JP2004061619A - Polarized light changing device and illumination optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarized light changing device having a simple constitution where light to be given is made linearly polarized light whose polarization direction is made uniform. <P>SOLUTION: A polarized light selecting element (14) and a reflector (15) transmitting either of two polarized light components whose polarization directions are orthogonal and reflecting the other are arranged oppositely, and a 1/4 wavelength plate (16) is arranged between both of them. A light guiding element (12) which has reflection structure (12a) on either surface out of two opposed surfaces and reflects the light to be given by the reflection structure and emits it from either surface while totally reflecting it by two surfaces and making it advance inside is arranged between the polarized light selecting element or the reflector and the 1/4 wavelength plate, so that light from a light source (11) is made incident from the end face of the light guiding element. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polarization conversion device that converts substantially all light from a light source into linearly polarized light having a uniform polarization direction, and an illumination optical system including the same.
[0002]
[Prior art]
With the spread of mobile phones, personal digital assistants, notebook personal computers, and the like, a thin image display device is desired. As a display element that satisfies this, a liquid crystal display device that modulates illumination light to emit light representing an image. Is often used. Liquid crystal displays are roughly classified into a transmission type, which modulates while transmitting illumination light, and a reflection type, which modulates while reflecting illumination light. A backlight illumination optical system is used for illumination of the transmission type liquid crystal display, and a front light illumination optical system is used for illumination of the reflection type liquid crystal display.
[0003]
Each illumination optical system has a light source that emits illumination light and a planar light guide element that emits the light from the light source little by little from the surface on the liquid crystal display side while traveling inside, in order to uniformly illuminate a wide range. In general, it consists of The planar light guide element has a prism-shaped convex portion or a groove-shaped concave portion which is repeatedly provided on one surface, and while the light travels in the direction of repetition of the convex portion or the concave portion by total internal reflection, the convex portion or the concave portion. The light is reflected by a part of the surface of the concave portion, and the light is emitted with a largely changed course.
[0004]
Although a rod-shaped cold cathode tube has been used as a light source, a light emitting diode is used in combination with a linear light guide element for reducing power consumption and weight. The linear light guide element is configured in the same manner as the planar light guide element, is arranged to face the end face of the planar light guide element, and supplies light from the light source to the planar light guide element.
[0005]
In both the planar light guide element and the linear light guide element, the surface of the convex portion or concave portion that generates the outgoing light needs to be set so that the incident angle of light becomes small in order to largely change the course of light. There is. For this reason, although light can be reflected in a predetermined direction, some light is transmitted. This transmitted light reaches 10 to 20%, which causes a decrease in light use efficiency.
[0006]
It has been proposed to provide a reflecting member in order to make the light transmitted through the surface of the light guide element re-enter the light guide element. FIG. 24 shows an example of a liquid crystal display device having such an illumination optical system. This liquid crystal display device includes an illumination optical system including a light source 91 that emits illumination light, a linear light guide element 92, a planar light guide element 93, and a reflector 94 in order to illuminate a reflective liquid crystal display 95. Prepare. As the light source 91, a light emitting diode is used.
[0007]
The linear light guide element 92 has a plurality of concave portions 92a having a V-shaped cross section on one of two opposing surfaces. The light source 91 is arranged to face the end face of the light guide element 92, and the light guide element 92 is arranged so that the surface on which the concave portion 92 a is not formed faces the end face of the planar light guide element 93. I have. The planar light guide element 93 has a plurality of prism-shaped convex portions 93a on one surface, and is arranged such that the surface on which the convex portions 93a are not provided faces the liquid crystal display 95. .
[0008]
The linear light guide element 92 reflects the light from the light source 91 incident from the end face through the surface of the concave portion 92a while advancing inside by total reflection, and largely changes the traveling direction. Light is emitted partly from the facing surface. That is, the light source 91 and the linear light guide element 92 form a linear light source. The planar light guide element 93 reflects the light from the linear light guide element 92 incident from the end face through the surface of the convex portion 93a while advancing inside by total reflection, and largely changes the traveling direction. The light is emitted one by one from the surface facing the container 95.
[0009]
The concave portion 92a of the linear light guide element 92 and the convex portion 93a of the planar light guide element 93 are designed so that the light quantity distribution of the emitted light is as uniform as possible. The entire liquid crystal display 95 is substantially uniform. Is illuminated. The liquid crystal display 95 displays an image on the liquid crystal layer, and reflects the applied illumination light while modulating the displayed image to make light representing the image. The reflection type liquid crystal display 95 has a polarizing plate 95a, and guides only a polarized light component transmitted through the polarizing plate 95a, that is, only linearly polarized light having a uniform polarization direction, to the liquid crystal layer. The modulation is performed by rotating the target 90 °. Of the light reflected by the liquid crystal display 95. The linearly polarized light whose polarization direction is rotated by 90 ° is blocked by the polarizing plate 95a, and the linearly polarized light whose polarization direction has not changed becomes light representing an image. Light representing an image passes through the planar light guide element 93 and reaches the eye E of the observer.
[0010]
The reflector 94 causes the light that is transmitted through the surface of the linear light guide element 92 and is lost to re-enter the linear light guide element 92. The cross section of the reflector 94 is set in a U-shape so as to cover three surfaces except the surface facing the planar light guide element 93.
[0011]
In the planar light guide element 93 as well, there is light that passes through the surface of the convex portion 93a that generates emitted light. However, since it is necessary to guide image light from the reflective liquid crystal display 95 to the viewer, the planar light A reflecting member cannot be provided facing the light guide element 93. However, when the liquid crystal display is of a transmissive type, the surface of the planar light guide element 93 on which the convex portion 93a is not provided is arranged toward the rear surface of the liquid crystal display, and the convex portion 93a is provided. It has been practiced to provide a flat reflecting member facing the surface. In addition, the transmission type liquid crystal display device has polarizing plates on the front and rear surfaces, and according to the directions of the polarizing plates, the linearly polarized light whose polarization direction is rotated by 90 ° or the polarization direction is rotated by modulation in the liquid crystal layer. The linearly polarized light that is not used is light representing an image.
[0012]
[Problems to be solved by the invention]
As described above, the conventional liquid crystal display device is provided with the reflector to prevent the loss of light from the light source. However, the light emitted from the light source is non-polarized light whose polarization direction is disordered, and one half of the light is a polarized light component absorbed by the polarizing plate on the incident side of the liquid crystal display. For this reason, even if a reflector is provided, the light that can be effectively used for providing an image is less than half of the light emitted from the light source. Therefore, the effect of providing the reflector is limited.
[0013]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a polarization conversion device having a simple configuration that converts given light into linearly polarized light having a uniform polarization direction. It is an object of the present invention to provide a polarization conversion device in a form suitable for the illumination of the above.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a polarization conversion device that converts given light into linearly polarized light having a uniform polarization direction has a reflecting structure on one of two opposing surfaces, and converts given light into two polarized lights. A light guide element that is totally reflected by a surface and travels through the interior while being reflected by a reflection structure and emitted from one surface, and a polarization selection that transmits one of two polarization components whose polarization directions are orthogonal and reflects the other. An element and a reflecting element having at least one set of two reflecting surfaces orthogonal to each other, wherein the polarization selecting element faces the surface of the light guiding element from which light is emitted, and the reflecting element has the light guiding element interposed therebetween to select the polarization. The intersection of the reflection surface of the reflection element and the intersection of the reflection surface of the reflection element forms an angle of 45 ° with the polarization direction of the polarization component reflected by the polarization selection element.
[0015]
This polarization conversion device emits a given light partly toward a polarization selection element while traveling inside the light guide element. The polarization selection element transmits a polarization component in a predetermined polarization direction and reflects a polarization component in a polarization direction perpendicular to that direction. The light reflected by the polarization selection element is transmitted through the light guide element, enters the reflection element, and is sequentially reflected by two reflection surfaces orthogonal to each other of the reflection element. Here, the line of intersection of the reflection surface of the reflection element and the polarization direction of the polarization component reflected by the polarization selection element forms an angle of 45 °, and the polarization direction of light is rotated 90 ° by two reflections. Thus, the light reflected by the reflection element becomes a polarization component transmitted through the polarization selection element. This light passes through the light guide element, re-enters the polarization selection element, and passes through it. Therefore, all the light once incident on the polarization selection element is transmitted through the polarization selection element and becomes linearly polarized light having a uniform polarization direction.
[0016]
The reflection element also functions as a reflector that re-enters light directly emitted from the reflection element side surface of the light guide element to the reflection element. This light also enters the polarization selection element and is directly transmitted therethrough, or is reflected once, and is transmitted through the polarization selection element by the reflection element. Therefore, all of the applied light passes through the polarization selection element and becomes linearly polarized light having a uniform polarization direction.
[0017]
The reflecting element may have at least two reflecting surfaces orthogonal to each other, and may have a plurality of sets of two orthogonal reflecting surfaces. Further, the direction of the line of intersection of the reflection surface of the reflection element and the polarization direction of the polarization component reflected by the polarization selection element are irrelevant to the traveling direction of light inside the light guide element, and these may be set independently. it can.
[0018]
In order to achieve the above object, the present invention also provides a polarization conversion device that converts given light into linearly polarized light having a uniform polarization direction, a reflective element having an opening through which the given light passes through a part of a reflection surface, A polarization selection element that transmits one of two polarization components whose polarization directions are orthogonal to each other and reflects the other, and a quarter-wave plate, wherein the reflection element is positioned with the quarter-wave plate therebetween. To the configuration.
[0019]
In this polarization conversion device, light provided through the opening of the reflection element is transmitted through the quarter-wave plate and is incident on the polarization selection element, and is partially transmitted and partially reflected. If the light to be given is divergent light, most of the light reflected by the polarization selection element is reflected by the reflection element and reenters the polarization selection element. In the meantime, the light passes through the quarter-wave plate two more times, and the polarization direction is rotated by 90 °. Therefore, all of the applied light passes through the polarization selection element and becomes linearly polarized light having a uniform polarization direction.
[0020]
According to the present invention, a polarization conversion device that converts given light into linearly polarized light having a uniform polarization direction has at least one set of two reflecting surfaces that are orthogonal to each other, and an opening that allows the given light to pass through is a part of the reflecting surface. And a polarization selection element that transmits one of two polarization components whose polarization directions are orthogonal to each other and reflects the other. The reflection element faces the polarization selection element, and the intersection line of the reflection surface of the reflection element is provided. Has an angle of 45 ° with respect to the polarization direction of the polarization component reflected by the polarization selection element.
[0021]
In this polarization conversion device, light provided through the opening of the reflection element is incident on the polarization selection element, and is partially transmitted and partially reflected. If the light to be given is divergent light, most of the light reflected by the polarization selection element is reflected by the reflection element and reenters the polarization selection element. The light incident on the reflective element is sequentially reflected by two orthogonal reflecting surfaces whose intersection lines form 45 ° with respect to the polarization direction, and the polarization direction is rotated by 90 °. Therefore, all of the applied light passes through the polarization selection element and becomes linearly polarized light having a uniform polarization direction.
[0022]
In the configuration in which the reflective element has an opening, a reflective structure is provided on one of the two opposing surfaces, and while the applied light is totally reflected by the two surfaces and travels inside, the reflected light is reflected by the reflective structure and the one surface is reflected. It is preferable to provide a light guide element for emitting light more, and to make the end face of the light guide element face the polarization selection element. By doing so, the device that can provide linearly polarized light with a uniform polarization direction is provided, while the configuration after the light guide element is simple.
[0023]
Each of the above-described polarization conversion devices can be included in a part of an illumination optical system that illuminates a liquid crystal display.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the overall configuration of an illumination optical system 1 according to the first embodiment, and FIG. 2 shows a portion related to polarization conversion. The illumination optical system 1 includes a light source 11, a linear light guide element 12, a planar light guide element 13, a polarization selection element 14, a reflector 15, and a quarter-wave plate 16.
[0025]
The light source 11 is, for example, a light emitting diode, and is arranged to face the end face of the linear light guide element 12. The linear light guide element 12 has a plurality of concave portions 12 a having a V-shaped cross section on one surface, and is arranged such that the surface on which the concave portions 12 a are not provided faces the end surface of the planar light guide element 13. ing. The planar light guide element 13 has a plurality of prism-shaped convex portions 13a on one surface. The illumination optical system 1 is used in a form in which the surface of the planar light guide element 13 on which the projection 13a is not provided faces an illumination target, for example, a liquid crystal display.
[0026]
Light emitted from the light source 11 enters the linear light guide element 12 from the end face. The linear light guide element 12 totally reflects light from the light source 11 entering the inside thereof on two surfaces facing each other and travels in the direction of repetition of the concave portion 12a, while reflecting on one surface of the concave portion 12a to greatly increase the light. The direction is changed, and the light is emitted from the surface facing the planar light guide element 13. This is shown in FIG. The surface of the concave portion 12a that generates the emitted light is inclined so that the light is emitted almost perpendicularly from the surface facing the planar light guide element 13.
[0027]
The planar light-guiding element 13 reflects the light from the linear light-guiding element 12 that has entered inside from the end face on the two opposing surfaces and travels in the direction of repetition of the convex part 13a. The light is reflected by one surface and changes its direction greatly, and is emitted from the surface facing the illumination target. Although not shown, the surface of the projection 13a that generates the emitted light is also inclined such that the light is emitted substantially perpendicularly from the surface facing the illumination target.
[0028]
FIG. 4 shows the optical characteristics of the polarization selection element 14. The polarization selection element 14 is an optical element having a characteristic of transmitting one of two polarization components whose polarization directions are orthogonal to each other and reflecting the other. Hereinafter, the polarized light component transmitted through the polarization selecting element 14 is called P-polarized light, and the polarized light component reflected by the polarization selecting element 14 is called S-polarized light. There are several types of polarization selection elements having such characteristics. Here, DBEF (trade name of Sumitomo 3M) which can vertically enter light in a thin film shape is used.
[0029]
FIG. 5 shows the polarization state of light in the illumination optical system 1. The polarization selection element 14 is disposed between the linear light guide element 12 and the planar light guide element 13. The reflector 15 has a uniformly flat reflecting surface, and the reflecting surface is disposed so as to face the polarization selecting element 14 with the linear light guide element 12 interposed therebetween. The 波長 wavelength plate 16 is disposed between the linear light guide element 12 and the polarization selection element 14.
[0030]
The light emitted from the light source 11 is non-polarized light, and includes P-polarized light transmitted through the polarization selection element 14 and S-polarized light reflected by the polarization selection element 14. The light reflected and emitted from the surface of the concave portion 12a of the linear light guide element 12 passes through the quarter-wave plate 16 and enters the polarization selection element. P-polarized light of the light incident on the polarization selection element 14 is transmitted and is incident on the planar light guide element 13.
[0031]
The S-polarized light of the light incident on the polarization selection element 14 is reflected and transmitted through the quarter-wave plate 16, and is shifted from the linearly-polarized light to the circularly-polarized light by a shift of 1/4. This light passes through the linear light guide element 12, is reflected by the reflector 15, passes through the linear light guide element 12, passes through the 1/4 phase plate 16 again, and is further shifted in phase by 1/4. It becomes linearly polarized light. This linearly polarized light is P-polarized light whose polarization direction is rotated by 90 ° from the polarization direction when reflected by the polarization selection element 14 and passes through the polarization selection element 14. This light passes through the polarization selection element 14 and enters the planar light guide element 13.
[0032]
Therefore, all the light incident on the polarization selection element 14 finally passes through the polarization selection element 14, and the light incident on the planar light guide element 13 is linearly polarized light having a uniform polarization direction. When illuminating the liquid crystal display, by setting the orientation of the polarization selection element 14 so that the linearly polarized light incident on the planar light guide element 13 passes through the polarizing plate of the liquid crystal display, all illumination light can be emitted. Modulation becomes possible.
[0033]
Some of the light traveling inside the linear light guide element 12 passes through the surface of the concave portion 12a that generates the emitted light. This light is reflected by the reflector 15, re-enters the linear light guide element 12, travels inside the linear light guide element 12 again, or transmits through the linear light guide element 12. The latter light passes through the 位相 phase plate 16 and enters the polarization selection element 14, and thereafter, all of the light finally passes through the polarization selection element 14 in exactly the same manner as described above.
[0034]
As shown in FIG. 2, the reflector 15 has a U-shaped cross section, and covers three surfaces of the linear light guide element 12 other than the surface facing the planar light guide element 13. When the degree of divergence of the light emitted from the light source 11 is large, some light is transmitted through three surfaces other than the surface facing the planar light guide element 13, but the reflector 15 converts the light into the linear light guide element 12. Again.
[0035]
The 波長 wavelength plate 16 may be arranged between the linear light guide element 12 and the reflector 15 instead of between the linear light guide element 12 and the polarization selection element 14. FIG. 6 shows a portion related to the polarization conversion of the modified example of the illumination optical system 1 in which the arrangement position of the 波長 wavelength plate 16 is set as described above. FIG. 7 shows the polarization state of light. Also in this configuration, the principle that the S-polarized light reflected by the polarization selection element 14 becomes P-polarized light by transmitting twice through the quarter-wave plate 16 is exactly the same.
[0036]
FIG. 8 shows a part related to the polarization conversion of the illumination optical system 2 of the second embodiment. The illumination optical system 2 is obtained by modifying the illumination optical system 1 described above, and includes a prism array 25 between the linear light guide element 12 and the reflector 15 and omits the 波長 wavelength plate 16.
[0037]
The prism array 25 is shown in FIG. The prism array 25 has a plurality of surfaces 25a whose inclination directions are alternately changed. The surface 25a is a reflection surface formed by vapor deposition of a metal such as aluminum or lamination of a dielectric. Hereinafter, the surface 25a of the prism array 25 is referred to as a reflection surface. Adjacent reflection surfaces 25a are orthogonal, and a cross section perpendicular to the intersection line forms a right-angled isosceles triangle. The intersections of the reflection surfaces 25a are perpendicular to the length direction of the linear light guide element 12, and are all parallel to each other.
[0038]
The polarization selection element 14 is oriented so that the polarization direction of the reflected S-polarized light forms an angle of 45 ° with the intersection line of the reflection surface 25a of the prism array 25. The light reflected by the polarization selection element 14 is transmitted through the linear light guide element 12, enters the prism array 25, and is sequentially reflected by two adjacent reflection surfaces 25a. FIG. 10 shows how light is reflected by the prism array 25, and FIG. 11 shows the polarization directions of light before and after reflection by the prism array 25. 9 and 11, Pin represents the polarization direction of the light before entering the prism array 25, and Pref represents the polarization direction of the light reflected by the prism array 25. The x and y directions in FIG. 11 correspond to the x and y directions in FIG.
[0039]
In the two reflections at the two reflection surfaces 25a, the polarization direction is rotated by 90 ° due to the relationship between the polarization direction of the light and the angle of the reflection surface 25, and the light reflected by the prism array 25 passes through the polarization selection element. P-polarized light is transmitted. This light passes through the linear light guide element 12 and also passes through the polarization selection element 14 to enter the planar light guide element 13. After all, similarly to the illumination optical system 1 of the first embodiment including the quarter-wave plate 16, all of the light incident on the polarization selection element 14 finally passes through the polarization selection element 14 and has the same polarization direction. Linearly polarized light.
[0040]
An illumination optical system 3 according to the third embodiment will be described. The illumination optical system 3 of the present embodiment is obtained by modifying the illumination optical system 2 described above and changing the direction of the reflection surface 25a of the prism array 25. FIG. 12 shows the prism array 25 of the illumination optical system 3.
[0041]
It is the same as the illumination optical system 2 that the reflection surface 25a of the prism array 25 is orthogonal and the cross section perpendicular to the intersection line forms an isosceles right triangle. The plane including every other intersection of the reflection surface 25a is parallel to the surface of the linear light guide element 12 provided with the concave portion 12a, but the intersection of the reflection surface 25a is the length of the linear light guide element 12. At an angle of 45 ° to the direction.
[0042]
Similarly to the illumination optical system 2, the polarization selection element 14 is oriented such that the polarization direction of the reflected S-polarized light forms an angle of 45 ° with the intersection of the reflection surface 25 a of the prism array 25. . However, since the illumination optical system 3 and the illumination optical system 2 have a difference of 45 ° in the direction of the intersection of the reflection surface 25a, there is also a difference of 45 ° in the direction of the polarization selection element 14.
[0043]
The light reflected by the polarization selection element 14 is transmitted through the linear light guide element 12, enters the prism array 25, and is sequentially reflected by two adjacent reflection surfaces 25a. FIG. 13 shows how light is reflected by the prism array 25, and FIG. 14 shows the polarization directions of light before and after reflection by the prism array 25.
[0044]
In the illumination optical system 3 as well, the prism array 25 rotates the polarization direction of the light reflected by the polarization selection element 14 by 90 ° so that the reflected light passes through the polarization selection element 14. Eventually, all the light that has entered the polarization selection element 14 finally passes through the polarization selection element 14 and becomes linearly polarized light having a uniform polarization direction.
[0045]
An illumination optical system 4 according to the fourth embodiment will be described. The illumination optical system 4 of the present embodiment is a modification of the illumination optical systems 2 and 3 and includes a prism 35 having two reflecting surfaces 35a instead of the prism array 25. The prism 35 is shown in FIG. The two reflecting surfaces 35a are orthogonal to each other, and a cross section perpendicular to the intersection line forms a right-angled isosceles triangle. In addition, the line of intersection of the reflection surface 35 a is parallel to the length direction of the linear light guide element 12.
[0046]
As described above, the polarization selection element 14 is oriented such that the polarization direction of the reflected S-polarized light forms an angle of 45 ° with the intersection of the reflection surface 35a of the prism 35. As described above, even in a configuration having only two orthogonal reflecting surfaces 35a, all the light incident on the polarization selection element 14 is finally transmitted through the polarization selection element 14 to be linearly polarized light having a uniform polarization direction. Can be.
[0047]
Rotating the polarization direction by 90 ° by the orthogonal reflecting surfaces 25a and 35a is also possible by omitting the prism array 25 and the prism 35 and providing such a reflecting surface on the reflector 15. FIG. 16 shows a reflector 15 of the illumination optical system 5 according to the fifth embodiment, which is one example. The portion of the reflector 15 facing the surface of the linear light guide element 12 where the concave portion 12a is provided is provided with a reflection surface 15a similar to the reflection surface 25a of the third embodiment.
[0048]
FIG. 17 shows the overall configuration of an illumination optical system 6 according to the sixth embodiment. The illumination optical system 6 includes a light source 11, a linear light guide element 12, and a planar light guide element 13, which are configured in the same manner as in the first embodiment. FIG. 18 shows a part of the illumination optical system 6 relating to polarization conversion. The polarization selecting element 14, the quarter-wave plate 16, and the reflector 15 located between the linear light guide element 12 and the planar light guide element 13 are omitted, and instead, the light source 11 and the linear light guide A polarization selection element 44, a reflection plate 45, and a quarter wavelength plate 46 are provided between the optical element 12 and the optical element 12.
[0049]
The reflection plate 45 is obtained by forming a reflection film 45a on the surface of a transparent substrate 45b by vapor deposition of metal or lamination of a dielectric, and has an opening 45c at the center of the reflection film 45a. The 波長 wavelength plate 46 is in contact with the substrate 45b of the reflection plate 45, and the polarization selection element 44 is in contact with the 波長 wavelength plate 46. Further, the light source 11 is arranged to face the opening 45 c of the reflection plate 45.
[0050]
The light emitted from the light source 11 passes through the opening 45c, passes through the quarter-wave plate 46, and enters the polarization selection element 44. Of the light incident on the polarization selection element 44, P-polarized light is transmitted therethrough, and S-polarized light is reflected. The light emitted from the light source 11 is divergent light, and the light reflected by the polarization selection element 44 passes through the quarter-wave plate 46, and most of the light enters the reflection film 45 a of the reflection plate 45. The light that has entered the reflection film 45a is reflected, passes through the quarter-wave plate 46, and enters the polarization selection element 44 again. This light is transmitted through the quarter-wave plate 46 twice, so that the polarization direction is rotated by 90 ° to be P-polarized light, and transmitted through the polarization selection element 44.
[0051]
In the illumination optical system 6 of the present embodiment, all the light from the light source 11 enters the linear light guide element 12 as linearly polarized light having a uniform polarization direction. The polarization selection element 44, the reflection plate 45, and the quarter-wave plate 46 are smaller than those in the above embodiments, and together with the light source 11, a point-like light source that supplies linearly polarized light with a uniform polarization direction is used. Make.
[0052]
FIG. 19 shows a part related to polarization conversion of the illumination optical system 7 of the seventh embodiment. The illumination optical system 7 of the present embodiment includes the prism array 55 by modifying the illumination optical system 6 described above, omitting the reflection plate 45 and the quarter-wave plate 46. The prism array 55 is in contact with the polarization selection element 44, has a plurality of reflection surfaces 55a orthogonal to each other on the surface opposite to the polarization selection element 44, and has an opening 55c at the center of the surface. The reflecting surface 55a of the prism array 55 has the same setting as that of the second and third embodiments, and the angle of the polarization direction of the reflected light from the polarization selecting element 44 with respect to the intersection of the reflecting surface 55a is also the same as that described above. 45 °.
[0053]
The light emitted from the light source 11 passes through the opening 55c, enters the polarization selection element 44, partially transmits, and the remaining part is reflected. Most of the light reflected by the polarization selection element 44 is incident on the reflection surface 55a of the prism array 55 and is reflected twice, so that the polarization direction is rotated by 90 ° and becomes light transmitted through the polarization selection element 44. In the illumination optical system 7 as well, all the light from the light source 11 enters the linear light guide element 12 as linearly polarized light having a uniform polarization direction, and the polarization selection element 44 and the prism array 55 A point-like light source that supplies linearly polarized light with uniformity.
[0054]
The polarization selection element 44, the reflection plate 45, and the quarter-wave plate 46 of the sixth embodiment can be linearly arranged by arranging them one-dimensionally, and can be arranged two-dimensionally. Thus, a planar illumination optical system can be obtained. The same applies to the polarization selection element 44 and the prism array 55 of the seventh embodiment.
[0055]
Hereinafter, an illumination optical system 8 according to an eighth embodiment equivalent to a configuration in which the polarization selection element 44, the reflection plate 45, and the quarter-wave plate 46 are arranged two-dimensionally will be described. FIG. 20 shows a part of the illumination optical system 8 relating to polarization conversion. The illumination optical system 8 includes a polarization selection element 74, a reflection plate 75, a quarter-wave plate 76, a first lens array 77, and a second lens array 78. The reflector 75 and the first and second lens arrays 77 and 78 are shown in FIGS. 21 and 22, respectively. The reflection plate 75 has openings 75c arranged two-dimensionally, and the lens arrays 77, 78 have lens cells 77a, 78a arranged two-dimensionally corresponding to the openings 75c of the reflection plate 75.
[0056]
FIG. 23 shows a portion from one lens cell 77a to a corresponding lens cell 78a and light passing through that portion. Substantially parallel light is applied to the lens array 77, and each lens cell 77a converges the incident light to the corresponding opening 75c. The light that has passed through the opening 75c becomes divergent light, passes through the quarter-wave plate 76, and enters the polarization selection element 74. P-polarized light of the light incident on the polarization selection element 74 is transmitted, and S-polarized light is reflected. The S-polarized light reflected by the polarization selection element 74 passes through the quarter-wave plate 76 to become circularly polarized light, is reflected by the reflection plate 75, transmits again through the quarter-wave plate 76, and passes through the polarization selection element 74. P-polarized light is transmitted. The light transmitted through the polarization selection element 74 is incident on the lens array 78, is made closer to parallel light by each lens cell 78a, and is guided to the illumination target.
[0057]
Each lens cell 78a of the second lens array 78 also guides light to a surface portion of the illumination object facing a portion surrounded by the four lens cells 78a and having no light to transmit, so that the entire illumination object is The characteristics are set slightly different from those of the lens cell 77a of the first lens array 77 in order to provide substantially uniform illumination. The illumination optical system 8 can be used for illumination of a transmissive liquid crystal display, and is slightly larger, so that it is suitable for a projector using a transmissive liquid crystal display.
[0058]
【The invention's effect】
A light-guiding element having a reflecting structure on one of the two opposing surfaces, wherein the light is reflected by the reflecting structure and emitted from one of the surfaces while the given light is totally reflected on the two surfaces and travels inside; A polarization selection element that transmits one of the two polarization components whose directions are orthogonal to each other and reflects the other; and a reflection element having at least one pair of two reflection surfaces that are orthogonal to each other, wherein the polarization selection element is a light guide element. The reflection element faces the polarization selection element with the light guide element interposed therebetween, and the intersection of the reflection surface of the reflection element with respect to the polarization direction of the polarization component reflected by the polarization selection element. , 45 °, the polarized light conversion device of the present invention has a simple configuration, but can convert all the applied light into linearly polarized light having a uniform polarization direction. The reflection element also functions as a reflector that re-enters light emitted from the reflection element side of the light guide element to the light guide element, and eliminates lost light. By reducing the width of the light guide element, the polarization selection element, and the reflection element, a linear illumination optical system that performs polarization conversion is obtained.
[0059]
A reflecting element having an opening for transmitting given light in a part of the reflecting surface, a polarization selecting element for transmitting one of two polarization components whose polarization directions are orthogonal to each other and reflecting the other, and a 波長 wavelength plate. The polarization conversion device of the present invention in which the reflection element is disposed so as to oppose the polarization selection element with the quarter-wave plate therebetween, also has a simple configuration, but all the applied lights have the same polarization direction. It can be linearly polarized light. This polarization conversion device can be used alone as a point-like illumination optical system that performs polarization conversion, or when combined, can be used as a linear or planar illumination optical system that performs polarization conversion.
[0060]
A reflective element having at least one pair of two mutually orthogonal reflecting surfaces, and having an opening in a part of the reflecting surface for transmitting given light, and transmitting one of two polarized components having orthogonally polarized light directions and transmitting the other. A polarization selecting element that reflects the light, wherein the reflecting element faces the polarization selecting element, and the line of intersection of the reflection surface of the reflecting element forms an angle of 45 ° with the polarization direction of the polarization component reflected by the polarization selecting element. The polarization conversion device according to the present invention, which is formed, has a simple configuration, but can convert all the applied light into linearly polarized light having a uniform polarization direction. When used alone, it can be used as a point-like illumination optical system that performs polarization conversion, and when a plurality is combined, it can be used as a linear or planar illumination optical system that performs polarization conversion.
[0061]
In a configuration in which the reflective element has an opening, a reflective structure is provided on one of the two opposing surfaces, and while the applied light is totally reflected on the two surfaces and travels inside, one surface is reflected by the reflective structure. When a light guide element for emitting light is further provided, and the end face of the light guide element is opposed to the polarization selection element, a linear shape capable of providing linearly polarized light having a uniform polarization direction while the configuration after the light guide element is simple. Illumination optical system.
[0062]
When any of the above-described polarization conversion devices is included in a part of the illumination optical system that illuminates the liquid crystal display, all of the applied light can be converted into linearly polarized light suitable for modulation of the liquid crystal display, and the use of light Efficiency is increased, and a bright image can be provided.
[Brief description of the drawings]
FIG. 1 is a plan view showing the overall configuration of an illumination optical system according to a first embodiment.
FIG. 2 is a perspective view showing a part related to polarization conversion of the illumination optical system according to the first embodiment.
FIG. 3 is a perspective view showing a linear light guide element of the illumination optical system according to the first embodiment and light emitted from the linear light guide element.
FIG. 4 is a diagram schematically showing characteristics of a polarization selection element.
FIG. 5 is a diagram illustrating a polarization state of light in the illumination optical system according to the first embodiment.
FIG. 6 is a perspective view showing a part related to polarization conversion of an illumination optical system according to a modification of the first embodiment.
FIG. 7 is a diagram illustrating a polarization state of light in an illumination optical system according to a modification of the first embodiment.
FIG. 8 is a perspective view showing a part related to polarization conversion of the illumination optical system according to the second embodiment.
FIG. 9 is a perspective view showing a prism array of the illumination optical system according to the second embodiment.
FIG. 10 is a diagram showing how light is reflected by a prism array of the illumination optical system according to the second embodiment.
FIG. 11 is a diagram illustrating polarization directions of light before and after reflection by a prism array of the illumination optical system according to the second embodiment.
FIG. 12 is a perspective view showing a prism array of the illumination optical system according to the third embodiment.
FIG. 13 is a view showing a state of light reflection by a prism array of the illumination optical system according to the third embodiment.
FIG. 14 is a diagram illustrating polarization directions of light before and after reflection by a prism array of the illumination optical system according to the third embodiment.
FIG. 15 is a perspective view showing a prism of an illumination optical system according to a fourth embodiment.
FIG. 16 is a perspective view showing a reflector of the illumination optical system according to the fifth embodiment.
FIG. 17 is a plan view showing the overall configuration of an illumination optical system according to a sixth embodiment.
FIG. 18 is a plan view showing a part related to polarization conversion of the illumination optical system according to the sixth embodiment.
FIG. 19 is a plan view showing a part related to polarization conversion of the illumination optical system according to the seventh embodiment.
FIG. 20 is a plan view showing a part related to polarization conversion of the illumination optical system according to the eighth embodiment.
FIG. 21 is a front view showing a reflector of an illumination optical system according to an eighth embodiment.
FIG. 22 is a front view showing a lens array of the illumination optical system according to the eighth embodiment.
FIG. 23 is a plan view showing a state of light in the illumination optical system according to the eighth embodiment.
FIG. 24 is a perspective view showing a conventional liquid crystal display device.
[Explanation of symbols]
1-8 Illumination optical system
11 Light source
12 Linear light guide element
12a recess
13 Planar light guide element
13a convex
14 Polarization selector
15 Reflector
15a Reflective surface
16 quarter wave plate
25 Prism array
25a reflective surface
35 Prism
35a reflective surface
44 Polarization Selector
45 Reflector
45a reflective film
45b substrate
45c opening
46 1/4 wavelength plate
55 prism array
55a reflective surface
55c opening
74 polarization selector
75 Reflector
76 quarter wave plate
77 lens array
77a lens cell
78 lens array
78a lens cell

Claims (5)

A polarization conversion device that converts the given light into linearly polarized light having a uniform polarization direction,
A light-guiding element having a reflecting structure on one of the two opposing surfaces, reflecting the given light totally on the two surfaces and traveling inside, while reflecting the light by the reflecting structure and emitting the light from one surface;
A polarization selection element that transmits one of two polarization components whose polarization directions are orthogonal to each other and reflects the other,
A reflective element having at least one pair of two reflective surfaces orthogonal to each other,
The polarization selection element faces the surface of the light guide element that emits light, the reflection element faces the polarization selection element with the light guide element in between,
A polarization converter, wherein an intersection line of a reflection surface of a reflection element forms an angle of 45 ° with a polarization direction of a polarization component reflected by the polarization selection element. A polarization conversion device that converts the given light into linearly polarized light having a uniform polarization direction,
A reflective element having an opening for transmitting given light on a part of the reflective surface,
A polarization selection element that transmits one of two polarization components whose polarization directions are orthogonal to each other and reflects the other,
A quarter-wave plate,
A polarization conversion device, wherein the reflection element faces the polarization selection element with a quarter-wave plate therebetween. A polarization conversion device that converts the given light into linearly polarized light having a uniform polarization direction,
A reflecting element having at least one pair of two reflecting surfaces orthogonal to each other, and having an opening in a part of the reflecting surface for transmitting given light;
A polarization selection element that transmits one of the two polarization components whose polarization directions are orthogonal and reflects the other.
The reflection element faces the polarization selection element,
A polarization converter, wherein an intersection line of a reflection surface of a reflection element forms an angle of 45 ° with a polarization direction of a polarization component reflected by the polarization selection element. A light-guiding element having a reflecting structure on one of the two opposing surfaces and reflecting the given light totally on the two surfaces and traveling inside, while being reflected by the reflecting structure and emitting from one surface;
4. The polarization converter according to claim 2, wherein an end face of the light guide element faces the polarization selection element. An illumination optical system for illuminating the liquid crystal display,
An illumination optical system comprising the polarization conversion device according to any one of claims 1 to 4.

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