JP5706746B2 - Projection optical unit and projection display apparatus using the same - Google Patents

Description

  The present invention relates to, for example, a projection display apparatus that displays an image by projecting a color enlarged image on a screen, and more particularly, a projection that projects an image obliquely to the screen to form an enlarged image on the screen. The present invention relates to a type image display device and a projection optical unit used therefor.

  In a projection-type image display device that enlarges and displays a display element using a reflective or transmissive liquid crystal panel or a micromirror on a screen, it is possible to obtain an enlarged image of a sufficiently large size on the screen. Therefore, it is required to shorten the depth dimension of the apparatus. In order to realize such a requirement, there is provided a projection optical unit for enlarging / projecting the screen from an oblique direction (hereinafter referred to as “oblique projection”) as described in Patent Document 1 below. Are known. Further, as for optical adjustment when a curved mirror is used for such oblique projection, for example, the one described in Patent Document 2 below is known.

JP 2001-264627 A JP 2002-350774 A

  When oblique projection is performed, that is, when an image is projected at a predetermined angle (for example, from below the screen) with respect to the normal of the main plane of the screen, trapezoidal distortion and projection distances above and below the screen are added to the image projected on the screen. Aberration resulting from the difference occurs. In order to solve this problem, in Patent Document 1, trapezoidal distortion is corrected by a free-form surface mirror having a negative power disposed between the projection optical system and the screen. On the other hand, the aberration is corrected by moving the image display element parallel to the coaxial projection optical system or by tilting and moving the image display element relative to the non-axisymmetric projection optical system.

  However, in such aberration correction, the image on the screen may be shifted in the vertical direction, and a correction mechanism for that purpose is required. In addition, in the case of using a coaxial projection optical system, since a very wide angle of view is required, the number of lenses is increased and the aperture is also increased.

  Patent Document 2 discloses an adjustment method by moving a free-form surface mirror, but does not consider the aberration correction described above.

  As described above, in the prior art, the trapezoidal distortion and the aberration are corrected by different means, so that it is necessary to increase the necessary lens diameter and the number of lenses. That is, in the above-described prior art, the depth of the image display device and / or the height of the lower portion of the screen is reduced while satisfactorily reducing trapezoidal distortion and aberration in oblique projection (hereinafter referred to as “compact set reduction”). It was difficult.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a technique suitable for downsizing a set while displaying an image with reduced trapezoidal distortion and aberration. .

  In addition, the present invention provides a technique capable of facilitating manufacture or assembly adjustment of a compact set having the display characteristics as described above in a rear projection type image display apparatus.

  The present invention relates to a first optical system that includes a projection lens that includes at least one asymmetric lens having a concave surface in the light emitting direction and having a rotationally asymmetric shape with respect to the optical axis in an oblique projection. And a second optical system including at least one convex mirror in which at least a part of the reflective surface is convex in the reflection direction. The present invention is characterized in that the first optical system and the second optical system are mounted and fixed on a common optical system support unit.

  The asymmetric lens is a free-form surface lens in which the curvature of the portion through which the light beam toward the lower end of the screen passes is larger than the curvature of the portion through which the light beam toward the upper end of the screen passes. In addition, the convex mirror has a portion in which the curvature of the light reflecting downward toward the screen is larger than the curvature of the portion reflecting light upward in the screen or a portion reflecting the light downward in the screen Is a free-form curved mirror in which a convex shape is formed in the light reflection direction, and a portion that reflects light toward the upper side of the screen is a concave shape in the light reflection direction.

  Further, the present invention provides at least adjustment of an angle between an emission direction of light from an image generation source including an image display element and an optical axis of the projection lens, and adjustment of an optical distance between the image generation source and the projection lens. A mechanism for enabling one of the above, a mechanism for allowing the free-form curved mirror to rotate about the center of the free-form curved mirror, or a lens group having the largest positive power among the projection lenses Is provided with at least one of mechanisms for enabling movement in the optical axis direction of the projection lens.

  According to the present invention, it is possible to reduce the trapezoidal distortion and / or aberration caused by oblique projection of an image to obtain a good image and to make the set compact.

1 is a cross-sectional view showing an embodiment of a video display device according to the present invention. FIG. 3 is a cross-sectional view showing a basic configuration of a projection optical unit according to the present invention. The YZ sectional view showing the composition and optical path of one example concerning the present invention. XZ sectional drawing which shows the structure and optical path of one Example which concern on this invention. It is a figure showing the distortion performance of one Example which concerns on this invention. It is a figure showing the spot performance of one Example which concerns on this invention. FIG. 3 is a diagram showing an example of a projection optical unit according to the present invention. FIG. 5 is a diagram illustrating an example of an adjustment mechanism of the projection optical unit according to the present invention. FIG. 5 is a diagram illustrating an example of an adjustment mechanism of the projection optical unit according to the present invention. Sectional drawing of the projection optical unit which concerns on this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a partial sectional perspective view of a video display device according to the present invention. The video source 1 displays a small video. The image generation source 1 includes a light modulation element such as a reflective or transmissive liquid crystal panel or a display element having a plurality of minute mirrors. Further, the image generation source 1 may include a projection type cathode ray tube. The projection lens 2 that is a component of the first optical system projects the image of the image generation source 1 onto the screen 3. In the optical path from the projection lens 2 to the screen 3, a plane reflection mirror 4 is provided to reduce the depth of the image display device. A free-form surface mirror 5 that is a component of the second optical system is disposed between the projection lens 2 and the plane reflection mirror 4. The light from the projection lens is reflected by the free-form curved mirror 5 and guided to the plane reflecting mirror 4, and further reflected by the plane reflecting mirror 4 and guided to the screen 3. These elements are housed inside the housing 6 and fixed at predetermined positions. The video source 1, the projection lens 2, and the free-form surface mirror 5 are fixed and integrated with an optical system base 7. The features of the components of the projection optical unit according to the present invention will be described below with reference to FIG.

  FIG. 2 is a cross-sectional view showing a basic optical configuration of a rear projection display apparatus using the projection optical unit according to the present embodiment. FIG. 2 shows the configuration of the optical system as a YZ section in an XYZ orthogonal coordinate system. Here, it is assumed that the origin of the XYZ orthogonal coordinate system is the center of the display screen of the video display element 11 constituting the video generation source 1, and the Z axis is parallel to the normal line of the screen 3. The Y axis is parallel to the short side of the screen of the screen and is assumed to be equal to the horizontal direction of the screen. The X axis is parallel to the long side of the screen and is equal to the vertical direction of the screen.

As shown in FIG. 2, the light emitted from the image display element 11 is a front group composed of a plurality of refractive lenses having a rotationally symmetric surface shape among the projection lenses 2 composed of a transmissive lens group. Pass through 12. Thereafter, the light passes through a rear group 13 of a projection lens including a lens (hereinafter, referred to as “free-form surface lens”) having at least one surface having a rotationally asymmetric free-form shape. Thereafter, the light is reflected by at least one reflecting mirror (hereinafter referred to as a free-form curved mirror) 5 having a rotationally asymmetric free-form reflecting surface . Then, the light is incident on the screen 3 after being reflected by the plane reflecting mirror 4.

  Here, when the image display element 11 is the light modulation element, an illumination system such as a lamp for irradiating the light modulation element is necessary, but the illustration thereof is omitted. Further, the video display element 11 may be a system that synthesizes a plurality of images like a so-called three-plate type. The illustration of the synthesizing optical system such as a synthesizing prism required in that case is also omitted.

  In FIG. 2, since the length of the projection lens 2 is long, it may be seen that the position of the image display element 11 is far from the normal direction of the screen and the depth becomes large. However, in the present embodiment, a mirror (between the free-form surface mirror 5 and the rear group 13 of the projection lens 2, between the front group 12 and the rear group 13 of the projection lens 2, or in the middle of the front group 12). (Not shown). As a result, the optical axis of the projection lens 2 can be bent in a direction substantially perpendicular to the cross section shown in FIG.

  In the present embodiment, as shown in FIG. 2, the center of the display screen of the image display element 11 is disposed on the optical axis of the projection lens 2. Accordingly, a light beam 21 that exits from the center of the display screen of the image display element 11 and passes through the center of the entrance pupil of the projection lens 2 toward the screen center on the screen 3 travels substantially along the optical axis of the projection lens. (Hereafter, this is called the screen center ray). The center ray of the screen is reflected at a point P2 on the reflection surface of the free-form curved mirror 5 and then reflected at a point P5 on the plane reflection mirror 4 so that the normal line of the screen appears at a point P8 at the center of the screen on the screen 3. 8 is incident with a predetermined angle (ie, obliquely). This angle is hereinafter referred to as “oblique incident angle” and is represented by θs.

  This means that the light beam that has passed along the optical axis of the projection lens 2 is incident on the screen obliquely, and the optical axis of the projection lens 2 is substantially provided obliquely with respect to the screen. Will be. When obliquely incident on the screen by such a method, various aberrations that are not rotationally symmetric with respect to the optical axis occur in addition to the so-called trapezoidal distortion in which the projected rectangular shape becomes a trapezoid. In the present embodiment, these are corrected by the rear group 13 of the projection lens 2 and the reflecting surface of the second optical system.

  In the cross section shown in FIG. 2, the light is emitted from the lower end of the screen of the image display element 11 through the lower end of the screen and the center of the entrance pupil of the projection lens 2, and enters the corresponding point P9 on the upper end of the screen on the screen. Let the light ray to be the light ray 22. Further, a light beam emitted from the upper end of the screen of the image display element 11 through the upper end of the screen and the center of the entrance pupil of the projection lens 2 and incident on the corresponding point P7 on the lower end of the screen on the screen is a light beam 23. To do. Referring to FIG. 2, the optical path length from the point P3 through the point P6 to the point P9 is longer than the optical path length from the point P1 through the point P4 to the point P7. This means that the image point P9 on the screen is farther than the image point P7 when viewed from the projection lens 2. Therefore, an object point corresponding to the image point P9 on the screen (a point on the display screen) is closer to the projection lens 2, and an object point corresponding to the image point P7 is closer to the projection lens 2. For example, the tilt of the image plane can be corrected. For this purpose, the normal vector at the center of the display screen of the video display element 1 is inclined with respect to the optical axis of the projection lens 2. Specifically, the normal vector may be inclined so as to be directed toward the screen in the YZ plane. A method of inclining the object plane to obtain an image plane inclined with respect to the optical axis is known. However, at an angle of view of a practical size, the image plane due to the inclination of the object plane is asymmetrically deformed with respect to the optical axis, and correction is difficult with a rotationally symmetric projection lens. In the present embodiment, since a rotationally asymmetric free curved surface is used, it is possible to cope with asymmetrical deformation of the image plane. For this reason, tilting the object plane can greatly reduce the distortion of the lower-order image plane, which is effective in assisting correction of aberrations by a free-form surface.

Next, the operation of each optical element will be described. The projection lens 2 that is the first optical system is a main lens whose front group 12 projects the display screen of the video display element 11 onto the screen 3, and corrects basic aberrations in the rotationally symmetric optical system. . The rear group 13 of the projection lens 2 includes a rotationally asymmetric free-form surface lens. Here, in the present embodiment, the free-form surface lens is curved so as to face the concave with respect to the light emitting direction. The curvature of the portion of the free-form surface lens through which the light beam toward the lower end of the screen 3 passes is made larger than the curvature of the portion through which the light beam toward the upper end of the screen passes. The second optical system has a free-form surface mirror having a rotationally asymmetric free-form surface shape. Here, in the present embodiment, the free-form curved mirror is a rotationally asymmetric convex mirror that is curved so that a part thereof is convex with respect to the light reflection direction. Specifically, the curvature of the portion of the free-form curved mirror that reflects light traveling downward of the screen 3 is made larger than the curvature of the portion reflecting light traveling upward of the screen. In addition, the portion of the free-form curved mirror that reflects light traveling downward from the screen has a convex shape in the light reflecting direction, and the portion that reflects light traveling upward from the screen is concave in the light reflecting direction. You may make it do. By the action of the free-form surface lens and the free-form surface mirror, correction of aberrations caused by oblique incidence is mainly performed. That is, in the present embodiment, the second optical system mainly corrects trapezoidal distortion, and the rear group 13 of the projection lens 2 that is the first optical system mainly corrects asymmetric aberrations such as distortion of the image plane. .

  As described above, in this embodiment, the first optical system includes at least one rotationally asymmetric free-form surface lens, and the second optical system includes at least one rotationally asymmetric free-form surface mirror. This makes it possible to correct both trapezoidal distortion and aberration caused by oblique projection.

The optical axis direction between the coordinate origin of the reflecting surface of the second optical system (here, the coordinates of the position where the central ray of the screen is reflected) and the lens surface closest to the screen side of the front group 12 of the projection lens 2 Is preferably set to be at least five times the focal length of the front group 12 of the projection lens 2. Accordingly, trapezoidal distortion and aberration can be more effectively corrected by the reflecting surface of the second optical system, and good performance can be obtained.

  On the other hand, a free-form curved mirror becomes very difficult to manufacture as its size increases, so it is important to make it a predetermined size or less. For example, since the size of the flat reflecting mirror 4 shown in FIG. 2 is about 70% or more of the screen screen, a large-screen rear projector such as a 50-inch or larger has a size exceeding 500 mm. Manufacturing becomes very difficult. Therefore, it is not appropriate to make the flat reflecting mirror a free curved surface in the rear projector. Therefore, in the present embodiment, the size of the free-form surface mirror 5 is made smaller than the size of the plane reflection mirror 3, and the free reflection mirror 5 is disposed below the plane reflection mirror 3. Then, the image light from the projection lens 2 is reflected on the free-form surface mirror 5 and the plane reflection mirror in this order and projected onto the screen 3.

  The above description is based on the embodiment shown in FIG. However, the same idea as in the above-described embodiment can be applied even when the direction of bending of the optical path by the mirror is in the plane including the long side of the screen, contrary to FIG.

  Thereby, in the projection lens 2 having a refracting surface, it is possible to correct trapezoidal distortion due to oblique incidence without causing decentration of the lens, an increase in the lens diameter, and without increasing the number of lenses. Furthermore, it is possible to realize a projection optical unit that has a small depth and is easy to manufacture. Furthermore, according to the present embodiment, a compact set in which the depth and the height of the lower portion of the screen are reduced can be provided, and an optical system that can be easily manufactured with a small free-form curved mirror can be provided.

  Hereinafter, examples of the optical system according to the present invention will be described with reference to specific numerical values. One of the numerical examples of the present invention will be described with reference to FIGS. 3 to 6 and Tables 1 to 4. FIG.

  3 and 4 show ray diagrams of the optical system according to the present invention based on the first numerical example. In the XYZ orthogonal coordinate system described above, FIG. 3 shows the structure in the YZ section, and FIG. 4 shows the structure in the XZ section. FIG. 1 shows an example in which a bending mirror is installed in the middle of the front group 12 of the projection lens 2 and the optical path is bent once in the X-axis direction. In FIG. 3, the bending mirror is omitted, and the optical system is shown expanded in the Z-axis direction. FIG. 4 shows the optical system in a state where the optical path is bent including the folding mirror. The bending mirror has a certain degree of arbitrary installation position and angle, and does not affect the function of each optical element. Accordingly, in the following description, the bending mirror is omitted.

  In the present example, the light emitted from the image display element 11 displayed on the lower side of FIG. 3 is a front group composed of only lenses having only a rotationally symmetric surface among the projection lenses 2 including a plurality of lenses. 12 is passed. Then, the light passes through the rear group 13 including a rotationally asymmetric free-form surface lens, and is reflected by the reflection surface of the free-form surface mirror 5 as the second optical system. The reflected light is reflected by the plane reflecting mirror 4 and then enters the screen 3.

  Here, the front group 12 of the projection lens 2 is composed of a plurality of lenses each having a rotationally symmetric refracting surface, and four of the refracting surfaces are rotationally symmetric aspherical surfaces, and the others are spherical surfaces. It is. The rotationally symmetric aspherical surface used here is expressed by the following equation using a local cylindrical coordinate system for each surface.

ここで、ｒは光軸からの距離であり、Ｚはサグ量を表している。また、ｃは頂点での曲率、ｋは円錐定数、ＡからＪはｒのべき乗の項の係数である。

Here, r is the distance from the optical axis, and Z represents the sag amount. C is the curvature at the apex, k is the conic constant, and A to J are coefficients of the power of r.

  The free-form surface lens in the rear group 13 of the projection lens 2 uses a local orthogonal coordinate system (x, y, z) whose origin is the surface vertex of each surface, and includes the following equations including X and Y polynomials. Represented.

ここで、ＺはＸ、Ｙ軸に垂直な方向で自由曲面の形状のサグ量を表わしており、ｃは頂点での曲率、ｒはＸ、Y軸の平面内での原点からの距離、ｋは円錐定数、Ｃ（ｍ、ｎ）は多項式の係数である。

Here, Z represents the sag amount of the shape of the free-form surface in the direction perpendicular to the X and Y axes, c is the curvature at the vertex, r is the distance from the origin in the plane of the X and Y axes, k Is a conic constant and C (m, n) is a coefficient of a polynomial.

  Table 1 shows numerical data of the optical system according to the present example. In Table 1, S0 to S23 correspond to the codes S0 to S23 shown in FIG. Here, S0 indicates the display surface of the image display element 11, that is, the object surface, and S23 indicates the reflection surface of the free-form curved mirror 5. S24, which is not shown in FIG. 10, shows the incident surface of the screen 3, that is, the image surface. In FIG. 10, the upper diagram shows a vertical sectional view of the first and second optical systems according to this embodiment, and the lower diagram shows a horizontal sectional view of the optical system.

  In Table 1, Rd is the radius of curvature of each surface. In FIG. 3, when the center of curvature is on the left side of the surface, it is expressed as a positive value, and in the opposite case, it is expressed as a negative value. In Table 1, TH is the inter-surface distance, and indicates the distance from the apex of the lens surface to the apex of the next lens surface. When a next lens surface is located on the left side in FIG. 3 with respect to a certain lens surface, the inter-surface distance is represented by a positive value, and when located on the right side, it is represented by a negative value. Furthermore, in Table 1, S5, S6, S17, and S18 are rotationally symmetric aspherical surfaces, and in Table 1, an asterisk (*) is added next to the surface number for easy understanding. Table 2 shows the coefficients of these four aspheric surfaces.

  In this embodiment, the object surface that is the display screen of the image display element 11 is inclined by −1.163 degrees with respect to the optical axis of the projection lens 2. The direction of inclination is represented by a positive value in the direction in which the normal of the object surface rotates counterclockwise in the cross section of FIG. Therefore, in this embodiment, the object surface is inclined 1.163 degrees in the clockwise direction from the position perpendicular to the optical axis of the projection lens 2 in the cross section of FIG.

The free-form surface mirror 5 of S23 has the origin of its local coordinates on the optical axis of the projection lens 2. The normal line at the origin of the local coordinates of the free-form surface mirror 5, that is, the Z-axis is inclined by 29 degrees from a position parallel to the optical axis of the projection lens 2. As in the case of the object surface, the direction of inclination is positive in the direction of rotating counterclockwise in the cross section of FIG. 3, and is therefore inclined counterclockwise. As a result, the screen center ray that has exited from the center of the screen of the image display element 11 and has traveled substantially along the optical axis of the projection lens 2 is reflected at S23 and then has an inclination angle of 2 with respect to the optical axis of the projection lens 2. Proceed in a direction tilted by 58 degrees. Here, as the coordinate origin in S23, the double inclined direction in S23 inclination angle against the optical axis of the projection lens 2, and a new optical axis after the reflection, the subsequent surface is disposed on the optical axis Shall. The surface spacing value −400 shown in S23 of Table 1 is that the next S24 is on the right side of S23, and the origin of the local coordinates is located at a distance of 400 mm along the optical axis after reflection. Is shown. The following planes are also arranged according to the same rules.

  Table 4 shows the state of inclination or decentering of the local coordinate system of each surface in this example. In Table 4, the inclination angle and the value of eccentricity are shown on the right side of the surface number, ADE is the magnitude of the inclination in the plane parallel to the cross section of FIG. 3, and the display rule is as shown above. is there. YDE is the magnitude of the eccentricity, and the eccentricity is set in a direction parallel to the cross section of FIG. 3 and perpendicular to the optical axis, and the downward eccentricity in the cross section of FIG. 3 is positive. In this embodiment, YDE is set to 0 (that is, no eccentricity).

  In the present invention, the inclination and decentering of all optical elements are set in a direction in a cross section parallel to the illustrated cross section.

  From Tables 1 and 3, it can be seen that the curvature c and the conic coefficient k are 0 in this embodiment. Trapezoidal distortion due to oblique incidence occurs extremely large in the direction of oblique incidence, and the amount of distortion is small in the direction perpendicular thereto. Therefore, a significantly different function is required between the direction of oblique incidence and the direction perpendicular thereto, and asymmetric aberrations are excellent by not using the curvature c and the conic coefficient k that function in all directions in rotational symmetry. Can be corrected.

上記表１〜４の数値は、物面上１６×９の範囲の映像を像面上１４５２．８×８１７．
２の大きさに投写する場合の一例である。そのときの図形歪を図５に示す。図５の縦方向は図３の上下方向であり、Ｙ軸の方向である。図５の横方向はスクリーン上でＹ軸と直交する方向であり、図の長方形の中央が画面の中央である。図は画面の縦方向を４分割、横方向を８分割した直線の曲がりの状態を表示して図形歪の様子を示している。

The numerical values in Tables 1 to 4 above represent images in the range of 16 × 9 on the object plane and 1452.8 × 817.
This is an example of projecting to a size of 2. The graphic distortion at that time is shown in FIG. The vertical direction in FIG. 5 is the vertical direction in FIG. 3 and is the Y-axis direction. The horizontal direction in FIG. 5 is a direction perpendicular to the Y axis on the screen, and the center of the rectangle in the figure is the center of the screen. The figure shows the state of figure distortion by displaying the state of straight line bending in which the vertical direction of the screen is divided into four and the horizontal direction is divided into eight.

  A spot diagram of this numerical example is shown in FIG. In FIG. 6, on the display screen of the video display element 11, the values of the X and Y coordinates are (8, 4.5), (0, 4.5), (4.8, 2.7), (8, 0), (0, 0), (4.8, -2.7), (8, -4.5), and (0, -4.5) from the top of the spot diagram of the luminous flux emitted from eight points Shown in order. The unit is mm. The horizontal direction of each spot diagram is the X direction on the screen, and the vertical direction is the Y direction on the screen. Thus, both maintain good performance.

  The optical unit according to the embodiment of the present invention has been described above. This embodiment is different from Patent Document 1 described in the related art in that the rear group 13 of the projection lens 2 is configured by a lens having a free curved surface shape that is not rotationally symmetric, and the second optical system is a free curved surface shape that is not rotationally symmetric. It is to be composed of a reflective surface having Furthermore, these roles are different, the second optical system mainly corrects trapezoidal distortion, and the rear group 13 of the projection lens 2 which is the first optical system mainly corrects asymmetric aberrations such as image plane distortion. To do.

  Therefore, in this embodiment, focusing at the time of assembly adjustment cannot be performed by moving the lens group of the imaging optical system along the axial direction as in the prior art.

  FIG. 7 is a view showing a lens group of the projection lens 2 constituting the projection optical unit according to the present embodiment, and a lens holding member for holding the lens group is omitted from the drawing. The front group 12 of the projection lens 2 is a main lens for projecting the display screen of the image display element 11 onto a screen (not shown), and is composed of a plurality of refractive lenses having a rotationally symmetric surface shape, and is rotationally symmetric. To correct basic aberrations in simple optical systems. The rear group 13 of the projection lens 2 includes a rotationally asymmetric free-form surface lens, and mainly corrects aberrations caused by oblique incidence.

  As is apparent from FIG. 7, in the present embodiment, at least one free-form surface lens is curved so as to face a concave with respect to the light emitting direction. Then, the portion of the free-form surface lens where the light beam toward the lower end of the screen 3 passes (here, the lower side of the free-form surface lens) passes through the portion of the free-form surface lens (here, the free-form surface lens). Is larger than the curvature of the upper side). In the present embodiment, the rear group 13 of the projection lens 2 is configured by combining two free-form surface lenses.

  In this embodiment, the bending mirror 14 is provided in the middle of the front group 12. In the prior art, in order to move the lens group of the imaging optical system along the axial direction, a groove is obliquely formed in the lens holding member (lens barrel) and the internal lens group is rotated along the groove. It was. In this embodiment, since a rotationally asymmetric free-form surface lens is used, the rear group 13 having this rotationally asymmetric free-form surface lens cannot be rotated. Therefore, in the present embodiment, as described above, the lens group cannot be moved along the optical axis direction by the method according to the related art. On the other hand, since the front group 12 of the projection lens 2 according to the present embodiment is composed of a rotationally symmetric lens group, the optical image is not deformed even when the front group 12 is rotated. Therefore, it is possible to focus by moving the lens group of the front group 12 along the axial direction. However, in such focusing, the position of the light ray incident on the incident surface of the rear group 13 for performing aberration correction changes. If such a change in the position of the light beam occurs, it may be impossible to correct aberrations favorably in the rear group 13. Therefore, in this embodiment, the positions of the front group 12 and the rear group 13 of the projection lens 2 are fixed, and the position and / or inclination of the image display element 11 installed in front of the projection lens 2 is changed during assembly adjustment. The focus is adjusted.

FIG. 8 shows an example of an optical unit having such an adjustment mechanism . In FIG. 8, the image generation source 1 shows a case where a three-plate transmission type liquid crystal panel is used as an example, but a reflection type liquid crystal panel may be used. Alternatively, a display element including a plurality of minute mirrors may be used. In the projection lens 2, the bending mirror 14 shown in FIG. 7 is provided in the middle of the front group 12. The free-form surface mirror 5 is fixed and integrated with the image generation source 1 and the projection lens 2 to an optical system base 7 that is an optical system support. Among those fixed to the optical system base 7, the projection lens 2 is fixed and integrated rigidly. On the other hand, the image generation source 1 is adjusted by the adjusting mechanism 15 at least in the vertical direction (with the axis parallel to the X axis as the rotation center) and in the front-rear direction (the Z axis direction), that is, on the output side of the image generation source 1. Is fixed to the optical system base 7 so that the distance between the projection lens 2 and the front group 12 of the projection lens 2 can be adjusted. The free-form surface mirror 5 is fixed by a support 16 provided on the optical system base 7 so as to be rotatable about the approximate center of the free-form surface mirror 5 as a central axis. In FIG. 8, the rotation center pin 17 sandwiches the center of the free-form curved mirror 5 from both ends of the pin 17 so that the free-form curved mirror 5 can rotate about this. The lower end of the free-form curved mirror 5 is coupled to a fixing wing nut 19 via a rotation guide groove 18. Then, the free curved surface mirror 5 can be rotated about the pin 17 as the central axis by sliding the lower end of the free curved surface mirror 5 along the rotation guide groove 18 using the fixing wing nut 19. As a result, the angle formed by the normal line at the center of the reflecting surface of the free-form curved mirror 5 and the optical axis of the projection lens 2, that is, the tilt angle of the free-form curved mirror 5 is adjusted.

  In this example, three transmission type liquid crystal panels 31 corresponding to red, green, and blue are used as the image generation source 1. Images from these liquid crystal panels are synthesized by the cross dichroic prism 32.

  It is also possible to focus the video corresponding to red, green and blue by moving each liquid crystal panel 31 independently. However, in this case, the physical quantity to be corrected increases, such as projection display alignment, pixel alignment, and field aberration correction. Therefore, it is difficult to perform all adjustments only by moving each liquid crystal panel 31. Therefore, in the present embodiment, the movement of each liquid crystal panel 31 is used for pixel alignment, and the adjustment mechanism 15 that holds the image generation source 1 is used for alignment for projection display and for correction of field aberration. Separated from 31 adjustments. The distortion aberration can be corrected by rotating the free-form surface mirror 5. In the present embodiment, the correction mechanism is separated according to the physical quantity to be corrected in this way, so that the image can be easily focused.

  The reason why the correction mechanism can be separated as described above is as follows. That is, in this embodiment, (1) the front group 12 of the projection lens 2 is a main lens for projecting the display screen of the liquid crystal panel 31 onto the screen 3, and the front group 12 is a basic in a rotationally symmetric optical system. (2) The rear group 13 of the projection lens 2 is a rotationally asymmetric free-form surface lens, and is mainly configured to correct field aberrations; (3) the free-form surface mirror 5 , Mainly configured to correct distortion; thereby enabling the correction mechanism as described above.

  Another embodiment of the projection optical unit according to the present invention is shown in FIG. The difference from FIG. 8 is that a lens group (not shown; hereinafter referred to as a power lens) having the largest positive power in the front group of the projection lens 2 can be moved in the axial direction. . In order to move the power lens along the axial direction, the lens moving guide groove 36 is obliquely inserted into the lens holding member (lens barrel) and the internal lens group is rotated along the groove. In FIG. 9, the lens fixing wing nut 37 is coupled to the power lens or an element for holding the lens. By sliding the lens along the guide groove 36, the power lens is moved along its optical axis. Let That is, in this example, the guide groove 36 and the lens fixing wing nut 37 constitute an adjusting mechanism for focusing. By adding this function to the projection lens 2, the adjustment mechanism 35 fixed to the optical system base 7 so that the image source 1 can be adjusted can be omitted. Further, when the power lens adjusting mechanism is used in the example of FIG. 8, at least the adjustment of the distance in the front-rear direction (Z-axis direction) can be omitted.

  As described above, according to the present embodiment, it is possible to realize a rear projection color image display apparatus that can reduce the depth size of a set and can be easily assembled and adjusted. Further, if the above-described optical system is used to remove the plane reflecting mirror and house the image display element to the free-form surface mirror in one device, a front projection display device is obtained. Therefore, a compact front projection apparatus with a very short distance from the apparatus to the screen can be realized.

DESCRIPTION OF SYMBOLS 1 ... Image generation source, 2 ... Projection lens, 3 ... Screen, 4 ... Plane reflection mirror, 5 ... Free-form surface mirror, 6 ... Housing | casing, 11 ... Image display element, 12 ... Projection lens front group, 13 ... After projection lens Group, 14 ... bending mirror, 15, 35 ... adjusting mechanism 16 ... support, 17 ... pin for rotation center, 18 ... guide groove for rotating free-form mirror, 36 ... guide groove for lens movement.

Claims (20)

In a projection display device that projects obliquely on a screen,
From the light source to the screen,
An image display element;
A projection optical system for enlarging and projecting the image displayed on the image display element;
A reflection mirror that reflects the light beam from the projection optical system to the screen;
The projection optical system is
A front group of a coaxial optical system composed of a plurality of lenses having a rotationally symmetric shape;
A rear group having at least one free-form surface lens having a rotationally asymmetric free-form surface shape and correcting asymmetric aberrations,
The reflecting mirror has a rotationally asymmetric free-form reflecting surface, corrects trapezoidal distortion,
The image display element, the projection optical system, and the reflection mirror are each fixed to a common optical system base,
The free-form surface lens has a surface with a concave in the light emitting direction,
The reflection mirror has a surface with a convex in the light reflection direction,
In the free-form surface lens, the curvature of the part through which the light going downward of the screen passes is larger than the curvature of the part through which the light going upward of the screen passes,
The projection display apparatus according to claim 1, wherein a curvature of a portion of the reflection mirror that reflects light directed downward of the screen is larger than a curvature of a portion of the reflection mirror that reflects light directed upward of the screen. In a projection display device that projects obliquely on a screen,
From the light source to the screen,
An image display element;
A projection optical system for enlarging and projecting the image displayed on the image display element;
A reflection mirror that reflects the light beam from the projection optical system to the screen;
The projection optical system is
A front group of a coaxial optical system composed of a plurality of lenses having a rotationally symmetric shape;
A rear group having at least one free-form surface lens having a rotationally asymmetric free-form surface shape and correcting asymmetric aberrations,
The reflecting mirror has a rotationally asymmetric free-form reflecting surface, corrects trapezoidal distortion,
The image display element, the projection optical system, and the reflection mirror are each fixed to a common optical system base,
The free-form surface lens has a surface with a concave in the light emitting direction,
In the free-form surface lens, the curvature of the part through which the light going downward of the screen passes is larger than the curvature of the part through which the light going upward of the screen passes ,
The reflection mirror has a convex shape in the light reflection direction at a portion that reflects light below the screen, and a concave shape in the light reflection direction at a portion that reflects the light upward toward the screen. None have projection display device comprising a Turkey. A mechanism for moving each of the plurality of liquid crystal panels constituting the video display element;
A mechanism that performs at least one of adjustment of an angle between the optical axis of the video display element and the optical axis of the front group, and adjustment of an optical distance between the video display element and the front group;
A mechanism for adjusting the angle of the reflection mirror,
The projection image display apparatus according to claim 1, wherein the projection optical system is rigidly fixed to the optical system base.   And a mechanism for adjusting at least one of an angle between an optical axis of the image display element and the optical axis of the front group and an adjustment of an optical distance between the image display element and the front group. Item 3. The projection display apparatus according to Item 1 or 2. The projection display apparatus according to claim 4, further comprising a mechanism for allowing the reflection mirror to rotate about a substantially center of the reflection mirror as a central axis.   The projection display apparatus according to claim 1, further comprising a mechanism for enabling a lens group having the largest positive power in the front group to be movable in an optical axis direction of the front group.   The distance in the optical axis direction between the coordinate origin of the reflecting surface of the reflecting mirror and the lens surface closest to the screen among the front group is 5 times or more the focal length of the front group. The projection type image display device described in 1.   The bending mirror which bends an optical path between any of the plurality of lenses in the front group, between the front group and the rear group, or between the rear group and the reflection mirror. Projection display device.   The projection display apparatus according to claim 1, wherein a center position of the image display element is disposed on the optical axis of the front group.   The projection display apparatus according to claim 1, further comprising a flat mirror for reflecting the light reflected by the reflection mirror and guiding the light to the screen. In an optical unit used in a projection display apparatus that projects obliquely on a screen,
From the light source to the screen,
An image display element;
A projection optical system for enlarging and projecting the image displayed on the image display element;
A reflection mirror that reflects the light beam from the projection optical system to the screen, and the projection optical system includes:
A front group of a coaxial optical system composed of a plurality of lenses having a rotationally symmetric shape;
A rear group having at least one free-form surface lens having a rotationally asymmetric free-form surface shape and correcting asymmetric aberrations,
The reflecting mirror has a rotationally asymmetric free-form reflecting surface, corrects trapezoidal distortion,
The image display element, the projection optical system, and the reflection mirror are each fixed to a common optical system base,
The free-form surface lens has a surface with a concave in the light emitting direction,
The reflection mirror has a surface with a convex in the light reflection direction,
In the free-form surface lens, the curvature of the part through which the light going downward of the screen passes is larger than the curvature of the part through which the light going upward of the screen passes,
The optical unit according to claim 1, wherein a curvature of a portion of the reflection mirror that reflects light directed downward of the screen is larger than a curvature of a portion of the reflection mirror that reflects light directed upward of the screen. In an optical unit used in a projection display apparatus that projects obliquely on a screen,
From the light source to the screen,
An image display element;
A projection optical system for enlarging and projecting the image displayed on the image display element;
A reflection mirror that reflects the light beam from the projection optical system to the screen, and the projection optical system includes:
A front group of a coaxial optical system composed of a plurality of lenses having a rotationally symmetric shape;
A rear group having at least one free-form surface lens having a rotationally asymmetric free-form surface shape and correcting asymmetric aberrations,
The reflecting mirror has a rotationally asymmetric free-form reflecting surface, corrects trapezoidal distortion,
The image display element, the projection optical system, and the reflection mirror are each fixed to a common optical system base,
The free-form surface lens has a surface with a concave in the light emitting direction,
In the free-form surface lens, the curvature of the part through which the light going downward of the screen passes is larger than the curvature of the part through which the light going upward of the screen passes,
The reflection mirror has a convex shape in the light reflection direction at a portion that reflects light below the screen, and a concave shape in the light reflection direction at a portion that reflects the light upward toward the screen. An optical unit characterized by A mechanism for moving each of the plurality of liquid crystal panels constituting the video display element;
A mechanism that performs at least one of adjustment of an angle between the optical axis of the video display element and the optical axis of the front group, and adjustment of an optical distance between the video display element and the front group;
A mechanism for adjusting the angle of the reflection mirror,
The optical unit according to claim 11 or 12, wherein the projection optical system is rigidly fixed to the optical system base.   And a mechanism for adjusting at least one of an angle between an optical axis of the image display element and the optical axis of the front group and an adjustment of an optical distance between the image display element and the front group. Item 13. The optical unit according to Item 11 or 12.   The optical unit according to claim 14, further comprising a mechanism for enabling the reflection mirror to rotate about a substantially center of the reflection mirror as a central axis.   The optical unit according to claim 11 or 12, further comprising a mechanism for allowing a lens group having the largest positive power in the front group to move in the optical axis direction of the front group.   The distance in the optical axis direction between the coordinate origin of the reflecting surface of the reflecting mirror and the lens surface closest to the screen among the front group is 5 times or more the focal length of the front group. The optical unit described in 1.   The bending mirror which bends an optical path between any of a plurality of lenses in the front group, between the front group and the rear group, or between the rear group and the reflection mirror is further provided. The optical unit described in 1.   The optical unit according to claim 11, wherein a center position of the image display element is arranged on the optical axis of the front group.   The optical unit according to claim 11 or 12, further comprising a plane mirror for reflecting the light reflected by the reflection mirror and guiding it to the screen.

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