JPH11174449A - Illuminator of reading light to spatial light modulation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical configuration capable of radiating reading light polarized in all the same direction even if indefinitely polarized light from a light source side is of a conical luminous flux in an illuminator irradiating an optical modulating layer of a spatial light modulating device with the reading light in a diagonal direction. SOLUTION: A light modulation layer (liquid crystal layer: lighting area 5a) and a polarized light selecting element (polarizing plate 2') of a spatial light modulating device 1 are arranged in an optically parallel relation. If the polarizing plate is arranged orthogonal to the optical axis of the luminous flux of said indefinitely polarized light, the directions of the polarized light components transmitted become irregular, while according to the above arrangement, even if the indefinitely polarized light forms a conical luminous flux, only the polarized components having a same polarizing direction as the transmission axis of the polarizing plate 2' are transmitted and the lighting area 5a can be irradiated with reading light of all the same directions, and as a result, a modified image with a sharp contrast is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading light illuminating device for a spatial light modulator, and is applied to a projection display device, a projector, an optical information processing device and the like, and obtains a high contrast modulated light. Regarding system improvement.

[0002]

2. Description of the Related Art Recently, a projection type display using a liquid crystal panel as a spatial light modulator has been developed. In particular, a reflection type liquid crystal panel is applied to an aperture in a conventional transmission type liquid crystal panel. Attention has been paid to the fact that the rate can be increased to 90% or more, while the rate was about 50%, and it is already being partially implemented.

An illumination optical system and a spatial light modulator in a projection type display using a reflection type liquid crystal panel are shown in FIG.
Has a schematic configuration as shown in FIG. In the figure, 1 is a spatial light modulator, 2 is a polarizing plate, 3 is an integrator, 4 is a light source such as a halogen lamp or a metal halide lamp, and the spatial light modulator 1 is a reflective liquid crystal panel 5 and a glass substrate 6. The coupling prism 7 has a laminated structure. Here, in the reflection type liquid crystal panel 5, a MOS-transistor and a reflection mirror (pixel electrode) made of Al are formed in pixel units on the upper side of the Si substrate, and the liquid crystal is sandwiched between the substrate and the transparent common electrode. -Consisting of a sealed basic structure, the liquid crystal between each reflection mirror and the common electrode is driven by the active matrix method, so that the readout light incident on the liquid crystal layer is modulated and reflected in pixel units. I have. In that case, in the reflective liquid crystal panel 5, MOS-transistors and connection wiring can be provided below the reflective mirror, and even if the pixels are made finer, almost the entire surface of the panel is reflective regardless of the size of the MOS-transistor. Therefore, a large aperture ratio can be secured as described above.

On the other hand, with respect to the illumination optical system, the indeterminate polarized light obtained from the light source 4 is made incident on the polarizing plate 2 via the integrator 3 and one of the polarized components (here, S (Polarized light component) is selectively transmitted to be incident on the spatial light modulator 1.However, the optical axis of the irregularly polarized light beam incident on the polarizing plate 2 is transmitted to the light modulation layer of the reflective liquid crystal panel 5. The luminous flux of the S-polarized component (reading light) transmitted through the polarizing plate 2 and having a certain angle θ with respect to the normal set to the corresponding liquid crystal layer, is transmitted through the coupling prism 7 and the glass substrate 6 to the liquid crystal. Oblique direction to the layer (incident angle: θ)
From the light source. In this case, the incidence surface 7a of the coupling prism 7 is set to have a relationship perpendicular to the optical axis, and the coupling prism 7 and the glass substrate 6 are made of glass having the same refractive index. Is used, the reading light enters the liquid crystal layer without being refracted. Although not shown, between the integrator 3 and the polarizing plate 2, a cold mirror or the like for removing components in an infrared wavelength band is interposed, or a three-plate projection display for displaying a color image. In some cases, the light path may be led to a liquid crystal panel corresponding to each color after being separated into R, G, and B color lights in advance, so that the light path between them is often not physically straight.

The S-polarized light component incident on the liquid crystal layer reciprocates in the liquid crystal layer by being reflected by the reflection mirror.
The driving of the reflective liquid crystal panel 5 based on the image signal controls the transition of the liquid crystal molecules and receives modulation.
The light enters the coupling prism 7 from 6 and exits from the exit surface 7a, and is further guided to a projection optical system (not shown) to project an image based on the modulated light on a screen (not shown).

[0006]

By the way, in the configuration of the illumination optical system and the spatial light modulator 1 in the above-mentioned projection type display, as shown in the figure, the polarization selection surface of the polarizing plate 2 is positioned with respect to the optical axis of the incident light beam. Are arranged in a vertical relationship with each other, and this is a method of using a polarizing plate in a normal mode. In this case, the direction of the transmission axis of the polarizing plate 2 is set to a direction perpendicular to the plane of FIG. 8, and the polarization direction of the incident irregularly polarized light is a polarization component parallel to the transmission axis direction. Is selectively transmitted to be incident on the spatial light modulator 1.

On the other hand, regarding the illumination optical system, the light source 4
Does not have an ideal point light source but has a light emitting part of finite size. In the integrator 3, a large number of secondary light source images are created by a first lens plate 3a in which minute lens segments are arranged in a matrix. And each secondary light source image is transferred to a second lens plate.
3b constitutes an optical system for forming an image on the plane area (illumination area of readout light) of the liquid crystal layer of the reflection type liquid crystal panel 5 on the side of the spatial light modulation section 1. Therefore, the indeterminate polarized light incident on the polarizing plate 2 is composed of a bundle of a large number of conical light beams. The light is a polarizing plate
It will have an angle of incidence other than 90 ° with respect to the second polarization selection plane.

FIG. 9 shows the polarization selecting function of the polarizing plate 2 under the incident condition. However, in the figure,
5a is an illumination area of the reading light of the reflective liquid crystal panel 5,
The direction indicated by the white arrow corresponds to the direction of the transmission axis of the polarizing plate 2. Each drawing associated with a drawing line from each position indicated by 示 す indicates a polarization component and its polarization direction as viewed from the near side in the traveling direction of the light beam at that position.

First, as a basic function, the polarization selecting surface of the polarizing plate 2 has a polarization component at a crossing line between a surface perpendicular to the traveling direction of the light beam and a surface including the transmission axis and perpendicular to the polarization selecting surface. And transmits the selected polarization component. Therefore, as shown in FIG.
Of the light beams of indeterminate polarization obtained through the integrator 3 from the side 4, the light beams that are perpendicularly incident on the polarization selection surface of the polarizing plate 2
Focusing on (A), an S-polarized component [S] whose polarization direction is the same as the transmission axis of the polarizing plate 2 is selected and transmitted, and
Focusing on the incident light beam (B) that is not perpendicular to the polarization selection plane of No. 2, the S-polarized light component [S ′] whose polarization direction includes the transmission axis and is perpendicular to the polarization selection plane is selected and transmitted. . In this case, the respective S-polarized light components [S] and [S ′] are incident on the illumination area 5a of the readout light, whereas the polarization direction of [S] is parallel to the plane of the illumination area 5a. The polarization direction of S ′] is not parallel, and the polarization direction of the transmitted polarization component generally differs depending on the angle of incidence of each incident light beam on the polarizing plate 2. 5a is irradiated.

If the polarization direction of the readout light is not uniform as described above, the modulation state in the reflective liquid crystal panel 5 will be different for each light beam of each polarization direction in the readout light. The light causes a decrease in the contrast of the image. Therefore, the present invention provides an optical configuration capable of irradiating the light modulation layer of the spatial light modulator with readout light of a polarization component having a uniform polarization direction, even if the irregularly polarized light obtained from the light source side is a conical light beam. It was created for the purpose of realizing a projection display device and a projector having high contrast characteristics.

[0011]

According to the present invention, the optical axis of the light beam of irregular polarization obtained from the light source is inclined with respect to the light modulation layer of the spatial light modulator, and is arranged in the light path of the light beam. An illumination device that selectively transmits only one polarization component included in the indefinite polarization by a polarization selection element and irradiates the polarization component as readout light to a light modulation layer of the spatial light modulation device, wherein the polarization selection The present invention relates to a reading light illuminating device for a spatial light modulation device, wherein a polarization selection surface of an element and a light modulation layer of the spatial light modulation device are arranged in an optically parallel relationship.

Here, the “optically parallel relationship” means that a light refraction element is interposed between the polarization selection surface of the polarization selection element and the light modulation layer of the spatial light modulator. It is a concept including tilting the polarization selection surface of the polarization selection element with respect to the light modulation layer of the spatial light modulator in accordance with the refraction angle, and also physically when the refraction element does not exist. Be parallel. Further, the above-mentioned “polarization selecting element” is an optical element having a function as a polarizer that selectively transmits only one of the polarization components included in the indeterminate polarized light. Also includes splitter.

In the present invention, the optical axis of the light beam of irregular polarization obtained from the light source is inclined with respect to the light modulation layer of the spatial light modulator, and the polarization selection surface of the polarization selection element is optically connected to the light modulation layer. Are in parallel with each other, so that the indeterminate polarized light is incident on the polarization selection surface at an angle. The polarization selection element selects a polarization component at an intersection of a plane perpendicular to the light traveling direction and a plane including the transmission axis and perpendicular to the polarization selection plane, but the polarization selection plane is indeterminate as described above. Since the light is inclined with respect to the polarized light beam, even if the incident angles of the light beams included in the irregularly polarized light beam with respect to the polarization selection surface are different, the polarization directions of the selected polarization components are all the polarization selection surface. Are parallel to the transmission axis direction. That is, even if the irregularly polarized light is a condensed light flux of a conical light flux, the light modulation layer is irradiated with a polarized light component having a uniform polarization direction, and the spatial light modulation device modulates the read light with a uniform polarized light component. In addition, a high-contrast image can be reproduced by the modulated projection light.

By the way, when no light refraction element is interposed between the polarization selection surface of the polarization selection element and the light modulation layer of the spatial light modulator, even if the polarization selection surface and the light modulation layer are physically parallel. However, when a refraction element is interposed under the condition of the parallel arrangement, the polarization direction is rotated according to the incident angle of each ray to the refraction element, and as a result, the polarization direction of the polarization component irradiated on the light modulation layer Become irregular. In such a case, if the polarization selection surface of the polarization selection element is inclined with respect to the light modulation layer of the spatial light modulator in accordance with the refractive index of the refraction element, the rotation of the polarization direction due to the refraction element can be reduced. A polarization component having a polarization direction that cancels out can be selectively transmitted. That is, even if a refraction element is interposed, the polarization direction of the polarization component irradiated on the light modulation layer can be made uniform by maintaining the optical parallel relationship between the polarization selection surface and the light modulation layer.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the "illumination device for reading light to a spatial light modulator" of the present invention will be described below in detail with reference to FIGS. Embodiment 1 First, FIG. 1 shows a schematic configuration of an illumination optical system and a spatial light modulator in a projection display using a reflective liquid crystal panel, as in FIG. The parts of the integrator 3 and the light source 4 are omitted, and only the positional relationship between the spatial light modulator 1 and the polarizing plate 2 'is shown.
Note that, in FIG. 1, each element indicated by the same reference numeral as FIG. 8 corresponds to the same element.

The feature of this embodiment resides in that the polarizing plate 2 ′ is disposed in a parallel relationship with its polarization selection surface and the liquid crystal layer of the spatial light modulator 1. Accordingly, the optical axis of the light beam of irregular polarization obtained from the light source 4 via the integrator 3 and the like and the polarization selection surface of the polarizing plate 2 'make an angle of (90-θ) °, and the polarizing plate
Irregularly polarized light enters obliquely with respect to 2 ′.

Next, the function of selecting the polarization of the polarizing plate 2 'under the arrangement conditions based on the above features will be described with reference to FIG. First, among the light beams of indeterminate polarization incident from an oblique direction, focusing on the incident light beam (A) that is perpendicular to the transmission axis of the polarizing plate 2 ′, the polarizing plate 2 ′ is orthogonal to the traveling direction of the light beam. In order to select the S-polarized light component at the intersection of the plane and the plane perpendicular to the polarization selection plane including the transmission axis, the S-polarized light component in the polarization direction perpendicular to the traveling direction of the light beam (A) and coinciding with the transmission axis direction Only [S] is selectively transmitted. On the other hand, focusing on the incident light (B) that is not perpendicular to the transmission axis of the polarizing plate 2 ', the polarization selecting function of the polarizing plate 2' is the same as described above, but the S-polarized light component [S '] of the light (B). Is not coincident with the direction of the transmission axis (inclined by an angle α when viewed in a plane), and thus corresponds to the decomposition vector of the S-polarized component [S ′] in the transmission axis direction [Sy]. = Only S'cosα is selectively transmitted.

Each of the S-polarized light components [S] and [Sy] selected and transmitted by the polarizing plate 2 'as described above is
The light travels in the directions (A) and (B) and enters the illumination area 5a of the reflective liquid crystal panel 5. In this case, since the polarization directions of the respective S-polarized light components [S] and [Sy] after passing through the polarizing plate 2 ′ in FIG. 2 are parallel to the direction of the transmission axis of the polarizing plate 2 ′, If the selection surface and the illumination area 5a are set in parallel, a polarization component having the same polarization direction on the surface of the illumination area 5a
(Read light). That is, as shown in FIG. 9, the polarizing plate 2 is arranged in a relationship perpendicular to the optical axis of the light beam of irregular polarization.
Polarization component [S '] of the incident light (B) not perpendicular to the transmission axis of
If is selected and transmitted as it is, the polarization direction will be different from the S-polarized component [S] of the perpendicular incident light (A) on the surface of the illumination area 5a, but according to this embodiment, the polarizing plate 2 ', A polarization component [Sy] obtained by rotating the polarization direction of the S polarization component [S'] by an angle α around the optical axis of the light beam (B) is selected and transmitted, and as a result, the polarizing plate In the illumination area 5a parallel to the 2 ′ polarization selection plane, S-polarized light components [S] and [Sy] having the same polarization direction are obtained. Note that the angle α is generally a small angle of at most about 10 °, and when the angle θ in FIG. 1 is set small, the angle α also becomes small.
(The angle θ is usually set in a range of about 30 to 60 °),
The polarization component [Sy] is so different from the polarization component [S].

Since the conditions for selecting and transmitting the S-polarized light component by the polarizing plate 2 'and the conditions for irradiating the illumination area 5a of the reflective liquid crystal panel 5 are satisfied for all the rays of the incident irregularly polarized light, the illumination area The readout light (S-polarized light component) for 5a is incident with its polarization direction completely aligned, and the modulation characteristics in the reflective liquid crystal panel 5 are uniform for all the light beams of the readout light, resulting in high contrast. Thus, projection light capable of displaying an image on the LCD is obtained. Further, in this embodiment, the polarizing plate 2 ′ has been described as having the function of selecting the S-polarized light component. Similar effects can be obtained.

<Embodiment 2> In the first embodiment, the readout light (S-polarized light component) transmitted through the polarizing plate 2 'is not subjected to any refraction, and the readout light illumination area 5 of the reflective liquid crystal panel 5 is not affected.
The explanation has been given on the assumption that it reaches a. However, in a general spatial light modulation device, a light refraction element such as a glass substrate is often interposed from the incident surface of the readout light to the light modulation layer. As shown in FIG. 3, the luminous flux of the S-polarized light component obtained from the polarizing plate 2 ′ is made incident on the incident surface 7 a of the coupling prism 7 at a fixed inclination angle, and the refractive index of the A reflective liquid crystal panel is set by setting a large refractive index and refracting the light beam of the polarized light component.
In some cases, the readout light of No. 5 may be guided to the illumination area 5a.

In this case, since the S-polarized light component always keeps a relation perpendicular to the direction of the light beam, as shown in FIG.
When the polarization selection surface of the polarizing plate 2 ′ is kept in a physical parallel relationship with the illumination area 5 a of the reflective liquid crystal panel 5 as in the first embodiment, the polarization direction of the S-polarized component of each light beam is The rotation from the state before the refraction is performed in accordance with the refraction angle, and as a result, the polarization direction of the readout light in the illumination area 5a becomes uneven.

The state can be considered with reference to FIG. 4 in the same expression format as in FIG. However, in FIG. 4, the coupling prism 7 ignored in the configuration of FIG. 2 is provided above the illumination area 5a as a refraction element. Here, in order to avoid complication of the description, it is assumed that the light beam is refracted only on the incident surface 7a of the coupling prism 7, and the refraction condition by the glass substrate 6 is expressed without consideration. As is clear from the comparison between FIG. 4 and FIG. 2, the function of selecting and transmitting the polarized light component by the polarizing plate 2 ′ is the same as that of the first embodiment, and each light beam (A), (B) is a ray of S-polarized light components [S] and [Sy],
The light is refracted by the incident surface 7a of the coupling prism 7 and reaches the illumination area 5a of the reflective liquid crystal panel 5. In this case, of the light rays of the conical luminous flux, the light rays that are perpendicular to the transmission axis of the polarizing plate 2 ′ are perpendicular to the polarization selection surface of the polarizing plate 2 ′ and the illumination area 5 a of the reflective liquid crystal panel 5. , The polarization direction of the S-polarized component [S] of the light beam does not change. However, with respect to a light ray that is not perpendicular to the transmission axis of the polarizing plate 2 ', the S-polarized light component [Sy] before being incident due to refraction.
Is rotated by an angle β corresponding to the angle of refraction,
It becomes an S-polarized light component represented by [S1].

Therefore, in this case, the ratio deviates from the rational condition in the first embodiment, and as a result, the S-polarized component [S] of the light (A) and the S-polarized light of the light (B) in the illumination area 5a. Since the component [S1] is incident in a different polarization direction and is illuminated with read light having a non-uniform polarization direction as in the case of FIG. 9, the contrast of the image due to the projection light after modulation by the reflective liquid crystal panel 5 is reduced. .

Therefore, in this embodiment, as shown in FIG. 5, when a refractive element is interposed in the optical path between the polarizing plate 2 'and the illumination area 5a of the reflective liquid crystal panel 5, the polarizing plate 2'
Is inclined with respect to the liquid crystal layer of the reflective liquid crystal panel 5 so that the two have an optically parallel relationship. Specifically, the angle (refraction angle) between the optical axis of the light beam of the irregularly polarized light incident on the polarizing plate 2 ′ and the optical axis when the readout light of the S-polarized component enters the liquid crystal layer of the reflective liquid crystal panel 5 ψ In response to the above, the polarization selection surface of the polarizing plate 2 ′ is inclined by an angle Φ with respect to the surface of the liquid crystal layer, so that both surfaces are physically non-parallel, but optically under the same conditions as in the first embodiment. To obtain an optical parallel relationship that can be configured.

The magnitude of the inclination angle Φ is determined in the same manner as in FIG.
This will be described with reference to FIG.
In the figure, first, the incident light (A) is
, The S-polarized component [S] is selected and transmitted as in the case of FIG. Meanwhile, the incident ray
Regarding (B), the basic principle of the polarizing plate 2 ′ is to select an S-polarized component at the intersection of a plane perpendicular to the light propagation direction and a plane including the transmission axis and perpendicular to the polarization selection plane. The S-polarized component [S2] is selected and transmitted based on the function. The polarization direction of the S-polarized component [S2] is rotated by an angle β with respect to the polarization direction of the S-polarized component [Sy] obtained in the first embodiment and FIG. ,
In FIG. 4, the S-polarized light component [Sy] before refraction becomes the S-polarized light component [S1] after refraction, and the direction of polarization is opposite to the direction of rotation. That is, the polarization direction of the S-polarized component [S2] is
In FIG. 4, the S-polarized light component of the light beam (B) is refracted by the incident surface 7a of the coupling prism 7, thereby canceling the angle (β) by which the polarization direction is rotated. Is set so as to give the conditions of the rotation angle and the rotation direction.

Therefore, the light beam selected and transmitted by the polarizing plate 2 '
The S-polarized light component [S2] according to FIG.
At the stage where the light enters the S-polarized light component [Sy] having the same polarization direction as the S-polarized light component [Sy] obtained in the first embodiment.
y ′], and enters the illumination area 5a of the reflective liquid crystal panel 5 in the same polarization direction as the S-polarized light component [S] of the light ray (A). In other words, even when a refraction element such as the coupling prism 7 or the glass substrate 6 is interposed,
If the polarization selection surface of the polarizing plate 2 ′ is inclined in accordance with the refractive index, the same optical conditions as in the first embodiment can be configured.

In the first and second embodiments, the case where the polarizing plate 2 'is used has been described. However, it goes without saying that the principle can also be applied to the case where a polarizing beam splitter is used. In that case, for example, FIG.
The polarization beam splitter 8 is arranged in a mode as shown in FIG. 5, but the polarization separation plane (corresponding to the polarization selection plane) 8a may be set under the conditions of each of the above embodiments, and a polarizing plate
The difference from 2 ′ is only whether or not a polarized light component other than the required polarized light component is guided in a predetermined direction as reflected light. In addition, although the embodiments have been described with respect to the case where the present invention is applied to the reflective liquid crystal panel 5, it is of course that the same effect can be obtained even when the present invention is applied to the transmissive liquid crystal panel.

[0028]

According to the present invention, the "illumination device for reading light with respect to the spatial light modulator" has the following effects by having the above configuration. In the spatial light modulator that irradiates the readout light from an oblique direction, the integrator etc. are interposed in the illumination optical system, so that the illumination light of irregular polarization obtained from the light source side is a condensed light flux of a conical light flux In many cases, when the polarization selection surface of the polarization selection element is arranged perpendicular to the optical axis of the aggregated light beam according to a normal usage, the spatial light modulation device is in a state where the polarization directions of the selected polarization components are not uniform. Irradiates the light modulating layer, thereby lowering the contrast of the image due to the modulated light. The present invention provides an extremely simple configuration in which a polarization selection surface of a polarization selection element and a light modulation layer of a spatial light modulation device are arranged in an optically parallel relationship with each other. Can irradiate a polarized component that is completely uniform, and the above problem is rationally solved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration of an illumination optical system and a spatial light modulation unit (a modulation unit is a reflective liquid crystal panel) in a projection display according to a first embodiment of a “lighting device for reading light with respect to a spatial light modulation device” of the present invention. FIG.

FIG. 2 is a diagram for describing a polarization selection function of a polarizing plate by expressing the optical system of FIG. 1 in a plan view, and showing polarization components and polarization directions of each light beam.

FIG. 3 is a schematic configuration diagram showing a case where a coupling prism or the like functions as a refraction element in the optical system of FIG. 1;

FIG. 4 is a diagram showing the optical system of FIG. 3 in a plan view, and showing a polarization component and a polarization direction of each light beam to explain a polarization selection function of a polarizing plate and a problem in that case. .

FIG. 5 shows an illumination optical system and a spatial light modulator in the projection display according to the second embodiment (the modulator is a reflective liquid crystal panel).
FIG. 3 is a schematic configuration diagram of FIG.

FIG. 6 is a diagram illustrating the optical system of FIG. 5 in a plan view and illustrating a polarization component of each light ray and a polarization direction thereof to explain a polarization selection function of a polarizing plate.

FIG. 7 is a schematic configuration diagram showing an arrangement mode when a polarizing beam splitter is used.

FIG. 8 is a schematic configuration diagram of an illumination optical system and a spatial light modulator in a projection display using a reflective liquid crystal panel.

FIG. 9 is a plan view showing the relationship between the polarizing plate and the illumination area of the spatial light modulator in the configuration (prior art) of FIG. FIG. 4 is a diagram for explaining a polarization selection function of FIG.

[Explanation of symbols]

1… Spatial light modulator, 2,2 ′… Polarizer, 3… Integrator,
3a: first lens plate, 3b: second lens plate, 4: light source, 5: reflective liquid crystal panel, 5a: illumination area, 6: glass substrate, 7: coupling prism, 7a: incident surface, 8: polarized beam Splitter, 8a: polarized light separating surface, A, B: light beam, S, S ', S1, S
2, Sx, Sy, Sy ': S-polarized light component, P: P-polarized light component, α: angle between light beam A and light beam B when viewed in a plane, β: rotation angle of S-polarized light component, θ: incident angle , Ψ ... refraction angle.

Claims (4)

[Claims] 1. An optical axis of a light beam of indeterminate polarization obtained from a light source is inclined with respect to a light modulation layer of a spatial light modulator, and is converted into the indeterminate polarization by a polarization selection element arranged in an optical path of the light beam. In an illumination device for selectively transmitting only one of the included polarization components and irradiating the polarization component of the polarization component as readout light to the light modulation layer of the spatial light modulation device, the polarization selection surface of the polarization selection element and the space An illumination device for reading light with respect to a spatial light modulation device, wherein the light modulation layers of the light modulation device are arranged in an optically parallel relationship. 2. When a light refraction element is interposed between the polarization selection surface of the polarization selection element and the light modulation layer of the spatial light modulator, the polarization selection of the polarization selection element is performed in accordance with the refractive index. 2. The illumination device for reading light with respect to the spatial light modulation device according to claim 1, wherein the surface is inclined with respect to the light modulation layer of the spatial light modulation device. 3. The illumination device for reading light with respect to the spatial light modulation device according to claim 1, wherein the polarization selection element is a polarizing plate. 4. The illumination device for reading light with respect to the spatial light modulation device according to claim 1, wherein the polarization selection element is a polarization beam splitter.