention. can be included in an embodiment. Therefore, the components and/or methods included in each of the above-described embodiments and modifications, and other embodiments of the present invention may be combined with each other, and the forms according to such combinations may also be implemented in the present invention. can be included in the form. Further, the effects achieved by the present invention are not limited to those described above, and specific effects according to the specific configurations of the respective embodiments can also be exhibited. Thus, various additions, changes, and partial deletions can be made to each element described in the claims, specification, abstract, and drawings without departing from the technical idea and gist of the present invention. is.

1 Hologram layer 1a Concavo-convex surface 2 Reflective layer 4 Base material 10 Light modulation element holder 11 Light modulation elements 21, 121, 221 Element elements 151, 251 Light source devices 100, 400 Optical images 200a, 300a First optical images 200b, 300b 2 light images

Claims (7)

Equipped with an element element that reproduces an optical image by modulating the phase of incident light,
The element element has an uneven surface with three or more different heights,
A light modulation element in which a first optical image is obtained by light in a first wavelength range, and a second optical image is obtained in a position overlapping the first optical image by light in a second wavelength range different from the first wavelength range. There is
The refractive index of the element element, the number of steps on the uneven surface, and the depth of each step on the uneven surface are different from the first wavelength range so that a first optical image is obtained by light in a first wavelength range. is determined so that a second optical image is obtained at a position overlapping the first optical image by light of two wavelength ranges;
when the optical modulation element is a reflective optical modulation element, the first optical image and the second optical image are both obtained by light reflected by the optical modulation element,
when the light modulation element is a transmissive light modulation element, both the first optical image and the second light image are obtained by light transmitted through the light modulation element ,
The optical modulation element , wherein when the first optical image and the second optical image are overlapped, an optical image different from the first optical image is obtained . 2. The light modulation element according to claim 1, wherein said element element is configured as a Fourier transform hologram. The element element reproduces the first optical image with light in the first wavelength band, and reproduces the second optical image point-symmetrically with the first optical image with light in the second wavelength band. 3. The optical modulation element according to claim 1 or 2. 2. The apparatus according to claim 1, comprising a first element element that reproduces the first optical image with light in the first wavelength band, and a second element element that reproduces the second optical image with light in the second wavelength band. 3. The light modulation element according to claim 2. 5. The light modulation element according to claim 4, wherein said first element element and said second element element are arranged side by side on the same plane. 6. The light modulation element according to claim 1, wherein said first wavelength band and said second wavelength band are from 380 nm to 780 nm. a light modulation element according to any one of claims 1 to 6;
A light source device that emits light containing one of the light in the first wavelength range and the light in the second wavelength range and excluding the other, and the other containing the light in the first wavelength range and the light in the second wavelength range and at least one of a filter that transmits light that does not contain and an image analysis device that captures light containing one of the light in the first wavelength range and the light in the second wavelength range and excluding the other. Device.

Images