JPH11305041A - Hologram color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress light losses due to secondary diffraction by a stacked structure. SOLUTION: This filter is structured by stacking a hologram lens array layer 40R for red, which diffracts and spectrally diffuses mainly light of red wavelength range of incident light and converges it on corresponding pixels, a hologram lens array layer 40B for blue which diffracts and spectrally diffuses mainly light of the blue wavelength range of the incident light and converges it on corresponding pixels, and a hologram lens array layer 40G for green which diffracts and spectrally diffuses mainly light of the green wavelength range of the incident light and converged it on corresponding pixels. Each hologram lens array layers is stacked in the order of red, green, and blue from the incident light site.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram color filter having a laminated structure for diffracting, dispersing, and condensing incident light into a plurality of lights having different wavelength bands.

[0002]

2. Description of the Related Art Conventionally, in a spatial light modulator used in a color liquid crystal display device or the like, a color filter using a coloring material such as a pigment or a dye is generally used as a color separating means. These color filters selectively transmit only one of the wavelength ranges corresponding to the three primary colors of light, R (red), G (green), and B (blue), and absorb the other wavelength ranges. This filter separates white light with a filter.

Therefore, in order to extract the three primary colors of RGB, it is necessary to form color filters for R, G, and B in independent areas on the incident surface of white light, and in principle, the light transmission of the color filter itself is required. The rate is low, and it is difficult to increase the light utilization rate.

On the other hand, recently, the use of a color filter using a hologram lens as a color separation means (hereinafter referred to as a hologram color filter) has been studied.
The hologram color filter can selectively diffract light of a specific wavelength by means of the diffraction / spectral function of the hologram lens, focus the light on the corresponding pixel electrode, and transmit the other light straight.

In general, a hologram color filter includes a hologram lens array layer for B having a function of diffracting and dispersing B light, a hologram lens array layer for G having a function of diffracting and dispersing G light, and a diffracting and diffracting R light. It has a structure in which three layers of an R hologram lens array layer having a function of separating light are laminated. For example, for B from the side where light enters,
When the hologram lens array layers are stacked in the order of G and R, the white light incident on the hologram color filter at a certain angle is first diffracted and separated by the B hologram lens array layer at the B hologram lens array layer. The G light component is diffracted and split by the hologram lens array layer for R, and the R light component is diffracted and split by the hologram lens array layer for R.

[0006] Since white light is hardly absorbed by the hologram color filter itself, it is possible in principle to increase the light utilization rate as compared with the conventional color separation means using a colored filter.

[0007]

As described above, a hologram color filter generally has a structure in which hologram lens array layers for B, G, and R are stacked. Was arbitrarily determined.
If each hologram lens array layer diffracts and disperses only the corresponding color light and transmits all other wavelengths straight,
The effect of the stacking order is not very large. However, the stacking order actually affects the spectral / diffraction function of the hologram color filter, and if the stacking order is changed, the light utilization rate also changes. Therefore, a good light utilization rate cannot often be obtained.

The present invention has been made in view of the above problems, and has as its object to provide a hologram color filter having a laminated structure capable of exhibiting a high light utilization factor.

[0009]

A feature of the hologram color filter of the present invention is that a hologram lens array layer for red which mainly diffracts and disperses light in a red wavelength region of incident light and condenses it on a corresponding pixel is provided. A hologram lens array layer for blue, which mainly diffracts and disperses light in the blue wavelength region out of the incident light and focuses it on the corresponding pixel, diffracts and disperses light mainly in the green wavelength region out of the incident light, In a hologram color filter having a laminated structure including a hologram lens array layer for green light condensed on a corresponding pixel, a red (R)
Hologram lens array layers are stacked in the order of hologram lens array layers for hologram lens, green (G), and blue (B).

As described above, by specifying the stacking order of the hologram lens array layers, the first and second layers from the incident light side are diffracted in a predetermined direction so as to be condensed on the corresponding pixel electrodes. The efficiency of the second-order diffraction of the emitted light in the second or third layer can be kept low, and the efficiency of the light effectively condensed on the corresponding pixel electrode can be increased.

Alternatively, the order of lamination of the hologram lens array layers described above may be changed from the incident light side to blue (B) and red (R).
Hologram color filter laminated in the order of green (G) or green (G) and blue (B) from the incident light side
Similarly, in a hologram color filter laminated in the order of red, red, and red, the above-mentioned second-order diffraction efficiency can be maintained low, and the efficiency of light effectively condensed on the corresponding pixel electrode can be increased.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1. Structure of spatial light modulator using hologram color filter) FIG. 4 shows an apparatus showing the structure of a spatial light modulator using a hologram color filter according to an embodiment of the present invention. It is sectional drawing. This spatial light modulator is used, for example, in a reflective color liquid crystal display device.

As shown in FIG. 1, the spatial light modulator includes a liquid crystal panel 11, a thin glass layer 12, a hologram color filter 13, a glass substrate 14, and a coupling prism 1.
5 and so on.

The liquid crystal panel 11 includes a silicon substrate 21, an active matrix drive circuit 22 formed on the silicon substrate 21, and the active matrix drive circuit 22 selectively controls and drives the liquid crystal panel 11 according to a video signal. A pixel electrode 23 in which the pixel electrodes 23r, 23g, and 23b are regularly arranged; a dielectric mirror film 24;
It has a structure in which an alignment film 25, a light modulation layer 26 made of a liquid crystal layer, an alignment film 27, and a transparent common electrode layer 28 are sequentially stacked.

The hologram color filter 13 according to the present embodiment has an R hologram lens array layer 13R, G for selectively separating and diffracting R (red) light from the incident light side.
A structure in which a G hologram lens array layer 13G for selectively separating and diffracting (green) light and a B hologram lens array layer 13B for selectively separating and diffracting B (blue) light are laminated in this order. Have The hologram lens array layers are laminated in the order of B, R, and G from the incident light side, or G
The hologram lens array layers may be laminated in the order of hologram lens array layers for B, R and R.

Each hologram lens array layer 13R, 13
G and 13B disperse and diffract the selected color light in the white light (readout light), and for each lens unit, each pixel electrode 23r, 23g, and 23 corresponding to R, G, and B in the liquid crystal panel 11.
The light is condensed almost vertically to b. In the case where a dielectric mirror 24 is formed on the pixel electrode 23 as shown in FIG.
The selected color light is focused on the dielectric mirror 24 just before the pixel electrode.

The incident angle of the readout light (white light) to the hologram color filter 13 is determined by diffracting one of the two polarized light components in the readout light, for example, the S-polarized light component (a polarized light component having a vibration plane perpendicular to the incident surface). The diffraction efficiency of the other P-polarized light component (a polarized light component having a vibration plane parallel to the incident surface) is set to be the maximum, and the diffraction efficiency ratio is set to 30% or more. For example, when the incident angle is 60 degrees to 9
If it is relatively large, such as in the range of 0 degrees, it is possible to make the difference between the diffraction efficiency of the P-polarized light component and the diffraction efficiency of the P-polarized light component 30% or more while maximizing the diffraction efficiency for the S-polarized light component.

With this setting, the s-polarized light component diffracted by the hologram color filter 13 and incident on the light modulation layer 26 changes to p-polarized light when modulated by the light modulation layer 26 on the way. Is reflected and reflected by the pixel electrode 23 and passes through the hologram color filter 13 again.
The light travels substantially straight without being diffracted, and can be efficiently extracted as projection light.

The hologram color filter 13 according to the present embodiment is characterized in that the hologram lens array layers are laminated in the above-described lamination order, and the spatial light modulation element having a high light utilization factor due to this characteristic. Can be provided.

A description will now be given of the study on the second-order diffracted light performed on the laminated structure of the hologram color filter according to the embodiment of the present invention.

(2, Incident and Diffraction in Hologram Lens) The hologram color filter according to the present embodiment
As shown in FIG. 4, three hologram lens array layers are stacked. Each layer has a function of diffracting and dispersing any one of the three primary colors as main diffracted light and condensing it in a predetermined direction.However, each color light is diffracted and dispersed only by the corresponding hologram lens array layer. In other cases, second-order diffraction may occur in another hologram lens array layer on the diffraction emission side.

Since such second-order diffracted light is no longer emitted in a direction different from the predetermined direction, it cannot be focused on the pixel electrode of the corresponding color in the spatial light modulator as shown in FIG. Therefore, when the second-order diffraction efficiency increases, the substantial light use efficiency decreases.

FIGS. 5A to 5C show the relationship between incident light and diffracted light in a single hologram lens. This figure is the basis of the concept in considering the relationship between incident light and second-order diffracted light in a hologram color filter having a laminated structure described later.

Since the hologram lens array layer is formed by arranging hologram lenses in an array, each lens has the same light incidence and light as those shown in FIGS. 5A to 5C.
It can be understood that diffraction is occurring.

In particular, FIGS. 5 (a), 5 (b) and 5 (c) show a hologram lens which diffracts and emits light of a specific wavelength in a predetermined direction with respect to oblique incident light. The diffraction emission state when the light of the specific wavelength is incident in the same direction as the diffraction emission direction is shown.

FIG. 5A shows how light of a specific wavelength λ is incident and diffracted on a hologram lens 20 which diffracts and emits light of a specific wavelength λ at a diffraction angle + β among white light incident at an incident angle + α. Actual diffracted light includes not only light of a specific wavelength λ, but also longer wavelength light (shown as “long” in the figure) and shorter wavelength light (shown as “short” in the figure) as sub-diffraction light. Therefore, it is necessary to consider the wavelength dispersion of the incident light and the diffracted light. Light having a wavelength longer than λ is emitted at a diffraction angle + β <, and light having a wavelength shorter than λ is emitted at a diffraction angle + β>.

On the other hand, FIG. 5A shows the relationship between the incident light and the diffracted light when the light of wavelength λ is made incident on the same hologram lens 20 from the incident angle-β direction. In this case, the light having the wavelength λ is diffracted and emitted at the diffraction angle -α. In addition, light having a wavelength longer than λ in FIG.
When light having a wavelength shorter than λ is incident on the hologram lens 20 at an incident angle −β <in β>, all of these incident lights are diffracted and emitted in the diffraction angle −α direction. Thus, FIG. 5A and FIG. 5A have a point-symmetric relationship with each other.

FIG. 5B shows a hologram lens 21 which emits light having a specific wavelength λ at a diffraction angle of zero with respect to incident white light having an incident angle of + α. The hologram lens 21 emits light having a wavelength longer than λ at a positive diffraction angle, and emits light having a wavelength shorter than λ at a negative diffraction angle.

On the other hand, FIG. 5B shows a case where light of wavelength λ is incident on the hologram lens 21 from the direction of zero incident angle. At this time, light of wavelength λ is diffracted and the diffraction angle −α
Indicates injection. Further, when light having a wavelength longer than λ is incident at a negative (−) incident angle or light having a wavelength shorter than λ is incident at a positive (+) incident angle, the light is also emitted in the diffraction angle −α direction. Thus, FIG. 5B and FIG.
(B) has a point-symmetric relationship with each other.

FIG. 5C shows a hologram lens 22 which emits light having a wavelength λ at a diffraction angle −β with respect to incident white light having an incident angle + α. The hologram lens 22 diffracts and emits light having a wavelength longer than λ at a diffraction angle −β>, and emits light having a wavelength shorter than λ at a diffraction angle −β <.

On the other hand, FIG. 5 (c) shows a case where light having a wavelength λ is incident on the hologram lens 22 from an incident angle + β direction. At this time, the light having a wavelength λ is diffracted and the diffraction angle −α
And diffracted. Also, light having a wavelength longer than λ is incident angle +
When light having a wavelength β or shorter than λ is incident at an angle of incidence + β <, the incident light is diffracted and exits in the direction of the diffraction angle −α. 5 (C) and FIG.
(C) also has a point-symmetric relationship with each other.

(3, Second Order Diffraction in Hologram Color Filter Laminated in Order of B Layer / G Layer / R Layer) Next, incident light and diffraction in the hologram lens shown in FIGS. 5 (A) to 5 (c) will be described. The behavior of diffracted light in a hologram color filter having a laminated structure will be considered with reference to the relationship with light.

First, referring to FIGS. 6 to 9, the B (blue) hologram lens array layer 30B (B
Layer), G (green) hologram lens array layer 30G
(G layer) and R (red) hologram lens array layer 3
The hologram color filter 30 laminated in the order of 0R (R layer) (B layer / G layer / R layer) is taken as an example. In each drawing, only the hologram color filter 30 and the pixel electrode 31 used in combination therewith are shown for convenience.

As shown in FIG. 6, each hologram lens array layer is formed by arranging long lenses in an array, and this is a conceptual cross-sectional view. Each rectangular portion separated by a line corresponds to one unit of the hologram lens. The light of the corresponding color diffracted by each hologram lens array layer is condensed substantially vertically on the corresponding pixel electrode for each hologram lens. Therefore, the position of the corresponding pixel electrode corresponds to the position of each hologram lens in each hologram lens array layer 30B, 30G, 30R.

First, FIG. 6 illustrates the emission direction of B light, which is the main diffracted light, in the first hologram lens array layer 30B (shown with spots), which is the first layer.
B light λb1 to λb3 having a blue wavelength among white light incident on the hologram color filter 30 at a constant incident angle
Are the hologram lenses 30B1 and 30B2 in the hologram lens array layer for B 30B and the corresponding pixel electrodes 31b
The light is diffracted and emitted in a direction in which light is condensed substantially vertically on the light beams 31b2.

FIG. 7 shows B light λ diffracted and emitted by the first layer.
This conceptually shows how b1, λb2, and λb3 are second-order diffracted by the second G hologram lens array layer 30G. Here, attention is paid to the hologram lens (marked in the figure) in the hologram lens array layer for G 30G, and in particular, three points a,
The state of incidence and diffraction of light at points b and c is shown. The point a is just above the center of the B color corresponding pixel electrode 31b1, the point b is just above the center of the G color corresponding pixel electrode 31g1, and the point c
Is located just above the center of the R-color corresponding pixel electrode 31r2.

The hologram lens in the hologram lens array layer for G 30G diffracts out in a direction of condensing the G light λg1 to λg3 having a green wavelength among the white light incident at a constant incident angle on the pixel electrode 31g1 of the corresponding color. Lens function. In this hologram lens, the first
5 (A) to 5 (A) to 5 (A) to 5 (C) show how the B light λb1, λb2, λb3 diffracted and emitted by the layer is diffracted.
Consider the light incident and diffracted by the hologram lens shown in FIG.

For example, at the point a of the hologram lens, a diffraction grating is formed so that the G light λg1 incident from the obliquely upper right direction in the figure is diffracted and emitted in the direction of the pixel electrode 31g1, that is, obliquely lower right direction. This corresponds to the case where the specific wavelength λ is replaced with the G light λg1 in FIG. On the other hand, since the B light λb1 is light diffracted and emitted in the direction of converging on the pixel electrode 31b1 by the B hologram lens array layer 30B, the incident angle to the point a is zero and vertically incident. The B light λb1 is light having a shorter wavelength than the G light λg1. Therefore, the B light λb1 corresponds to the “short” light in FIG. That is, according to FIG.
As shown in FIG. 7, the B light λb1 can be second-order diffracted by the hologram lens in a direction corresponding to the emission angle −α.

That is, the B light λb1, which should be focused on the pixel electrode 31b1, is secondarily diffracted by the second G hologram lens array layer 30G, and is focused on a predetermined pixel electrode. Diverged in the horizontal direction, and could not be used as effective display light.

Similarly, at the point b, a diffraction grating is formed so as to diffract and emit the G light λg2 incident from the obliquely upper right direction in the drawing in the direction of the pixel electrode 31g1, that is, vertically downward. This corresponds to the case where the specific wavelength λ is replaced with the G light λg2 in FIG.

On the other hand, since the B light λb2 is light diffracted by the hologram lens array layer for B 30B in the direction of being condensed on the pixel electrode 31b1, it enters the point b obliquely from the upper right. The B light λb2 is light having a shorter wavelength than the G light λg2. That is, the B light λb2 corresponds to the “short” light in FIG. Therefore, according to FIG. 5B, the B light λb2 can be second-order diffracted by the hologram lens in the emission angle −α direction as shown in FIG. The B light λb2 which should be originally focused on the pixel electrode 31b1 is also the G light of the second layer.
When the light is second-order diffracted by the hologram lens array layer for use 30G, it is not condensed on a predetermined pixel electrode but diverges in the horizontal direction, and cannot be used as effective display light.

At point c, a diffraction grating is formed so as to diffract and emit the G light λg3 incident from the obliquely upper right direction in the figure in the direction of the pixel electrode 31g1, that is, the obliquely lower left direction. This is because the specific wavelength λ is changed to the G light λg in FIG.
This corresponds to the case where the number is replaced by 3.

By the way, the B light λb3 incident on the point c is
Since the light is focused on the pixel electrode 31b2, the angle of incidence on the point c is minus (-). Moreover, since the B light λb3 has a shorter wavelength than the G light λg3, the relationship between the incidence and the diffraction at the point c does not correspond to FIG. Therefore, in this case, the B light λb3 is used for the G hologram lens array layer 30G.
And goes straight without being secondarily diffracted, and is condensed on the pixel electrode 31b2.

Next, FIG. 8 conceptually shows how the B light λb4, λb5, λb6 diffracted and emitted by the first layer is second-order diffracted by the third R hologram lens array layer 30R. It is shown. Here, attention is focused on one hologram lens (marked in the figure) in the hologram lens array layer for R 30R, and in particular, the state of diffraction at three points d, e, and f in the same lens. Is shown. The point d is just above the center of the G color pixel electrode 31g1, the point e is just above the center of the R color pixel electrode 31r2, and the point f
Is located just above the center of the B-color corresponding pixel electrode 31b2.

The hologram lens in the hologram lens array layer 30R is an R light λr having a red wavelength of white light incident on the hologram color filter 30 at a fixed angle.
It has a lens function of diffracting and emitting 1 to λr3 in the direction of converging it on the pixel electrode 31r2 of the corresponding color.

For example, at the point d in the hologram lens, the R light λr1 incident obliquely from the upper right is applied to the pixel electrode 31.
A diffraction grating that diffracts and emits light in the r2 direction is formed. This is because the R light λr1 has a specific wavelength λ as shown in FIG.
Corresponding to the diffraction characteristics shown in FIG. By the way, B incident on the point d
Since the light λb4 is light diffracted in the direction of converging on the pixel electrode 31b1, the incident angle at the point d is plus (+), and the B light λb4 has a shorter wavelength than the R light λr1. Therefore, the relationship between the incidence and diffraction of the B light λb4 at the point d is shown in FIG.
Corresponding to the “short” light in (a), the B light λb4 can be second-order diffracted by the hologram lens in a direction corresponding to the emission angle −α.

Similarly, at the point e in the hologram lens, the R light λr2 incident obliquely from the upper right
A diffraction grating that diffracts and emits light in the 1r2 direction is formed, and this diffraction characteristic corresponds to FIG. 5B. Since the B light λb5 incident on the point e is light diffracted in the direction of condensing on the pixel electrode 31b2, the incident angle on the point e is minus (-), and the B light λb5 has a wavelength longer than that of the R light λr2. Is short, the relationship between the incidence and the diffraction at the point e is shown in FIG.
And the B light λb5 travels substantially straight without being secondarily diffracted by the hologram lens corresponding to the R light, and the pixel electrode 3
The light is focused on 1b2.

At point f, a diffraction grating is formed which diffracts and outputs the R light λr3 incident obliquely from the upper right in the direction of the pixel electrode 31r2. This is Figure 5
This corresponds to (C). By the way, the B light λb incident on the point f
Reference numeral 6 denotes light that is condensed on the pixel electrode 31b2, and is vertically incident on the point f. Further, since the B light λb6 has a shorter wavelength than the R light, the relationship between the incidence and the diffraction at the point f does not correspond to FIG. 5 (c). Therefore, the B light λb6 is second-order diffracted by the hologram lens corresponding to the R light. The light travels straight through without being condensed on the pixel electrode 31b2.

Next, how the G light diffracted and emitted from the second G hologram lens array layer 30G can be secondarily diffracted by the third R hologram lens array layer 30R will be considered.

FIG. 9 shows G light λg4 to λg diffracted and emitted by the second hologram lens array layer 30G as the second layer.
Reference numeral 6 conceptually shows a state of second-order diffraction by the third R hologram lens array layer 30R. That is, the G light of the white light (incident from the upper right side in the figure) incident on the hologram color filter 30 is turned by the hologram lens array layer 30G so as to be condensed on the pixel electrodes 31g1 and 30g2 of the corresponding color. Folded out.

Here, attention is paid to one hologram lens (dotted in the figure) in the hologram lens array layer for R 30R, and particularly at three points g, h, and i in the same lens. The state of diffraction is shown. Note that point g
Is located right above the center of the G color pixel electrode 31g1, point h is located directly above the center of the R color pixel electrode 31r2, and point i is located immediately above the center of the B color corresponding pixel electrode 31b2.

The hologram lens in the hologram lens array layer for R 30R has a lens function of diffracting the R lights λr1 to λr3 in a direction in which the R lights are focused on the pixel electrode 31r2 of the corresponding color. For example, at the point g, the R light λr1 incident obliquely from the upper right, at the point h, the R light λr2 incident from the same direction, and at the point i, the R light λr3 incident from the obliquely right direction in the figure, the pixel electrode 31r2. Each diffraction grating is formed so as to diffract and emit light in the directions. Therefore, the diffraction characteristics at points g, h, and i are shown in FIGS. 5A and 5A when the specific wavelength λ is λr1 to λr3.
(B) corresponds to FIG.

On the other hand, the hologram lens array layer 30 for G
G diffracts and emits the G light λg4 and λg5 so as to condense it to the pixel electrode 31g1 and the G light λg6 so as to condense it to the pixel electrode 31g2. The light λg5 is incident diagonally from the upper right and the G light λg6 at the point i is incident diagonally from the upper left. The wavelengths of the G lights λg4 to λg6 are shorter than the wavelengths of the R lights λr1 to λr3. Therefore, the relationship between the incidence and diffraction of the G light λg4 at the point g corresponds to the “short” light in FIG.
4 can be second-order diffracted by the hologram lens in a direction corresponding to the emission angle -α. The relationship between the incidence and diffraction of the G light λg5 at the point h corresponds to the “short” light in FIG.
The G light λg5 can be second-order diffracted by the hologram lens in a direction corresponding to the emission angle −α. Therefore, λg4 and λg5 that are second-order diffracted at points g and h are not collected on the pixel electrode 31g1.

The G light λg6 incident on the point i has a negative (-) angle of incidence on the point i. Moreover, since the wavelength of the G light λg6 is shorter than that of the R light λr3, the relationship between the incidence and the diffraction at the point i does not correspond to FIG. 5C. In this case, the G light λg6 is The light goes straight without being diffracted next, and is condensed on the pixel electrode 31g2.
(4, Diffraction of light in hologram color filter laminated in order of R layer / G layer / B layer) Another example, this time, the lamination order corresponding to the hologram color filter according to the embodiment of the present invention, that is, white light As an example of a hologram color filter in which a hologram lens array layer is laminated in the order of R layer / G layer / B layer from the incident side, diffracted light related to RGB primary color light with reference to FIGS. Consider the behavior of

FIG. 1 shows the R light λr diffracted and emitted by the first hologram lens array layer (R layer) 40R for R.
7A to 7R conceptually show how second-order diffraction is performed by a second G hologram lens array layer (G layer) 40G of the second layer. Here, attention is focused on one hologram lens (marked in the figure) in the G hologram lens array layer 40G, and particularly, the state of diffraction at three locations in the same lens is shown. Note that point j is just above the center of the pixel electrode 41b1 corresponding to B color, point k is just above the center of the pixel electrode 41g2 corresponding to G color, and point l is the pixel electrode 41r corresponding to R color.
2 is located just above the center. At each point on the hologram lens, G light λ incident from a certain direction
A diffraction grating is formed so that g7 to λg9 are condensed substantially vertically on the corresponding pixel electrode 41g2.

The G lights λg7 to λg9 corresponding to the specific wavelengths of the hologram array layer for G 40G are incident on points j, k, and l in the hologram lens from obliquely right above in the figure. The incident and diffracted states of the G lights λg7 to λg9 correspond to FIG. 5A at point j, FIG. 5B at point k, and FIG. 5C at point l.

The R lights λr7 to λr9 are diffracted and emitted by the R hologram lens array layer 40R in a direction in which they are condensed substantially vertically onto the corresponding pixel electrodes. That is, as shown in FIG. 1, the R lights λr7 to λr9 incident on the G hologram lens array layer 40G, for example, enter the point j from obliquely right above in the figure, that is, at a positive (+) incident angle, and k
In the figure, light is incident from an obliquely upper left in the drawing, that is, at an incidence angle of minus (-), and at point l, light is incident at an incidence angle of zero (0) from an upper right in the figure. The R lights λr7 to λr9 are converted to G light λg7
The wavelength is longer than λg9.

From these conditions, the R light λ at the point j
The incident / diffractive state of r7 does not correspond to FIG. 5 (a), and therefore, the R light λr7 is supplied to the G hologram lens array layer 40G.
Are emitted without being second-order diffracted by the pixel electrode 41r1
Focus on top. On the other hand, at the point k, the incident / diffraction state of the R light λr8 corresponds to FIG.
Can be second-order diffracted by the G hologram lens array layer 40G. Further, at the point 1, the incident / diffraction state of the R light λr9 corresponds to FIG. 5C, so that the R light λr9 can be second-order diffracted by the G hologram lens array layer 40G. The second-order diffracted light cannot be focused on the pixel electrode 41r2.

FIG. 2 shows the R light λr10 diffracted by the first R hologram lens array layer (R layer) 40R.
.Lambda.r12 is conceptually shown to be second-order diffracted by the third layer B hologram lens array layer (B layer) 40B.

Here, the state of light incident and diffracted by one hologram lens (area with a spot) in the hologram lens array layer for B (layer B) 40B will be considered. FIG.
As in the case of (3), three points m, n, and o in the hologram lens are considered. Each point is a pixel electrode 41
r1, 41b1, and just above the center of 41g2.

At each position in the lens, a diffraction grating is formed so that the B lights λb7 to λb9 incident from a certain direction are condensed on the pixel electrode 41b1. Therefore, the B light λ
The incident / diffraction state of b7 to λb9 is shown in FIG.
(A), point n corresponds to FIG. 5 (B), and point o corresponds to FIG. 5 (C).

On the other hand, the incident and diffracted states of the R light at points m and n do not correspond to FIGS. 5 (a) and 5 (b).
The light λr10 and λr11 travel straight without being second-order diffracted by the hologram lens array layer for B 40B and are condensed on the corresponding pixel electrode 41r1, but at the point o, the incident angle is minus (−), and Since the R light λr12 has a longer wavelength than the B light λb9, the state of incidence and diffraction corresponds to FIG. 5C, and the R light λr12 can be second-order diffracted by the B hologram lens array layer 40B. As a result, the second-order diffracted light is not focused on the corresponding pixel electrode 41r2.

FIG. 3 shows that the G light diffracted by the second G hologram lens array layer (G layer) 40G is second-order diffracted by the third B hologram lens array layer (B layer) 40B. This is a conceptual view of the situation.

Here, the state of light incident and diffracted by one hologram lens (area with a spot) in the hologram lens array layer for B (layer B) 40B will be considered. As in the case of FIGS. 1 and 2, the point p in the hologram lens,
Consider three points q and r. B light λb7 to λb9 incident from a certain direction is applied to each portion of the pixel electrode 41b.
A diffraction grating is formed so as to converge light on the light source 1. Therefore, the incident / diffraction state of the B light at the point p is as shown in FIG.
(A), the point q corresponds to FIG. 5 (B), and the point r corresponds to FIG. 5 (C).

On the other hand, the incident / diffractive state of the G light λg10 to λg12 does not correspond to FIG.
The light λg10 travels straight without being diffracted by the hologram lens array layer for B 40B, and is condensed on the corresponding pixel electrode 41g1. At the point q, the incident angle of the G light λg11 is minus (-), and Since the G light λg11 has a longer wavelength than the B light λb8, the state of incidence and diffraction corresponds to FIG. 5B, and the G light λg11 can be second-order diffracted by the B hologram lens array layer 40B. Also at point r, G
Since the incident angle of the light λg12 is zero and the wavelength of the G light λg12 is longer than that of the B light, the state of incidence and diffraction is shown in FIG.
Corresponding to (c), the G light λg12 can be second-order diffracted by the B hologram lens array layer 40B. The second-order diffracted light is not focused on the corresponding pixel electrode 41g2.

As described above, a hologram color filter in which hologram lens array layers are laminated in the order of B layer / G layer / R layer from the incident light side and each hologram lens array layer in the order of R layer / G layer / B layer from the incident light side. The behavior of the second-order diffracted light was considered for the two types of laminated hologram color filters. As can be seen by comparing the diffraction state of each color light in both cases, the stacking order of the hologram lens array layer changes the state of the second-order diffraction. Here, for convenience, only the diffraction emission direction of the second-order diffracted light at three locations in one hologram lens is illustrated, but the relationship between the incident angle and the diffraction grating changes depending on the position on the lens. It can be seen that the secondary diffraction characteristics have changed.

(5. Second-Order Diffraction Characteristics in Hologram Color Filters with Different Laminated Structures) By performing a simulation based on the above-described examination results, the relationship between the stacking order of the hologram lens array layers and the second-order diffraction is further improved. The following specific study was conducted.

The hologram lens array layer is for R (R
Layer), G (G layer), and B (B layer).
The combination of the lamination order is 1) R layer / G from the white light incident side.
Layer / B layer, 2) B layer / R layer / G layer, 3) G layer / B layer / R
Layers, 4) B layer / G layer / R layer, 5) R layer / B layer / G layer,
6) There are a total of six types of G layer / R layer / B layer. Thus, for each of the hologram color filters having the six stacking orders, one unit of the hologram lens was divided into 24 equal parts in the wavelength dispersion direction, and the second-order diffraction efficiency at each position was obtained by simulation. The results are shown in FIGS.

The simulation conditions were as follows: the change in the refractive index of the photosensitive material constituting the hologram color filter
n is 0.045, the thickness of each hologram lens array layer is 4.5 μm, and the incident angle of the readout light (white light) is 60.
And the designed diffraction angle of the main diffracted light was set to 0 degree. The center wavelengths corresponding to the three primary colors are 435 nm for the blue center wavelength, 545 nm for the green center wavelength, and 640 nm for the red center wavelength.

First, FIG. 10 shows the second-order diffraction characteristics of the hologram color filter in which the hologram lens array layer is laminated in the order of R layer / G layer / B layer from the white light incident side, in which the R light and the G light are received. The horizontal axis indicates the relative position on the hologram lens, and the vertical axis indicates the second-order diffraction efficiency (%).

In the figure, the “R light / G layer” means the R light diffracted by the first hologram lens array layer (R layer).
The hologram lens array layer for G (G
2) shows the efficiency of second-order diffracted light. Similarly, “R light / B
The “layer” means that the R light diffracted by the first hologram lens array layer (R layer) as the first layer is second-order diffracted by the third hologram lens array layer (B layer) as the third layer. The efficiency is referred to as “G light / B layer” when the G light diffracted by the second G hologram lens array layer (G layer) is the third B hologram lens array layer (B layer). Layer) shows the efficiency of second-order diffraction (hereinafter, in FIGS. 11 to 15,
Have the same meaning). The hologram lens array layer here refers to one unit of the hologram lens in each layer.

As is apparent from the figure, the second-order diffraction efficiency greatly changes depending on the relative position on the hologram lens. For example, in the hologram lens of each layer, the position on the left side in the drawing is hardly affected by the second-order diffraction, whereas the position on the right side in the drawing has a portion exhibiting a diffraction efficiency of 80% or more. This result almost coincides with the results shown in FIGS. 1 to 3 described above.

Hereinafter, FIGS. 11 to 14 show similar simulation results of the second-order diffracted light.

FIG. 11 shows the second-order diffraction characteristics received by the B light and the R light in a hologram color filter in which a hologram lens array layer is stacked in the order of B layer / R layer / G layer from the white light incident side.

FIG. 12 shows the second-order diffraction characteristics of G and B lights in a hologram color filter in which a hologram lens array layer is laminated in the order of G layer / B layer / R layer from the white light incident side. This laminated structure is described in FIGS.
Corresponds to the structure described with reference to FIG.

FIG. 13 shows the second-order diffraction characteristics received by the B light and the G light in the hologram color filter in which the hologram lens array layers are stacked in the order of B layer / G layer / R layer from the white light incident side.

FIG. 14 shows the second-order diffraction characteristics of the hologram color filter, in which the hologram lens array layers are laminated in the order of R layer / B layer / G layer from the white light incident side, to the R light and the B light.

FIG. 15 shows the second-order diffraction characteristics of G and B lights in a hologram color filter in which a hologram lens array layer is laminated in the order of G layer / R layer / B layer from the white light incident side.

As can be seen from the comparison between the graphs of FIGS. 10 to 15, the second-order diffraction characteristic changes when the stacking order of the hologram lens array layers changes. In particular, the relationship with the position on the lens varies.

FIG. 16 shows the total sum of the second-order diffraction efficiencies of the hologram color filters in each lamination order for each color light. The numerical values in Table 16 are numerical values obtained from the area ratios of the respective graphs in FIGS.

Generally, most of the second-order diffracted light is diverged without being converged on the corresponding pixel electrode, resulting in light loss.
Comparing the total second-order diffraction efficiency involves comparing the substantial light utilization rates of the respective hologram color filters.

As a result, as shown in Table 16, in the hologram color filter according to the present embodiment, in which the R layer / G layer / B layer were laminated in this order from the incident light side, the total second-order diffraction efficiency of R light was 17%, and G It can be seen that the total second-order diffraction efficiency of light is 28%, and the lowest second-order diffraction efficiency is obtained.

In the hologram color filter laminated in the order of B layer / R layer / G layer from the incident light side, the total second-order diffraction efficiency of B light is 53% and the total second-order diffraction efficiency of R light is 5%. In a hologram color filter laminated in the order of G layer / B layer / R layer from the incident light side, the total second-order diffraction efficiency of G light is 5
The total second-order diffraction efficiency of 1% and the B light is 2%, and the hologram color filter having such a laminated structure also has a lower total second-order diffraction efficiency as compared with the hologram color filters having other lamination orders.

As described above, the order of the R layer / G layer / B layer, the order of the B layer / R layer / G layer, or the order of the G layer / B layer / R layer from the incident light side according to the present embodiment. The stacked hologram color filters can suppress the generation of the second-order diffraction efficiency low by the stacked structure, so that the light utilization efficiency can be substantially increased.

When the hologram color filter according to the present embodiment is used for a spatial light modulator as shown in FIG. 4, it is possible to increase the light use efficiency of the entire device.

[0086]

As described above, the hologram color filter of the present invention diffracts and disperses mainly the light in the red wavelength region of the incident light, and condenses the hologram lens array layer for red on the corresponding pixel. The hologram lens array layer for blue, which mainly diffracts and disperses the light in the blue wavelength range of the incident light and condenses it on the corresponding pixels, and diffracts and disperses the light mainly in the green wavelength range of the incident light, responds In a hologram color filter having a structure in which a green hologram lens array layer condensed on a pixel is laminated, the hologram color filter according to the first invention specifies the lamination order.
The lamination order is from the incident light side for red, green, and blue. In the hologram color filter according to the second invention, the lamination order is from the incident light side for red,
In the hologram color filter according to the third invention, the lamination order is for green, blue, and red from the incident light side.

According to the hologram color filter of the present invention, it is possible to suppress the occurrence of light loss due to second-order diffraction occurring in a layer different from the hologram lens array layer of the corresponding color, and to provide a high light utilization factor.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a state of second-order diffraction of red light in a G layer in a hologram color filter laminated in the order of R layer / G layer / B layer according to the present embodiment.

FIG. 2 is a schematic cross-sectional view showing a state of second-order diffraction of red light in a B layer in a hologram color filter laminated in the order of R layer / G layer / B layer according to the present embodiment.

FIG. 3 is a schematic cross-sectional view showing a state of second-order diffraction of green light in a B layer in a hologram color filter laminated in the order of R layer / G layer / B layer according to the present embodiment.

FIG. 4 is a schematic sectional view showing a structure of a spatial light modulator using a hologram color filter according to the present embodiment.

FIG. 5 is a conceptual diagram for explaining the relationship between incident light having wavelength dispersion and diffracted light with respect to a hologram lens.

FIG. 6 is a schematic cross-sectional view showing a state of diffraction of blue light in a B layer in a hologram color filter laminated in the order of B layer / G layer / R layer.

FIG. 7 is a schematic cross-sectional view showing a state of second-order diffraction of blue light in a G layer in a hologram color filter laminated in the order of B layer / G layer / R layer.

FIG. 8 is a schematic cross-sectional view showing a second-order diffraction of blue light in an R layer in a hologram color filter laminated in the order of B layer / G layer / R layer.

FIG. 9 is a schematic cross-sectional view showing a second-order diffraction of green light in an R layer in a hologram color filter laminated in the order of B layer / G layer / R layer.

FIG. 10 shows R layer / G layer /
FIG. 9 is a diagram illustrating a second-order diffraction efficiency of three primary color lights in a hologram color filter stacked in the order of the B layer.

FIG. 11 shows B layer / R layer /
FIG. 9 is a diagram illustrating the second-order diffraction efficiency of the hologram color filters stacked in the order of G layers with respect to the three primary colors.

FIG. 12 shows G layer / B layer /
FIG. 7 is a diagram illustrating a second-order diffraction efficiency of three primary color lights in a hologram color filter stacked in the order of the R layer.

FIG. 13 shows B layer / G layer /
FIG. 7 is a diagram illustrating a second-order diffraction efficiency of three primary color lights in a hologram color filter stacked in the order of the R layer.

FIG. 14 shows R layer / B layer /
FIG. 9 is a diagram illustrating the second-order diffraction efficiency of the hologram color filters stacked in the order of G layers with respect to the three primary colors.

FIG. 15 shows G layer / R layer /
FIG. 9 is a diagram illustrating a second-order diffraction efficiency of three primary color lights in a hologram color filter stacked in the order of the B layer.

FIG. 16 is a table showing the total second-order diffraction efficiency for each color light in each hologram color filter.

[Explanation of symbols]

 13, 30, 40: hologram color filter 23, 31, 41: pixel electrode 26: light modulation layer

Claims (3)

[Claims] 1. A hologram lens array layer for red, which mainly diffracts and disperses light in a red wavelength range of incident light and condenses it on a corresponding pixel, diffracts light mainly in a blue wavelength range of incident light. A blue hologram lens array layer that disperses and condenses the light onto the corresponding pixel; and a green hologram lens array layer that diffracts and disperses mainly the light in the green wavelength region of the incident light and condenses the light onto the corresponding pixel. A hologram color filter having a laminated structure comprising: a hologram color filter, wherein each hologram lens array layer is laminated in the order of red, green, and blue from the incident light side. 2. A hologram lens array layer for red, which mainly diffracts and disperses light in a red wavelength range of incident light and condenses it on a corresponding pixel, diffracts light mainly in a blue wavelength range of incident light. A blue hologram lens array layer that disperses and condenses the light onto the corresponding pixel; and a green hologram lens array layer that diffracts and disperses mainly the light in the green wavelength range of the incident light and condenses the light onto the corresponding pixel. A hologram color filter having a laminated structure comprising: a hologram color filter, wherein hologram lens array layers are laminated in the order of blue, red, and green from the incident light side. 3. A hologram lens array layer for red, which diffracts and disperses mainly the light in the red wavelength range of the incident light and condenses it on the corresponding pixel, diffracts mainly the light in the blue wavelength range of the incident light. A blue hologram lens array layer that disperses and condenses the light onto the corresponding pixel; and a green hologram lens array layer that diffracts and disperses mainly the light in the green wavelength region of the incident light and condenses the light onto the corresponding pixel. A hologram color filter, comprising: a hologram color filter having a laminated structure comprising: a hologram lens array layer in which green, blue, and red hologram lens array layers are laminated in this order from the incident light side.