JP2013061375A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device having high light utilization efficiency of an illumination optical system and capable of vertical placement.SOLUTION: An image display device includes: a light source; a light collector; a light mixing element; a color filter; a reflection type image display element; an illumination optical system composed of a first relay lens, a second relay lens, a first holding mirror and a second holding mirror; and a projection optical system which projects light reflected from fine mirrors in an on-state out of a plurality of fine mirrors constituting the reflection type image display element. An angle formed by a display surface of the reflection type image display element and the projected surface is substantially orthogonal, and the first relay lens is tilted with respect to an optical axis formed by the light source and the light mixing element.

Description

  The present invention relates to an image display apparatus that enlarges an image and displays it on a screen, and more particularly, to an image display apparatus that has a high light utilization efficiency of an illumination optical system and that can be placed vertically.

  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 reflective image display element that has a plurality of micromirrors arranged two-dimensionally, and forms a projected image by turning on and off reflected light by changing the tilt angle of each micromirror. is there. 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 known technique related to the image display apparatus according to the present invention, which is an image display apparatus provided with a reflective image display element, there are techniques described in Patent Document 1 and Patent Document 2 described below.

  Patent Document 1 has an illumination optical system composed of a lamp light source, a color filter, a condenser lens, a plane mirror, a spherical mirror, and a DMD which is a reflective image display element, and an optical axis of the lamp light source according to this illumination optical system. An image display device is described in which the optical axis of the condenser lens is coaxial or parallel and is not decentered.

  The image display device described in Patent Literature 2 also has substantially the same configuration as the image display device of Patent Literature 1, and light from the illumination optical system is projected onto a projection surface (for example, a screen) via the projection optical system. The image forming surface of the DMD and the projection surface are in a parallel relationship.

  The above-described conventionally known image display apparatuses are generally used by installing the apparatus main body at a predetermined height such as a desk. An image is projected and displayed on the projection surface parallel to the indoor side wall from the installation location. The height of the installation location of the apparatus is as high as the projected image is as high as the viewer's field of view or slightly lower. At this time, the optical axis of the projection optical system of the image display apparatus is substantially perpendicular to the projection surface.

  In the general usage mode as described above, the normal line of the image forming surface of the reflective image display element provided in the image display device is parallel to the optical axis of the projection lens. Accordingly, the image forming surface of the reflective image display element is parallel to the projection surface.

  Further, the image display device may be tilted in order to adjust the position of the projected image on the projection surface. In this case, the optical axis of the projection lens has a slight inclination with respect to the normal line of the projection surface. The angle formed by the normal of the projection surface formed by this inclination (the normal when the normal direction of the projection surface is used as a reference) and the optical axis of the projection lens is an acute angle. In this specification, an image display device in which the above positional relationship is established between the optical axis of the projection lens and the projection surface is referred to as a “horizontal projector”.

  The horizontal projector as described above needs to provide a certain distance between the image display device main body and the projection surface in order to ensure the size of the display image. This is one of the restrictions on the installation of the projection type image display device.

  Moreover, since it becomes difficult to see an image if it is too far from the projection surface, a person viewing the image tries to be as close to the projection surface as possible. For this reason, in the horizontal projector as described above, there may be a person who sees an image between the installation location and the projection surface. That is, since there is a “person” that can be an obstacle on the optical path of the projection light, the projection light is obstructed by the “person's shadow” and the image may be difficult to see. In addition, when used in a lecture or the like, the speaker is in a state of facing the image display device, and thus is dazzled by the projected light.

  In order to solve these problems, in recent years, an image display device has been developed that can project an image from a very short distance by shortening and widening a projection lens. If the distance between the image display device and the projection surface can be reduced, the projection light is not obstructed by the human shadow as described above, and the speaker does not feel dazzling.

  In recent years, an image display apparatus has been developed that employs an “ultra-close-up projection method” that can display a large image on a projection surface at a closer distance. The image display apparatus of a very close distance projection system reflects light emitted from a projection lens by a free-form surface mirror and projects an image onto a projection surface. The reason why the free-form surface mirror is used instead of the plane mirror is that when the light emitted from the projection lens is reflected by the plane mirror, trapezoidal distortion or the like occurs in the projected image except for a specific angle. The projection lens and the free-form surface mirror are collectively referred to as a projection optical system.

  One index indicating the performance of the image display device is “Throw Ratio” indicating the degree of projection from a close range. The slow ratio is a value obtained by dividing the diagonal size of the projected image by the distance from the image display device to the projection surface. Therefore, an image display device having a smaller slow ratio can project an image of a predetermined size even when the distance to the projection surface is short.

  Here, the usage mode of the image display apparatus capable of ultra-short distance projection will be described with reference to FIG. As shown in FIG. 24, since the distance between the projector 100 that is an image display device capable of ultra-short distance projection and the screen 200 that is the projection surface is very close, the observer 300 is located on the back side of the projector 100. It will be. At this time, if the installation surface of the projector 100 is a position A, the main body of the projector 100 enters the field of view of the observer 300 and becomes an obstacle. Therefore, the installation position of the projector 100 is desirably a position below the screen, as indicated by a position B in FIG. For example, the projector 100 may be placed directly on the floor.

  When an image is projected on the screen 200 close to and above the projector 100 on the floor, the incident angle of the projection light to the lower end (floor side) of the screen 200 and the incidence of the projection light to the upper end (ceiling side) of the screen 200 The corners are greatly different. That is, the incident angle to the upper end of the screen 200 is large, and the incident angle to the lower end of the screen 200 is small. The light projected on the upper end of the screen 200 having a large incident angle increases in the ratio of being reflected toward the ceiling, and the ratio of the light toward the viewer 300 is reduced, so that the image on the upper side of the screen 200 becomes dark.

  That is, in the image display apparatus of the very close distance projection method, brightness unevenness may occur in the image on the projection surface. In other words, the image display apparatus of the very close range projection system has a problem of improving the light use efficiency in an optical system for projecting an image, particularly in an illumination optical system.

  In order to improve the light utilization efficiency in the illumination optical system, the positional relationship between the optical axis of the projection lens and the normal line of the reflective image display element is important. This is because if the optical axis of the projection lens is tilted with respect to the normal line of the reflective image display element, there is a problem that only one side of the projection image becomes blurred. Therefore, it is necessary to carefully arrange and position the reflective image display element and the projection lens.

  Further, in order to improve the light utilization efficiency of light from the illumination optical system, the projection lens needs to be firmly fixed so that the optical axis of the projection lens does not shift. The projection lens is configured by combining a plurality of lenses. The plurality of lenses are housed in a lens barrel and fixed to a predetermined positional relationship of the image display device. When fixing the lens barrel to the housing of the image display device, it is necessary to adjust the lens barrel so that it does not tilt.

  Even if the image display device is used for a long time, the lens barrel and the projection lens inside the lens barrel are affected by external factors such as impact and vibration, and internal factors such as the weight of each member including the lens barrel. It is necessary to prevent the optical axis from tilting. As described above, in order to improve the light use efficiency in the illumination optical system of the image display device, accuracy in the assembly process of the image display device and robustness against long-term use of the lens barrel including the projection lens are required.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image display apparatus that can be placed vertically by improving the light utilization efficiency of an illumination optical system.

  The present invention relates to an image display device, and relates to a light source, a light collector for collecting light emitted from the light source, a light mixing element having an incident end near the light collector, a light collector, and a light. A color filter that is arranged between the mixing elements and superimposes color elements on the light incident on the light mixing element in a time-sharing manner and a plurality of two-dimensionally arranged micro mirrors, and the inclination of each micro mirror A reflective image display element that turns on and off the emission of reflected light by changing the angle between an on state and an off state, and a first disposed between the emission end of the optical mixing element and the reflective image display element. An illumination optical system including a relay lens, a second relay lens, a first folding mirror, and a second folding mirror, and a minute mirror in an on state among a plurality of minute mirrors constituting a reflective image display element A projection optical system that projects the reflected light onto the projection surface, the angle formed by the display surface of the reflective image display element and the projection surface is substantially orthogonal, and the first relay lens is the light source And tilting with respect to the optical axis formed by the optical mixing element.

  ADVANTAGE OF THE INVENTION According to this invention, the light utilization efficiency of an illumination system is high, for example, a vertical type image display apparatus with stable illumination system and projection lens installation can be obtained.

It is a schematic diagram which shows the example of a structure of the image display apparatus which concerns on this invention. It is (a) top view which shows the example of the reflection type image display element with which the said image display apparatus is equipped, (b) Partial enlargement, (c) Side view, (d) Reflection state figure of projection light. It is (a) front view and (b) side view which show the example of the light source with which the said image display apparatus is equipped, and a lamp reflector. It is a perspective view which shows the example of the illumination equalization element with which the said image display apparatus is provided. It is a top view which shows the example of the installation state of the said illumination equalization element. It is a top view which shows the example of the color wheel with which the said image display apparatus is provided. It is a schematic diagram which shows the example of the illumination optical system with which the said image display apparatus is provided. It is a schematic diagram which shows the example of the illumination optical system with which the said image display apparatus is provided. It is the side view which compared the installation aspect of the said image display apparatus and the conventional image display apparatus. It is a top view which shows the example of the usage condition of the image display apparatus which concerns on this invention. It is a top view which shows another example of the usage condition of the said image display apparatus. (A) which shows the example of the fixing method of the projection lens of the said image display apparatus is a side view, (b) is a front view. It is the schematic which shows another example of the illumination optical system with which the said image display apparatus is provided. It is a schematic diagram which shows the example of the holding method of the relay lens which comprises the illumination optical system with which the said image display apparatus is provided. It is a schematic diagram which shows another example of the holding method of the relay lens which comprises the illumination optical system with which the said image display apparatus is equipped. It is a schematic diagram which shows another example of the holding method of the relay lens which comprises the illumination optical system with which the said image display apparatus is provided. It is a graph shown about the example of the relationship between the 4th-order aspherical coefficient of the 1st relay lens with which the said image display apparatus is provided, and light utilization efficiency. It is a graph shown about the example of the relationship between the 4th-order aspherical coefficient of the 2nd relay lens with which the said image display apparatus is provided, and light utilization efficiency. It is a graph shown about the example of the relationship between the 4th-order aspherical coefficient of the 2nd folding mirror with which the said image display apparatus is provided, and light utilization efficiency. It is a graph shown about the example of the relationship between the 6th-order aspherical coefficient of the 2nd folding mirror with which the said image display apparatus is provided, and light utilization efficiency. It is a schematic diagram which shows the example of the projection optical system with which the image display apparatus which concerns on this invention is provided. It is a contour map which shows an example of the light quantity distribution in the reflection type image display element with which the said image display apparatus is provided. It is a contour map which shows an example of light quantity distribution in the to-be-projected surface of the projection light radiate | emitted from the projection optical system with which the said image display apparatus is provided. It is explanatory drawing which shows the example of the installation aspect of the image display apparatus in which a very close distance projection is possible.

  Embodiments of an image display apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a vertical projector that is an example of an image display device according to the present invention. Reference numeral 1 denotes a vertical projector body (hereinafter referred to as “projector 1”), and reference numeral 14 denotes a screen as an example of a projection surface. In the following description, it is assumed that one direction in the horizontal plane is the x axis, one direction in the horizontal plane orthogonal to the z axis is the z axis, and the vertical axis orthogonal to both the x axis and the z axis is the y axis. Further, the rotation around the x axis is expressed as α, the rotation around the y axis as β, and the rotation around the z axis as γ.

  In FIG. 1, a projector 1 includes a light source 2 that is a white light source, a lamp reflector 3 that collects light emitted from the light source 2, an explosion-proof glass 4 that prevents scattering of the light source 2, and red light from the light source 2. A color wheel 5 that is a rotating color filter that converts green and blue light in a time-sharing manner, and an illumination uniformizing element 6 that is an optical mixing element that makes the light quantity distribution of the light collected by the lamp reflector 3 uniform. A first relay lens 7, a second relay lens 8, a first folding mirror 9, a second folding mirror 10, a DMD 11 that is a reflective image display element, a projection lens 12, and a free-form surface mirror 13. , Has.

  The projector 1 includes a cooling fan, a lamp driving unit, a DMD driving unit, a holding unit for various optical elements, and the like in addition to those illustrated in FIG. Here, the light source 2 to the second folding mirror 10 are referred to as an illumination optical system. The projection lens 12 and the free-form surface mirror 13 are collectively referred to as a projection optical system.

  White light emitted from the light source 2 is collected by the lamp reflector 3. The lamp reflector 3 has an outer shape of an ellipsoid, the light source 2 is disposed at a position corresponding to the first focal point of the ellipsoid, and the entrance (incident incident) of the illumination uniformizing element 6 at a position corresponding to the second focal point. End) is arranged. Accordingly, the light emitted from the light source 2 is collected at the incident end of the illumination uniform element 6.

  An explosion-proof glass 4 and a color wheel 5 are disposed between the light source 2 and the illumination uniformizing element 6. Of the white light emitted from the light source 2, ultraviolet rays (UV) and infrared rays (IR) are blocked by a UV cut filter and an IR cut filter provided on the explosion-proof glass 4. The light that has passed through the explosion-proof glass 4 is converted by the color wheel 5 into light of three colors, for example, red (R), green (G), and blue (B), in a time-sharing process. The light on which these color elements are superimposed is incident on the illumination uniformizing element 6 and is reflected a number of times inside the light uniformizing element 6 to be a light having a uniform spatial intensity distribution.

The light that has passed through the illumination uniformizing element 6 passes through the first relay lens 7 and the second relay lens 8, is reflected by the first folding mirror 9 and the second folding mirror 10, and reaches the DMD 11.
The illumination light that has passed through the second relay lens 8 passes above the DMD 11 and is reflected obliquely upward by the first folding mirror 9 that is installed at an angle. The reflected light is further obliquely lowered by the second folding mirror 10. Reflected toward DMD 11.

  The power arrangement of the first relay lens 7, the second relay lens 8, and the second folding mirror 10 is adjusted so that the exit end face of the illumination uniformizing element 6 and the image forming surface of the DMD 11 have a conjugate relationship. As described above, the projector 1 according to the present embodiment reduces the entire size by folding the optical path three-dimensionally.

  The DMD 11 is a reflective image display element composed of a minute mirror array, and is an element in which square mirrors with sides of around 10 μm are arranged. The resolution of the projected image is determined by the number of micromirrors arranged in the DMD 11. For example, if the resolution of the projected image is set to XGA, the DMD 11 in which minute mirrors corresponding to 1024 × 768 pixels (or pixels) are arranged is used. In addition, if the resolution of the projected image is WXAGA, the DMD 11 in which a minute mirror corresponding to 1280 × 768 pixels (or pixels) is arranged is used. XGA is an abbreviation for “Extended Graphics Array”. WXGA is an abbreviation for “Wide XGA”.

  The micromirror included in the DMD 11 has a configuration that can rotate around a square diagonal line as a rotation axis. The rotation angle of the micromirror is ± 10 ° to ± 12 °. For example, the light reflected by the mirror when the micromirror is rotated by + 12 ° is set to “ON light” to contribute to image formation, and the micromirror is rotated by −12 °. The light reflected by the light is “OFF light” and does not contribute to image formation and is configured to display black. That is, each optical element is arranged so that “ON light” by the DMD 11 travels upward and enters the projection lens 12 through the side of the second folding mirror 10.

  That is, when the light is ON, the light reflected by the micromirror of the DMD 11 enters the entrance pupil of the projection lens 12, is reflected by the free-form surface mirror 13 through the projection lens 12, and reaches the screen 14. On the other hand, in the case of OFF light, the light reflected by the micromirror of the DMD 11 cannot enter the entrance pupil of the projection lens 12, and is an OFF light processing absorbing member (not shown) provided near the DMD 11. ). In this way, by controlling the rotation of the micro mirror of the DMD 11, it is possible to project the projection light necessary for the display image onto the screen 14 via the projection optical system.

  Here, the DMD 11 will be described. FIG. 2 is a diagram showing an outline of the DMD 11. 2A is a plan view of the DMD 11 as viewed from above, FIG. 2B is a partially enlarged view of the image display area of the DMD 11, FIG. 2C is a side view of the DMD 11, and FIG. FIG. 6 is a diagram illustrating a state of reflection of image projection light in DMD 11.

  As shown in FIG. 2A, the appearance of the DMD 11 is rectangular, and includes an image display area 110 formed by arranging a plurality of micromirrors. An enlarged view of a part of the image display area 110 is shown in FIG.

  As shown in FIG. 2B, when the partial image display area 110a is enlarged, a plurality of micromirrors 110 are arranged. The micromirror 110 is square, and corresponds to one pixel of an image displayed by one micromirror 110 by projection light. The arrangement period of the micromirrors 110 is referred to as a pixel pitch P. The pixel pitch P is, for example, about 10 μm. The display size of the projected image is determined by the length of the diagonal line of the image display area 110.

  In FIG. 2B, the micromirrors 110 are shown as being arranged without a gap, but the actual size of the micromirrors is slightly smaller than the pixel pitch P. The actual mirror size with respect to the pixel pitch P is referred to as the aperture ratio. Each micromirror 110 can rotate about its diagonal line as a rotation axis. The rotation direction of the micromirror 110 is positive with respect to the rotation axis and negative with respect to the counterclockwise direction. The rotation angle is ± 10 ° to ± 12 °.

  A protective glass 112 is disposed on the upper surface side of the DMD 11 as shown in FIG. This protective glass 112 is for preventing dust and the like from adhering to the surface of the micromirror 110.

  As shown in FIG. 2D, the micro mirror 111 can rotate clockwise and counterclockwise with the diagonal line as the rotation axis. Since the micromirror 111a rotates in the clockwise direction, the reflected light becomes ON light and travels toward the entrance pupil of a projection lens (not shown). Since the micromirror 111b rotates counterclockwise, the reflected light is turned off and does not go to the entrance pupil of the projection lens (not shown) but goes to the absorbing member.

  Next, the light source 2 and the lamp reflector 3 will be described. The light source 2 is preferably a tube-shaped high-pressure mercury lamp. Moreover, a halogen lamp may be used. The lamp reflector 3 is an ellipsoid, and the light source 2 is installed at one of the two focal points of the ellipse, and the incident end of the illumination uniformizing element 6 is installed at the other focal point. For example, the output of the light source 2 is about 180 W to 260 W (watts). The higher the output of the light source 2, the brighter the projected image can be obtained.

  When a mercury lamp is used as the light source 2, it may burst. An explosion-proof glass 4 is installed on the front surface of the lamp reflector 3 so that the glass pieces do not scatter inside even if the light source 2 is ruptured. The explosion-proof glass 4 is, for example, a borosilicate glass having a 40 mm square and a thickness of around 3 mm, and is installed at an angle of 10 ° with respect to the optical axis of the light source 2. The reason why the explosion-proof glass 4 is installed to be inclined with respect to the optical axis of the light source 2 is to prevent the light reflected by the explosion-proof glass 4 from being returned light and focusing at the position of the light source 2. This is because the life of the light source 2 is shortened when such return light is present.

  The explosion-proof glass 4 is provided with a multilayer film of an infrared (IR) cut filter and an ultraviolet (UV) cut filter. The lamp reflector 3 is housed in a housing, and the housing may be covered with a fine metal mesh for explosion prevention. Since the light source 2 is a consumable item in the projector 1, the brightness is reduced when the usage time exceeds several thousand hours. When the light source 2 needs to be replaced, the lamp housing (unit) including the light source 2 is replaced.

  In FIG. 3, the outline of the light source 2 and the lamp reflector 3 is shown. FIG. 3A is a front view of the lamp housing 30 including the light source 2 and the lamp reflector 3, and FIG. 3B is a side view of the lamp housing 30.

  The light source 2 emits light in a wide range from ultraviolet rays to visible rays and infrared rays. Of the emitted light, the ultraviolet rays and infrared rays are cut by the explosion-proof glass 4 immediately after being emitted from the light source 2, and the rest. The light in the visible light region is colored by the color wheel 5.

  Next, the illumination uniformizing element 6 will be described. FIG. 4 is a perspective view showing an outline of the illumination uniform element 6. As shown in FIG. 4, the illumination uniformizing element 6 is formed by bonding four plate-like mirrors so that the mirror surface faces inward.

  Each mirror which comprises the illumination uniformization element 6 is bonded together using the adhesive agent etc. excellent in heat resistance. The longer the illumination uniformizing element 6 is, the more the number of reflections on the inner surface is, and the light distribution of incident light can be made uniform. However, if the illumination uniformizing element 6 is lengthened, the entire illumination optical system becomes large, which affects the size of the housing of the projector 1. Therefore, the degree of uniformity and the size of the illumination optical system are in a trade-off relationship. The length of the illumination uniformizing element 6 according to the present invention is 20 mm to 30 mm, and 25 mm is optimal.

  Assume that the DMD 11 has a diagonal size of 0.65 inches and a pixel pitch P of 10.8 μm. The inner dimension of the illumination uniformizing element 6 at this time is about 6 mm × 3 mm. The reflectance of the mirror used for the illumination uniformizing element 6 is preferably 98% (wavelength 420 nm to 680 nm) or more.

  In addition, the mirror used for the illumination uniformizing element 6 is formed by forming a metal film such as Ag or Al on the glass surface by vacuum deposition or the like. In this case, a dielectric multilayer film may be used instead of the metal film. The thickness of each plate constituting the illumination uniformizing element 6 is around 1 mm. The illumination uniformizing element 6 is also called a light tunnel, a light pipe, a rod lens, a rod integrator, or the like.

  The illumination uniformizing element 6 may be a thing other than the one in which the mirror plate is laminated, for example, a glass column. In this case, since the total reflection of the inner surface of the glass column is used, it is not necessary to produce a reflective film.

  The light emitted from the light source 2 and collected by the lamp reflector 3 has a light distribution. Therefore, if the projection is performed on the screen 14 as it is, unevenness in brightness occurs. For example, the image in the center area of the screen 14 is bright and the surrounding images are dark. The illumination uniformizing element 6 is a member used to prevent such brightness unevenness, and its principle is the same as that of the kaleidoscope. Light incident on the illumination uniformizing element 6 at an appropriate angle is repeatedly reflected by an inner surface mirror a plurality of times, and is superimposed so as to fold the light.

  The optical elements constituting the illumination optical system of the projector 1 according to the present embodiment are three-dimensionally arranged as shown in FIG. For this reason, the illumination uniformizing element 6 is arranged so as to rotate with respect to the optical axis. Here, the rotation of the illumination uniformizing element 6 will be described. FIG. 5 is a plan view of the illumination uniformizing element 6 viewed from the z-axis direction, and illustrates a state where γ is −11.42 °.

  Next, the color wheel 5 provided in the projector 1 according to the present embodiment will be described with reference to FIG. FIG. 6A is a plan view of the color wheel 5 viewed from the z-axis direction. FIG. 6B is a plan view of the color wheel 5 viewed from the x-axis direction. As shown in FIG. 6A, the color hole 5 is formed by dividing the disc 51 into a plurality of regions like a pie chart and coloring different colors by depositing different multilayer films in the respective regions. The colors of the color wheel 5 are basically red (R), green (G), and blue (B), but white (W) may be added as shown in FIG. . White (W) is a region where a multilayer film is not formed. The reason why white (W) is provided on the color wheel 5 is to increase the brightness. Further, yellow (Y), magenta (M), cyan (C), or the like may be added to the color wheel 5 in order to improve color reproducibility.

  The color wheel 5 is a color separation unit that separates a necessary spectrum from the light emitted from the light source 2. The disc 51 constituting the color wheel 5 is a glass having a diameter of about 40 mm and a thickness of about 1 mm provided with filters of each color. Each color region is physically separated.

  Further, as shown in FIG. 6B, the color wheel 5 is configured such that the rotation shaft of the motor 52 is coupled to the center of rotation of the disk 51 and rotates at a high speed. The rotation speed is from several thousand rpm (round per minute) to around 10,000 rpm. The color wheel 5 is provided with a sensor (not shown) and has a configuration capable of grasping position information of each color. A display image can be formed by synchronizing the rotation control of the sensor and the DMD 11.

  Therefore, the color wheel 5 generates each color by time division (field sequential). Since the response speed of the micromirror 110 included in the DMD 11 is high, there is no problem even if a color image is formed in a field sequential manner. Moreover, the light (spot) in the middle of being condensed by the lamp reflector 3 is configured to always hit the same position. In FIG. 6A, reference numeral 53 indicates the light spot.

  Next, the first folding mirror 9 and the second folding mirror 10 that form the illumination optical system of the projector 1 according to the present embodiment will be described. The first folding mirror 9 is a plane mirror, and the second folding mirror 10 is a concave mirror. The radius of curvature of the second folding mirror 10 is −75 mm. Further, the first folding mirror 9 is tilted three-dimensionally. For example, α has a tilt of −35.45 °, β has a tilt of −2.17 °, and γ has a tilt of 18 °. The second folding mirror 10 is also tilted three-dimensionally. For example, α has a tilt of 94 ° and β has a tilt of 17.64.

  Next, the configuration of the illumination optical system included in the image display apparatus according to the present invention will be further described. FIG. 7 is a schematic diagram showing a part of the illumination optical system provided in the projector 1, and shows the arrangement from the light source 2 to the illumination uniformizing element 6. As already described, the lamp reflector 3 is an ellipsoid, and the light source 2 is installed at a position corresponding to the first focal point, and the incident end of the illumination uniformizing element 6 is installed at a position corresponding to the second focal point. . Between the light source 2 and the incident end of the illumination uniformizing element 6, an explosion-proof glass 4 and a color wheel 5 are installed.

  The explosion-proof glass 4 and the color wheel 5 are arranged in a tilted state with respect to the y-axis. This tilt can prevent the light reflected from the front and back surfaces of the explosion-proof glass 4 and the color wheel 5 from returning to the light source 2. The tilt of the explosion-proof glass 4 and the color wheel 5 is about several degrees to 10 degrees. The angle of light emitted from the light source 2 and collected by the lamp reflector 3 (illumination angle S) is about 60 °. In FIG. 7, the optical axes formed by the light source 2, the lamp reflector 3, and the illumination uniformizing element 6 are aligned in the z-axis direction.

  Next, in the configuration of the illumination optical system included in the projector 1 according to the present embodiment, the relationship between the illumination uniformizing element 6, the first relay lens, and the second relay lens will be described. FIG. 8 is a schematic diagram showing the arrangement of the illumination uniformizing element 6, the first relay lens 7 and the second relay lens 8. In FIG. 8, the first relay lens 7 and the second relay lens 8 have different positions in the z-axis (optical axis) direction, but the coordinates in the x-axis direction and the y-axis direction are the same. It is therefore coaxial. The z-axis optical axis B of the first relay lens 7 and the second relay lens 8 is shifted with respect to the z-axis optical axis A of the illumination uniformizing element 6.

  When the shift amounts of the first relay lens 7 and the second relay lens 8 are expressed as Δx · Δy with respect to the illumination uniformizing element 6, for example, Δx is −1.469 mm and Δy is −1.370 mm.

  In order to brighten the image projected on the screen 14 with the light emitted from the projector 1, it is necessary to improve the light utilization efficiency of the illumination optical system. Here, the light use efficiency of the illumination optical system is defined. The light use efficiency is represented by the ratio of light reaching the projection lens (its entrance pupil) out of the light emitted from the illumination uniformizing element 6. Therefore, the light reaching the projection lens (its entrance pupil) when the light emitted from the illumination uniformizing element 6 is taken as 100% may be expressed as a percentage.

  The estimation of the light use efficiency can be performed by a simulation experiment using a ray tracing calculation software. The number of light rays reaching the entrance pupil of the projection lens is calculated with a constant number of light rays emitted from the exit end of the illumination uniformizing element 6. Thereby, the light use efficiency can be calculated.

  As already described, the light reaching the image forming surface of the DMD 11 is folded three-dimensionally by the first folding mirror 9 and the second folding mirror 10 constituting the illumination optical system. In such an illumination optical system, in order to efficiently irradiate light to the DMD 11, it is preferable to tilt the first relay lens 7 and the second relay lens 8 rather than coaxially.

  Therefore, in the projector 1 according to the present embodiment, the optical axes of the first relay lens 7 and the second relay lens 8 are tilted eccentrically with respect to the optical axis formed by the light source 2 and the illumination uniformizing element 6. . Table 1 shows values of light utilization efficiency when the first relay lens 7 is tilted decentered with respect to the x-axis and the y-axis.

(Table 1)

  As shown in Table 1, when the first relay lens 7 is tilted by 1 ° or β by −1 °, the light utilization efficiency is higher than the light utilization efficiency when the first relay lens 7 is not tilted. improves. Further, in the state where α is tilted by 1 ° and β is tilted by −1 °, the light utilization efficiency is higher than when α and β are tilted alone.

Returning to FIG. The image forming surface of the DMD 11 is parallel to the zx plane. The optical axis of the projection lens 12 is parallel to the y axis and is perpendicular to the image forming surface of the DMD 11. The screen 14 is parallel to the yz plane, and the image forming surface of the DMD 11 and the screen 14 are orthogonal to each other.
Further, since the optical axis of the projection lens 12 and the display surface of the screen 14 are parallel, the place where the projector 1 is installed is a place that is parallel to the zx plane. Then, the optical axis of the projection light of the projector 1 and the screen 14 that is the projection surface are in a parallel relationship. An image display device having such a positional relationship is called a vertical projector. In the conventional horizontal projector, the optical axis of the projection lens and the screen are in a vertical relationship.

  Here, a difference in distance between a conventional horizontal projector and a screen due to a difference in installation mode of the vertical projector according to the present invention will be described with reference to FIG. FIG. 9A is a plan view showing an example in which the installation state of the conventional projector 100 is viewed from the side. FIG. 9B is a diagram illustrating an example in which the installation state of the projector 1 (vertical type) according to the present embodiment is viewed from the side.

  As shown in FIG. 9A, the distance from the rear end of the housing of the projector 100 to the image projection surface of the screen 14 is D1. Further, as shown in FIG. 9B, the distance from the rear end of the housing of the projector 1 to the image projection surface of the screen 14 is D2. When D1 and D2 are compared, D1> D2. In other words, the vertical projector 1 has a shorter distance to the screen. That is, the projector 1 which is a vertical type can reduce the slow ratio.

  Next, features of the usage mode of the image display apparatus according to the present invention will be described with reference to FIG. FIG. 10 is a diagram of the projector 1 shown in FIG. 1 as viewed from the z-axis direction. In FIG. 10, in the projector 1, the direction perpendicular to the image forming surface of the DMD 11 is parallel to the y axis. The optical axis of the projection lens 12 is also parallel to the y axis. Although these are parallel to each other, the center of the image forming surface of the DMD 11 and the optical axis of the projection lens 12 are decentered by Δs in the x direction.

  An example of another usage mode of the projector 1 is shown in FIG. FIG. 11 is a plan view of the projector 1 shown in FIG. 1 viewed from the z-axis direction. In FIG. 11, in the projector 1, the direction perpendicular to the display surface of the DMD 11 is parallel to the y axis, and the optical axis of the projection lens 12 is also parallel to the y axis. Although these are parallel to each other, the center of the image forming surface of the DMD 11 and the optical axis of the projection lens 12 are shifted in the x direction. Further, by placing the plane mirror 15 between the projection lens 12 and the free-form surface mirror 13 and mounting the free-form surface mirror 13 on the side opposite to that in FIG. 10, the projection direction can be reversed. Thus, the projector 1 according to the present embodiment can change the projection direction of the image without changing the installation direction of the projector 1 by changing the mounting position of the free-form curved mirror 13.

  Next, an example of a method for fixing the projection lens 12 and the lens barrel 120 constituting the projection optical system to the projector 1 will be described with reference to FIG. FIG. 12 is a partially enlarged view of the vicinity of the projection optical system of the projector 1 as seen from the z-axis direction. In FIG. 12, the lens barrel 120 including the projection lens 12 is fixed to the side surface of the main body of the projector 1 with a plurality of screws 20. Since the projection lens 12 includes a plurality of lenses, in order to improve the light use efficiency of the projector 1, the distance D between the DMD 11 and the projection lens 12, the inclination of the projection lens 12 (its optical axis) itself, The inclination of the optical axis with respect to the display surface of the DMD 11 is an important factor.

  Since the distance D between the DMD 11 and the projection lens 12 is determined by the production accuracy of the main body (housing) of the projector 1, fine adjustment is performed using a spacer when the lens barrel 120 is fixed to the projector 1. By this fine adjustment, the tilt of the optical axis can be adjusted. The inclination of the DMD 11 itself can also be performed by using a spacer when fixing the DMD 11.

  The lens barrel 120 is a member made of a metal such as aluminum. The projection lens 12 is a member made of glass. Therefore, the lens barrel 120 including a plurality of lenses is a heavy member. In the case of a conventional horizontal projector, the lens barrel 120 is fixed so as to protrude in a direction against gravity, so that the projection lens 12 (its optical axis) may be displaced due to gravity.

  For this reason, when the projector is installed like a conventional horizontal projector, the manner in which the load is applied to the screw 20 differs depending on the fixing position, and the lens barrel 120 tends to be inclined. In addition, even when the optical axes are aligned, it is assumed that the projector device 1 will deteriorate over time by using the projector device 1 for a long time, and the optical axis will be shifted due to a shift in the fixed position of the projection lens 12. Further, when the projector 1 is transported, it is assumed that the optical axis of the projection lens is shifted due to vibration or impact in the vertical direction of the optical axis.

  As already described, the projector 1 according to the present embodiment uses the projection lens in a vertical installation form. As a result, the optical axis of the projection lens 12 becomes the gravity direction (y-axis direction). For this reason, a load due to gravity is applied in the longitudinal direction of the projection lens 12. That is, since the side surface of the projector 1 on which the lens barrel 120 holding the projection lens 12 is installed is parallel to the xz plane, the load on the projector 1 by the lens barrel 120 is uniformly related. Also, regarding the DMD 11, if the back surface of the DMD 11 is flat and has high accuracy, the DMD 11 can be placed stably with respect to gravity only by being placed. As described above, in the projector 1 according to the present embodiment, the optical axis of the DMD 11 and the projection lens 12 can be easily adjusted and adjusted simply by fixing the lens barrel 120 to the side surface of the main body of the projector 1 with the screw 20. The state can be stably maintained, and a robust product can be obtained even for long-term use.

  As described above, according to the image display device of the present invention, a vertical image display device is obtained in which the light use efficiency of the illumination optical system is high and the illumination optical system and the projection optical system can be used in a stable state. be able to.

  Next, another embodiment of the image display device according to the present invention will be described. In the embodiment described above, the light use efficiency of the illumination optical system can be improved by tilting the first relay lens 7 of the projector 1. Therefore, in this embodiment, the fact that the light use efficiency of the illumination optical system can be improved by tilting the second relay lens 8 will be described.

Similar to the embodiment already described, the tilt of the first relay lens 7 is set to α = 1 ° and β = −1 °, and the α and β tilts of the second relay lens 8 are set by simulation experiments using software. Table 2 shows the light utilization efficiency when changed.
(Table 2)

  In Table 2, when the tilt of the first relay lens 7 is α = 1 ° and β = −1 ° where the light utilization efficiency is high, the tilt of the second relay lens 8 that exhibits the highest light utilization efficiency is β = 1. This is the case. In addition, it can be seen from the results in Table 2 that the light utilization efficiency increases when the signs of α and β of the first relay lens 7 and the second relay lens 8 are reversed. That is, when the tilts of the first relay lens 7 and the second relay lens 8 are set in opposite directions, the light use efficiency is increased.

  FIG. 13 is a schematic diagram showing an example of a state in which the “tilt with the highest light utilization efficiency” shown in Tables 1 and 2 is set for the first relay lens 7 and the second relay lens 8. FIG. 13 shows the arrangement of the illumination uniformizing element 6, the first relay lens 7, and the second relay lens 8 as viewed from the y-axis direction (that is, viewed from the upper surface). As shown in FIG. 13, the optical axis A of the illumination uniformizing element 6 and the optical axes B of the first relay lens 7 and the second relay lens 8 are shifted in the x-axis direction.

  Further, the first relay lens 7 has β tilted counterclockwise, and the second relay lens 8 has β tilted clockwise.

  As described above, in the projector 1 according to the present embodiment, when the first relay lens 7 and the second relay lens 8 are respectively tilted in a predetermined direction, the light use efficiency can be improved.

  Next, still another embodiment of the first relay lens 7 and the second relay lens 8 will be described. As shown in FIG. 13, in the first relay lens 7 and the second relay lens 8, when the surface close to the illumination uniformizing element 6 is the first surface r1, and the opposite surface is the second surface r2, the glass material In consideration of the refractive index, each of the r1 aspherical surfaces in the relationship between the r1, r2, thickness, and diameter elements of the first relay lens 7 and the r1, r2, thickness, and diameter elements of the second relay lens 8. It is desirable to set the value of the coefficient α04 as shown in Table 3.

The refractive index (nd) of the glass material is 1.51680. Moreover, a refractive index (nd) may be 1.52307 using another glass material. Since the refractive index is slightly different, it is preferable to change the radius of curvature as shown in Table 3, but even if it is not changed, the light utilization efficiency is not greatly affected. Even if the glass materials are different, the tendency shown in Tables 1 and 2 is preserved, so that no problem occurs.
(Table 3)

  Next, a method for maintaining the tilt eccentricity of the first relay lens 7 and the second relay lens 8 will be described with reference to FIG. The shapes of the first relay lens 7 and the second relay lens 8 are rotationally symmetric with respect to the optical axis. FIG. 14 illustrates an embodiment in which the tilt eccentricity of the first relay lens 7 is maintained. A similar method can be used for the method of maintaining the tilt eccentricity of the second relay lens 8.

  As already described, the light use efficiency can be improved by tilting the first relay lens 7. Therefore, as shown in FIG. 14, a lens holding portion 1a that fixes the first relay lens 7 in a predetermined tilt state is used. The lens holding portion 1a may be formed on a part of the casing of the projector 1, or may be formed as a separate member formed by molding and fixed inside the casing.

  The lens holding portion 1a is formed with a groove 150 that matches the size of the first relay lens 7. The groove 150 is formed with an inclination capable of maintaining an optimum tilt (α and β) in the x-axis direction and the y-axis direction. The groove 150 illustrated in FIG. 14 has a β tilt set.

  The first relay lens 7 improves the light utilization efficiency not only by β but also by tilt of α. Therefore, as shown in FIG. 15, the lens holding portion 1a may be formed with a groove 150 in a depth direction inclined by a predetermined angle with respect to an axis orthogonal to the y-axis. FIG. 15 is an example of a cross section of the lens holding portion 1a viewed from the x-axis direction. In FIG. 15, the groove 150 is formed so as to set an optimal tilt of α in the x-axis direction with respect to an axis orthogonal to the y-axis. In this way, the light use efficiency of the projector 1 can be improved by forming the grooves 150 for fixing the first relay lens 7 in advance so as to have optimum α and β.

  Another example of a method for fixing the first relay lens 7 and the second relay lens 8 while maintaining a predetermined tilt will be described with reference to FIG. In FIG. 16, reference numeral 20 indicates an example of a frame installed inside the projector 1. The frame 20 is a member in which the installation surfaces of the first relay lens 7, the second relay lens 8, and the DMD 11 are integrated. In the frame 20, a lens holding portion 1 a for fixing the first relay lens 7, a lens holding portion 1 b for fixing the second relay lens 8, and an installation surface of the DMD 11 are integrally formed.

  Although the tilt accuracy of the first relay lens 7 and the second relay lens 8 depends on the accuracy of the frame 20, the frame 20 can be used rather than forming the holding portions 1 a and 1 b using a part of the housing of the projector 1. Stable accuracy can be maintained by using. The frame 20 also improves the accuracy of the position with the DMD 11.

  As described above, the positional accuracy of the first relay lens 7 and the second relay lens 8 and the DMD 11 can be maintained by the integrated member (frame 20). This is because it can be installed vertically.

Next, an example of the first relay lens 7 will be described. In this embodiment, the first relay lens 7 is an aspheric lens. Table 4 shows changes in light utilization efficiency caused by making the first relay lens 7 aspherical.
(Table 4)

  Table 4 shows the relationship between the aspheric coefficient fourth order (α04) and the light utilization efficiency when the second surface r2 (see FIG. 13) of the first relay lens 7 is aspherical. Based on Table 4, a graph in which the horizontal axis is an aspheric coefficient and the vertical axis is light utilization efficiency is approximated by a quadratic curve. As is apparent from FIG. 17, the optimum value of the fourth-order aspheric coefficient for asphericalizing the second surface r2 of the first relay lens 7 is about 0.00014. Thus, in the projector 1 according to the present embodiment, the light use efficiency can be improved by making the first relay lens 7 aspherical.

Next, an example of the second relay lens 8 will be described. In this embodiment, the second relay lens 8 is an aspheric lens. Table 5 shows changes in light utilization efficiency caused by making the second relay lens 8 aspherical.
(Table 5)

  Table 5 shows the relationship between the aspherical coefficient fourth order (α04) and the light utilization efficiency when the second surface r2 of the second relay lens 8 is aspherical. Based on Table 5, a graph in which the horizontal axis is an aspheric coefficient and the vertical axis is light utilization efficiency is approximated by a quadratic curve. As apparent from FIG. 18, the optimum value of the fourth-order aspheric coefficient for asphericalizing the second surface r2 of the second relay lens 8 is about −0.000035. Thus, in the projector 1 according to the present embodiment, the light use efficiency can be improved by making the second relay lens 8 aspherical.

Next, an embodiment of the second folding mirror 10 will be described. In this embodiment, the second folding mirror 10 is aspherical. Table 6 shows changes in light utilization efficiency caused by making the second folding mirror 10 aspherical.
(Table 6)

  Table 6 shows the relationship between the aspherical coefficient fourth order (α04) and the aspherical coefficient sixth order (α06) and the light utilization efficiency when the second folding mirror 10 is aspherical. The second folding mirror 10 is a concave mirror, and the radius of curvature is −75 mm.

  Based on Table 6, a graph in which the horizontal axis is a fourth-order aspheric coefficient and the vertical axis is light utilization efficiency is approximated by a quadratic curve is shown in FIG. Further, based on Table 6, a graph in which the horizontal axis is a sixth-order aspheric coefficient and the vertical axis is light utilization efficiency is approximated by a quadratic curve is shown in FIG. From the results shown in FIG. 19 and FIG. 20, the light utilization efficiency can be improved by introducing fourth-order and sixth-order aspheric surfaces to the second folding mirror 10.

Next, examples of the illumination optical system provided in the image display apparatus according to the present invention will be further described. Table 7 shows the optimal coordinates of the main members constituting the illumination optical system when the center of the image display area of the DMD 11 is (0, 0, 0) of the x axis, the y axis, and the z axis.
(Table 7)

  Next, examples of the projection optical system provided in the image display apparatus according to the present invention will be described. FIG. 21 is a schematic diagram illustrating an example of the projection lens 12, the free-form surface mirror 13, and the plane mirror 15 that constitute the projection optical system. In FIG. 21, the illumination optical system is omitted.

  As shown in FIG. 21, a plane mirror 15 is disposed between the projection lens 12 and the free-form surface mirror 13. The shape of the free-form curved mirror 13 is represented by a 15th-order coefficient, for example. The size of the projected image on the screen 14 is about 40 inches to 80 inches. The screen size is changed by changing the distance between the projector 1 and the screen 14. For example, when the projector 1 is brought closer to the screen 14, the screen size becomes smaller, and when the projector 1 is moved away from the screen 14, the screen size becomes larger.

  An example of the light amount distribution on the image forming surface of the DMD 11 of the projector 1 provided with the illumination optical system described above is shown in FIG. This light quantity distribution is obtained by a simulation experiment by ray tracing. The light quantity distribution position of the DMD 11 is such that the minus direction in the longitudinal direction is the left direction when the screen 14 is viewed from the front, the plus direction in the longitudinal direction is the right direction, the minus direction in the short direction is the upward direction and the short direction when the screen 14 is viewed from the front. The positive direction of the hand direction corresponds to the downward direction.

  In FIG. 22, an area surrounded by a dotted line 112 is an effective area corresponding to the image display area of the DMD 11. The light amount distribution is normalized and displayed with the maximum light amount in the region being 1, that is, 100%. As shown in FIG. 22, the minimum value of the normalized light amount distribution in the effective area 112 of the DMD 11 is 76% or more. Moreover, it can be seen that the same contour line area extends from the vicinity of the center and is illuminated uniformly. Incidentally, even if there is a light amount distribution of 50%, the human eye can hardly feel the difference, so the minimum value 76% of the light amount distribution as described above is not a problem.

  Next, an example of the light amount distribution on the screen by the projection light from the image display device according to the present invention is shown in FIG. Using the projector 1 having the optical system and the projection optical system that have already been described, a white image is projected on a screen having a diagonal of about 84 inches. The maximum value is normalized as 1. In the center of the screen, a region with a uniform amount of light spreads, but it can be seen that the amount of light decreases as it goes to the periphery.

  As described above, the image display device according to the present invention tilts the relay lens constituting the illumination optical system with respect to the optical axis, aspherical the second surface r2, and aspherical the folding mirror. The light utilization efficiency of the illumination optical system can be improved, and thereby, the projection light with a uniform light amount distribution can be emitted.

DESCRIPTION OF SYMBOLS 1 Projector 2 Light source 3 Lamp reflector 5 Color wheel 6 Illumination equalization element 7 1st relay lens 8 2nd relay lens 11 DMD
12 Projection lens 13 Free-form surface mirror

JP 2000-098272 A Japanese Patent No. 3121843

Claims (7)

A light source;
A condenser for condensing the light emitted from the light source;
An optical mixing element having an incident end in the vicinity of the condenser;
A color filter disposed between the condenser and the light mixing element, and superimposing color elements in time division on the light incident on the light mixing element;
A reflective image display element having a plurality of micromirrors arranged two-dimensionally and turning on and off the reflected light by changing the tilt angle of each micromirror between an on state and an off state;
An illumination optical system including a first relay lens and a second relay lens, a first folding mirror, and a second folding mirror disposed between an emission end of the optical mixing element and the reflective image display element; ,
A projection optical system that projects reflected light from a micromirror in an on state among a plurality of micromirrors constituting the reflective image display element, and projects an image on the projection surface A display device,
The angle formed between the display surface of the reflective image display element and the projected surface is substantially orthogonal,
The image display device in which the first relay lens is tilted with respect to an optical axis formed by the light source and the light mixing element.   The image display device according to claim 1, wherein the second relay lens is tilted with respect to the optical axis.   The image display device according to claim 2, wherein tilt directions of the first relay lens and the second relay lens are opposite to each other.   The shapes of the first relay lens and the second relay lens are rotationally symmetric with respect to the optical axis, and the tilt is caused by a lens holding portion that holds the first relay lens and the second relay lens on the optical axis. 4. The image display device according to claim 1, wherein the image display device is formed by being tilted with respect to the image display device.   The image display device according to claim 1, wherein a lens surface of the first relay lens has an aspherical shape.   6. The image display device according to claim 1, wherein a lens surface of the second relay lens has an aspherical shape. ,
The image display device according to claim 1, wherein a reflection surface of the second folding mirror has an aspherical shape.