JP2000329919A - Diffraction grating pattern and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a brighter image without losing the relation of brightness values of the pixels for the base image data by increasing the total brightness while maintaining the brightness ratio in the pixel units in the pattern to be displayed. SOLUTION: The whole brightness of the pattern is increased while the brightness ratio of pixel units in the pattern to be displayed is maintained. Namely, if the brightest cell in the diffraction grating cell formed has the diffraction grating by 80% of the max. area of the cell, the cell is enlarged into an area by 1.25 times (80×1.25=100) so that the cell can be transformed into a bright cell with the diffraction grating possessing the whole region of the cell, In order to maintain the brightness ratio in the pixel units of the pattern to be displayed, the region where the diffraction gratings are formed is enlarged into an area by 1.25 times. Thus, the whole brightness of the diffraction grating pattern can be improved without losing the relation of the brightness of the original data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern expressed by arranging minute cells (dots) made of a diffraction grating on a surface of a substrate, and a method of manufacturing the same.
In particular, the present invention relates to a pattern with higher lightness / saturation and a higher gaze rate, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Since a pattern formed by a diffraction grating has a directional luster that cannot be expressed by ordinary printing techniques, it is widely used for display applications and security products aimed at preventing forgery. Therefore, it is required to produce a more versatile and highly original pattern.

In response to such demands, cells (dots)
2. Description of the Related Art Displays having a diffraction grating pattern constituted by a collection of diffraction gratings are known. A cell (dot) on which a diffraction grating is formed is referred to as a diffraction grating cell in the following description.

[0004] As a method for producing the above display, a method as exemplified in JP-A-60-156004 is known. According to this method, minute interference fringes (diffraction gratings) due to two-beam interference of laser light are formed at the pitch,
The photosensitive film is successively exposed by changing the direction and the light intensity.

On the other hand, using an electron beam exposure apparatus instead of a laser, and moving the XY stage on which a planar substrate is mounted by computer control, a plurality of minute A method of producing a display on which a diffraction grating pattern is formed by arranging various dots has also been proposed. The above method is disclosed in JP-A-2-72320 and U.S. Pat. No. 5,058,992.

The parameters of the diffraction grating pattern include: (1) the spatial frequency of the diffraction grating (pitch of the grating fringes); (2) the direction of the grating (the direction of the grating fringes); and (3) the drawing area of the diffraction grating (the arrangement of the grating cells). According to (1), the color in which the diffraction grating cell shines with respect to a fixed point changes according to (1), and according to (2), the direction in which the diffraction grating cell shines changes, and ( The display pattern (picture) is determined according to 3).

[0007] Note that "cell" and "dot" which are constituent units of a display (pattern) are treated as synonyms, but a nuanced term "cell" which is not restricted by shape (outline) or size, and The product will be referred to as a “diffraction grating pattern”, and the following description will be unified.

By the way, in such a diffraction grating pattern, since a cell serving as a pixel is constituted by a diffraction grating, light is diffracted in an arbitrary direction and color and an image is perceived, so that the diffraction grating is drawn on the pattern. If there is an area that is not
Since the amount of light to be diffracted is reduced, sufficient brightness cannot be expressed, and a high gaze effect cannot be obtained.

In order to make the pattern brighter, the cells (dots), which are the constituent units of the pattern, may have a larger area.

In order to express the luminance of each pixel by the diffraction grating pattern, it is effective to change the cell area in proportion to the luminance value (brightness). That is, if the cell having the largest area corresponds to the color having the brightest luminance value,
For darker colors, only cells of smaller area than cells used for the lightest color will always be used.

As a proposal for changing the size of a cell (dot) constituting a diffraction grating pattern to a designated size in accordance with the brightness of the cell, Japanese Patent Application Laid-Open No. 3-39701 by the present applicant has been proposed.
Is known.

[0012] The proposal according to the above publication is effective in producing a pattern in which each cell (dot) can be arranged at an arbitrary position and an arbitrary area on a substrate. In order to achieve high speed, the area where the diffraction grating is to be formed on the substrate is defined in a matrix in advance, and it is effective to arrange the cells by forming the diffraction grating in each area. It is. Therefore, the proposal in the above publication is not necessarily appropriate for producing a pattern by digital processing.

[0013]

When the data on which the diffraction grating pattern is based is image data having many gradation colors obtained by computer graphics, scanners, digital cameras, etc. Not only is digital processing suitable for fabrication, but most of the pixels that make up the image data do not require cells with the largest area, so diffraction gratings are drawn on the fabricated diffraction grating pattern. There are many non-existent regions, and those portions do not contribute to the generation of diffracted light, and therefore, it is unavoidable that the image is originally darker than the image to be expressed by the diffraction grating pattern.

The present invention provides a diffraction grating pattern comprising:
It is an object of the present invention to provide a diffraction grating pattern capable of expressing a brighter image without deteriorating the magnitude relationship between the luminance values of the pixels of the original image data (particularly, digital data), and a method of manufacturing the same.

[0015]

According to the present invention, in the case where even the cell having the highest luminance has a portion where the diffraction grating is not drawn, the area of each cell is made as large as possible to produce a diffraction grating pattern. This achieves the above object.

The diffraction grating pattern according to the first aspect of the present invention is constituted by arranging a plurality of minute cells made of a diffraction grating on the surface of a substrate, and at least the spatial frequency of the diffraction grating, the direction of the diffraction grating, and the drawing area of the diffraction grating. In a pattern in which any of the patterns is changed, the overall luminance is improved while maintaining a luminance ratio in a pixel unit in a pattern to be expressed.

The diffraction grating pattern according to the second aspect of the present invention is constituted by arranging a plurality of minute cells made of a diffraction grating on a substrate surface, and at least the spatial frequency of the diffraction grating, the direction of the diffraction grating, and the drawing area of the diffraction grating. In a pattern in which any of the patterns change, the arrangement location of the region where the diffraction grating is formed and the area of each region are determined in advance so as to constitute the pattern, and the maximum brightness in the configured pattern is obtained. In the cell to be expressed, the entire area of the region is occupied by the diffraction grating, and in other cells constituting the pattern, the area occupied by the diffraction grating in each region is expanded. And

The diffraction grating pattern according to the third aspect of the present invention is constituted by arranging a plurality of minute cells made of a diffraction grating on the surface of a substrate. In a pattern in which any of them is changed, the arrangement location of the region where the diffraction grating is formed and the area of each region are determined in advance so as to form the pattern, and various types (spaces) are included in each region (cell). (Frequency, direction), even in the case where diffraction gratings are mixed, the cell which can diffract light most in the formed pattern occupies the entire area of the region by the diffraction grating. Is characterized in that the area occupied by the diffraction grating in each of the cells is expanded in each of the other cells.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a diffraction grating pattern, comprising the steps of: obtaining a maximum value from each pixel of image data which constitutes a diffraction grating pattern, obtained by computer graphics, a scanner, a digital camera, or the like. Extracting luminance data of a pixel having brightness; calculating, from the data, an area of a region where no diffraction grating exists in each cell where the diffraction grating is formed; and The area of the cell having the smallest value is set to 0, the area where the diffraction grating is drawn is expanded, and the area where the diffraction grating is drawn is increased at the same ratio for the other cells; Newly determining the outer shape of a region (cell) in which a pattern is to be drawn. While it is drawn in, characterized by arranging a plurality of cells comprising a diffraction grating on the substrate surface.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram illustrating an example of an optical system that forms a diffraction grating cell. As described above, there are two typical methods for forming a diffraction grating cell: exposure formation by two-beam interference method and formation by electron beam (EB) drawing. FIG. 1A shows the two-beam interference method. 1 (b)
Is an explanatory diagram showing an electron beam (EB) drawing method.

In the two-beam interference method using laser light, a mask provided with an opening having an area corresponding to a desired brightness is installed immediately before the two-beam laser interferes with the photosensitive material surface.
The luminance value of the cell is determined by defining the exposure area by the laser beam. (FIG. 1 (a)) There is also a method in which the cell area is all the same without using a mask, and the brightness value of the cell is determined by increasing or decreasing the exposure time in each cell. As described in 39701,
Due to the intensity distribution of the laser beam (Gaussian distribution = high intensity at the center), it is difficult to appropriately set the change in diffraction efficiency (luminance) for each cell.

On the other hand, in the electron beam (EB) drawing method, it is easy to determine the luminance value of a cell by drawing a diffraction grating inside an area unique to each cell corresponding to the luminance value. (Figure 1
(b))

A diffraction grating pattern produced by such a drawing method is a set of diffraction grating cells as shown in FIG. FIG. 1 is an explanatory diagram relating to an example of a pattern configured by arranging diffraction grating cells in a 3 × 3 matrix.

The numerical value described on the cell is 100 when the diffraction grating is drawn on the entire maximum area of the cell, and is a numerical value proportional to the brightness (area of drawing the diffraction grating). The value of the area of the cell where the diffraction grating is not drawn is zero.

Here, as shown in FIG. 2A, when at least one cell having the brightness of 100 (upper left) exists in the diffraction grating pattern, the area of all the cells is uniformly increased. However, the brightness of the entire pattern cannot be improved (because the brightness ratio of each pixel in the pattern to be expressed is not maintained). However, as shown in FIG. If there are not 100 cells, the expansion of the grating cell according to the invention takes place.

In FIG. 2B, the brightest cell among the formed diffraction grating cells has a maximum area of 80%.
% (On the center) with a diffraction grating formed. By making this cell 1.25 times the area (80 × 1.25 = 100), it can be converted into a bright cell in which the entire cell area is occupied by the diffraction grating. Similarly, in order to maintain the luminance ratio of the pixel unit in the pattern to be expressed, in other cells, the area where the diffraction grating is formed is expanded to 1.25 times the area, so that the relationship between the brightness of the original data and The brightness of the entire diffraction grating pattern to be produced can be improved without any loss.

In producing a full-color diffraction grating pattern based on a two-dimensional image, a method of dividing one cell into red, green, and blue regions is generally used as a method for naturally expressing the color of the original image. It is being done.

By using this method, it is possible to faithfully represent colors (such as white and intermediate colors) that cannot be represented by a specific single wavelength. Thus, even if one cell is divided into several smaller cells (sub-cells), the luminance value of the cell is (red, green, blue) = (100,
If there is no cell (100, 100), the area where the diffraction grating is formed in the cell can be extended, and the brightness can be improved.

FIG. 3 is an explanatory diagram showing the concept of expanding the formation area of the diffraction grating according to the present invention in the case where one cell is constituted by subcells. In the figure, 1
One cell is configured by being divided into red (R), green (G), and blue (G) subcells.

For example, as shown in a photographed image of a flame, a red (R)
Is very high and the luminance values of green (G) and blue (G) are low, and conversely, if the component of red (R) is small like a forest image, red, green, There is a large bias in the distribution of blue luminance values. Therefore, the luminance value of a specific sub-cell (red in the image of the flame) can be designated as an amount that cannot be expressed at the stage of the original data (that is, a value exceeding 100). FIG. 3 shows the concept of converting original data (upper) for a flame image into a diffraction grating pattern (lower).

Similarly, when producing a three-dimensional diffraction grating pattern composed of a plurality of two-dimensional images having parallax, one cell is divided into sub-cells corresponding to the number of the two-dimensional images. Therefore, a diffraction grating can be efficiently formed even in a region where no diffraction grating is formed in the cell in the original data.

As a proposal relating to a three-dimensional diffraction grating pattern for providing a three-dimensional display, Japanese Patent Application Laid-Open No. Hei.
Japanese Patent Application Laid-Open No. 06401 and Japanese Patent Application Laid-Open No. 5-2148 are publicly known, and the outline is described below.

In a three-dimensional display, it is necessary to change the pattern to be viewed according to the viewing direction. For example, when the same subject is viewed from different directions (left / front / right), the images of the different subjects are visually observed, and the observer feels three-dimensionally.

In Japanese Patent Application Laid-Open No. Hei 3-206401, a plurality of two-dimensional images obtained by observing a subject from a plurality of directions are decomposed into dot units, and dots formed by a diffraction grating having a direction corresponding to the observation direction. Draws a two-dimensional image as a diffraction grating pattern on the same substrate.
The diffraction grating patterns are formed for the number of the two-dimensional images.

In Japanese Patent Application Laid-Open No. 5-2148, a diffraction grating pattern corresponding to a two-dimensional image is formed 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. Change.

FIG. 4 shows a three-dimensional diffraction grating pattern formed by combining four two-dimensional images having parallax.
It is explanatory drawing which shows the concept which applies this invention. One cell is divided into four subcells each, and the base data (top)
In this case, the area where the diffraction grating is formed can be extended (below) to the area where the diffraction grating is not formed in the cell.

FIG. 5 shows an example of a procedure for expanding a region where a diffraction grating is formed in a case where one cell is divided into a plurality of subcells as described above.

First, in step a, luminance information of all pixels is read from image data such as computer graphics, and a pixel having the maximum brightness is selected.

Assuming that the area of each of the (R, G, B) subcells obtained in step a is (r, g, b) and the area of a cell on which a diffraction grating can be formed (drawn) is S, The area ratio of the area where the diffraction grating is drawn in the cell is ((r + g + b) / S) * 100 (%). If this value is not 100%, the area of ((S− (r + g + b)) / S) * 100 (%) is the area where the diffraction grating is not drawn.

Therefore, it is determined that the drawing area of each of the R, G, and B elements can be expanded as described below. (Step b) R; ((S- (r + g + b)) * r) / (S * (r + g + b)) * 100 (%) G; ((S- (r + g + b)) * g) / (S * (r + g + b)) ) * 100 (%) B; ((S− (r + g + b)) * b) / (S * (r + g + b)) * 100 (%)

In step c, taking into account the expanded portion,
Determine the outer shape of each subcell. If the area of the area where the diffraction grating is drawn is correct, the outer shape of the area where the diffraction grating is drawn in each subcell does not matter, and the subcell can take any shape. As shown in FIG. 6, it is also possible to draw a grid that is extended so as to be added to each subcell by the conventional method (top), and to arrange subcells having the same area and completely different shapes inside the cell. In addition, the effect of the present invention is attributable to the area of the region where the diffraction grating is expanded, and does not depend on the outer shape of the region.

In step d, the diffraction grating of each cell determined by the above process is drawn to complete a diffraction grating pattern.

[0043]

As described above, the diffraction grating pattern of the present invention has the following effects because the drawing area of the diffraction grating is expanded in each cell. (1) By expanding the drawing area of the diffraction grating, the area of the pattern surface that contributes to the diffraction of light increases, so that a brighter pattern than before can be obtained, and high gaze power can be expected. (2) A case where each cell constituting the pattern is divided into sub-cells of three colors of R, G and B, or a case where each cell is composed of sub-cells of the number of a plurality of two-dimensional images having parallax. However, for subcells within the same cell, an area where a diffraction grating is not drawn can be used effectively, and a luminance value that cannot be expressed at the stage of original data can be expressed (more than 100). Increase). (3) By extending the drawing area of the diffraction grating, a change in gradation can be expressed more clearly. Therefore, it is expected that the effect of the color scheme, such as expressing the contrast strongly or expressing the gradation smoothly, will appear more clearly. (4) Even with a diffraction grating pattern having a small area, a bright pattern can be obtained, so that a gaze effect not inferior to a diffraction grating pattern having a large area can be expected.

[0044]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of an optical system for forming a diffraction grating cell. FIG. 1 (a) is an explanatory view showing a two-beam interference method, and FIG. 1 (b) is an explanatory view showing an electron beam (EB) drawing method.

FIG. 2 is an explanatory view showing an example of a pattern formed by arranging diffraction grating cells in a matrix. FIG. 2 (a) shows a pattern to which the area expansion of the diffraction grating according to the present invention cannot be applied, and FIG. FIG. 2B is an explanatory diagram of a pattern before the area expansion of the diffraction grating according to the present invention is applied, and FIG.

FIG. 3 is an explanatory diagram showing a concept of expanding a formation region of a diffraction grating according to the present invention in a case where one cell is constituted by subcells.

FIG. 4 is an explanatory diagram showing a concept of expanding a formation region of a diffraction grating according to the present invention in another case (a three-dimensional display using a three-dimensional diffraction grating pattern) in which one cell is configured by a subcell.

FIG. 5 is a flowchart showing an example of a procedure for a method of manufacturing a diffraction grating pattern (expansion of a diffraction grating area) according to the present invention.

FIG. 6 is an explanatory diagram showing an example of expansion of a formation region of a diffraction grating according to the present invention.

Claims (4)

[Claims] 1. A pattern in which at least one of a spatial frequency of a diffraction grating, a direction of a diffraction grating, and a drawing area of the diffraction grating is changed, wherein a plurality of minute cells made of a diffraction grating are arranged on a substrate surface. A diffraction grating pattern having a configuration in which the overall luminance is improved while maintaining the luminance ratio of each pixel in a pattern to be expressed. 2. A pattern in which at least one of a spatial frequency of the diffraction grating, a direction of the diffraction grating, and a drawing area of the diffraction grating is changed, wherein a plurality of minute cells formed of the diffraction grating are arranged on the substrate surface. The location of the area where the diffraction grating is formed to form the pattern and the area of each area are predetermined, and the cell to be expressed with the maximum brightness in the configured pattern is: A diffraction grating pattern, wherein the entire area of the region is occupied by the diffraction grating, and the area occupied by the diffraction grating in each of the other cells constituting the pattern is expanded. 3. A pattern in which at least one of a spatial frequency of the diffraction grating, a direction of the diffraction grating, and a drawing area of the diffraction grating is changed, wherein a plurality of minute cells formed of the diffraction grating are arranged on the substrate surface. The location of the area where the diffraction grating is formed and the area of each area are determined in advance so as to form a pattern. Diffraction gratings of various types (spatial frequency, direction) are mixed in each area (cell). Even in such a case, the cell that can diffract light the most in the configured pattern has the diffraction grating occupying the entire area of the region, and the other cells constituting the pattern also have A diffraction grating pattern characterized in that the area occupied by the diffraction grating in the region is expanded. 4. A step of extracting luminance data of a pixel having the maximum brightness from each pixel of image data serving as a basis for forming a diffraction grating pattern obtained by computer graphics, a scanner, a digital camera, or the like. Calculating the area of the region where the diffraction grating does not exist in each cell where the diffraction grating is formed from the data; and setting the area of the cell where the area where the diffraction grating does not exist to be smallest to 0 as 0 Expanding the area where the diffraction grating is drawn and increasing the area where the diffraction grating is drawn at the same ratio for the other cells, and adding a new shape to the area where the diffraction grating is drawn (cell). And determining based on the above steps,
A method for producing a diffraction grating pattern, comprising arranging a plurality of cells made of a diffraction grating on a substrate surface while drawing the diffraction grating for each region.