JP2009258656A - Light pipe, illuminating optical system, and image projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To emit an illuminating light having high directivity of light and an uniformized luminance distribution so as to improve the utilization efficiency of the light, in a light pipe 1 configured so that the light from a light source is made incident through an incidence end 5, repeatedly reflected by a sidewall surface 3 and is then emitted from an injection end 6. <P>SOLUTION: A light guide 2 includes a translucent partition part 12 for partitioning the internal space of the light guide 2 in the longitudinal direction of the light guide 2, and a refraction part 4, formed on a surface of the incident end 5-side region of the partition part 12. The emission angle β of the light emitted through an emitting end 6 is set smaller than the incident angle α of the light introduced through the incident end 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light pipe that introduces light from one end and emits the light from the other end, and an illumination optical system and an image projection apparatus using the light pipe.

  2. Description of the Related Art Image projection apparatuses that irradiate light modulation elements such as liquid crystal display elements and DMD (digital micromirror device) elements with light from a light source and project an image on a screen have become widespread. A halogen lamp, a high pressure mercury lamp, or the like has been used as a light source for irradiating the light modulation element. However, these light sources require a large amount of electric power, and since a temperature rises and requires a cooling device, the weight and volume increase, which hinders the compact construction of the entire device. On the other hand, in recent years, the luminance and light emission efficiency of light emitting diodes (LEDs) have been improved. Since the LED has a low driving voltage and is small and lightweight, if the LED can be used as a light source of an image projection apparatus, the entire apparatus can be reduced in size and weight.

  However, the light emitted from the LED has low directivity, and a reflector or a condenser lens system is required, and the luminance in the direction in which the light is emitted is not necessarily uniform. If the directivity of the emitted light is low, the proportion of light that can be used for image projection decreases, and the projection surface becomes dark. In addition, if there is luminance unevenness with respect to the emission direction, luminance unevenness occurs on the projection surface and image quality is degraded. Patent Document 1 is intended to improve such a problem by using a rod integrator (hereinafter referred to as a light pipe).

  FIG. 7 shows a cross-sectional structure of the illumination light source device 50 described in Patent Document 1. As shown in FIG. The illumination light source device 50 includes a light pipe 51 and a white LED 52 provided in a light incident opening 54 of the light pipe 51. The white LED 52 can set the light emitting point 53 inside the light guide path 56 from the end of the light pipe 51, and can efficiently guide the light emitted from the light emitting point 53 to the light exit opening 55. In addition, since the light pipe 51 has a hollow cylindrical shape, the number of times of internal reflection of light is increased as compared with the case where a solid columnar light pipe is used. Therefore, when light is emitted from the light emission opening 55, illumination light with a more uniform intensity can be obtained.

  FIG. 8 shows a cross-sectional structure of the illumination device 60 described in Patent Document 2. Mounted with a plurality of taper rods 63, a rod 64 that gathers the exit side openings of the plurality of taper rods 63, and LEDs 68R, 68G, 68B and LEDs installed at the bottom of each mortar-shaped taper rod 63 The LED array 62 is composed of the substrate 67. The light emitted from each LED 68R, 68G, 68B is reflected by the wall surface of the taper rod 63, the emission angle becomes narrow, and is emitted from the exit end of the rod 64. The light of each color emitted from the plurality of light sources of the LEDs 68R, 68G, and 68B is combined, and white light with higher directivity can be emitted.

JP-A-2005-283918 JP 2003-330109 A

  In the illumination light source device 50 described in Patent Document 1, for example, the emission angle of light emitted from the light emitting point 53 of the white LED 52 is θ. The light emitted from the light emitting point 53 is repeatedly reflected by the inner surface 57 of the light pipe 51 and proceeds to the light exit opening 55. However, when light is reflected by the inner surface 57, the incident angle and the reflection angle are equal. That is, when the light emitted from the white LED 52 is emitted from the light emission opening 55, the emission angle is maintained. Therefore, if the emission angle of light emitted from the light emission opening 55 is φ, the emission angle φ is almost the same as the emission angle θ. Therefore, in the illumination light source device 50 shown in FIG. 7, the directivity of the light emitted from the light pipe 51 is not so different from the directivity of the light emitted from the LED 52 as the light source. Therefore, additional devices are required to prevent the light utilization efficiency from being lowered. In particular, when used in a projector, since the allowable incident angle of the projection lens is smaller than the light emission angle of the LED, light emitted from the light pipe at an emission angle larger than the allowable incident angle is not projected from the projection lens and is lost. .

  In the illuminating device 60 described in Patent Document 2, the light emitted from the LEDs 68R, 68G, and 68B is emitted with high directivity by the tapered rod 63 having a reflector function. However, the light emitted from each LED 68R, 68G, 68B is not repeatedly reflected in each taper rod 63, and the rod 64 provided at the tip of the taper rod 63 has a large diameter, so that the light emitted from the taper rod 63 is repeatedly reflected. Less often. For example, when the light emitted from the LEDs 68R, 68G, and 68B has an emission angle dependency, the angle dependency of the emission light emitted from the rod 64 is maintained as it is and appears as uneven color in the projected image. Similarly, when the emission colors are different between the LEDs 68R, 68G, 68B, there is a possibility that a color distribution is generated in the light emitted from the rod 64. When the color distribution occurs, the quality of the projected image is deteriorated. Therefore, it is necessary to take measures such as further providing a light mixing means between the rod 64 and the light modulation element.

  In the present invention, the following means have been taken in order to solve the above problems.

  In the invention according to claim 1, the light pipe is formed of a cylindrical light guide whose side wall surface is a reflection surface, in which light is introduced from the incident end, repeatedly reflected by the side wall surface, and emitted from the emission end. The light guide includes a translucent partition portion that partitions at least an internal space on the incident end side of the light guide in the longitudinal direction of the light guide, and the incident end side of the partition portion. The light pipe is characterized in that a diffractive portion is formed on the surface of the region, and an exit angle of light emitted from the exit end is smaller than an incident angle of light introduced from the entrance end.

  In the invention according to claim 2, the partition portion has a cross shape so that two translucent plates are orthogonal to each other, and the internal space is divided into four parts. The light pipe according to claim 1, wherein the light pipe is formed on the surface of two translucent plates.

  The invention according to claim 3 is characterized in that the diffractive portion has a plurality of grooves, and an interval between the plurality of grooves becomes narrower as it approaches the incident end. The light pipe.

  In the invention according to claim 4, the diffractive portion has a plurality of grooves, and the intervals between the plurality of grooves are different from each other in the two translucent plates orthogonal to each other. Or it was set as the light pipe of Claim 3.

  In the invention which concerns on Claim 5, it was set as the illumination optical system provided with the light pipe of any one of Claims 1-4, and the light emitting element installed in the said incident end of the said light pipe.

  In the invention which concerns on Claim 6, the said incident end is divided | segmented by the said partition part, The said some light emitting element is installed corresponding to each of the said divided incident end, It is characterized by the above-mentioned. The illumination optical system according to claim 5 is provided.

  In the invention according to claim 7, the shape of the light emitting surface of the light emitting element is substantially the same as the shape surrounded by the side wall surface and the partition portion at the incident end. The illumination optical system according to claim 6 is provided.

  In the invention which concerns on Claim 8, the said incident end is divided into 4 by the said partition part, The light emitting element of each luminescent color of red, green, blue, and white is installed in the said 4 divided incident ends. An illumination optical system according to claim 6 or claim 7 is provided.

  In the invention which concerns on Claim 9, the said incident end is divided into 4 by the said partition part, The light emitting element of each luminescent color of red, green, green, and blue is installed in the said 4 divided incident ends. An illumination optical system according to claim 6 or claim 7 is provided.

  In the invention which concerns on Claim 10, the illumination optical system described in any one of the said Claims 5-9, the light modulation part which converts the illumination light inject | emitted from the said illumination optical system into image light, The image projection apparatus includes a projection unit that projects the image light.

  In the invention according to claim 11, the illumination optical system corresponds to each of the three primary colors, and a light combining unit that combines light emitted from each of the illumination optical systems, and light combined by the light combining unit The image projection apparatus according to claim 10, further comprising: the light modulation unit that modulates the light and the projection unit that projects the light modulated by the light modulation unit.

  The light pipe according to the present invention is such that light is introduced from the incident end, repeatedly reflected on the side wall surface, and emitted from the exit end. The light guide guides at least the internal space on the incident end side. A translucent partition that partitions in the longitudinal direction of the light body is configured, a diffractive portion is formed on the surface of the region on the incident end side of the partition, and the exit angle of light emitted from the exit end is from the entrance end. The incident angle of the light to be introduced was made smaller. Thereby, the directivity higher than the directivity of the incident light can be given, and the light with improved brightness uniformity at the exit end can be emitted, and as a result, the light utilization efficiency can be improved. Has the advantage.

  The partition has a cross-shaped cross section so that the two translucent plates are orthogonal to each other, and the internal space is divided into four parts. The diffractive portion is formed on the surface of the two translucent plates. Has been. As a result, even when light of different colors is incident on the internal space divided into four parts, the light of each color can be transmitted to and mixed with other regions, and light with high directivity can be emitted. Has advantages.

  Moreover, the diffraction part has a plurality of grooves, and the interval between the plurality of grooves is made narrower as it approaches the incident end. The light incident on the incident end region of the light pipe enters the diffraction section near the incident end as the emission angle from the light emitting element increases. The diffractive portion near the incident end is diffracted by receiving a stronger diffractive action because the groove interval is narrower than that of the diffractive portion on the exit end side. That is, as the light beam has a larger emission angle, it can be subjected to a large declination action that approximates to parallel light, and as a result, the directivity of the emitted light can be further increased.

  The diffractive portion has a plurality of grooves, and the intervals between the plurality of grooves are different from each other in the two translucent plates orthogonal to each other. As a result, for example, it is possible to individually set the vertical and horizontal light transmission conditions of the cross-shaped partition part, and light with improved directivity while giving different emission angles in the vertical and horizontal directions. Can be injected.

  Moreover, it was set as the illumination optical system provided with the said light pipe and the light emitting element installed in the incident end of this light pipe. Accordingly, there is an advantage that light is small and light, has high directivity, and has little luminance unevenness.

  The incident end is divided by the partition plate, and an illumination optical system is provided in which a plurality of light emitting elements are installed corresponding to the divided incident ends. This makes it possible to irradiate light with high directivity and high brightness if the light emitting elements of the same color are arranged, and additively mixed light with high directivity and less luminance unevenness if light emitting elements of different colors are installed. It has the advantage that it can.

  In addition, an illumination optical system in which the shape of the light emitting surface of the light emitting element is substantially the same as the shape of the incident end of the light pipe. This has the advantage that the area of the exit surface of the light pipe can be minimized and the utilization efficiency of light emitted from the light emitting element can be improved.

  In addition, the incident end is divided into four by the partition part, and the four divided incident ends are provided with light emitting elements of emission colors of red, green, green and blue, or red, green, blue and white. The illumination optical system was provided with light emitting elements of the respective emission colors. Accordingly, there is an advantage that light of all colors matching the visibility characteristics can be emitted, or light of all colors can be irradiated together with strong white light.

  The image projection apparatus includes the illumination optical system, a light modulation unit that converts illumination light emitted from the illumination optical system into image light, and a projection unit that projects the image light. Thereby, it has the advantage that a lightweight and small-sized image projector can be comprised.

It is a typical longitudinal section of a light pipe concerning an embodiment of the present invention. It is explanatory drawing of the light pipe which concerns on embodiment of this invention. It is a typical longitudinal section of a light pipe concerning an embodiment of the present invention. It is explanatory drawing of the illumination optical system which concerns on embodiment of this invention. 1 is a schematic cross-sectional view of an image projection apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view of an image projection apparatus according to an embodiment of the present invention. It is sectional drawing of the conventionally well-known illumination light source device. It is sectional drawing of a conventionally well-known illumination optical system.

Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional view showing a configuration of a light pipe 1 according to an embodiment of the present invention. The light pipe 1 is composed of a light guide 2 having a cylindrical shape. A translucent partition 12 is formed in the inner space of the light guide 2. The side wall surface 3 of the light guide 2 is constituted by a reflection surface that reflects light. The light guide 2 receives light from the incident end 5 and emits the incident light from the exit end 6. A diffractive portion 4 is formed on the upper surface of the partition portion 12 on the incident end 5 side. Light incident at an incident angle α is transmitted to the exit end 6 side in the diffraction section 4. In this diffractive portion 4, according to the transmission conditions of the diffractive portion 4, light of several orders among the light incident at the incident angle γ1 can be transmitted at the transmission angle γ2 having an angle larger than the incident angle γ1. . In the partition part 12 other than the diffraction part 4, the incident angle γ3 and the transmission angle γ4 are equal. Further, the incident angle and the reflection angle of the light incident on the side wall surface 3 of the light guide 2 are equal. Thereby, the emission angle β becomes smaller than the incident angle α. In the following description, the maximum angle of the light flux that enters with a spread is referred to as an incident angle α, and the maximum angle of the light flux that exits with a spread is referred to as an emission angle β.

  As the light guide 2, an inorganic material such as glass, a resin material such as plastic, a metal material, ceramics, or the like is used. On the side wall surface 3 of the light guide 2, for example, a metal film such as Ag or Al or a reflective film of a dielectric film is provided. The reflective film may be provided on the outer surface of the light guide 2, and part of the incident light incident on the light guide 2 is reflected by the inner surface, and the light transmitted through the inner surface is reflected by the reflective film on the outer surface. Reflected. The partition portion 12 provided inside the light guide 2 can use an inorganic material such as translucent glass or a resin material such as translucent plastic. The light guide 2 may have a cylindrical shape or a polygonal cylindrical shape. The partition part 12 may be one sheet or a large number of sheets. Further, the cross section may be a cross shape so that the two translucent plates are orthogonal to each other, or the cross section may be a * shape. In addition to the case where the partition portion 12 extends from the incident end 5 to the exit end 6, the partition portion 12 may not be extended from the entrance end 5 to the exit end 6 but may be formed halfway. In addition, the shape is set according to an apparatus that requires a uniform surface light source. For example, when irradiating light to a light modulation element whose display effective surface is a quadrangle, the cross section in the short direction of the light guide 2 is made a quadrangle. Thereby, the emitted light with high directivity and high uniformity of in-plane luminance distribution can be obtained.

  The diffractive part 4 is formed in a region on the incident end 5 side of the partition part 12. The diffractive portion 4 is formed on either one or both of the upper surface and the lower surface of the partition portion 12, and is constituted by a concave or V-shaped groove, or a convex or cross-shaped protrusion having a triangular or sawtooth shape. The shape of the diffractive portion 4 is preferably determined so as to maximize the efficiency of one or more orders to be used. These grooves and protrusions can be a diffraction grating or a hologram pattern. Further, a thin metal film or the like is provided on the surface of the partition portion 12 where the diffractive portion 4 is formed so as to be semi-transmissive so that a part of light is transmitted and diffracted by the diffractive portion 4 and the remaining light is reflected and diffracted. May be.

  FIG. 2 is an explanatory diagram showing the diffraction section 4 of the light pipe 1 according to the embodiment of the present invention. 2A is a schematic partial cross-sectional view of the region on the incident end 5 side of the light pipe 1, and FIG. 2B is a schematic perspective view of the region on the incident end 5 side of the light pipe 1. It is.

  As shown in FIGS. 2A and 2B, the light pipe 1 is constituted by a light guide body 2 having a quadrangular cylindrical shape. Inside the light guide 2, a partition portion 12 having a cross-shaped cross section is installed so that the two substrates of the lateral translucent plate 13 a and the longitudinal translucent plate 13 b are orthogonal to each other. The side wall surface 3 of the light guide 2 is constituted by a reflecting surface. A diffractive portion 4 is formed on the upper surface and the side surface (hereinafter collectively referred to as one surface) of the region on the incident end 5 side of the lateral light transmitting plate 13a and the vertical light transmitting plate 13b. The diffractive portion 4 is composed of a large number of grooves 15. The groove 15 is formed in a direction orthogonal to the longitudinal direction of the light guide 2. The interval between the grooves 15 is smaller in the interval P1 on the incident end 5 side than on the interval P2 on the exit end 6 side. That is, the interval between the grooves 15 becomes narrower as the incident end 5 is approached. Thereby, in the vicinity of the incident end 5, light incident at a large incident angle α is incident on the lateral translucent plate 13 a and the longitudinal translucent plate 13 b directly or after being reflected by the reflecting surface 3. Since the larger diffraction is obtained as the distance from 5 increases, the transmission angle transmitted through the lateral translucent plate 13a and the longitudinal translucent plate 13b increases. Then, it is converted into transmitted light that is nearly parallel to the longitudinal direction of the light guide 2. That is, the light is emitted from the emission end 6 at an emission angle β smaller than the incident angle α.

  In particular, out of the light incident on the incident end 5 of the light guide 2, the larger the incident angle α, the more incident on the diffraction section 4 near the incident end 5. The diffractive portion 4 near the incident end 5 is diffracted by a stronger diffracting action because the diffraction groove 15 has a narrower interval than the diffractive portion 4 on the exit end 6 side, and is bent more greatly on the exit end 6 side. Note that LG = W / (tan (β / 2)) where LG is the length of the diffractive portion 4 in the longitudinal direction of the light guide 2 and W is the width of one incident end among the incident ends 5. In this case, light incident at an angle larger than the emission angle β is always incident on the diffraction section 4, and can be emitted from the emission end 6 at a small emission angle β.

  Therefore, the cross-sectional area in the direction orthogonal to the longitudinal direction of the light guide 2 need not be increased on the incident end 5 side and increased on the exit end 6 side, and the exit area of the exit end 6 can be reduced. It is possible to emit light with high directivity that is close to a point light source and has a uniform luminance distribution on the exit surface.

  In the above-described embodiment, the grooves 15 are formed at the same pitch in the horizontal translucent plate 13a and the vertical translucent plate 13b. However, the present invention is not limited to this. For example, the pitch of the grooves 15 formed in the lateral translucent plate 13a can be different from the pitch of the grooves 15 formed in the vertical translucent plate 13b. Further, the groove 15 can be a hologram diffraction pattern instead of a parallel groove. This is particularly effective when the light incident from the incident end 5 has a radial intensity distribution such as a point light source. Further, for example, as an example of the pitch of the diffraction grating, when the incident angle α is 80 ° and the angle at which the light incident on the incident end is emitted from the emission end and the emission angle β is 15 ° or less and the directivity is to be increased, the refractive index If n is 1, the incident angle on the wall surface is θin, and the reflection angle on the wall surface is θ, the pitch size is about 0.67 μm, where m is 1 from the equation p (nsinθ−sinθin) = mλ (m is an integer). Is required. Furthermore, when reflection by several times of diffraction is performed, the pitch may be given so that the total angle of reflection by several times of diffraction is 15 ° or less.

  FIG. 3 is a schematic longitudinal sectional view showing the configuration of the light pipe 1 according to another embodiment of the present invention. A difference from FIG. 1 is that a partition 12 ′ is formed from the incident end 5 toward the exit end 6 to the middle of the light guide 2. Other configurations are the same as those of the light pipe 1 shown in FIG. The same reference numerals are assigned to the same parts or parts having the same function.

  The light pipe 1 is composed of a light guide 2 having a cylindrical shape. A translucent partition portion 12 ′ is formed in the internal space of the light guide 2. The partition portion 12 ′ is formed partway from the incident end 5 side of the light guide 2 toward the exit end 6. That is, the inner space on the incident end 5 side of the light guide 2 is formed so as to be partitioned in the longitudinal direction of the light guide 2. The side wall surface 3 of the light guide 2 is constituted by a reflection surface that reflects light. The light guide 2 receives light from the incident end 5 and emits the incident light from the exit end 6. A diffractive portion 4 is formed on the upper surface of the partition portion 12 on the incident end 5 side. Light incident at an incident angle α is transmitted to the exit end 6 side in the diffraction section 4. In the diffractive part 4, according to the transmission conditions of the diffractive part 4, light of a specific order among the light incident at the incident angle γ1 is transmitted at a transmission angle γ2 having an angle larger than the incident angle γ1. In the partition part 12 ′ other than the diffraction part 4 and the side wall surface 3 of the light guide 2, the incident angle γ3 and the reflection angle γ4 (when light passes through the region where the diffraction part 4 of the partition part 12 ′ is not formed). Is equal to the transmission angle γ4).

  Other configurations are the same as those in FIG. 1 or FIG. By configuring the light pipe 1 in this way, light having high directivity and high uniformity in luminance distribution can be emitted from the emission end 6. In particular, since the end portion of the partition portion 12 ′ is separated from the exit end 6, the emitted light is hardly affected by the end portion of the partition portion 12 ′, and the uniformity of the luminance distribution can be improved. Further, the weight of the light pipe 1 can be reduced.

  FIG. 4 is an explanatory diagram of the illumination optical system 10 according to the embodiment of the present invention. 4A is a schematic longitudinal sectional view showing the illumination optical system 10, and FIGS. 4B to 4D are plan views showing the layout of the light emitting elements 11. The same portions or portions having the same function are denoted by the same reference numerals.

  As shown in FIG. 4A, the light emitting element 11 is installed at the incident end 5 of the light pipe 1 made of the light guide 2. The space surrounded by the side wall surface 3 of the light guide 2 has substantially the same cross-sectional shape in the direction orthogonal to the longitudinal direction of the light guide 2. At least the internal space on the incident end 5 side of the light guide 2 is divided into two by a translucent partitioning portion 12. The light pipe 1 is the same as that described in FIG. 1 or FIG. Similarly to the light pipe 1 described with reference to FIG. 3, the partition portion 12 may be formed partway along the light guide 2, and an interval may be provided between the end portion of the partition portion 12 and the exit end 6.

  The light emitting element 11 includes a base 8 and LEDs 7 a and LEDs 7 b installed on the base 8. The light exit surface 9 a of the LED 7 a has substantially the same shape as the shape of the lower incident end 5 a divided by the partition portion 12, and the light exit surface 9 b of the LED 7 b is the upper portion divided by the partition portion 12. The incident end 5b has substantially the same shape. The exit surfaces 9a and 9b of the LEDs 7a and 7b are installed in close contact with the upper and lower incident ends 5a and 5b, respectively. Therefore, the light emitted from each of the emission surfaces 9a and 9b is introduced into the light guide 2 without leaking outside. The light introduced into the light guide 2 is transmitted to the exit end 6 side by the diffractive portion 4 and is converted into exit light having high directivity and a uniform luminance distribution at the exit end 6. In addition, since light having a wide directivity from the exit surfaces 9a and 9b can also be used as the exit light, the light use efficiency can be improved.

  The present embodiment shown in FIG. 4A is a case where the internal space of the light guide 2 is divided into two parts by the partitioning section 12, but instead of this, it is divided into four parts as shown in FIG. Multiple division may be performed. Further, the LED 7a and the LED 7b may have the same or different emission colors. Moreover, the partition part 12 installed inside the light guide 2 is divided into four when the cross section as shown in FIG. 2 has a cross shape and the inner space of the light guide 2 is divided into four. Four LEDs emitting the same color may be installed at the incident end, or LEDs emitting different colors may be installed.

  FIG. 4B is a plan view of the light emitting element 11 viewed from the light guide 2 side when the internal space of the light guide 2 is divided into two by a partition portion 12 made of a single translucent plate. . The light emitting element 11 includes an LED 7 a and an LED 7 b installed on the base 8. The light emission surfaces of the LEDs 7 a and 7 b have substantially the same shape as the divided incident ends 5 a and 5 b of the light guide 2. If the LEDs 7a and 7b have complementary colors such as blue and yellow and red and green, white light can be emitted from the emission end 6.

  4 (c) and 4 (d) show a light guide when the internal space on the incident end 5 side of the light guide 2 is divided into four by a partition part 12 made of a light-transmitting plate having a cross-shaped cross section. FIG. 3 is a plan view of the light emitting element 11 viewed from the body 2 side. As shown in FIG. 4C, the light emitting element 11 is provided with a red light emitting LED 7R, a green light emitting LED 7G, and a blue light emitting LED 7B installed on the base 8. The light emission surfaces of the LEDs 7R, 7G, and 7B have substantially the same shape as the four divided incident ends of the light guide 2. All the colors can be emitted by the light emission of the three primary colors of the LEDs 7R, 7G, and 7B. Further, by using the two green LEDs 7G, it is possible to emit light that matches the visibility characteristic.

  Further, as shown in FIG. 4D, a red light emitting LED 7R, a green light emitting LED 7G, a blue light emitting LED 7B, and a white light emitting LED 7W can be installed on the base 8. While white light is obtained by additive color mixture of red, green, and blue, and a white light emitting LED 7W is provided, all colors can be emitted, and bright white light can be obtained.

  FIG. 5 is a schematic cross-sectional view showing the image projection apparatus 20 according to the embodiment of the present invention. The image projection apparatus 20 includes a light combining unit 22, three light modulation units 21R, 21G, and 21B provided on three sides of the light combination unit 22, and three light modulation units 21R, 21G, and 21B. The three relay lenses 24R, 24G, and 24B, three illumination optical systems 10R, 10G, and 10B provided corresponding to the three relay lenses 24R, 24G, and 24B, and the projection unit 23, respectively. Here, the light combining unit 22 is configured by a dichroic prism. The light modulator 21R is a liquid crystal display element that displays a red image, the light modulator 21G is a liquid crystal display element that displays a green image, and the light modulator 21B is a liquid crystal display element that displays a blue image. Each of the three illumination optical systems 10R, 10G, and 10B has a green light emission including a red light emitting element 11R including red light emitting LEDs 7a and 7b and a green light emitting LED at an incident end 5 of the light pipe 1 including the light guide 2. An element 11G and a blue light emitting element 11B including a blue light emitting LED are provided. The projection unit 23 includes a projection lens system for projecting an image.

  The exit end 6 of each of the illumination optical systems 10R, 10G, and 10B has a surface shape similar to the shape of the display effective area of each of the light modulation units 21R, 21G, and 21B. When the display effective area of each of the light modulation units 21R, 21G, and 21B has a quadrangle, and the ratio of the length and width of the quadrangle is, for example, 3 to 4, each of the illumination optical systems 10R, 10G, and 10B also has a quadrangle. The aspect ratio of the rectangular injection end 6 is also set to 3 to 4. A partition portion 12 having a cross-shaped cross section is installed inside the light guide 2, and a diffraction portion 4 including a plurality of grooves is formed on the surface of the incident end 5 of the partition portion 12. The pitch of many grooves becomes narrower as it approaches the incident end 5 side. In addition, a large number of grooves formed on the surface of the translucent plate 13a constituting the cross shape of each illumination optical system 10R, 10G, and 10B, and a large number of grooves formed on the surface of the vertical translucent plate 13b Are different in the interval between adjacent grooves. Also, in each of the illumination optical systems 10R, 10G, and 10B, the groove intervals are formed in accordance with the emission colors of the light emitting elements 11R, 11G, and 11B.

  The light emitted from each of the illumination optical systems 10R, 10G, and 10B is substantially parallel or matched with the numerical aperture of the projection lens via the relay lenses 24R, 24G, and 24B, and the light modulators 21R and 21G. , 21B. Each of the light modulation units 21R, 21G, and 21B converts incident illumination light into image light corresponding to each color. Image light emitted from each of the light modulation units 21R, 21G, and 21B is additively mixed by the light combining unit 22 and projected onto a screen or the like via the projection unit 23. By configuring in this way, it is possible to configure a light and compact image projector 20 with high light efficiency.

  In the above embodiment, the relay lenses 24R, 24G, and 24B are provided between the illumination optical systems 10R, 10G, and 10B and the light modulators 21R, 21G, and 21B. However, the relay lenses 24R, 24G, and 24B can be removed, and the light modulation units 21R, 21G, and 21B corresponding to the illumination optical systems 10R, 10G, and 10B can be disposed close to each other. In this case, the shape of the exit end 6 of each of the illumination optical systems 10R, 10G, and 10B and the shape of the effective display area of each of the light modulators 21R, 21G, and 21B can be made substantially the same surface shape. Moreover, you may make it provide the space | interval between the partition part 12 in the light guide 2 of each illumination optical system 10R, 10G, 10B between the edge part and the injection | emission end 6. FIG.

  FIG. 6 is a schematic cross-sectional view showing an image projector 20 according to another embodiment of the present invention. The same portions or portions having the same function are denoted by the same reference numerals. In FIG. 6, the image projection apparatus 20 includes an illumination optical system 10, a relay lens 24, a reflective light modulation unit 21, and a projection unit 23 that projects image light reflected from the light modulation unit 21. Yes. The illumination optical system 10 includes a light guide 2, a partition 12 provided in the light guide 2, and a light emitting element 11 provided at the incident end 5 of the light guide 2. The light emitting element 11 includes a base body 8, a red light emitting LED 7R provided on the base body 8, a green light emitting LED 7G (not shown), and a blue light emitting LED 7B. The LEDs 7R, 7G, and 7B are integrated and installed on the base 8, and the entire light emitting surface of the LEDs 7R, 7G, and 7B has substantially the same shape as the incident surface of the incident end 5, and the end of the light guide 2 It is installed in close contact with. Therefore, the light of each LED 7R, 7G, 7B does not leak outside. The light of the colors of the LEDs 7R, 7G, and 7B is repeatedly reflected on the diffraction portion 4 and the side wall surface 3 of the partitioning portion 12, and is converted into emitted light having a uniform luminance distribution and high directivity on the exit surface of the exit end 6. The

  The light modulation unit 21 is configured by a DMD element. The DMD element is configured such that a large number of micromirrors can rotate according to an image signal. The light emitted from the illumination optical system 10 is irradiated onto the DMD element via the relay lens 24, reflected according to the display image by a large number of micromirrors of the DMD element, and via the projection unit 23 configured by the lens system. Projected onto a screen or the like.

  The DMD element operates as follows. A light source driving circuit that drives the light emitting element 11 drives each of the LEDs 7R, 7G, and 7B in a time-sharing manner to sequentially emit red, green, and blue light. A display driving circuit that drives the DMD element sequentially displays a red image, a green image, and a blue image on the DMD element in synchronization with the time-division driving. As a result, red, green, and blue images are sequentially projected from the projection unit 23, and the observer views these colors as time-averaged images. As a light color mixing method, as shown in FIG. 5, the illumination optical system 10 of different colors, for example, each of the illumination optical systems 10 of red, green, and blue, is combined and mixed by the light combining unit 22, The combined light may be applied to the reflective light modulation unit 21 via the relay lens 24, and image light may be projected by the projection unit 23 that projects the light modulated by the light modulation unit 21. In FIG. 6, the relay lens 24 is provided in the gap between the illumination optical system 10 and the light modulation unit 21, but the relay lens 24 can be omitted. Further, as the light modulation unit 21, a reflective liquid crystal display element can be used instead of the DMD element.

DESCRIPTION OF SYMBOLS 1 Light pipe 2 Light guide 3 Side wall surface 4 Diffraction part 5 Incident end 6 Ejection end 7 LED
8 Substrate 9 Emitting surface 10 Illumination optical system 20 Image projection device

Claims (11)

In the light pipe that the side wall surface is made of a cylindrical light guide having a reflection surface, and the light is introduced from the incident end and repeatedly reflected on the side wall surface to emit the light from the emission end.
The light guide is configured with a translucent partition that partitions at least the incident space side internal space of the light guide in the longitudinal direction of the light guide.
A diffractive part is formed on the surface of the region on the incident end side of the partition part,
A light pipe, wherein an emission angle of light emitted from the emission end is smaller than an incident angle of light introduced from the incident end. The partition part has a cross shape so that two translucent plates are orthogonal to each other, and the internal space is divided into four parts,
The light pipe according to claim 1, wherein the diffractive portion is formed on a surface of the two translucent plates. The diffraction part has a plurality of grooves,
3. The light pipe according to claim 1, wherein an interval between the plurality of grooves becomes narrower toward the incident end. 4. The diffraction part has a plurality of grooves,
4. The light pipe according to claim 2, wherein intervals between the plurality of grooves are different from each other in the two light-transmitting plates orthogonal to each other. 5.   An illumination optical system comprising: the light pipe according to any one of claims 1 to 4; and a light emitting element installed at the incident end of the light pipe. The incident end is divided by the partition;
The illumination optical system according to claim 5, wherein a plurality of the light emitting elements are installed corresponding to the divided incident ends.   The illumination optical system according to claim 5 or 6, wherein a shape of a light emitting surface of the light emitting element is substantially the same as a shape surrounded by the side wall surface and the partition portion at the incident end. .   The light incident element is divided into four by the partition part, and light emitting elements of red, green, blue, and white emission colors are installed at the four divided light incident edges. The illumination optical system according to claim 6 or 7.   The light incident end is divided into four by the partition part, and light emitting elements of red, green, green, and blue emission colors are installed at the four divided light incident ends. The illumination optical system according to claim 6 or 7.   An illumination optical system according to any one of claims 5 to 9, a light modulation unit that converts illumination light emitted from the illumination optical system into image light, and a projection unit that projects the image light. An image projection apparatus provided. The illumination optical system has three primary colors, respectively.
A light combining unit that combines light emitted from each of the illumination optical systems;
The light modulating unit that modulates the light combined by the light combining unit;
The image projection device according to claim 10, further comprising: the projection unit that projects the light modulated by the light modulation unit.

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