JP6326717B2 - Projection optical system and image display device - Google Patents

Description

  The present invention relates to a projection optical system applicable to an image display apparatus that projects and displays an enlarged image on a screen.

  An image display device (projector) including a projection optical system that projects an image formed by an image forming unit onto a screen that is a projection surface is widely known. A DMD (Digital Micromirror Device), a liquid crystal panel, or the like is used for the image forming unit of such a projector. In recent years, there has been an increasing demand for front projection projectors having a very short projection distance that enables a large screen display while further shortening the projection distance.

  Since the projector with an ultra-short projection distance has a large projection angle, the size of the image displayed on the screen changes greatly even when the distance between the projector and the screen is slightly changed. Therefore, it is difficult for a projector with an ultra-short projection distance to finely adjust the projection (display) image size by adjusting the installation position. Further, when the projector is mounted on a wall, generally, a fastening member such as a bolt is often used, and some of the fastening members have an installation position adjusting function. However, it is difficult to finely adjust the installation position by the adjustment function of the fastening member.

  Thus, a projector including a projection optical system having a zooming function is known so that fine adjustment of the image size on the screen can be easily performed (see, for example, Patent Document 1). The projection optical system provided in the projector of Patent Document 1 includes, in order from the image forming unit, a lens group having positive refractive power, a lens group including an aperture stop and having positive refractive power, and a lens having negative refractive power. A group and a reflecting mirror. In the projection optical system of Patent Document 1, the lens group arranged on the image forming unit side with respect to the arrangement position of the aperture stop moves during zooming, so that the entrance pupil position changes during zooming. When the entrance pupil position changes, the light use efficiency decreases. However, the projection optical system of Patent Document 1 is premised on a lens system with high telecentricity, so that the light use efficiency decreases due to the change in the entrance pupil position to some extent. Suppressed.

  However, there is a problem with the projection optical system that presupposes a lens system with high telecentricity as in Patent Document 1. That is, a projection optical system that performs projection at a very close distance needs to have a wide angle. However, if the projection optical system with high telecentricity is intended to widen the angle, the entire projection optical system becomes large. Therefore, it is difficult to reduce the size of the projection optical system having high telecentricity as disclosed in Patent Document 1.

  In order to construct a projection optical system that is capable of widening the angle so that it can handle projections at shorter distances, but also capable of responding to miniaturization, the lens must be non-telecentric (non-telecentric lens system). You can do it. However, the lens of the non-telecentric optical system has a great influence on the light utilization efficiency due to the change of the entrance pupil position. That is, as in the projection optical system of Patent Document 1, if the entrance pupil position changes during zooming, the brightness of the image fluctuates during zooming. A projection optical system with a zooming function that can handle short-distance projection and that can be downsized, but does not reduce the light utilization efficiency, cannot be realized with conventional configurations. It was.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a projection optical system that has a very short projection distance, can be zoomed, is small, and suppresses a change due to a change in light utilization efficiency.

The present invention is a projection optical system that projects an image formed on an image forming unit onto a projection surface, and has a positive refractive power, and includes a moving lens that is moved during zooming from the enlargement side to the reduction side. A fixed lens group that has a positive refractive power and has an aperture stop that is fixedly arranged closer to the image forming unit than the moving lens group, and does not move during zooming, and the projection target than the moving lens group disposed in the optical path of the reflecting surface arranged on the side and the movable lens group and said reflecting surface, a third lens group having negative refractive power, Tona is, the moving lens group and the fixed lens group Among the third lens groups, only the moving lens group moves during zooming, the lateral magnification on the enlargement side of the moving lens group is βw, the lateral magnification on the reduction side of the moving lens group is βt, When
βw <-1 <βt
It is characterized by satisfying .

  According to the present invention, the projection distance is very short, zooming is possible, the size is small, and the change due to the scaling of the light utilization efficiency can be suppressed.

1 is an optical layout diagram showing an embodiment of an image display device according to the present invention. 1 is an optical arrangement diagram showing an embodiment of a projection optical system according to the present invention. It is the figure which looked at the image formation part with which the above-mentioned image display device is provided from the optical axis direction. It is a graph which shows the position of the intermediate image of the expansion side and reduction side in the said projection optical system. It is a graph which shows the distance in the optical axis direction of the conjugate point and zooming point in zooming in the said projection optical system. It is an example of the image on the screen at the time of the expansion side short distance projection which concerns on Example 1 of the said projection optical system. FIG. 7 is a diagram illustrating (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image in the image illustrated in FIG. 6. It is an example of the image on the screen at the time of reduction side short distance projection by the projection optical system which concerns on the said Example 1. FIG. FIG. 9 is a diagram illustrating (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image in the image illustrated in FIG. 8. It is an example of the image on the screen at the time of the expansion side reference distance projection by the projection optical system which concerns on the said Example 1. FIG. FIG. 11 is a diagram illustrating (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image in the image illustrated in FIG. 10. It is an example of the image on the screen at the time of reduction side reference distance projection by the projection optical system concerning Example 1 above. In the image illustrated in FIG. 12, (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image. It is an example of the image on the screen at the time of the expansion side long distance projection by the projection optical system which concerns on the said Example 1. FIG. In the image illustrated in FIG. 14, (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image. It is an example of the image on the screen at the time of the reduction side long distance projection by the projection optical system which concerns on the said Example 1. FIG. In the image illustrated in FIG. 16, (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image. It is a spot diagram at the time of the expansion side short distance projection in the projection optical system according to Example 1 described above. It is a spot diagram at the time of reduction side short distance projection in the projection optical system concerning Example 1 above. It is a spot diagram at the time of expansion side reference distance projection in the projection optical system concerning Example 1 above. It is a spot diagram at the time of reduction side reference distance projection in the projection optical system concerning Example 1 above. It is a spot diagram at the time of expansion side long distance projection in the projection optical system concerning Example 1 above. It is a spot diagram at the time of reduction side long distance projection in the projection optical system concerning Example 1 above. It is an optical arrangement | positioning figure which shows another embodiment of the image display apparatus which concerns on this invention. It is an optical arrangement | positioning figure which shows another embodiment of the projection optical system which concerns on this invention. It is a graph which shows the position of the intermediate image of the expansion side and reduction side in the said projection optical system. It is a graph which shows the distance in the optical axis direction of the conjugate point and zooming point in zooming in the said projection optical system. It is an example of the image on the screen at the time of the expansion side short distance projection which concerns on Example 2 of the said projection optical system. In the image illustrated in FIG. 28, (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image. It is an example of the image on the screen at the time of the reduction | restoration side short distance projection by the projection optical system which concerns on the said Example 2. FIG. In the image illustrated in FIG. 30, (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image. It is an example of the image on the screen at the time of the expansion side reference distance projection by the projection optical system which concerns on the said Example 2. FIG. In the image illustrated in FIG. 32, (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image. It is an example of the image on the screen at the time of reduction side reference distance projection by the projection optical system concerning Example 2 above. FIG. 35 is a diagram illustrating (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image in the image illustrated in FIG. 34. It is an example of the image on the screen at the time of the expansion side long distance projection by the projection optical system which concerns on the said Example 2. FIG. FIG. 37 is a diagram illustrating (a) a curve on the upper side of the image, (b) a curve on the left side of the image, and (c) a curve on the lower side of the image in the image illustrated in FIG. 36. It is an example of the image on the screen at the time of reduction side long distance projection by the projection optical system which concerns on the said Example 2. FIG. FIG. 39 is a diagram illustrating (a) bending at the upper side of the image, (b) bending at the left side of the image, and (c) bending at the lower side of the image in the image illustrated in FIG. 38. It is a spot diagram at the time of expansion side short distance projection in the projection optical system concerning Example 2 above. It is a spot diagram at the time of reduction side short distance projection in the projection optical system concerning Example 2 above. It is a spot diagram at the time of expansion side reference distance projection in the projection optical system concerning Example 2 above. It is a spot diagram at the time of reduction side reference distance projection in the projection optical system concerning Example 2 above. It is a spot diagram at the time of expansion side long distance projection in the projection optical system concerning Example 2 above. It is a spot diagram at the time of reduction side long distance projection in the projection optical system concerning Example 2 above. It is a figure which shows the field position corresponding to each view angle of the image formation part which concerns on this invention.

  Hereinafter, embodiments of a projection optical system and an image display apparatus according to the present invention will be described with reference to the drawings. Here, the projection optical system according to the present invention is a projection optical system that projects an image formed on the image forming unit onto a projection surface. An image display device according to the present invention is an image display device including the projection optical system according to the present invention.

Embodiment 1 of image display device and projection optical system
FIG. 1 is an optical arrangement diagram showing an embodiment of an image display device according to the present invention. The projector 1 as an image display device includes an image forming unit 10, a parallel plate 40, a projection optical system 100 according to the present invention, an illumination optical system 20 including a light source of illumination light that illuminates the image forming unit 10, and others. Members necessary for image formation are accommodated in the housing 30.

  The image forming unit 10 is, for example, a DMD, a transmissive liquid crystal panel, a reflective liquid crystal panel, or the like. In the present embodiment, for example, a “part for forming an image to be projected” in the DMD is shown as the image forming unit 10.

  The parallel plate 40 is a cover glass (seal glass) that is disposed in the vicinity of the image forming unit 10 and protects the image forming unit 10.

  The projection optical system 100 includes a lens system 101 and a concave mirror 102 that is a reflection surface. Details of the projection optical system 100 will be described later.

  The illumination optical system 20 efficiently illuminates the image forming unit 10 and includes, for example, a rod integrator and a fly eye integrator in order to uniformly illuminate the image forming unit 10. The illumination optical system 20 uses a white light source such as an ultra-high pressure mercury lamp, a xenon lamp, a halogen lamp, and an LED, and a monochromatic light source such as a monochromatic light emitting LED and a monochromatic light emitting LD. In addition, description of the specific structural example of the illumination optical system 20 is abbreviate | omitted.

  Here, in the following description, the image forming unit 10 is premised on an “image forming unit having no function of emitting light” such as DMD. However, in the projection optical system according to the present invention, the image forming unit is not limited to this, and a “self-emission method having a function of emitting a generated image” can also be used.

  In the DMD, the image forming unit 10 is illuminated with illumination light from the illumination optical system 20, and image information is formed. The image information is a light beam that is two-dimensionally intensity-modulated, and this light beam becomes a projected light beam as object light.

  The projection light beam from the image forming unit 10 passes through the projection optical system 100 and becomes a bundled light beam. As a result, the image formed on the image forming unit 10 is enlarged and projected onto a screen (not shown).

  In FIG. 1, a screen (not shown) is arranged in parallel with the image forming unit 10. That is, the normal line of the image forming surface of the image forming unit 10 and the normal line of the screen that is the projection surface are parallel.

  FIG. 2 is an optical layout diagram of the projection optical system 100 according to the present embodiment. FIG. 2A is an optical layout diagram of the projection optical system 100 on the enlargement side. FIG. 2B is an optical layout diagram of the projection optical system 100 on the reduction side.

  The projection optical system 100 includes a lens system 101 and a concave mirror 102 that is a reflection mirror constituting the mirror system. The lens system 101 includes a first lens group 11, a second lens group 12, a third lens group 13, and a concave mirror 102.

  The first lens group 11 has a positive refractive power, and is a fixed lens group that is fixed to the image forming unit 10 during zooming from the enlargement side to the reduction side.

  The first lens group 11 that is a fixed lens group includes an aperture stop 111. The aperture stop 111 is disposed closest to the concave mirror 102 in the first lens group 11. Therefore, the aperture stop 111 is more fixed to the image forming unit 10 side than the second lens group 12 which is a moving lens group.

  A direction perpendicular to the optical axis LX is defined as a Y direction on a plane including a light ray connecting the center of the aperture stop 111 and the center of the projection image.

  The first lens group 11 includes, in order from the image forming unit 10 side, a negative meniscus lens having a convex surface facing the image forming unit 10 side, a positive meniscus lens having a convex surface facing the concave mirror 102 side, and the image forming unit 10 side. It includes a cemented lens of a positive meniscus lens having a convex surface and a negative meniscus lens having a convex surface facing the image forming unit 10, and an aperture stop 111.

  The second lens group 12 has a positive refractive power and is a moving lens group that moves relative to the image forming unit 10 during zooming from the enlargement side to the reduction side.

  The second lens group 12, which is a moving lens group, includes a negative meniscus lens having a convex surface facing the image forming unit 10, a biconvex lens having a strong convex surface facing the concave mirror 102, and a negative lens having a convex surface facing the concave mirror 102. A cemented lens of a meniscus lens, and a cemented lens of a biconvex lens having a strong convex surface on the image forming unit 10 side and a positive meniscus lens having a convex surface directed to the concave mirror 102 side.

  The third lens group 13 has a negative refractive power and includes at least one aspheric lens. The third lens group 13 includes a 3a lens group 131, a 3b lens group 132, and a 3c lens group 133. , Has.

  The third-a lens group 131 includes a biconcave lens having a strong concave surface facing the image forming unit 10 side, a positive meniscus lens having a convex surface facing the concave mirror 102 side, and a biconcave lens having a strong concave surface facing the image forming unit 10 side. , Has.

  The 3b lens group 132 is a positive meniscus lens having a convex surface facing the concave mirror 102 side.

  The third c lens group 133 includes a double-sided aspheric negative meniscus lens having a convex surface facing the concave mirror 102 and a double-sided aspheric negative meniscus lens having a convex surface facing the image forming unit 10 side.

  The concave mirror 102 is a reflecting surface that is disposed on the most enlarged side of the projection optical system 100 and has an odd-order aspherical shape. In this embodiment, the concave mirror 102 is an aspherical mirror, but it is more preferable to use a free-form curved mirror.

  FIG. 2 shows the movement locus of each lens unit related to the lens system 101 during focusing and zooming. The movement trajectory of each lens group during zooming is indicated by a solid line, and the movement trajectory of each lens group during focussing is indicated by a broken line. The first lens group 11, the aperture stop 111, the second lens group 12, and the third lens group 13 each share the optical axis LX.

  As shown in FIG. 2, in the lens system 101, only the second lens group 12 that is a moving lens group shares light with each optical element of the first lens group 11 during zooming from the enlargement side to the reduction side. It moves in the direction away from the image forming unit 10 along the axis LX. That is, in the lens system 101, the moving lens group moves to the concave mirror 102 side during zooming from the enlargement side to the reduction side.

  That is, the aperture stop 111 does not move relative to the image forming unit 10 during zooming from the enlargement side to the reduction side. Thereby, the entrance pupil position does not change even during zooming, and high light utilization efficiency is maintained. In zooming, if the first lens group 11 is not fixed and moved in two or more parts, the entrance pupil position can be prevented from changing, but in this case, the zooming mechanism becomes complicated. This is not preferable because it causes an increase in cost and a decrease in productivity.

  Further, the lens system 101 has a 3a lens group 131 closest to the image forming unit 10 in the third lens group 13 and a 3b lens that is an adjacent positive lens group during focusing from the short distance side to the long distance side. The group 132 is independently moved to the image forming unit 10 side along the optical axis LX.

  The lens system 101 may move the entire third lens group 13 toward the image forming unit 10 along the optical axis LX during focusing from the short distance side to the long distance side.

  FIG. 3 is a diagram of the image forming unit 10 as viewed from the optical axis LX direction. As shown in FIG. 3, the image forming unit 10 is shifted in the Y direction with respect to the optical axis LX. The intersection point between the optical axis LX and the axis line in the Y direction passing through the image forming center C of the image forming unit 10 is defined as an intersection point B0.

  Returning to FIG. A conjugate point of the intersection point B0 by the lens system 101 is defined as a conjugate point B. The light that has passed through the first lens group 11, the second lens group 12, and the third lens group 13 forms an intermediate image conjugate with the image information formed in the image forming unit 10 on the image forming unit 10 side with respect to the concave mirror 102. At the conjugate point B, a spatial image is formed. The intermediate image does not need to be formed as a planar image, and is formed as a curved surface image in this embodiment as well as in other embodiments described later. When zooming from the enlargement side to the reduction side, the conjugate point B once moves on the optical axis LX to the image forming unit 10 side and then moves to the concave mirror 102.

  That is, the projection optical system 100 has little change in the formation position of the intermediate image during zooming from the enlargement side to the reduction side.

  The intermediate image is enlarged and projected toward the screen by a concave mirror 102 which is an aspherical concave mirror disposed on the most screen side. The intermediate image has field curvature and distortion, but this can be corrected by using an aspherical surface or a free-form surface for the concave mirror 102. Therefore, the burden of aberration correction on the lens system 101 provided in the projection optical system 100 is reduced, the degree of freedom in design is increased, and this is advantageous for downsizing and the like.

  FIG. 4 is a graph showing the position of the intermediate image on the enlargement side and the reduction side in the projection optical system 100. In order to simplify the description, only the position in the Y direction is shown. The image size displayed on the screen is 80 inches. In FIG. 4, the vertical axis represents the distance in the Y direction from the optical axis LX to the intermediate focal point at each angle of view, and the horizontal axis represents the lens center on the most concave mirror 102 side of the third lens group 13 at each angle of view. Represents the distance in the optical axis LX direction from the center to the intermediate image (condensing point).

  As shown in FIG. 4, in the projection optical system 100, since the positions of the intermediate images on the enlargement side and the reduction side are substantially the same position, the positional relationship between the concave mirror 102 and the intermediate image does not change during zooming. For this reason, there are few fluctuations of the light incident angle and incident position on the concave mirror 102, and distortion of the projected image and deterioration of the optical performance can be suppressed.

  FIG. 5 is a graph showing the distance in the optical axis LX direction between the conjugate point B during zooming and the intersection point B0 described above. The image size displayed on the screen is 80 inches. In FIG. 5, the vertical axis represents the distance in the optical axis LX direction from the intersection B 0 to the conjugate point B by the lens system 101, and the horizontal axis represents the focal length of the lens system 101. The lateral magnification of the second lens group 12 on the enlargement side is “−1.02”, and the lateral magnification of the second lens group 12 on the reduction side is “−0.97”.

  As described above, since the projection optical system 100 moves only the second lens group 12 during zooming, the projection optical system 100 includes a point where the lateral magnification becomes “−1” during zooming (equal magnification imaging). Become. Therefore, the conjugate point B moves to the concave mirror 102 side after moving to the image forming unit 10 side on the optical axis LX. That is, a locus such that the conjugate point B is convex toward the image forming unit 10 is drawn during zooming. For this reason, the fluctuation of the intermediate image position due to zooming is small.

  If the point at which the lateral magnification is “−1” is removed, the distance in the optical axis LX direction from the intersection B0 to the conjugate point B increases monotonously, and the amount of change in the intermediate image increases rapidly. Therefore, the image enlarged and projected by the concave mirror 102 is deteriorated.

  Further, the conjugate point B of the plane including the image forming unit 10 can be made constant by moving a plurality of lens groups. However, in that case, the configuration of the projection optical system 100 becomes complicated.

  In FIG. 2, the conjugate point B is described only for the light on the optical axis LX, but each conjugate point B shows a similar locus even for light that is not on the optical axis LX (off-axis light). As a result, the projection optical system 100 can reduce the fluctuation of the intermediate image due to zooming.

  The projection optical system 100 forms an image of the 3a lens group 131 and the 3b lens group 132 during focusing from the short distance side to the long distance side among the plurality of lens groups constituting the negative third lens group 13. Move the unit 10 side independently (floating focus). As a result, field curvature and distortion can be highly controlled.

  In particular, in the first embodiment, by using an aspheric lens for the third c lens group 133, the effect of controlling the above-mentioned field curvature and distortion is enhanced.

Next, specific numerical examples of the projection optical system 100 will be described. Here, the meanings of the symbols used in the following description are as follows.
f: focal length of the entire projection optical system 100 NA: aperture efficiency ω: half angle of view (deg)
R: radius of curvature (for aspheric surfaces, the paraxial radius of curvature)
D: Spacing between surfaces Nd: Refractive index νd: Abbe number K: Aspherical conical constant Ai: i-th order aspherical constant

The aspherical shape uses an inverse number of paraxial curvature radius (paraxial curvature): C, height from optical axis: H, conic constant: K, and aspheric constant Ai of each order. , X is expressed by the following formula 1 with the amount of aspheric surface in the optical axis direction.
(Formula 1)

Table 1 shows layout data showing an arrangement example of optical elements constituting the projection optical system 100 according to the first embodiment.
(Table 1)
Numerical aperture: 0.195

Table 2 shows specific examples of lens intervals in zooming and focusing in the projection optical system 100 according to the present embodiment.
(Table 2)

Table 3 shows specific examples of numerical values of the aspheric coefficients in the projection optical system 100 according to the present embodiment. The aspherical surface is expressed by the above formula 1.
(Table 3)

Table 4 shows specific examples of DMDs used as the image forming unit 10 in the projection optical system 100 according to the present embodiment.
(Table 4)

  Next, suppression of image degradation during zooming in the projection optical system 100 according to the present embodiment will be described with reference to FIGS. 6 to 17 illustrate an example in which an image showing a spot position with a wavelength of 550 nm is displayed on the screen at each zoom position and each projection distance in the projection optical system 100 according to the first embodiment, and the image at each angle of view. It is a figure which illustrates distortion. As shown in FIGS. 6 to 17, it can be seen that the projection optical system 100 can project an image with little distortion even at each zoom and each projection distance.

  FIG. 6 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the projection optical system 100 on the enlargement side at the time of short distance projection. FIG. 7 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG. 6.

  FIG. 8 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the reduction-side projection optical system 100 during short-distance projection. FIG. 9 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG.

  Comparing the enlarged profile at the short distance projection shown in FIG. 7 and the reduced profile at the short distance projection shown in FIG. 9, the bending profiles of the upper side, the lower side, and the left side are similar. That is, according to the projection optical system 100 according to the first embodiment, distortion of the projected image due to zooming is suppressed.

  FIG. 10 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the projection optical system 100 on the enlargement side at the time of projecting the reference distance. FIG. 11 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG.

  FIG. 12 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the reduction-side projection optical system 100 at the time of standard separation projection. FIG. 13 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG.

  Comparing the profile on the enlargement side at the time of projection of the reference distance shown in FIG. 11 and the profile on the reduction side at the time of projection of the reference distance shown in FIG. That is, according to the projection optical system 100 according to the first embodiment, distortion of the projected image due to zooming is suppressed.

  FIG. 14 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the projection optical system 100 on the enlargement side during long distance projection. FIG. 15 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG.

  FIG. 16 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the reduction-side projection optical system 100 during long-distance projection. FIG. 17 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG.

  Comparing the enlarged side profile during long distance projection shown in FIG. 15 and the reduced side profile during long distance projection shown in FIG. 17, the bending profiles of the upper side, the lower side, and the left side are similar. That is, according to the projection optical system 100 according to the first embodiment, distortion of the projected image due to zooming is suppressed.

  As described above, as shown in FIGS. 6 to 17, according to the projection optical system 100 according to the first embodiment, an image with little distortion can be projected at each zoom position and each projection distance. Image degradation can be suppressed.

  Next, it will be described using the spot diagram in the projection optical system 100 according to the present embodiment that an image change is suppressed during zooming at each angle of view. Each spot in the spot diaphragm shown in FIGS. 18 to 23 corresponds to a field position shown in F1 to F13 shown in FIG. In addition, each spot diagram has shown the imaging characteristic (mm) on a screen surface about wavelength 625nm (red), 550nm (green), and 425nm (blue).

  FIG. 18 is a spot diagram on the enlargement side during short distance projection. FIG. 19 is a spot diagram on the reduction side during short distance projection.

  As shown in FIGS. 18 and 19, the spots related to the field positions are the same during focusing during short-distance projection. That is, according to the projection optical system 100 according to the present embodiment, image quality fluctuations due to focusing are suppressed.

  FIG. 20 is a spot diagram on the enlargement side during reference distance projection. FIG. 21 is a spot diagram on the reduction side during reference distance projection.

  As shown in FIGS. 20 and 21, the spots related to the field positions are the same during focusing during the reference distance projection. That is, according to the projection optical system 100 according to the present embodiment, image quality fluctuations due to focusing are suppressed.

  FIG. 22 is a spot diagram on the enlargement side during long distance projection. FIG. 23 is a spot diagram on the reduction side during long distance projection.

  As shown in FIGS. 22 and 23, the spots associated with each field position are the same during focusing during long-distance projection. That is, according to the projection optical system 100 according to the present embodiment, image quality fluctuations due to focusing are suppressed.

  According to the projection optical system 100 described above, it is possible to suppress a decrease in the amount of light and prevent a change in the amount of light in the projected image during zooming. Further, according to the projection optical system 100, since the change in the position of the intermediate image is small during zooming, the change in image quality can be suppressed.

Embodiment 2 of image display device and projection optical system
Next, another embodiment of the image display device and the projection optical system according to the present invention will be described focusing on the differences from the above-described embodiment.

  FIG. 24 is an optical arrangement diagram showing an embodiment of an image display apparatus according to this embodiment. The projector 2 as an image display device includes an image forming unit 10, a parallel plate 40, a projection optical system 200 according to the present invention, an illumination optical system 20 including a light source of illumination light that illuminates the image forming unit 10, and others. Members necessary for image formation are accommodated in the housing 30.

  Since the image forming unit 10, the illumination optical system 20, the housing 30, and the parallel plate 40 are the same as those in the first embodiment, detailed description thereof is omitted.

  FIG. 25 is an optical layout diagram showing the projection optical system 200. FIG. 25A is an optical layout diagram of the projection optical system 200 on the enlargement side. FIG. 25B is an optical layout diagram of the projection optical system 200 on the reduction side.

  The projection optical system 200 includes a lens system 201 and a concave mirror 202 that is a reflection mirror constituting the mirror system. The lens system 201 includes a first lens group 21, a second lens group 22, a third lens group 23, a fourth lens group 24, and a concave mirror 202.

  The first lens group 21 has a positive refractive power, and is a fixed lens group that is fixed to the image forming unit 10 during zooming from the enlargement side to the reduction side.

  The first lens group 21 which is a fixed lens group includes an aperture stop 211. Therefore, the aperture stop 211 is fixed to the image forming unit 10 side with respect to the second lens group 22 which is a moving lens group.

  A direction perpendicular to the optical axis LX is defined as a Y direction on a plane including a light beam connecting the center of the aperture stop 211 and the center of the projection image.

  The first lens group 21 includes, in order from the image forming unit 10 side, a negative meniscus lens having a convex surface facing the image forming unit 10 side, a positive meniscus lens having a convex surface facing the concave mirror 202 side, and the image forming unit 10 side. A cemented lens of a biconvex lens having a strong convex surface and a positive meniscus lens having a convex surface facing the concave mirror 202, an aperture stop 211, and a negative meniscus lens having a convex surface facing the image forming unit 10; Become.

  The second lens group 22 has a positive refractive power and is a moving lens group that moves relative to the image forming unit 10 during zooming from the enlargement side to the reduction side.

  The second lens group 22, which is a moving lens group, has a negative meniscus lens having a convex surface facing the image forming unit 10, a biconvex lens having a strong convex surface facing the image forming unit 10, and a convex surface facing the concave mirror 202. And a cemented lens with a negative meniscus lens.

  The third lens group 23 has a positive refractive power, and is a moving lens group that moves relative to the image forming unit 10 during zooming from the enlargement side to the reduction side.

  The third lens group 23 which is a moving lens group includes a positive meniscus lens having a convex surface facing the image forming unit 10 and a positive meniscus lens having a convex surface facing the concave mirror 202 side.

  The fourth lens group 24 has a negative refractive power and includes at least one aspheric lens, and is the negative lens group closest to the image forming unit 10 in the fourth lens group 24. 4a lens group 241, 4b lens group 242, and 4c lens group 243 are provided.

  The 4a lens group 241 includes a negative meniscus lens having a concave surface facing the concave mirror 202, a biconcave lens having a strong concave surface facing the image forming unit 10, and a negative meniscus lens having a convex surface facing the concave mirror 202. It has.

  The fourth lens group 242 is a positive meniscus lens having a convex surface facing the concave mirror 202 side.

  The fourth c lens group 243 includes a double-sided aspheric negative meniscus lens having a convex surface facing the concave mirror 202 and a double-sided aspheric negative meniscus lens having a convex surface facing the image forming unit 10 side.

  The concave mirror 202 is a reflecting surface that is disposed on the most enlarged side of the projection optical system and has an odd-order aspheric shape. In this embodiment, the concave mirror 202 is an aspherical mirror, but it is more preferable to use a free-form curved mirror.

  FIG. 25 shows the movement trajectory of each lens unit related to the lens system 201 during focusing and zooming. The movement trajectory of each lens group during zooming is indicated by a solid line, and the movement trajectory of each lens group during focussing is indicated by a broken line.

  As shown in FIG. 25, the first lens group 21, the aperture stop 211, the second lens group 22, the third lens group 23, and the fourth lens group 24 share an optical axis LX. .

  When zooming from the enlargement side to the reduction side, the lens system 201 has an optical axis LX shared by the second lens group 22 and the third lens group 23, which are moving lens groups, with each optical element of the first lens group 21. It moves in the direction away from the image forming unit 10 along the axis. That is, in the lens system 201, the moving lens group moves to the concave mirror 202 side during zooming from the enlargement side to the reduction side.

  That is, during zooming from the enlargement side to the reduction side, the aperture stop 211 does not move with respect to the image forming unit 10, so that the entrance pupil position does not change during zooming, and high light utilization efficiency is maintained. In zooming, if the first lens group 21 is not fixed and moved in two or more parts, the entrance pupil position can be prevented from changing, but in this case, the zooming mechanism becomes complicated. This is not preferable because it causes an increase in cost and a decrease in productivity.

  Further, when focusing from the short distance side to the long distance side, the lens system 201 includes a fourth lens group 241 that is a negative lens and a fourth lens group 242 that is an adjacent positive lens group independently of the optical axis LX. To the image forming unit 10 side.

  The lens system 201 may move the entire fourth lens group 24 toward the image forming unit 10 along the optical axis LX during focusing from the short distance side to the long distance side.

  Similar to the first exemplary embodiment, the image forming unit 10 is shifted in the Y direction with respect to the optical axis LX. An intersection point between the optical axis LX and the axis line in the Y direction passing through the center of the image forming unit 10 is defined as an intersection point B0.

  Also, as shown in FIG. 25, a conjugate point of the intersection point B0 by the lens system 201 is defined as a conjugate point B. The light that has passed through the first lens group 21, the second lens group 22, the third lens group 23, and the fourth lens group 24 forms an intermediate image conjugate with the image information formed in the image forming unit 10 from the concave mirror 202. Is also formed as an aerial image at the conjugate point B on the image forming unit 10 side. The intermediate image does not need to be formed as a planar image, and is formed as a curved surface image in this embodiment as well as in other embodiments. When zooming from the enlargement side to the reduction side, the conjugate point B temporarily moves on the optical axis LX to the image forming unit 10 side and then moves to the concave mirror 202.

  That is, the projection optical system 200 has little change in the formation position of the intermediate image during zooming from the enlargement side to the reduction side.

  The intermediate image is enlarged and projected toward the screen by a concave mirror 202 which is an aspherical concave mirror disposed on the most screen side. The intermediate image has field curvature and distortion, but this can be corrected by using an aspherical surface or a free-form surface for the concave mirror 202. Therefore, the burden of aberration correction on the lens system 201 included in the projection optical system 200 is reduced, the degree of freedom in design is increased, which is advantageous for downsizing and the like.

  FIG. 26 is a graph showing the position of the intermediate image on the enlargement side and the reduction side in the projection optical system 200. In order to simplify the description, only the position in the Y direction is shown. The image size displayed on the screen is 80 inches. In FIG. 26, the vertical axis represents the distance in the Y direction from the optical axis LX to the intermediate focal point at each angle of view, and the horizontal axis represents the lens center on the most concave mirror 202 side of the third lens group 23 at each angle of view. Represents the distance in the optical axis LX direction from the center to the intermediate image (condensing point).

  As shown in FIG. 26, in the projection optical system 200, the positions of the intermediate images on the enlargement side and the reduction side are substantially the same, but the positional relationship between the concave mirror 202 and the intermediate image does not change during zooming. For this reason, there are few fluctuations of the light incident angle and incident position on the concave mirror 202, and distortion of the projected image and deterioration of the optical performance can be suppressed.

  FIG. 27 is a graph showing the distance in the optical axis LX direction between the conjugate point B during zooming and the intersection point B0 described above. The image size displayed on the screen is 80 inches. In FIG. 27, the vertical axis represents the distance in the optical axis LX direction from the intersection B0 to the conjugate point B by the lens system 201, and the horizontal axis represents the focal length of the lens system 201.

  As already described, the projection optical system 200 moves the second lens group 22 and the third lens group 23 during zooming. As in the first embodiment, during zooming, the conjugate point B moves on the optical axis LX to the image forming unit 10 side, and then moves to the concave mirror 202 side. That is, a locus such that the conjugate point B is convex toward the image forming unit 10 is drawn during zooming. For this reason, the fluctuation of the intermediate image position due to zooming is small.

  Assuming that the locus of the conjugate point B does not include a convex portion, the distance in the optical axis LX direction from the intersection B0 to the conjugate point B includes many monotonous increases and monotonous decreases. The amount of image movement increases. Therefore, when the trajectory of the conjugate point B is a trajectory that does not include a convex portion, the fluctuation amount of the intermediate image increases rapidly, and the image enlarged and projected by the concave mirror 202 is deteriorated.

  In FIG. 25, the conjugate point B is described only for the light on the optical axis LX, but each conjugate point B shows a similar locus even for light that is not on the optical axis LX (off-axis light). As a result, the projection optical system 200 can reduce the fluctuation of the intermediate image due to zooming.

  Further, among the plurality of lens groups constituting the negative fourth lens group 24, when focusing from the short distance side to the long distance side, the 4a lens group 241 and the 4b lens group 242 are floated to the image forming unit 10 side. do. As a result, field curvature and distortion can be highly controlled.

  In particular, in the second embodiment, by using an aspheric lens for the fourth c lens group 243, the effect of controlling the above-described field curvature and distortion is enhanced.

Next, specific numerical examples of the projection optical system 200 will be described. Here, the meanings of the symbols used in the following description are as follows.
f: Focal length of the entire projection optical system 200 NA: Aperture efficiency ω: Half angle of view (deg)
R: radius of curvature (for aspheric surfaces, the paraxial radius of curvature)
D: Spacing between surfaces Nd: Refractive index νd: Abbe number K: Aspherical conical constant Ai: i-th order aspherical constant

  The aspherical shape uses an inverse number of paraxial curvature radius (paraxial curvature): C, height from optical axis: H, conic constant: K, and aspheric constant Ai of each order. , X is expressed by Equation 1 shown in Example 1 where aspherical amounts in the optical axis direction are used.

Table 5 is layout data showing an arrangement example of optical elements constituting the projection optical system 200 according to the second embodiment.
(Table 5)
Numerical aperture: 0.195

Table 6 shows specific examples of lens intervals in zooming and focusing in the projection optical system 200 according to the present embodiment.
(Table 6)

Table 7 shows specific examples of numerical values of the aspheric coefficients in the projection optical system 200 according to the present embodiment.
(Table 7)

Table 8 shows specific examples of DMDs used as the image forming unit 10 in the projection optical system 200 according to the present embodiment.
(Table 8)

  Next, suppression of image deterioration during zooming in the projection optical system 200 according to the present embodiment will be described with reference to FIGS. 28 to 39 show an example in which an image showing a spot position with a wavelength of 550 nm is displayed on the screen at each zoom position and each projection distance in the projection optical system 200 according to Example 2, and the image at each angle of view. It is a figure which illustrates distortion. As shown in FIGS. 28 to 39, it can be seen that the projection optical system 200 can project a projection image with little distortion at each zoom and each projection distance.

  FIG. 28 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the projection optical system 200 on the enlargement side at the time of short distance projection. FIG. 29 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG.

  FIG. 30 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the projection optical system 200 on the reduction side during short distance projection. FIG. 31 is a diagram illustrating (a) bending at the upper side of the image, (b) bending at the left side of the image, and (c) bending at the lower side of the image in the image illustrated in FIG. 30.

  Comparing the enlargement-side profile during short-distance projection shown in FIG. 29 and the reduction-side profile during short-distance projection shown in FIG. 31, the bending profiles of the upper side, lower side, and left side are similar. That is, according to the projection optical system 200 according to the second embodiment, distortion of the projection image due to zooming is suppressed.

  FIG. 32 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the projection optical system 200 on the enlargement side at the time of projecting the reference distance. FIG. 33 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG. 32.

  FIG. 34 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the reduction-side projection optical system 200 at the time of projecting the reference distance. FIG. 35 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG.

  When the profile on the enlargement side at the time of projection of the reference distance shown in FIG. 33 is compared with the profile on the reduction side at the time of projection of the reference distance shown in FIG. 35, the profiles of the bends on the upper side, the lower side and the left side are similar. That is, according to the projection optical system 200 according to the second embodiment, distortion of the projection image due to zooming is suppressed.

  FIG. 36 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the projection optical system 200 on the enlargement side during long distance projection. FIG. 37 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG.

  FIG. 38 is an example of an image showing a spot position with a wavelength of 550 nm displayed on the screen in the projection optical system 200 on the reduction side during long distance projection. FIG. 39 is a diagram illustrating (a) bending on the upper side of the image, (b) bending on the left side of the image, and (c) bending on the lower side of the image in the image illustrated in FIG. 38.

  Comparing the profile on the enlarged side at the time of long distance projection shown in FIG. 37 and the profile on the reduction side at the time of long distance projection shown in FIG. 39, the bending profiles of the upper side, the lower side and the left side are similar. That is, according to the projection optical system 200 according to the second embodiment, distortion of the projection image due to zooming is suppressed.

  As described above, as shown in FIG. 28 to FIG. 39, the projection optical system 200 according to the second embodiment can project an image with little distortion even at each zoom and each projection distance. Deterioration can be suppressed.

  Next, it will be described using the spot diagram in the projection optical system 200 that an image change is suppressed during zooming at each angle of view. Each spot in the spot diaphragm shown in FIGS. 40 to 45 corresponds to the field positions shown in F1 to F13 shown in FIG. In addition, each spot diagram has shown the imaging characteristic (mm) on a screen surface about wavelength 625nm (red), 550nm (green), and 425nm (blue).

  FIG. 40 is a spot diagram on the enlargement side during short distance projection. FIG. 41 is a spot diagram on the reduction side during short distance projection.

  As shown in FIGS. 40 and 41, the spots related to the field positions are the same during focusing during short-distance projection. That is, according to the projection optical system 200 according to the present embodiment, image quality fluctuations due to focusing are suppressed.

  FIG. 42 is a spot diagram on the enlargement side during reference distance projection. FIG. 43 is a spot diagram on the reduction side at the time of projecting the reference distance.

  As shown in FIG. 42 and FIG. 43, the spots related to the field positions are the same during focusing during the reference distance projection. That is, according to the projection optical system 200 according to the present embodiment, image quality fluctuations due to focusing are suppressed.

  FIG. 44 is a spot diagram on the enlargement side during long distance projection. FIG. 45 is a spot diagram on the reduction side during long distance projection.

  As shown in FIGS. 44 and 45, the spots related to the field positions are the same during focusing during long-distance projection. That is, according to the projection optical system 200 according to the present embodiment, image quality fluctuations due to focusing are suppressed.

  According to the projection optical system 200 described above, it is possible to suppress a decrease in the amount of light and prevent a change in the amount of light in the projected image during zooming. Further, according to the projection optical system 200, the fluctuation of the position of the intermediate image is small during zooming, so that the fluctuation of the image quality can be suppressed.

Next, the entrance pupil position in the projection optical system 100 according to the first embodiment and the projection optical system 200 according to the second embodiment will be described. Table 9 shows the entrance pupil position at each zoom position in each example.
(Table 9)

  As shown in Table 9, it can be seen that in either embodiment, the entrance pupil position does not change during zooming.

  According to the projection optical system 100 and the projection optical system 200 described above, the aperture stop 111 (211) is fixedly disposed on the image forming unit 10 side of the moving second lens group 12 (22) during zooming. . With this configuration, the projection optical system 100 and the projection optical system 200 can maintain high light utilization efficiency without changing the entrance pupil position even when zooming is performed.

  Furthermore, according to the projection optical system 100 and the projection optical system 200, since the intermediate image position does not change, a high-quality projection image can be obtained.

  In addition, in the form of each Example mentioned above, although the suitable Example of this invention was shown, this invention is not limited to the content. In particular, the specific shapes and numerical values of the respective parts exemplified in Example 1 and Example 2 are merely examples of implementations in carrying out the present invention, and the technical scope of the present invention is limitedly interpreted by these. Never happen.

  That is, the projection optical system according to the present invention is not limited to the contents described in the present embodiment, and can be appropriately changed without departing from the gist thereof.

  Here, the main features of the projection optical system and the image display apparatus according to the present invention described so far are described below.

● Feature 1
The projection optical system according to the present invention includes a moving lens group that moves during zooming from the enlargement side to the reduction side, an aperture stop that is fixedly disposed closer to the image forming unit than the moving lens group, and a projection target that is more than the moving lens group. And a reflecting surface arranged on the surface side.

  Here, the projection optical system can be mounted on a project or the like that is an image display device, and projects image light formed by the image forming unit toward a screen that is a projection surface.

  According to this feature, the fluctuation of the light utilization efficiency can be suppressed without moving the entrance pupil position during zooming.

  In zooming, at least the moving lens group is moved in the optical axis direction shared by the other optical elements included in the projection optical system, thereby reducing the change in the position of the intermediate image on the reduction side and the enlargement side. be able to. Therefore, the positional relationship between the reflecting surface and the intermediate image can be maintained, and the distortion of the projected image and the deterioration of the optical performance (mainly the curvature of field) due to zooming can be suppressed.

● Feature 2
The projection optical system according to the present invention is characterized in that the lens provided in the projection optical system is a non-telecentric optical system.

  According to this feature, it is possible to achieve a wide angle and a small size in a projection optical system that enables ultra-short distance projection.

● Feature 3
The projection optical system according to the present invention includes, in the above-described projection optical system, a fixed lens group including an aperture stop, and a third lens group disposed in an optical path between the moving lens group and the reflecting surface. The fixed lens group is a lens group having a positive refractive power, the moving lens group is a lens group having a positive refractive power, and the third lens group is a lens group having a negative refractive power. It is characterized by.

  According to this feature, the aperture stop does not move with respect to the image forming unit during zooming because the first lens group is fixed. That is, the position of the entrance pupil does not change even when the moving lens group moves. As a result, fluctuations in light utilization efficiency can be suppressed during zooming.

● Feature 4
The projection optical system according to the present invention is characterized in that, in the above-described projection optical system, the reflecting surface is fixed during zooming.

  If the reflecting surface is moved during zooming or focusing, the degree of freedom in design increases and the performance of the design value is improved. However, the distortion of the projected image due to the positional accuracy of the reflecting surface and the deterioration of the optical performance are large, leading to a decrease in productivity and a complicated configuration. Therefore, according to the above feature, the configuration can be simplified by fixing the reflecting surface.

  As a result, the positional relationship between the reflecting surface and the intermediate image does not change, so that distortion of the projected image and deterioration of the optical performance can be suppressed during zooming.

● Feature 5
In the projection optical system according to the present invention, in the above projection optical system, the reflecting surface is a concave mirror, and an intermediate image enlarged and projected by the concave mirror is formed between the third lens group and the reflecting surface. It is characterized by that.

  According to this feature, the projection distance can be very short.

● Feature 6
The projection optical system according to the present invention is the intersection of the plane including the image forming surface of the image forming unit and the optical axis shared by the fixed lens group, the moving lens group, and the third lens group in the above-described projection optical system. On the other hand, the conjugate point of the fixed lens group, the moving lens group, and the third lens group moves to the projection surface side after moving to the image forming unit side on the optical axis during zooming.

  According to this feature, the amount of movement of the conjugate point can be reduced during zooming. That is, during zooming, fluctuations in the position of the intermediate image can be suppressed, so that deterioration of the projected image due to zooming can be suppressed.

● Feature 7
In the projection optical system according to the present invention, in the projection optical system described above, among the fixed lens group, the moving lens group, and the third lens group, only the moving lens group moves during zooming. Here, when the lateral magnification on the enlargement side of the moving lens group is βw and the lateral magnification on the reduction side of the moving lens group is βt, the conditional expression βw <−1 <βt is satisfied.

  The conditional expression indicates that the lateral magnification of the moving lens group (second lens group having a positive refractive power) becomes “−1” during zooming in the projection optical system according to the present embodiment (same magnification imaging). Is included. According to the above feature, the position variation of the intermediate image is small during zooming from the enlargement side to the reduction side. Thereby, it is possible to suppress changes in the field curvature and distortion of the intermediate image, and to minimize deterioration of the projected image.

  Further, when zooming, the moving lens group is moved to one, so that the configuration becomes simple and the productivity is improved.

  The number of zoom groups is not limited to one. For example, another lens group is arranged between the moving lens group which is the second lens group and the third lens group, and the other lens group is moved. It may be a lens group. Also in this case, it is desirable to move each zoom group so that the movement of the intermediate image is minimized.

  Here, if the conditional expression is not satisfied, the paraxial image position monotonously increases, so that the fluctuation of the intermediate image position becomes large.

● Feature 8
The projection optical system according to the present invention is characterized in that the image forming unit is not located on the optical axis.

  According to this feature, it is possible to highly control the field curvature and distortion of the intermediate image by the aspheric lens and the aspheric mirror.

● Feature 9
The projection optical system according to the present invention is characterized in that focusing is performed by moving some or all of the plurality of lenses constituting the third lens group.

  According to this feature, it is possible to highly control field curvature and distortion that may occur due to focusing.

● Feature 10
The projection optical system according to the present invention is characterized in that the normal of the image forming surface of the image forming unit and the normal of the projected surface are parallel.

  In a projection optical system in which the screen normal line and the image forming unit normal line are parallel, the difference in the light beam incident angle to the screen at the lower end of the screen and the upper end of the screen is large, so that the variation in field curvature increases due to focusing according to the projection distance. However, according to the above feature, since it is a floating focus, it is possible to correct fluctuations in the curvature of field due to fluctuations in projection distance.

● Feature 11
The projection optical system according to the present invention is characterized in that the plurality of lenses constituting the third lens group includes an aspherical lens.

  Light rays from each angle of view of the image forming unit are sufficiently separated on the most reflective surface side. For this reason, according to the above feature, by including an aspheric lens in the lens group (third lens group) arranged closest to the reflecting surface, the effect of correction by the aspheric surface is enhanced, and field curvature and distortion are increased. More advanced control can be performed.

● Feature 12
The projection optical system according to the present invention is characterized in that the reflecting surface is a free-form surface or an aspherical surface.

  According to this feature, curvature of field, distortion, and the like that occur in the intermediate image can be corrected, and the burden on the refractive optical system is reduced, leading to downsizing and improved productivity.

  As described above, according to the projection optical system described above, during zooming, a change in the brightness of the projection image is suppressed, and a distortion of the projection image and a deterioration in optical performance (mainly curvature of field) due to a magnification change are suppressed. be able to.

● Feature 13
An image display device according to the present invention includes an illumination optical system that irradiates light from a light source to an image forming unit, and a projection optical system that projects an image formed on the image forming unit on a projection surface in an enlarged manner, The projection optical system is a projection optical system according to the present invention.

  According to this feature, the projection distance is very short, the size can be reduced, and during zooming, the change in the brightness of the projected image is suppressed, and the distortion and optical performance of the projected image due to zooming (mainly the image) Deterioration of surface curvature can be suppressed.

DESCRIPTION OF SYMBOLS 11 1st lens group 12 2nd lens group 13 3rd lens group 100 Projection optical system 111 Aperture stop 101 Lens system 102 Concave mirror

JP 2010-122574 A

Claims (11)

A projection optical system that projects an image formed on an image forming unit onto a projection surface,
A moving lens group having a positive refractive power, and a lens that moves during zooming from the enlargement side to the reduction side;
A fixed lens group that has a positive refractive power and includes an aperture stop that is fixedly arranged closer to the image forming unit than the moving lens group, and does not move during zooming;
A third lens group having a negative refractive power, disposed in the optical path of the reflecting surface arranged on the projection surface side with respect to the moving lens group, the moving lens group, and the reflecting surface;
Tona is,
Among the fixed lens group, the moving lens group, and the third lens group, the zooming is performed.
And only the moving lens group moves,
The lateral magnification on the magnification side of the moving lens group is βw,
The lateral magnification on the reduction side of the moving lens group is βt,
When
βw <-1 <βt
Meet,
A projection optical system characterized by that. The lens system provided in the projection optical system is a non-telecentric optical system,
The projection optical system according to claim 1. The reflective surface is fixed during zooming.
The projection optical system according to claim 1 or 2. The reflective surface is a concave mirror,
An intermediate image enlarged and projected by the concave mirror is formed between the third lens group and the reflecting surface.
The projection optical system according to claim 1. The fixed lens group and the moving lens group with respect to an intersection of a plane including an image forming surface of the image forming unit and an optical axis shared by the fixed lens group, the moving lens group, and the third lens group. The conjugate point by the third lens group moves to the projection surface side after moving to the image forming unit side on the optical axis during the zooming.
The projection optical system according to claim 1. The image forming unit is shared by the fixed lens group, the moving lens group, and the third lens group.
Not located on the optical axis,
The projection optical system according to claim 1. Focusing is achieved by moving some or all of the plurality of lenses constituting the third lens group.
Sing,
The projection optical system according to claim 1. The normal line of the image forming surface of the image forming unit and the normal line of the projection surface are parallel.
The projection optical system according to claim 1. The plurality of lenses constituting the third lens group includes an aspheric lens.
The projection optical system according to claim 1. The reflecting surface is a free-form surface or an aspheric surface,
The projection optical system according to claim 1.   An illumination optical system for irradiating light from a light source to the image forming unit;
  A projection optical system for enlarging and projecting the image formed on the image forming unit on the projection surface;
Have
  The projection optical system is the projection optical system according to any one of claims 1 to 10.
An image display device characterized by that.

Images