JP2005338138A - Projection image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve miniaturization in a combination of a projection optical system by a reflection optical system and an optical engine and the simplification of handling thereof. <P>SOLUTION: The configuration suitable for vertical placement is employed in the combination of the projection optical system by the reflection optical system and the optical engine. A color combining system bent on a short side is vertically placed and is combined by a vertical type with a free curved surface projection system. As compared to the case the projection system is combined with the conventional optical engine as the projection equipment using particularly the reflection optical system, the space volume (the smallest rectangular parallelepiped volume that the space volume is confined) is made smaller than the case the projection system is combined with the conventional optical system (miniaturization) and the shape of the casing of the equipment is simplified and both of the appearance and handling are improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  A free-form surface refers to an arbitrary curved surface shape expressed by an arbitrary function such as a two-dimensional power series function. An optical system having such a surface as an optical action surface for reflection (mirror or the like) or transmission (lens or the like) is known.

  The present invention relates to a projection type image display apparatus such as a liquid crystal projector using a projection optical system in which a projection optical system is configured by a combination of a free-form surface reflection optical system (free-form surface mirror).

  A projection optical system using a free curved surface reflecting surface (free curved mirror) will be described.

  Here, it is assumed that all the surfaces of the optical system are constituted by reflecting surfaces. However, regarding the hybrid optical system that combines the coaxial system (refractive lens system) and the reflecting surface, the description is similarly applied to the portion constituted by the reflecting surface.

  Each free-form surface shape constituting the imaging optical system is plane-symmetric with respect to a reference plane. Further, with respect to all the free-form curved reflecting surfaces, the plane serving as the plane symmetry reference is on the same plane. This is defined as the reference plane of the optical system.

  Next, the reference optical axis will be described.

  The imaging optical system does not have an optical axis that is a rotationally symmetric axis that penetrates the center of the optical system unlike a general coaxial optical system. Therefore, it is necessary to define an alternative optical axis for convenience. Consider one light beam that starts at one point at the center of the object plane and reaches one point at the center of the conjugate image plane. One light beam is defined that travels through the center of the beam spread. The path followed by this ray is defined as the reference optical axis. At this time, the location defining the center of the light beam is the position of the stop.

  The reference optical axis of the imaging optical system exists on one plane. The plane is the reference plane described above.

  The characteristics when the imaging optical system is applied to a device such as a liquid crystal projector will be described.

  The optical system is easy to make a wide angle as compared with the coaxial lens system and has a high degree of freedom in handling the optical path. There are some other advantages derived from the configuration of only the reflecting surface, but details are omitted here.

  In the case of a coaxial lens system, the elevation angle of a light beam projected from a projector onto a screen is usually about 10 ° to 15 °. On the other hand, since the optical system has no concept of being on-axis, a large projection elevation angle such as 40 ° or 60 °, which is practically impossible with a coaxial lens system, can be freely designed. As a result, there is an advantage that a projector can be installed immediately below the screen.

In the case of the imaging optical system, the form of the optical system is different from that of a general coaxial lens system, and various forms are made depending on the design of the optical path. Basically, as described in detail above, the optical path of the reference optical axis is folded on a predetermined plane. Therefore, the form of the optical system itself is such that the reflecting surfaces are arranged along the reference plane. (Figure 2)
The reference plane is substantially parallel to the vertical direction. The casing that covers the outside of the optical system is roughly box-like like a thick plate placed vertically (the thickness direction is the width of each mirror). (Figure 2)
The size of the optical system casing is determined by the following factors.

The projection optical system of a liquid crystal projector is required to be telecentric on the image display panel side. For this reason, the size of the first mirror is determined by the diameter of the light beam reaching the first mirror.
◆ Screen size of image display panel device ◆ Distance from image display panel to first mirror (thickness of color composition prism)
◆ Object side F value ◆ The presence or absence of vignetting and the amount of vignetting in the periphery of the screen.

In addition, the size of the subsequent mirror is influenced by the size of the first mirror,
◆ Whether to form an image once in or near the optical system,
◆ pupil size,
◆ The distance from the pupil of the mirror,
It depends on factors such as.

  Reducing the size of the first mirror contributes to miniaturization of the entire optical system.

Of the size of the projection optical system, the size in the direction perpendicular to the reference plane (that is, the direction corresponding to the horizontal width direction of the screen in the case of a liquid crystal projector) is almost determined by the above factors. On the other hand, the size of the optical system in the reference plane depends on the distance between the mirrors along the reference optical axis. This mirror interval depends on the width of the light beam in the reference plane (mirror size). The method of folding the optical path is determined with a gap narrowed so as to avoid interference between the light beam and the free-form surface mirror and to make the most compact. (Figure 2)
Next, the color synthesis prism will be described.

  In the liquid crystal projector, the RGB liquid crystal panels are arranged almost conjugate with each other as the object plane of the projection optical system. The color light of the reference optical axis that has passed through each liquid crystal panel is integrated into one light beam by the color synthesis prism. Then, it reaches the image plane as the reference optical axis of the projection optical system.

  Conventionally, in a liquid crystal projector, a cross dichroic prism (FIG. 7) in which two dichroic mirror layers that reflect light having different wavelength ranges are arranged in an X shape inside the prism has been used for color synthesis. This is disclosed in Japanese Patent Application Laid-Open No. 09-318907 (Seiko Epson Corporation). Since the cross dichroic prism has two dichroic mirror layers arranged in an X shape inside the prism, there is an advantage that the color synthesis prism can be made small. The cross dichroic prism is composed of four triangular prisms. If the angle accuracy and bonding accuracy of individual prisms are not increased in manufacturing, the dichroic mirror layer is likely to have a step or angular deviation, and a linear pattern on the screen. When the image is projected on the screen, or when an image with uniform brightness is projected on the screen, there are disadvantages that a bright vertical stripe and a dark vertical stripe are likely to occur near the center of the screen. In order to solve this drawback, a color synthesizing prism that does not cross the dichroic mirror layer is proposed in Japanese Patent Laid-Open Publication No. 2001-290010 (Canon Inc.). This 3P prism (FIG. 9) or 4P prism is a combination of three or four triangular prisms.

  The thickness of the color synthesis prism will be described.

  As described above, the thickness of the color synthesis prism determines the distance between the projection optical system and the image display panel device, which directly affects the size of the projection optical system.

A plane composed of the reference optical axes of the RGB colors immediately before being synthesized by the color synthesis prism is defined as a color synthesis plane. (Fig. 11)
The thickness of the color synthesis prism depends on the length of the dichroic mirror effective portion in the direction parallel to the color synthesis plane. The factors that determine this are almost the same as the factors that determine the size of the light beam reaching the first mirror. That is,
◆ Screen size of image display panel ◆ Object side F value ◆ It is determined by the component in the direction parallel to the color composition plane of each item of the presence or absence of vignetting and the amount of vignetting.

  The screen of the image display panel is usually rectangular. A configuration in which color composition is performed within a plane including the long side of the screen is generally used. If this is performed on the short side, the effective length of the dichroic mirror region in the color synthesis plane direction is shortened, and the thickness of the prism can be reduced.

  An example of reducing the thickness of the prism by switching the image display area of the image display panel in this way is disclosed in Japanese Patent Application Laid-Open No. 11-249070 (Sharp Corporation) regarding a cross dichroic prism. Yes. The long side of the rectangular image display panel conventionally coincides with the color synthesis plane direction, but by changing this to the short side direction, the prism thickness can be shortened by the short side / long side. However, when the orientation of the screen display panel device is rotated by 90 ° in the plane as described above, the vertical and horizontal directions of the projected image are also rotated by 90 ° in the plane to form a vertically long screen.

In general, the orientation of the screen projected by a liquid crystal projector or the like is usually landscape. Therefore, conversely, it is possible to turn the entire color composition system 90 ° to set it vertically and make a landscape screen. However, since a general coaxial lens projection system has a small elevation angle of about 10 ° to 15 °, a vertically long casing is placed in front of the screen. In this case, from the viewer's point of view, the housing is likely to get in the way by blocking the screen. (Fig. 13)
Japanese Patent Laid-Open No. 11-249070 JP 2001-290010 A JP 09-318907 A

An imaging optical system that uses a free-form curved reflecting surface has a smaller number of mirror surfaces than the number of coaxial lens surfaces of equivalent performance, but the light beam incident on a certain mirror is emitted on the same side as the incidence. Due to the limitations inherent in the reflection system, there is a limit to reducing the distance between the surfaces. Due to such factors, there is a problem that the optical system tends to be difficult to downsize. (Figure 2)
Further, in order to explain the next problem, a part constituted by the illumination optical system and the color synthesis prism system of the liquid crystal projector will be described. (Fig. 11)
Regardless of whether the color synthesis prism is a cross dichroic prism or a 3P or 4P prism, each reference optical axis passing through the three liquid crystal panels of RGB is in the color synthesis plane. In addition, the reference optical axis in the illumination optical system is generally configured to exist in the same color synthesis plane.

  That is, a light beam that starts from the light source lamp and travels along the reference optical axis is first divided into three color lights of RGB in an intermediate optical path. Then, the liquid crystal display panel that modulates the color light intensity of each of RGB according to the image signal is illuminated from the back side or from the front side (in the case of a reflective liquid crystal). These light beams of color light are again combined into one optical axis by the color combining prism and reach the projection optical system. These optical axes exist in almost one color synthesis plane.

  As described above, since the optical axes of the illumination system and the color synthesis system also exist in substantially the same color synthesis plane, the arrangement of the components of these optical systems extends in the plane direction. Therefore, this effect also appears in the appearance of the device housing, and the housing of a normal liquid crystal projector has a shape that spreads in a direction along this plane, and generally a thin flat rectangular parallelepiped in a direction parallel to the installation surface. It has a base form.

  Combining the illumination optical system and the color synthesizing optical system with the projection optical system using the above-described free-form curved reflecting surface to constitute a liquid crystal projector causes the following problems.

That is, since the mirror systems are arranged in a reference plane parallel to the vertical direction due to the arrangement of the projection optical system (FIG. 2), the portion of the projection optical system is actually a structure that extends vertically and front and rear. On the other hand, in the illumination system and the color synthesizing system, the plane formed by the optical path along the reference optical axis is generally arranged substantially parallel to the surface such as a desk installed as described above. (Fig. 11)
The liquid crystal projector includes a box-shaped housing that extends horizontally on the installation surface of the illumination and color composition system and the like, and a projection optical system portion of the box-shaped housing that extends in a direction perpendicular to the installation surface. As a result, the overall apparatus housing shape is as shown in FIG. The shape of the appearance lacks simplicity and is difficult to handle. Since there is a large difference in shape between the illumination and color synthesis system and the projection optical system, there is a clear boundary between the twisted joints between them, and the mechanical rigidity at this boundary tends to decrease. Further, in such a configuration, when the device is lifted, the force is likely to be uneven. A force is applied only to any part, and the force tends to concentrate particularly on the boundary part. When a positional deviation such as an inclination occurs at the joint between the projection optical system and the illumination unit, the projection image quality such as a single blur is deteriorated. In order to avoid such a problem, there may be a measure to design a casing that covers the entire apparatus and to make it difficult to wastefully apply force to the joint portion due to external factors. However, the volume of the housing that accommodates all of these becomes too large, and the ease of handling and storage are further reduced. (Fig. 14)
The above two major problems are summarized.

About the first mentioned contents,
(1-1) When a known color synthesizing prism thinning means is used, the projection screen rotates 90 °.

  (1-2) To return the screen to landscape orientation in (1-1), the illumination system or the like is placed vertically, and in combination with the conventional coaxial projection system, the projection angle is low, and the vertically placed housing is used for viewing the projection screen. Get in the way.

Regarding the second item,
(2-1) A free-form curved reflecting surface projection optical system is difficult to downsize.

  (2-2) A projection optical system using a free-form curved reflecting surface has a vertical casing.

  (2-3) A combination of (2-2) and a horizontal illumination / color composition housing is not easy to handle.

  In order to solve the above problems, the factor that determines the size of the free-form surface projection optical system is the thickness of the color synthesis prism. Therefore, a prism system that combines colors on the short side of the screen is used.

  In addition, the illumination and color composition system is also rotated so that the vertical and horizontal directions of the screen are switched, and the projected screen is horizontally long as before. The optical system can reduce the size of the mirror as much as the thickness of the color combining prism is reduced.

  By combining this illumination and color synthesis system with a free-form surface projection optical system, both are placed vertically.

  The projection type image display apparatus according to the first aspect of the present invention is an optical system having at least one free-form curved reflecting surface, and the shapes of the free-form curved reflecting surfaces are all plane-symmetric with respect to one reference plane. Starting from one point at the center of the object plane of the system, one light beam that reaches one point at the center of the image plane in a conjugate relationship with this is used as a reference light for the optical system. When defined as an axis, a projection optical system in which the reference optical axis exists on the reference plane, a cross dichroic prism that combines a plurality of color lights, and an object plane of the optical system via the cross dichroic prism are conjugated with each other A plurality of image modulation elements, each of which is placed at a different position and illuminated with different color light, and whose image display surface is rectangular, and the color light modulated by the plurality of image modulation elements is converted into the cross dichroic The color is synthesized with a rhythm and projected onto the image plane by the projection optical system, and the reference optical axes of a plurality of color lights just before color synthesis at the cross dichroic prism are all on one plane. When this plane is defined as a color synthesis plane, the color synthesis plane and the short sides of the display surfaces of the plurality of image modulation elements are parallel, and the reference plane of the projection optical system and the color synthesis plane are The image modulation elements are arranged with respect to the cross dichroic prism and the projection optical system so as to be parallel to each other and the projected image is horizontally long.

  The projection-type image display apparatus according to claim 2 of the present invention is an optical system having at least one free-form curved reflecting surface, and the free-form curved reflecting surface is all plane-symmetric with respect to one reference plane. Starting from one point at the center of the object plane, one light beam traveling to the center at the center of the image plane conjugate with this is converted to a reference light axis of the optical system. Is defined as a projection optical system in which the reference optical axis exists on the reference plane and a color combining prism that combines a plurality of color lights, and has a surface that serves as a total reflection surface and a transmission surface on the most exit side. A color synthesizing prism comprising two dichroic mirror layers that reflect light having different wavelength ranges inside the prism, the two dichroic mirror layers including at least three prisms that do not intersect inside the prism; The A plurality of image modulation elements, which are placed at conjugate positions as the object plane of the optical system via a combining prism, are each illuminated with different color light, and whose image display surface is rectangular, and the plurality of image modulation elements The color light modulated by the element is color-synthesized by the color synthesis prism and projected onto an image plane by the projection optical system, and a plurality of color lights just before color synthesis by the color synthesis prism The reference optical axes are all on one plane, and when this plane is defined as a color synthesis plane, the short side direction of the color synthesis plane and the display surfaces of the plurality of image modulation elements are parallel, and the projection optics The image modulation element is arranged with respect to the color synthesis prism and the projection optical system so that the reference plane of the system and the color synthesis plane are parallel to each other and the projected image is horizontally long.

  A projection type image display apparatus according to a third aspect of the present invention is an optical system having at least one free curved surface reflecting surface, and the shape of the free curved surface reflecting surface is all plane-symmetric with respect to one reference plane. Starting from one point at the center of the object plane of the system, one light beam that reaches one point at the center of the image plane in a conjugate relationship with this is used as a reference light for the optical system. When defined as an axis, the reflected optical beam is modulated by irradiating the projection optical system having the reference optical axis on the reference plane and a plurality of reflective liquid crystal image modulation elements as illumination light from substantially the front. Are separated from the illumination light to obtain a plurality of modulated color lights, and a color synthesis prism system composed of at least three or more sets of prisms for color synthesis of the color light and the color synthesis prism system. As an object surface of the optical system The color composition prism system includes the plurality of reflective liquid crystal image modulation elements, the image display surface of which is placed in a conjugate position with respect to each other, and the color light modulated by the plurality of reflective liquid crystal image modulation elements. And the projection optical system projects the image onto the image plane, and the reference optical axes of the plurality of color lights immediately before color synthesis in the prism system are all on one plane, When this plane is defined as a color synthesis plane, the color synthesis plane and the short side direction of the display surfaces of the plurality of reflective image modulation elements are parallel, and the reference plane of the projection optical system and the color synthesis plane are The reflection type liquid crystal image modulation elements are arranged with respect to the color synthesis prism system and the projection optical system so that they are parallel to each other and the projected image is horizontally long.

  According to a fourth aspect of the present invention, there is provided a projection type image display apparatus according to the first or second aspect, other than on the extension line of the reference optical axis immediately after the color light synthesis among the plurality of image modulation elements arranged around the color synthesis prism. The arrangement of the image modulation element and the shape of the color synthesis prism itself are asymmetric with respect to the reference optical axis immediately after the color light synthesis, and around the reference optical axis immediately after the color light synthesis on the color synthesis plane. The image modulation element and the color composition so as not to cause mechanical interference with an optical element such as a free-form curved reflecting surface constituting the projection optical system. It is characterized in that the orientation of the prism arrangement is selected and determined.

  According to a fifth aspect of the present invention, there is provided a projection type image display apparatus according to the first or second aspect, wherein the image plane direction side is positive along the reference optical axis immediately after color light synthesis, and the exit end face of the color synthesis prism is the origin. When the Z axis is defined as follows, the arrangement of the image modulation elements other than the Z axis among the plurality of image modulation elements arranged around the color synthesis prism and the shape of the color synthesis prism itself are the Z axis It is possible to adopt two types of arrangements that are asymmetric with respect to the color composition plane and that are inverted about the Z-axis on the color synthesis plane, and among the optical elements constituting the projection optical system, When the optical element is present in a negative space, the one of the two arrangements of the image modulation element and the color synthesizing prism is selected so as not to cause mechanical interference with the optical element. Yes.

  According to a sixth aspect of the present invention, there is provided a projection type image display apparatus according to the third aspect, wherein the reference optical axis immediately after the light composition of all the colors among the plurality of reflection type liquid crystal image modulation elements arranged around the color composition prism system. The arrangement of the reflection type liquid crystal image modulation elements other than the extension line of the color liquid crystal and the arrangement of the color synthesis prism system itself are asymmetric with respect to the reference optical axis immediately after the color light synthesis, and on the color synthesis plane. In addition, it is possible to adopt two arrangements inverted around the reference optical axis immediately after the color light synthesis, and no mechanical interference occurs with optical elements such as a free-form reflecting surface constituting the projection optical system. Thus, the arrangement direction of the reflective liquid crystal image modulation element and the color synthesis prism is selected and determined.

  According to a seventh aspect of the present invention, there is provided a projection type image display apparatus according to the third aspect, wherein the image plane direction side is positive along the reference optical axis immediately after the photosynthesis of all colors, and the color synthesis prism closest to the image side. When defining the Z axis with the exit end face as the origin, the arrangement of the reflective liquid crystal image modulation elements other than the Z axis among the plurality of reflective liquid crystal image modulation elements arranged around the color synthesis prism system; and The shape of the color synthesizing prism system itself is asymmetric with respect to the Z-axis, and can take two arrangements that are inverted about the Z-axis on the color synthesizing plane. Among the optical elements constituting the optical system, when there is the optical element in the space where the Z coordinate value is negative, of the two arrangements of the image modulation element and the color synthesizing prism system, It is characterized by selecting the arrangement that does not cause interference

  According to an eighth aspect of the present invention, there is provided the projection type image display apparatus according to any one of the first, second and third aspects, wherein the F number of the illumination optical system in the short side direction of the image display surface of the image display apparatus is larger than the other directions. It is said.

  When a projection optical system using a free-form curved reflecting surface is arranged so that the long side of a normal image display panel and the color synthesis plane are parallel, the matching of the illumination system & color synthesis system and the shape of the optical system is poor, and the housing The body becomes unstable or increases in size. Further, there was no means for reducing the size of the optical system, and the compatibility was not good.

  On the other hand, according to the present invention, by combining the color combining prism in which the short side of the image display panel and the color combining plane are arranged in parallel with the free curved reflecting surface projection optical system, the size of the reflecting optical system can be reduced. Is possible. At the same time, the illumination system and the color synthesis system are arranged vertically so as not to make the projection image vertically long, so that the alignment of the projection optical system and the illumination system & color synthesis system is good, and the housing is not enlarged. Further, the vertical casing does not get in the way because of the characteristic of the reflection optical system that the projection elevation angle is large.

  When a general coaxial lens system with a low screen projection height is used as the projection optical system, such a vertical arrangement will cause a projection display device with a high height to stand in front of the projection screen and block the screen. Get in the way of appreciation.

  FIG. 1 shows a first embodiment of the present invention. FIG. 10 is a conventional diagram for comparison.

  In this embodiment, the arrangement of the cross dichroic prism disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 11-249070 (Sharp Corporation) with the short side of the image display panel parallel to the color synthesis plane is used. Combined with a projection optical system using a free-form curved reflecting surface. This is shown in FIG. For comparison, FIG. 10 shows a color synthesis system using a conventional cross dichroic prism and the projection optical system.

  FIG. 3 shows an example of a product form in which the illumination system and color composition system housing of the embodiment of FIG. 1 and the projection optical system housing are combined.

  First, FIG. 1 will be described.

  Unlike the conventional arrangement shown in FIGS. 10 and 11, the cross dichroic prism which is a color composition system is arranged such that the image display panel is rotated 90 ° within the screen. For this reason, in order to prevent the projection screen from becoming vertically long, it is necessary to rotate the color synthesis system and the illumination system by 90 ° so as to cancel out this. In this configuration, since the colors are folded and combined in the direction along the short side of the image display panel, the thickness of the prism is simply reduced by an amount corresponding to the aspect ratio of the screen. As a result, the first mirror approaches the image display panel as compared with the conventional arrangement shown in FIG. (Φ1 <φ2) The reduction in the size of the first mirror contributes to downsizing the entire optical system.

  Moreover, the form of the product at this time is shown in FIG. Compared with the conventional case shown in FIG. 14, the illumination system & color synthesis system and the projection optical system are both vertical casings, so that they are well organized. Moreover, since high elevation angle projection, which is a characteristic of free-form curved reflection optical systems, is possible, even with such a vertical casing, an image can be projected at a higher position, and the screen is not blocked by the casing. . These are easily understood when FIG. 3 and FIG. 13 are compared.

  FIG. 4 shows a second embodiment of the present invention.

  In this example, in the 3P prism disclosed in Japanese Patent Application Laid-Open No. 2001-290010 (Canon Inc.), the short sides of the image display panels are arranged parallel to the color synthesis plane. A projection optical system that uses a free-form curved reflecting surface is combined with the 3P prism of this arrangement. This is shown in FIG. Compared with the color synthesizing system using the conventional cross dichroic prism shown in FIG. 2 and the projection optical system, even in the case of a 3P prism that tends to be thicker than the cross dichroic prism under the same conditions, the optical system according to the configuration of the present invention It can be seen that the size of is comparable.

  In the second embodiment, an example of the product form in which the housing of the illumination system and the color composition system and the housing of the projection optical system are combined is almost the same as that shown in FIG. 3 in the case of the first embodiment. It is. Therefore, the case shape of the second embodiment is substituted in FIG.

  First, FIG. 4 will be described.

  Unlike the conventional arrangement, the 3P prism, which is a color composition system, has an arrangement in which the image display panel is rotated 90 ° within the screen. Therefore, in order to prevent the projected image from becoming vertically long, the color synthesis system and the illumination system need to be rotated by 90 ° so as to cancel out this. In this configuration, since the colors are folded and combined in the direction along the short side of the image display panel, the thickness of the prism is simply reduced by an amount corresponding to the aspect ratio of the screen. As a result, since the first mirror is closer to the image display panel than in the conventional arrangement, the beam diameter (φ3) on the mirror is reduced. A reduction in the size of the first mirror contributes to downsizing the entire optical system.

  Moreover, although it is a form of the product at this time, it becomes a form as shown in FIG. 3 also in this case. Compared to the conventional case shown in FIG. 14, the illumination system & color synthesis system and the projection optical system are both vertical casings, so that they are well organized. In addition, since a configuration of high elevation angle projection is possible, an image can be projected at a high position even in a vertical casing, and the screen is not blocked by the casing. These states are easily understood when FIG. 3 is compared with FIG.

  Also, what is characteristic in this embodiment is the asymmetry of the color synthesis prism and the liquid crystal panel arrangement. In the case of the cross dichroic prism as in the first embodiment, the two color lights reflected and synthesized by the dichroic mirror surface are in a symmetric positional relationship with respect to the optical axis of the transmitted color light. Therefore, there is no difference depending on how it is placed.

  However, as is apparent from FIG. 4, in the case of the 3P prism, the color light reflected and synthesized by each dichroic mirror surface is asymmetric with respect to the optical axis of the transmitted color light. In particular, the liquid crystal panel on the side of the color light to be combined last (color light that is totally reflected inside the prism) requires a large overhanging space. In the case of the free-form surface reflecting optical system used in FIG. 4, a part of the mirror A protrudes above the color synthesis prism. Therefore, in the present embodiment, it is preferable to arrange the color light on the optical path side, which is once totally reflected and synthesized, on the side opposite to the free-form surface mirror A side. This state is circled in FIG.

  FIG. 5 shows a third embodiment of the present invention.

  In this embodiment, a reflective liquid crystal panel is applied to a color synthesis prism having an image display panel.

  The color composition system for the reflective liquid crystal is a known means disclosed in, for example, Japanese Patent Publication No. 2002-357708 (Color Link Corp.). Then, with respect to the color synthesis prism system corresponding to this reflective liquid crystal panel, the short side of each image display panel is arranged parallel to the color synthesis plane. A projection optical system using a free-form curved reflecting surface is combined with the arrangement of the color combining prism system for the reflective liquid crystal. These will be described with reference to FIGS.

  In the third embodiment, an example of a product form in which a housing of an illumination system and a color composition system and a housing of a projection optical system using a free-form curved reflecting surface is combined is shown in FIG. 3 in the case of the first embodiment. It will be almost the same as the thing. Accordingly, the housing shape of the third embodiment is substituted in FIG.

  First, FIG. 6 and FIG. 12 will be described.

  6 and 12 show a color synthesizing prism system when a reflective liquid crystal panel is used. FIG. 12 shows a conventional arrangement, and FIG. 6 shows an arrangement in which the image display panel device is rotated by 90 ° in the plane, unlike the conventional arrangement. Therefore, in order to prevent the projected image from becoming vertically long, the color synthesis system and the illumination system need to be rotated by 90 °. In this configuration, since the colors are folded and synthesized in the direction along the short side of the image display panel device, the thickness of the prism is simply reduced by an amount corresponding to the aspect ratio of the screen. The prism thickness L2 is obtained when the panel is rotated with respect to the conventional prism thickness L2, and the prism thickness can be reduced by a distance corresponding to the aspect ratio of the screen.

  As a result, since the first mirror is closer to the image display panel device than in the conventional arrangement, the beam diameter on the mirror is reduced. A reduction in the size of the first mirror contributes to downsizing the entire optical system.

  Further, the form of the product at this time is also the form shown in FIG. Compared to the conventional case shown in FIG. 14, the illumination system & color synthesis system and the projection optical system are both vertical casings, so that they are well organized. In addition, since a configuration of high elevation angle projection is possible, an image can be projected at a high position even in a vertical casing, and the screen is not blocked by the casing. These are easily understood when FIG. 3 and FIG. 13 are compared.

  Further, what is characteristic of this embodiment is the asymmetry of the arrangement of the liquid crystal panels for color synthesis as in the second embodiment. In the case of the cross dichroic prism as in the first embodiment, the two color lights reflected and synthesized by the dichroic mirror surface on the optical axis of the projection optical system are transmitted on the optical axis of the transmitted color light, that is, immediately after synthesis on the dichroic prism. The reference optical axes are symmetrical with each other. Therefore, there is no difference depending on the direction of placement.

  However, as is apparent from FIG. 5, the color combining prism system that illuminates the reflective liquid crystal image display element from the front, splits the light beam that is image-modulated and reflected on the same front face, and combines them again is as follows: It is asymmetric with respect to the reference optical axis after synthesis. As shown in the circle of FIG. 5, the two reflective liquid crystal panels are preferably arranged in a direction that does not interfere with the mirror B.

1 is a cross-sectional view of an image projection display device according to a first embodiment (cross dichroic prism) of the present invention (an example of a short side // color combination plane of an image display panel device). Schematic of the example of the projection optical system using the free-form curved reflective surface used in the first, second, and third embodiments of the present invention. Schematic of the external appearance of the housing of the image projection display device when the first, second and third embodiments of the present invention are applied. Sectional drawing of the image projection display apparatus of 2nd Example (3P prism) of this invention (example which is a short side // color synthetic | combination plane of an image display panel device). Sectional drawing (example which is a short side /// color synthesis plane of an image display panel device) of the image projection display apparatus of 3rd Example (reflective liquid crystal panel and exclusive synthetic prism) of this invention. Color synthesizing prism used in the third embodiment of the present invention (an example of a long side of the image display panel device // color synthesizing plane). Explanatory drawing of a cross dichroic prism. The figure for demonstrating the definition of the structure of a cross dichroic prism, the direction of a color composition, etc. which are used by this invention. Explanatory drawing of 3P prism. Sectional drawing of the image projection display apparatus of the prior art example corresponding to 1st Example of this invention (The example which is a long side // color synthetic | combination plane of an image display panel device). A conventional example of a color synthesis system using a cross dichroic prism (an example of a long side of the image display panel device // color synthesis plane) and a light source optical system (part of the configuration is omitted). Explanatory drawing of the conventional structure of the color synthetic | combination prism in the case of using a reflective liquid crystal panel (example which is a long side /// color synthetic | combination plane of an image display panel device). FIG. 6 is a schematic diagram of the external appearance of a conventional example of an image projection display device that combines a coaxial refraction lens system and a color composition system (which is a short side // color composition prism of an image display panel device). Schematic diagram of the appearance of a conventional case of an image projection display device that combines a conventional illumination system (an example of a long side // color combining plane of an image display panel device) and a projection optical system using a free-form curved reflecting surface .

Claims (8)

An optical system having at least one free-form curved reflecting surface, and the shape of the free-form curved reflecting surface is all symmetrical with respect to one reference plane, and starts from one point at the center of the object plane of this optical system. When defining one light beam traveling through the center of one light beam reaching one point at the center of the image plane in a conjugate relationship with this as the reference optical axis of the optical system,
A projection optical system in which the reference optical axis exists on the reference plane;
A cross dichroic prism that combines multiple color lights;
A plurality of image modulation elements which are placed at conjugate positions as object surfaces of the optical system via the cross dichroic prism, each illuminated with different color light, and whose image display surface is rectangular,
The color light modulated by the plurality of image modulation elements is color-combined by the cross dichroic prism and projected onto an image plane by the projection optical system,
The reference optical axes of the plurality of color lights immediately before color synthesis in the cross dichroic prism are all on one plane, and when this plane is defined as a color synthesis plane,
The short side direction of the display surface of the color synthesis plane and the plurality of image modulation elements is parallel,
The reference plane of the projection optical system and the color synthesis plane are parallel to each other;
A projection-type image display device, wherein the image modulation element is arranged with respect to the cross dichroic prism and the projection optical system so that the projected image is horizontally long. An optical system having at least one free-form surface, wherein the free-form surfaces are all symmetrical with respect to one reference plane, and start from one point at the center of the object plane of the optical system; When defining one light beam traveling through the center of one light beam reaching one point at the center of the image plane in a conjugate relationship with this as the reference optical axis of the optical system,
A projection optical system in which the reference optical axis exists on the reference plane;
A color combining prism that combines a plurality of color lights, the surface having both a total reflection surface and a transmission surface is provided on the most exit side, and two dichroic mirror layers that reflect light having different wavelength ranges are provided inside the prism. The two dichroic mirror layers are color combining prisms composed of at least three or more prisms that do not intersect inside the prism;
A plurality of image modulation elements, which are placed at conjugate positions as object surfaces of the optical system via the color synthesis prism, each illuminated with different color light, and whose image display surface is rectangular,
The color light modulated by the plurality of image modulation elements is color-synthesized by the color synthesis prism, and projected onto an image plane by the projection optical system,
The reference optical axes of a plurality of color lights immediately before color synthesis in the color synthesis prism are all on one plane, and when this plane is defined as a color synthesis plane,
The short side direction of the display surface of the color synthesis plane and the plurality of image modulation elements is parallel,
The reference plane of the projection optical system and the color synthesis plane are parallel to each other;
A projection-type image display apparatus, wherein the image modulation element is arranged with respect to the color synthesis prism and the projection optical system so that a projected image is horizontally long. An optical system having at least one free-form surface, and the shape of the free-form surface is all symmetrical with respect to one reference plane, and starts from one point at the center of the object plane of this optical system. When defining one light beam traveling through the center of one light beam reaching one point at the center of the image plane in a conjugate relationship with this as the reference optical axis of the optical system,
A projection optical system in which the reference optical axis exists on the reference plane;
A plurality of reflective liquid crystal image modulation elements are irradiated with different colored light as illumination light from substantially the front, and the modulated reflected light flux is polarized and separated from the illumination light to obtain a plurality of modulated colored light, which is then converted into color. A color synthesizing prism system composed of at least three sets of prisms for synthesizing and the like, and is placed at a conjugate position as the object plane of the optical system via the color synthesizing prism system, and its image display surface is rectangular A plurality of reflective liquid crystal image modulation elements,
The color light modulated by the plurality of reflective liquid crystal image modulation elements is color-synthesized by the color synthesis prism system, and projected onto an image plane by the projection optical system,
The reference optical axes of the plurality of color lights immediately before color synthesis in the prism system are all on one plane, and when this plane is defined as a color synthesis plane, the color synthesis plane and the plurality of reflective images The short side direction of the display surface of the modulation element is parallel,
The reference plane of the projection optical system and the color synthesis plane are parallel to each other;
A projection-type image display device, wherein the reflection-type liquid crystal image modulation element is arranged with respect to the color synthesis prism system and the projection optical system so that the projected image is horizontally long. Among the plurality of image modulation elements arranged around the color synthesis prism, the arrangement of the image modulation elements other than on the extension line of the reference optical axis immediately after the color light synthesis and the shape of the color synthesis prism itself are as follows. Asymmetric with respect to the reference optical axis of
In addition, it is possible to take two arrangements reversed around the reference optical axis immediately after the color light synthesis on the color synthesis plane,
The arrangement direction of the image modulation element and the color synthesis prism is selected and determined so as not to cause mechanical interference with an optical element such as a free-form surface reflecting surface constituting the projection optical system. The projection-type image display device according to claim 1. When defining the Z-axis along the reference optical axis immediately after color light synthesis, with the image plane direction side being positive and the exit end surface of the color synthesis prism being the origin,
Among the plurality of image modulation elements arranged around the color synthesis prism, the arrangement of the image modulation elements other than on the Z axis and the shape of the color synthesis prism itself are asymmetric with respect to the Z axis,
In addition, it is possible to take two arrangements reversed around the Z axis on the color synthesis plane,
Among the optical elements constituting the projection optical system, when the optical element is in a space where the Z coordinate value is negative, of the two arrangements of the image modulation element and the color synthesizing prism, the machine with this optical element The projection type image display device according to claim 1, wherein an arrangement that does not cause mechanical interference is selected. Arrangement of reflection type liquid crystal image modulation elements other than on the extension line of the reference optical axis immediately after the light synthesis of all colors among the plurality of reflection type liquid crystal image modulation elements arranged around the color synthesis prism system, and further the color synthesis The arrangement of the prism system itself is asymmetric with respect to the reference optical axis immediately after the color light synthesis,
In addition, it is possible to take two arrangements reversed around the reference optical axis immediately after the color light synthesis on the color synthesis plane,
The orientation of the arrangement of the reflective liquid crystal image modulation element and the color combining prism is selected and determined so as not to cause mechanical interference with an optical element such as a free-form reflecting surface constituting the projection optical system. 4. The projection type image display device according to claim 3, wherein When defining the Z axis along the reference optical axis immediately after the photosynthesis of all colors, with the image plane direction side being positive and the exit end face of the color synthesis prism closest to the image as the origin,
Of the plurality of reflection type liquid crystal image modulation elements arranged around the color synthesis prism system, the arrangement of the reflection type liquid crystal image modulation elements other than on the Z axis and the shape of the color synthesis prism system itself are as follows. Asymmetric about the axis,
In addition, it is possible to take two arrangements reversed around the Z axis on the color synthesis plane,
Among the optical elements constituting the projection optical system, when there is the optical element having a negative Z coordinate value, of the two arrangements of the image modulation element and the color synthesizing prism system, 4. The projection type image display apparatus according to claim 3, wherein an arrangement that does not cause mechanical interference is selected.   4. The projection type image display device according to claim 1, wherein the F number value of the illumination optical system in the short side direction of the image display surface of the image display device is larger than the other direction.

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