JPH11260142A - Polarization converting device and polar screen element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a polarization converting device capable of converting natural light to one directional linearly polarized light with high efficiency of nearly 100% by a small optical system without optical axis separation of emitted light. SOLUTION: When the light from a light source is incident on a polarization beam splitter 23, P polarized light penetrates the polarization beam splitter 23 to come to the front, and S polarized light is reflected to the side of the polarization beam splitter 23. A regression reflector 24 is provided on the side of the polarization beam splitter 23, and the S polarized light is reflected by the regression reflector 24, further it is reflected by the polarization beam splitter 23 to get back to the light source 22. The light source 22 is composed of a light emitting body 25, a curved surface reflector element 26 and a hemispherical reflector element 27, and the S polarized light regressed to the light source 22 is reflected by the curved surface reflector element 26 and the hemispherical reflector element 27 to be converted to elliptically polarized light, thus it is incident on the polarization beam splitter 23 again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polarization conversion device and a polarization filter element. Specifically, the present invention relates to a technique for converting two linearly polarized light beams whose polarization directions are orthogonal to each other into linearly polarized light beams having the same polarization direction and emitting the same.

[0002]

2. Description of the Related Art A projection television is shown in FIG.
As shown in FIG. 1B, a liquid crystal projector 1 installed on the front projects light R toward a screen 2 so that an image can be viewed from a projection direction. There is a rear projection type in which light R is projected onto a screen 2 from a liquid crystal projector 1 installed on the back using a pair of mirrors 3 and 4 so that an image can be viewed from the front side.

FIG. 2 is a diagram showing a configuration of the liquid crystal projector 1. The difference between the front projection type projection television and the rear projection type projection television is only the presence or absence of the mirrors 3 and 4, and the principle configuration is the same. A lamp 5 such as a metal halide lamp shown in FIG. 2 is disposed at a focal position of a reflector 6. The reflector 6 has a parabolic mirror, and the light R of the lamp 5
Is reflected to make parallel light. A liquid crystal display panel 9 sandwiched between polarizers 7 and 8 is disposed in front of the reflector 6, and is configured to project light R onto the screen 2 via a projection lens 10.

However, a liquid crystal projector using a liquid crystal display panel has an advantage that a large screen can be realized at low cost as compared with a cathode ray tube, but has an essential disadvantage that a screen is dark. In particular, as a liquid crystal display panel,
A TN (twisted nematic) type liquid crystal panel having high contrast and multi-gradation characteristics is used. This TN type liquid crystal display panel controls the flow of light by a polarizing plate. Since only the polarization component in the direction is allowed to pass, there is a problem that 50% of the light of the light source light is unconditionally lost by the polarizing plate on the incident side.

[0005] In order to prevent the light amount loss due to such a polarizing plate, a polarization conversion optical element as shown in FIG. 3 has been conventionally considered. This polarization conversion optical element can input natural light containing both P-polarized light effective for image display and S-polarized light that is completely lost, and can convert the total amount of light into P-polarized light and output it. Therefore, the use efficiency of light in the liquid crystal display panel becomes almost 100% by using such a polarization conversion optical element.

The polarization conversion optical element 11 shown in FIG. 3 is constituted by one polarization beam splitter (PBS) 12 and four right-angle prisms 13, 14, 15, and 16.
Natural light from the light source is split by the polarizing beam splitter 12 into two linearly polarized light components whose polarization directions are orthogonal to each other. The polarizing beam splitter 12 has a structure in which a dielectric multilayer film is deposited on one slope of two right-angle prisms and the slopes are joined to each other. The light transmitted through the slope is P-polarized light, and the light reflected by the slope is S-polarized light.

The P-polarized light transmitted through the polarizing beam splitter 12 sequentially enters right-angle prisms 13 and 14. In the process of performing total internal reflection twice on the inclined surfaces of the right-angle prisms 13 and 14, if the inclination direction of the reflection surfaces is rotated by 90 degrees, the polarization direction of light is rotated by 90 degrees. By rotating the polarization direction by 90 degrees, the polarization direction of the light incident on the right-angle prism 13 is horizontal (P polarization), whereas the polarization direction of the light emitted from the right-angle prism 14 is vertical (S polarization). It has become.

On the other hand, the S-polarized light reflected by the inclined surface of the polarizing beam splitter 12 sequentially enters the right-angle prisms 15 and 16 and, as in the case of the P-polarized light, the right-angle prisms 15 and 16.
Is totally reflected twice on the slope. However, since the arrangement of the reflecting surfaces is parallel to each other, the polarization direction does not change.
Accordingly, the polarization direction of the light exiting the right-angle prisms 15 and 16 is equal to the polarization direction (S-polarization) of the light incident on the right-angle prism 15 and is perpendicular (S-polarization). As a result, the two linearly polarized lights split by the polarizing beam splitter 12 are:
Both have the same polarization direction and the traveling directions are equal. As a result, almost 100% of the light emitted from the light source is
The light is converted into linear polarized light in one direction and projected.

[0009]

However, the conventional polarization conversion optical element 11 has a prism 1 as shown in FIG.
Since the light sources 4, 15, and 16 are protruding, the optical system becomes much larger in comparison with the case where only the light source is used. For this reason, there are problems that it is difficult to reduce the size of the polarization conversion optical element and that the cost of the polarization conversion optical element is high.

Furthermore, the optical axes of the two linearly polarized lights whose polarization directions have been aligned are separated into two axes, and the light beam has spread widely as a whole. For this reason, it is difficult to stop the emitted light beam, and if the light beam is to be stopped, the lens diameter and the lens thickness are increased, and the cost is high. In addition, if the light beams are not stopped down, it is insufficient to couple the two light beams to the one-axis optical system, and there is a problem that the image quality of a liquid crystal display panel or the like deteriorates.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object thereof is to provide a polarization conversion device which can be realized by a smaller optical system and has no separation of optical axes. It is in. Another object of the present invention is to provide a polarization filter element used for the polarization conversion device.

[0012]

DISCLOSURE OF THE INVENTION A light source having a function of generating light, converting incident linearly polarized light into non-linearly polarized light or linearly polarized light having a different polarization direction and reflecting the light, and a light source. Polarization splitting means for splitting the light into two linearly polarized lights having different polarization directions and emitting one of the linearly polarized lights to the outside, and a polarization recovery means for guiding the other linearly polarized light separated by the polarization separating means to the light source. It is characterized by having.

In the polarization conversion device of the present invention, the light emitted from the light source is separated into two linearly polarized lights by the polarization separating means, one of the linearly polarized lights is emitted to the outside, and the other is returned to the light source. Since the state of polarization is changed by the light source and the light is again incident on the polarization separation means, only linearly polarized light in one polarization direction can be emitted. Also, the light in the other polarization direction is converted into a polarization direction that can be emitted while reciprocating between the polarization separation means and the light source. Therefore, natural light can be converted into linearly polarized light aligned in one direction with high conversion efficiency. Moreover, the linearly polarized light to be emitted is not biaxial as in the conventional example, but can be linearly polarized light of one axis. Therefore, the emitted light can be narrowed down easily and the polarization converter can be downsized. be able to.

According to a second aspect of the present invention, in the polarization converter according to the first aspect, the light source rotates the luminous body and the polarization direction of linearly polarized light incident on the light source by approximately 90 degrees. And a reflecting element having a function of emitting light from a light source.

In this embodiment, the light returned to the light source from the polarization separation element side is rotated by 90 degrees by the light source and is incident on the polarization separation element again. The light is emitted from the element. Therefore, the number of round trips of light between the polarization separation side and the light source can be reduced, and the light can be efficiently converted into linear polarized light in one direction.

According to a third aspect of the present invention, in the polarization conversion device according to the first aspect, the polarization separation means comprises a polarization beam splitter, and the polarization recovery means faces the side surface of the polarization beam splitter. The light source is provided with a light reflecting means, and the light source and the light reflecting means are conjugated to each other.

If the light source and the light reflecting means are conjugated to each other, the linearly polarized light not emitted from the light source is collected by the light reflecting means, and the light reflected by the light reflecting means is also transmitted to the light source. Since the light is collected, the amount of light hardly decreases while the light is reciprocated between the light source and the light reflecting means, and the conversion efficiency to linearly polarized light can be increased.

According to a fourth aspect of the present invention, in the polarization filter element, a regression reflection plate is disposed to face one surface of the polarization beam splitter,
The light incident on the polarizing beam splitter is split into two linearly polarized lights having different polarization directions by the polarizing beam splitter, and one linearly polarized light is emitted from the polarizing beam splitter, and the other linearly polarized light is guided to the regression reflection plate. The reflected linearly polarized light is returned to the polarization beam splitter and is reversed in the first incident direction.

This polarization filter element is used as polarization separation means and polarization recovery means in the polarization conversion device of the first aspect. In addition, since a recursive reflection plate is used as the polarization recovery means, the linearly polarized light that has not been emitted from the polarization separation means can be accurately returned to the original direction, so that the light amount loss is reduced and the conversion efficiency to the linearly polarized light is reduced. Is improved.

[0020]

FIG. 4 is a perspective view showing a polarization converter 21 according to one embodiment of the present invention, and FIG. 5 is a schematic sectional view thereof. The polarization conversion device 21 includes a light source 22, one polarization beam splitter 23, and one return reflection plate 24. The light source 22 is a luminous body 2 such as a lamp.
5 and a curved reflecting element 2 composed of a parabolic mirror, an elliptical mirror, etc.
6. A hemispherical reflecting element 27 having a hemispherical shape. The light emitted from the light emitter 25 is reflected by the curved surface reflection element 2.
6, or after being reflected by the curved reflecting element 26 and the hemispherical reflecting element 27, while being focused, the polarization beam splitter 2
The light is emitted to the third side.

The light that has entered the polarization beam splitter 23 is separated into two linearly polarized lights whose polarization directions are orthogonal to each other, and the S-polarized light is inclined 23 a in the polarization beam splitter 23.
, And the P-polarized light is transmitted through the inclined surface 23a and emitted toward the liquid crystal display panel 28 in front. The regression reflection plate 24 is disposed so as to face the side surface of the polarization beam splitter 23 on the side where the S-polarized light reflected on the inclined surface 23a comes out. The retroreflector 24 may be bonded to the side surface of the polarization beam splitter 23. The retroreflective plate 24 is constituted by a prism array in which prisms having a vertical angle of 90 degrees are arranged.

The retroreflector 24 is arranged so as to have a conjugate positional relationship with the light source 22. That is, the light emitted from the light source 22 converges on the reflection surface of the regression reflector 24, and conversely, the light emitted from one point of the regression reflector 24 converges on the light source 22.

Next, the outline of the operation of the polarization conversion device 21 will be described with reference to FIGS. 6 (a), 6 (b) and 6 (c). Luminous body 2
When light is emitted from the light source 22 to emit natural light, the natural light reflected by the curved reflecting element 26 enters the polarization beam splitter 23. When natural light enters the polarization beam splitter 23, as shown in FIG. 6A, the natural light is split into two linearly polarized lights having polarization directions orthogonal to each other, and one of the linearly polarized lights, that is, the P-polarized light, passes through the polarization beam splitter 23. The other linearly polarized light, that is, the S-polarized light is reflected by the inclined surface 23 a of the polarization beam splitter 23. The S-polarized light reflected by the polarization beam splitter 23 enters the regression reflection plate 24 on the side surface, is reflected by the regression reflection plate 24 as S-polarized light, and enters the polarization beam splitter 23 again. The S-polarized light that has entered the polarization beam splitter 23 again is reflected by the inclined surface 23a, and returns to the light source 22.

The S-polarized light returned to the light source 22 side is shown in FIG.
As shown in the figure, the curved reflecting element 26 and the hemispherical reflecting element 2
After being reflected at 7, the light is emitted again from the light source 22. Since the curved surface reflection element 26 and the hemispherical reflection element 27 are made of metal, the light emitted from the light source 22
Elliptical polarization is obtained by repeating reflection at 6 and the hemispherical reflecting element 27.

The elliptically polarized light emitted from the light source 22 is shown in FIG.
As shown in (1), the P-polarized light component enters the polarization beam splitter 23, passes through the polarization beam splitter 23, and the S-polarized light component is reflected by the polarization beam splitter 23. The S-polarized light reflected by the polarization beam splitter 23 is reflected by the retroreflector 2
4, the light is reflected again by the polarization beam splitter 23, and returns to the light source 22 side.

This polarization converter 21 is shown in FIG.
By repeating the steps (b) and (c), only the P-polarized light is emitted forward, and the S-polarized light is also emitted forward from the polarization beam splitter 23 while being gradually converted to P-polarized light.
Therefore, theoretically, natural light emitted from the light
It is possible to convert the light into% P polarized light and emit it forward. In addition, since the linearly polarized light emitted from the polarization conversion device 21 is uniaxial and emitted as one light beam, there is no need to overlap the light beams as in the conventional example, It can also be squeezed easily by the method described above.

In this polarization conversion device 21, what is required other than the light source 22 is a polarization beam splitter 23.
And the retroreflective plate 24 alone, which is very small compared to a conventional polarization conversion optical element.

Next, the operation of each component of the polarization converter 21 based on the above principle will be described in detail. First, the regression reflection plate 24 will be described. The retroreflective plate 24 is formed of a transparent optical resin having a large refractive index in the form of a plate, and has a triangular prism-shaped uneven stripe arranged on the back surface (this unevenness has a refractive index as shown in FIG. 8). Small resin 3
0 may be filled in), and the apex angle of each prism 29 is 90 degrees. When a light beam enters the recursive reflection plate 24, the light beam enters the prism 29, is reflected twice on the inclined surface, and is reflected in the original direction. In addition, since the prism 29 is a triangular prism having a vertex angle of 90 degrees, the reflected light is shifted by a maximum of one pitch from the incident light, but the reflected light returns in a direction parallel to the incident light regardless of the direction of the incident light.

S reflected by the polarizing beam splitter 23
As means for returning the polarized light to the polarizing beam splitter 23 again, a metal mirror can be used.
Since the (light-emitting body 25) is not an ideal point light source, if a normal metal mirror is used, the S-polarized light returning to the light source 22 will be deviated from the light source 22 and will not be captured by the light source 22, resulting in a large loss. In addition, the metal mirror itself has poor reflectance (70).
８０80%), the loss is further increased.

On the other hand, if the retroreflector 24 is used,
Since the beam direction does not change when returning the S-polarized light to the polarization beam splitter 23, the S-polarized light can be collected in the light source 22 without escaping to the outside of the polarization conversion device 21, and the efficiency of the polarization conversion device 21 can be increased. it can. Further, since the total reflection by the prism 29 is used, the reflectance is high, and the loss can be made very small as compared with a metal mirror.

When an ordinary metal mirror is used to reflect the S-polarized light to the polarization beam splitter 23, the light reflected back to the polarization beam splitter 23 becomes elliptically polarized light, so that all the light does not return to the light source 22 side. , Part of elliptically polarized light (P
The polarized light component passes through the polarization beam splitter 23 and becomes a loss.

On the other hand, as shown in FIG. 9, the retroreflector 24 receives linearly polarized light whose polarization direction is parallel to the longitudinal direction of the prism 29, or as shown in FIG. When the linearly polarized light parallel to the short side direction of the incident light is incident, the polarization direction of the reflected linearly polarized light does not change, but as shown in FIG.
When the linearly polarized light rotated by 45 degrees with respect to the longitudinal direction is incident, the polarization direction of the reflected linearly polarized light is rotated by 90 degrees. Therefore, if the retroreflector 24 disposed on the side surface of the polarizing beam splitter 23 is set so that the longitudinal direction or the shorter direction of the prism 29 is parallel to the polarization direction of the incident S-polarized light, the polarized beam The light returning to the splitter 23 is almost completely reflected by the polarizing beam splitter 23 to the light source 22 side, and no loss occurs.

Next, the curved reflecting element 26 and the hemispherical reflecting element 27 of the light source 22 will be described. At least the surface (reflection surface) of the curved surface reflection element and the hemispherical reflection element 27 is made of metal and the direction of the crystal axis is random (there is no crystal axis). Then, the reflected light becomes elliptically polarized light. In the configuration of this polarization conversion device 21, S returned from the polarization beam splitter 23
The polarized light is reflected twice by the curved reflecting element 26 and the hemispherical reflecting element 27.
Is reflected three times in total, so that the S-polarized light becomes elliptically polarized light having a considerably high ellipticity and returns to the polarization beam splitter 23. Therefore, when the light again enters the polarization beam splitter 23, the rate of transmission of the P-polarized light through the polarization beam splitter 23 is significantly increased. Note that the curved reflection element 26
As the metal material of the hemispherical reflective element 27, it is preferable to use aluminum having a high reflectance over almost the entire visible light region.

As a further feature of the polarization converter 21, the light source 22 and the retroreflector 24 are arranged so as to have a conjugate positional relationship. By maintaining such a conjugate relationship, the S
Since the polarized light is collected by the light source 22, the light returns to the light source 22 side S
Preventing the polarized light from leaking out of the polarization conversion device 21 and escaping,
Conversion efficiency can be improved.

Further, since the light source 22 and the retroreflector 24 are located at conjugate positions, as shown in FIG. 12, the light incident on the polarizing beam splitter 23 is such that the S-polarized component converges on the retroreflector 24. , At a certain angle. In order to reduce the size of the polarization conversion device 21 (that is, the distance between the light source 22 and the polarization beam splitter 23), the condensing angle θ may be increased. On the other hand, the polarization beam splitter 23 has an angle dependency of incident light, and ideally, the condensing angle θ is desirably small. So, actually,
The condensing angle θ is designed to take as large an angle as possible within the allowable range of the polarizing beam splitter 23. Specifically, when a currently available polarizing beam splitter that has the gentlest incident light angle dependency is used, the condensing angle θ can be up to about 20 to 30 degrees.

As shown in FIG. 13, by forming a plurality of triangular prisms 29 having a vertical angle of 90 degrees on the surface of one triangular prism constituting the polarizing beam splitter 23 in parallel, the retroreflective plate 24 and the polarization Beam splitter 23
May be used.

Further, as shown in FIG. 14, a plurality of triangular prisms 29 having a vertical angle of 90 degrees are formed in parallel on the side surface of the polarizing beam splitter 23 with an ultraviolet curable resin, so that the retroreflective plate 24 and the polarizing beam splitter 23 are formed. A polarization filter element integrated with the splitter 23 may be used.

In these cases, the pitch Lp of the prism 29
The smaller the better, the better. The reason is,
This is because when the pitch Lp is small, the intensity distributions of the incident light and the reflected light become substantially equal. Also, in order to focus the light on the surface of the regression reflection plate 24, if the pitch Lp of the prism 29 is large, the deviation of the optical axis of the reflected light with respect to the incident light cannot be ignored. With the current technology, a sufficiently small pitch of about 30 μm can be realized.

(Second Embodiment) FIG. 15 is a plan view showing a configuration of a polarization conversion device 21 according to another embodiment of the present invention. In this polarization conversion device 21, a regression reflection plate 24 is disposed on the side of the polarization beam splitter 23 opposite to the surface on which light from the light source 22 is incident, and the P-polarized light reflected by the polarization beam splitter 23 is returned to the light source 22. Only the S-polarized light reflected by the light source is extracted forward.

(Third Embodiment) FIG. 16 is a schematic sectional view showing the structure of a light source 22 according to still another embodiment of the present invention. In this light source 22, the hemispherical reflecting element 2
As shown in FIG. 17, a vertex angle 90 whose longitudinal direction extends in an oblique direction of 45 degrees (that is, inclined 45 degrees with respect to the polarization direction of the S-polarized light returning from the polarization beam splitter 23) is formed on the inner surface of the substrate 7. Degree prisms are arranged in an array. On the other hand, as the curved surface reflection element 26, one that does not convert incident linearly polarized light into elliptically polarized light and reflects it while maintaining the polarization direction as it is as much as possible is used.

Therefore, the polarization beam splitter 23 outputs S
When the polarized light returns, S reflected by the curved reflecting element 26
When the polarized light is incident on the hemispherical reflecting element 27, as shown in FIG. Is emitted from. in this way,
The S-polarized light returned from the polarization beam splitter 23 is converted into P-polarized light and is incident on the polarization beam splitter 23 again. Therefore, most of the S-polarized light passes through the polarization beam splitter 23. Therefore, since elliptically polarized light does not occur in the light source 22, the light between the polarization beam splitter 23 and the light source 22
The number of light reciprocations is reduced, and the light amount loss at the time of reflection and the light amount loss due to optical axis shift can be reduced.

In the embodiments shown in FIGS. 16 to 18, the hemispherical reflecting element 27 is provided with a function of rotating the polarization direction of linearly polarized light. And the curved reflection element 2
In step 6, the linearly polarized light may be rotated by 45 degrees. That is, as shown in FIG. 19, the triangular prisms 32 are arranged in an array on the inner surface of the curved reflecting element 26 and reflected by this prism 32 so that the polarization direction of the incident linearly polarized light is rotated by 45 degrees. For example, the S-polarized light returned from the polarization beam splitter 23 is converted into P-polarized light and then enters the polarization beam splitter 23 again. However, in the case of the curved reflecting element 26, the vertex angle of the prism 32 differs depending on the location, and is larger in the peripheral part than in the central part.
For example, the vertex angle of the central prism 32 shown in FIG.
_2, if the apex angle of the prism 32 of the periphery phi ₁ and, phi ₂ <
φ ₁

(Fourth Embodiment) FIG. 20 is a schematic sectional view showing the structure of a light source 22 according to still another embodiment of the present invention. In the light source 22, the curved reflection element 26
A prism 33 having a radial pattern as shown in FIG. The apex angle of this pattern is designed to reflect the incident linearly polarized light by rotating it by 45 degrees. The S-polarized light returned from the polarization beam splitter 23 is
Since the light is reflected twice by the curved surface reflection element 26 and the polarization direction is rotated by 90 degrees, it is converted into P-polarized light and re-enters the polarization beam splitter 23, and most of the polarization beam splitter 23
Will be transmitted. Accordingly, no elliptically polarized light is generated in the light source 22, so that the polarization beam splitter 23 and the light source 22
The number of reciprocations of light between the light source and the light source is reduced, and the light amount loss at the time of reflection and the light amount loss due to optical axis shift can be reduced.

Although not shown, the hemispherical reflecting element 27
A prism having a radial pattern may be provided on the inner surface of the lens to rotate the linearly polarized light by 90 degrees.

(Others) In addition, as a planar reflecting element for reflecting light from the polarizing beam splitter and returning it to the polarizing beam splitter, a polarization direction and a crystal axis direction are aligned instead of a retroreflector in which prisms are arranged. Alternatively, a semiconductor crystal plate of Si or the like may be used. Even with such a plane reflection element,
The linearly polarized light reflected or transmitted by the polarization beam splitter can be returned to the polarization beam splitter in a straight line without rotating the polarization direction. Therefore, even with such a planar reflection element, no loss is caused by the polarization beam splitter.

(Application Field) The polarization conversion element of the present invention can be used in various fields. For example, the present invention can be applied to a light source of a projector, a light source (light emitting unit) of a regression reflection photoelectric sensor, a light source of a surface inspection device using polarized light, a glossiness measuring device, and other measuring devices using polarized light. As an example, in the regression reflection type photoelectric sensor, the polarization conversion optical element of the present invention may be placed in the light projecting unit, and the light reflected by the regression reflection plate may be received by the light receiving unit through the polarization plate.

[Brief description of the drawings]

1A is a schematic diagram showing a front projection type projection television, and FIG. 1B is a schematic diagram showing a rear projection type projection television.

FIG. 2 is a diagram illustrating a configuration of a liquid crystal projector.

FIG. 3 is a perspective view showing a structure of a conventional polarization conversion optical element.

FIG. 4 is a perspective view showing the structure of a polarization conversion device according to an embodiment of the present invention.

FIG. 5 is a schematic plan view of the polarization conversion device.

FIGS. 6 (a), (b) and (c) are views for explaining the operation of the polarization converter of the above.

FIG. 7 is a perspective view of a retroreflective plate used in the polarization converter of the above.

FIG. 8 is an enlarged cross-sectional view for explaining the function of the above-described retroreflective plate.

FIG. 9 is a diagram illustrating an operation when linearly polarized light having a polarization direction parallel to the longitudinal direction of the prism is incident on the retroreflective plate.

FIG. 10 is a diagram showing an operation when linearly polarized light having a polarization direction orthogonal to the longitudinal direction of the prism is incident on the retroreflective plate.

FIG. 11 is a diagram illustrating an operation when linearly polarized light having a polarization direction that forms an angle of 45 degrees with the longitudinal direction of the prism is incident on the retroreflector according to the first embodiment.

FIG. 12 is a diagram showing a converging angle of light incident on the polarizing beam splitter according to the first embodiment.

FIG. 13 is a plan view showing a polarization filter element in which a retroreflector and a polarization beam splitter are integrated.

FIG. 14 is a plan view showing another polarization filter element in which a regression reflection plate and a polarization beam splitter are integrated.

FIG. 15 is a schematic plan view showing the structure of a polarization conversion device according to another embodiment of the present invention.

FIG. 16 is a sectional view showing a configuration of a light source according to still another embodiment of the present invention.

FIG. 17 is a front view of a hemispherical reflecting element of the light source.

FIG. 18 is an explanatory diagram of the operation of the above hemispherical reflecting element.

FIG. 19 is a cross-sectional view showing the configuration and operation of a light source according to still another embodiment of the present invention.

FIG. 20 is a sectional view showing a configuration of a light source according to still another embodiment of the present invention.

FIG. 21 is a front view of a curved reflecting element of the light source of the above.

[Explanation of symbols]

 REFERENCE SIGNS LIST 22 light source 23 polarizing beam splitter 24 retroreflector 25 light emitter 26 curved reflecting element 27 hemispherical reflecting element

Claims (4)

[Claims] 1. A light source having a function of generating light, converting incident linearly polarized light into non-linearly polarized light or linearly polarized light having a different polarization direction and reflecting the light, and two linearly polarized lights having different polarization directions from the light from the light source. 1. A polarization conversion device comprising: a polarization separation unit that separates one linearly polarized light and emits one of the linearly polarized light to the outside; and a polarization recovery unit that guides the other linearly polarized light separated by the polarization separation unit to the light source. 2. The light source according to claim 1, wherein the light source includes a luminous body and a reflecting element having a function of rotating the polarization direction of the linearly polarized light incident on the light source by approximately 90 degrees to emit the light from the light source. 3. The polarization conversion device according to item 1. 3. The polarization separation means comprises a polarization beam splitter, and the polarization recovery means comprises light reflection means provided on a side of the polarization beam splitter,
2. The polarization conversion device according to claim 1, wherein the light source and the light reflection unit have a conjugate positional relationship with each other. 4. A retroreflector is disposed on one surface of the polarizing beam splitter so as to separate light incident on the polarizing beam splitter into two linearly polarized lights having different polarization directions by the polarizing beam splitter. A polarization filter, which is emitted from the splitter, guides the other linearly polarized light to the regression reflection plate, and returns the linearly polarized light reflected by the regression reflection plate to the polarization beam splitter and reverses toward the first incident direction. element.