JP2001337584A - Computer hologram and reflection type liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a computer hologram observable in white in a desired observation region and a reflection type liquid crystal display device using it as a reflecting plate. SOLUTION: The computer hologram 1 which spreads incident light of prescribed reference wavelength λsta being made incident with a prescribed incident angle θ in a specific angle range, with respect to zero-order transmitted light or zero-order reflected light being made incident with the incident angle θ, is constituted so that the maximum angle of diffraction β2min of the incident light with the incident angle θ of the minimum wavelength λmin in a wavelength range λmin-λmax which looks white when additive mixture of colors are performed, including the reference wavelength λsta, becomes larger than the minimum angle of diffraction β1max of the incident light with the incident angle θof the longest wavelength λmax in the wavelength range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer generated hologram and a reflection type liquid crystal display device using the same, and more particularly, to a computer generated hologram which can be observed in white in a desired observation area and a reflection type liquid crystal using the same as a reflection plate. The present invention relates to a display device.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a computer generated hologram which can be used as a reflection diffuser by being arranged on the back of a reflection type liquid crystal display device. For example, Japanese Patent Application Laid-Open No. H11-296054 proposes a computer generated hologram having a phase distribution that diffracts light incident at a predetermined oblique incident angle into a predetermined observation region.

[0003]

The problem to be solved by the present invention is disclosed in JP-A-11-29.
The computer generated hologram proposed in Japanese Patent No. 6054 is a type in which a reflective layer is provided on a relief pattern, or a transmission type hologram, so that diffraction occurs in a wide wavelength range. For this reason, when the observation area is set to be narrow for the purpose of improving brightness or the like, there is a problem that the color observed at each observation position changes due to a difference in the diffraction angle depending on the wavelength.

The present invention has been made in view of such problems of the prior art, and has as its object to provide a computer-generated hologram which can be observed in white in a desired observation area and a reflection type liquid crystal using the same as a reflection plate. It is to provide a display device.

[0005]

According to the present invention, there is provided a computer generated hologram for diffusing incident light of a predetermined reference wavelength incident at a predetermined angle of incidence into a specific angle range. The maximum diffraction angle of the incident light at the incident angle of the shortest wavelength in the wavelength range in which the zero-order transmitted light or the zero-order reflected light enters at the minimum wavelength in the wavelength range that appears white when additive color mixing is performed, including the reference wavelength, is the wavelength range. Is larger than the minimum diffraction angle of the incident light having the longest wavelength and the incident angle.

In this case, the computer generated hologram is 2
A computer-generated hologram composed of a collection of minute cells arranged in a two-dimensional array, the cells each having an optical path length that gives a unique phase to reflected light or transmitted light, and A first phase distribution in which a vertically incident light beam is substantially diffracted into a predetermined observation area and is not substantially diffracted outside the observation area, and a light beam that is obliquely incident at a predetermined incident angle is vertically It may have a phase distribution obtained by adding a second phase distribution that emits light.

Further, the computer generated hologram is a computer generated hologram composed of an aggregate of minute cells arranged two-dimensionally in an array, and each cell has a unique phase with respect to reflected light or transmitted light. A given optical path length, the phase distribution of which is such that a light beam that is obliquely incident at a predetermined angle of incidence is substantially diffracted into a predetermined observation area, but is not substantially diffracted outside the observation area. A phase that is such that it is substantially diffracted into another area where the position of the predetermined observation area is shifted, and is not substantially diffracted outside the other area. It may have a distribution.

Further, it is realistic that the cells are arranged in a grid pattern vertically and horizontally.

[0009] A reflection type computer generated hologram in which an uneven relief pattern is provided on the surface of the substrate and a reflection layer is provided thereon may be used.

The shortest wavelength is 450 nm,
It may be configured such that the longest wavelength is 650 nm.

The incident angle of the illumination light is θ, and the shortest wavelength is λ.
_min and the longest wavelength is λ _max , the reference wavelength λ _sta
It is _desirable that the minimum diffraction angle β _1sta and the maximum diffraction angle β _{2sta satisfy} λ _min / λ _max ≧ (sin _β 1sta _−sin θ) / (sin _β 2sta _−sin θ) (3).

The shortest wavelength is λ _min , and the longest wavelength is λ
_When the minimum diffraction angle at the reference wavelength λ _sta is β _1sta and the maximum diffraction angle is β _2sta , the incident angle θ is sin θ ≧ (λ _max sin β _1sta -λ _min sin _{β 2sta} ) / (λ _max −λ _min ) It is desirable to satisfy (4).

A display device according to the present invention is characterized in that the above-mentioned computer generated hologram is used as a reflection plate.

Further, the reflection type liquid crystal display device of the present invention is characterized in that the above-mentioned computer generated hologram is arranged on a back surface as a reflection plate.

Another reflection type liquid crystal display device according to the present invention is characterized in that the above-mentioned computer generated hologram is arranged as a reflection plate between a liquid crystal layer and a back substrate.

In the present invention, the zero-order transmitted light or the zero-order reflected light that is incident at a predetermined incident angle includes the reference wavelength and has the shortest wavelength in the wavelength range that appears white when additive color mixing is performed. Since the maximum diffraction angle of the incident light is configured to be larger than the minimum diffraction angle of the incident light at the incident angle at the longest wavelength in the wavelength range, the maximum diffraction angle at the shortest wavelength and the minimum diffraction angle at the longest wavelength are set. It can be observed in white in the angle range of the angle, and the observed color does not change even if the viewpoint is moved in the angle range, and is suitable for a reflection plate or the like of a reflection type liquid crystal display device.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A computer generated hologram according to the present invention is disclosed in Japanese Patent Application Laid-Open No. 11-183716 or Japanese Patent Application Laid-Open No. 11-29.
It is based on a computer generated hologram obtained based on No. 6054. These computer generated holograms will be briefly described.

A computer generated hologram based on Japanese Patent Application Laid-Open No. 11-183716 is described in the claims, and is a computer generated hologram composed of an aggregate of minute cells arranged two-dimensionally in an array. The cell has an optical path length that gives a unique phase to each of the reflected light and the transmitted light, and substantially diffracts a vertically incident light beam into a predetermined observation area and out of the observation area. Has a phase distribution obtained by adding a first phase distribution that does not substantially diffract and a second phase distribution that vertically emits a light beam that enters obliquely at a predetermined incident angle. It is characterized by doing.

Here, the first phase distribution is a phase distribution φ _HOLO of a computer _generated hologram that diffracts light only to a predetermined observation area when illuminated with parallel light perpendicular to the hologram surface,
This is a phase distribution φ _HOLO as exemplified in FIG. The second phase distribution is a phase distribution φ obtained by approximating a phase distribution (dashed line in the figure) of a phase diffraction grating that diffracts light incident from behind at an incident angle θ in the front direction to a digital step-like function.
_GRAT , and a phase distribution φ as exemplified in FIG.
_GRAT . This phase distribution phi _HOLO and phase grating phase distribution phi _GRAT and phase distribution of a computer hologram phi formed by adding up is a phase distribution of a computer generated hologram based on JP-A-11-183716, in FIG. 5 (c) The phase distribution φ becomes as illustrated. The computer generated hologram having the phase distribution φ is a computer generated hologram that diffracts light incident obliquely from behind at an incident angle θ to a predetermined front observation area.

The actual depth distribution of the hologram is obtained from the phase distribution thus obtained, which differs between the reflection type and the transmission type. The φ (x, y) of FIG. 5C is calculated based on the following equation (8a) for the reflection type and the depth D of the computer generated hologram for the transmission type based on the following equation (8b).
(X, y).

D (x, y) = λφ (x, y) / (4π) (8a) D (x, y) = λφ (x, y) / {2π (n ₁ −n ₀ )} (8b) Here, λ is the center wavelength used, and n ₁ and n ₀ are the refractive indexes of the two materials constituting the transmission hologram.

In the case of the reflection type, as shown in the sectional view of FIG.
A relief pattern 11 having a depth of (x, y) is formed, and a reflective layer 1 made of aluminum or the like is formed on the relief pattern 11.
2, the computer generated hologram 1 based on JP-A-11-183716 is obtained. In case of transmission type,
As shown in the sectional view of FIG. 6B, a computer generated hologram 1 based on JP-A-11-183716 is formed by forming a relief pattern 11 having a depth of D (x, y) obtained by the above equation (8b). Is obtained. FIG. 7 shows a plan view of the computer generated hologram 1. The computer generated hologram 1 is composed of an aggregate of small cells 13 having a vertical and horizontal dimension of Δ arranged in a grid pattern of N × M (16 × 16 in FIG. 7). 8a) or (8b)
Has a depth D (x, y) given by

A computer generated hologram based on Japanese Patent Application Laid-Open No. 11-296054 is a computer generated hologram composed of an aggregate of minute cells arranged two-dimensionally in an array, and the cells generate reflected light or transmitted light. In contrast, each phase has an optical path length that gives a unique phase, and the distribution of the phase obliquely diffracts a light beam incident at a predetermined incident angle from obliquely into a predetermined observation region, and substantially deviates outside the observation region. Has a phase distribution such that it does not diffract, and diffracts a vertically incident light beam substantially into another area where the position of the predetermined observation area is shifted, and substantially outside the other area. Has a phase distribution that does not cause diffraction.

That is, first, when the hologram surface is illuminated with parallel light from behind, the amplitude ImgAmp
Are substantially constant, u ₀ ≦ u ≦ u ₁ , v ₀ ≦ v ≦ v
Rather than _one, then it shifted _{u 0 '≦ u ≦ u 1} ', v
Designate a computer generated hologram such that it is specified within the range of ₀ ′ ≦ v ≦ v ₁ ′ and becomes substantially 0 outside the region ((u, v) is coordinates on the reproduction image plane). That is, as shown in FIG. 8A, when the illumination light 3 ′ that is vertically parallel is incident,
The computer generated hologram 1 that diffracts light only in the range of u ₀ ′ ≦ u ≦ u ₁ ′ and v ₀ ′ ≦ v ≦ v ₁ ′ is designed. Assuming that the distribution of the phase HoloPha of the computer generated hologram 1 is a diffraction grating, the diffraction by the computer generated hologram 1 is represented by a basic expression of the diffraction grating, sin θ _d −sin θ _i = mλ / d (7) Here, m is the diffraction order, d is the pitch of the diffraction grating, λ is the wavelength, θ _i is the incident angle, and θ _d is the diffraction angle.
From design conditions, θ _i = 0 and α ₀ ′ ≦ θ _d ≦ α ₁ ′. Here, α ₀ ′ is u ₀ ′ of the reproduced image plane 2 from the incident position.
Α ₁ ′ is the angle of diffraction at the position of u ₁ ′.

The computer generated hologram 1 has an incident angle θ
FIG. 8 (b) shows a case where the illumination light 3 obliquely parallel is incident. From the diffraction equation (7), in this case, θ _i = θ, and if the case in the figure is positive, the range α ₀ ≦ θ of the diffraction angle θ _{d
If d} ≤ α ₁ is considered including the sign, α ₀ '≤ θ _d ≤ α ₁ '
8B, the diffraction range u ₀ ≦ u ≦ u ₁ (u
₀ is the position where the diffracted light is incident on the reproduction image plane 2 at the diffraction angle α ₀ from the incident position, and u ₁ is the position where the diffracted light is incident at the diffraction angle α ₁ ) in a direction substantially in front of the computer generated hologram 1.
The same applies to the v direction.

As described above, Japanese Patent Application Laid-Open No. H11-296054
The computer-based hologram based on the
When a parallel light is incident perpendicularly to the specified observation area in front
(U ₀≤u≤u₁, V₀≦ v ≦ v₁) Shifts position
Another area (u₀′ ≦ u ≦ u₁’, V₀′ ≦ v
≤v₁’) Is a computer generated hologram that diffracts into
When parallel light is obliquely incident on the hologram surface from behind
A predetermined observation area (u₀≤u≤u₁, V₀≦ v ≦ v
₁2) is a computer generated hologram diffracting into ()

Also in this case, based on the obtained phase distribution (x, y), based on equation (8a) for the reflection type and based on equation (8b) for the transmission type, as shown in FIG. By converting to the depth D (x, y) of the computer generated hologram, FIG.
A computer generated hologram 1 as shown in FIG.

As described above, Japanese Patent Application Laid-Open No.
The computer-generated hologram based on 183716 or JP-A-11-296054 substantially diffracts illumination light having a reference wavelength λ _sta obliquely incident at a predetermined incident angle θ into a predetermined observation region, and substantially diffracts light outside the observation region. This is a computer generated hologram having a phase distribution that does not cause diffraction. Hereinafter, for the sake of simplicity, it is assumed that the direction of incidence of the illumination light is the vertical direction, the illumination light is vertically incident in the horizontal direction, and diffracted from the computer generated hologram to a substantially symmetric range in the horizontal direction. Further, the computer hologram based on the premise of the present invention may be of a transmission type or a reflection type.

First, how the reproduction light is observed when the wavelength of the illumination light changes when the observation region of the computer generated hologram is narrow and wide will be described.

FIG. 1 conceptually shows how the observation area changes with wavelength in the case of the computer generated hologram 1 in which the observation area is set narrow. And some reference wavelength lambda _sta of the illumination light 3 between the shortest wavelength lambda _min and the longest wavelength lambda _max, computer-generated hologram 1 has been designed for the reference wavelength lambda _sta. As shown in FIG. 1B, at the reference wavelength λ _sta ,
The incident angle θ of a certain oblique (angle, at an angle from the normal line of the hologram 1, the angle of counterclockwise is positive.) Angle range of the illumination light 3 is near the front incident at _β 1sta ~β 2sta (subscript 1 Is the minimum diffraction angle, and the suffix 2 is the maximum diffraction angle, where the minimum diffraction angle is the diffraction angle of the diffracted light that forms the minimum angle with respect to the zero-order transmitted light, and the maximum diffraction angle is the zero-order transmitted light. When the illumination light 3 having the shortest wavelength λ _min is incident at the same oblique incident angle θ, the computer generated hologram 1 is set to spread out as the diffracted light 4 _sta within the maximum diffraction angle of the diffracted light.
Since it is considered as a set of phase diffraction gratings, as shown in FIG. 1 (a), the observation region where the diffraction light 4 _min is incident (angle range β _1min ~β _2min) is lower than the reference wavelength lambda _sta (0th transmitted light side). When the incident illumination light 3 of the longest wavelength lambda _max at an incident angle of the same oblique theta, as shown in FIG. 1 (c), the observation region (angular range where the diffraction light 4 _{ma x} is incident β
_{1max to} β _2max ) are higher (0) than the case of the reference wavelength λ _sta.
(The side opposite to the next transmitted light side). Note that the distribution of the diffracted light as described above is in a plane including the normal line of the hologram 1 and the illumination light 3, and in a plane including the normal line of the hologram 1 and orthogonal to the plane, the illumination light 3 is distributed. Are considered in the case where diffracted light is distributed on both sides.

At this time, as shown in FIG. 2, since there is no portion where all of the diffracted lights 4 _min , 4 _sta and 4 _max overlap, all wavelengths can be observed simultaneously and the wavelength range λ _{min to} λ
_{When sta to} λ _max is in the visible light range, there is no region that can be observed in white, and the observed color changes depending on the observation position (angle).

FIG. 3 conceptually shows how the observation area changes with wavelength in the case of the computer generated hologram 1 in which the observation area is set wide. In this case as in the case also observed region of FIG. 1 is narrow, when the incident shortest wavelength lambda _min and longest wavelength lambda _max (Fig 3 (a), (c) ), the observation region (angle range β _1min ~β _2min, β _1max ~β _2max) is compared with the case of the reference wavelength lambda _sta, lower respectively, shifted upward. However, since the observation area is wide, as shown in FIG. 4, the diffracted light 4 _min,
4 _sta , near the front where all 4 _max overlap 5 (angle range β
When observed in _{1max ~β 2min),} it is possible to observe all wavelengths simultaneously. As long as the observer moves in the region 5 where all wavelengths can be observed at the same time, almost no change in the observed color is felt.

The conditions for this so that the regions 5 of all wavelengths observable assuming there, as is clear from FIG. 4, the maximum diffraction angle beta _{2m in} the shortest wavelength lambda _min of the assumed wavelength range _{That is,} it is larger than the minimum diffraction angle β _1max of the longest wavelength λ _max . Diffracted light 4 _min , 0th order transmitted light, 4 _{min
When sta} and 4 _max are distributed opposite to those in FIGS. 1 to 4, this relationship is reversed, so that, with reference to the 0th-order transmitted light, the maximum of the shortest wavelength λ _min formed with respect to the 0th-order transmitted light It is true to say that the diffraction angle β _2min is greater than the minimum diffraction angle β _1max of the longest wavelength λ _max.

[0034] For observable overlap all wavelengths in white, λ _min = 450nm, it is sufficient if λ _{ma x} = 650nm. Therefore, at least the shortest wavelength λ
_min = 450 nm maximum diffraction angle β _2min is the longest wavelength λ _max
= In the minimum diffraction angle beta _{1 m} larger computer hologram 1 than _ax of 650 nm, as long as observed in region 5 is observable white no color change.

[0035] From the above, in some observation area, if you want to observe all of the desired wavelength, it can be seen it Re determining an observation area _β 1sta ~β 2sta reference wavelength lambda _sta the following procedure. (A) The incident angle θ of the illumination light 3 for reproduction is determined. (A) A desired observation angle range 5 that looks white is determined. That is, the minimum diffraction angle γ ₁ (= β _1max ) to the maximum diffraction angle γ ₂
(= Β _2min ).

Here, the minimum diffraction angle γ ₁ and the maximum diffraction angle γ ₂
Is the diffraction angle that forms the minimum and maximum angles with respect to the zero-order transmitted light. In the case of the distributions of FIGS. 1 to 4, θ <γ ₁ ≦ γ
_In the case where diffracted light is distributed in a manner opposite to that shown in FIGS. 1 to 4, the relationship is θ> γ ₁ ≧ γ ₂ . (C) Determine a desired observation wavelength (shortest wavelength λ _min to longest wavelength λ _max ). (D) The reference wavelength λ _sta is determined in the range of λ _min ≦ λ _sta ≦ λ _max . (E) Based on the diffraction equation (7), the minimum diffraction angle β _1sta at the reference wavelength λ _sta is obtained from the minimum diffraction angle γ ₁ and the longest wavelength λ _max using the following equation (1).

(Sinγ ₁ −sin θ) / λ _max = (sin _β 1sta _−sin θ) / λ _sta sin β _1sta = sin θ + (sin γ ₁ −sin θ) × λ _sta / λ _max (1) Similarly, Based on the diffraction equation (7), the maximum diffraction angle β _2sta at the reference wavelength λ _sta is determined from the maximum diffraction angle γ ₂ and the shortest wavelength λ _min using the following equation (2).

[0038] _{(sinγ 2 -sinθ) / λ min} = and _{(sinβ 2sta -sinθ) / λ sta} sinβ 2sta = sinθ + (sinγ 2 -sinθ) × λ sta / λ min ··· (2), the incident illumination light At an angle θ and a reference wavelength λ _sta ,
By making the computer generated hologram 1 based on JP-A-11-183716 or JP-A-11-296054 so that the minimum diffraction angle β _1sta and the maximum diffraction angle β _2sta are obtained, the incident angle of the illumination light 3 for reproduction is obtained. θ, the observation angle γ
Diffusion hologram visible wavelength lambda _min to [lambda] _max is observable white obtained in the range of ₁ to? _2.

The above is the description of the desired incident angle θ of the illumination light and the diffraction range.
Circumference γ₁~ Γ_Two, Wavelength range λ_min~ Λ _maxWhen given
Of diffraction angle range β used for calculation_1sta~ Β_2staHow to find
It is.

On the other hand, the reference wavelength λ_sta, Illumination light incident angle θ
The minimum diffraction angle β_1sta, Maximum diffraction angle β_2staGiven
The wavelength range λ_min~ Λ_maxWatching the light of
The condition for the presence of an observable and white area
Long wavelength λ_maxMinimum diffraction angle β _1max= Γ₁And the shortest wavelength λ
_minMaximum diffraction angle β_2min= Γ_TwoAnd using
Given to. (1) When the diffracted light exists on the positive side with respect to the zero-order transmitted light
(FIGS. 1 to 4), γ_Two≧ γ₁ sinγ_Two≧ sinγ₁ Using equations (1) and (2), sin θ + (sin β_2sta−sin θ) × λ_min/ Λ_sta ≧ sinθ + (sinβ_1sta−sin θ) × λ_max/ Λ_sta (Sinβ_2sta−sin θ) × λ_min ≧ (sinβ_1sta−sin θ) × λ_max sinβ_2sta> Sin θ, λ_min/ Λ_max ≧ (sinβ_1sta−sin θ) / (sin β_2sta−sin θ) (3) (2) When the diffracted light exists on the negative side with respect to the zero-order transmitted light
If (opposite to FIGS. 1-4), γ_Two≤γ₁ sinγ_Two≤sinγ₁ Using equations (1) and (2), sin θ + (sin β_2sta−sin θ) × λ_min/ Λ_sta ≤sinθ + (sinβ_1sta−sin θ) × λ_max/ Λ_sta (Sinβ_2sta−sin θ) × λ_min ≤ (sinβ_1sta−sin θ) × λ_max sinβ_2sta<Sin θ, λ_min/ Λ_max ≧ (sinβ_1sta−sin θ) / (sin β_2sta−sin θ) (3) Therefore, Expression (3) indicates that the diffracted light is on either the positive side or the negative side.
It is also an equation that holds.

[0041] The equation (3), the incident angle of the illumination light theta, a desired observed when the wavelength range was set lambda _min to [lambda] _max, the equation diffraction angle range _β 1sta ~β 2sta at a reference wavelength lambda _sta If the setting is made so as to satisfy (3), the range γ in which all desired observation wavelength ranges λ _{min to} λ _max can be simultaneously observed.
Which means that _{the 1 ~γ 2} is present.

By transforming equation (3), sin θ ≧ (λ_maxsinβ_1sta−λ_minsinβ_2sta) / (Λ_max−λ_min) (4) This equation (4) gives the desired observation wavelength range λ_min~
λ_max, A reference wavelength λ _staDiffraction angle range β at
_1sta~ Β_2staSatisfies this equation (4)
Only when the incident angle θ of the illumination light is set as described above,
Observation wavelength range λ_min~ Λ_maxAll can be observed simultaneously
Circumference γ₁~ Γ_TwoMeans that there is.

In the above description, only the plane including the normal line of the hologram 1 and the illumination light 3 is considered. However, in a plane including the normal line of the hologram 1 and perpendicular to the plane, the light is diffracted to both sides of the illumination light 3. Since it is assumed that light is distributed, in this in-plane direction, the distribution range at the shortest wavelength λ _min is a region where white observation is possible, and the range is the observation region at the reference wavelength λ _sta. Is obtained by conversion in the same manner as

By using such a computer generated hologram 1 as, for example, the reflection diffuser plate 31 of the reflection type liquid crystal display device shown in FIG. 9, the illumination light 32 incident from the display side of the liquid crystal display element 40 is directed to a predetermined front side. Diffuse reflection is performed only in the observation area, and a bright white display can be performed in a bright place without using a self-luminous backlight. In FIG. 9, the liquid crystal display element 40 includes, for example, two glass substrates 4.
A liquid crystal layer 45 made of twisted nematic or the like sandwiched between the first and second glass substrates 42. A uniform transparent counter electrode 44 is provided on the inner surface of one glass substrate 42, and the other glass substrate 41
On the inner surface, a transparent display electrode 43 and a black matrix (not shown) are provided independently for each pixel. In the case of a color display device, a transparent display electrode 43, a color filter, and a black matrix are independently provided on the inner surface of the other glass substrate 41 for each of the liquid crystal cells R, G, and B. Further, an alignment layer (not shown) is provided on the liquid crystal layer 45 side of the electrodes 43 and 44.
A polarizing plate 46 is attached to the outer surface of the glass substrate 42, and a polarizing plate 47 is attached to the outer surface of the glass substrate 42 on the side opposite to the observation side. For example, the transmission axes are arranged so as to be orthogonal to each other. I have. By controlling the voltage applied between the transparent display electrode and the transparent counter electrode of such a liquid crystal display element 40 to change the transmission state, numerals, characters, symbols,
A picture or the like can be selectively displayed. The reflection / diffusion plate 31 is composed of the computer generated hologram 1 according to the present invention having a configuration as shown in FIG. 6A, and the reflection / diffusion plate 31 is arranged on the side opposite to the viewing side of the liquid crystal display element 40.
Illumination light 32 having a desired observation wavelength range λ _{min to} λ _max incident from the display side of the liquid crystal display element 40 is diffusely reflected forward by the reflective diffuser plate 31 arranged on the rear surface thereof, and is self-luminous in a bright place. White display can be performed without using a backlight.

Further, as shown in FIG. 10, the computer generated hologram 1 according to the present invention may be arranged as a reflector between the liquid crystal layer 45 of the reflection type liquid crystal display device and the rear substrate 42 '. In this case, the reflective layer 12 of the computer generated hologram 1 also functions as the light reflective electrode 44 '.

Next, one specific embodiment will be described.
As the computer generated hologram 1 having the characteristics shown in FIG.
FIG. 11 shows the phase distribution HoloPha of the hologram surface when the image is divided into 2 × 32 grid cells and the reproduced image plane for angle display is similarly divided into 32 × 32 grid cells. . This computer generated hologram 1 sets the phase of each cell to -π.
The range between. +-. Pi. Is quantized in 16 steps. Based on Japanese Patent Application Laid-Open No. 11-296054, the design wavelength is 500 nm.
Are illuminated perpendicularly. FIG. 12 shows the amplitude distribution ImgAmp on the reproduced image plane at the time of normal incidence. Diffracted light is distributed in a desired 6 × 5 range.

In this computer generated hologram 1, the incident angle θ = −
Reference wavelength λ _sta = 5 when changed to 35 ° and illuminated
FIG. 13 shows the amplitude distribution ImgAmp on the reproduced image plane in the case of 00 nm.
Shown in The diffracted light is distributed on the lower side than at the time of 0 ° incidence in FIG.

This computer generated hologram 1 has an incident angle θ = −3.
FIG. 14 shows the amplitude distribution ImgAmp on the reproduced image plane when the shortest wavelength λ _min = 400 nm at 5 °. Lower than the reference wavelength λ _{st a} = 500 nm in FIG. 13 (0-order transmitted light side)
Are diffracted light.

When the incident angle θ = −35 °, the longest wavelength λ
Amplitude distribution ImgAmp on the reproduced image plane when _max = 700 nm
Is shown in FIG. The reference wavelength λ _sta = 500 nm in FIG.
The diffracted light is distributed above (at the side opposite to the zero-order transmitted light).

FIG. 16 is a diagram in which the visual ranges, which are the distribution ranges of the diffracted light in FIGS. 13 to 15, are schematically superimposed.
The vertical diffraction angle is represented by β _y , and the horizontal diffraction angle is represented by β _x . As is clear from this figure, the wavelength range of 400 nm
The viewing range in which light of all wavelengths can be seen in the vertical direction at ~ 700 nm is between the maximum diffraction angle of the shortest wavelength and the minimum diffraction angle of the longest wavelength in the wavelength range. In the horizontal direction, the diffraction angle is the shortest wavelength range.

The above embodiment is merely an example for showing that the computer generated hologram 1 of the present invention can be specifically calculated. To construct an actual computer generated hologram 1, the number of cells must be reduced. The calculation is performed with an increase in the number of digits.

Although the computer generated hologram according to the present invention has been described based on the principle and the embodiment, the present invention is not limited thereto, and various modifications are possible. In addition, the computer generated hologram of the present invention is not limited to a reflection plate for a reflection type liquid crystal display device.
For example, it can be used for a reflector for display or the like. In addition, the computer generated hologram of the present invention may be configured as a transmissive plate without the reflective layer 12 in addition to the reflective plate.

[0053]

As is apparent from the above description, according to the computer generated hologram of the present invention, the case where the 0-order transmitted light or the 0-order reflected light incident at a predetermined incident angle includes the reference wavelength and is additively mixed. Since the maximum diffraction angle of the incident light at the incident angle at the shortest wavelength in the wavelength range that looks white is larger than the minimum diffraction angle at the incident light at the incident angle at the longest wavelength in the wavelength range. It can be observed in white in the angle range of the maximum diffraction angle of the shortest wavelength and the minimum diffraction angle of the longest wavelength, and the observed color does not change even if the viewpoint is moved in that range. It is suitable for a reflection plate or the like of a display device.

[Brief description of the drawings]

FIG. 1 is a diagram conceptually showing how an observation region changes with wavelength in the case of a computer generated hologram in which the observation region is set narrow.

FIG. 2 is a diagram conceptually showing that there is no white observable region in the case of FIG. 1;

FIG. 3 is a diagram conceptually showing a state of a change in an observation area depending on a wavelength in a case of a computer generated hologram in which an observation area is set widely.

FIG. 4 is a diagram conceptually showing that a computer-readable hologram of FIG. 3 has an area that can be observed in white.

FIG. 5 is a diagram for explaining a configuration of a first computer generated hologram as a premise of the present invention.

FIG. 6 is a sectional view showing a configuration of a computer generated hologram of the present invention.

FIG. 7 is a plan view of a computer generated hologram according to the present invention.

FIG. 8 is a diagram showing a comparison of diffraction ranges of a second computer generated hologram, which is a premise of the present invention, in the case of vertical illumination and oblique illumination.

FIG. 9 is a cross-sectional view illustrating a configuration of a reflective liquid crystal display device according to the present invention.

FIG. 10 is a cross-sectional view showing the configuration of another reflective liquid crystal display device to which the computer generated hologram reflector according to the present invention is applied.

FIG. 11 is a diagram showing a phase distribution of a hologram surface of a computer generated hologram according to one embodiment of the present invention.

12 is a diagram showing an amplitude distribution on a reproduction image plane at the time of vertical illumination at a design wavelength of the computer generated hologram of the embodiment in FIG. 11;

FIG. 13 is a diagram showing an amplitude distribution on a reproduced image plane in the case of oblique illumination at a reference wavelength of the computer generated hologram of the embodiment in FIG. 11;

FIG. 14 is a diagram showing an amplitude distribution on a reproduced image plane in the case of oblique illumination at the shortest wavelength of the computer generated hologram of the embodiment in FIG. 11;

FIG. 15 is a diagram showing an amplitude distribution on a reproduction image plane in the case of oblique illumination at the longest wavelength of the computer generated hologram of the embodiment in FIG. 11;

FIG. 16 is a diagram in which viewing zones, which are distribution ranges of diffracted light in FIGS. 13 to 15, are schematically superimposed.

[Explanation of symbols]

_{DESCRIPTION OF SYMBOLS} 1 ... Computer hologram 2 ... Reconstructed image plane 3 ... Illumination light 3 '... Illumination light 4 _sta ... Reference wavelength diffracted light 4 _min ... Shortest wavelength diffracted light 4 _max ... Longest wavelength diffracted light 5 ... Observe all wavelengths simultaneously Possible area 10 ... Substrate 11 ... Relief pattern 12 ... Reflective layer 13 ... Cell 31 ... Reflection diffuser 32 ... Illumination light 40 ... Liquid crystal display element 41, 42 ... Glass substrate 43 ... Transparent display electrode 44 ... Transparent counter electrode 45 ... Liquid crystal Layers 46, 47: Polarizing plate 42 ': Back substrate 44': Reflective electrode

Continued on the front page F-term (reference) 2H049 AA03 AA07 AA25 AA50 AA60 AA65 CA01 CA05 CA08 CA09 CA16 CA22 2H091 FA02Y FA08X FA14Y FA19Y FA31Y FA35Y LA16 LA20 2K008 AA00 EE04 FF11 FF27 5G435 AA04 BB12FF

Claims (11)

[Claims] 1. A computer generated hologram for diffusing incident light of a predetermined reference wavelength incident at a predetermined incident angle into a specific angle range, wherein a zero-order transmitted light or a zero-order reflected light incident at the incident angle is The maximum diffraction angle of the incident light at the incident angle of the shortest wavelength in the wavelength range that looks white when additive color mixing is performed including the reference wavelength is smaller than the minimum diffraction angle of the incident light at the incident angle at the longest wavelength in the wavelength range. A computer generated hologram configured to be large. 2. The computer-generated hologram according to claim 1, wherein the computer-generated hologram is a computer-generated hologram composed of an aggregate of minute cells arranged two-dimensionally in an array, and each of the cells has a unique phase with respect to reflected light or transmitted light. Have a given optical path length,
In addition, a first phase distribution such that a vertically incident light beam is substantially diffracted into a predetermined observation region and is not substantially diffracted outside the observation region, and a light beam that is obliquely incident at a predetermined incident angle. 2. The computer generated hologram according to claim 1, wherein the computer generated hologram has a phase distribution obtained by adding a second phase distribution which is emitted vertically. 3. The computer generated hologram according to claim 1, wherein the computer generated hologram is an aggregate of minute cells arranged two-dimensionally in an array, and each of the cells has a unique phase with respect to reflected light or transmitted light. Have a given optical path length,
The phase distribution is such that the light beam obliquely incident at a predetermined angle of incidence is substantially diffracted into a predetermined observation area, and is not substantially diffracted outside the observation area, and is perpendicularly incident. A phase distribution that substantially diffracts the luminous flux into another region in which the position of the predetermined observation region is shifted, and does not substantially diffract outside the another region. The computer generated hologram according to claim 1, wherein 4. The computer generated hologram according to claim 2, wherein the cells are arranged in a grid pattern in the vertical and horizontal directions. 5. The computer generated hologram according to claim 1, wherein an uneven relief pattern is provided on a surface of the substrate, and a reflective layer is provided thereon. 6. The shortest wavelength is a wavelength of 450 nm,
The computer generated hologram according to claim 1, wherein the longest wavelength is configured to be 650 nm. 7. The incident angle of illumination light is θ, and the shortest wavelength is λ.
_min, wherein the longest wavelength is taken as lambda _max, the minimum diffraction angle beta _1STA in the reference wavelength lambda _sta, the maximum diffraction angle beta _2Sta
Satisfies λ _min / λ _max ≧ (sin _β 1sta _−sin θ) / (sin _β 2sta _−sin θ) (3).
Computer hologram described in the item. 8. The minimum wavelength is λ _min , the longest wavelength is λ _max , and the minimum diffraction angle at the reference wavelength λ _sta is β.
_1sta and the maximum diffraction angle is β _2sta , the incident angle θ
Satisfies: sin θ ≧ (λ _max sin β _1sta −λ _min sin β _2sta ) / (λ _max −λ _min ) (4)
Computer hologram described in the item. 9. A display device using the computer generated hologram according to claim 1 as a reflecting plate. 10. A reflection type liquid crystal display device, wherein the computer generated hologram according to claim 1 is arranged on a back surface as a reflection plate. 11. A reflection type liquid crystal display device, wherein the computer generated hologram according to claim 1 is disposed as a reflection plate between a liquid crystal layer and a rear substrate.