JP2008145669A - Volume hologram, method for manufacturing the same and hologram display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a volume hologram having a figure recorded, in which a region close to the edge of a figure portion having uniform brightness does not appear brighter than other portion but appears in the same brightness as other region in the figure. <P>SOLUTION: A pattern image 1 including figures 11, 12 is recorded in a transmissive or reflective volume hologram, in which the pattern image 1 recorded comprises a bright figure recorded in a relatively dark background and a gradation zone 13 disposed along the rim of the figure, the zone where the brightness gradually changes from a level equal to the brightness of the background outside the figure edge to a level equal to the brightness inside the figure, in a direction from the edge of the figure to the inside of the figure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a volume hologram, a method for producing the same, and a hologram display device using the same, and more particularly to a volume hologram in which an edge of a recorded figure is inconspicuous, a method for producing the same, and a display device using the same.

  In a hologram in which a figure is recorded as an image hologram, there is a problem that, for example, in the figure portion having uniform brightness, the diffraction efficiency is substantially uniform in the figure, but the vicinity of the edge of the figure is bright and conspicuous. This phenomenon is due to a visual action called edge contrast (Non-Patent Document 1).

In order to make the vicinity of an edge in a figure have the same brightness as the area in the other figure, it is necessary to suppress the brightness in the vicinity of the edge. As a method for adjusting the brightness of the hologram, it is common to control the diffraction efficiency by adjusting the film thickness of the photosensitive material, the exposure amount, and the exposure ratio. However, changing the brightness of the uniform graphic portion of the hologram recorded on the same photosensitive material for each region is because the film thickness is constant and the diffraction efficiency is controlled by adjusting the exposure amount and exposure ratio. It is difficult to do.
JP 2005-115225 A Japanese Patent Publication No. 7-82289 Yoshio Oi and one other author, “Introduction to Color Coordinator Color” (Japan Color Research Co., Ltd., January 30, 1999, 1st edition issued) 32-33

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to make the vicinity of an edge of a volume hologram with a uniform brightness of a volume hologram on which a figure is recorded appear brighter than others. It is an object of the present invention to provide a volume hologram that looks the same brightness as other regions in the figure, a method for producing the same, and a display device using the same.

  In the volume hologram of the present invention that achieves the above object, a pattern image including a figure is recorded as a transmission or reflection type volume hologram, and the pattern image includes a bright figure in a relatively dark background. A gradation band is provided along the edge that is recorded and gradually changes in brightness from the edge of the figure part toward the inside of the figure, from the brightness of the background outside the edge to the brightness inside the figure. The pattern image is recorded.

  In this case, it is desirable that the gradation band is composed of a dot density pattern.

  Further, it is desirable that the pattern image is a planar image and is recorded as an image hologram.

The volume hologram creating method of the present invention is a method for creating a volume hologram in which a pattern image is recorded,
A bright figure is recorded in a relatively dark background, and the brightness gradually changes from the brightness of the background outside the edge to the brightness inside the figure from the edge of the figure to the inside of the figure. A pattern image in which gradation bands to be provided are provided along the edge thereof is prepared, and the pattern image is hologram-photographed as a transmission type or reflection type volume hologram.

  In this case, it is desirable that the gradation band is composed of a dot density pattern.

  Further, it is desirable that the pattern image is a flat image and is recorded as an image hologram.

The hologram display device of the present invention includes a light guide plate that irradiates reproduction illumination light, a volume hologram embedded in the light guide plate, and a light source disposed at at least one end of the light guide plate, and the volume hologram Is a hologram display device that is illuminated by illumination light guided by multiple reflection that repeats total reflection in the light guide plate,
In the volume hologram, a bright figure is recorded in a relatively dark background, and the brightness from the edge of the figure part toward the inside of the figure is changed from the brightness of the background outside the edge to the inside of the figure. A pattern image in which a gradation band gradually changing to brightness is provided along the edge is recorded.

Another hologram display device of the present invention includes a light guide plate that irradiates reproduction illumination light, a volume hologram disposed in an illumination light path emitted from one surface of the light guide plate, and at least one end of the light guide plate. The volume hologram is illuminated by illumination light emitted from one surface of the light guide plate,
In the volume hologram, a bright figure is recorded in a relatively dark background, and the brightness from the edge of the figure part toward the inside of the figure is changed from the brightness of the background outside the edge to the inside of the figure. A pattern image in which a gradation band gradually changing to brightness is provided along the edge is recorded.

  In these cases, it is desirable that the gradation band is composed of a dot density pattern.

  The pattern image is preferably a flat image and recorded as an image hologram.

  According to the present invention as described above, a volume hologram in which a portion of the figure of the volume hologram on which the figure is recorded has a uniform brightness and the vicinity of the edge does not look brighter than the others and the same brightness as the area in the other figure is obtained. Can be obtained.

  Below, the volume hologram of the present invention, a method for producing the same, and a display device using the same will be described based on the principle and description of the embodiments.

  The basic principle of the volume hologram of the present invention is that when a pattern image including a figure is recorded as a transmission or reflection type volume hologram, the pattern image is not recorded as it is, but at least a figure portion brighter than the background is recorded. In order to prevent the vicinities of the edges from appearing brightly and conspicuously, the brightness gradually changes from the edge of the bright figure part toward the inside of the figure, from the brightness of the background outside the edge to the brightness inside the figure. By providing a gradation image along the edge and creating a pattern image to be recorded on the volume hologram, the figure in the pattern image reproduced from the volume hologram on which the pattern image has been recorded looks almost uniform in brightness, and the edge It is to prevent a phenomenon in which the neighborhood appears bright and conspicuous (compared to the edge).

  FIG. 1 is an optical path diagram showing an example of an arrangement for photographing a volume hologram according to the present invention. For example, a pattern image 1 as shown in a plan view in FIG. 3 to be described later is arranged on the object plane of the projection optical system 3, and a photopolymer, a silver salt photosensitive material, or a holographic height is formed in the vicinity of the image plane of the pattern image 1. A volume hologram sensitive material 2 made of a molecular dispersion type liquid crystal element (Patent Document 1) is disposed. Then, the illumination light 5 illuminates the pattern image 1 from the back and transmits the light transmitted through the pattern image 1 as the object light 6 through the projection optical system 3 and enters the hologram sensitive material 2, and from the same laser light source as the illumination light 5 The reference light 7 is simultaneously incident on the hologram sensitive material 2 from the same side as the object light 6 at a predetermined incident angle θ and is caused to interfere in the hologram sensitive material 2 and photographed as a transmission hologram.

  Then, based on the present invention, as shown in FIG. 2, a volume hologram in which a pattern image 10 in which, for example, a bright square 11 and a letter “A” 12 are arranged in parallel on a dark background is photographed in an arrangement as shown in FIG. (Hereinafter denoted by reference numeral 2 '), the pattern image reproduced on the basis of the contrast between the edges of the square 11 and the bright part of the character "A" 12 is in the vicinity of the edge (edge). In order to prevent a phenomenon that looks relatively dark compared to the above, a pattern image 1 as shown in FIG. 3 is photographed as a volume hologram 2 ′ in the arrangement as shown in FIG.

  In the pattern image 1 of FIG. 3, the square 11 and the character “A” 12 to be reproduced and displayed are arranged in parallel on a dark background, but the dark image in the bright part of the square 11 and the character “A” 12 is displayed. A gradation band 13 that gradually changes from the brightness of the dark background to the brightness of the figures 11 and 12 is provided along the edge.

  In this way, the pattern image 1 provided with the gradation band 13 in which the brightness gradually changes along the edges (edges) in the bright figures 11 and 12 is formed on the volume hologram 2 ′ recorded in the arrangement as shown in FIG. A pattern image similar to the pattern image 1 of FIG. 3 is reproduced by applying reproduction illumination light of a predetermined wavelength, but the observer is prevented from the edge contrast phenomenon, and against a dark background as shown in FIG. For example, a pattern image 10 in which squares 11 and letters “A” 12 having bright and uniform brightness are arranged in parallel can be observed.

  By the way, as disclosed in Patent Document 2, the reproducibility of the gradation of the density change gradation image is not easy particularly in the image hologram. The gradation band 13 of the pattern image 1 in FIG. 3 is nothing but a density change gradation image. Therefore, it is not easy to record the volume hologram 2 'that accurately reproduces the gradation. If the volume hologram 2 ′ is not recorded as a hologram for accurately reproducing the gradation of the gradation band 13, a pattern in which squares 11 of uniform brightness and the letter “A” 12 are arranged in parallel as shown in FIG. The image 10 cannot always be observed.

  Therefore, instead of using the gradation band 13 of the density change gradation image as shown in FIG. 3 as the pattern image 1 to be recorded in the arrangement for photographing the volume hologram 2 ′ of FIG. 1, the density is expressed by the area ratio of the halftone dots. The gradation band 13 illustrated in FIG. 4 is provided along the edges in the graphics 11 and 12 of the pattern image 1. Also in this case, the area ratio of the halftone dots gradually changes from the brightness of the dark background to the brightness of the inside of the figures 11 and 12 along the edge (edge) with respect to the dark background in the bright part of the figures 11 and 12. A gradation band 13 expressing the density is provided.

  Here, the gradation band 13 expressing the density by the area ratio of the halftone dots is similar to the gradation band 13 of the density change gradation image, from the brightness of the background where the average density distribution is dark to the brightness inside the figures 11 and 12. The halftone dots are composed of figures such as fine opaque circles and rectangles that are difficult to resolve with the eye during observation, and the average is obtained by changing the area ratio. The concentration can be changed.

  1. A reproduction illumination light having a predetermined wavelength is applied to a volume hologram 2 ′ in which a pattern image 1 provided with a gradation band 13 composed of halftone dots that are difficult to be decomposed by such eyes is recorded in an arrangement as shown in FIG. Thus, a pattern image similar to the pattern image 1 in FIG. 4 is reproduced. However, since the halftone dots are difficult to disassemble with eyes during observation, the gradation band of the density change gradation image as shown in FIG. As in the case of using 13, the edge contrast phenomenon is prevented from being observed by the observer. For example, a square 11 and a letter “A” 12 having a bright and uniform brightness against a dark background as shown in FIG. Can be observed.

Here, a method of gradually decreasing the most inconspicuous density of the gradation band 13 will be described. That is, as shown in FIG. 5, when the density η is assumed to be a continuous function regarding the position x on the pattern image 1, the background portion of the pattern image 1 in which η takes a constant value η ₁ [x ₁ ≦ x ≦ x ₂ ]. When the x-axis positive direction is taken in the direction toward the internal position f where η of the figures 11 and 12 becomes a constant value η ₂ [η ₁ > η ₂ ] from (dη / dx), a <x <x ₂ In the case of ≦ 0 and at least in a certain range x ₂ ≦ b <x <c, (d ² η / dx ² ) <0 may be satisfied. At this time, when b <x <c, | dη / dx | is an increasing function of x. It should be noted that η is asymptotic to the minimum value η ₂ (≧ 0) [e ≦ x ≦ f], that is, in a certain range of x c <d <x <e ≦ f (d ² η / dx ² )> If it is 0, the method of convergence to η ₂ becomes smooth as shown in FIG. 5, and the edge contrast phenomenon becomes smaller. Here, C is the width of the gradation band 13.

  Here, the width C of the gradation band 13 is about 3 to 25% of the size in the direction orthogonal to the edges of the figures 11 and 12 on which the gradation band 13 is provided, and is 10 μm to 300 μm. It is desirable that the size be in the range of.

  Now, as described above, the volume hologram 2 ′ in which the pattern image 1 provided with the gradation band 13 that gradually changes from the brightness of the dark background to the brightness of the figures 11 and 12 is recorded as shown in FIG. A structural example of a display device capable of observing a pattern image is shown in a sectional view of FIG. The light guide plates 21 and 22 are closely arranged and integrated on both surfaces of the transmission type volume hologram 2 ′ photographed in the arrangement as shown in FIG. 1, and one end of the laminate, in the case of FIG. A hologram display device 20 is configured by arranging a light source 23 made of, for example, an LED to introduce reproduction illumination light having a predetermined wavelength into the light guide plate 21. In such a configuration, the illumination light 24 from the light source 23 introduced from one end of the light guide plate 21 is opposite to the surface of the light guide plate 21 opposite to the volume hologram 2 ′ and the volume hologram 2 ′ of the light guide plate 22. By the multiple reflection that repeats total reflection with the back surface on the side, the light source 23 is led from the end facing the light source 23 to the opposite end through the laminated body including the light guide plate 21, the volume hologram 2 ′, and the light guide plate 22. While the multi-layered reflection is made in the laminate, the volume hologram 2 ′ has a predetermined incident angle from the back side (the wavelength is the same as that of the reference light 7, and there is no shrinkage in post-processing such as development processing of the volume hologram photosensitive material 2. Then, the component incident at an angle equal to or near the incident angle θ of the reference light 7 is diffracted by the volume hologram 2 ′ as diffracted light 25 to the front of the laminate and recorded in the volume hologram 2 ′. The pattern image 1 is reproduced, and a pattern image as shown in FIG. 2 can be observed from the front of the hologram display device 20.

  FIG. 7 shows a cross-sectional view of a configuration example of another hologram display device 20. This configuration example uses a light guide plate as a backlight instead of embedding the volume hologram 2 ′ in the light guide plate and illuminating with the light guided in the light guide plate as shown in FIG. It is an arrangement to illuminate with light emitted from The volume hologram 2 ′ on which the pattern image 1 provided with the gradation band 13 that gradually changes from the brightness of the dark background to the brightness of the figures 11 and 12 is placed close to the illumination light exit side of the light guide plate 26. The illumination light 24 from the light source 23 having a predetermined wavelength is introduced from one end of the light guide plate 26. The light guide plate 26 is guided from the end on the light source 23 side of the light guide plate 26 to the opposite end by multiple reflection that repeats total reflection between the back surface and the surface on the volume hologram 2 ′ side. Alternatively, a reflector such as a fine prism surface or a scatterer is provided on the back surface, and the illumination light 24 guided by multiple reflection in the light guide plate 26 is emitted to the front side of the light guide plate 26, and the volume type therein If the hologram 2 ′ has a predetermined incident angle from the back side (the wavelength is the same as that of the reference light 7, and there is no contraction in post-processing such as development processing of the volume hologram sensitive material 2), it is equal to the incident angle θ of the reference light 7. The incident component at or near the angle) is diffracted by the volume hologram 2 ′ as diffracted light 25 to the front opposite to the light guide plate 26, and the pattern image 1 recorded on the volume hologram 2 ′ is reproduced. Front of display device 20 Pattern image such as al Figure 2 can be observed.

  As described above, the volume hologram of the present invention and the hologram display device using the volume hologram have been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible.

It is an optical path diagram which shows an example of the arrangement | positioning which image | photographs the volume hologram by this invention. It is a top view which shows the pattern image which is going to be displayed with the volume hologram of this invention. It is a top view which shows an example of the pattern image recorded on the volume hologram of this invention. It is a top view which shows the other example of the pattern image recorded on the volume hologram of this invention. It is a figure for demonstrating the gradual reduction method of the density | concentration of a gradation zone. It is sectional drawing which shows the structural example of the hologram display apparatus by this invention. It is sectional drawing which shows another structural example of the hologram display apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pattern image 2 ... Volume type hologram sensitive material 2 '... Volume type hologram 3 ... Projection optical system 5 ... Illumination light 6 ... Object light 7 ... Reference light 10 ... Pattern image 11 to reproduce | regenerate ... Square 12 ... Letter "A"
13 ... gradation band 20 ... hologram display device 21, 22 ... light guide plate 23 ... light source 24 ... illumination light 25 ... diffracted light 26 ... light guide plate

Claims (10)

A pattern image including a figure is recorded as a transmission or reflection type volume hologram, and as the pattern image, a bright figure is recorded in a relatively dark background, and the figure is drawn from the edge of the figure part. A pattern image is recorded in which a gradation band is provided along the edge where the brightness gradually changes from the brightness of the background outside the edge to the brightness inside the figure. Volume hologram. 2. The volume hologram according to claim 1, wherein the gradation band is a halftone dot pattern. 3. The volume hologram according to claim 1, wherein the pattern image is a flat image and is recorded as an image hologram. In a method for creating a volume hologram in which a pattern image is recorded,
A bright figure is recorded in a relatively dark background, and the brightness gradually changes from the brightness of the background outside the edge to the brightness inside the figure from the edge of the figure to the inside of the figure. A method for producing a volume hologram, comprising preparing a pattern image in which gradation bands to be provided are provided along an edge of the gradation band and photographing the pattern image as a transmission type or reflection type volume hologram. 5. The method for producing a volume hologram according to claim 4, wherein the gradation band comprises a halftone dot density pattern. 6. The volume hologram creating method according to claim 4, wherein the pattern image is a planar image and is recorded as an image hologram. A light guide plate that irradiates the reproduction illumination light, a volume hologram embedded in the light guide plate, and a light source disposed at at least one end of the light guide plate. In a hologram display device illuminated by illumination light guided by multiple reflections that repeat reflections,
In the volume hologram, a bright figure is recorded in a relatively dark background, and the brightness from the edge of the figure part toward the inside of the figure is changed from the brightness of the background outside the edge to the inside of the figure. A hologram display device, wherein a pattern image in which a gradation band gradually changing to brightness is provided along an edge thereof is recorded. A light guide plate that emits reproduction illumination light; a volume hologram disposed in an illumination light path emitted from one surface of the light guide plate; and a light source disposed at at least one end of the light guide plate. Is a hologram display device illuminated by illumination light emitted from one surface of the light guide plate,
In the volume hologram, a bright figure is recorded in a relatively dark background, and the brightness from the edge of the figure part toward the inside of the figure is changed from the brightness of the background outside the edge to the inside of the figure. A hologram display device, wherein a pattern image in which a gradation band gradually changing to brightness is provided along an edge thereof is recorded. 9. The hologram display device according to claim 7, wherein the gradation band is a halftone dot pattern. The hologram display device according to claim 7, wherein the pattern image is a flat image and is recorded as an image hologram.

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