JP2008046328A - Video projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that the intensity of emitted light in the area of a periphery part is reduced in comparison with that in the area of a projection optical axis as a projection viewing angle gets larger with respect to the projection optical axis of a video projection device when the image is projected by the video projection device. <P>SOLUTION: The video projection device is equipped with: a light source part which condenses emitted light; a light pipe on which the condensed light is made incident from an incident surface and which guides it to emit from an emitting surface; an electrooptic element which converts the emitted light into video light; and a projection lens part which projects the video light, wherein the condensed light is set to deviate from the optical axis of the light pipe on the incident surface of the light pipe. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a video projection apparatus that incorporates an electro-optic element such as a liquid crystal display element and projects an image on a projection screen or the like.

  2. Description of the Related Art In recent years, video projectors incorporating electro-optic elements such as liquid crystal display elements and DMD (digital micromirror device) display elements have become widespread. This type of image projection apparatus is easy to carry, and is installed on a desk or the like, and is used by enlarging and projecting image light toward an upward projection screen that is higher than the height of the desk. For this reason, the optical axis of the projection lens of the image projection apparatus does not match the center of the projection screen.

  FIG. 7 is a schematic view of this type of conventionally known video projector 100 (see, for example, Patent Document 1). The video projection apparatus 100 includes a casing 101, a scanning panel 103, a projection lens unit 102, and the like. FIG. 8A is a block diagram of the video projection apparatus 100 for explaining the path of light projected from the video projection apparatus 100 toward the projection screen, and FIG. FIG. 8C is a graph showing the relationship between the position on the lens 114 and the light intensity for light, and FIG. 8C is a graph showing the relationship between the position on the projection screen and the light intensity.

  In FIG. 8A, the light emitted from the light source 112 is reflected by the reflector 111 and collected. The condensed light is incident on the incident surface of the light pipe 113 and is repeatedly reflected from the inner surface of the light pipe 113 and is emitted from the emission surface. The emitted light is collimated by the lens 114 and applied to the liquid crystal display element 115. The irradiated light is converted into image light by the liquid crystal display element 115 and projected onto the projection screen 117 by the projection lens unit 116. In this case, the optical axis 125 of the light source unit constituted by the light source 112 and the reflector 111, the optical axis 126 of the light pipe 113, the lens 114, and the optical axis 127 of the liquid crystal display element 115 all coincide. Further, the optical axis 128 of the projection lens unit 116 does not coincide with the center of the projection screen 117. The projected image light is enlarged and projected above the optical axis 128. Note that the optical axis 126 of the light pipe 113 is an axis that coincides with the optical axis of the incident light when the incident incident light is emitted from the exit surface as the emitted light having a uniform light intensity distribution.

A graph 119 in FIG. 8B represents the incident light intensity distribution in the vertical direction of the lens 114 when light having a uniform intensity distribution is emitted from the exit surface of the light pipe 113. The horizontal axis represents the incident light intensity in arbitrary units, and the vertical axis 118 represents the position of the lens 114 in the vertical direction. The graph 121 of FIG. 8C shows the incident light intensity in the vertical direction of the projection screen 117 when the liquid crystal display element 115 is in a transmissive state and the emitted light having a uniform intensity distribution is emitted from the emission surface of the light pipe 113. Represents the distribution. The horizontal axis represents the incident light intensity in arbitrary units, and the vertical axis 120 represents the vertical position of the projection screen 117. Thereby, in the lens 114, the incident light intensity is substantially uniform from the center of the lens 114 toward the outer periphery, whereas on the projection screen 117, the incident light intensity is increased from the optical axis 128 of the projection lens unit 116 toward the outer periphery. Will decline.
JP 2005-208174 A

  As shown in FIG. 8C, the light intensity of the image light projected from the projection lens unit 116 is the strongest in the optical axis direction of the projection lens unit 116, and the light intensity gradually decreases toward the outer periphery. For this reason, the projection image on the projection screen 117 has a problem that the lower side, which is the optical axis direction of the projection lens unit 116, is bright and the upper side is dark, which makes it difficult to see.

In the present invention, the following means have been taken in order to solve the above problems.
In the invention which concerns on Claim 1, the light source part which condenses the emitted light, the light pipe which injects the condensed light from the incident surface, guides it and injects it from the emission surface, and the emitted light In a video projection device comprising an electro-optic element for converting to video light, and a projection lens unit for projecting the video light, the light pipe emits the condensed light on the incident surface from the optical axis of the light pipe. The video projection apparatus is characterized in that it is incident at a shifted position.

  In the invention according to claim 2, the optical axis of the light source unit does not coincide with the optical axis of the light pipe, and substantially coincides with the optical axis of the electro-optic element. It was set as the image projection apparatus of description.

  According to a third aspect of the present invention, in the video projection device according to the first or second aspect, the optical axis of the light source unit is parallel to the optical axis of the light pipe.

  The invention according to claim 4 is characterized in that the irradiation light emitted from the emission surface of the light pipe and applied to the electro-optic element has an asymmetric intensity distribution with respect to the optical axis of the electro-optic element. The video projection device according to any one of claims 1 to 3.

  In the invention which concerns on Claim 5, the light which injects at the largest angle with respect to the optical axis of the said light pipe among the said condensed light which injects in the position shifted from the optical axis of the said light pipe in the said entrance plane When the light pipe is reflected an odd number of times in the light pipe and emitted from the emission surface, the intensity of the emitted light on the emission surface of the light pipe is from the optical axis of the light pipe with respect to the optical axis of the light pipe. The video projector according to claim 1, wherein the video projector is maximum in a direction opposite to the direction of the shifted position.

  According to a sixth aspect of the present invention, when the projection field angle upward with respect to the optical axis of the projection lens unit is larger than the projection field angle downward, the light pipe has the light condensing on the incident surface. The image projection apparatus according to claim 5, wherein the incident light is incident at a position shifted downward from the optical axis of the light pipe.

  In the invention which concerns on Claim 7, the light which injects at the maximum angle with respect to the optical axis of the said light pipe among the said condensed light which injects in the position shifted from the optical axis of the said light pipe in the said entrance plane Is reflected an even number of times in the light pipe and emitted from the exit surface, the intensity of the emitted light at the exit surface of the light pipe is from the optical axis of the light pipe with respect to the optical axis of the light pipe. 5. The video projection device according to claim 1, wherein the video projection device has a maximum in the same direction as the direction of the shifted position.

  In the invention according to claim 8, when the projection field angle upward with respect to the optical axis of the projection lens unit is larger than the projection field angle downward, the light pipe has the light condensing on the incident surface. The image projection apparatus according to claim 7, wherein the incident light is incident at a position shifted upward from the optical axis of the light pipe.

  In the invention which concerns on Claim 9, the said projection lens part has a maximum projection view angle of 45 degrees or more with respect to the optical axis of the said projection lens part, The any one of Claims 1-8 characterized by the above-mentioned. The video projection apparatus described in 1.

  In the invention which concerns on Claim 10, It has a moving means for moving the incident position which injects the said condensed light with respect to the optical axis of the said light pipe, The any one of Claims 1-9 characterized by the above-mentioned. The video projection device described in item 1 was used.

  In the invention which concerns on Claim 11, the said moving means is a moving means for moving to the orthogonal | vertical direction with respect to the optical axis of the said light pipe, Comprising: One end hold | maintains the said light pipe or the said light pipe The image projection device according to claim 10, wherein the image projection device is a position adjusting screw that is in contact with the other end and is rotatably supported by the fixed portion.

  The invention according to claim 12 is the video projection apparatus according to claim 10, wherein the moving means is an actuator that enables movement in a direction perpendicular to the optical axis of the light pipe. .

  According to the video projection device of the present invention, the condensed light incident on the incident surface of the light pipe is shifted from the optical axis of the light pipe. The peripheral part away from the optical axis is stronger than the vicinity of the optical axis. As a result, the image projected on the projection screen can reduce the difference in light intensity between the projection area having a small projection angle of view and the projection area having a large projection angle of view with respect to the optical axis of the projection lens unit. It is possible to improve the uniformity of the brightness of the projected image light.

  Further, the optical axis of the light source unit and the optical axis of the electro-optical element are made substantially the same, and only the optical axis of the light pipe is shifted. Thereby, the light intensity distribution of the emitted light emitted from the light pipe can be changed by shifting only the position of the light pipe, and there is an advantage that the light intensity distribution can be easily adjusted.

  Also, the optical axis of the light source unit and the optical axis of the light pipe are made parallel. Thereby, only the light intensity distribution of the emitted light emitted from the light pipe can be asymmetrical, and there is an advantage that adjustment of the irradiation direction and the like of the irradiation light irradiated on the electro-optic element is facilitated.

  Further, the irradiation light emitted from the light pipe exit surface and applied to the electro-optical element has an asymmetric intensity distribution with respect to the optical axis of the electro-optical element, that is, the central portion of the electro-optical element. Thus, even when an image is enlarged and projected upward from the optical axis of the projection lens unit, there is an advantage that a projected image with improved brightness uniformity can be obtained on the projection screen.

  In addition, the intensity distribution of the emitted light on the light pipe exit surface is such that when the light incident on the light pipe incident surface at the maximum angle with respect to the optical axis of the light pipe is reflected an even number of times in the light pipe, Maximum in the direction opposite to the direction of incidence on the incident surface with respect to the optical axis of the light pipe, and when reflected an odd number of times, maximum in the same direction as the direction of incidence on the incident surface with respect to the optical axis of the light pipe It was made to become. This has the advantage that the light emitted from the exit surface of the light pipe can have an asymmetric intensity distribution with respect to the optical axis by a simple method.

  Further, when the image light projected from the projection lens unit is enlarged and projected upward with respect to the optical axis of the projection lens unit, the light incident at the maximum angle with respect to the optical axis of the light pipe is reflected in the light pipe. Light is incident at the maximum angle with respect to the optical axis of the light pipe so that the light condensed on the incident surface of the light pipe is incident below the optical axis of the light pipe. When the light pipe is reflected an odd number of times, the light condensed on the incident surface of the light pipe is made to enter above the optical axis of the light pipe. Accordingly, there is an advantage that the light intensity distribution can be compensated on the projection screen, and a projection image with improved brightness uniformity can be obtained.

  In addition, in the region where the projection angle of view of the projected image light is 45 ° or more with respect to the optical axis of the projection lens unit, the light intensity of the image light is significantly reduced. Therefore, it is particularly effective to allow the light collected at a position shifted from the optical axis of the light pipe to be incident.

  In addition, since the moving means for moving the position of the light pipe is provided, the moving amount of the light pipe can be adjusted while actually projecting the image light, and there is an advantage that the convenience is high.

  Other effects of the present invention will be described in the description of each embodiment.

  In an embodiment of the present invention, a light source unit that collects emitted light, a light pipe that enters and guides the collected light from an incident surface, and emits light from an exit surface; and a light pipe An electro-optical element that converts the emitted light into image light and a projection lens unit that projects the image light emitted from the electro-optical element onto a projection screen or the like are provided. In this case, the light pipe enters the light collected by the light source unit on the incident surface at a position shifted from the optical axis of the light pipe, and the light intensity distribution of the image light projected from the projection lens unit is uneven. To compensate. Here, a transmissive liquid crystal display element can be used as the electro-optical element. Further, instead of the liquid crystal display element, a DMD display element, an electrophoretic element, or other transmission type or reflection type display element can be used. In the present embodiment, the solid light pipe and the hollow light pipe or the light tube are collectively referred to as a light pipe.

  In addition, the optical axis of the light source unit and the optical axis of the electro-optic element are substantially matched so that the optical axis of the light pipe does not match the optical axis of the light source unit. Thereby, the uniformity of the brightness of the projected image can be easily improved without complicating the optical system.

  Also, the optical axis of the light source unit and the optical axis of the light pipe are made parallel. Thereby, since only the light intensity distribution of the emitted light emitted from the light pipe can be made asymmetrical, the adjustment of the optical axis with other components can be easily performed.

  Further, the irradiation light emitted from the light pipe exit surface and applied to the electro-optical element has an asymmetric intensity distribution with respect to the optical axis of the electro-optical element, that is, the central portion of the electro-optical element. For example, with reference to the optical axis that is the center of a liquid crystal display element that is an electro-optic element, the intensity of light irradiated near the upper side of the liquid crystal display element is strong, and the irradiation light irradiated toward the lower side of the liquid crystal display element gradually increases. Make it weak. As described above, this can be obtained by causing the light condensed by the light source unit to enter the position shifted from the optical axis of the light pipe. As a result, even when an image is enlarged and projected upward from the optical axis of the projection lens unit, a projected image with improved brightness uniformity can be obtained on the projection screen.

  In addition, the light collected from the light source on the incident surface of the light pipe is incident on a position shifted from the optical axis of the light pipe, and the light emitting surface from which the light pipe emits is also shifted from the optical axis of the light pipe. The intensity of the emitted light is maximized at the position. In this case, when the light incident at the maximum angle with respect to the optical axis of the light pipe is reflected an odd number of times in the light pipe and is emitted from the exit surface, the light pipe is referenced with respect to the optical axis of the light pipe. The intensity of the emitted light is maximized in the direction opposite to the direction of the position shifted from the optical axis. Further, when the light pipe is reflected an even number of times and is emitted from the exit surface, the intensity of the emitted light is in the same direction as the position shifted from the optical axis of the light pipe with respect to the optical axis of the light pipe. Try to be the maximum. This makes it possible to easily obtain asymmetric light on the exit surface of the light pipe without the need to add other components.

  Further, by shifting the optical axis of the light source unit upward or downward with respect to the optical axis of the light pipe, the intensity distribution of the emitted light emitted from the light pipe can be biased upward with respect to the optical axis of the light pipe. it can. Specifically, when light having the maximum angle with respect to the optical axis of the light pipe is reflected an odd number of times in the light pipe, the incident light to the light pipe is directed to the optical axis of the light pipe. If it is shifted downward and reflected an even number of times, the incident light to the light pipe should not be directed upward. Thereby, it is possible to make the luminance of the image light projected enlarged and deviated upward with respect to the optical axis of the projection lens unit uniform. In particular, when the projection angle of view is 45 ° or more with respect to the optical axis of the projection lens unit, the light intensity decreases in the peripheral region of the projected image light. Therefore, when the projection lens unit has such a projection angle of view, it is particularly effective to make the light collected by the light source unit enter the light pipe while being shifted from the optical axis.

  Further, a light pipe moving means for moving the position of the light pipe is provided. The moving means may be manually moved or may be moved by an actuator.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  FIG. 1A is an explanatory diagram for explaining a path of light projected from the image projection apparatus 1 according to the present embodiment toward the projection screen 8, and FIG. FIG. 1C is a graph showing the relationship between the position of the projection screen 8 and the light intensity. The same parts or the same functions are denoted by the same reference numerals.

  In FIG. 1A, a light source unit is configured by the light source 3 and the reflector 2. A mercury lamp or a xenon lamp can be used as the light source. The light emitted from the light source 3 is reflected by the reflector 2 and collected on the incident surface 25 of the light pipe 4. The light pipe 4 is made of a hollow rectangular column whose inner surface is coated with a reflective film, or a transparent square column made of glass or the like and whose surface is formed with a reflective film. can do. The light incident on the light pipe 4 is repeatedly reflected and transmitted by the reflection film formed on the inner surface or the outer surface, and is emitted from the emission surface 26. The emitted light is applied to the transmissive liquid crystal display element 6 by the lens 5 with parallel rays or a specific F value. In the liquid crystal display element 6, a large number of pixels including a liquid crystal layer are arranged in a matrix, and the amount of transmitted light of each pixel is controlled in accordance with an image signal to modulate incident light into video light. The modulated image light is projected onto the projection screen 8 by the projection lens unit 7 to display an image.

  Here, the optical axis in each part will be described. FIG. 2 is an enlarged view of part A in FIG. The reflected light 20 reflected from the reflector 2 is collected on the light incident surface 25 of the light pipe 4 on the optical axis 13 of the light source unit. This condensing point is separated from the optical axis 14 of the light pipe 4 by a distance d. Further, the optical axis 15 of the lens 5 and the optical axis 16 of the liquid crystal display element 6, that is, a perpendicular line passing through the center of the liquid crystal display element 6, and the optical axis 13 of the light source section are substantially coincident. Further, the optical axis 16 of the liquid crystal display element 6 and the optical axis 17 of the projection lens unit 7 do not necessarily match. The image light emitted from the liquid crystal display element 6 enters from a lower region or an upper region than the optical axis 17 of the projection lens unit 7. The optical axis 17 of the projection lens unit 7 does not coincide with the center of the projection screen 8, and the image light 18 is projected largely biased upward by the projection lens unit 7.

  A graph 10 in FIG. 1B represents the intensity distribution of the emitted light at the position of the lens 5, the horizontal axis represents the light intensity, and the vertical axis represents the lens position. A graph 12 in FIG. 1C represents the intensity distribution of the projection light on the projection screen 8, the horizontal axis represents the light intensity, and the vertical axis represents the screen position. By making the light condensed by the light source part enter the distance d from the optical axis 14 on the incident surface 25 of the light pipe 4, the upper part of the emitted light emitted from the emission surface 26 is strongly below the center. Can be emitted light having a weak intensity distribution. As a result, the image light projected from the projection lens unit 7 can have a uniform light intensity on the projection screen 8 as shown in the graph 12. An optimal intensity distribution can be obtained by appropriately setting the distance d according to the distance between the projection screen 8 and the projection lens unit 7 and the angle between the projection screen 8 and the optical axis 17 of the projection lens unit 7. .

  When a reflective liquid crystal display element or a DMD display element is used instead of the transmissive liquid crystal display element 6, the optical axis 16 of the liquid crystal display element 6, the optical axis 15 of the lens 5, and the optical axis of the light source unit. 13 do not need to match.

  Moreover, in the said embodiment, the image projection apparatus 1 was installed, for example on the desk, and the example which installed the projection screen 8 in the position higher than the height of the desk was demonstrated. However, the present invention is not limited to this arrangement. For example, the present invention can also be applied to a case where projection is performed obliquely downward from the upper surface of the desk toward the surface of the desk. For example, when the projection light is enlarged and projected from the −X direction on the desk toward the + X direction, “upper” in the above description corresponds to the + X direction, and the lower side in the above description corresponds to the −X direction. That is, when projecting image light from the left direction on the desk to the right direction, the light collected from the light source unit on the incident surface 25 of the light pipe 4 is left with respect to the optical axis 14 of the light pipe 4. What is necessary is just to make it shift to a direction.

  In the above embodiment and FIG. 1, the image light emitted from the liquid crystal display element 6 passes through the projection lens unit 7 and is enlarged and projected as an erect image. Next, unlike the case of FIG. 1, the case where the projection lens unit 7 projects an enlarged image as an inverted image will be described.

  In this case, the arrangement of each part may be as follows. In FIG. 1A, the light pipe 4 is shifted downward. Therefore, the light collected from the reflector 2 is incident above the optical axis 14 of the light pipe 4. Then, the light emitted from the light pipe 4 is reversed upside down from the intensity shown in FIG. 1B, the lower light intensity is strong, and the upper light intensity is weak. Next, the position of the projection lens unit 7 is moved upward so that the image light emitted from the liquid crystal display element 6 enters the region below the optical axis 17 of the projection lens unit 7. That is, the optical axis 17 of the projection lens unit 7 is set to be located above the optical axis 16 of the liquid crystal display element 6. Thereby, the image light emitted from the projection lens unit 7 is enlarged and projected above the optical axis 17 of the projection lens unit 7. As a result, the image of the lower side of the liquid crystal display element 6 is projected onto the upper side of the projection screen 8, and the image of the upper side of the liquid crystal display element 6 is projected onto the lower side of the projection screen 8. By disposing the respective components in this way, an image with uniform light intensity is projected onto the projection screen 8.

  In the above description, when the optical axis 13 of the light incident on the incident surface 25 of the light pipe 4 is shifted downward (or upward) with respect to the optical axis 14 of the light pipe 4, the light pipe 4 is emitted. The light emitted from the surface 26 is a case where the light intensity at the upper part (or lower part) is strong and the light intensity at the lower part (or upper part) is weak with respect to the optical axis 14. That is, the intensity distribution of incident light on the incident surface 25 is emitted from the emission surface 26 with a substantially symmetric distribution with respect to the optical axis 14 of the light pipe 4. However, this relationship is not always obtained from the reflection of light in the light pipe 4.

  FIG. 3 is an explanatory diagram showing the optical path of the video projector 1 more specifically. FIG. 3A shows the light having the maximum angle with respect to the optical axis 14 out of the light incident on the light pipe 4. When the light pipe 4 is reflected an odd number of times, FIG. 3B shows a case where the light pipe 4 is reflected an even number of times. The same parts or parts having the same function are denoted by the same reference numerals.

  In FIG. 3A, the light pipe 4a is a solid type of a quadrangular prism made of a transparent material, for example, and the light taken inside is totally reflected on its side surface. The reflected light 20 reflected and collected from the reflector 2 around the optical axis 13 of the light source unit is incident on a region above the optical axis 14 of the incident surface 25 of the light pipe 4a. Of the light incident on the light pipe 4a, the light having the maximum angle α with respect to the optical axis 14 is reflected twice on the side surface of the light pipe 4a as shown in FIG. The light is emitted from above the optical axis 14. The intensity of the emitted light at the exit surface 26 is maximized in the region above the optical axis 14 and becomes weaker as it goes from the optical axis 14 and the region below the optical axis 14. That is, the intensity of the emitted light is maximized in the same direction as the direction of the incident position on the incident surface 25 with respect to the optical axis 14 of the light pipe 14a.

  Then, the emitted light emitted from the emission surface 26 is applied to the effective display surface of the liquid crystal display element 6 that is an electro-optic element through the lens 5. In particular, in the case of FIG. 3A, the intensity of the light applied to the lower part of the liquid crystal display element 6 is greater than the intensity of the light applied to the upper part. Then, the image light modulated by the liquid crystal display element 6 by the projection lens 27 of the projection lens unit 7 is inverted and projected onto the projection screen 8. Since the image of the lower part of the liquid crystal display element 6 having a high light intensity is projected on the upper part of the projection screen 8, the light intensity is compensated and an image with a more uniform brightness can be projected. In the above embodiment, the light having the maximum angle α with respect to the optical axis 14 is reflected twice on the side surface of the light pipe 4a out of the light incident on the light pipe 4a. The same applies to the case of multiple reflections. In the above-described embodiment, a solid type is used as the light pipe 4a. However, the same applies even when a hollow type light pipe is used.

  On the other hand, FIG. 3B shows a case where light having the maximum angle α is reflected three times among the light incident on the light pipe 4b. The reflected light 20 reflected and collected from the reflector 2 around the optical axis 13 of the light source unit is incident on a region below the optical axis 14 of the incident surface 25 of the light pipe 4b. Of the light incident on the light pipe 4b, the light having the maximum angle α with respect to the optical axis 14 is reflected twice on the side surface of the light pipe 4b as shown in FIG. The light is emitted from above the optical axis 14. The intensity of the emitted light at the exit surface 26 is maximized in the region above the optical axis 14 and becomes weaker as it goes from the optical axis 14 and the region below the optical axis 14. That is, the intensity of the emitted light is maximized in a direction opposite to the direction of the incident position on the incident surface 25 with respect to the optical axis 14 of the light pipe 14b. The subsequent optical paths are the same as in FIG. In the above embodiment, the light having the maximum angle α with respect to the optical axis 14 is reflected three times on the side surface of the light pipe 4b out of the light incident on the light pipe 4b. The same is true for an odd number of reflections. In the above-described embodiment, a solid type is used as the light pipe 4b. However, the same applies even when a hollow type light pipe is used.

  FIG. 4A is a schematic diagram showing a state in which image light is projected onto the projection screen 8 by the general image projection apparatus 1. An angle formed by the projection image and the optical axis 17 of the projection lens unit 7 is defined as a projection field angle θ. FIG. 4B is a graph showing the relationship between the projection angle of view θ and the intensity ratio of the projection light on the projection screen 8. The graph 30 represents the light intensity ratio of the projection light on the projection screen 8, the horizontal axis is the projection field angle θ, and the vertical axis is the light intensity ratio on the projection screen 8. As is apparent from the graph 30, when the projection angle of view θ exceeds 45 °, the light intensity ratio rapidly decreases. Therefore, in the present embodiment in which the light collected by the reflector 2 shown in FIG. 1 is shifted from the position of the optical axis 14 of the light pipe 4, the projection lens unit 7 having a projection field angle θ of 45 ° or more is more effective. It can be understood that.

  FIG. 5 is a schematic cross-sectional view showing a holding mechanism for the light pipe 4 mounted inside the video projector 1. The light pipe 4 is held between the top plate 40 and the bottom plate 44 of the housing. The light pipe 4 is held by an upper support member 42 and a lower support member 43. Then, two springs 41 are provided between the upper support member 42 and the upper plate 40 to press the light pipe 4 downward, and the position of the light pipe 4 between the lower support member 43 and the bottom plate 44 of the housing. An adjusting screw 45 for adjusting the light pipe 4 is provided to hold the light pipe 4. An image may be projected onto the projection screen 8 during use, and the position of the light pipe 4 may be adjusted with the adjusting screw 45 as necessary.

  In addition, although the light source part, the liquid crystal display element 6, and the projection lens part 7 were fixed and the example which moves only the light pipe 4 with respect to the optical axis 13 of a light source part was demonstrated, it is not limited to this. Only the optical axis 13 of the light source unit may be moved with respect to the optical axis 14 of the light pipe 4, or the lens 5, the liquid crystal display element 6, and the projection lens unit 7 may be moved together with the light pipe 4. May be. In short, the position of the condensing point condensed by the reflector 2 may be shifted with respect to the optical axis 14 on the incident surface 25 of the light pipe 4.

  FIG. 6 is a schematic cross-sectional view showing a modified example of the holding mechanism that holds the light pipe 4 shown in FIG. An upper guide 46 is installed on the upper plate 40 of the casing, and a lower guide 47 is installed on the bottom plate 44. Further, the light pipe 4 is provided with support members 48 in the vicinity of both side surfaces of the entrance surface 25 and the exit surface 26. The light pipe 4 is pressed downward by a spring 41 provided between the upper plate 40 of the casing and is held by an adjusting screw 45 provided between the bottom plate 44 of the casing. By rotating the adjusting screw 45, it is guided by the upper guide 46 and the lower guide 47 and can be moved and adjusted in the vertical direction.

  The moving mechanism of the light pipe 4 is not limited to the above example, and the adjustment screw 45 may be adjusted by being rotated by an actuator such as a motor provided in the housing. For example, a lower support member is provided at the lower portion of the light pipe 4 and a bolt with a screw cut is fixed to the support member. Further, the bolt is inserted into the inner periphery to cut the screw for enabling vertical movement, and an ohmic gear is formed on the outer periphery to be freely rotated and attached to the housing. The ohmic gear is rotated by a motor to move the light pipe 4 up and down. A motor control switch may be provided on the operation panel of the housing to control the position of the light pipe 4 from the outside.

1 is a schematic block diagram of a video projection apparatus according to an embodiment of the present invention. It is a figure which shows the relationship between the optical axis of the light pipe which concerns on embodiment of this invention, and the optical axis of a light source part. It is explanatory drawing which represents more specifically the optical path of the image projection apparatus 1 which concerns on embodiment of this invention. It is the outline figure which shows the state which is projecting the image | video with the general image | video projection apparatus, and the graph showing a projection view angle and a light intensity ratio. It is a general-view figure showing the support mechanism of the light pipe which concerns on embodiment of this invention. It is a general-view figure showing the support mechanism of the light pipe which concerns on embodiment of this invention. It is a general-view figure of a conventionally well-known image projection device. It is a typical block diagram of a conventionally well-known video projection device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image projector 2 Reflector 3 Light source 4 Light pipe 5 Lens 6 Liquid crystal display element 7 Projection lens part 8 Projection screen

Claims (12)

A light source unit that collects the emitted light, a light pipe that enters the collected light from an incident surface, guides the emitted light from the exit surface, and an electro-optic element that converts the emitted light into image light In a video projection device comprising a projection lens unit for projecting the video light,
The image projection apparatus, wherein the light pipe makes the condensed light incident on the incident surface at a position shifted from an optical axis of the light pipe.   The video projection apparatus according to claim 1, wherein an optical axis of the light source unit does not coincide with an optical axis of the light pipe, and substantially coincides with an optical axis of the electro-optical element.   The image projection apparatus according to claim 1, wherein an optical axis of the light source unit is parallel to an optical axis of the light pipe.   The irradiation light emitted from the light emission surface of the light pipe and applied to the electro-optic element has an asymmetric intensity distribution with respect to the optical axis of the electro-optic element. The video projection device according to claim 1.   Of the collected light incident at a position shifted from the optical axis of the light pipe on the incident surface, light incident at a maximum angle with respect to the optical axis of the light pipe is reflected an odd number of times in the light pipe. When the light pipe is emitted from the light exit surface, the intensity of the light emitted from the light pipe exit surface is opposite to the direction of the position deviated from the light pipe optical axis with respect to the light pipe optical axis. 5. The image projection device according to claim 1, wherein the image projection device is a maximum in the image projection.   When the upward projection field angle with respect to the optical axis of the projection lens unit is larger than the downward projection field angle, the light pipe transmits the condensed light on the incident surface to the optical axis of the light pipe. The image projection apparatus according to claim 5, wherein the light is incident at a position shifted downward.   Of the collected light incident at a position shifted from the optical axis of the light pipe on the incident surface, light incident at a maximum angle with respect to the optical axis of the light pipe is reflected even times in the light pipe. When the light pipe is emitted from the light exit surface, the intensity of the light emitted from the light pipe exit surface is in the same direction as the direction of the position shifted from the light pipe optical axis with respect to the light pipe optical axis. The video projection device according to claim 1, wherein the video projection device is maximum.   When the upward projection field angle with respect to the optical axis of the projection lens unit is larger than the downward projection field angle, the light pipe transmits the condensed light on the incident surface to the optical axis of the light pipe. The image projection apparatus according to claim 7, wherein the light is incident at a position shifted upward.   The video projection device according to claim 1, wherein the projection lens unit has a maximum projection angle of view of 45 ° or more with respect to an optical axis of the projection lens unit.   The video projection apparatus according to claim 1, further comprising a moving unit configured to move an incident position where the condensed light is incident on an optical axis of the light pipe.   The moving means is a moving means for moving the light pipe in a direction perpendicular to the optical axis of the light pipe, one end abutting against the light pipe or the holding means for holding the light pipe, and the other end being a fixed portion. The image projecting device according to claim 10, wherein the image projecting device is a position adjusting screw rotatably supported by the position adjusting screw.   The video projection apparatus according to claim 10, wherein the moving unit is an actuator that can move in a direction perpendicular to an optical axis of the light pipe.

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