JPH10170870A - Polarization element, light source device, and projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin polarization element with less loss by forming it into a shape connecting unit elements of a pole shape of which light-incident surface and light-outgoing surface are folded back at an angle transmitting P polarization light with a low loss at a fixed interval. SOLUTION: This polarization element 62 is formed so as to integrally connect pole-shaped elements 162 with a diamond-shaped section at the fixed interval, and a peak part of an incident side fold-back surface 63 and the peak part of an outgoing side fold-back surface 64 exist on the same positions in surface/rear side surface. A slope θi of an oblique side in the incident surface 63 and outgoing surface 64 of the polarization element 62 forms the angle transmitting the P polarization through with less loss and partially reflecting an S polarization. The outgoing surface 64 is the same shape as the incident surface 63, and when natural light 25 with undecided polarization direction is made incident on the polarization element 62 parallel to the normal N, though the P polarization transmits nearly through it, the S polarization is partially reflected by the incident surface 63 and outgoing surface 64. Then, outgoing light 26 becomes polarized polarization (partial polarization) with a strong polarization component of a P direction. Thus, the polarization element 62 converting the natural light 25 into the partial polarization is made thin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing element for converting natural light whose polarization direction is indefinite into partial polarized light whose polarization is large only in one direction.

[0002]

2. Description of the Related Art A liquid crystal light valve of the TN (Twisted Nematic) type is constructed by arranging polarizing plates before and after a liquid crystal layer. The polarizing plate has a function of transmitting only polarized light in one direction and absorbing polarized light in a direction orthogonal thereto. Generally, a plastic polarizing plate is often used, and a material obtained by adsorbing a dichroic substance such as an iodine compound or a dye onto a polyvinyl alcohol (PVA) film is oriented in one direction, and only polarized light in a specific direction is applied. It is configured to absorb

When natural light having an indeterminate polarization direction is incident on a liquid crystal light valve, half of the optical power is absorbed by a polarizing plate. In a projection display device using a liquid crystal light valve, the liquid crystal light valve is illuminated by a high-luminance light source, and light absorption by a polarizing plate is a factor for generating heat. If the polarizing plate is used at a temperature exceeding the heat-resistant temperature, the degree of polarization is reduced due to deformation or denaturation of the polarizing plate, and the image quality is largely deteriorated. In particular, in a liquid crystal light valve using a plastic polarizing plate, since the polarizing plate has heat resistance of only 80 to 90 ° C., it becomes an obstacle when illuminating with high illuminance and obtaining a high-luminance image.

As one method for solving this problem, there is a method of removing polarized light in unnecessary directions before a polarizing plate. This conventional example will be described with reference to FIG. Fig. 14
FIG. 1 is a diagram showing an optical system of a projection display device using a liquid crystal light valve, which is reported in JAPAN DISPLAY '89 DIGEST pp.646-649. The light source 120 emits the parallel light beam 2 using the parabolic mirror 13 and the like. The filter 12 cuts ultraviolet light and infrared light, and the polarizing element 6 called a prepolarizer converts the light beam 2 into partial polarized light in which natural light having an indeterminate polarization direction is large only in one direction.

Next, red (R), green (G) and blue (B) lights are separated by dichroic mirrors 7a and 7b, and the red light is reflected by a mirror 11a, and each light is condensed by a condenser. After focusing by the lenses 8r, 8g, 8b, two polarizing plates 17r,
LCD light valve sandwiched between 17g, 17b, 18r, 18g, 18b
Light is modulated by 3r, 3g, and 3b to form an image of three primary colors. Next, the blue light is reflected by the mirror 11b, the three primary color images are synthesized by the color synthesizing dichroic mirrors 9a and 9b, enlarged by the projection lens 4, and the color image is enlarged on a screen (not shown). Project.

FIG. 15 is a view showing a polarizing element 6, and the polarizing element 6 has a structure in which glass plates 61 are laminated. Glass plate 61
At the interface where the refractive index between the air layer and the glass plate layer is different, the incident angle (Brew) at which one of the linearly polarized light (P-polarized light) 22 is entirely transmitted and a part of the other linearly polarized light (S-polarized light) 21 is reflected. (Star angle). Polarization direction necessary for liquid crystal light valves 3r, 3g, 3b by stacking multiple glass plates 61,
That is, the polarizers 17r, 17g, 17b on the entrance side of the liquid crystal light valve
To generate a light beam of polarized light in the same direction as the polarization axis.

In the prior art, the polarizing element 6 removes in advance the polarization component (S-polarized light in FIG. 52) orthogonal to the polarization direction of the incident-side polarizers 17r, 17g, 17b of the liquid crystal light valve. This can reduce heat generation deterioration of the incident-side polarizing plates 17r, 17g, and 17b.

[0008]

The polarizing element 6 in the conventional example is constituted by a glass plate inclined at a Brewster angle with respect to the optical axis, typically about 57 ° (when the refractive index n = 1.52). I have. When a polarizing element is constituted by one glass plate, the depth D is required to be about 1.5 times the cross-sectional area of the light beam. Figure
When the structure is folded once as shown in FIG. 15, the depth D can be reduced to half. In order to increase the brightness of the projection display, the light source 120 should be
It is necessary to install near r, 3g, 3b. In the prior art, the large polarizing element 6 is an obstacle, and the realization of a thinner polarizing element is desired from the viewpoint of making the projection display device compact.

The present invention has been made in view of such circumstances, and has as its object to provide a polarizing element which is thin and has little loss.

[0010]

Means for Solving the Problems The polarizing element according to the first invention comprises:
The entrance surface and the exit surface are folded at an angle such that the P-polarized light is transmitted with low loss, and the element cross section is a shape in which rhombic columnar unit elements are connected at regular intervals, and the incident angle is further increased to Brewster angle or more. Angle. Further, the thickness and the turnback period of the polarizing element are optimized. Further, a plastic material is used as the material of the polarizing element. It is a light source device using a polarizing element of the present invention together with a filter for cutting off ultraviolet rays and infrared rays. Further, the present invention is a light source device in which the polarizing element of the present invention is forcibly cooled. Further, a plurality of polarizing elements are stacked, and a spacer is inserted between the polarizing elements. Further, a projection structure is formed integrally with a part of the polarizing element, and a spacer is used as a substitute, and an air layer is provided between the elements.

According to the polarizing element of the first aspect of the present invention, P
Since the shape is folded at an angle that transmits polarized light, the polarizing element is thin. When the incident angle is Brewster's angle, P
Polarized light is transmitted without loss, and the transmission efficiency of P-polarized light is improved by optimizing the thickness. When the incident angle is set to be equal to or larger than the Brewster angle, the P-polarized light is slightly lost, but the transmittance of S-polarized light is further reduced, so that the extinction ratio is improved. Further, by forming this polarizing element from a plastic material, a single layer element can be manufactured easily and inexpensively even in a complicated shape. Also,
By using an ultraviolet / infrared cut filter together and forcibly cooling, thermal deformation / denaturation of the polarizing element itself can be prevented. The extinction ratio is improved by stacking a plurality of polarizing elements. Further, by inserting a spacer between the polarizing elements to secure an air layer, deterioration of the extinction ratio due to multiple reflection is prevented.

In the polarizing element according to the second aspect of the present invention, the incident surface and the outgoing surface transmit the P-polarized light with low loss, the cross section of the device is formed into a triangular wave shape, and the incident angle is a Brewster angle or more. In addition, the thickness of the element and the return period are optimized.

According to the polarizing element of the second aspect of the present invention, since the cross-sectional shape is triangular, a structure having a uniform layer thickness and high mechanical strength is obtained. In addition, the thickness and the turnback period of the element are optimized so that the incident angle becomes the Brewster angle or more, so that the transmission efficiency of P-polarized light is improved.

Further, the projection type display device according to the third invention is characterized in that
The polarizing element of the invention or the second invention is provided between a light source and a liquid crystal light valve.

According to the projection display apparatus of the third invention, the first
By applying the polarizing element of the invention or the second invention,
Heat generation of the incident-side polarizing plate of the liquid crystal light valve can be reduced, and a compact and high-brightness projection display device can be realized.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. <First invention> (Polarizing element) Embodiment 1 FIG. 1 is a configuration diagram of a polarizing element according to Embodiment 1 of the first invention. The polarizing element 62 has a shape in which columnar elements 162 having a rhombic cross section are integrally connected at regular intervals, and the peaks (or valleys) of the entrance-side folded surface 63 and the peaks (or valleys) of the emission-side folded surface 64 are formed. Valley) part is the same position on the front and back. Note that a dashed line L in FIG. 1B is a polarizing element.
62 indicates a center line, and N indicates a normal to the center line L.
The inclination θi of the hypotenuse of the incident surface 63 and the exit surface 64 of the polarizing element 62 forms an angle at which the P-polarized light is transmitted with low loss and a part of the S-polarized light is reflected. Here, θi is the angle of the normal direction of the plane of incidence and emission with respect to the normal line N of the polarizing element 62. The outgoing surface has the same shape as the incident surface, and when natural light 25 having an indeterminate polarization direction is incident on the polarizing element 62 in parallel to the normal line N, the P-polarized light (polarized light in the horizontal direction in the paper of FIG. 1B) becomes Although almost transmitted, S-polarized light (polarized light perpendicular to the plane of the paper) is partially reflected at the entrance surface 63 and the exit surface 64. Therefore, the outgoing light 26 is polarized light (partially polarized light) having a strong polarization component in the P direction.

The incident angle at which 100% of the P-polarized light is transmitted is
As mentioned earlier, it is called the Brewster angle. Brewster angle θ at the interface between the air layer and the substrate layer having a refractive index of n
B is obtained by the following equation (1). θi = θB = tan ⁻¹ n (1)

FIG. 2 shows the transmittance T and the reflectance R of P-polarized light and S-polarized light with respect to the angle of incidence on the transparent substrate where n = 1.57.
When the incident angle θi is Brewster angle θB = 57.51 °, P
100% of the polarized light is transmitted, while about 18% of the S-polarized light is reflected at the interface.

FIG. 3 is a diagram showing a light beam transmitted through a rhombic columnar element 162 which is a unit element of the polarizing element 62. In order to realize the Brewster angle, the vertex angle θP of the rhombus is set as in equation (2). θP = π−2θB (2) The light beam 25a incident on the rhombic unit element 162 is incident on the incident surface 63.
After being refracted at the light exit surface 64, the light beam 26a is emitted. The light beam 25b incident on the outside of the light beam 25a passes through the unit element 162 like the light beam 26b, and becomes unnecessary light 26b. The hatched portions in the figure are regions that are invalid as polarizing elements. If the rhombic unit elements 162 are formed by connecting the diagonal portions so as to overlap and be integrated, light loss due to the diagonal portions can be eliminated.

Next, the optimum design of the cross-sectional shape of the polarizing element 62 shown in FIG. 1B will be described. As shown in FIG. 4A, the maximum thickness from the center line L is a, the minimum thickness is b, the return period of the incident surface is c, the refractive index of the material is n, and the Brewster angle obtained by the equation (1) is θB. Then, the P-polarized light passes through the element without loss if the relationship of the following equation (3) is satisfied. a: b: c = 1: 1 + 2COS (2θB) :−( 4 / n) COS (2θB) (3) As an example of a case where the above equation (3) is not satisfied, the thickness b is calculated according to the equation (3). When the size is small, a region that does not transmit light is generated as shown by a hatched portion in FIG. 4B, and a stripe-like shadow is formed. A light beam such as 25b is lost light.

In the first embodiment, the incident angle θi shown in FIG. 1B is set so as to form the Brewster angle θB.
When the incident angle θi is slightly larger than the Brewster angle, the rate at which S-polarized light can be removed increases. FIG. 5 is a diagram showing the relationship between the transmission ratio (extinction ratio) of P-polarized light and S-polarized light with respect to the angle of incidence on the substrate at n = 1.57. The transmittance decreases by 4%, but the extinction ratio increases by 15%. In this case, θP is changed from the value of 64.98 ° to the Brewster angle to 40 °. Naturally θ
Since P is larger than 0 °, θP may be set in the range of 0 <θP ≦ π−2θB.

The material of the polarizing element 62 may be any material that is transparent to a desired light wavelength. In the visible light region, there are glass materials, plastic materials, and the like. In terms of heat resistance, it is advantageous to form or polish a glass material. A plastic material is advantageous in that a complicated shape can be easily formed. As a plastic material which is transparent in the visible light region and has a small absorption loss and excellent optical characteristics, there are polymethyl methacrylate (PMMA), polystyrene (PS), polycarbonate (PC) and the like. When heat resistance becomes a problem when irradiated with a high-intensity light source, for example, a thermoplastic resin ARTON (trade name, manufactured by Nippon Synthetic Rubber Co., Ltd., weighted deflection temperature of 164 ° C.) or a high heat-resistant polycarbonate Apec HT (Bayer Company, (trade name),
(Weighted deflection temperature 141-215 ° C).

The plastic material has a large absorption in the ultraviolet region, and when irradiated with high-intensity light containing a large amount of ultraviolet light, it causes heat generation. Known UV / IR cut filter with polarizing element
By irradiating the polarizing element 62 with natural light 25 while blocking light including infrared light by placing it on the light source side of the incident surface 63 of 62, the temperature rise of the material can be reduced, and the thermal deformation of the polarizing element 62 And denaturation can be prevented.

The polarizing element may be forcibly cooled by air cooling or the like by using a known fan, and the cooling effect is further enhanced by using the ultraviolet / infrared cut filter in combination.

Embodiment 2 FIG. 6 is a sectional view showing a polarizing element according to the second embodiment of the first invention. Embodiment 2
1 is a stack of three polarizing elements 62 shown in FIG.
The ratio at which unnecessary polarization components (S-polarized light) can be removed increases.

FIG. 7 is a diagram showing the intensity ratio between P-polarized light and S-polarized light when natural light according to the second embodiment is incident, as an extinction ratio / polarization degree. Since the S-polarized light is removed on two surfaces of the polarizing element 62, ie, the incident surface and the outgoing surface, five devices (substrate refractive index n = 1.57, incident angle θi = 57.51 °) shown in the first embodiment are used. If laminated, the intensity of S-polarized light will be 15% or less of P-polarized light. The number of stacked layers may be set as appropriate with reference to the extinction ratio in FIG.

When the thickness a of the optical element in the first embodiment is 1 mm, the thickness b is 0.15 mm according to the equation (3).
Even if five such devices are stacked, the layer thickness is 6.6 mm. on the other hand,
In FIG. 15 showing a conventional example, if the width of the liquid crystal light valve (or the width of the illuminating light beam) is 40 mm, the depth D of the polarizing element 6 is 30.8 mm or more. It can be seen that it can be achieved. Moreover, the polarizing element of the second embodiment does not change even if the width of the liquid crystal light valve (or the width of the illumination light beam) increases. on the other hand,
In the conventional polarizing element, the depth D of the polarizing element increases in proportion to the width of the liquid crystal light valve (or the width of the illumination light beam).

Embodiment 3 FIG. 8 is a sectional view showing Embodiment 3 of the first invention, and FIG. 9 is a sectional view taken along line bb of FIG. As in the second embodiment, a plurality of polarizing elements 62 are stacked, but the spacer 65 is placed at a position that does not interfere with the optical path.
Is inserted to secure the air layer 66 between the polarizing elements 62. 2
When the two polarizing elements 62 come close to each other, the S-polarized light 26s transmitted through the polarizing elements 62 undergoes multiple reflection between the polarizing elements 62 and becomes transmitted light again, so that the degree of polarization is reduced. Further, when the thickness of the air layer 66 is on the order of the wavelength, the air layer 66 functions as an interference film, causing a change in color of transmitted light and color unevenness. As shown in FIG.
In order to prevent the S-polarized light 26s reflected and separated at b from being reflected again at the light exit surface 64a, the gap d is set to 0.32 mm or more by using the polarizing element 62 of Embodiment 2 (a design example of thickness a = 1 mm). What is necessary is just to insert such a spacer 65.

Embodiment 4 FIG. 10 is a sectional view showing Embodiment 4 of the first invention, and FIG. 11 is a sectional view taken along line bb of FIG. Instead of the spacer 65 used in the third embodiment, a projection 67 is provided on a part of the polarizing element 62, and the spacer is formed integrally with the polarizing element 62. If a plastic material is used, integral molding of the spacer can be relatively easily performed.

In the third and fourth embodiments, each of the air layers 66
If the air is blown using a known fan or the like as an air path, there is an effect that the polarizing element can be efficiently cooled.

<Second Invention> (Polarizing Element) FIG. 12 is a sectional view showing a polarizing element of the second invention. In the polarizing element 68, the ridge (or valley) of the incident-side folded surface 69 and the valley (or ridge) of the emission-side folded surface 70 are in a relationship in which the front and back surfaces of the element coincide. For this reason, the entire cross-sectional shape becomes a triangular wave shape, and the layer thickness is uniform, so that the structure has high mechanical strength. In order for the incident surface to form the Brewster angle θB, the turning angle θP between the incident surface 69 and the exit surface 70 is given by the following equation (4). θP = π−2θB (4)

The maximum thickness from the center is a, the minimum thickness is b,
Assuming that the return period is c, when the following expression (5) is satisfied, the P-polarized light passes through the polarizing element 68 without loss. a: b: c = 1: {2 + 3COS (2θB)} / {2 + COS (2θB)}: − {4COS (2θB)} / [n {2 + COS (2θB)}] (5)

In addition, the extinction ratio can be improved by setting the incident angle to a Brewster angle or more. The material of the polarizing element 68 and an example in which the polarizing element 68 is used by lamination, spacers and the like are described in Embodiment 1 of the first invention. Same as 2, 3, and 4.

<Third Invention> (Projection Display Device) FIG. 13 is a diagram of an optical system of a projection display device using a polarizing element according to the third invention. FIG. 13 is different from FIG. 14 showing a conventional example in that a polarizing element is changed. light source
120 emits the parallel light beam 2 using the parabolic mirror 13 and the like. UV and infrared rays are cut by the filter 12,
A polarizing element in which a plurality of the above-described polarizing elements 62 or 68 are stacked
According to 16, the light beam 2 is converted from natural light having an indeterminate polarization direction into partial polarization in which the polarization direction is large only in one direction. Red (R), green (G), blue (B) by dichroic mirrors 7a and 7b
After being separated into three colors of light, the red light is reflected by a mirror 11a, and each light is condensed by condenser lenses 8r, 8g, 8b, and then two polarizing plates 17r, 17g, 17b, 18r, 18g , 18b, and light is modulated by the liquid crystal light valves 3r, 3g, 3b to form an image of three primary colors. Next, the blue light is reflected by the mirror 11b, and the three primary color images are converted into a dichroic mirror for color synthesis.
The images are synthesized by 9a and 9b, enlarged by the projection lens 4, and the color image is enlarged and projected on a screen (not shown).

The polarizing elements 62 and 68 of the first or second invention described above or the polarizing element 16 obtained by laminating a plurality of the polarizing elements 62 and 68 are
If the polarizing element 6 of the conventional device (FIG. 14) is substituted, the light source 12
Since 0 can be set closer to the liquid crystal light valve, the device can be made compact, and the illuminance of the liquid crystal light valve can be increased, so that a high-brightness projection display device can be realized. Although the polarizing element 16 in FIG. 13 shows an example of a three-layer configuration,
As the number of layers is increased, the extinction ratio (degree of polarization) becomes better, and the incident side polarizing plates 17r, 17g, 17b of the liquid crystal light valves 3r, 3g, 3b.
Heat generation can be reduced.

[0036]

As described above in detail, according to the first aspect, since the front and back surfaces are formed by folding the P-polarized light at an angle that transmits the P-polarized light with low loss, the optical element that converts natural light into partially polarized light is provided. Becomes thin. Further, by setting the apex angle θP so that the incident angle and the outgoing angle of the polarizing element become the Brewster angle, P-polarized light can be transmitted through the element interface without loss. Further, by designing the thickness and the turn-back period of the element to optimal values according to the equation (3), the P-polarized light can be transmitted through the polarization element without loss. Further, by setting θP smaller than the expression (2) in order to set the incident angle and the output angle to the polarizing element to be equal to or larger than the Brewster angle, the transmittance of P-polarized light is slightly reduced.
The extinction ratio can be improved.

By using a plastic material as the material of the polarizing element, a complicated shape can be produced relatively easily and inexpensively as compared with a glass material or the like. When polarizing high-intensity white light with a polarizing element made of plastic material,
By using the infrared cut filter together, it is possible to reduce the deformation and denaturation of the polarizing element due to the temperature rise. Furthermore, if forced cooling such as air cooling is performed, the effect of reducing deformation and denaturation of the polarizing element is enhanced. In addition, since one polarizing element is thin, the polarizing element is thin even when a plurality of polarizing elements are stacked, and the extinction ratio can be improved with an increase in the number of layers. Furthermore, by inserting a spacer to secure an air layer between the elements, multiple reflection of S-polarized light between the elements can be removed, and the extinction ratio can be improved. In addition, if the air layer is used as an air path and cooled by blowing air, the thermal deformation of the polarizing element can be reduced. Also, if the polarizing element and the spacer are integrally formed, the assembly process of the polarizing element can be reduced.

Further, according to the second aspect of the present invention, by forming the cross section of the polarizing element into a triangular wave shape, the thickness of the polarizing element becomes uniform and a structure having high mechanical strength is obtained. Further, by setting the incident angle and the outgoing angle of the polarizing element to the Brewster angle as in the first invention, the P-polarized light can be transmitted through the element interface without loss. Further, by designing the thickness and the turn-back period of the element to optimal values, the P-polarized light can be transmitted through the polarizing element without loss.

According to the third aspect, the polarizing element of the first aspect or the second aspect is applied to a projection type display device using a liquid crystal light valve, so that the heat of the polarizing plate on the liquid crystal light valve incident side is generated. Is reduced, and image quality deterioration due to denaturation or deformation of the polarizing plate can be prevented. In addition, since the polarizing element is thin, the light source can be installed close to the liquid crystal light valve, so that a high-brightness projected image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a polarizing element of the present invention.

FIG. 2 is a graph showing a relationship between an incident angle on a transparent substrate, transmittance, and reflectance.

FIG. 3 is an explanatory diagram of a light beam transmitted through a columnar element which is a unit element of a polarizing element.

FIG. 4 is an explanatory diagram of a light beam transmitted through a polarizing element.

FIG. 5 is a graph showing the relationship between the angle of incidence on a transparent substrate and the extinction ratio.

FIG. 6 is a cross-sectional view illustrating a configuration of a polarizing element of the present invention.

FIG. 7 is a graph showing the relationship between the number of stacked polarizing elements and the degree of polarization.

FIG. 8 is a cross-sectional view illustrating a configuration of a polarizing element of the present invention.

FIG. 9 is a sectional view taken along line bb of FIG. 8;

FIG. 10 is a cross-sectional view illustrating a configuration of a polarizing element of the present invention.

FIG. 11 is a sectional view taken along line bb of FIG. 10;

FIG. 12 is a cross-sectional view illustrating a configuration of a polarizing element of the present invention.

FIG. 13 is a diagram showing an optical system of the projection display device of the present invention.

FIG. 14 is a diagram showing a configuration of another conventional projection display device.

FIG. 15 is a view showing a conventional polarizing element.

[Explanation of symbols]

3r, 3g, 3b LCD light valve, 4 projection lens, 12
Filter, 16 polarizing element, 62 polarizing element, 65 spacer, 66 air layer, 67 protrusion, 68 polarizing element, 120 light source, 162 columnar element.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03B 33/12 G03B 33/12 H04N 5/74 H04N 5/74 A

Claims (15)

[Claims] 1. A polarizing element for converting natural light having an indeterminate polarization direction into partial polarization having a large polarization in only one direction, wherein the incident surface and the emission surface are folded at an angle such that the P-polarized light is transmitted with low loss. A polarizing element, wherein unit elements are formed in a shape connected at regular intervals. 2. The polarizing element according to claim 1, wherein the cross-sectional shape of the columnar unit element is a rhombus. 3. The apparatus according to claim 2, wherein the angle of incidence and the angle of emergence are equal to each other and form a Brewster angle .theta.B, and a pair of opposed apex angles .theta.P of the diamond-shaped unit element satisfy the following condition. Polarizing element. θP = π−2θB where θB = tan ⁻¹ nn where n is the refractive index of the polarizing element substrate 4. The polarizing element according to claim 2, wherein the relationship between the maximum thickness a from the center, the minimum thickness b, and the turnback period c is set as follows. a: b: c = 1: 1 + 2 COS (2θB) :−( 4 / n) C
OS (2θB) 5. The angle of incidence and the angle of emission are Brewster angles θB.
3. The polarizing element according to claim 2, wherein the pair of opposing apex angles .theta.P of the diamond-shaped unit element satisfy the following condition. 0 <θP ≤π-2θB 6. A cross-sectional shape of the columnar unit element is a triangular wave shape in which a position of a valley (valley) of an incident surface and a position of a valley (peak) of an emission surface coincide in an element plane. Claim 1
The polarizing element as described in the above. 7. The device according to claim 6, wherein the incident angle and the output angle are equal to each other and form a Brewster angle θB, and the turning angle θP of the triangular wave-shaped portion of the unit element satisfies the following condition. Polarizing element. θP = π−2θB where θB = tan ⁻¹ nn where n is the refractive index of the polarizing element substrate 8. The polarizing element according to claim 7, wherein the relationship among the maximum thickness a from the center, the minimum thickness b, and the turnback interval c satisfies the following conditions. a: b: c = 1: {2 + 3COS (2θB)} / {2 + COS (2
θB)｝: − {4COS (2θB)} / [n ｛2 + COS (2θ
B)｝] 9. The polarizing element according to claim 1, wherein the polarizing element is formed of a plastic material. 10. A light source device comprising: the polarizing element according to claim 9; a light source that emits natural light; and an ultraviolet / infrared cut filter provided between the polarizing element and the light source. 11. A light source device comprising: the polarizing element according to claim 9; a light source that emits natural light; and a fan that blows and cools the polarizing element. 12. The polarizing element according to claim 1, wherein a plurality of the polarizing elements are stacked. 13. The polarizing element according to claim 12, wherein a spacer is inserted between the plurality of stacked polarizing elements. 14. The polarizing element according to claim 1, wherein a projection structure serving as the spacer is integrally formed with the polarizing element.
3. The polarizing element according to 3. 15. The polarized light according to claim 1, wherein the projection type display device enlarges and projects an image of the liquid crystal light valve illuminated by the light source onto a screen by a projection lens. A projection display device comprising an element.