JP2014191282A - Hologram recording method and hologram recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording method of a hologram where variation in luminance of a hologram image to be reproduced is small and images do not overlap under ambient light that is incident to a hologram recording surface at random from every direction, and a hologram recording medium recorded by the same method.SOLUTION: In a hologram recording method for recording images composed of a plurality of pixels, one pixel is composed of element holograms in N lines and N columns (N≥2), the respective element holograms in the pixel are recorded by identical object light and reference light which satisfies the condition that an angle Φ made by an orthogonal projection onto hologram recording medium surfaces of adjacent reference light is between 70° to 110°.

Description

The present invention relates to a hologram recording method and a hologram recording medium for recording a three-dimensional image.

A hologram is known as a method for outputting three-dimensional image data to a two-dimensional medium. Initially, the hologram was developed as a method of recording the object as a three-dimensional image by causing the reflected light from the actual object to interfere with the reference light in a coherent relationship with the reflected light in the hologram recording medium. It was.

In recent years, a hologram solid hard copy that can be used as a hard copy of a three-dimensional object has been invented, and its recording method and apparatus are disclosed in Japanese Patent Laid-Open No. 3-249686 (Patent Document 1). This hologram solid hard copy is configured by recording a plurality of dot-shaped element holograms on the surface of a substrate. In the recording method described above, an original pattern corresponding to each point of the hologram recording medium is displayed on the display means from the data of the three-dimensional image, and a dot-shaped element hologram corresponding to the displayed original pattern is displayed on the hologram recording medium. To record.

The hologram image recorded by the above method is used as a security label for product authentication. However, in order to reproduce the recorded hologram image, it is necessary to irradiate light from a direction that coincides as much as possible with the reference light at the time of recording (in the range of ± 45 ° based on the angle of the reference light), and from other directions The hologram image is not reproduced even when light is applied. In other words, when the hologram image is observed from a certain direction, an image having a high luminance is reproduced. However, when viewed from other directions, the luminance is low and the image is hardly reproduced. Therefore, compared to a two-dimensional medium (for example, a picture written on paper) that allows an image to be viewed with the same brightness when viewed from any direction, the brightness varies greatly depending on the viewing direction, and the image may or may not be visible. The image is dark.

Japanese Laid-Open Patent Publication No. 8-297458 (Patent Document 2) proposes to use a dedicated light source for reproducing a bright hologram image. By using a dedicated light source, it is possible to view an image with the same brightness from any direction. However, because it is necessary to prepare a dedicated lighting device, it cannot be used as a security label. Is done.

Japanese Patent Laid-Open No. 2001-109362 (Patent Document 3) obtains a hologram recording medium by using a computer-generated hologram technique in which interference fringes formed on a recording surface are obtained by a computer and a hologram is produced by an electron beam drawing apparatus. A hologram recording medium that is manufactured and capable of reproducing a completely different original image depending on the viewpoint position is disclosed. The hologram recording medium produced by the above recording uses a plurality of reference beams having different incident angles with respect to the hologram recording surface, and thus has a feature that another image is reproduced when the viewing direction is changed to the left or right or up and down. There are restrictions on stereoscopic viewing in the horizontal or horizontal direction. In addition, since different images are recorded for each angle of the reference light, an unclear image in which all the recorded images are overlapped is reproduced under ambient light in which light enters the hologram recording surface from all directions. Has the disadvantages.

JP-A-3-249686 JP-A-8-297458 JP 2001-109362 A

The present invention has been made in view of the above situation, and its purpose is that the variation in luminance of a reproduced hologram image is small under ambient light in which light enters the hologram recording surface from all directions, and It is an object of the present invention to provide a hologram recording method and a hologram recording medium recorded thereby, in which a plurality of images do not overlap each other and become unclear.

The above problems can be solved by the present invention described below.
(1) In a hologram recording method for recording an image composed of a plurality of pixels, one pixel is composed of element holograms of N rows and N columns (N ≧ 2), and the element holograms in the pixels are the same The hologram recording method is characterized in that recording is performed using the object light and reference light in which an angle Φ formed by orthogonal projection of adjacent reference lights onto the hologram recording medium surface satisfies 70 ° to 110 °.

(2) The hologram recording method according to (1), wherein one pixel is configured by an element hologram of 2 rows and 2 columns.

(3) A hologram recording medium for recording an image composed of a plurality of pixels, wherein one pixel is composed of element holograms of N rows and N columns (N ≧ 2), and each element hologram in the pixel is A hologram recording medium recorded with reference light in which an angle Φ formed by orthogonal projection of the same object light and adjacent reference light onto the hologram recording medium surface satisfies 70 ° to 110 °.

(4) The hologram recording medium according to (3), wherein one pixel is composed of an element hologram of 2 rows and 2 columns.

According to the present invention, it is possible to obtain a clear hologram image with a small variation in luminance and without overlapping of a plurality of images under indoor lighting that is exposed to light from all directions.

1 is an optical system diagram showing an optical system for recording on a hologram recording medium according to the present invention. It is a figure which shows the control method of the incident direction to the medium of reference light. (A) When reference light is incident from the left direction (b) When reference light is incident from the right direction. (A) The figure which showed the incident angle to the hologram recording medium surface of reference light. (B) It is the figure which showed the orthogonal projection of the reference light, and the angle which those make. It is the schematic of the brightness | luminance measurement of a hologram recording medium. It is a figure which shows the angle | corner which the orthogonal projections of reference light make. It is a figure which shows the shape of 1 pixel, and the recording pattern of each element hologram.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of an optical system for recording an image including a plurality of element holograms. A blue laser 1, a red laser 2, and a green laser 3 are arranged as laser light sources. Light emitted from the lasers 1, 2, 3 is converted into parallel light by the collimator lenses 4, 5, 6, and shutters 7, 8, After passing through 9, the blue laser light is bent in the traveling direction by the mirror 10 and guided to the half-wave plate 13 through the dichroic mirrors 11 and 12. Similarly, the red laser light and the green laser light are led to the half-wave plate 13 by bending the traveling direction of the laser light by the dichroic mirrors 11 and 12, respectively. The blue laser light, red laser light, and green laser light guided to the half-wave plate 13 are coaxial, and after the polarization direction is controlled by the half-wave plate 13, the beam splitter 14 separates the light into two light beams. Is done.

After the intensity of the object light 15 is adjusted by the ND filter 16, the beam diameter is expanded to the size of the spatial light modulator (SLM) 20 by the beam expanders 18 and 19 via the mirror 17, and the spatial light modulator ( The object light is amplitude-modulated by the SLM) 20, is beam-shaped by the relay lenses 21 and 23 and the Nyquist aperture 22, and then is condensed in the hologram recording medium 25 by the objective lens 24. The Nyquist aperture 22 filters the diffracted light by the spatial light modulator (SLM) 20 and simultaneously gives a signal beam shape to be exposed to the hologram recording medium 25.

The image (signal pattern) displayed on the spatial light modulator (SLM) 20 represents the light intensity distribution in the viewing direction of the partial image of the image to be reproduced. The spatial light modulator (SLM) 20 may be a transmissive device such as a liquid crystal (LCD) or a reflective device such as a digital mirror device (DMD) or liquid crystal on silicon (LCOS).

The reference beam 26 is transmitted through the optical path to the opposite side of the medium, and after adjusting the intensity by the ND filter 27, the hologram is obtained through the mirror 28, the aperture 29, the galvano mirror 30 which is an angle modulation optical element, and the relay lenses 31 and 32. The element hologram 33 is recorded by interfering with the object light irradiated into the recording medium 25 and condensed by the objective lens 24 in the hologram recording medium 25.

The aperture 29 gives a beam shape of reference light to be exposed to the hologram recording medium 25. It is preferable that the shape and size of the signal light beam and the reference light beam be as uniform as possible, and the region where the signal light beam and the reference light beam overlap gives the shape and size of the element hologram 33. By combining the galvanometer mirror 30 and the relay lenses 31 and 32, the incident direction of the reference light to the hologram recording medium 25 is controlled.

The hologram recording medium 25 is held on a movable stage such as an XY stage or a drum stage. After one element hologram 33 is formed, the element hologram 33 can be formed in a new unrecorded area by moving the hologram recording medium 25. The hologram recording medium 34 is produced by continuously recording the element hologram 33.

The blue laser 1, the red laser 2, and the green laser 3 are arranged in any region on the hologram recording medium 25 by controlling the opening / closing of the shutters 7, 8, 9 provided in each optical path in synchronization with the movement of the movable stage. Recording with blue laser light, red laser light, and green laser light is possible. The blue laser 1, red laser 2, and green laser 3 are preferably single mode lasers having coherence. The wavelength of each laser is not particularly limited, but preferably, the blue laser 1 is 440 to 490 nm, the red laser 2 is 600 to 680 nm, and the green laser 3 is 500 to 550 nm.

2A and 2B show a method for controlling the incident direction of the reference light 26 to the medium. The galvanometer mirror 30 and the hologram recording medium 25 are disposed at the focal positions of the relay lenses 31 and 32, respectively. The galvanometer mirror 30, the relay lenses 31, 32, and the hologram recording medium 25 are arranged on the same axis. The reference light 26 reflected by the galvanometer mirror 30 is irradiated to the same location on the hologram recording medium 25 via the relay lenses 31 and 32 regardless of the reflection direction. That is, by controlling the reflection angle at the galvanometer mirror 30, the direction of the reference light 26 irradiated on the hologram recording medium 25 can be controlled.

The uniaxial galvanometer mirror 30 can control the incident angle θ of the reference light 26 with respect to the medium normal. The angle range θmax with respect to the medium normal of the controllable reference beam 26 depends on the numerical aperture (NA) of the relay lens 32 and is expressed by the equation (I).

In order to widen the direction of reproduction light that can be used, it is necessary to increase the incident angle with respect to the medium normal of the reference light during recording. From the equation (I), the reference light direction is determined by the numerical aperture (NA) of the relay lens 32. For a lens with NA = 0.5, θmax to ± 30 degrees, and for a lens with NA = 0.85, θmax to ±±. It will be 60 degrees.

The spread (viewing angle) of the recorded image in the reflecting direction is determined by the numerical aperture (NA) of the objective lens 24. Therefore, in order to widen the viewing angle of the image, it is preferable that the NA of the objective lens 24 is large.

By using the biaxial galvanometer mirror 30, it is possible to control both the incident angle θ of the reference light 26 with respect to the medium normal and the angle Φ formed by orthogonal projection of the adjacent reference lights onto the hologram recording medium surface. Become. Here, adjacent reference beams refer to four pairs of AB, BC, CD, and DA in FIG. 3 showing the incident direction of the reference beam on the hologram recording medium surface (xy plane). The angle Φ formed by the orthogonal projection on the hologram recording medium surface indicates Φ _AB , Φ _BC , Φ _CD , Φ _DA .

In order to reproduce a normally recorded hologram, light must be applied from a direction that coincides as much as possible with the reference light used at the time of recording (in the range of ± 45 ° with respect to the angle of the reference light). The hologram image is not reproduced even when light is applied.

In order to widen the range in which the hologram is reproduced, a single pixel may be composed of a plurality of element holograms recorded by the same object beam and reference beams having different angles formed by orthogonal projections of the reference beams. . Since a hologram image is reproduced only in the range of 90 ° with one reference beam, in order to reproduce a hologram in the entire range (360 °), one pixel needs to be composed of four or more element holograms. The vertical and horizontal resolution (number of pixels per inch) of the recorded image is preferably constant, and for this purpose, one pixel is composed of element holograms of N rows and N columns (N ≧ 2). preferable.

However, since the size of the element hologram is always constant, as the number of N increases, the shape of one pixel increases, resulting in a decrease in resolution. Therefore, when N = 2, that is, 2 rows and 2 columns, the hologram can be reproduced in the entire range (360 °), and since the shape of one pixel is small, a sufficient resolution can be obtained, which is most preferable.

Further, in order to allow the hologram image to be observed no matter which direction the light is applied, the angle Φ formed by orthogonal projection of the reference light adjacent to each other during recording onto the hologram recording medium surface is 90 °. It is particularly preferred to record four element holograms. However, even if the angle Φ formed by the orthogonal projection is slightly deviated from 90 ° such as 89 ° or 91 °, the same effect can be obtained. If the angle Φ formed by the orthogonal projection is set to what degree, the holographic image can be observed depending on the image to be recorded. Is preferably 70 ° or more and 110 ° or less.

(Brightness measurement)
FIG. 4 is a schematic diagram of the luminance measurement of the hologram recording medium 35. After installing the hologram recording medium 35 at the rotation center of the turntable 36, the white LED light source 37 is installed at an angle α from the normal direction of the hologram recording medium 35. The light emitted from the LED light source 37 enters the hologram recording medium 35 at an angle α and is diffracted in the normal direction. The luminance L (α, β) of the diffracted light on the surface of the hologram recording medium 35 is measured by a luminance meter 38 installed just above the hologram recording medium 35.

The brightness measurement is performed every 90 ° while rotating the rotary table 360 ° (the rotation angle is β), so that when the hologram recording medium 35 is irradiated with light at a certain incident angle α, the rotation angle β The brightness of the hour can be evaluated.

Furthermore, after changing the incident angle α to the hologram recording medium 35 to α ₁ , α ₂ ,... Α _n and measuring the luminance L (α _n , β), the average luminance represented by the formula (II) is obtained. By calculating, it becomes possible to measure the luminance with higher accuracy.

（II）

(II)

For the hologram recording medium 35, the luminance of the reproduced image was evaluated at four points of β = 0 °, 90 °, 180 °, and 270 °, and when the minimum luminance / maximum luminance was calculated, the value was 0.5 or less. If, or bright depending on the direction to see the brightness of the reproduced image, become difficult to say the state is a bright image look even when viewed from anywhere to or darker. In order to obtain a bright image as seen from anywhere such as a two-dimensional medium (a picture written on paper), it is necessary that 0.5 <(minimum luminance / maximum luminance) ≦ 1.0.

Further, with respect to the hologram recording medium 35, the luminance evaluation of the reproduced image is performed at intervals of 0 ° within a range of 0 ° ≦ β ≦ 359 °, so that the number of reference lights used at the time of recording and the hologram recording medium between adjacent reference lights The angle Φ formed by the orthogonal projection on the surface can be specified. For example, as a result of the luminance evaluation of the hologram recording medium 35, if four peaks are obtained at a certain half width at intervals of about 90 °, it can be determined that the number of reference lights used during recording is four. Further, by obtaining the rotation angle β of the turntable 36 when the maximum value of each peak is obtained, the angle Φ formed by orthogonal projection of adjacent reference beams onto the hologram recording medium surface can be specified. For example, when the maximum value of each peak is obtained at β = 0 °, 89 °, 179 °, and 270 °, the angle Φ formed by the orthogonal projection can be specified as 89 °, 90 °, 91 °, and 90 °. That is, the number of reference lights is specified by the number of peaks having a certain half width, and the angle Φ formed by the orthogonal projection is specified by the rotation angle β of the rotary table 36 when the maximum value is obtained among the peaks. can do.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.

[Example 1]
(Production of hologram recording medium 25)
A recording material composition solution was prepared according to the following procedure.
Vinyl acetate polymer as matrix (Sigma Aldrich, weight average molecular weight Mw
= 100,000, n20 / D = 1.47) 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene (manufactured by Shin-Nakamura Chemical Co., Ltd.) as a photopolymerizable monomer in 1.6 g NK ester A-BPEF, n20 / D = 1.62) 2.0 g, neopentyl glycol diglycidyl ether (manufactured by Sigma-Aldrich, n20 / D = 1.46) 0.8 g, diethyl sebacate (Tokyo) 0.4 g of Kasei Kogyo Co., Ltd., n20 / D = 1.44) was added. To this mixture was further added 20 mg of a sensitizing dye (3-butyl-2- [3- (3-butyl-5-phenyl-1,3-benzoxazole-2 (3H)-) having sensitivity at wavelengths of 473 nm and 532 nm. Ylidene) prop-1-en-1-yl] -5-phenyl-1,3-benzoxazol-1-ium = hexafluoro-λ5-phosphanoid) and 20 mg of sensitizing dye sensitive to 633 nm (3-ethyl 2- [5- (3-Ethyl-1,3-benzoxazol-2 (3H) -ylidene) penta-1,3-dien-1-yl] -1,3-benzoxazole-3-ium bis (Trifluoromethanesulfone) imidate), and 50 mg of tetrabutylammonium butyltriphenylborate (manufactured by Showa Denko KK) as a polymerization initiator A dissolved 1.09 g acetone solution (1.00 g as acetone) was added and dissolved by stirring. In this way, a recording material composition solution was obtained.

The obtained recording material composition solution was coated on a 100 μm-thick PET film using a bar coater and dried under reduced pressure at room temperature overnight. The film thickness of the recording material layer after drying was 20 μm. This was affixed to a 1.0 mm thick slide glass so that the recording material layer was in contact with the glass surface to obtain a hologram recording medium 25.

(Hologram image recording)
The laser is an Nd-YAG laser (wavelength 473 nm, Showa Optronics) as the blue laser 1, a He-Ne gas laser (wavelength 633 nm) as the red laser 2, and an Nd-YAG laser (wavelength 532 nm, Coherent) as the green laser 3. A liquid crystal spatial light modulator (Seiko Epson L3P06x-8x) was used as the spatial light modulator (SLM) 20. The objective lens 24 installed in the optical path of the object light 15 was an objective lens with NA of 0.55. The relay lenses 31 and 32 installed in the optical path of the reference beam 26 are both NA0.5 lenses.

The reference beam 26 uses a biaxial galvanometer mirror 30 and is tilted by 30 ° with respect to the normal line of the hologram recording medium 25 and an angle Φ formed by orthogonal projection of the reference beams onto the hologram recording medium surface is shown in FIG. As shown to (a), it set so that it might respectively become 90 degrees. In FIG. 5A, an element hologram to be recorded with the reference light A is an element hologram (A) 39, an element hologram to be recorded with the reference light B is similarly an element hologram (B) 40, and an element hologram to be recorded with the reference light C is shown. An element hologram (C) 41 and an element hologram recorded with the reference light D are referred to as an element hologram (D) 42.

Element hologram 33 of □ 250 × 250 μm was recorded in a □ 4 × 4 cm region of hologram recording medium 25 at a recording pitch of 250 μm. One pixel is composed of four element holograms (A) to (D) as shown in FIG. 6A, and the element holograms (A) to (D) in the pixel are shown in FIG. It is not limited to the pattern a) and can be arbitrarily arranged. In this way, a hologram recording sample 1 was obtained.

(Brightness measurement)
The hologram recording sample 1 was placed on the rotary table 36 of FIG. As the luminance meter 38, a spectroradiometer SR-2 (Topcon Corporation) was used. During the measurement, the distance of the white LED light source was adjusted so that the illuminance was 500 lx / m ² on the hologram recording sample 1.

Table 1 shows the measurement results of the average luminance represented by the above formula (II) in the reproduction light from the hologram recording sample 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 90 cd / ^{m 2,} with beta = 90 ° in ^{90Cd / m 2, 95Cd / m} 2 at β = 180 °, β = 270 ° in 90 cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 4.3. The minimum luminance / maximum luminance is 0.95, and the hologram recording sample 1 is from all directions (β = 0 ° ± 45 °, 90 ° ± 45 °, 180 ° ± 45 °, 270 ° ± 45 °). The recorded image could be observed with almost the same brightness. Since this luminance value is about the same as the luminance value of paper (about 90 Cd / m ² ) measured under the same illuminance of 500 lx / m ² , it can be determined that the hologram recording sample 1 has the same brightness as paper. Further, since the horizontal resolution / vertical resolution = 1, there is no difference in resolution in the vertical and horizontal directions of the recorded image, and the size of the pixels is sufficiently small, so that the overall resolution has no problem. Furthermore, since the same object light was used for recording within one pixel, a clear image could be observed.

Next, the luminance evaluation of the reproduced image was performed on the hologram recording sample 1 in the range of 0 ° ≦ β ≦ 359 ° every 1 °. As a result, the maximum value of each peak is obtained at β = 0 °, 90 °, 180 °, and 270 °, and the angle Φ formed by orthogonal projection of adjacent reference beams onto the hologram recording medium surface is 90 °, 90 °. It was confirmed that the angle was 90 °, 90 °.

[Example 2]
A hologram recording sample 2 was obtained on the hologram recording medium 25 produced in the same manner as in Example 1 using the optical system shown in FIG. However, the reference light 26 is inclined by 30 ° with respect to the normal line of the hologram recording medium 25, and the angle Φ formed by orthogonal projection of the reference lights onto the surface of the hologram recording medium 25 is as shown in FIG. Were set so that Φ _AB = 80 °, Φ _BC = 100 °, Φ _CD = 80 °, and Φ _DA = 100 °.

The luminance measurement of the hologram recording sample 2 was performed under the same conditions as in Example 1, and the results are shown in Table 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 100 Cd / ^{m 2,} with beta = 90 ° in ^{70Cd / m 2, 100Cd / m} 2 at β = 180 °, β = 270 ° in 70 cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 30.0. Further, the minimum luminance / maximum luminance was 0.70, and the horizontal resolution / vertical resolution = 1.00.

[Example 3]
A hologram recording sample 3 was obtained on the hologram recording medium 25 produced in the same manner as in Example 1 using the optical system in FIG. 1 with the pattern in FIG. 6A in the same manner as in Example 1. However, the reference light 26 is inclined by 30 ° with respect to the normal line of the hologram recording medium 25, and the angle Φ formed by orthogonal projection of the reference lights onto the surface of the hologram recording medium 25 is as shown in FIG. Are set such that Φ _AB = 70 °, Φ _BC = 110 °, Φ _CD = 70 °, and Φ _DA = 110 °.

Under the same conditions as in Example 1, the luminance of the hologram recording sample 3 was measured, and the results are shown in Table 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 110 cd / ^{m 2,} with beta = 90 ° in ^{55Cd / m 2, 110Cd / m} 2 at β = 180 °, β = 270 ° in 55 cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 55.0. The minimum luminance / maximum luminance was 0.50, and the horizontal resolution / vertical resolution = 1.00.

[Comparative Example 1]
Hologram image recording was performed on the hologram recording medium 25 manufactured in the same manner as in Example 1 using the optical system of FIG. The uniaxial galvanometer mirror 30 was adjusted so that the reference beam 26 was +30 degrees with respect to the medium normal.

Element hologram 33 of □ 250 × 250 μm was recorded in a □ 4 × 4 cm region of hologram recording medium 25 at a recording pitch of 250 μm. After irradiating the reference beam 26 and the object beam 15 tilted by +30 degrees from the normal line of the hologram recording medium 25 to form the element hologram (A) 39, the reference beam 26 and the object beam tilted by +30 degrees in the same manner are moved on the XY stage. 15 was irradiated to form an element hologram (A) 39. This was repeated to obtain a hologram recording sample 4 in which the element hologram (A) 39 was recorded on the entire surface as individual pixels as shown in FIG. 6B.

Under the same conditions as in Example 1, the luminance of the hologram recording sample 4 was measured, and the results are shown in Table 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 360 cd / ^{m 2,} with beta = 90 ° in ^{5Cd / m 2, 5Cd / m} 2 at β = 180 °, β = 270 ° in 5Cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 307.4. The minimum luminance / maximum luminance was 0.01, and the horizontal resolution / vertical resolution was 1.00. From this result, the hologram recording sample 4 efficiently reflects light incident from a specific direction (β = 0 ° ± 45 °), but hardly reflects light incident from other directions. That is, the recorded image can be observed brightly only when observed from a specific direction, but the recorded image can hardly be observed from other directions. Therefore, since the range in which the hologram image is not reproduced is wide, even if a locally bright image is reproduced, an overall dark impression is given.

[Comparative Example 2]
Hologram image recording was performed on the hologram recording medium 25 manufactured in the same manner as in Example 1 using the optical system of FIG. The uniaxial galvanometer mirror 30 was adjusted so that the reference beam 26 was +30 degrees and −30 degrees with respect to the medium normal. Further, the angle Φ formed by orthogonal projection of the reference beams onto the surface of the hologram recording medium 25 was set to be 180 degrees as shown in FIG.

Element hologram 33 of □ 250 × 250 μm was recorded in a □ 4 × 4 cm region of hologram recording medium 25 at a recording pitch of 250 μm. After irradiating the reference beam 26 and the object beam 15 inclined by +30 degrees from the normal line of the hologram recording medium 25 to form the element hologram (A) 39, the XY stage is moved to beside the element hologram (A) 39, − An element hologram (B) 40 was formed by irradiating the reference beam 26 and the object beam 15 inclined by 30 degrees. The adjacent pair of element hologram (A) 39 and element hologram (B) 40 is used as one pixel and is repeated while changing the object light for each pixel, and is recorded in a pattern as shown in FIG. Recording sample 5 was obtained.

Under the same conditions as in Example 1, the luminance of the hologram recording sample 5 was measured, and the results are shown in Table 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 180 cd / ^{m 2,} with beta = 90 ° in ^{5Cd / m 2, 180Cd / m} 2 at β = 180 °, β = 270 ° in 5Cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 175.0. The minimum luminance / maximum luminance was 0.03. From this result, the hologram recording sample 5 efficiently reflects light incident from a specific direction (β = 0 ° ± 45 °, 180 ° ± 45 °), but almost reflects even when light strikes from other directions. do not do. That is, the recorded image can be observed brightly only when observed from a specific direction, but the recorded image can hardly be observed from other directions. Therefore, the hologram recording sample 5 has a wide range in which the hologram image is not reproduced as in the comparative example 1, so that even if a bright image is reproduced locally, an overall dark impression is given. Also, since the horizontal resolution / vertical resolution = 0.50, the vertical / horizontal resolution difference is large.

[Comparative Example 3]
Hologram image recording was performed on the hologram recording medium 25 manufactured in the same manner as in Example 1 using the optical system of FIG. The reference beam 26 uses a biaxial galvanometer mirror 30. The reference beam 26 is inclined by 30 ° with respect to the normal line of the hologram recording medium 25, and the orthogonal projection of the reference beams onto the surface of the hologram recording medium 26 is made. The angle Φ was set to be the angle shown in FIG. In FIG. 5 (e), the element hologram recorded by the reference light A from the 0 ° direction is referred to as an element hologram (A) 39, and similarly recorded by the reference light B and the reference light C from the 120 ° and 240 ° directions. These element holograms are referred to as an element hologram (B) 40 and an element hologram (C) 41, respectively. The three types of element holograms were recorded as one pixel in a pattern as shown in FIG. 6D, and a hologram recording sample 6 was obtained.

Under the same conditions as in Example 1, the luminance of the hologram recording sample 6 was measured, and the results are shown in Table 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 120 cd / ^{m 2,} with beta = 90 ° in ^{40Cd / m 2, 30Cd / m} 2 at β = 180 °, β = 270 ° in 40 cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 72.6. The minimum luminance / maximum luminance was 0.25. Since the value of the minimum luminance / maximum luminance is smaller than the critical value of 0.50 at which the luminance variation starts to be noticeable, when the hologram recording sample 6 is observed, the image becomes brighter or darker depending on the viewing direction. Further, the horizontal / vertical resolution = 0.33 and the vertical / horizontal resolution were different, so that the image was uncomfortable.

[Comparative Example 4]
A hologram recording sample 7 was obtained on the hologram recording medium 25 produced in the same manner as in Example 1, using the optical system shown in FIG. However, the reference light 26 is inclined by 30 ° with respect to the normal line of the hologram recording medium 25, and the angle Φ formed by orthogonal projection of the reference light onto the surface of the hologram recording medium 26 is Φ as shown in FIG. _{AB = 90 °, Φ BC =} 90 °, Φ CD = 90 °, was set to be Φ _DA = 90 °.

Under the same conditions as in Example 1, the luminance of the hologram recording sample 7 was measured, and the results are shown in Table 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 95Cd / ^{m 2,} with beta = 90 ° in ^{90Cd / m 2, 90Cd / m} 2 at β = 180 °, β = 270 ° in 90 cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 4.3. The minimum luminance / maximum luminance was 0.95. With this hologram recording sample 7, images recorded from all directions (β = 0 ° ± 45 °, 90 ° ± 45 °, 180 ° ± 45 °, 270 ° ± 45 °) could be observed with substantially the same luminance. However, since the horizontal / vertical resolution = 0.25, the vertical and horizontal resolutions differ greatly, and the image is very uncomfortable.

[Comparative Example 5]
A hologram recording sample 8 was obtained on the hologram recording medium 25 produced in the same manner as in Example 1 using the optical system shown in FIG. However, the reference light 26 is inclined by 30 ° with respect to the normal line of the hologram recording medium 25, and the angle Φ formed by orthogonal projection of the reference light onto the surface of the hologram recording medium 26 is Φ as shown in FIG. _{AB = 60 °, Φ BC =} 120 °, Φ CD = 60 °, was set to be Φ _DA = 120 °.

Under the same conditions as in Example 1, the luminance of the hologram recording sample 8 was measured, and the results are shown in Table 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 120 cd / ^{m 2,} with beta = 90 ° in ^{30Cd / m 2, 120Cd / m} 2 at β = 180 °, β = 270 ° in 30 cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 90. The minimum luminance / maximum luminance was 0.25, and the horizontal resolution / vertical resolution was 1.00.

[Comparative Example 6]
A hologram recording sample 9 was obtained by performing hologram image recording on the hologram recording medium 25 produced in the same manner as in Example 1 with the pattern of FIG. However, hologram recording was performed on the four element holograms in one pixel with different object light and reference light similar to Example 1.

Under the same conditions as in Example 1, the luminance of the hologram recording sample 9 was measured, and the results are shown in Table 1. The average luminance in the rotational angle beta = 0 ° of the rotary table is 90 cd / ^{m 2,} with beta = 90 ° in ^{95Cd / m 2, 90Cd / m} 2 at β = 180 °, β = 270 ° in 90 cd / ^{m 2} there were. The variation (standard deviation σ) of the four luminance values was 4.3. Further, the minimum luminance / maximum luminance was 0.95, and the horizontal resolution / vertical resolution = 1.00. As in Example 1, recorded images were reproduced brightly when light was irradiated from four directions (β = 0 ° ± 45 °, 90 ° ± 45 °, 180 ° ± 45 °, 270 ° ± 45 °). However, since recording was performed using different object light for each element hologram, when the hologram sample 9 was observed, the four images overlapped and reproduced, and a clear image could not be observed.

These results are summarized in Table 1.

From the above embodiments, the hologram recording medium produced by the recording method of the present invention can reproduce an image having a small luminance variation and high visibility under any ambient light.

DESCRIPTION OF SYMBOLS 1 ... Blue laser 2 ... Red laser 3 ... Green laser 4, 5, 6 ... Collimator lens 7, 8, 9 ... Shutter 10, 17, 28 ... Mirror 11, 12 ... Dichroic mirror 13 ... 1/2 wavelength plate 14 ... Beam Splitter 15 ... Object light 16, 27 ... ND filter 18, 19 ... Beam expander 20 ... Spatial light modulator (SLM)
21, 23, 31, 32 ... relay lens 22 ... Nike store aperture 24 ... objective lens 25 ... hologram recording medium 26 ... reference beam 29 ... aperture 30 ... galvanometer mirrors 34, 35, 43-51 ... hologram recording medium 36 ... rotary table 37 ... White LED light source 38 ... Luminance meter 39 ... Element hologram (A)
40 ... Element hologram (B)
41 ... Element hologram (C)
42 ... Element hologram (D)

Claims (4)

  In a hologram recording method for recording an image composed of a plurality of pixels, one pixel is composed of element holograms of N rows and N columns (N ≧ 2), and each of the element holograms in the pixel has the same object light A hologram recording method comprising: recording with reference light in which an angle Φ formed by orthogonal projection of adjacent reference beams onto the hologram recording medium surface satisfies 70 ° to 110 °. 2. The hologram recording method according to claim 1, wherein one pixel is constituted by an element hologram of 2 rows and 2 columns. A hologram recording medium for recording an image composed of a plurality of pixels, wherein one pixel is composed of element holograms of N rows and N columns (N ≧ 2), and each element hologram in the pixels is the same object A hologram recording medium recorded with reference light in which an angle Φ formed by orthogonal projection of light and adjacent reference light onto the hologram recording medium surface satisfies 70 ° to 110 °. 4. The hologram recording medium according to claim 3, wherein one pixel is composed of an element hologram of 2 rows and 2 columns.

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