JP2012215909A - Projection type video display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type video display apparatus that allows a wide angle, minimizes deformation despite alteration of distance of a projection surface (a screen) and the apparatus is easily manufactured.SOLUTION: A projection type video display apparatus magnifies video displayed on a video display element 1 and projects the video onto a projection surface. The projection type video display apparatus comprises: lens optical systems 2 and 3 comprising a plurality of projection lenses; and a reflection mirror 5 composing a reflecting system that reflects light emitted from the lens optical systems and projects the light onto a screen 5 at a slant. A rear lens group 3 composing the lens optical systems comprises a plurality of lenses 31 and 32 having a shape of free curved faces that are asymmetrical in rotation. The reflection mirror 5 comprises a projection optical unit composed of a convex reflection mirror, part of which is projecting in a reflecting direction and asymmetrical in rotation.

Description

  The present invention relates to a projection-type image display apparatus that displays an image by enlarging an image of an image display element and projecting it on a projection surface such as a screen, and in particular, a projection-type image suitable for a front-transmission-type image display apparatus The present invention also relates to a display device and a projection optical unit therefor.

  In a color image display device that projects an image of an image display element on a screen (transmission surface) through a projection optical unit composed of a plurality of lenses, the enlarged image has a sufficiently large size on the screen. Is required without distortion. In order to realize this, as described in Patent Documents 1 and 2 below, for example, the projection screen is shifted in a direction perpendicular to the optical axis of the projection system, and is also predetermined with respect to the optical axis of the projection system. There is already known a projection apparatus or an optical system that enlarges and projects an image in an oblique direction with respect to a screen using an additional optical system arranged at an angle of. The additional optical system (afocal converter) referred to here is an optical system that has the effect of converting the size of the projected image, and corrects / reduces the distortion of the projected image due to the transmission from the oblique direction to the screen. Thus, a rectangular projection image is obtained.

  Reflective imaging that uses a plurality of reflecting mirrors (reflection optical elements) instead of the lens (transmission optical elements) and projects an image of the image display element on a screen (transmission surface). The optical system is already known, for example, from Patent Document 3 below.

Japanese Patent Laid-Open No. 5-134213 JP 2000-162544 A JP 2004-157560 A

  That is, when an image is projected from an oblique direction with respect to the screen, so-called trapezoidal distortion occurs in the projected image. In order to solve this problem, the projection optical unit described in Patent Document 1 has a configuration in which trapezoidal distortion is suppressed by decentering an additional optical system (afocal converter) disposed on the screen side. However, it is difficult to widen the angle of a lens constituting such a decentered optical system because the magnification is low. Therefore, in order to obtain a projection image with a necessary magnification, the distance from the transmission device to the screen becomes large. In addition, the distance between the projection screen and the projection system also increases, and there is a problem that the entire apparatus becomes large (particularly, the length of the optical unit in the optical axis direction). In addition, an additional optical system having a large aperture is required as the lens constituting the above-described decentered additional optical system, which causes an increase in the cost of the transmission optical unit.

  Also in the projection optical unit described in Patent Document 2, as in Patent Document 1, since the magnification is low, it is difficult to widen the angle, and the lenses to be used must be individually decentered. In addition, it is difficult to manufacture, and an additional optical system having a large aperture is required, which causes an increase in the cost of the transmission optical unit.

  On the other hand, in the reflective imaging optical system described in Patent Document 3, imaging optics is used by using a reflective optical system (reflecting mirror) instead of the conventional transmissive imaging optical system (lens system). It is intended to suppress the enlargement of the system and widen the angle of view. However, since the amount of decentering (deflection) of light at the reflector is large, it is difficult to arrange a plurality of reflectors at an accurate position including the inclination angle in the apparatus. Since the tilt angle of the reflecting mirror easily changes, there is still a problem that its manufacture is extremely difficult.

  Therefore, in the present invention, in view of the above-described problems in the prior art, a projection-type image display apparatus that enables a wide angle without enlarging the apparatus and is relatively easy to manufacture, and a projection optical unit therefor And its purpose is to provide That is, it is an object of the present invention to provide a technique suitable for making the projection display device itself more compact without requiring an additional optical system having a large aperture and without causing trapezoidal distortion. .

  According to the present invention, in order to achieve the above object, first, a projection type video display including a video display element and a projection optical unit that enlarges and projects the video displayed on the video display element onto a projection plane. The projection optical unit includes a lens group that is disposed adjacent to the image display element and includes a plurality of projection lenses; and reflects light emitted from the lens group. A reflection mirror that projects the image on the projection surface at an angle, and the lens group includes a plurality of lenses that are disposed between the image display element and the reflection mirror and have a rotationally asymmetric free-form surface. In addition, there is provided a projection display apparatus in which a part of the reflection mirror that reflects the light emitted from the lens group is a rotationally asymmetric convex reflection mirror that is convex in the reflection direction.

  According to the present invention, in the projection display apparatus, a part of the plurality of lenses having a rotationally asymmetric free-form surface constituting the rear lens group constituting the projection optical unit is formed on the projection surface. It is preferable that the curvature of the portion through which the light ray incident on the lower end portion passes is different from the curvature of the portion through which the light ray incident on the upper end portion of the projection plane passes, or the projection optical unit constituting the projection optical unit The rear lens group preferably includes at least one rotationally symmetric spherical lens and at least one rotationally symmetric aspherical lens in addition to the asymmetric lens. Alternatively, in the convex reflecting mirror constituting the projection optical unit, the curvature of the portion that reflects the light incident on the lower end of the projection surface is larger than the curvature of the portion that reflects the light incident on the upper end of the screen. Preferably it is formed.

Furthermore, according to the present invention, in the projection display apparatus, the convex reflection mirror constituting the projection optical unit has a shape in which a portion that reflects light incident on a lower end of the screen has a convex shape with respect to the reflection direction. Therefore, it is preferable that the portion that reflects the light beam incident on the upper end of the screen has a concave shape in the reflection direction, or in the projection optical unit, the screen center light beam and the screen center light beam In a plane including the normal line of the projection surface, the distance of the path of the light beam incident from the reflection surface of the reflection mirror to the upper end of the projection surface is L1, and the distance from the reflection surface of the reflection mirror to the lower end of the projection surface L2 is the distance of the path of the ray to be emitted, Dv is the distance from the upper end to the lower end of the screen on the projection plane, and θs is the angle formed by the center ray of the screen and the normal of the projection plane. Come, it is preferably formed so as to satisfy the following expression.
| L1-L2 | <1.2 * sin θs * Dv
According to the present invention, in the projection display apparatus, the normal line at the center of the display surface of the image display element disposed substantially on the optical axis of the lens group constituting the projection optical unit is defined as the lens group. It is preferable to incline with respect to the optical axis of the optical system.

  Further, in the present invention, in the projection display apparatus, the lens group constituting the projection optical unit includes a front lens group including a plurality of refractive lenses having a positive power having a rotationally symmetric surface shape; And a rear lens group including a plurality of lenses having a shape of a rotationally asymmetric free-form surface, and further, the lens on a path of a screen center ray of the projection optical unit toward the projection plane It is preferable that the optical path length from the last surface of the group to the reflecting surface of the reflecting mirror is five times or more than the focal length of the front lens group of the lens group. Alternatively, the rear lens group further includes a refractive lens having a negative power having a rotationally symmetric surface shape, and the rear lens group moves in the optical axis direction with respect to the front lens group. Preferably it is possible.

  Furthermore, in the present invention, the projection display apparatus preferably further comprises means for moving the rear lens group in the optical axis direction, or the rear lens group moving means is external to the apparatus. It is preferable to be operable. Alternatively, it is preferable that the projection optical unit further includes a plane mirror that reflects the reflected light from the rotationally asymmetric convex reflection mirror. Alternatively, in the projection display apparatus, the projection optical unit further includes: It is preferable that a positioning mechanism for adjusting the traveling angle of the emitted light from the device is provided on the bottom surface of the housing.

  In addition, according to the present invention, in order to achieve the above-described object, a lens group that is disposed adjacent to the image display element and includes a plurality of projection lenses, A projection optical unit that includes a reflection mirror that reflects incident light and projects an image on the projection plane at an angle, and is diagonal to the distance (Lp) from the center of the reflection mirror to the projection plane A projection optical unit is provided wherein the ratio (Lo / Lp) between the dimensions (Lo) is at least 2 or more.

  In the present invention, there is provided a projection-type image display device comprising an image display element and a projection optical unit that enlarges an image displayed on the image display element and projects the image onto a projection plane, as the projection optical unit. A projection display apparatus using the projection optical unit described above is provided.

  According to the present invention described above, a wide angle can be obtained without requiring an additional optical system having a large aperture, and distortion and aberration can be minimized even if the position to the projection surface (screen) is changed. It is possible to suppress this, and it has an excellent effect that it is possible to realize a projection-type image display device that has good performance, is convenient, and is easy to use.

1 is a perspective view showing an overall configuration of a projection display apparatus according to an embodiment of the present invention. It is sectional drawing which shows the basic composition of the projection optical unit of the said projection type video display apparatus. It is a perspective view which shows an example of lens arrangement | positioning of the said optical unit. It is sectional drawing of the perpendicular direction and the horizontal direction for demonstrating the lens surface of the said optical unit. It is a perspective view which shows the whole structure of the projection type video display apparatus concerning other embodiment of this invention. It is a perspective view which shows an example of lens arrangement | positioning of the optical unit in the projection type video display apparatus which becomes said other embodiment. It is sectional drawing of the perpendicular direction for demonstrating the lens surface of the said optical unit. It is YZ sectional drawing which shows the optical path in the projection type video display apparatus of the said invention. It is XZ sectional drawing which shows the optical path in the projection type video display apparatus of the said invention. It is a figure which shows the distortion performance of the optical unit which becomes Example 1 of this invention. It is a figure which shows the spot performance of the optical unit which becomes Example 1 of this invention. It is a figure which shows the distortion performance of the optical unit which becomes Example 2 of this invention. It is a figure which shows the spot performance of the optical unit which becomes Example 2 of this invention. It is a figure which shows the distortion performance of the optical unit which becomes Example 3 of this invention. It is a figure which shows the spot performance of the optical unit which becomes Example 3 of this invention. It is a figure which shows the distortion performance of the optical unit which becomes Example 4 of this invention. It is a figure which shows the spot performance of the optical unit which becomes Example 4 of this invention. It is a figure which shows the state which applied the said projection optical unit to the projection type video display apparatus, and expanded and projected the image on the screen. It is a figure which shows the state at the time of changing projection distance in the projection type video display apparatus to which said projection optical unit is applied. It is a figure which shows the distortion performance and spot performance at the time of changing projection distance in the projection type video display apparatus to which said projection optical unit is applied. It is a figure which shows the distortion performance and spot performance at the time of changing projection distance in the projection type video display apparatus to which said projection optical unit is applied. It is a figure which shows the state which moved the back lens group in said projection optical unit. FIG. 3 is a perspective view including a partial cross section showing an example of a structure for moving a rear lens group in the projection optical unit in the projection display apparatus. It is sectional drawing of the horizontal direction for demonstrating the lens surface in said projection optical unit. It is a figure which shows the distortion performance at the time of moving a back lens group in said projection optical unit. It is a figure which shows the spot performance at the time of moving a back lens group in said projection optical unit. It is a perspective view which shows the whole structure of the projection type video display apparatus concerning further another embodiment of this invention. It is sectional drawing which shows the basic composition of the projection optical unit in the projection type video display apparatus which becomes the said further another embodiment. It is a figure for demonstrating the structure and usage method of the positioning mechanism attached to a part of projection type video display apparatus of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
First, FIG. 1 attached is a perspective view showing an overall configuration of a projection display apparatus according to an embodiment of the present invention. That is, in this figure, inside the substantially box-shaped casing 110 constituting the projection display apparatus 100, for example, an image display element 1 for displaying an image or video input from an external personal computer, And a light source 8 such as a lamp that generates white light having a luminance. The structure of the light source 8 will be described in detail below. The light emitted from the light source 8 and modulated by the image display element 1 is enlarged. A projection optical unit for irradiating is mounted. When the projection display apparatus is used indoors, the light emitted from the projection optical unit faces one direction (longitudinal direction in the figure) of the housing 110 as indicated by an arrow in the figure. It is projected onto a so-called screen 5 such as a wall surface of a room or a sheet-like screen.

  Next, a basic optical configuration of the projection optical unit constituting the projection display apparatus will be described with reference to the attached sectional view of FIG. 2 shows the cross section viewed from the lower right direction of FIG. 1 (see the white arrow in the figure). The XYZ orthogonal coordinate system shown in FIG. This corresponds to the YZ cross section in FIG.

  As shown in FIG. 2, the projection optical unit according to the present invention includes an image display element 1 and a prism 10 that emit light from a light source 8 and emits a desired image, a front lens group 2 and a rear lens group 3. And a reflecting mirror (hereinafter referred to as a free-form surface mirror) having a free-form reflection surface that is not rotationally symmetric (that is, non-rotationally symmetric). 4 and a reflecting optical system.

  Here, as the image display element 1, for example, a transmission type typified by a liquid crystal panel is used. However, the present invention is not limited to this, for example, a self-luminous type such as a CRT. It may be. Further, when a transmissive type such as the above-described liquid crystal panel is employed as the image display element 1, a lamp serving as the light source 8 for irradiating the liquid crystal panel is required. Further, as the liquid crystal panel, a method of combining a plurality of R, G, and B images, such as a so-called three-plate type, may be used, and in that case, a video combining prism or the like is required. However, details of these liquid crystal panels and lamps that serve as the light source 8 for irradiating the liquid crystal panels will be described later, and are not directly related here, and thus illustration thereof is omitted. On the other hand, it is obvious that the light source 8 is not necessary for a self-luminous type such as a CRT.

  In the projection optical unit of the present invention configured as described above, light emitted from the image display element 1 via the prism 10 is first incident on the front lens group 2 constituting the lens optical system. Although the details will be described later, the front lens group 2 includes a plurality of refractive lenses having a rotationally symmetric surface shape and having positive power and negative power. Thereafter, the light emitted from the front lens group 2 is composed of a plurality of lenses including a plurality of (two in this example) lenses having a free-form surface shape in which at least one surface is not rotationally symmetric (rotationally asymmetric). The rear lens group 3 is passed through. The light emitted from the rear lens group 3 is further magnified and reflected by a reflecting optical system including a reflecting mirror (hereinafter referred to as a free-form curved mirror) 4 having a free-form reflecting surface that is not rotationally symmetric. The image is projected onto a predetermined screen 5 (for example, a wall surface of a room or a sheet-like screen).

  In this embodiment, as is clear from FIG. 2, the projection screen (display element) is perpendicular to the optical axis of the projection system as in the prior art (particularly, the above-mentioned Patent Documents 1 and 2). Unlike the optical system in which the additional optical system is arranged at a predetermined angle with respect to the optical axis of the projection system, the image display element 1 has a lens optical system at the center of the display screen. They are disposed so as to be substantially on the optical axis (that is, they form a coaxial optical system). Accordingly, the light beam 11 that exits from the center of the display screen of the image display element 1 and passes through the center of the entrance pupil of the lens optical system toward the center of the screen on the screen 5 is substantially the lens optical system (the front lens group 2 and It proceeds along the optical axis of the rear lens group 3 (including the rear lens group 3) (hereinafter referred to as “screen central ray”). Thereafter, the screen central ray 11 is reflected at a point P2 on the reflection surface 4 having a free curved surface shape of the reflection optical system (including a free curved mirror), and then is reflected at a point P5 at the screen center on the screen 5. It is incident obliquely from below with respect to the normal 7 of the screen. 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 lens optical system is incident on the screen obliquely, so that the optical axis of the lens optical system is substantially inclined with respect to the screen. It means that it is (obliquely incident system).

  As described above, when a light beam is incident obliquely on the screen, the rectangular shape projected from the image display element 1 becomes a trapezoid, including so-called trapezoidal distortion. However, in the present invention, these are corrected by the rear lens group 3 constituting the lens optical system and the reflection surface of the reflection optical system. Is.

  In particular, the light obtained by the lens is obtained by enlarging and reflecting the light projected from the image display element 1 on the reflecting surface of the reflecting mirror 4 constituting the reflecting optical system and entering the screen 5 obliquely. Compared to the amount of decentering (deflection angle), a larger amount of decentering (deflection angle) can be obtained, and since it is difficult for aberrations to occur, it is possible to suppress the enlargement of the apparatus and to widen the angle of view. It becomes possible. That is, the lens optical system including the front lens group 2 and the rear lens group 3 is decentered from the additional optical system (afocal converter) of the above-described prior art (particularly, the above-described Patent Documents 1 and 2) to suppress trapezoidal distortion. Compared to the configuration, it is possible to configure as an optical system having a smaller aperture.

  Further, as described above, since the light incident on the reflecting surface of the reflecting mirror 4 constituting the reflecting optical system is projected to be enlarged to a predetermined size by the lens optical system, it is enlarged only by the conventional reflecting mirror. Even when compared with the structure constituting the projection system (for example, Patent Document 3 described above), its manufacture is facilitated. That is, the lens optical system is manufactured separately from the reflection optical system, and then the position of both of them is fixed and adjusted in the apparatus housing, so that it is particularly suitable for mass production. Further, as described above, according to the configuration in which the rear lens group 3 for correcting trapezoidal distortion or the like is arranged in front of the front lens group 2, the rear lens group 3 is arranged between the rear lens group 3 and the front lens group 2. Since it becomes possible to arrange with a small interval, the apparatus on which the projection optical unit is mounted can be made compact as a whole, and in particular, a favorable effect that the height at the lower part of the screen can be reduced. Is obtained.

  In this way, by combining a transmission lens optical system having a free-form surface shape and a reflection optical system having a free-form surface shape, particularly in the case of being suitable for a front-transmission type image display apparatus, Widening the angle of view, which is strongly demanded in the imaging mode, can be realized reliably and relatively easily as a compact projection-type video display apparatus in which the entire apparatus is reduced.

  Next, FIGS. 3 and 4 attached herewith show details of the optical elements including the lens optical system and the reflective optical system of the projection optical unit constituting the projection display apparatus. 3 is a perspective view of the projection optical unit, and FIG. 4 shows a vertical section (FIG. 4A) and a horizontal section (FIG. 4B), respectively.

  As shown in these figures, in the lens optical system, an image emitted from the image display element 1 through the prism 10 is first incident on the front lens group 2 including a plurality of rotationally symmetric lenses. The As described above, the front lens group 2 includes a rotationally symmetric spherical lens and an aspheric lens. Alternatively, as shown in FIGS. 5 and 6, a folding mirror 35 may be disposed in the middle of the front lens group 2 and the rear lens group 3 to bend the light beam at a right angle.

  The rear lens group 3 is composed of at least two free-form surface lenses. As shown in these figures, the free-form surface lens 31 closest to the reflecting surface S22 of the reflecting mirror 4 has a concave portion in the light emitting direction, and a light ray incident on the lower end of the screen passes therethrough. The curvature of the part is set larger than the curvature of the part through which the light ray incident on the upper end of the screen passes. In other words, a free-form surface lens is curved with its concave portion facing in the direction of light emission, and the curvature of the portion through which light incident on the lower end of the screen passes is the same as that on which the light incident on the upper end of the screen passes. It shall have a shape larger than the curvature of the part to do.

  Moreover, in this embodiment, it is comprised so that the following conditions may be satisfy | filled. That is, in the cross section shown in FIG. 2, a light ray emitted from the lower end of the screen of the image display element 1 and passing through the center of the entrance pupil of the front lens group 2 and incident on the point P6 at the upper end of the screen 5 is a ray. 12 An optical path length from the point P3 where the light ray 12 passes through the free-form surface mirror 4 to a point P6 on the screen is defined as L1. Further, a light ray that is emitted from the upper end of the screen of the image display element 1 and passes through the center of the entrance pupil of the front lens group 2 and enters the point P4 at the lower end of the screen 5 is referred to as a light ray 13. The optical path length from the point P1 where the light ray 13 passes through the free-form surface mirror 4 to the point P4 on the screen is L2. In the above-described projection optical unit, L1 and L2 are configured to satisfy the following expression.

  Here, Dv is the size of the screen on the screen in the cross section of FIG. 2, in other words, the distance from the top point P6 on the screen to the bottom point P4 on the screen. Θs is the oblique incident angle.

  On the other hand, the image display element 1 is arranged so that the center of the display screen is positioned on the optical axis of the lens optical system. Alternatively, as shown in FIG. It would be desirable for the normal to be placed slightly inclined with respect to the optical axis of the lens optical system.

  In FIG. 2, as described above, the optical path length from the point P3 to the point P6 is longer than the optical path length from the point P1 to the point P4. This means that the image point P6 on the screen is farther than the image point P4 when viewed from the lens optical system. Therefore, an object point corresponding to the image point P6 on the screen (a point on the display screen) is closer to the lens optical system, and an object point corresponding to the image point P4 is closer to the lens optical system. For example, the tilt of the image plane can be corrected. For this purpose, as shown in FIG. 7, the normal vector at the center of the display screen of the image display element 1 is placed on the optical axis of the lens optical system in the plane including the normal line of the screen 5 and the screen central ray. It is preferable to make it tilt slightly. The direction of the inclination is preferably opposite to the direction in which the screen 5 is located.

  In order to obtain an image plane tilted with respect to the optical axis, a method of tilting the object plane is known. However, at an angle of view of a practical size, the image plane due to the tilt of the object plane is not relative to the optical axis. As a result, it was difficult to correct with a rotationally symmetric projection lens. In this embodiment, since the rotationally asymmetric free-form surface lens 31 and the free-form surface lens 32 are also used in the rear lens group 3 described above, it is possible to deal with asymmetric image plane deformation. For this reason, by tilting the object plane, that is, tilting the display surface of the video display element, distortion of the lower-order image plane can be greatly reduced, which is effective in assisting correction of aberrations by a free-form surface.

  Next, with regard to the action of each optical element described above, in the lens optical system, the front lens group 2 (lenses 21 to 25) projects a main lens for projecting the display screen of the image display element 1 onto the screen 5. The basic aberration in the rotationally symmetric optical system is corrected. Further, the rear lens group 3 (lenses 31 to 34) of the lens optical system is composed of lenses having a free-form surface shape that is not rotationally symmetric (rotational asymmetric). Furthermore, since the reflection optical system 4 is composed of a reflective surface having a free-form surface that is not rotationally symmetric, it mainly corrects aberrations caused by oblique incidence. In this way, the mirror 4 constituting the reflection optical system mainly corrects trapezoidal distortion, while the rear lens system group 3 of the lens optical system mainly corrects asymmetric aberrations such as image plane distortion. Yes.

  As described above, in the embodiment of the present invention, the reflection optical system is composed of a single reflection surface (mirror) 4 having a free-form surface shape that is not rotationally symmetric, and the rear lens group 3 of the lens optical system has both sides. Both are configured to include two transmissive lenses (lenses 31 and 32 on the reflection mirror 4 side) each having a rotationally asymmetric free-form surface shape. Here, the free-form surface mirror 4 is curved so that the convex portion is directed in the reflection direction. The curvature of the portion of the free-form curved mirror 4 that reflects the light incident on the lower end of the screen is set larger than the curvature of the portion that reflects the light incident on the upper end of the screen. In addition, the portion that reflects light incident on the lower end of the screen has a convex shape in the reflection direction, while the portion that reflects light incident on the upper end of the screen has a concave shape in the reflection direction. May be.

  The distance in the optical axis direction between the coordinate origin on the reflecting surface (mirror) 4 of the reflecting optical system and the lens surface closest to the reflecting surface (mirror) 4 in the front lens group 2 is the focal point of the front lens group 2. It is desirable to set the distance 5 times or more. According to this, the trapezoidal distortion aberration can be more effectively corrected by the reflecting surface having the free-form surface of the reflecting optical system, so that good performance can be obtained.

  Hereinafter, specific numerical examples of the present invention will be described.

  First, the details of the projection optical unit according to the present embodiment described above will be described in detail with reference to FIGS. 8 and 9 and the following Tables 1 to 4, particularly the lens optical system and the reflective optical system. An explanation will be given while showing specific numerical values of the optical element including. These drawings show ray diagrams of the optical system according to the present invention based on the first numerical example. That is, FIG. 8 shows the YZ cross section in the XYZ orthogonal coordinate system of FIG. 2 described above, that is, the optical system expanded in the Z-axis direction. FIG. 9 shows a configuration in the XZ section. In FIG. 9, as shown in FIGS. 5 and 6, the detailed structure is shown, and a bending mirror 35 is installed in the middle of the front lens group 2 and the rear lens group 3 of the lens optical system constituting the lens optical system. Therefore, an example in which the optical path is bent once in the X-axis direction is shown.

  In this example, the light emitted from the image display element 1 displayed on the lower side of FIG. 4 is a front lens composed of only a lens having only a rotationally symmetric surface in a lens optical system including a plurality of lenses. Pass through group 2. Then, the light passes through the rear lens group 3 including a rotationally asymmetric free-form surface lens and is reflected by the reflection surface of the free-form surface mirror 4 which is a reflection optical system. The reflected light then enters the screen 5.

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

  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 the coefficients of the power term of “r”.

  On the other hand, the free-form surface constituting the rear lens group 3 of the lens optical system uses a local orthogonal coordinate system (x, y, z) with the surface vertex of each surface as the origin, and includes X and Y polynomials. It is expressed by the following formula.

  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 apex, and “r” is the plane in the X and Y axes. The distance from the origin, “k” is a conic constant, and “C (m, n)” is a polynomial coefficient.

  Next, Table 1 below 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, the symbol S0 indicates the display surface of the video display element 11, that is, the object surface, and S23 indicates the reflection surface of the free-form surface mirror 5. Reference numeral S24 is not shown in these drawings, but indicates the incident surface, that is, the image plane of the screen 5 in FIG.

  In Table 1, “Rd” is the radius of curvature of each surface. In FIG. 3, the center of curvature is on the left side of the surface, and the negative value is expressed in the opposite case. . In Table 1 above, “TH” is the inter-surface distance, which indicates the distance from the apex of the lens surface to the apex of the next lens surface. When the next lens surface is on the left side in the figure, the inter-surface distance is expressed as a positive value, and when it is on the right side, it is expressed as a negative value.

  Further, in Table 1 above, S5, S6, S17, and S18 are rotationally symmetric aspherical surfaces. In Table 1, “*” is added next to the surface number, and these four surfaces are clearly displayed. Table 2 below shows the coefficients of the aspherical surfaces.

  In Table 1, S19 to S22 are refracting surfaces having a free curved surface shape constituting the rear lens group of the lens optical system, and S23 is a reflecting surface having a free curved surface S23 shape of the reflecting optical system. # Is displayed next to the number. The coefficient values representing the shapes of these five free-form surfaces are shown in Table 3 below.

  In the present invention, as shown in FIG. 7, the object surface which is the display screen of the image display element 1 is inclined by −1.163 degrees with respect to the optical axis of the lens optical system. It should be noted that the direction of the inclination is represented by a positive value in the direction in which the normal of the object surface rotates clockwise in the cross section of FIG. Therefore, in this embodiment, the object surface is inclined 1.163 degrees counterclockwise from the position perpendicular to the optical axis of the lens optical system in the cross section of FIG.

  Further, the free-form surface mirror 4 indicated by reference numeral S23 in FIG. 3 or FIG. 7 described above places the origin of its local coordinates on the optical axis of the lens optical system, and thus the normal at the origin of the local coordinates, that is, Z The axis is inclined by about +29 degrees from a position parallel to the optical axis of the lens optical system. Note that, as in the case of the object surface, the direction of the inclination is positive in the direction rotating counterclockwise in the cross section of FIG. 3 or FIG. 7, 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 1 and traveled substantially along the optical axis of the lens optical system is reflected by S23 and then the optical axis of the lens optical system. Proceed in a direction tilted by 58 degrees, twice the tilt angle (see arrows in the figure).

  Furthermore, the following Table 4 shows the state of inclination or eccentricity of the local coordinate system of each surface in the present 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. 4, and the display rule is shown above. That's right. “YDE” is the magnitude of the eccentricity, and the eccentricity is set in a direction parallel to the cross section of FIG. 4 and perpendicular to the optical axis. In the cross section of FIG. And In the embodiments described below, the inclination and decentration of the optical element are set in the direction in the cross section parallel to the displayed cross section.

  From Table 1 and Table 3, it can be seen that the curvature “c” and the conic coefficient “k” are zero (0) in this embodiment. That is, trapezoidal distortion due to oblique incidence occurs extremely large in the direction of oblique incidence, and the amount of distortion in the direction perpendicular thereto is small. Therefore, a significantly different function is required between the direction of oblique incidence and the direction perpendicular thereto, and by using the curvature “c” and the conic coefficient “k” that function in all directions in a rotationally symmetric manner, This makes it possible to correct excellent aberrations.

  In Table 4, “ADE” on the surface S23 is the same as θm shown in FIG. 2, and “ADE” on the surface of the screen 5 is θs as shown in FIG. From these two values, the above condition is satisfied, and accordingly, the height of the lower part of the screen is made smaller and a compact optical system is realized.

  The value of the optical path length difference | L1-L2 | shown in the above equation 1 is 0.42 times the screen height of the screen, and θs is 30 degrees. Is pleased. The numerical values in Tables 1 to 4 above represent an image in the range (12.16 × 6.84 mm) on the object plane (for example, a liquid crystal panel having a ratio of 16: 9) and an image plane (60 ″ + over-scan: 1452.8). × 817.2 mm) is an example of a case where the image is enlarged and projected, and the figure distortion at that time is shown in the attached Fig. 10. The vertical direction of Fig. 10 is the vertical direction of Fig. 8, and The horizontal direction in Fig. 10 is the direction perpendicular to the Y axis on the screen (vertical direction in Fig. 9), and the center of the rectangle in the figure is the center of the screen. 10 shows the state of figure distortion by displaying the state of bending of each straight line when the vertical direction of the screen is divided into four and the horizontal direction is divided into eight.

  Further, a spot diagram is shown in FIG. In FIG. 11, (8, 4.5), (0, 4.5), (4.8, 2.7) on the display screen of the video display element 5, that is, the values of the X and Y coordinates. Spot diagrams of light beams emitted from eight points (8, 0), (0, 0), (4.8, -2.7), (8, -4.5), (0, -4.5) Are shown in order from the top (in the drawing, in the order of circled (1) to (8)). 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. Both maintain good performance.

  In addition, when the diagonal dimension of the projection image obtained by the above (for example, the screen 5 in FIG. 1) is “Lo” and the distance from the center of the free-form curved mirror 5 to the projection image is “Lp” (above 1), Lo = 1524 mm, Lp = 700 × cos 45 ° ≈495 mm, so the ratio between them is 2 or more (Lo / Lp> 2), and even at a relatively close distance (Lp) It can be seen that the surface can be enlarged and projected on a sufficiently large screen, that is, the projection magnification rate is excellent.

  Next, a second embodiment will be described with reference to FIGS. 12 and 13 and Tables 5 to 8. Here, all the front lens groups 2 of the lens optical system are composed of rotationally symmetric refracting surfaces, and four of these lens refracting surfaces are rotationally symmetric aspherical surfaces, and the others are spherical surfaces. is there. The axisymmetric aspherical surface used here is expressed by the above-described equation [Equation 2] using a local cylindrical coordinate system for each surface.

  Further, the free-form surface of the lens constituting the rear lens group 3 of the lens optical system uses a local orthogonal coordinate system (x, y, z) with the surface vertex of each surface as the origin, and an X, Y polynomial is expressed. Including the above-described formula, [Expression 3].

  Table 5 below shows lens data of this numerical example, and the surface numbers are S0 for the object surface, and S1 to S23 in order. In Table 5, “Rd” is the radius of curvature of each surface, and “TH” is the inter-surface distance, which indicates the distance from the apex of the lens surface to the apex of the next lens surface.

  In Table 5, surfaces S5, S6, S17, and S18 are rotationally symmetric aspherical surfaces. In Table 1, "*" is added next to the surface number for easy understanding, and these four aspherical surfaces are displayed. The coefficients are shown in Table 6 below.

  In Table 5, surfaces S19 to S22 are refracting surfaces having a free curved surface shape constituting the rear group of the lens optical system, and S23 is a reflecting surface having a free curved surface shape of the reflecting optical system, Displayed with “#” next to the face number. The coefficient values representing the shapes of these five free-form surfaces are shown in Table 7 below.

  Further, Table 8 below shows the inclination of each surface and the magnitude of eccentricity in the second embodiment. The rules for displaying the values “ADE” and “YDE” in Table 8 are as described above. Further, the inclination of each surface in the present embodiment is substantially the same as that in the first embodiment.

  In Table 8, from the ADE (= θm) of S23 and the ADE (= θs) of the screen surface 5, a compact optical system that satisfies the above conditions and has a small lower portion of the screen is realized. .

  Also, the value of the optical path length difference | L1-L2 | shown in Expression 1 is 0.43 times the screen height of the screen and θs is 30 degrees. Therefore, the condition of [Expression 1] is satisfied. You can see that you are satisfied.

  On the other hand, in the second embodiment, as shown in Table 8 above, S15 is decentered by -0.193 mm, and the S17 surface is decentered by 0.193 mm. When a certain surface is decentered, the optical axis moves by the amount of decentering on the subsequent surfaces. Accordingly, the decentering of S15 and S17 means that one lens composed of S15 and S16 is decentered by −0.193 mm from the optical axis. Note that the amount of decentration is very small and does not adversely affect the size of the lens. However, this decentration realizes fine adjustment of asymmetric chromatic aberration.

  Also, from the above Tables 5 and 7, it can be seen that in this example, the curvature “c” and the conic coefficient “k” are zero (0). 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. Accordingly, a significantly different function is required between the direction of oblique incidence and the direction perpendicular thereto, and the figure “c” and the conic coefficient “k” that function in all directions with rotational symmetry are not used. It becomes possible to correct distortion well.

  The effective range of the second embodiment based on the numerical values described above is that the range on the object plane (ratio 16: 9) is expanded on the image plane (70 ″ + over-scan: 1694.9 × 953.4 mm). The projected image is shown in Fig. 12. The vertical direction of Fig. 12 is the vertical direction of Fig. 1 and is the direction of the Y axis, and the horizontal direction of Fig. 12 is perpendicular to the Y axis on the screen. The center of the rectangle in the figure is the center of the screen, and the figure shows the state of the graphic distortion by displaying the state of the straight line that is divided into 4 in the vertical direction and 8 in the horizontal direction.

  A spot diagram of the second embodiment is shown in FIG. In FIG. 13, the values of the X and Y coordinates on the display screen of the video display element 61 are (8, 4.5), (0, 4.5), (4.8, 2.7), (8 , 0), (0, 0), (4.8, -2.7), (8, -4.5), (0, -4.5) (In the figure, in the order of circled (1) to (8)). 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. That is, it can be seen that both maintain good performance.

  Also in this example, assuming that the diagonal dimension of the obtained projection image is “Lo” and the distance from the center of the free-form surface mirror 5 to the projection image is “Lp”, Lo = 1524 mm, Lp = 700 × cos 45 ° ≈495 mm Therefore, the ratio between these becomes 2 or more (Lo / Lp> 2), and even at a relatively close distance (Lp), the object surface can be enlarged and projected onto a sufficiently large screen. It can be seen that the projection magnification is excellent.

  Next, a third embodiment according to the present invention will be described with reference to FIGS. 14 and 15 and Tables 9 to 12. FIG. Here, the front lens group 2 of the lens optical system is all composed of rotationally symmetric refracting surfaces, and four of these refracting surfaces are rotationally symmetric aspherical surfaces, and the other is a spherical surface. . The axisymmetric aspherical surface used here is also expressed by the above-described equation [Equation 2] using a local cylindrical coordinate system for each surface.

  The free-form surface constituting the rear lens group 3 of the lens optical system uses a local orthogonal coordinate system (x, y, z) whose origin is the surface vertex of each surface, and includes a polynomial of X, Y, It is represented by [Equation 3] shown.

  Table 9 below shows lens data in the third example, and the surface numbers are S0 for the object surface, and S1 to S23 in order. In Table 9, “Rd” is the radius of curvature of each surface. “TH” indicates a distance between the surfaces, and indicates a distance from the vertex of the lens surface to the vertex of the next lens surface.

  Also in Table 9, the surfaces S5, S6, S17, and S18 are rotationally symmetric aspherical surfaces, which are displayed in an easy-to-understand manner by adding "*" next to the surface number. The spherical coefficients are shown in Table 10 below.

  In Table 9, surfaces S19 to S22 are refracting surfaces having a free-form surface constituting the rear lens group of the lens optical system, and S23 is a reflecting surface having a free-form surface of the reflection optical system. In addition, “#” is added to the side of the surface number. The values of coefficients representing the shapes of these five free-form surfaces are shown in Table 11 below.

  Further, Table 12 below shows the inclination of each surface and the magnitude of eccentricity in the third embodiment. The rules for displaying the values “ADE” and “YDE” in Table 12 are as described above.

  From Table 12, it can be seen that the above-mentioned conditions are not satisfied. However, in the third embodiment, the depth is reduced accordingly, and the depth is prioritized.

  Further, as shown in Table 12 above, as in the second embodiment, one lens composed of the surfaces S15 and S16 is decentered by −0.304 mm from the optical axis. The amount of decentration is very small, and there is no adverse effect of increasing the size of the lens, but this decentration realizes fine adjustment of asymmetric chromatic aberration.

  Furthermore, the value of the optical path length difference | L1−L2 | shown in the above [Equation 1] is 0.62 times the screen height of the screen, and θs is 45 degrees. Therefore, the above condition is satisfied. ing.

  From Tables 9 and 11, it can be seen that the curvature “c” and the conic coefficient “k” are zero (0) in the third 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. Accordingly, a significantly different function is required between the direction of oblique incidence and the direction perpendicular thereto, and the figure “c” and the conic coefficient “k” that function in all directions with rotational symmetry are not used. It is possible to correct distortion well.

  The effective range of the third embodiment is that the range on the object plane (ratio 16: 9) is enlarged and projected on the image plane (50 ″ + over-scan: 1210.7 × 681.0). 14 shows the distortion of the figure in Fig. 14. The vertical direction of Fig. 14 is the vertical direction of Fig. 2, that is, the direction of the Y axis, and the horizontal direction of Fig. 14 is the Y axis on the screen. The vertical center (horizontal direction), the center of the rectangle in the figure is the center of the screen, and Figure 14 shows the distortion of the figure by displaying the state of the straight line that is divided into 4 in the vertical direction and 8 in the horizontal direction. The state of is shown.

  A spot diagram of this numerical example is shown in FIG. In FIG. 15, on the display screen of the video display element 61, 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), (0, -4.5) (In the figure, in the order of circled (1) to (8)). 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. That is, it can be seen that both maintain good performance.

  Also in this example, assuming that the diagonal dimension of the obtained projection image is “Lo” and the distance from the center of the free-form surface mirror 5 to the projection image is “Lp”, Lo = 1524 mm, Lp = 700 × cos 45 ° ≈495 mm Therefore, the ratio between these becomes 2 or more (Lo / Lp> 2), and even at a relatively close distance (Lp), the object surface can be projected on a sufficiently large screen, that is, It can be seen that the projection magnification is excellent.

  A fourth embodiment according to the present invention will be described with reference to FIGS. 16 and 17 and Tables 13 to 16. FIG.

  Here again, the light emitted from the image display element 1 is a lens optical system including a front lens group 2 of a lens optical system including a transmission lens having a rotationally symmetric surface shape and a transmission lens having a free-form surface shape. After passing through the rear lens group 3 of the system in this order, it is reflected by the reflecting surface 4 having a free-form surface shape of the reflecting optical system and enters the screen 5.

  That is, also in this case, the front lens group 2 of the lens optical system is all composed of rotationally refracting refracting surfaces, and four of the refracting surfaces are rotationally symmetric aspherical surfaces, and the others are spherical surfaces. It is. Further, the axisymmetric aspherical surface used here is expressed by the above-described equation [Equation 1] using a local cylindrical coordinate system for each surface.

  The free-form surface constituting the rear lens group 3 of the lens optical system also uses a local orthogonal coordinate system (x, y, z) whose origin is the surface vertex of each surface, and includes a polynomial of X, Y. [Expression 2].

  Table 13 below shows lens data of the fourth example, where the surface number is S0 for the object surface, S1 to S24 in order, and S25 is the image surface. In Table 13, “Rd” is the radius of curvature of each surface. In FIG. 3 or FIG. 7, when the center of curvature is on the left side of the surface, the value is positive. Yes.

  In Table 13, “TH” is a distance between surfaces, and indicates a distance from the vertex of the lens surface to the vertex of the next lens surface. Further, when the next lens surface is on the left side of the lens surface, the inter-surface distance is a positive value, and when it is on the right side, it is expressed as a negative value.

  In Table 13, S5, S6, S17, and S18 are rotationally symmetric aspherical surfaces. In Table 13, "*" is added next to the surface number for easy understanding, and these four aspherical surfaces are displayed. The coefficients are shown in Table 14 below.

  In Table 13, S19 to S22 are refractive surfaces having a free-form surface constituting the rear lens group 3 of the lens optical system, and S23 is a reflection surface having a free-form surface of the reflection optical system. , "#" Is displayed next to the surface number. The values of coefficients representing the shapes of these five free-form surfaces are shown in Table 15 below.

  Further, Table 16 below shows the inclination and eccentricity of each surface in this example. The rules for displaying the values of “ADE” and “YDE” in Table 16 are as described above, and the inclination of each surface in this embodiment is almost the same as that in the first embodiment.

  That is, it can be seen from Table 16 that the above-mentioned conditions are not satisfied. However, the depth is small correspondingly, and this is an embodiment in which depth is prioritized.

  On the other hand, in the fourth embodiment, as shown in Table 16 above, the S15 surface is decentered by -0.23 mm, and the S17 surface is decentered by 0.23 mm. When a certain surface is decentered, the optical axis moves by the amount of decentering on the subsequent surfaces. Accordingly, the decentering of S15 and S17 means that one lens composed of S15 and S16 is decentered by −0.193 mm from the optical axis. The amount of decentration is very small, and there is no adverse effect of increasing the size of the lens, but this decentration realizes fine adjustment of asymmetric chromatic aberration.

  Further, the value of the optical path length difference | L1−L2 | is 0.64 times the height of the screen screen, and θs is 45 degrees, which satisfies the condition of [Expression 1].

  Also, looking at Tables 13 and 15, it can be seen that the curvature “c” and the conic coefficient “k” are zero (0) in the fourth 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. Accordingly, a significantly different function is required between the direction of oblique incidence and the direction perpendicular thereto, and the figure “c” and the conic coefficient “k” that function in all directions with rotational symmetry are not used. Distortion can be corrected satisfactorily.

  The effective range of the present embodiment is projected by enlarging the range on the object plane (ratio: 16: 9) onto the image plane (60 ″ + over-scan: 1452.8 × 817.2 mm), The graphic distortion is shown in Fig. 16. The vertical direction of Fig. 16 is the vertical direction of Fig. 2, that is, the direction of the Y axis, and the horizontal direction of Fig. 14 is the direction perpendicular to the Y axis on the screen. (Horizontal direction), and the center of the rectangle in the figure is the center of the screen, and this figure 14 shows the state of the straight line bending in which the vertical direction of the screen is divided into four and the horizontal direction is divided into eight. This shows the state of figure distortion.

  Further, a spot diagram of the fourth embodiment is shown in FIG. In FIG. 17, the values of the X and Y coordinates on the display screen of the video display element 61 are (8, 4.5), (0, 4.5), (4.8, 2.7), (8 , 0), (0, 0), (4.8, -2.7), (8, -4.5), (0, -4.5) (In the figure, in the order of circled (1) to (8)). 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. That is, both maintain good performance.

  When the diagonal dimension of the projection image obtained as described above is “Lo” and the distance from the center of the free-form curved mirror 5 to the projection image is “Lp” (see FIG. 1 above), Lo = 2032 mm, Since Lp = 996 × cos45 ° ≈704 mm, the ratio between them is 2 or more (Lo / Lp> 2), and the object surface is enlarged and projected onto a sufficiently large screen even at a relatively close distance (Lp). It can be seen that the projection magnification ratio is excellent.

  Next, FIG. 18 attached shows a state in which the projection optical unit described in detail above is applied to a projection display apparatus, and an image is enlarged and projected on, for example, a wall surface of a room or a sheet-like screen. Furthermore, FIG. 19 attached shows a problem when the projection distance from the projection optical unit to the screen is changed. That is, as is clear from FIG. 19, in the method of using a free-form surface and tilting the optical axis with respect to the screen and projecting obliquely, if the projection distance is greatly changed from the designed distance, the figure distortion increases and the spot becomes large. The resolution increases as the size increases.

  For example, as shown in FIG. 19 described above, the position of the screen 5 is changed from the design position 65 (designed screen size, for example, 80 inches) to the position 66 (for example, screen size 60) in the direction of reducing the projection screen. FIG. 20 shows the spot shape and the state of distortion when placed on an inch), and the spot shape and distortion when placed at a position 67 in the direction of enlarging the screen (for example, equivalent to a screen size of 100 inches). The state is shown in FIG. As is apparent from FIGS. 20 and 21, the magnitude of the distortion increases to about 2% or more of the screen vertical width, and the spot shape becomes more than three times as large as the design position, resulting in degraded resolution performance. To do.

  Note that the increase in the spot cannot improve the spot shape on the entire screen even if, for example, the position of the panel is moved back and forth to perform focusing. The reason is that, since the optical system is not rotationally symmetric, when the panel or rotationally symmetric lens is moved, if the focus of a part of the screen is adjusted, the focus of the other part is greatly shifted. Further, the spot shape cannot be corrected by moving only the lenses 31 and 32 of the rear lens group which is a free-form surface lens. This is because the power of the rotationally symmetric lens is required to correct the distortion accompanying the movement of the screen position.

  Therefore, based on the above embodiment, as a result of investigating a lens that is effective in improving spot shape distortion and resolution performance by moving the lens in accordance with the movement of the screen position, in particular, the rear It is effective to move the transmission lenses 31 and 32 having a free curved surface in the optical axis direction together with the lenses 33 and 34 (see FIG. 2 or FIG. 6 described above) having negative power constituting the lens group. I found out. The movement of the mirror 4 having the free curved surface is also effective. However, it is difficult to move the free-form mirror 4 that is inclined and has a relatively large size from the viewpoint of the structure of the apparatus. It is most effective to move 31-34.

  In the attached FIG. 22, the lenses constituting the rear lens group 3, that is, a transmission lens 31 having a free curved surface, a transmission lens 32 having a free curved surface, and two rotationally symmetric lenses having negative power are shown. The transmission lenses 33 and 34) are moved. Note that FIG. 22A shows the projection screen at the design position 65 (screen size) when the projection screen is placed at a position 66 (corresponding to a screen size of 60 inches) in FIG. FIG. 22C shows a case where the projection screen is moved to a position 67 in the direction of enlarging the projection screen. That is, in this embodiment, with respect to the movement of the screen position, a negative lens power constituting the rear lens group 3 and a lens group in which the lens to be rotated in the vicinity are combined, and a free lens group. Two transmissive lenses having a curved surface are used as one lens group, and the lens group is moved in the optical axis direction and adjusted with respect to the screen position. I try to get performance.

  As described above, as a structure for moving the lenses 31 to 34 constituting the rear lens group 3, for example, as shown in the attached FIG. The front lens group 2 (rotationally symmetric lenses 21 to 25) and the rear lens group 3 (lenses 31 to 34) are incorporated in the individual mounting bases 210 and 220, respectively, and one mounting base 210 is mounted on the housing of the apparatus. While being fixed on the bottom part 111 of the body 110, the other mounting base 220 is slidably mounted on a rail, for example. Further, for example, a rod-shaped member 221 extends upward from the other mounting base 220 and protrudes to the outside from a slit portion 112 formed on the upper surface of the housing 110. In addition, grooves 221, 222, and 223 are formed in advance on the other mounting table (for example, mounting table 220), and the mounting table 220 is connected to the mounting table 210 (in this example, in the figure). As indicated by an arrow, the lens unit is installed in the apparatus so as to be movable (in a direction perpendicular to the optical axis direction of the lens group).

  In addition, as shown in FIG. 23B, the lenses 31 to 34 constituting the rear lens group 3 are integrated with the lenses 33 and 34, that is, the lens 31, the lens 32, and The lens is divided into three groups consisting of lenses 33 and 34, and the respective positions thereof are moved corresponding to the screen size (60 inch, 80 inch, 100 inch) obtained by projecting on the screen. That is, the grooves 221, 222, and 223 are formed corresponding to these three groups of lenses, that is, at a desired inclination angle with respect to each lens group. According to such a configuration, the rod member 221 that protrudes from the movable mounting base 220 to the outside of the housing is previously marked on the surface of the housing 110 by “60” inches, “80” inches, “100” inches, or the like. By moving to the position where the mark is attached, the three groups of lenses, that is, the lens 31, the lens 32, and the lenses 33 and 34 are moved along the grooves 221, 222, and 223, respectively. It will be arranged at a desired position. That is, according to such a configuration, the projection screen can be sized in the form of spot distortion and resolution performance by moving the tip of the rod-shaped member 221 in the direction of the arrow in the figure from the outside of the projection display apparatus. It becomes possible to change without deteriorating.

  Alternatively, although not shown, the same function as described above can also be achieved by using a cylinder in which grooves as described above are formed on the outer periphery, although not shown. In this case, in particular, the two transmission lenses 31 and 32 having a free curved surface in the rear lens group 3 do not need to be rotated in spite of the change in the relative position in the optical axis direction. For this reason, for example, it is preferable that the cylindrical member is configured to be rotatable independently of each other, that is, separated from the front end side and the rear end side so that the front end side does not rotate. Furthermore, for example, it may be possible to employ a structure in which the rear lens group 3 (lenses 31 to 34) is moved using drive means including an electric motor or the like. That is, according to this, the effect of improving the distortion of the spot shape and the resolution performance can be obtained in response to the change in the position of the screen on which the image is projected (that is, the distance from the apparatus to the screen).

  Subsequently, the lens data of the above-described embodiment will be shown below with reference to the following Tables 17 to 21 and FIGS.

  Also in this case, the expression of the free-form surface is the same as the above [Equation 1]. The numerical values in Tables 17 to 20 below are obtained when an image in the range on the object plane (ratio 16: 9) is enlarged and projected on the image plane (60 ″ + over-scan: 1841.9 × 1036.1 mm). In addition, the lens surface of the optical element in the projection optical unit in this case is shown in Fig. 24. This embodiment is different from the above embodiment in Fig. 4 above. In FIG. 21, the lens surfaces indicated by S9 and S10 are integrated with each other in FIG.

  First, in Table 17, “Rd” is a radius of curvature of each surface, and is represented by a positive value when the center of curvature is on the left side of the surface in the figure, and a negative value in the opposite case. . In Table 17, “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 positioned on the left side with respect to a certain lens surface, the inter-surface distance is expressed as a positive value, and when positioned next to the right side, it is expressed as a negative value. Further, in Table 17, S5, S6, S16, and S17 (see FIG. 4 above) are rotationally symmetric aspherical surfaces. In Table 17, “*” is added beside the surface number. The coefficients of these four aspheric surfaces are shown in Table 18 below.

  In Table 17, S18 to S21 are the refractive surfaces of the free-form surface lens, and S22 is the reflection surface of the free-form surface mirror, which is indicated by “#” next to the surface number. Table 18 shows coefficient values representing the shapes of these five free-form surfaces.

  Next, in Table 19 below, coefficient names and values are displayed side by side as a set of frames, the right side is the value of the coefficient, the left side is the name and the name is separated by commas in parentheses. Numerical values indicate the values of “m” and “n” shown in Equation 2.

  Furthermore, the following table 20 shows the state of inclination or decentering of the local coordinate system of each surface in this example. In Table 20, “ADE” is the magnitude of the inclination in a plane parallel to the cross section of the figure, and the direction of the inclination is positive in the direction rotating counterclockwise within the cross section of the figure, and the unit is degrees. It is. “YDE” is the magnitude of eccentricity, and the eccentricity is set in the cross section of the figure and in the direction perpendicular to the optical axis. In the cross section of the figure, the downward eccentricity is positive, and the unit is mm.

  In the inclination or eccentricity shown in Table 20, all the subsequent surfaces including the displayed surface number are arranged on the inclined optical axis of the displayed surface. However, the inclination of the S22 plane indicates the inclination of the optical axis of only the 22 plane, and the subsequent 23 planes are arranged on the optical axis inclined twice the inclination amount of the 22 plane.

  Table 21 shows changes in the distance between the surfaces of the lens groups that move in response to the movement of the screen position.

  The values in the columns corresponding to Sc65, Sc67, and Sc66 in Table 9 indicate the lens intervals at the screen positions 65, 67, and 66.

  Also, attached FIG. 25 shows the distortion when the screen is at positions 66, 65, and 67 in FIG. 19, and attached FIG. 26 shows the spot shape in that case. The state of each is shown.

  That is, in FIGS. 25A to 25C, the range on the object plane (ratio 16: 9) is enlarged to an image plane of 60 inches, an image plane of 80 inches, and an image plane of 100 inches, respectively. Indicates the shape distortion when projected. The vertical direction of FIG. 24 is the vertical direction of FIG. 1, that is, the Y-axis direction. The horizontal direction in FIG. 22 is the direction perpendicular to the Y axis on the screen, and the center of the rectangle in the figure is the center of the screen. FIG. 24 shows a state of graphic distortion by displaying a 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.

  On the other hand, FIG. 26 shows a spot diagram obtained when the screens are arranged at respective positions 66, 65, and 67 (see FIG. 19). In this figure, the values of the X and Y coordinates on the display screen of the video display element 1 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). The screen positions are shown in order from the top (in the order of circles (1) to (8) in the figure), and in the horizontal direction, the screen positions (Sc66, Sc65, Sc67). 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. That is, as is clear from these figures, it can be seen that in either case, both maintain good performance.

  When the diagonal dimension of the projection image obtained as described above is “Lo” and the distance from the center of the free-form curved mirror 5 to the projection image is “Lp” (see FIG. 1 above), Lo = 2032 mm, Since Lp = 996 × cos45 ° ≈704 mm, the ratio between them is 2 or more (Lo / Lp> 2), and the object surface is enlarged and projected onto a sufficiently large screen even at a relatively close distance (Lp). It can be seen that the projection magnification ratio is excellent.

  Next, FIG. 27 attached shows a projection display apparatus according to another embodiment of the present invention. That is, as is apparent from the drawing, in the projection display apparatus 100 ′ according to another embodiment, in addition to the configuration of the projection optical unit of the projection display apparatus shown in FIG. 1 or FIG. A projection optical unit is configured by further arranging a flat reflecting mirror 21 in the optical path between the free-form reflecting mirror 4 and the screen 5. In the example of this figure, the flat reflecting mirror 21 also serves as a lid for covering the opening formed on the upper surface of the apparatus housing 110 corresponding to the free-curved reflecting mirror 4, and above it. It can be opened and closed freely.

  In the configuration of the projection optical unit, as shown in FIG. 28 attached, the light emitted from the image display element 1 via the prism 10 is first incident on the front lens group 2 constituting the lens optical system. Thereafter, the light emitted from the front lens group 2 is obtained from a plurality of lenses including a plurality of (two in this example) lenses having at least one surface having a free-form surface that is not rotationally symmetric (rotationally asymmetric). It passes through the rear lens group 3 configured. The light emitted from the rear lens group 3 is magnified and reflected by a reflecting optical system including a reflecting mirror (hereinafter referred to as a free-form curved mirror) 4 having a free-form reflecting surface that is not rotationally symmetric. The light is reflected by the flat reflecting mirror 21 and projected onto a predetermined screen 5 (for example, a wall surface of a room or a sheet-like screen). That is, as is apparent from this figure, the projection is performed in the opposite direction to the above-described embodiment (for example, FIG. 2 or FIG. 4). For this reason as well, in the configuration of the projection optical unit of the projection display apparatus 100 ′ according to the other embodiment, the optical path from the free-form surface mirror 4 to the screen 5 is folded back by the plane reflecting mirror 21, so that the screen 5 It is possible to make the distance up to a smaller distance, which is suitable for widening the angle.

  In the configuration of the projection optical unit, as shown by a broken line in FIG. 28, the planar reflecting mirror 27 is configured so that the inclination angle thereof can be adjusted by a minute angle. That is, according to this, it is possible to change the position of the projected image on the screen 5 up and down by changing the inclination angle of the plane reflecting mirror 27 as indicated by the broken line and the arrow in the figure. In particular, it is possible to provide a suitable function in the projection display apparatus. The flat reflecting mirror 27 can be adjusted by the user in accordance with the use state of the projection display apparatus. Alternatively, although not shown here, for example, a driving mechanism including an electric motor is provided. It is also possible to move from a position covering the opening on the top surface of the casing 110 (rise) and to be inclined at an angle set by the user.

  In the projection display apparatus according to the embodiment of the present invention described above, the image (image) from the image display element 1 is emitted from the projection optical unit and reflected by the free-form surface mirror 4, or Further, the light is reflected by the plane reflecting mirror 27 and projected onto the screen 5. Therefore, it is necessary to accurately position the devices 100 and 100 ′ with respect to the screen 5 that projects the video (image). That is, it is preferable to adjust the arrangement so that the light beam at the center of the screen shown in FIG. 5 is perpendicular to the surface of the screen 5. This is important for obtaining a projected screen.

  Therefore, the projection display apparatus according to the embodiment of the present invention is provided with a part of the positioning mechanism of the apparatus, and a specific example thereof will be described below.

  Attached FIG. 29 shows a projection display apparatus 100 provided with the positioning mechanism. In particular, FIG. 29A is a perspective view from above of the projection display apparatus 100 provided with a positioning mechanism. FIG. 29 (b) is a perspective view from the bottom of the device, and FIG. 29 (c) is an enlarged cross-sectional view taken along the line cc in FIG. 29 (b).

  That is, as shown in FIG. 29 (b), the bottom surface of the housing 110 of the projection display apparatus 100 is adjacent to the edge in the light projection direction (right direction in the figure) and at the center thereof. Is attached with a central stopper 113 formed by forming an elastic body such as rubber in a substantially conical shape, on the other hand, adjacent to the edge on the opposite side to the edge, A pair of moving members 114, 114 made of a rotating ball are provided.

  Each of the pair of moving members 114, 114 holds a ball 116 rotatably in a receiving hole 115 formed on the bottom surface of the housing 110, as shown in FIG. The housing 110 includes a restraining member (or pressing member) 117 that stops the rotation of the ball 116 by the movement in the direction of the arrow. That is, when the user presses the restraining member (or pressing member) 117 shown in the figure in the direction of the arrow (however, FIG. 29C is shown upside down), the ball 116 is moved to the inner wall surface of the receiving hole 115. To stop the rotation.

  An example of how to use the positioning mechanism described above is shown in FIG. First, in a state where the restraining member (or pressing member) 117 is moved upward (that is, the ball 116 can be rotated), the projection display 100 is placed with the bottom surface of the housing 110 facing down, for example, Place them in parallel on a desk. Then, as shown by the arrows in the figure, the apparatus 100 (100 ') is rotated about the stopper 113 by pushing the side surface while projecting an image (image) on the screen 5. When the projection display apparatus 100 is at a desired angular position with respect to the screen 5, the pair of moving members 114 and 114 provided on both side surfaces of the apparatus housing 110 are pushed down. That is, according to the projection display apparatus 100 provided with the above-described positioning mechanism, it is possible to easily and accurately position with respect to the screen 5 by the operation described above. By appropriately setting the moving mechanism of the mirror 21 and the rear lens group 3, it is possible to obtain a good projection screen on the screen 5 with the distortion and aberration being minimized as a whole.

  As described above, according to the present invention, it is not necessary to decenter the lens to be used as in the prior art described above, so that it is possible to widen the angle without requiring an additional optical system having a large aperture. In addition, it is possible to provide a projection display apparatus that can minimize distortion even if the position to the screen is changed and that is relatively easy to manufacture. According to such a projection display apparatus, it is possible to obtain a good projection screen that minimizes distortion and aberration throughout, and to realize an easy-to-use projection display apparatus. It becomes possible.

  DESCRIPTION OF SYMBOLS 1 ... Image generation source, 2 ... Front lens group, 3 ... After back lens, 4 ... Free-form surface mirror, 5 ... Screen, 6 ... Normal of origin coordinate of free-form surface mirror, 7 ... Normal of screen, 100, DESCRIPTION OF SYMBOLS 100 '... Projection type video display apparatus, 110 ... Housing | casing, 27 ... Planar reflecting mirror, 113 ... Stopper, 114 ... Moving member

The present invention relates to a projection-type image display apparatus that enlarges an image of an image display element and projects the image on a projection surface such as a screen to display an image, and in particular, a projection-type image display apparatus suitable for a front projection -type image display apparatus. Furthermore, the present invention relates to a projection optical unit for that purpose.

In a color image display device that projects an image of an image display element on a screen ( projection surface) through a projection optical unit composed of a plurality of lenses, a sufficiently large image is displayed on the screen. It is required to obtain without distortion. In order to realize this, as described in Patent Documents 1 and 2 below, for example, the projection screen is shifted in a direction perpendicular to the optical axis of the projection system, and is also predetermined with respect to the optical axis of the projection system. There is already known a projection apparatus or an optical system that enlarges and projects an image in an oblique direction with respect to a screen using an additional optical system arranged at an angle of. The additional optical system (afocal converter) referred to here is an optical system that has the function of converting the size of the projected image, and corrects and reduces the distortion of the projected image due to projection from an oblique direction with respect to the screen. In order to obtain a rectangular projection image.

Reflective imaging optics that uses a plurality of reflecting mirrors (reflection optical elements) instead of the lens (transmission optical elements) described above, and enlarges and projects an image of the image display element on a screen ( projection surface). The system is already known, for example, from US Pat.

That is, when an image is projected from an oblique direction with respect to the screen, so-called trapezoidal distortion occurs in the projected image. In order to solve this problem, the projection optical unit described in Patent Document 1 has a configuration in which trapezoidal distortion is suppressed by decentering an additional optical system (afocal converter) disposed on the screen side. However, it is difficult to widen the angle of the lenses constituting such a decentered optical system because the magnification is low, and therefore the distance from the projection device to the screen becomes large in order to obtain a projection image with the necessary magnification. In addition, the distance between the projection screen and the projection system also increases, which causes a problem that the entire apparatus becomes large (particularly, the length of the optical unit in the optical axis direction). In addition, an additional optical system having a large aperture is required as the lens constituting the decentration additional optical system described above, but this also causes an increase in the cost of the projection optical unit.

Also in the projection optical unit described in Patent Document 2, as in Patent Document 1, since the magnification is low, it is difficult to widen the angle, and it is necessary to individually decenter the lens to be used. In addition, it is difficult to manufacture, and in addition, an additional optical system having a large aperture is required, which causes an increase in the cost of the projection optical unit.

Thus, a transmission type lens optical system having a free-form surface, according to the combination of reflective optical system having a free-form surface, in particular, if appropriate for a front projection type video display, a front projection Therefore, it is possible to realize a wide angle of view, which is strongly demanded by the present invention, as a compact projection-type image display apparatus that is reliable and relatively easy and that makes the entire apparatus small.

Next, Table 1 below shows numerical data of the optical system according to the present example. In Table 1, S0 to S23 correspond respectively to the code S0 to S23 shown in FIG. 4. Here, the symbol S0 indicates the display surface of the video display element 11, that is, the object surface, and S23 indicates the reflection surface of the free-form surface mirror 5. Reference numeral S24 is not shown in these drawings, but indicates the incident surface, that is, the image plane of the screen 5 in FIG.

Next, FIG. 27 attached shows a projection display apparatus according to another embodiment of the present invention. That is, as is apparent from the drawing, in the projection display apparatus 100 ′ according to another embodiment, in addition to the configuration of the projection optical unit of the projection display apparatus shown in FIG. 1 or FIG. A projection optical unit is configured by further arranging a planar reflecting mirror 27 in the optical path between the free-form curved reflecting mirror 4 and the screen 5. In the example of this figure, the flat reflecting mirror 27 also serves as a lid for covering the opening formed on the upper surface of the apparatus housing 110 corresponding to the free-curved reflecting mirror 4, and above it. It can be opened and closed freely.

In the configuration of the projection optical unit, as shown in FIG. 28 attached, the light emitted from the image display element 1 via the prism 10 is first incident on the front lens group 2 constituting the lens optical system. Thereafter, the light emitted from the front lens group 2 is obtained from a plurality of lenses including a plurality of (two in this example) lenses having at least one surface having a free-form surface that is not rotationally symmetric (rotationally asymmetric). It passes through the rear lens group 3 configured. The light emitted from the rear lens group 3 is magnified and reflected by a reflecting optical system including a reflecting mirror (hereinafter referred to as a free-form curved mirror) 4 having a free-form reflecting surface that is not rotationally symmetric. The light is reflected by the flat reflecting mirror 27 and projected onto a predetermined screen 5 (for example, a wall surface of a room or a sheet-like screen). That is, as is apparent from this figure, the projection is performed in the opposite direction to the above-described embodiment (for example, FIG. 2 or FIG. 4). Also from this, in the configuration of the projection optical unit of the projection display apparatus 100 ′ according to another embodiment, the optical path from the free-form surface mirror 4 to the screen 5 is folded back by the plane reflecting mirror 27 , so that the screen 5 It is possible to make the distance up to a smaller distance, which is suitable for widening the angle.

An example of how to use the positioning mechanism described above is shown in FIG. First, in a state where the restraining member (or pressing member) 117 is moved upward (that is, the ball 116 can be rotated), the projection display 100 is placed with the bottom surface of the housing 110 facing down, for example, Place them in parallel on a desk. Then, as shown by the arrows in the figure, the device 100 (100 ′) is rotated about the stopper 113 by pushing the side surface while projecting an image (image) on the screen 5. When the projection display apparatus 100 is at a desired angular position with respect to the screen 5, the pair of moving members 114 and 114 provided on both side surfaces of the apparatus housing 110 are pushed down. That is, according to the projection display apparatus 100 provided with the above-described positioning mechanism, it is possible to easily and accurately position with respect to the screen 5 by the operation described above. By appropriately setting the moving mechanism of the mirror 27 and the rear lens group 3, it is possible to obtain a good projection screen on the screen 5 with the distortion and aberration being minimized as a whole.

Claims (16)

A projection-type image display apparatus comprising: an image display element; and a projection optical unit that enlarges an image displayed on the image display element and projects the image onto a projection plane, the projection optical unit comprising:
A lens group disposed adjacent to the image display element and including a plurality of projection lenses;
A reflection mirror that reflects the light emitted from the lens group and projects the light on the projection surface at an angle,
The lens group is provided between the image display element and the reflection mirror, and includes a plurality of lenses having a rotationally asymmetric free-form shape, and the reflection that reflects light emitted from the lens group A projection-type image display apparatus, wherein a part of the mirror is a rotationally asymmetric convex reflection mirror having a convex shape in a reflection direction.   2. The projection display apparatus according to claim 1, wherein a part of the plurality of lenses having a rotationally asymmetric free-form surface constituting the rear lens group constituting the projection optical unit is a lower end of the projection plane. A projection-type image display apparatus, wherein a curvature of a portion through which a light ray incident on the portion passes and a curvature of a portion through which a light ray incident on the upper end portion of the projection plane passes are different.   2. The projection display apparatus according to claim 1, wherein the rear lens group constituting the projection optical unit includes at least one rotationally symmetric spherical lens and at least one rotationally symmetric lens in addition to the asymmetric lens. A projection display apparatus comprising an aspheric lens.   2. The projection display apparatus according to claim 1, wherein the convex reflection mirror constituting the projection optical unit has a curvature of a portion that reflects a light beam incident on a lower end portion of the projection surface at an upper end of the screen. A projection-type image display device, wherein the projection-type image display device is formed to be larger than a curvature of a portion that reflects incident light rays.   2. The projection display apparatus according to claim 1, wherein the convex reflecting mirror constituting the projection optical unit has a convex shape with respect to a reflection direction of a portion that reflects light incident on a lower end of the screen. The projection optical unit is characterized in that a portion that reflects light incident on the upper end of the screen has a concave shape in the reflection direction. 2. The projection display apparatus according to claim 1, wherein the projection optical unit includes a reflection mirror having a plane including a screen center ray and a normal of the projection plane at a position where the screen center ray is incident. The distance of the path of the light beam incident from the reflection surface to the upper end of the projection surface is L1, the distance of the path of the light beam incident from the reflection surface of the reflection mirror to the lower end of the projection surface is L2, and the upper edge of the screen on the projection surface Projection-type image display formed so as to satisfy the following expression, where Dv is the distance from the base to the lower end, and θs is the angle formed by the screen center ray and the normal of the projection plane: apparatus.
| L1-L2 | <1.2 * sin θs * Dv   2. The projection display apparatus according to claim 1, wherein a normal line at a center of a display surface of the image display element disposed substantially on an optical axis of the lens group constituting the projection optical unit is defined as an optical value of the lens group. A projection-type image display device characterized by being tilted with respect to the optical axis of the system.   The projection type image display device according to claim 1, wherein the lens group constituting the projection optical unit includes a front lens group including a plurality of refractive lenses having a positive power having a rotationally symmetric surface shape, And a rear lens group including a plurality of lenses having a rotationally asymmetric free-form surface shape.   9. The projection display apparatus according to claim 8, wherein an optical path length from a final surface of the lens group to the reflection surface of the reflection mirror is on a path of a screen center ray of the projection optical unit toward the projection surface. A projection-type image display apparatus, wherein the focal length of the front lens group of the lens group is five times or more.   9. The projection display apparatus according to claim 8, wherein the rear lens group further includes a refractive lens having a negative power having a rotationally symmetric surface shape, and the rear lens group includes A projection display apparatus characterized by being movable in the optical axis direction with respect to the front lens group.   9. The projection display apparatus according to claim 8, further comprising means for moving the rear lens group in the optical axis direction.   12. The projection display apparatus according to claim 11, wherein the rear lens group moving means can be operated from outside the apparatus.   9. The projection image display device according to claim 8, wherein the projection optical unit further includes a plane mirror that reflects the reflected light from the rotationally asymmetric convex reflecting mirror. apparatus.   2. The projection display apparatus according to claim 1, further comprising a positioning mechanism for adjusting a traveling angle of light emitted from the apparatus on a bottom surface of the casing of the apparatus. Type image display device. A lens group that is disposed adjacent to the image display element and includes a plurality of projection lenses, and a reflection mirror that reflects the light emitted from the lens group and projects the light on the projection surface in an inclined manner. A projection optical unit comprising:
A ratio (Lo / Lp) between the distance (Lp) from the center of the reflecting mirror to the projection plane and the diagonal dimension (Lo) of the projection plane is at least 2 or more. unit.   16. A projection display apparatus comprising: an image display element; and a projection optical unit that enlarges an image displayed on the image display element and projects the image onto a projection plane, wherein the projection optical unit is the projection optical unit. A projection-type image display apparatus using the projection optical unit.

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