JP2000304912A - Diffraction grating pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate irregularity of diffraction efficiency of the whole pattern by letting a two-dimensional pattern constituted of an assemble of micro cells formed of a straight line diffraction grating and a three-dimensional pattern constituted of an assembled of micro cells formed of a curved line diffraction grating co-existing within the same region of the same substrate. SOLUTION: The diffraction grating pattern is formed by letting a three- dimensional diffraction grating pattern and a planar diffraction grating pattern co-existing within the same region of the same substrate. That is, around a cell 13 made of curved line grating constituting the three-dimensional diffraction grating pattern, a cell 12 made of straight line grating constituting the planar diffraction grating pattern is arranged. Consequently, as each of the three- dimensional pattern and the planar pattern is visually sensed without irregularity of the whole brightness (diffraction effect) and as the perfect pattern, versatile expressions with high eye-catch effect can be realized. Furthermore at the time of used for security use, forgery and imitation become more difficult.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern (hereinafter, referred to as a diffraction grating pattern) in which minute cells (dots) made of a diffraction grating are arranged on the surface of a substrate, and are represented by a group of these cells.

[0002]

2. Description of the Related Art A pattern (display) formed by arranging a plurality of minute dots made of a diffraction grating on the surface of a planar substrate is known. Japanese Patent Application Laid-Open No. 60-156 discloses a method for manufacturing such a display.
The method exemplified in Japanese Patent Publication No. 004 is known. In this method, minute interference fringes (diffraction gratings) due to two-beam interference of laser light are sequentially exposed on a photosensitive film while changing its pitch, direction, and light intensity.

On the other hand, an XY stage on which a planar substrate is mounted is moved by using an electron beam exposure apparatus instead of a laser and by computer control, so that a plurality of minute A method of manufacturing a display on which a diffraction grating pattern is formed by arranging various dots has been proposed. The above method is disclosed in JP-A-2-72320 and U.S. Pat. No. 5,058,992. According to the method using an electron beam,
Since the diffraction grating (lattice fringes) is directly drawn, the degree of freedom of the pattern to be produced is greatly improved, for example, the grating interval can be changed arbitrarily, and the diffraction grating can be a curved grating as well as a straight line.

As a typical example of the improvement of the degree of freedom of a pattern,
One example is that a pattern can be displayed three-dimensionally. In three-dimensional display, depending on the viewing direction,
You need to change the pattern that you see. For example,
When the same subject is viewed from different directions (left / front / right), the images of the different subjects are visually recognized, and the observer feels three-dimensionally.

The following are known as proposals relating to three-dimensional display using a diffraction grating pattern. (1) JP-A-3-206401 Regarding a plurality of two-dimensional images obtained by observing a subject from a plurality of directions, each is decomposed into dot units, and dots formed by a diffraction grating having a direction corresponding to the observation direction are used. 2
A two-dimensional image is drawn as a diffraction grating pattern, and diffraction grating patterns are formed on the same substrate by the number of two-dimensional images.

(2) Japanese Patent Application Laid-Open No. 5-2148 The diffraction grating pattern corresponding to a two-dimensional image is constituted by a linear diffraction grating, and the direction of the grating changes sequentially for each of a plurality of directions to be observed. In such a case, the display pattern does not change smoothly as the observer moves the viewpoint. This phenomenon is called "image jump". In order to eliminate image skipping, the diffraction grating is composed of a curve (more specifically, a set of a plurality of lines obtained by translating the same curve in parallel), and the change in the slope of the curve and the pitch at which the curve moves according to the observation conditions. It is this (2) that changes.

By the way, there is no report to date on a proposal for coexistence of a three-dimensional pattern and a two-dimensional pattern in a diffraction grating pattern having cells (dots) as constituent units in the same region on the same substrate. .

[0008] The three-dimensional pattern is not an existing rainbow hologram or holographic stereogram but a cell (dot) as a constituent unit on a substrate on which these are recorded. A method of overwriting (multiple exposure) the planar diffraction grating pattern described above is considered.

However, in the above method, a part where the three-dimensional pattern and the two-dimensional pattern overlap and a part where the three-dimensional pattern does not overlap are mixed, so that the diffraction efficiency (brightness) becomes uneven as a whole, and In the overlapping portions, interference fringes of a three-dimensional pattern serving as a base are crushed, which is bad for recognizing each pattern as being complete.

[0010]

SUMMARY OF THE INVENTION The present invention provides a pattern in which the diffraction efficiency (brightness) of the entire pattern has no unevenness and the three-dimensional pattern and the two-dimensional pattern can be recognized as perfect. It is intended to provide a diffraction grating pattern in which a three-dimensional pattern and a two-dimensional pattern each having a cell (dot) as a constituent unit coexist in the same region on the same substrate. is there. Note that “cell” and “dot”, which are constituent units of the pattern, are treated as synonyms.
The following description is unified by the term "cell" with a nuance that is not restricted by size.

[0011]

According to a first aspect of the present invention, there is provided a diffraction grating pattern comprising a plurality of minute cells formed of a diffraction grating arranged on a surface of a substrate. In a pattern in which at least one of the direction and the arrangement of each cell is changed, a two-dimensional pattern (A) composed of a group of minute cells composed of a linear diffraction grating and a minute pattern composed of a curved diffraction grating And a three-dimensional pattern (B) constituted by a group of unique cells coexists in the same region of the same substrate.

[0012] Claim 2 is a three-dimensional pattern (B).
Is to synthesize a plurality of two-dimensional patterns each composed of a collection of minute cells formed by a diffraction grating having a curved line corresponding to a display direction, each of a plurality of two-dimensional images having parallax. 2. A diffraction grating pattern according to claim 1, wherein:

A third aspect of the present invention is the diffraction grating pattern according to the first or second aspect, wherein an interval between adjacent cells is 300 μm or less. The above interval is
This corresponds to all the intervals between the cells constituting the pattern (A) and the cells constituting the pattern (B), the intervals between the cells constituting the pattern (A), and the intervals between the cells constituting the pattern (B). .

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1. Production of Three-Dimensional Pattern (B) FIG. 1 is an explanatory diagram showing a process of obtaining a plurality of two-dimensional patterns which are the basis of the three-dimensional pattern (B).

A plane image 80 of an object 85 to be displayed three-dimensionally
Is photographed using the television camera 81. That is, the television cameras 81 are arranged at a plurality of positions defined by the interval p, and photograph a plurality of planar images 80 of the object 85 corresponding to each position. In shooting, a plurality of TV cameras may be used for simultaneous shooting, or one TV camera may be moved for shooting.

The data of the plurality of obtained planar images 80 is input to a computer 82 using a digitizer 83 and stored as image data. Incidentally, the form of these planar images 80 may be data recorded on a video tape or photographic data. Further, the object 85 to be displayed three-dimensionally is not limited to an existing object,
It may be a virtual object by graphics.

Next, a method of determining the direction Ω of the diffraction grating and the pitch d of the diffraction grating when converting the plane image 80 into a diffraction grating pattern will be described.

It is assumed that an observer observes a pattern 15 having a diffraction grating cell 16 as shown in FIG. The incident angle of the illumination light 91 is θ, and 1 is reflected and diffracted by the diffraction grating.
Assuming that the direction of the second-order diffracted light 92 is α and the wavelength of the first-order diffracted light 92 is λ, the direction Ω of the diffraction grating 18 and the pitch d (reciprocal of the spatial frequency) of the diffraction grating 18 are as follows, as shown in FIG. Can be calculated by the following equation. The illumination light 91 is Y-
It is assumed that the light passes through the Z plane and that the diffracted light passes through the XZ plane.

Tan (Ω) = sin (α) / sin (θ) d = λ / {sin ² (α) / sin ² (θ)} ^1/2 By using the above equation, the illumination light 91 can be arbitrarily set. The direction Ω and the pitch d of the diffraction grating 18 for diffracting in the direction can be obtained. That is, the incident angle θ of the illumination light 91, the direction α of the first-order diffracted light 92, the first-order diffracted light 92
Is given, the direction Ω and the pitch d of the diffraction grating 18 can be obtained.

Here, a pitch d 'of the diffraction grating that diffracts to the front (α = 0) is obtained. d ′ = λ / sin (θ) Therefore, d = d′ sin (θ) / {sin ² (α) / sin ² (θ)} ^1/2 = d′ cos (Ω)

As shown in FIG. 4, in a configuration in which the curve is translated at a constant pitch, the above equation is always satisfied.
The diffraction grating is configured such that the wavelength of the same color can always be observed from the viewpoint where the diffracted light moves in the horizontal direction. FIG.
In the cell No., the curve constituting the cell changes from the slope Ω1 to Ω2, and the curves are arranged at the pitch d ′. That is, in order to obtain a cell of a diffraction grating in which the range of diffracted light in the horizontal direction is at an angle α1 to α2 with respect to the normal to the plane on which the diffraction grating is present, tan (Ω1) = sin (Α1) / sin (θ) tan (Ω2) = sin (α2) / sin (θ) d = λ / sin (θ) Therefore, a diffraction grating in which a curve that changes from the slope Ω1 to Ω2 is translated at a pitch d ′ may be used.

Therefore, the basic structure of a diffraction grating cell forming a three-dimensional pattern is as shown in FIG.

Next, as shown in FIG. 5, the cell is divided into three in the vertical direction. Then, the three divided areas are defined as r1, r2, and r3 from the left. Light incident on the portion r1 is diffracted leftward, light incident on the portion r2 is diffracted frontward, and light incident on the portion r3 is diffracted rightward. The number of areas that divide one cell is
The division is not limited to three as described above, but is performed by the number of two-dimensional images having parallax.

Here, if it is desired that this cell can be observed by illuminating only from the left direction, a diffraction grating should be drawn only for r1 and nothing should be drawn for r2 and r3. . In that case, the observer will see this cell shining only when the viewpoint is in the range of e1.

Assume that three two-dimensional images having parallax have been photographed for a certain three-dimensional object by the procedure described with reference to FIG. For example, this object is "T",
Assume that it looks like "O" when viewed from the front and "P" when viewed from the right. (There is no such object in reality)

Since there are three two-dimensional images having parallaxes to be used, the cells constituting the diffraction grating pattern are divided into three in the vertical direction. As shown in FIG. 6, "T" is the left part of the cell,
“O” represents the central part of the cell, and “P” represents the diffraction grating on the right part of the cell, whereby a three-dimensional diffraction grating pattern can be obtained.

The above diffraction grating pattern is reproduced as shown in FIG. At this time, "T" can be observed in the left direction, "O" in the front direction, and "P" in the right direction.

In the above description, there are three two-dimensional images having the input parallax. However, by using more parallax images, it is possible to make the images entering the left and right eyes of the observer different. it can. That is, the observer sees images having parallax separately for the left and right eyes, and feels three-dimensionally (three-dimensionally). Even if the observer's observation position is moved in the horizontal direction, a pair of images having parallax as viewed from other directions will be seen, and a natural stereoscopic effect will be obtained.

The above is a description of the production of a three-dimensional diffraction grating pattern.
By forming a planar (two-dimensional) diffraction grating pattern in a region where the diffraction gratings constituting “O” and “P” are not drawn, the diffraction grating pattern of the present invention is obtained.

Production of Two-Dimensional Pattern (A) A planar (two-dimensional) diffraction grating pattern is a single two-dimensional image having no parallax.
Unlike a cell in a two-dimensional image that forms a three-dimensional diffraction grating pattern, it is not necessary to be configured by a curved diffraction grating.

Examples of the two-dimensional pattern include a geometric fine print pattern, a logo, characters, symbols, and the like.

The direction of the diffraction grating constituting the above pattern
The pitch and the shape of the cells do not all need to be the same, and the direction of the diffraction grating is sequentially changed for each adjacent cell to provide a dynamic visual effect such that diffracted light appears to move as the viewpoint moves. It is also possible.

FIG. 8 is a local (microscopic) illustration of an example of a diffraction grating pattern in which a three-dimensional diffraction grating pattern and a two-dimensional diffraction grating pattern coexist in the same region on the same substrate. is there. Around a cell 13 consisting of a curved grating constituting a three-dimensional diffraction grating pattern, a cell 12 consisting of a straight grating constituting a planar diffraction grating pattern is provided.
Are arranged.

When setting the size of the cells constituting the diffraction grating pattern and the arrangement interval between the cells, the following consideration is made.

In determining the size of a cell that is difficult to identify with the naked eye, for example, a person with an eyesight of 0.7
Consider the case where a pattern is viewed at a distance of cm.
The resolution of a human eye with a visual acuity of 0.7 is 1.4 minutes = (1.4 / 6
0) °, two points 70 cm apart and 300 μm or more apart.

Therefore, when the diffraction grating pattern is viewed at a distance of 70 cm, the presence of a cell having a size of 300 μm square or less, including its shape, cannot be recognized by itself. Therefore, if the cells constituting the pattern (A) and the cells constituting the pattern (B) are adjacent to each other at an interval of 300 μm or less, they cannot be recognized separately. The patterns will appear to overlap. Therefore, to give the observer the impression that the pattern changes continuously and smoothly,
It is effective to set the cell interval and size to 300 μm square or less.

The case where a person with better visual aptitude comes closer to view the pattern than in the above case will be considered below. (1) The resolution of a human eye with a visual acuity of 1.0 is 1.0 minute = (1.0
/ 60) °, 50 cm apart, 150 μm or more 2
Points can be identified. (2) The resolution of a human eye with a visual acuity of 1.5 is 0.66 minutes = (0.
66/60) °, 30 cm apart, 58 μm or more 2
Points can be identified.

From the above, in case (1), it can be identified that there is a gap of 150 μm or more between adjacent cells.
In (2), it is possible to identify that there is a gap of 58 μm or more between adjacent cells. Therefore, the interval (gap) between adjacent cells in the pattern is set to (150 μm).
m, 58 μm) or less, the pattern is viewed as continuously and smoothly changing, and the cells are viewed as a bright pattern that is spread without gaps. A finer pattern can be produced as the cell interval and size are made smaller, but the above conditions are appropriate in consideration of an increase in the production time and the amount of processing data.

[0039]

According to the present invention, a three-dimensional pattern and a two-dimensional pattern are
Since there is no unevenness in the overall brightness and each can be viewed as perfect, various expressions with high eye catching effect are realized, and when used for security purposes,
Forgery and imitation are more difficult.

That is, in the present invention, it is necessary to accurately arrange cells constituting each of the three-dimensional pattern and the two-dimensional pattern, and it is very difficult to produce an original pattern. Countermeasures against counterfeiting and counterfeiting are improved as compared with a pattern using only a target pattern.

Further, as compared with the case where the three-dimensional pattern and the two-dimensional pattern are synthesized by the existing method, since there is no unevenness in the brightness (diffraction efficiency) due to the presence or absence of the overlapping portion, the authenticity determination is not performed. In addition to being easy, all cells constituting both the three-dimensional pattern and the two-dimensional pattern are formed (drawn) without overlapping, so that the three-dimensional pattern or the And / or a planar pattern is recognized, producing a unique decorative effect.

[0042]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a process of obtaining a plurality of two-dimensional patterns which are a basis for forming a three-dimensional pattern.

FIG. 2 is an explanatory diagram showing a state in which a pattern having a diffraction grating cell is observed.

FIG. 3 shows a direction Ω and a pitch d of a diffraction grating formed in a cell.
Explanatory drawing which shows (the reciprocal of a spatial frequency).

FIG. 4 is an explanatory view showing an example of a cell composed of a diffraction grating having a curved line constituting a three-dimensional pattern.

FIG. 5 is an explanatory diagram showing a relationship between a divided region and a direction of emission of diffracted light in a cell including a diffraction grating having a curved line constituting a three-dimensional pattern.

FIG. 6 is a diagram illustrating a case where a diffraction grating is formed as a pixel that constitutes “T” in the left part of the cell, “O” in the center part, and “P” in the right part, and synthesizes an original image having parallax on the same substrate Explanatory drawing which shows a concept.

FIG. 7 is an explanatory diagram showing a state in which the diffraction grating pattern of FIG. 6 is observed.

FIG. 8 is an explanatory diagram showing an example of a cell arrangement for an example of a diffraction grating pattern in which a three-dimensional diffraction grating pattern and a two-dimensional diffraction grating pattern coexist in the same region on the same substrate.

[Explanation of symbols]

12: a cell composed of curved lattices constituting a planar diffraction grating pattern 13: a cell composed of curved lattices constituting a three-dimensional diffraction grating pattern 14, 15, a substrate (pattern) 16: a diffraction cell 18: diffraction Grating 91 ... Illumination light 92 ... First order diffracted light

Claims (3)

[Claims] A plurality of minute cells comprising a diffraction grating arranged on a surface of a substrate;
In a pattern in which at least one of the direction of the diffraction grating and the arrangement of the cells is changed, a two-dimensional pattern (A) composed of a collection of minute cells composed of linear diffraction gratings and a curved diffraction grating A three-dimensional pattern (B) constituted by a collection of minute cells made of a coexistence in the same region of the same substrate. 2. A three-dimensional pattern (B) comprising: a plurality of two-dimensional images each having a parallax formed by a group of minute cells formed by a diffraction grating having a curve corresponding to a display direction. 2. The diffraction grating pattern according to claim 1, wherein said two-dimensional pattern is synthesized. 3. An interval between adjacent cells is 300 μm.
The diffraction grating pattern according to claim 1, wherein m is equal to or less than m.