JPH11352864A - Method for duplication of hologram and hologram duplicated by this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unwanted interference fringes from being recorded by incidence of diffracted light of higher order other than the 0 order, and +1st order from an original plate hologram on a hologram photosensitive material at the time of duplicating the hologram by duplication from the original plate hologram or diffraction grating. SOLUTION: The method for optical duplication to the photosensitive material 32 from the hologram of the original plate or diffraction grating 30 satisfies two mathematical conditions of the duplication wavelength λ at which the diffracted light below the -1st order and above the +1st order on the photosensitive material 32 side. Even if, therefore duplication is executed by using this original plate, the undesired interference fringes are not recorded in the duplicate product and even if this duplicate product is reconstructed, the occurrence of unwanted stray light does not occur and the degradation in diffraction efficiency does not occur either.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hologram duplication method and a hologram duplicated by the method.
In particular, 0 generated from the hologram master or diffraction grating master
, Higher order (+2, +3, +4,..., -1, -2, -3, -4,.
The present invention relates to a hologram duplication method for preventing recording of unnecessary interference fringes generated between a + 1st-order diffracted light and a hologram duplicated by the method.

[0002]

2. Description of the Related Art A hologram array can be used, for example, instead of a microlens array. As one such hologram array, the present applicant has filed Japanese Patent Application No.
In -12170 and the like, a hologram color filter for a liquid crystal display device was proposed. The structure is composed of an eccentric Fresnel zone plate-shaped micro-hologram array. Further, in the above-mentioned application, as another hologram color filter for a liquid crystal display device having the same function as this micro hologram array, a hologram or diffraction grating composed of parallel and uniform interference fringes and a hologram or diffraction grating arranged on the incident side or the exit side thereof are provided. Also proposed are those that consist of a converging lens array. Hereinafter, a hologram color filter composed of a typical eccentric Fresnel zone plate-shaped micro-hologram array will be briefly described.

[0003] A liquid crystal display device using the hologram color filter will be described with reference to the sectional view of FIG. In the figure, a hologram array 5 constituting a hologram color filter is arranged at a distance from a liquid crystal display element 6 which is regularly divided into liquid crystal cells 6 '(pixels), on the side of incidence of a backlight 3. On the back of the liquid crystal display element 6,
A black matrix 4 provided between the liquid crystal cells 6 'is arranged. In addition to the above, polarizing plates (not shown) are arranged on both sides of the liquid crystal display element 6. In addition, between the black matrix 4, similarly to the conventional color liquid crystal display device, an absorption type color filter that transmits light of colors corresponding to R, G, and B color separation pixels is additionally arranged. You may do so.

The hologram array 5 has a repetition period of R, G, and B color separation pixels, that is, a set of three liquid crystal cells 6 ′ adjacent to each other in the direction of the liquid crystal display element 6 in the plane of the paper. The micro holograms 5 'are arranged in an array at the same pitch as the repetition pitch. The micro holograms 5' are aligned with each set of three liquid crystal cells 6 'adjacent to each other in the direction of the plane of the liquid crystal display element 6 and each of them has one micro hologram. Each of the micro holograms 5 ′ corresponds to the light of the green component in the backlight 3 that enters at an angle θ with respect to the normal to the hologram array 5 and corresponds to the micro hologram 5 ′. In order to converge on the liquid crystal cell G at the center of the three color separation pixels R, G, and B, the interference fringes are formed in a Fresnel zone plate shape as schematically shown in FIG. (Eccentric hologram Lens). The minute hologram 5 'is formed of a transmission hologram such as a relief type, a phase type, and an amplitude type, which has little or no wavelength dependence of diffraction efficiency. Here, the fact that there is no or little wavelength dependence of the diffraction efficiency means that only a specific wavelength is diffracted and other wavelengths are hardly diffracted as in a Lippmann hologram. The diffraction grating having a small wavelength dependence of the diffraction efficiency diffracts at different diffraction angles according to the wavelength.

[0005] With such a configuration, when the white backlight 3 that enters at an angle θ with respect to the normal line from the surface of the hologram array 5 opposite to the liquid crystal display element 6 is incident, the wavelength is reduced. Accordingly, the diffraction angle of the minute hologram 5 'is different, and the condensing position for each wavelength is dispersed in a direction substantially parallel to the surface of the hologram array 5. Among them, the red wavelength component is located at the position of the liquid crystal cell R displaying red, the green component is located at the position of the liquid crystal cell G displaying green, and the blue component is located at the position of the liquid crystal cell B displaying blue. By arranging the hologram array 5 so as to diffract and condense, each color component passes through each liquid crystal cell 6 'with little attenuation by the black matrix 4, and the color components of the liquid crystal cell 6' at the corresponding position. Color display according to the state can be performed.

As described above, by using the hologram array 5 as a color filter, each wavelength component of a conventional backlight for a color filter can be made incident on each liquid crystal cell 6 'without waste and without absorption. Can be greatly improved.

The production of the color filter 5 composed of a hologram array as described above is performed, for example, by adding +1 diffracted from a micro hologram lens array composed of a computer hologram.
The duplication method is based on two-beam interference between the next multipoint convergent light and the zero-order transmitted light. The duplication method will be briefly described with reference to the cross-sectional view of FIG.
Is calculated by a computer, a chromium film is formed on the glass substrate 1, an electron beam resist is applied thereon, and the interference fringes obtained as a result of the calculation are drawn and developed by an electron beam, and By etching the film to form a chromium pattern 2, an amplitude type computer generated hologram (CGH: Computer Generate)
d Hologram) 5 'array 7' is made.
Next, as shown in FIG.
A hologram photosensitive material 18 comprising a GH array 7 'as a hologram master, a photosensitive layer 13 of a photopolymer or the like provided on a glass substrate 12 on a chromium pattern 2 and a cover film 14 laminated thereon is covered with a cover. On the film 14 side, they are adhered to each other through an index matching liquid or overlapped with a slight gap.
Laser light 9 is incident at an angle θ corresponding to the backlight 3 of the above, and the convergent diffracted light 10 ′ generated by each CGH 5 ″ of the CGH array 7 ′ and the linearly transmitted light 11 interfere in the photosensitive layer 13 of the hologram photosensitive material 18. Then, the CGH array 7 'is duplicated, and the duplicated hologram is used as the hologram array 5 in Fig. 9. The incident angle of the laser beam 9 at the time of the duplication is not necessarily substantially equal to the incident angle θ of the backlight 3. It is not necessary to make the wavelength equal, and the wavelength does not need to be substantially equal to the wavelength of the backlight 3.

[0008]

By the way, when a laser beam 9 is incident on an amplitude type hologram such as a CGH array 7 ', as shown schematically in FIG.
, The + 2nd-order diffracted light 22, other +3, +4,... And -1, -2, -3, -4 ,
... the next higher-order diffracted light 23 is generated. For example, the + 2nd-order diffracted light 22 interferes with the 0th-order diffracted light 20 or the + 1st-order diffracted light 21 in the photosensitive layer 13 of the hologram photosensitive material 18 arranged in close contact or with a gap, and unnecessary interference fringes are recorded simultaneously with the duplication. Would. If such unnecessary interference fringes are recorded while being superimposed on the duplicated regular hologram interference fringes, the diffraction efficiency of the duplicated hologram is reduced, and stray light is generated by the unnecessary interference fringes. The quality of the reproduced image from the camera. Also,
In the case of the hologram color filter 5 shown in FIG. 9, stray light due to such unnecessary interference fringes lowers the display contrast of the color liquid crystal display device.

The present invention has been made in view of such problems of the prior art, and an object thereof is to copy a hologram from an original hologram or a diffraction grating to a 0th order and a + 1st order from the original hologram. Another object of the present invention is to provide a hologram duplication method for preventing a high-order diffracted light other than the above from being incident on a hologram photosensitive material and recording unnecessary interference fringes, and a hologram duplicated by the method.

[0010]

According to the present invention, there is provided a method for duplicating a hologram according to the present invention, comprising the steps of optically duplicating a hologram or diffraction grating of an original to a photosensitive material, wherein sin [φ + sin ^-1 ｛λ / (2nΛcosφ)｝] + λ / (nΛ) ≧ 1 (13) and sin [φ + sin ⁻¹ {λ / (2nΛcosφ)}]-2λ / (nΛ) ≦ -1 (14) , Λ: one of the surface pitches of the original plate, n: average refractive index of the photosensitive material, φ: target fringe angle when recording a duplicate, and replicating with a light beam of wavelength λ that satisfies It is a method.

Another hologram duplication method of the present invention is a method of optically duplicating a hologram or a diffraction grating of an amplitude type original plate into a photosensitive material, wherein sin [φ + sin ^-1 {λ / (2nΛcosφ)}] + λ. / (NΛ) ≧ sinα (15) and sin [φ + sin ⁻¹ {λ / (2nΛcosφ)}] − 2λ / (nΛ) ≦ −sinα (16) where α = tan ⁻¹ (RdΛ / t), Λ: one of the surface pitches of the amplitude type master, n: average refractive index of the photosensitive material, φ: target fringe angle at the time of recording a duplicate, d: amplitude type master , Average duty ratio (space / pitch), t: average film thickness of the line portion (opaque portion) of the amplitude type master, r: a value satisfying 0.5 ≦ r ≦ 1, It is a method characterized by the following.

In these cases, the hologram of the original plate may be formed of an array of elementary holograms that converge at a position with a fixed focal length.

The present invention includes a hologram duplicated by such a hologram duplication method.

In the present invention, in reproducing the original,
Since no high-order light is generated, no unwanted interference fringes are recorded on the duplicated product even when the original is duplicated, and unnecessary stray light does not occur even when the duplicated product is reproduced, and there is no reduction in diffraction efficiency. Alternatively, in reproducing the original, the intensity of high-order light can be reduced, so that even if the original is duplicated, the degree of recording of unwanted interference fringes on the duplicate is low, and unnecessary stray light is unnecessary even if the duplicate is reproduced. Is weak, and there is almost no decrease in diffraction efficiency.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and an embodiment of a hologram duplication method according to the present invention will be described below. In general, a hologram and a diffraction grating generate diffracted light even when irradiated with illumination light different from the recording wavelength. Therefore, it is assumed that a relatively long wavelength is used as a replication wavelength of a hologram (hereinafter, a hologram including both a hologram and a diffraction grating, unless otherwise specified). The specific description is shown below.

The type of the hologram or diffraction grating of the original plate is as follows:
It may be an amplitude type or a phase type, but here,
The case of the amplitude type will be described as an example. FIG. 1 shows the diffraction grating 3
FIG. 4 shows a diagram for explaining diffraction by zero. An amplitude type diffraction grating 30 is arranged on the boundary surface between the entrance side medium 31 and the exit side medium 32, the refractive index of the entrance side medium 31 is set to n ′, and the exit side medium 3 is set.
The average refractive index of 2 is n. First, the incident light 33 having the wavelength λ
In the case where the original 30 is copied to the photosensitive material (emission side medium) 32 in FIG. 1, in FIG. 1, the angle of the m-th order diffracted light in the photosensitive material 32 is θ _m (m =. , +
1, + 2, ... However, the sign + is omitted. ).
In addition, Λ is the surface pitch of the original 30 and φ is the fringe angle (target) representing the inclination of the interference fringe when recording a duplicate. Theta _in in the figure is the incident angle of the incident light 33, Snell's law holds between the theta _0. The definitions of these parameters are as shown in FIG.

At this time, θ ₀ and θ ₁ are set so that −π / 2 <θ ₁ <θ ₀ <π / 2 (1). From the diffraction equation, sin θ ₀ -sin θ ₁ = λ / (nΛ) (2) sin θ ₀ -sin θ _m = mλ / (nΛ) (3) From equations (2) and (3), sin θ _m = m sin θ ₁ − (m−1) sin θ ₀ (4) Here, as a constraint condition, (θ ₀ + θ ₁ ) / 2 = φ (the fringe angle φ is a value at the time of producing a hologram such as heating). A correction value may be used in advance in anticipation of the angle change.) From this, θ ₀ = φ + x (5) θ ₁ = φ−x (6) (x> 0) and substituting the equations (5) and (6) into the equation (2), By transforming, 2 cos φ sinx = λ / (nΛ) x = sin ⁻¹ {λ / (2nΛcos φ)} (7) From equations (3) and (5), sin θ _m = sin (φ + x) −mλ / ( nΛ) = sin [φ + sin ⁻¹ {λ / (2nΛcosφ)}] − mλ / (nΛ) (8) For the −1st order light, m = −1 is substituted into the equation (8), and sin θ ₋₁ = sin [φ + sin ⁻¹ {λ / (2nΛcosφ)}] + λ / (nΛ) (9) ) Is obtained. For the + 2nd-order light, substituting m = 2 into equation (8), sin θ ₂ = sin [φ + sin ⁻¹ {λ / (2nΛcosφ)}] − 2λ / (nΛ) (10) can get. Here, the range of x is the expression (1) and (5),
According to the equation (6), x <π / 2−φ and x <π / 2 + φ, so that, collectively, 0 <x <π / 2−φ | (11) (7), (11) from the equation, λ / (2nΛcosφ) <sin a λ / (2nΛcosφ) <cosφ λ <2nΛcos 2 φ ··· (12) (π / 2- | | φ).

The condition that no diffracted light of -1 order or less and +2 or more order does not occur on the exit side is given by the following equation (1).
In consideration of <θ ₂ <θ ₁ <θ ₀ <θ ₋₁ <..., Sin θ ₋₁ ≧ 1 and sin θ ₂ ≦ −1, respectively, at this time, from equations (9) and (10), sin [φ + sin ⁻¹ {λ / (2nΛcosφ)}] + λ / (nΛ) ≧ 1 (13) and sin [φ + sin ⁻¹ ｛λ / (2nΛcosφ)｝] − 2λ / (nΛ) ≦ -1 (14)

Next, the case where the original 30 is an amplitude grating will be described. As shown in FIG. 2, when the line 30 ′ of the amplitude grating 30 and the line portion (opaque portion) 30 ′ in the space 30 ″ are opaque and thick, the space portion 30 ″ (width of dΛ) is reached. Light beam diffraction angle α = tan
The ratio r of the component diffracted at ^-1 (rdΛ / t) is geometrically affected (absorbed, irregularly reflected, etc.) on the side surface of the line portion 30 ', and the diffracted light is attenuated. Where d
Is the average duty ratio (space / pitch) of the amplitude-type master 30, t is the average film thickness of the line portion 30 'of the amplitude-type master 30, r is the line portion (opaque portion) 30' of the amplitude-type master 30
Is a rate of attenuation caused by the thickness of the sheet. This is the same regardless of whether α is positive or negative. Equation (1)
・ <Θ ₂ <θ ₁ <θ ₀ <θ ₋₁ <.
When nθ ₋₁ ≧ sin α, sin θ ₂ ≦ −sin α,
Light of -1 order or lower and +2 or higher order is affected and attenuated on the side surface of the line portion 30 'at a rate of r or higher, respectively. From the expressions (9) and (10), the condition is as follows: sin [φ + sin ^-1 ｛λ / (2nφcosφ)｝] + λ / (nΛ) ≧ sinα (15) and sin [φ + sin ^-1 ｛λ / (2nΛcosφ)｝] − 2λ / (nΛ) ≦ −sinα (16) r is between 0 and 1. By setting this value to 0.5 ≦ r ≦ 1 (17), half or more of the -1st or lower and + 2nd or higher order diffracted lights are in the line portion. Vignetting and attenuation will occur on the side of 30 '. For this purpose, it is desirable that the side surface of the line portion 30 'be made of a light absorbing material at least for the replication wavelength λ.

Hereinafter, comparative examples and examples of the present invention will be described. Comparative Example A hologram (diffraction grating) to be obtained by duplication is set under the following design conditions (FIG. 3).・ Simple diffraction grating ・ Design wavelength 440nm ・ Incident angle 52.4 ° (in a medium with a refractive index of 1.47) (converted to 50 ° in a medium with a refractive index of 1.52) ・ Emission angle 0 ° (with a refractive index of 1)・ Slant angle φ = 25 ° Amplitude diffraction grating consisting of a uniform line-and-space chrome mask as a master for duplicating a hologram (diffraction grating) satisfying such design conditions Was prepared. The surface pitch is Λ = 378 nm (uniform).

A copy was made on a photosensitive material (n = 1.52) using the original under the following conditions.・ Replication wavelength 457 nm ・ Incident angle θ _in = 53.5 ° (in a medium with a refractive index of 1.47)
(Converted to a refractive index of 1.52, 51.0 ° (= θ ₀ )) Under these conditions, secondary light is generated from the original plate. The stray light considered to be was observed. At this time, in the calculation, (9),
From equation (10), sin θ ₂ = −0.81> −1 (+2
Order diffracted light), sin θ ₋₁ = 1.57 ≧ 1 (−1
No second-order diffracted light is generated).

FIG. 6 shows that the surface pitch Λ = 378 nm
In the case of (uniform), the relationship between the replication wavelength λ and the diffraction angles θ ₀ , θ ₁ , and θ ₂ , which is derived by the equation (8) and is obtained when the simple diffraction grating obtained by replication has a slant angle φ = 25 °, Show. Here, the refractive index n ′ of the incident side medium is set to 1.47, and the refractive index n of the output side medium (photosensitive material) is set to 1.52.

Example 1 A hologram (diffraction grating) to be obtained by duplication is designed under the same design conditions as in the comparative example (FIG. 3). As a master for duplicating a hologram (diffraction grating) satisfying such a design condition, the same amplitude type diffraction grating as in the comparative example was used.

Then, a copy was made on a photosensitive material (n = 1.52) using the original plate under the following conditions (FIG. 4). • Duplicate wavelength 532 nm • Incident angle θ _in = 58.7 ° (in a medium with a refractive index of 1.47)
(Converted to a refractive index of 1.52, 55.7 ° (= θ ₀ )) Under this condition, since no secondary light is generated from the original, even if the reproduced product is reproduced with white light, the secondary light is obtained. No stray light attributed to the influence of was observed. At this time, the calculation
From equations (9) and (10), sin θ ₂ = −1.03 ≦ −
1 (no +2 order diffracted light is generated), sin θ ₋₁ = 1.75
≧ 1 (−1st-order diffracted light is not generated).

[Second Embodiment] A hologram to be obtained by duplication has the following design conditions (FIG. 5).・ Eccentric hologram lens (FIGS. 9 and 10) Focal length 30 mm (in a medium with a refractive index of 1.52) Lens diameter 4 mm ・ Design wavelength 440 nm ・ Incident angle 52.4 ° (in a medium with a refractive index of 1.47) (refraction) Emission angle 0 ° (in a medium with a refractive index of 1.52) (at the center of the eccentric hologram lens) Slant angle φ = 25 ° (center of the eccentric hologram lens) As an original for duplicating a hologram satisfying such design conditions, an amplitude-type computer hologram made of a chrome mask was prepared. The surface pitch on the surface of FIG.
Λ = 348 nm to 414 nm (Λ = 378n at the center)
m).

Then, a copy was made on a photosensitive material (n = 1.52) under the same copy conditions as in Example 1. • Duplicate wavelength 532 nm • Incident angle θ _in = 58.7 ° (in a medium with a refractive index of 1.47)
(Converted to a refractive index of 1.52, 55.7 ° (= θ ₀ )) Under these conditions, the secondary light does not generate much secondary light from the original (at least not at the right side from the center, but at the left end (s
inθ ₂ = −0.87> −1). Therefore, even if the reproduced product was reproduced with white light, there was little observation of stray light due to the effect. At this time, if the replication wavelength is set to 647 nm, for example,
No secondary light is generated over the entire area of the original lens (sin θ ₂ = −
1.17 ≦ -1).

Although the hologram duplication method of the present invention and the hologram duplicated by the method have been described based on the principle and the embodiments, the present invention is not limited to these, and various modifications are possible.

[0028]

As is clear from the above description, according to the hologram duplication method of the present invention and the hologram duplicated by the method, no high-order light is generated in the reproduction of the original, so that the original is reproduced using the original. However, undesired interference fringes are not recorded on the duplicated product, and even if the duplicated product is reproduced, unnecessary stray light does not occur and diffraction efficiency does not decrease. Alternatively, in reproducing the original, the intensity of high-order light can be reduced, so that even if the original is duplicated, the degree of recording of unwanted interference fringes on the duplicate is low, and unnecessary stray light is unnecessary even if the duplicate is reproduced. Is weak, and there is almost no decrease in diffraction efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining diffraction by a diffraction grating for explaining the principle of the present invention.

FIG. 2 is a diagram for explaining the influence of the thickness of an amplitude grating in the present invention.

FIG. 3 is a diagram showing design conditions of a comparative example and the first embodiment.

FIG. 4 is a diagram illustrating a copy condition according to the first embodiment.

FIG. 5 is a diagram showing design conditions of Example 2.

FIG. 6 is a diagram illustrating a relationship between a replication wavelength and a diffraction angle at which a simple diffraction grating obtained by replication has a specific slant angle.

FIG. 7 is a cross-sectional view for explaining a conventional duplication method.

FIG. 8 is a diagram schematically showing diffracted light generated from a hologram.

FIG. 9 is a sectional view of a liquid crystal display device using a hologram color filter.

FIG. 10 is a diagram schematically showing interference fringes of a minute hologram constituting a hologram color filter.

[Explanation of symbols]

 Reference Signs List 30: Amplitude diffraction grating (original) 31: Incident side medium 32: Outgoing side medium (photosensitive material) 33: Incident light 30 ': Line part (opaque part) 30 ": Space part

[Procedure amendment]

[Submission date] June 9, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

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Claims (4)

[Claims] 1. A method of optically copying a hologram or diffraction grating of an original onto a photosensitive material, wherein sin [φ + sin ⁻¹ {λ / (2n cos φ)}] + λ / (n （) ≧ 1 (13) And sin [φ + sin ^-1 ｛λ / (2nΛcosφ)｝]-2λ / (nΛ) ≦ -1 (14) where Λ: one of the surface pitches of the original plate, n: photosensitive A method of replicating a hologram, wherein the hologram is replicated with a light beam having a wavelength λ that satisfies the following: average refractive index of a material, φ: target fringe angle when recording a duplicate. 2. A method of optically copying a hologram or diffraction grating of an amplitude type master onto a photosensitive material, wherein sin [φ + sin ⁻¹ {λ / (2nΛcosφ)}] + λ / (nΛ) ≧ sinα ... ( 15) And sin [φ + sin ⁻¹ {λ / (2nΛcosφ)}] − 2λ / (nΛ) ≦ −sinα (16) where α = tan ⁻¹ (rdΛ / t), Λ: amplitude type One of the surface pitches of the master, n: average refractive index of the photosensitive material, φ: target fringe angle when recording a duplicate, d: average duty ratio (space / pitch) of the amplitude type master, t: an average film thickness of a line portion (opaque portion) of the amplitude type master; r: a value satisfying 0.5 ≦ r ≦ 1; 3. The hologram duplicating method according to claim 1, wherein the hologram of the original comprises an array of elementary holograms condensed at a position of a fixed focal length. 4. A hologram copied by the hologram copying method according to claim 1.