JP2013097123A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image projection device capable of preventing lowering of illumination intensity and reducing illuminance unevenness.SOLUTION: An image projection device comprises: an illumination optical system comprising a light source including a reflector 11, an illuminance equalization element 4, relay lenses 5 and 6, first and second folding mirrors 7 and 8; a reflection type spatial optical modulation element 10 in which an image is formed by reclining each arranged mirror element and illumination light is radiated by the illumination optical system; and a projection optical system 20 that projects light reflected by the reflection type spatial light modulation element 10 on an image projection surface. The second folding mirror 8 includes a notch 81 to avoid mechanical overlapping of a lens barrel part of the projection optical system 20 and the second folding mirror 8. A light source unit 1 including the reflector 11 includes a position adjustment member so as to perform an illumination distribution adjustment for a part corresponding to the notch 81 in an illumination area of the reflection type spatial optical modulation element 10.

Description

  The present invention relates to an image display device that displays an image by projecting it on a screen, and is generally called a projector.

  Image display devices generally referred to as projectors include CRT projectors, liquid crystal projectors, DMD (Digital Micromirror Device) projectors, and the like, depending on image display elements. The DMD is a kind of reflection type spatial light modulation element, has a myriad of two-dimensionally arranged micromirrors, and changes the inclination angle of each micromirror to turn on / off the reflected light. It is a display element. The DMD forms an image by turning on and off according to a change in the tilt angle of each pixel. The light turned on by the DMD pixel is guided to the screen surface through the projection optical system, and the image formed by the DMD is enlarged by the projection optical system and projected onto the screen surface.

  The image display apparatus according to the present invention includes a reflective image display element such as the DMD as an image display element. As a well-known technique related to the configuration of the image display apparatus according to the present invention, which is an image display apparatus provided with a reflective image display element, techniques described in Patent Document 1 and Patent Document 2 described below There is.

  Patent Document 1 discloses a technique related to a single-plate projector using one DMD in FIG. In the illumination system of this projector, a plurality of mirrors are used for converging illumination light on the DMD reflecting surface and turning back the optical path. Among these mirrors, a mirror closest to the projection lens may be partially cut out depending on the shape of the projection lens so as not to mechanically overlap with a part of the projection lens constituting the projection optical system. Illumination light is partially lost due to this notch, so that the illuminance is partially reduced in the illuminance distribution on the DMD (see Patent Document 1, lower left portion of FIG. 10). Furthermore, the illuminance also decreases on the screen (see Patent Document 1, lower right part of FIG. 11). When such uneven illuminance occurs, the image quality deteriorates. This is because even if the brightness level of the input image data to be displayed is uniform on the entire screen, if there is uneven illuminance as described above, the center of the screen appears bright and appears dark at the lower right of the image. This is because a bright image may not be recognized. Patent Document 1 does not describe illuminance unevenness, and does not disclose countermeasures for eliminating illuminance unevenness.

  Patent Document 2 discloses a technique related to a projector having a lamp light source, a condenser lens, a first folding mirror, a second folding mirror, a DMD, and a projection lens. Such a projector described in Patent Document 2 is generally known as a projector configuration using a DMD as an image display element. Patent Document 2 includes a characteristic configuration of the present invention described later. There is no description about a certain light source and the position adjusting means of the accompanying lifter.

  As described above, Patent Document 1 and Patent Document 2 do not have an idea of providing a light source and a position adjusting means for a lifter associated therewith. For this reason, it is impossible to eliminate the illuminance reduction and uneven illuminance of the formed image due to the fact that the folding mirror has a notch, and there is a problem that the quality of the formed image is deteriorated.

  By the way, as one of the requests from users for recent image projection apparatuses, there is a reduction in size of the image projection apparatus mainly for the purpose of improving portability. Light source diodes (LEDs) or laser diodes (LDs) can be considered as examples of light sources that can be miniaturized, but these light sources are insufficient in brightness. Bright white light sources such as lamps are still mainstream. Since the ultra-high pressure mercury lamp or the like is larger than the LED or LD, it is a problem to reduce the size while using a lamp light source.

  In order to reduce the size of the image projection apparatus, it is effective to reduce the size of optical components included in the illumination system. This also leads to cost reduction. However, downsizing optical components often conflicts with obtaining desired optical properties. In an illumination system, for example, a light tunnel is often used as illumination uniformizing means. A light tunnel is made by bonding four plate-like mirrors using an adhesive with excellent heat resistance so that the mirror surfaces are inside each other and the cross-sectional shape is rectangular. The appearance is columnar. When illumination light is incident from one end of the light tunnel, the illumination light is reflected a plurality of times within the light tunnel corresponding to the incident angle, and illumination light having a substantially uniform illumination distribution is emitted from the other end of the light tunnel. .

Regarding the light tunnel, it is desired to achieve both miniaturization and obtaining desired optical characteristics. The longer the light tunnel, the better the illumination can be made uniform, and it becomes possible to form a high-quality image with little illuminance unevenness. However, as the light tunnel becomes longer, the illumination system becomes larger. If the light tunnel is shortened in order to reduce the size of the illumination system, the number of reflections in the light tunnel is reduced, resulting in insufficient uniformity of the illumination light. If the light tunnel is further shortened, it is not reflected at all in the light tunnel, and the ratio of emitted light increases, but the light intensity distribution becomes uneven with a peak near the center on the DMD. When the length of the light tunnel is long and the number of reflections is large, the illumination light becomes dark. This allows the reflectance at the reflecting surface as R, is the number of reflections When n, from the R ^n. Therefore, the length of the light tunnel is set in consideration of the length of the light tunnel, the uniformity of illumination, and the total reflectance.

  In the present invention, which will be described in detail later, the second folding mirror closest to the projection lens has a notch, so if any illuminance reduction prevention means and illuminance unevenness reduction means are not provided, the DMD and the screen Illuminance decreases at a position corresponding to the notch of the image formed above.

  The present invention has a white light source having a reflector, an illumination uniformizing element, a folding mirror, and a reflective spatial light modulation element, and solves the problems of the image projection apparatus caused by the notch of the folding mirror, It is an object of the present invention to provide an image projection device that can prevent a decrease in brightness and reduce illuminance unevenness.

  The present invention provides an illumination optical system having a light source having a reflector, an illumination uniformizing element, a relay lens, a first folding mirror, and a second folding mirror, and tilting each arrayed mirror pixel to form an image. An image projection apparatus comprising: a reflective spatial light modulator that is irradiated with illumination light by an illumination optical system; and a projection optical system that projects light reflected by the reflective spatial light modulator on an image projection surface. The second folding mirror has a notch for avoiding mechanical overlap between the lens barrel portion of the projection optical system and the second folding mirror, and the light source unit having the reflector includes the reflective spatial light. The most important feature is to have a position adjusting member for adjusting the illuminance distribution of the portion corresponding to the notch in the illumination area of the modulation element.

  The position of the light source having the reflector is adjusted by the position adjustment member, and the illuminance distribution adjustment in the illumination area is performed, thereby reducing the decrease in illuminance at the portion corresponding to the cutout of the second folding mirror and the entire projected image Can be reduced.

It is a perspective view which shows the Example of the image projection apparatus which concerns on this invention. It is a top view which shows typically the periphery of the light source unit in the said Example, and an illumination optical system. It is a top view which shows typically the aspect which the periphery of the said light source unit and the illumination optical system were moved for illumination intensity distribution adjustment. It is a top view which shows another example of the movement mechanism of the periphery of the said light source unit and illumination optical system for illumination distribution adjustment. It is a front view which shows another example of the moving mechanism for illumination intensity distribution adjustment. It is a front view which shows another example of the moving mechanism for illumination distribution adjustment. It is a front view which shows the operation | movement aspect of the said moving mechanism. It is a side view which shows the example of installation structure of the illumination uniformization element applicable to this invention. It is an optical arrangement | positioning figure which shows the outline | summary of the Example of the image projector concerning this invention. It is a top view which shows another example of the moving mechanism for illumination distribution adjustment. It is a front view which shows the operation | movement aspect of the said moving mechanism. It is a top view which shows another example of the moving mechanism for illumination distribution adjustment. It is a front view which shows the outline | summary of the Example of the image projection apparatus which concerns on this invention. It is a front view of the 2nd folding mirror in the example of the present invention. It is a schematic diagram which shows the dimensional relationship between a light source unit and an illumination uniformization element, and the relationship of the aspect ratio of an illumination uniformization element. It is a graph which shows the example of the illuminance distribution of a length direction, a width direction, and a diagonal direction about the spatial light modulation element in the Example of this invention. It is the schematic diagram and graph for demonstrating that illumination distribution changes with the length of an illumination uniformization element. It is a perspective view which shows the example of an external appearance of the illumination equalization element in the Example of this invention. It is a perspective view which shows another example of the illumination equalization element in the Example of this invention. The example of the attachment structure of an illumination equalization element is shown, (a) is a perspective view, (b) is a side view. The example of the spatial light modulation element in the Example of this invention is shown, (a) is a top view of the whole spatial light modulation element, (b) is a top view of a part of spatial light modulation element, (c) is FIG. 5D is a plan view of the micromirror, FIG. 5D is a side view of a part of the spatial light modulator, and FIG. 5E is a side view showing a difference in reflected light path between when the micromirror is on and when it is off. The light source unit in the Example of this invention is shown, (a) is a front view, (b) is a side view. The rotation color filter in the Example of this invention is shown, (a) is a front view, (b) is a side view. It is a top view which shows the example of arrangement | positioning of the explosion-proof glass with respect to the light source unit and the spatial light modulation element, and rotation color filter in the Example of this invention. It is a top view which shows the positional relationship of the illumination equalization element and the 1st, 2nd relay lens in the Example of this invention. It is an illuminance distribution figure which shows the result of having conducted simulation experiment about the illuminance distribution on a spatial light modulation element. It is an illuminance distribution map on the spatial light modulation element when the light source unit is shifted in one direction. It is an illuminance distribution figure on a spatial light modulation element at the time of shifting a light source unit in the reverse direction. It is an illuminance distribution map on the spatial light modulation element when the light source unit is rotated around an axis in one direction. FIG. 7 is an illuminance distribution diagram on the spatial light modulation element when the light source unit is rotated in the reverse direction about an axis in one direction. It is an illumination intensity distribution diagram for defining the position on a spatial light modulation element. It is a graph which plots and shows illumination intensity at equal intervals in the diagonal direction of a spatial light modulation element. It is a front view which shows another example of the moving mechanism for illumination distribution adjustment. It shows the positional relationship among the image projection device, the screen, and a person. (A) is a schematic diagram showing an example of an image projection device that projects at a very close distance, and (b) is a schematic diagram showing an example of a traditional image projection device. .

  Embodiments of an image projection apparatus according to the present invention will be described below with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes a light source unit, and the light source unit 1 includes a light source 12 shown in FIGS. 9, 15, and the like, and a reflector 11 that surrounds almost half of the light source 12. The light source 12 is a white light source. In front of the light source unit 1, that is, on the path of illumination light emitted from the light source unit, an explosion-proof glass 2, a rotating color filter 3, a light tunnel 4 that is an illumination uniformizing element, a first relay lens 5, and a second relay lens 6. The first folding mirror 7, the second folding mirror 8, the cover glass 110, the DMD 7, which is a reflective spatial light modulation element, the projection optical system 20, and the dust-proof glass 27 are arranged in this order. The light source unit 1 to the second folding mirror 8 constitute an illumination optical system that illuminates the minute mirror surface of the DMD 7.

  The projection optical system 20 is configured by arranging a refractive projection lens 21 using a lens, a plane mirror 25 as a folding mirror, and a free-form surface mirror 26 in this order in the light beam traveling direction. The projection optical system 20 projects the reflected light from the micromirrors of the DMD 7 onto the screen 70 shown in FIG. 9 and enlarges and displays the image formed by the DMD 7 on the screen 70.

  The first folding mirror 7 has a cylinder mirror, that is, a cylindrical reflecting surface. The second folding mirror 8 is spherical and has a notch 81 at one corner as shown in FIG. Each of the first and second folding mirrors 7 and 8 has a concave reflecting surface. In this embodiment, illumination light is emitted from the light source unit 1 in the horizontal direction, transmitted through the light tunnel 4, the first and second relay lenses 5, 6 in the horizontal direction, and the illumination light that has passed above the DMD 7 is the first. The first folding mirror 7 is installed obliquely upward so that it is reflected obliquely upward by the folding mirror 7. The second folding mirror 8 is installed obliquely downward so that the illumination light reflected by the first folding mirror 7 is reflected by the second folding mirror 8 toward the DMD 7. The DMD 7 has innumerable micromirrors corresponding to pixels as described above, and the micromirrors are arranged so as to be arranged on a horizontal plane so that the reflected light from the micromirrors turned on is directed upward in the vertical direction. . The second folding mirror 8 is disposed at a position deviated from the path of the light beam upward in the vertical direction.

  The projection lens 21 is disposed in the path of light reflected by the micromirrors turned on as described above and directed upward in the vertical direction. As will be described in detail later, the reflected light from the micromirror that is turned off deviates from the optical path of the projection lens 21 and does not enter the projection optical system 20. Since one corner of the second folding mirror 8 is at a position that mechanically overlaps with the outer periphery of the lower end of the barrel of the projection lens 21, the notch 81 is formed at one corner of the second folding mirror 8 in order to avoid this overlapping. Is formed.

  The dustproof glass 27 is provided to prevent dust and dust from entering the projection optical system 20, the illumination optical system, and the DMD 10 from above. In addition, a cover glass 110 for making the DMD 10 almost the same is disposed immediately above the DMD 10.

  The free-form surface mirror 26 projects an image spatially modulated by the DMD 10 obliquely upward toward a screen at a close distance of the image projection apparatus, and forms an image on the screen. In the illumination optical system of the present embodiment, the exit end of the light tunnel 4 and the minute mirror surface of the DMD 10 are conjugated with each other by the first and second relay lenses 5 and 6 and the first and second folding mirrors 7 and 8. is there.

  The horizontal direction in which the illumination light is emitted from the light source unit 1 is the z direction, the horizontal direction that is orthogonal to the z direction is the x direction, and the direction that is orthogonal to the z direction and the plane including the x direction is the y direction. To do. The micromirror surfaces of the DMD 10 are arranged in a plane including the z direction and the x direction, and the light emitted from the light source unit 1 and reflected by the micromirror surface of the DMD 10 travels upward in the y direction. Yes.

  2 and 3 schematically show an illumination optical system including the light source unit 1 in the above embodiment. 2 and 3, the light source unit 1 and the explosion-proof glass 2 are incorporated in a light source unit case 16. The light source unit case 16 is disposed in the light source casing 15 and is abutted against the inner wall surface of the light source casing 15 by a leaf spring 17. The leaf springs 17 are arranged at two locations, and one leaf spring 17 presses one side surface of the light source unit case 16 against the inner surface of one side wall of the light source housing 15, and the other one leaf spring 17 attaches the light source unit case 16 to the light source housing. It is pressed toward the front of the body 15. A wedge 18, which is a kind of spacer, is interposed as a tilt adjusting member of the light source unit 1 between the one side front end of the light source unit case 16 and the inner surface of the front wall of the light source housing 15.

  Each optical element outside the light source housing 15 includes a color wheel 3, a light tunnel 4, a first relay lens 5, a second relay lens 6, a first folding mirror 7, a second folding mirror 8, a DMD 10, and a projection optical system 20. Are arranged in the order. From the light tunnel 4 to the lower part of the projection lens 21 that constitutes a part of the projection optical system 20 is disposed in an optical system housing 40 that is integrally formed of resin or the like. The rotating color filter 3 is disposed between the light source housing 15 and the optical system housing 40.

  As shown in FIG. 13, the light source casing 15, the optical system casing 40, and the rotating color filter 3 are installed in a housing 60 that is integrally formed of resin or the like. By providing the light source housing 15 separately from the optical system housing 40 of the illumination system as in the illustrated example, the generated heat can be reduced from being transmitted to the optical system housing 40 side. However, it is not essential to provide the light source housing 15 and the optical system housing 40 separately, and it is sufficient that the light source housing 15 and the optical system housing 40 are accommodated in the same housing 60.

  2 and 3, the reflector 11 has an elliptical cross-sectional shape, for example, and a white light source 12 made of, for example, an ultra-high pressure mercury lamp is disposed on the rotation axis O thereof. Illumination light emitted from the light source 12 is reflected by an elliptical reflecting surface formed of a concave surface of the reflector 11, so that illumination light centered on the rotation axis O is emitted along the rotation axis O.

  As described above, at one corner of the second folding mirror 8, there is a notch 81 for avoiding mechanical overlap between the lens barrel portion of the projection lens 21 constituting the projection optical system 20 and the second folding mirror 8. Is formed. For this reason, the illuminance of the illumination light applied to the DMD 10 decreases at a portion corresponding to the notch 81, and uneven illuminance occurs. Therefore, a position adjusting member for the light source unit 1 is provided to reduce the illuminance reduction and the illuminance unevenness due to the notch 81. The wedge 18 is one of the position adjusting members.

  In the embodiment shown in FIG. 2, due to the elasticity of the two leaf springs 17, one side surface of the light source unit case 16 is on the inner surface of one side wall of the light source housing 15, and the front surface of the light source unit case 16 is on the inner surface of the front wall of the light source housing 15. It is pressed. In this aspect, the wedge 18 does not function, and the central axis of the illumination light of the light source unit 1 substantially coincides with the optical axes of the first and second relay lenses 5 and 6.

  The mode shown in FIG. 3 is a mode when a wedge 18 as an inclination adjusting member of the light source unit 1 is inserted while being slid between one side front end of the light source unit case 16 and the front wall inner surface of the light source housing 15. is there. By inserting the wedge 18, the light source unit case 16 tilts against the elasticity of the two leaf springs 17, the light source unit 1 tilts together with the light source unit case 16, and the rotation axis O of the lifter 11 that is the central axis of the illumination light also tilts. . In this way, the inclination of the light source 12 can be easily adjusted.

  The spacer as the adjustment member is not limited to the wedge 18 and may be an adjustment member 181 formed of a flat spacer as shown in FIGS. When the flat adjustment member 181 is inserted between the front end of one side of the light source unit case 16 and the inner surface of the front wall of the light source housing 15 as in the examples shown in FIGS. It tilts while moving against the elasticity of the two leaf springs 17. The light source unit 1 moves and tilts together with the light source unit case 16. The amount of movement and inclination of the light source unit 1 can be adjusted by changing the thickness of the adjusting member 181 or by changing the number of overlapping adjusting members 181. In the example shown in FIGS. 2 to 5, the direction in which the adjusting members 18 and 181 are moved while sliding is the x direction.

  In FIG. 5, the optical system casing 40 is made of a lightweight and strong metal, such as magnesium, for example, and is manufactured by a casting method. The optical system housing 40 is formed with grooves, holes, or openings for installing individual optical elements. Specifically, a groove 45 for installing the first relay lens 5 and a groove 46 for installing the second relay lens 6 are formed. The light tunnel 4 has a rectangular cross section, and a step 47 corresponding to the length and width of one side is formed in the academic housing 40. Further, the academic housing 40 is formed with a rectangular opening 41 for installing the DMD 10 and a circular opening 42 for installing the lens barrel of the projection lens 21.

  The first and second folding mirrors 7 and 8 are installed in a mirror housing 48. The mirror housing 48 is a separate member from the optical system housing 40 and is installed in the optical system housing 40. The mirror housing 48 is made of metal or resin, or a composite of metal and resin. In the example shown in FIGS. 2 to 13, only the projection lens 21 of the projection optical system 20 is installed in the optical system housing 40, but the flat mirror 25 constituting the projection optical system 20, and further a free-form surface You may install in the optical system housing | casing 40 including the mirror 26. FIG. The light source unit 1 has an explosion-proof glass 2.

  A rotating color filter 3 is disposed between the light source unit 1 and the optical system housing 40. The shaft of the drive motor 31 is coupled to the rotation center of the rotary color filter 3, and the rotary color filter 3 is rotated by the motor 31. As shown in FIGS. 2 to 7, the illumination light emitted from the light source 12 and reflected by the reflector 11 passes through the rotating color filter 3 and is collected at the incident end of the light tunnel 4. In general, it is desirable to collect light at the center of the incident end face of the light tunnel 4 (in the plane including the x direction and the y direction). However, in the present invention, it may be preferable to shift in the x direction and further in the y direction. The explosion-proof glass 2 and the color wheel 3 are installed with an inclination of several degrees to about 10 ° in order to reflect the illumination light and prevent return light to the light source 12.

  In the example shown in FIGS. 2 to 5, the tilt adjustment of the light source unit 1 is performed by rotating around the axis in the y direction. However, as shown in FIGS. 6 and 7, the axis in the x direction is set as the center. Adjustments can also be made by rotating. In the example shown in FIGS. 6 and 7, a wedge 18 as an adjustment member is interposed between the front upper end of the light source unit case 16 and the front wall front of the light source housing 15. By adjusting the insertion amount of the wedge 18, the inclination of the light source unit 1 in the light source unit case 16 can be adjusted.

  Further, since the second folding mirror 8 has the notch 81 at one corner, the light tunnel 4 is arranged around its central axis so that there is no decrease in illuminance at the portion corresponding to the notch 81 in the illumination area of the DMD 10. It is installed in a mode rotated (tilted). FIG. 8 is a view of the light tunnel 4 as seen from the light source side. The step 47 for installing the light tunnel 1 is formed to be inclined, and the light tunnel 4 is installed at the same angle as the inclination angle of the step 47 by installing the light tunnel 4 at the step 47. .

  As illustrated in FIGS. 10 and 11, the light source tilt adjusting member may be a screw 50. The screw 50 is screwed into the front wall of the light source housing 15 from the outer front surface, and the tip of the screw 50 penetrates the front wall and abuts the front surface near the upper end of the light source housing 15 and near one end. By adjusting the screwing amount of the screw 50 with respect to the front wall of the light source housing 15, the inclination of the light source unit case 16 and the light source unit 1 integrated with the light source housing 15 around the axis in the x direction is continuously adjusted. Can be adjusted.

  Since the light source unit 1, the rotating color filter 3, the light tunnel 4 constituting the illumination optical system, and the like are closely arranged, there may be no space necessary for turning the screw 50. Therefore, as shown in FIG. 12, a long lever 51 may be formed integrally with the head of the screw 50, and the screw 50 may be rotated by operating the lever 51. When the light source tilt adjusting member is constituted by the screw 50 as in the example shown in FIGS. 10 to 12, the light source tilt adjusting member can be continuously adjusted by the amount of rotation of the screw and fine adjustment can be performed. Is possible. Further, if the screw 50 is adjusted for every fixed angle, stepwise adjustment is possible.

  By the way, when the image projection apparatus is classified by appearance, there are a vertical type and a horizontal type, and an optical element is arranged corresponding to each. The embodiment described so far is a vertical type. As represented in FIG. 9, a light source unit 1 including an explosion-proof glass 2 in a housing 60 of an image projection apparatus, a rotating color filter 3 that forms at least red, green, and blue light from white illumination light in a time-sharing manner. A light tunnel 4 as an illumination uniformizing element, first and second relay lenses 5 and 6, first and second folding mirrors 7 and 8, a DMD 10 as a spatial light modulation element, a projection lens 21, and a projection mirror system 22. Is arranged. The projection mirror system 22 includes a plane mirror 25 and a free-form surface mirror 26 shown in FIG. Although not shown, a cooling fan, a light source driving unit, a DMD driving unit, holding members for various optical elements, and the like are arranged in the housing 60. The section from the light source unit 1 to the second folding mirror 8 is called an illumination optical system. Further, the projection optical system is configured by combining the projection lens 12 to the free-form surface mirror 12. Although omitted in FIG. 9, each element of the illumination optical system is installed in the light source housing 15 and the optical system housing 40 as described above.

  White illumination light emitted from the light source 12 travels forward while being collected by the reflector 11. Of the white illumination light, ultraviolet rays (UV) and infrared rays (IR) are cut by a UV cut filter and an IR cut filter provided on the explosion-proof glass 2. Further, the white illumination light is time-divided into three colors, for example, red (R), green (G), and blue (B) by the rotating color filter 3. These lights are reflected many times in the light tunnel 4, and the spatial intensity distribution is made uniform. The reflecting surface of the reflector 11 is represented by, for example, a concave ellipsoid, and the light source (light emitting unit) 12 is installed at the first focus, and the entrance (incident end) of the light tunnel 4 is installed at the second focus position. . Accordingly, the light emitted from the light source 12 is once condensed at the incident end of the light tunnel 4.

  The light exiting the light tunnel 4 passes through the first relay lens 7 and the second relay lens 8, is folded back by the first folding mirror 7, is further folded by the second folding mirror 8, and reaches the DMD 10. The power of the first and second relay lenses 5 and 6 and the second folding mirror 8 is distributed so that a conjugate relationship is established between the emission end face of the light tunnel 4 and the display face of the DMD 10. The optical path of the illumination light is three-dimensionally folded by the first and second folding mirrors 7 and 8, thereby reducing the size of the housing 60. In addition, as described with reference to FIG. 8, the light tunnel 4 is installed in an inclined posture that rotates around the optical axis. The illumination light is three-dimensionally provided by the first and second folding mirrors 7 and 8. This is because it is configured to be folded back.

  The orthogonal coordinate system of x, y, z is as described above. In the lower right of FIG. 9, rotations about the x-axis, y-axis, and z-axis are indicated as α, β, and γ, respectively. This is common in other figures.

  In FIG. 9, the image display surface of the DMD 10 is parallel to a surface including the z axis and the x axis. The projection lens 21 is installed so that its optical axis is along the y-axis direction, and is perpendicular to the image display surface of the DMD 10. The screen 70 on which the image is projected is parallel to the yz plane. Therefore, the image display surface of the DMD 10 and the screen 70 are orthogonal to each other. The optical axis of the projection lens 21 and the screen 70 are parallel to each other, and the screen 70 is parallel to a plane including the y direction and the z direction perpendicular to the floor. In addition, the surface of a flat table such as a floor or a desk in a room where the image projection apparatus is installed is parallel to a plane including the z direction and the x direction. The image projection apparatus according to the present embodiment having such a relationship is referred to as a vertical type. In the conventional horizontal image projection apparatus, the optical axis of the projection lens is parallel to the x-axis, and there is a screen perpendicular to this (see, for example, Patent Document 2). The technical idea according to the present invention is not limited to the vertical type, but can be applied to a horizontal type image projection apparatus.

  The second folding mirror 8 is shown in FIG. The second folding mirror 8 has a notch 81 at one corner and can be manufactured by compression molding using a mold including the notch 81. Moreover, you may form by cutting.

  As shown in FIG. 15, the maximum angle of illumination light emitted from the light source unit 1 including the light source 12 and the reflector 11 is 2θ. The cross section of the light tunnel 4 is rectangular, the length of the short side of the inner surface in the cross section is a, the length of the long side is b, the length of the diagonal is 2c, the length of the light tunnel 4 along the optical axis ( L) is L. If the distance along the optical axis until the light incident on the light tunnel 4 at the half of the maximum angle is reflected in the light tunnel 4 for the first time is s, s = c * tan θ. As an example, L = 25 mm, θ = 30 °, a = 3.4 mm, and b = 5.7 mm. Further, c = 3.32 mm and s = 5.75 mm. Further, L / s represents the number of reflections of the illumination light with the maximum incident angle in the light tunnel, and is 4.35.

When the angle θ of the illumination light is smaller than 30 °, the number of reflections in the light tunnel decreases. If L is 30 mm, 20 mm, or 15 mm and the other is the same, L / s is 5.22, 3.48, 2.61 respectively. Assuming that the one-time reflectance of the reflecting surface of the light tunnel 4 is 98% (average), the total reflectance is 90.0% at L = 30 mm and 91.6% at L = 25 mm depending on the number of reflections. L = 20 mm and 93.2%, and L = 15 mm and 94.8%. The greater the L, the greater the number of reflections and the lower the total reflectivity. The smaller the L, the less the number of reflections and the total reflectivity. As a single optical element, the total reflectance is preferably 90% or more. Also, it is not preferable that the number of reflections is too small from the viewpoint of uniform illumination light. Therefore,
3.48 s ≦ L ≦ 5.22 s
Is desirable.

  When the DMD 10 is appropriately illuminated without large illuminance unevenness, the illuminance distribution on the DMD 10 becomes substantially flat. FIG. 16 shows the illuminance distribution on the DMD 10. In FIG. 16, the curve (A) shows the illuminance distribution in the short side direction of the DMD 10, the curve (B) shows the illuminance distribution in the long side direction of the DMD 10, and the curve (C) shows the illuminance distribution in the diagonal direction of the DMD 10. The illuminance distribution on the DMD 10 depends on the number of reflections of light in the light tunnel 4. When the number of reflections is small and the illumination is not sufficiently uniform, the upper portion does not become a flat curve, and the distribution is not uniform with a sharp center.

  The decrease in illuminance on the DMD 4 caused by the notch 81 of the second folding mirror 8 can be improved and recovered by adjusting the position of the light source unit 1. The reason will be described with reference to FIG. FIGS. 17A to 17C depict the positional relationship between the light source unit 1 and the light tunnel 4. (A) shows a case where the light tunnel 4 is sufficiently long and there is no influence of the notch 81 of the second folding mirror 8, and the illuminance distribution (diagonal) on the DMD 10 is shown in the graph (i). To be uniform. However, when there is an influence of the notch 81, the illuminance distribution has a reduced illuminance on one side as shown in the graph (ii).

  FIG. 17B shows a case where the light tunnel 4 is short. When the light tunnel 4 is short, the ratio of the illumination light emitted from the light source unit 1 without being reflected in the light tunnel 4 increases, and a peak occurs at the center in the illuminance distribution curve on the DMD 10. . Furthermore, one side of the illuminance distribution curve is lowered due to the influence of the notch 81 of the second folding mirror 8. The graph in this case is shown in (iii). In this case, when the central axis of the illumination light is tilted by the adjustment member of the light source unit 1 as shown in FIGS. 2 to 7, the peak at the center of the illuminance distribution curve on the DMD 10 moves. Therefore, if the central axis of the illumination light is tilted in a direction that cancels the illuminance reduced by the notch 81 of the second folding mirror 8, the reduction in illuminance is recovered and improved as shown in the graph (vi) of FIG. Can be made.

  According to the embodiment of the present invention, even when the illumination on the DMD 10 is reduced by the notch 81 of the second folding mirror 8 and the short light tunnel 4 is used, the light source unit 1 having the lifter 11 is provided. By the position adjusting means, it is possible to obtain an image projection apparatus with little illuminance unevenness.

Next, each component of the above embodiment will be described in more detail.
As shown in FIG. 18, the light tunnel 4 as an illumination uniformizing element is composed of four plate-like mirrors bonded together so that the mirror surfaces are inside each other and the cross-sectional shape is rectangular. It is columnar. Each mirror is bonded using an adhesive having excellent heat resistance. As described above, the longer the length of the light tunnel 4, the more the number of reflections on the inner surface, and the illuminance distribution of the illumination light can be made uniform, but the balance between the uniformity of the illuminance distribution and the size of the illumination system Thus, the length of the light tunnel is set to about 20 mm to 30 mm.

  As DMD10, a 0.65 inch WXGA (16:10) pixel pitch of 10.8 μm was used. The inner dimension of the light tunnel 4 corresponding to this is about 6 mm × 3 mm. The reflectivity of each mirror constituting the light tunnel 4 is preferably 98% (wavelength 420 nm to 680 nm) or more. The reflection surface of the mirror is formed by depositing a metal film such as Ag or Al on the glass surface by vacuum deposition or sputtering. A dielectric multilayer film may be formed instead of the metal film. The thickness of each mirror plate is around 1 mm. The illumination uniformizing element having such a configuration is also called a light tunnel, a light pipe, a rod lens, a rod integrator, or the like.

  The illumination uniformizing element may not be a laminate of mirror plates as shown in FIG. 18, and may be, for example, a glass column. When a glass column is used as the illumination uniformizing element, the illumination light can be reflected using total reflection on the inner surface of the glass column, so that it is not necessary to form a reflective film.

  Illumination light emitted from the light source 12, reflected by the reflector 11, and emitted from the light source unit 1 has a light distribution, and when projected onto the screen as it is, illuminance (brightness) unevenness is recognized by humans. Is done. In general, uneven illumination is often bright in the central area of the screen but dark in the periphery. Irradiance unevenness can be reduced by the light tunnel 4 as an illumination uniformizing element. The principle is the same as that of a kaleidoscope. Light incident on the illumination uniforming means at an appropriate angle is repeatedly reflected several times by the mirror on the inner surface of the light tunnel 4 so as to fold the light, and the illuminance is made uniform at the exit end of the light tunnel 4. .

  The installation and adjustment structure of the light tunnel 4 will be described. In FIG. 20, the light tunnel 4 is installed at a step 47 of the optical system housing 40 by a fixture 49 corresponding to the shape of the light tunnel 4. There is a vertical wall surface following the step 47, and the light tunnel 4 is disposed at a corner portion constituted by the step 47 and the vertical wall surface, and an angle-shaped fixture 49 having two surfaces orthogonal to each other. The light tunnel 4 is fixed by pressing the light tunnel 4 to each corner.

  The light tunnel 4 may be put in a holder 44 as shown in FIG. The material of the holder 44 is, for example, stainless steel and preferably has heat resistance. The cooling effect can be enhanced by bringing the inner surface of the holder 44 into contact with the outer surface of the light tunnel 4. The light tunnel 4 is fixed directly or the holder 44 holding the light tunnel 4 is fixed to a step 47 of the optical system housing 40 by a fixture 49 as shown in FIG. The fixture 49 is made of a metal having high thermal conductivity such as stainless steel or aluminum, and is screwed to the optical system housing 40.

  As shown in FIG. 20B, a leaf spring 52 that is an elastic member is interposed between the light tunnel 4 and the fixture 49. A screw hole is formed on the optical system housing 40 side, and an adjusting screw 53 is screwed into the screw hole. The adjustment screw 53 is screwed in from the two directions of the bottom surface side and one side surface side of the light tunnel 4, and the tip of each adjustment screw 53 is in contact with the bottom surface side and one side surface side of the light tunnel 4. The leaf springs 52 are respectively interposed on the opposite sides of the two adjusting screws 53 with the light tunnel 4 interposed therebetween. Thus, both the adjusting screw 53 and the leaf spring 52 are provided in two directions to constitute a position adjusting structure capable of adjusting the position of the light tunnel 4 in the x-axis direction and the y-axis direction, and the adjusting screw 53 is an adjusting member. It has become.

  By turning at least one adjusting screw 53, the light tunnel 4 is pushed in a direction to bias the leaf spring 52 on the opposite side of the adjusting screw 53. Further, when the adjustment screw 53 is turned to the opposite side, the light tunnel 4 is pushed by the elasticity of the leaf spring 52 on the opposite side and moves in the opposite direction. The leaf spring 52 may simply be interposed between the fixture 49 and the light tunnel 4, or may be provided integrally with the fixture 49. The position where the adjustment screw 53 is provided may be provided on either the incident side or the emission side of the light tunnel 4 or may be provided on both of them. If the inclination in the length direction of the light tunnel 4 is adjusted, it may be provided on either the incident side or the emission side, and the position adjustment (for example, parallel movement (shift) of the light tunnel 4 or the like) may be performed. For example, it is provided on both the incident side and the emission side.

  Spatial light modulation elements are roughly classified into a transmission type and a reflection type. In addition, there is a liquid crystal spatial light modulator using liquid crystal and polarized light, and a DMD having a micro mirror array and switching each of the micro mirrors to on light and off light. In the above embodiment, DMD is used. DMD uses non-polarized light.

  FIG. 21 schematically shows the DMD 10. FIG. 21A shows the DMD 10 as viewed from above. The image display area is rectangular, and innumerable micromirrors 102 are arranged as pixels in this image display area as shown in FIG. Each micromirror 102 is a square having a side of about 10 μm. The number of micromirrors is 1280 × 768 pixels (or pixels) for XGA and 1280 × 768 pixels for WXAGA. The array surface of the micromirrors is a DMD display surface, that is, an image display region.

  The size of the image display is a diagonal line of the image display area of the DMD 10 and is determined to be 0.5 inch or 0.65 inch, for example. Further, the ratio of the long side to the short side of the rectangular image display area is taken to express the aspect ratio of the screen as 4: 3, 16:10. The micromirrors 102 constituting each pixel are square, and the arrangement period of the micromirrors 102 is referred to as a pixel pitch. The pixel pitch is around 10 μm. Although not shown in the drawing, the actual size of the micromirror 102 is slightly smaller than the pixel pitch. The ratio of the actual size of the micromirror 102 to the pixel pitch is called the aperture ratio.

  FIG. 21D shows a case where the pixel array of the DMD 10 is viewed from the side. A protective cover glass 110 is placed on the upper side of the pixel array. Each square micromirror 102 rotates with its diagonal line as a rotation axis (see FIG. 21C). The direction of rotation of each micromirror 102 is both clockwise and counterclockwise with respect to the rotation axis, and the direction of rotation is distinguished between plus and minus. The rotation angle is ± 10 ° to 12 °. The rotation of the micro mirror 102 is sometimes referred to as tilt. As shown in FIG. 21E, the rotated micromirror 102 can change the direction of the reflected light with respect to the incident light by rotating in the plus direction and rotating in the minus direction. As a result, binary values of ON and OFF can be taken.

  Each micro mirror 102 is turned on when the rotation angle is + 12 °, and is turned off when the rotation angle is −12 °. When the micromirror is on, the light reflected by the micromirror contributes to the image formation. When the micromirror is off, the light reflected by the micromirror does not contribute to the image formation and displays black. When the light is on, the light reflected by the micromirror can enter the entrance pupil of the projection lens 21 and reaches the screen 70 via the projection lens 21. On the other hand, when the light is off, the light reflected by the micro mirror cannot enter the entrance pupil of the projection lens 21 and reaches the off light processing absorbing member provided in the vicinity of the DMD 10. This absorbing member requires cooling. Also, there is a moment when the micromirror takes a flat posture between the on and off states. A heat sink and a cooling fan are installed on the side opposite to the display surface of the DMD to cool the DMD.

  As the white light source 12, a tube-shaped high pressure or ultra high pressure mercury lamp may be used. Alternatively, a halogen lamp may be used. The shape of the reflector 11 of the light source unit 1 is preferably an ellipsoid. A tube (light emitting unit) is installed at one of the two focal points of the ellipsoid, and the incident end of the illumination uniformizing element is installed at the other focal point. As the light source 12, a light source having an output of, for example, about 180 W to 260 W (watts) is used. The higher the lamp output, the brighter the projected image.

  The mercury lamp may burst, and the explosion-proof glass 2 is installed on the front surface of the reflector 11 so that the glass piece does not scatter even if it bursts. The explosion-proof glass 2 is made of borosilicate glass having, for example, a 40 mm square and a thickness of about 3 mm, and is installed at an angle of, for example, 10 ° with respect to the optical axis of the light source unit 1. This is because the light reflected by the explosion-proof glass 2 becomes return light and is not focused at the position of the tube. Such return light shortens the lamp life. The explosion-proof glass 2 is provided with a multilayer film of an infrared (IR) cut filter and an ultraviolet (UV) cut filter. The reflector 11 is housed in an appropriate housing, and the housing may be covered with a fine metal mesh for explosion prevention. A lamp as a light source in an image projection apparatus is a consumable item, and its brightness is reduced by long-term use such as several thousand hours. At that time, the lamp housing or the light source unit is replaced.

  A light source 12 and a reflector 11 made of a tube are shown in FIG. 22A is a front view, and FIG. 22B is a side view. The shape of the lifter 11 includes an ellipse or a hyperbola. All have a rotation axis. Further, a tube as a light source 12 is installed on the rotation axis.

  The light source 12 emits a wide range of light from ultraviolet light to visible light and infrared light, and is therefore a white light source. Among these, ultraviolet rays and infrared rays are cut immediately after the emission of the lamp as described above, and the remaining light in the visible light region is separated into color components by the rotating color filter 3, and in particular, R, G, B which are the three primary colors of light. A color image is formed using monochromatic light.

  The rotating color filter 3 is color separation means. As shown in FIG. 23, the rotating color filter 3 divides a disk into a plurality of regions in a rotational direction like a pie chart, and each region has a different color (see FIG. 23A). Specifically, a multilayer film is deposited on the surface of a circular glass plate to form a color filter. Basically, they are red (R), green (G), and blue (B), and white (W) is added to this to divide the region into four. The white (W) region is provided for increasing the brightness, and is a transparent region where a multilayer film is not formed. In order to improve color reproducibility, yellow (Y), magenta (M), cyan (C), etc. may be added.

  A necessary spectrum is extracted from the illumination light emitted from the white light source 12 by the rotating color filter 3. The glass disk forming the base of the rotating color filter 3 has a diameter of about 40 mm and a thickness of about 1 mm, for example. Each color filter area is physically separated. The rotation center of the disk is attached to the rotation output shaft of the motor 31 and is driven to rotate at high speed by the motor 31. The rotation speed is about several thousand rpm to about 10,000 rpm. A sensor for detecting positional information of each color of the rotating color filter 3 is provided, and the image display by the DMD 10 is synchronized with the output of this sensor. Therefore, the rotating color filter 3 generates each color by time division (field sequential). Since the response speed of the micromirror of the DMD 10 is high, a color image can be formed without any problem by field sequential. Further, a light spot 32 (see FIG. 23A) that is being collected from the light source unit 1 always hits the same position of the rotating color filter 3.

  FIG. 24 shows the arrangement from the light source unit 1 to the light tunnel 4 that is an illumination uniformizing element. An explosion-proof glass 2 is disposed immediately before the light source unit 1, and a rotating color filter 3 is subsequently disposed. As described above, the explosion-proof glass 2 and the rotating color filter 3 are arranged to be tilted from several degrees to about 10 ° with respect to the y-axis. The angle of illumination light emitted from the light source 12 and collected by the reflector 11, that is, the illumination angle is about 60 °. As shown in FIG. 18, the rotation axis of the lift reflector 11 is parallel to the z axis, and on this axis, there are an axis passing through the center of the light source 12 and the light tunnel 4 made of a tube.

  FIG. 25 schematically shows the positional relationship between the light tunnel 4 and the first and second relay lenses 5 and 6. In FIG. 25, the first and second relay lenses 5 and 6 are different from the light tunnel 4 in the z axis, that is, in the optical axis direction of the illumination light, but the coordinates of the x axis and the y axis are the same. Therefore, the first and second relay lenses 5 and 6 and the light tunnel 4 are coaxial. However, the first and second relay lenses 5 and 6 are shifted with respect to the axis passing through the center of the light tunnel 4, and the optical axes of the first and second relay lenses 5 and 6 and the central axis of the light tunnel 4 are shifted from each other. . The first and second relay lenses 5 and 6 are preferably manufactured by polishing if they are spherical lenses, or by press molding if they are aspherical lenses.

Tables 1 and 2 show the position coordinates and detailed numerical values of the optical components constituting the illumination system from the light tunnel 4 to the DMD 10.
Table 1

Table 2

  As an example of the projection optical system 20, the position coordinates of the constituent lenses and other optical elements are shown in Table 3, and detailed numerical values of the projection system lens are shown in Tables 4, 5 and 6. The coordinates shown in Table 3 are for a case where an image having a diagonal length of 43 inches is projected on the screen.

Table 3

Table 4

Table 5

Table 6

Table 7 shows details of the shape of the free-form surface mirror 26 that is one of the constituent members of the projection optical system.
Table 7

The shape of some aspheric lenses shown in Tables 4 to 6 follows Formula 1.
Formula 1

The surface shape of the free-form surface mirror 26 in Table 7 follows Formula 2.
Formula 2

  Regarding the installation of the light tunnel 4, a simulation experiment was performed by using ray tracing calculation software LightTools (ORA: Optical Research Associates). The illuminance distribution on the DMD 10 when the position and tilt of the light source unit 1 were adjusted was obtained. The pitch of one pixel of the DMD 10 is assumed to be 10.8 μm and a diagonal length of 0.65 inches WXGA.

  FIG. 26 shows the result of a simulation experiment performed on the illuminance distribution on the DMD with the configuration shown in FIG. 1 and Tables 1 to 7. FIG. 26 shows an experiment without shifting and rotating the light source unit, and this is the median value. Next, the illuminance distribution on the DMD was obtained when the light source unit was shifted +0.3 mm in the x direction. The result is shown in FIG. Furthermore, the illuminance distribution on the DMD when the light source unit was shifted by -0.3 mm in the y direction was obtained. The result is shown in FIG. Further, the illuminance distribution on the DMD when the light source unit was rotated by −0.5 ° in the α direction was obtained. The result is shown in FIG. Further, the illuminance distribution on the DMD when the light source unit was rotated by −0.5 ° in the β direction was obtained. The result is shown in FIG. In the case of FIGS. 29 and 30, the center of rotation is set at the center of the incident end of the light tunnel 4. Referring to FIGS. 26 to 30, it can be seen that the illuminance distribution changes in any case.

  As shown in FIG. 31, FIG. 32 shows a plot of illuminance at equal intervals in the diagonal direction, with the center being “0” and the lower left being “24” to represent the position on the DMD. In FIG. 32, the illuminance is normalized, and the reference is the maximum value in the entire illuminance distribution. When the position of the light source unit is adjusted, it can be seen that the median illuminance is increased at all positions 24. However, as can be seen from FIGS. 28 and 29, when the light source unit is shifted by -0.3 mm in the y direction or rotated by -0.5 ° in the α direction, the illuminance decreases at the upper right of the DMD. Therefore, the image quality is not good. Therefore, the direction of the position adjustment of the light source unit is desirably shifted by −0.3 mm in the x direction or rotated by −0.5 ° in the β direction, as shown in FIGS. As is clear from FIG. 32, the rotation in the α direction and the β direction has a higher effect of reducing the illuminance reduction and the illuminance unevenness than the shift in the x direction and the y direction.

  In each of the embodiments described so far, the adjustment member that adjusts the illuminance distribution mainly adjusts the inclination angle of the light source unit. In some embodiments, the light source unit can be shifted, that is, translated. It was like that. Here, if it is only necessary to adjust the illuminance distribution by shifting the light source unit in the x direction or the y direction, the adjustment member can be configured as in the example shown in FIG. That is, the leaf spring 17 is interposed between the upper surface of the light source unit case 16 and the light source housing 15 and between the back surface of the light source unit case 16 and the light source housing 15, so that the bottom surface of the light source unit case 16 and the light source housing 15 are disposed. A flat plate-shaped adjustment member 54 is interposed therebetween. The position of the light source unit case 16 together with the light source unit 1 can be shifted in the y direction by changing the thickness of the adjustment member 54 or changing the number of the adjustment members 54 to be stacked.

  In FIG. 31, the normalized illuminance at the position 24 at the median is approximately 0.75. On the other hand, when the position of the light source unit is adjusted, it becomes 0.78 to 0.81. Therefore, the illuminance at this position is preferably about 0.75 or more with respect to the maximum value of the entire illuminance distribution, and less than about 0.25 when the illuminance is reduced.

  As described above, image projection apparatuses are classified into a vertical type and a horizontal type according to appearance. The present invention is applicable to both vertical and horizontal types. The illustrated embodiment has an image projection apparatus main body, and has a reflection type screen independently of the image projection apparatus main body, and is configured as a front projection type image projection apparatus that projects an image from the front of the screen. A person views an image on the screen from the same side where the image projection apparatus is installed with respect to the screen position. The traditional front projection type image projection apparatus has a positional relationship of image projection apparatus-human-screen, and requires a certain distance for projection between the image projection apparatus main body and the screen. This is one of the restrictions when installing the image projection apparatus. As shown in FIG. 34 (b), when the traditional image projection apparatus 300 is used in a lecture or the like, a person 75 may enter between the image projection apparatus 300 and the screen 70. Shadows are visible and the shadowed image cannot be seen. The speaker has the difficulty of feeling uncomfortable when the light from the light source enters the eyes.

  On the other hand, in recent years, projection from a close range has become possible due to the shortening and widening of the projection lens. FIG. 34A shows the arrangement relationship of such an image projection apparatus. In this case, the positional relationship between the person 75 and the image projection apparatus 100 or 200 and the screen 70 becomes possible, and even if the person 75 approaches the screen 70, the shadow of the person 75 is not easily included in the projected image, and thus it is difficult for the lecturer to see the eyes. Projection light is difficult to enter, and you will never feel unpleasant.

  Further, as in the above-described embodiment, by using a configuration in which the light emitted from the projection lens 21 is projected onto the screen using the free-form surface mirror 26, an image projection apparatus capable of projecting from a closer distance can be obtained. . Projection using such an image projection apparatus is called ultra-short distance projection. When the light emitted from the projection lens 21 is simply folded back by a plane mirror, problems such as trapezoidal distortion occur in the image from the projection lens 21 except for a specific angle. Accordingly, the trapezoidal distortion is eliminated by using a free-form surface mirror 26. The projection lens 21 and the free-form surface mirror 26 are combined, and in the embodiment, the plane mirror 25 is also referred to as a projection optical system. In FIG. 34A, reference numeral 100 denotes an image projection apparatus capable of projecting at a very close distance in which trapezoidal distortion is eliminated by using the free-form surface mirror 26 as in the illustrated embodiment. Reference numeral 200 represents an image projection apparatus capable of projecting at a very close distance without the free-form surface mirror 26.

  There is a throw ratio as an index indicating the degree of projection from a close range. This is the diagonal size of the projected image divided by the distance from the image projection device to the screen. The larger this value is, the greater the degree that it can be projected onto a larger screen from a closer distance.

  In the case of close-distance projection, as shown in FIG. 34A, the positional relationship of person-image projection apparatus-screen is established. At this time, if the image projection apparatus is installed at the center height of the screen 70 as indicated by the reference numeral 200, the image projection apparatus main body overlaps the screen 70 as viewed from the audience, thereby hindering image observation. Accordingly, the installation position of the image projection apparatus at a close distance is below the screen 70 as indicated by reference numeral 100. For example, it may be placed on the floor 72. In this case, since the projection is performed obliquely below the screen 70, the incident angle of the light beam is different between the lower end (floor side) and the upper end (ceiling side) of the screen 70, and the incident angle is larger at the upper end. Therefore, the ratio of the light entering the upper end of the screen is reflected in the direction of the ceiling 71 and the ratio of the light toward the viewer is reduced. This is a dark image at the upper end of the screen 70. Such a problem does not occur in the image projection apparatus of the traditional projection system as shown in FIG.

  In the vertical image projection apparatus capable of projecting at a close range, the projection optical system 20 including the free-form curved mirror 26 is used. Therefore, unlike the normal horizontal image projection apparatus, the deformation of the projected image area due to specific distortion is performed. In addition, there is a problem of uneven illumination such that the upper part of the screen 70 is dark and the lower part is bright. If the illuminance is reduced due to the presence of the notch in the folding mirror in the illumination optical system, the image quality further deteriorates. On the other hand, when the light source position adjusting member is provided as in the embodiment of the present invention, it is effective for reducing uneven illuminance and reducing illuminance.

DESCRIPTION OF SYMBOLS 1 Light source unit 2 Explosion-proof glass 3 Rotating color filter 4 Illumination equalization element (light tunnel)
5 First Relay Lens 6 Second Relay Lens 7 First Folding Mirror 8 Second Folding Mirror 10 Spatial Light Modulation Element (DMD)
DESCRIPTION OF SYMBOLS 11 Reflector 12 Light source 15 Light source housing 16 Light source unit case 17 Elastic body (leaf spring)
18 Tilt adjustment member (wedge)
DESCRIPTION OF SYMBOLS 20 Projection optical system 21 Projection lens 22 Projection mirror system 25 Plane mirror 26 Free-form surface mirror 40 Optical system housing 48 Mirror housing 50 Tilt adjusting screw 60 Housing 70 Screen 81 Notch

JP 2004-138668 A JP 2000-098272 A

Claims (9)

An illumination optical system having a light source having a reflector, an illumination uniformizing element, a relay lens, a first folding mirror, and a second folding mirror, and forming an image by tilting each arrayed mirror pixel, An image projection apparatus comprising: a reflective spatial light modulator that is irradiated with illumination light; and a projection optical system that projects light reflected by the reflective spatial light modulator onto an image projection surface,
The second folding mirror has a notch for avoiding mechanical overlap between the lens barrel portion of the projection optical system and the second folding mirror,
The light source unit having the reflector includes a position adjusting member for adjusting an illuminance distribution of a portion corresponding to the notch in the illumination area of the reflective spatial light modulator.   The image projection apparatus according to claim 1, wherein the adjustment member adjusts an inclination of a central axis of illumination light by the reflector.   3. The image projection apparatus according to claim 1, wherein the adjustment member is a spacer.   The image projection apparatus according to claim 1, wherein the adjustment member is a screw. 5. The image projection apparatus according to claim 1, wherein the illumination uniformizing element has a rectangular column shape with a rectangular cross-section, and is 1 of a maximum illumination angle of light emitted from a light source having the reflector. When / 2 is θ, 1/2 of the length of the diagonal of the rectangle is c, and c / tan θ is s, that is, s = c / tan θ, the total length L of the illumination uniformizing element is
3.48 s ≦ L ≦ 5.22 s
An image projection apparatus characterized by   6. The image projection device according to claim 1, wherein a portion of the illuminance distribution caused by the cutout of the second folding mirror with respect to the maximum illuminance value in the entire illuminance distribution on the reflective spatial light modulator. An image projecting apparatus characterized in that a typical decrease is less than 25%.   7. The image projection apparatus according to claim 1, wherein the light source is a white light source, and generates at least three colors of red, green, and blue in time division from illumination light emitted from the white light source. An image projection apparatus comprising:   8. The image projecting apparatus according to claim 1, further comprising a position adjusting member for an illumination uniformizing element in addition to the position adjusting member for the light source unit.   9. The image projection apparatus according to claim 1, wherein the projection optical system includes a projection lens and a free-form curved mirror, thereby enabling a close range projection.

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