JP2015132723A - Projection optical system and image display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact projection optical system configured to significantly reduce projection distance and to enable image positioning.SOLUTION: A projection optical system for projecting an image formed by an image forming section on a projection surface includes, sequentially from a reduction side to an enlargement side, a dioptric system and a reflection optical system. The dioptric system includes a diaphragm, a free-form surface lens, and an optical element having at least one power. The reflection optical system includes at least one reflection optical element. When an axis shared by a plurality of axially symmetric lenses constituting the dioptric system is an axis A, the optical element can be moved in a direction vertical to the axis A.

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.

  There is known an image display device (projector) that projects an image formed by an image forming unit onto a screen that is a projection surface. Such a projector includes a projection optical system. The projection optical system is an optical system that enlarges and projects an image formed in the image forming unit on a screen.

  A DMD (Digital MicroMirror Device), a liquid crystal panel, or the like is used for the image forming unit of the projector. Among such projectors, there are projectors that have a shorter projection distance to the screen than conventional projectors. A projector capable of such ultra-short distance projection is called an ultra-short projection projector. Some ultra-short projection projectors can increase the image display size on the screen (capable of large screen display).

  As an ultrashort projection projector, a projector including a refractive optical system and a curved mirror is known (see, for example, Patent Document 1 to Patent Document 4).

  The projection optical system provided in the projectors of Patent Literature 1 to Patent Literature 4 is insufficient for the recent demand for high pixel number display.

  Since an ultra-short projection projector has a large projection angle, the change in the distance between the projector and the screen is very small, and the image size and image position on the screen change greatly. Therefore, it is difficult for the ultra-short projection projector to finely adjust the projected image position.

  Further, when the ultra-short projection projector is wall-mounted, a fastening member such as a bolt is usually used. With such a fastening member, it is particularly difficult to finely adjust the installation position in the height direction.

  As described above, in the ultra-short projection projector, there is a problem that it is difficult to adjust the image size and the installation position. The conventional projectors disclosed in Patent Documents 1 to 3 are insufficient to solve this problem.

  The projector of Patent Document 4 includes a method for adjusting the image position of a projection image. This image position adjustment method uses a part of the effective pixels of the image forming unit. That is, the projector disclosed in Patent Document 4 sacrifices resolution for adjusting the image position. If some of the effective pixels cannot be used for image formation, it will become more difficult to achieve the high pixel count display that has been required in recent years.

  Further, the projection optical system provided in the projector of Patent Document 4 requires an image circle that is considerably larger than the pixel range used for the projected image. Therefore, the size of the projection optical system becomes large. If the projection optical system becomes large, the projector as a whole cannot be reduced in size.

  Therefore, an object of the present invention is to provide a projection optical system in which the projection distance is very short, the image position can be adjusted, and the size can be reduced.

  The present invention is a projection optical system that projects an image formed on an image forming unit onto a projection surface, and includes a refractive optical system and a reflective optical system in order from the reduction side to the enlargement side, and the refraction The optical system includes a stop, a free-form surface lens, and an optical element having at least one power, and the reflection optical system includes at least one reflection optical element, and constitutes the refractive optical system. Of these lenses, when the axis shared by a plurality of target lenses is the axis A, the optical element can move in the direction perpendicular to the axis A.

  According to the present invention, it is possible to provide a projection optical system in which the projection distance is very short, the image position can be adjusted, and the size can be reduced.

1 is an optical layout diagram showing an embodiment of an image display device according to the present invention. It is the top view which looked at the image formation part with which the above-mentioned image display device is provided from the image formation side. It is an optical arrangement | positioning figure which shows the movement locus | trajectory of each lens group at the time of focusing in the projection optical system with which the said image display apparatus is provided. It is an example of the power distribution of the free-form surface lens with which the said projection optical system is provided, Comprising: (a) Power distribution figure of X-axis direction, (b) Power distribution figure of Y-axis direction. It is a figure which shows the field position corresponding to each view angle of the image formation part with which the said image display apparatus is provided. It is an example of the image on the screen at the time of the short distance projection which concerns on Example 1 of the said projection optical system. FIG. 7 is a diagram illustrating (a) bending at the upper side of the image, (b) bending at the left end of the image, and (c) bending at the lower end of the image in the image illustrated in FIG. 6. It is an example of the image on the screen at the time of the reference distance projection by the projection optical system which concerns on the said Example 1. FIG. FIG. 9 is a diagram illustrating (a) bending at the upper side of the image, (b) bending at the left end of the image, and (c) bending at the lower end of the image in the image illustrated in FIG. 8. It is an example of the image on the screen at the time of long distance projection by the projection optical system which concerns on the said Example 1. FIG. FIG. 11 is a diagram illustrating (a) bending at the upper side of the image, (b) bending at the left end of the image, and (c) bending at the lower end of the image in the image illustrated in FIG. 10. It is a spot diagram at the time of short distance projection in the projection optical system which concerns on the said Example 1. FIG. It is a spot diagram at the time of the reference distance projection in the projection optical system which concerns on the said Example 1. FIG. It is a spot diagram at the time of long-distance projection in the projection optical system concerning Example 1 above. It is an example of the image on the screen at the time of short distance projection by the projection optical system when the negative lens which concerns on Example 1 of the said projection optical system is shifted. In the image illustrated in FIG. 15, (a) bend at the upper side of the image, (b) bend at the left end of the image, and (c) bend at the lower end of the image. It is an example of the image on the screen at the time of the reference distance projection by the projection optical system when the negative lens which concerns on the said Example 1 is shifted. In the image illustrated in FIG. 17, (a) a curve at the upper side of the image, (b) a curve at the left end of the image, and (c) a curve at the lower end of the image. It is an example of the image on the screen at the time of long distance projection by the projection optical system when the negative lens which concerns on the said Example 1 is shifted. In the image illustrated in FIG. 19, (a) a curve at the upper side of the image, (b) a curve at the left end of the image, and (c) a curve at the lower end of the image. It is a spot diagram at the time of short distance projection in the projection optical system when the negative lens which concerns on the said Example 1 is shifted. It is a spot diagram at the time of the reference distance projection in the projection optical system when the negative lens which concerns on the said Example 1 is shifted. It is a spot diagram at the time of long-distance projection in a projection optical system when the negative lens which concerns on the said Example 1 is shifted. 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 the movement locus | trajectory of each lens group at the time of focusing in the projection optical system with which the said image display apparatus is provided. It is an example of the power distribution of the free-form surface lens with which the said projection optical system is provided, Comprising: (a) Power distribution figure of X-axis direction, (b) Power distribution figure of Y-axis direction. It is an example of the image on the screen at the time of the short distance projection which concerns on Example 2 of the said projection optical system. In the image illustrated in FIG. 27, (a) a curve at the upper side of the image, (b) a curve at the left end of the image, and (c) a curve at the lower end of the image. It is an example of the image on the screen at the time of the reference distance projection by the projection optical system which concerns on the said Example 2. FIG. In the image illustrated in FIG. 29, (a) a curve at the upper side of the image, (b) a curve at the left end of the image, and (c) a curve at the lower end of the image. It is an example of the image on the screen at the time of long distance projection by the projection optical system which concerns on the said Example 2. FIG. FIG. 32 is a diagram illustrating (a) a curve at the upper side of the image, (b) a curve at the left end of the image, and (c) a curve at the lower end of the image in the image illustrated in FIG. 31. It is a spot diagram at the time of short distance projection in the projection optical system concerning Example 2 above. It is a spot diagram at the time of reference distance projection in the projection optical system concerning Example 2 above. It is a spot diagram at the time of long-distance projection in the projection optical system concerning Example 2 above. It is an example of the image on the screen at the time of the short distance projection by the projection optical system when the cemented lens which concerns on Example 2 of the said projection optical system is shifted. In the image illustrated in FIG. 36, (a) a curve at the upper side of the image, (b) a curve at the left end of the image, and (c) a curve at the lower end of the image. It is an example of the image on the screen at the time of the reference distance projection by the projection optical system when the cemented lens which concerns on the said Example 2 is shifted. FIG. 39 is a diagram illustrating (a) bending at the upper side of the image, (b) bending at the left end of the image, and (c) bending at the lower end of the image in the image illustrated in FIG. 38. It is an example of the image on the screen at the time of long distance projection by the projection optical system when the cemented lens which concerns on the said Example 2 is shifted. In the image illustrated in FIG. 40, (a) a curve at the upper side of the image, (b) a curve at the left end of the image, and (c) a curve at the lower end of the image. It is a spot diagram at the time of short distance projection in the projection optical system when the cemented lens which concerns on the said Example 2 is shifted. It is a spot diagram at the time of the reference distance projection in the projection optical system when the cemented lens which concerns on the said Example 2 is shifted. It is a spot diagram at the time of long-distance projection in the projection optical system when the cemented lens according to Example 2 is shifted. It is a cross-sectional view of the refractive optical system with which the projection optical system which concerns on this invention is provided. It is a cross-sectional view of a refractive optical system showing an example of a lens driving mechanism provided in the refractive optical system.

  Embodiments of a projection optical system according to the present invention and an image display device according to the present invention will be described below with reference to the drawings. Here, the projection optical system according to the present invention projects the image formed on the image forming unit onto the projection surface. An image display device according to the present invention includes the projection optical system according to the present invention.

● Image display device (1)
First, an embodiment of an image display device according to the present invention will be described. FIG. 1 is an optical layout diagram of the image display apparatus according to the present embodiment. In FIG. 1, a projector 1 that is an image display device includes an image forming unit 10, a parallel plate 40, a projection optical system 100, 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 50.

  The projection optical system 100 includes a refractive optical system 101, and a flat mirror 102 and a concave mirror 103 that constitute the reflective optical system in order from the reduction side to the enlargement side.

  The refractive optical system 101 is composed of a plurality of lens groups. A detailed description of the refractive optical system 101 will be described later.

  The meanings of symbols used to describe the projection optical system 100 will be described. In addition, the meaning of each symbol shown below is used in common in description of embodiment described in this specification.

f: focal length of the entire projection optical system 100 NA: numerical aperture ω: half angle of view (deg)
R: radius of curvature (for aspheric surfaces, the paraxial radius of curvature)
D: Surface spacing Nd: Refractive index νd: Abbe number K: Aspherical conical constant Ai: i-th order aspherical constant Cj: Free-form surface coefficient C: Reciprocal of paraxial radius of curvature (paraxial curvature)
H: Height from the optical axis K: Conic constant

The aspherical shape is expressed by the following formula 1. Here, the aspherical shape represented by Equation 1 uses X as the light beam using the paraxial curvature C, the height H from the optical axis, the conic constant K, and the aspherical constant Ai of each order. Expressed as an aspherical amount in the axial direction.
(Formula 1)

  By giving the paraxial curvature C, the conic constant K, and the aspherical constant Ai to the above equation 1, the shape of the aspherical surface is specified.

ただし、ｊは以下の式３で表されるものである。
（式３）

In addition, the free-form surface shape is expressed as follows, using a paraxial curvature C, a height H from the optical axis, a conic constant K, and a free-form surface coefficient Cj, where X is a free-form surface amount in the optical axis direction. It is represented by Formula 2.
(Formula 2)

However, j is represented by the following formula 3.
(Formula 3)

  As illustrated in FIG. 1, an axis that is parallel to the normal direction of the image forming unit 10 and that is shared by a plurality of target lenses among the plurality of lenses included in the refractive optical system 101 is an “A axis”. And In addition, an axis perpendicular to the A axis among axes in a plane including a light beam emitted from the center of the image forming unit 10 and passing through the center of the diaphragm S included in the refractive optical system 101 is defined as a Y axis. An axis perpendicular to both the A axis and the Y axis is taken as an X axis.

  Note that, as shown in FIG. 1, the rotation direction in the clockwise direction with the X axis as the rotation axis is defined as the + α direction.

  Here, the image forming unit 10 will be described. FIG. 2 is a plan view of the image forming unit 10 as viewed from the image forming surface side. Note that a surface on which image information is formed in the image forming unit 10 is referred to as an image forming surface. As shown in FIG. 2, the image forming unit 10 is shifted in the Y-axis direction with respect to the A-axis.

Example 1
FIG. 1 is an optical path diagram in the case of 48 inches that the free curved lens 131 that is the front lens is extended most, and is projected from the image forming unit 10 through the projection optical system 100 onto the screen 200 that is the projection surface. It shows the optical path of the light. The refractive optical system 101 included in the projection optical system 100 includes a first lens group 11, a second lens group 12, and a third lens group 13.

  The refracting optical system 101 includes a first negative lens D12 (a lens included in the second lens group 12), which is located on the enlargement side with respect to the stop S of the first lens group 11 and is the third lens from the lens closest to the screen 200. It is movable in the Y-axis direction with respect to the axis.

  By moving the negative lens D12 in the Y axis direction with respect to the A axis, the image position on the screen 200 can be adjusted.

  Note that the direction in which the negative lens D12 can be moved to adjust the image position is not limited to the Y-axis direction, and may be movable in the X-axis direction. Moreover, you may move to XY direction.

Lens Driving Mechanism Here, a driving mechanism for the negative lens D12 that is one of the optical elements will be described. FIG. 45 is a transverse sectional view of the refractive optical system 101. As shown in FIG. 45, the refractive optical system 101 is held in the internal space of a hollow cylindrical holding member 1011. Further, a gap 1012 is formed between the inner diameter of the holding member 1011 that is the holding portion and the outer diameter of the negative lens D12 that is one of the optical elements. Since the gap 1012 is formed, a driving mechanism (not shown) can move the negative lens D12.

  FIG. 46 is a cross-sectional view of the refractive optical system 101 showing an example of a lens driving mechanism provided in the refractive optical system 101. As shown in FIG. 46, the lens driving mechanism includes a screw 1013 that penetrates the outer wall of the holding member 1011 from the outside of the holding member 1011 and contacts the outer edge of the negative lens D12 that is an optical element. The lens driving mechanism includes a spring 1014 fixed to the inner diameter of the holding member 1011 and in contact with the outer edge of the negative lens D12. The positions where the screw 1013 and the spring 1014 are in contact with the negative lens D12 are opposite to each other by 180 degrees.

  When the screw 1013 is tightened, the negative lens D12 is pushed by the screw 1013 and moved in the traveling direction of the screw 1013. Further, when the screw 1013 is loosened, the negative lens D12 is pushed by the elastic force of the spring 1014 and moved to the screw 1013 side. The direction in which the negative lens D12 is movable by the screw 1013 and the spring 1014 may be the Y-axis direction. The screw 1013 may be rotated by an electric motor (not shown), and the negative lens D12 may be moved electrically.

  In addition to this, various configurations can be adopted for the lens driving mechanism. For example, an operation lever is arranged outside the housing 50, a gear provided in the housing is rotated according to the operation of the operation lever, and the holding member 1011 of the negative lens D12 is driven according to the rotation of the gear, In response to this, the negative lens D12 may move in a predetermined direction. By providing such a movable adjustment mechanism, the user can move the negative lens D12 to an arbitrary position.

  Returning to FIG. 1, the projection optical system 100 will be described. As shown in FIG. 1, a free-form surface lens 131 is disposed at a position closest to the concave mirror 103 side of the projection optical system 100 among the lenses included in the refractive optical system 101. By disposing the free-form surface lens 131 at this position, it is possible to greatly enhance the effect of correcting distortion and field curvature. In addition, this free-form surface lens 131 can reduce the burden on other lenses included in the refractive optical system 101.

  Due to the effect of the free-form surface lens 131, the projection optical system 100 can be easily reduced in size and performance.

  Further, by using the free-form surface lens 131, it is possible to correct aberrations that occur when the negative lens D12 is decentered.

  Here, the “free-form surface” will be described. A free-form surface is that the curvature in the X-axis direction according to the position in the X-axis direction is not constant at any position in the Y-axis direction, and the Y-direction according to the position in the Y-axis direction at any position in the Y-axis direction. An anamorphic surface with a non-constant curvature.

  The image light formed by the image forming unit 10 passes through the projection optical system 100 and is projected onto the screen 200 to display an image. A light beam emitted from the image forming unit 10 passes through the refractive optical system 101. An intermediate image conjugate with the image information formed by the image forming unit 10 is formed by the light beam that has passed through the refractive optical system 101. This intermediate image is formed as an aerial image on the image forming unit 10 side with respect to the plane mirror 102. Note that the intermediate image does not have to be formed as a planar image, and may be formed as a curved image.

  An image is displayed on the screen 200 by enlarging and projecting the intermediate image by the concave mirror 103 arranged on the most enlargement side in the projection optical system 100. The intermediate image has field curvature and distortion, and these can be corrected by making the reflecting surface of the concave mirror 103 into a free-form surface. As a result, the burden of aberration correction on the refractive optical system 101 is reduced, which increases the degree of freedom in designing the projection optical system 100 and is advantageous for downsizing.

  In the projection optical system 100, a dustproof glass 104 is installed between the concave mirror 103 and the screen 200. The dustproof glass 104 is installed in the opening of the housing 50. The dustproof glass 104 may be a curved surface or an optical element having a power such as a lens.

  Next, a more detailed configuration of the refractive optical system 101 and the manner of focusing will be described. FIG. 3 is an optical layout diagram of the refractive optical system 101 included in the projection optical system 100. As shown in FIG. 3, the refractive optical system 101 includes a first lens group 11 having a positive refractive power and a second lens group 12 having a negative refractive power in order from the image forming unit 10 toward the enlargement side. , And a third lens group 13 composed of only a free-form surface lens 131. As shown in FIG. 1, the projection optical system 100 including the refractive optical system 101 has a concave mirror 103 that is a free-form surface mirror at the subsequent stage of the third lens group 13.

  In the refractive optical system 101, the second lens group 12 and the third lens group 13, which are negative lens groups, move to the enlargement side during focusing from the long distance side to the short distance side.

  The first lens group 11 includes, in order from the image forming unit 10 side, a double-sided aspheric positive meniscus lens having a convex surface facing the image forming unit 10 side, a biconvex lens having a strong convex surface on the enlargement side, and the image forming unit 10 side. A cemented lens of a biconcave lens having a strong concave surface, a biconvex lens having a strong convex surface on the image forming unit 10 side, a double-sided aspherical positive meniscus lens having a convex surface on the enlargement side, an aperture S, and the image forming unit 10 A cemented lens of a biconcave lens with a strong concave surface facing the side and a biconvex lens with a strong convex surface facing the image forming unit 10, a biconvex lens with a strong convex surface facing the magnification side, and a negative meniscus lens with a convex surface facing the magnification side And a biconvex lens having a stronger convex surface on the enlargement side.

  The second lens group 12 includes a double-sided aspheric positive meniscus lens having a convex surface facing the image forming unit 10 and a biconcave lens (negative lens) that is movable in the Y-axis direction and has a strong concave surface facing the image forming unit 10 side. D12). A double-sided aspherical biconcave lens having a stronger concave surface on the image forming unit 10 side.

  The third lens group 13 includes a free-form surface lens 131 whose surface on the concave mirror 103 side is rotationally asymmetric.

  Here, the power distribution of the free-form surface lens 131 will be described. 4A and 4B show an example of the power distribution of the free-form surface lens 131. FIG. 4A is a power distribution diagram in the X-axis direction, and FIG. 4B is a power distribution diagram in the Y-axis direction.

  The power distribution of the free-form surface lens 131 shown in FIG. 4 shows the X-axis power Px and the Y-axis power Py. FIG. 4 is obtained by differentiating an equation f (x, y) of a free-form surface with X and Y and calculating Px and Py at each coordinate (X, Y) by using the following equation 4.

(Formula 4)

  That is, the free-form surface lens 131 has a convex shape in the Y-axis direction and the X-axis direction, and the absolute value of the change amount of the Y-axis power is smaller than the absolute value of the change amount of the X-axis power. .

Next, specification data of the projection optical system 100 according to the first embodiment will be described. Table 1 shows lens (optical element) data of the projection optical system 100 according to the first embodiment. In Table 1, the surface number with “*” mark indicates an aspherical surface. A surface number with a “**” mark indicates a free-form surface. A surface number with a “*” mark indicates a lens that can be shifted in the Y-axis direction.
(Table 1)
Numerical aperture: 0.200

Table 2 is a specific example of the lens interval at the time of focusing of the projection optical system 100 according to the first embodiment.
(Table 2)
Variable interval focusing

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

Table 4 is a specific example of each numerical value of the free-form surface coefficient in the projection optical system 100 according to the present embodiment. The free-form surface is expressed by the above equation 2.
(Table 4)
Free-form surface coefficient

Table 5 shows specific examples of the image forming unit 10 in the projection optical system 100 according to the first embodiment. The image forming unit 10 according to the first embodiment is an example using DMD. The entrance pupil position in the projection optical system 100 is 58.48 mm. That is, the projection optical system 100 according to the present embodiment is a non-telecentric optical system.
(Table 5)

Table 6 shows the position coordinates of the plane mirror 102 and the concave mirror 103 from the apex of the lens located closest to the plane mirror 102 among the lenses of the projection optical system 100 in the in-focus state where the projection image is maximum. It is a specific example of the angle of α rotation. The rotation indicates an angle formed by the surface normal and the A axis.
(Table 6)

  Next, suppression of image degradation at each projection distance in the projection optical system 100 according to Example 1 will be described with reference to FIGS. 6 to 11 show an example in which an image showing a spot position with a wavelength of 550 nm is displayed on the screen 200 at each zoom position and each projection distance in the projection optical system 100 according to the first embodiment, and an image at each angle of view. It is a figure which illustrates distortion of.

  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 at the 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 projection optical system 100 at the time of projecting the reference distance. 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.

  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 during long-distance projection. 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.

  As described above, as shown in FIGS. 6 to 11, the projection optical system 100 according to the first embodiment can project an image with little distortion at each zoom and each projection distance.

  Next, it will be described with reference to FIGS. 12 to 14 that the change in the image is suppressed during zooming at each angle of view using the spot diagram in the projection optical system 100 according to the first embodiment. Each spot of the spot diaphragm shown in FIGS. 12 to 14 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. 12 is a spot diagram at the time of short-distance projection. FIG. 13 is a spot diagram when the reference distance is projected. FIG. 14 is a spot diagram during long distance projection.

  As shown in FIGS. 12 to 14, according to the projection optical system 100 according to the first embodiment, the variation in image quality at each zoom and each projection distance is suppressed.

  Next, suppression of image degradation when the negative lens D12 is shifted in the Y-axis direction at each projection distance of the projection optical system 100 according to Example 1 will be described with reference to FIGS. The shift amount of the negative lens D12 is 0.2 mm in the Y-axis direction.

  FIGS. 15 to 20 are diagrams showing an image showing the principal ray position at a wavelength of 550 nm and images showing the principal ray position on the screen at each zoom position and each projection distance in the projection optical system 100 according to the first embodiment. It is a figure which illustrates the distortion of the image in each view angle when it displays.

  FIG. 15 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 at the time of short distance projection in which the negative lens D12 is shifted in the Y-axis direction. FIG. 16 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. 17 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 at the time of projecting the reference distance with the negative lens D12 shifted in the Y-axis direction. FIG. 18 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. 19 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 during long distance projection in which the negative lens D12 is shifted in the Y-axis direction. FIG. 20 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.

  As described above, as shown in FIGS. 15 to 20, according to the projection optical system 100 according to the present embodiment, even if the negative lens D <b> 12 is shifted (decentered), there is distortion at each zoom and each projection distance. A small number of images can be projected.

  Next, in the projection optical system 100 according to Example 1, the change in the image is suppressed even when the negative lens D12 is shifted in the Y-axis direction using the spot diagram, as shown in FIGS. Will be described. The shift amount of the negative lens D12 is 0.2 mm in the Y-axis direction.

  Each spot of the spot diaphragm shown in FIGS. 21 to 23 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. 21 is a spot diagram at the time of short distance projection in which the negative lens D12 is shifted in the Y-axis direction. FIG. 22 is a spot diagram at the time of reference distance projection in which the negative lens D12 is shifted in the Y-axis direction. FIG. 23 is a spot diagram during long distance projection in which the negative lens D12 is shifted in the Y-axis direction.

  As shown in FIGS. 21 to 23, according to the projection optical system 100 according to the first embodiment, even when the negative lens D12 is shifted (decentered) in the Y-axis direction, image quality at each zoom and each projection distance is obtained. The fluctuation of is suppressed.

The shift amount of the image position when the negative lens D12 is shifted by 0.2 mm is as follows.

● Image display device (2)
Next, another embodiment of the image display apparatus according to the present invention will be described. FIG. 24 is an optical layout diagram of the image display apparatus according to the present embodiment. In FIG. 24, the projector 1 that is an image display device includes an image forming unit 10, a parallel plate 40, a projection optical system 100, an illumination optical system 20 that includes 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 50.

  The projection optical system 100 includes a refractive optical system 101, a plane mirror 102, and a concave mirror 103.

  As shown in FIG. 24, an axis that is parallel to the normal direction of the image forming unit 10 and that is shared by a plurality of target lenses among a plurality of lenses included in the refractive optical system 101 is an “A axis”. And In addition, an axis perpendicular to the A axis among axes in a plane including a light beam emitted from the center of the image forming unit 10 and passing through the center of the diaphragm S included in the refractive optical system 101 is defined as a Y axis. An axis perpendicular to both the A axis and the Y axis is taken as an X axis.

  As shown in FIG. 24, the rotation direction in the clockwise direction with the X axis as the rotation axis is the + α direction.

Example 2
FIG. 24 is an optical path diagram in the case where the front curved surface free-form lens 131 is extended to 48 inches, and is projected from the image forming unit 10 through the projection optical system 100 onto the screen 200 as the projection surface. It shows the optical path of the light. The refractive optical system 101 includes a first lens group 11, a second lens group 12, and a third lens group 13.

  In the refractive optical system 101, a cemented lens D11 (lens included in the first lens group 11) having a first negative power is located on the enlargement side with respect to the aperture stop S included in the first lens group 11, and the A-axis. Is movable in the Y-axis direction.

  By moving the cemented lens D11 in the Y-axis direction with respect to the A-axis, the image position on the screen 200 can be adjusted.

  Note that the direction in which the cemented lens D11 is movable in order to adjust the image position is not limited to the Y-axis direction, and may be movable in the X-axis direction. Moreover, you may move to XY direction.

  The driving mechanism of the cemented lens D11 is the same as the driving mechanism applicable to the projection optical system 100 according to the first embodiment that has already been described.

  As shown in FIG. 24, a free-form surface lens 131 is disposed at a position closest to the concave mirror 103 of the projection optical system 100 among the lenses included in the refractive optical system 101. By disposing the free-form surface lens 131 at this position, it is possible to greatly enhance the effect of correcting distortion and field curvature. In addition, this free-form surface lens 131 can reduce the burden on other lenses included in the refractive optical system 101.

  By using such a free-form surface lens 131, the above effects can be obtained, and the projection optical system 100 can be easily reduced in size and performance.

  Further, by using the free-form surface lens 131, it is possible to correct aberrations that occur when the cemented lens D11 is decentered.

  Here, the “free-form surface” will be described. A free-form surface is that the curvature in the X-axis direction according to the position in the X-axis direction is not constant at any position in the Y-axis direction, and the Y-direction according to the position in the Y-axis direction at any position in the Y-axis direction. An anamorphic surface with a non-constant curvature.

  An intermediate image conjugate with the image information formed by the image forming unit 10 is formed by the light beam that has passed through the refractive optical system 101. This intermediate image is formed as an aerial image on the image forming unit 10 side with respect to the plane mirror 102. Note that the intermediate image does not have to be formed as a planar image, and may be formed as a curved image.

  The intermediate image is enlarged and projected by the concave mirror 103 arranged on the most enlargement side in the projection optical system 100, whereby an image is displayed on the screen. The intermediate image has field curvature and distortion, and these can be corrected by making the reflecting surface of the concave mirror 103 into a free-form surface. As a result, the burden of aberration correction on the refractive optical system 101 is reduced, which increases the degree of freedom in designing the projection optical system 100 and is advantageous for downsizing.

  Further, the projection optical system 100 installs a dustproof glass 104 between the concave mirror 103 and the screen 200. The dustproof glass 104 is installed in the opening of the housing 50. The dust-proof glass 104 may be a curved surface, or an optical element having power such as a lens may be used.

  Next, a more detailed configuration of the refractive optical system 101 and the manner of focusing will be described. FIG. 25 is an optical layout diagram of the refractive optical system 101 included in the projection optical system 100. As shown in FIG. 25, the refractive optical system 101 includes a first lens group 11 having a positive refractive power and a second lens group 12 having a negative refractive power in order from the image forming unit 10 toward the enlargement side. , And a third lens group 13 composed of only a free-form surface lens 131. As shown in FIG. 1, the projection optical system 100 including the refractive optical system 101 has a concave mirror 103 that is a free-form surface mirror following the third lens group 13.

  In the refractive optical system 101, the second lens group 12 and the third lens group 13, which are negative lens groups, move to the enlargement side during focusing from the long distance side to the short distance side. That is, in the refractive optical system 101 according to the present embodiment, an optical element that is movable perpendicularly to the axis A is included in a (fixed) lens group that does not move during focusing.

  The first lens group 11 includes, in order from the image forming unit 10 side, a double-sided aspherical positive meniscus lens having a convex surface facing the image forming unit 10, a biconvex lens having a strong convex surface on the enlargement side, and the image forming unit 10 side. A cemented lens of a biconcave lens having a strong concave surface, a biconvex lens having a strong convex surface on the image forming unit 10 side, a double-sided aspherical positive meniscus lens having a convex surface on the enlargement side, an aperture S, and the image forming unit 10 A cemented lens D11 of a biconcave lens having a strong concave surface directed toward the side and a biconvex lens having a strong convex surface directed toward the image forming unit 10, a biconvex lens having a strong convex surface directed toward the magnification side, and a negative meniscus having a convex surface directed toward the magnification side And a biconvex lens having a stronger convex surface on the enlargement side.

  The second lens group 12 has a double-sided aspherical positive meniscus lens with a convex surface facing the image forming unit 10, a biconcave lens with a strong concave surface facing the image forming unit 10, and a strong concave surface facing the image forming unit 10 side. A double-sided aspherical biconcave lens.

  The third lens group 13 includes a free-form surface lens 131.

  Here, the power distribution of the free-form surface lens 131 will be described. FIGS. 26A and 26B are an example of power distribution of the free-form surface lens 131 according to the present embodiment, (a) a power distribution diagram in the X-axis direction, and (b) a power distribution diagram in the Y-axis direction.

  The power distribution shown in FIG. 26 shows the X-axis power Px and the Y-axis power Py. FIG. 26 is obtained by differentiating the equation f (x, y) of the free-form surface with X and Y, and calculating Px and Py at each coordinate (X, Y) using Equation 5 below.

(Formula 5)

Next, specification data of the projection optical system 100 according to the second embodiment will be described. Table 7 shows lens (optical element) data of the projection optical system 100 according to Example 2. In Table 7, the surface number marked with “*” indicates an aspherical surface. A surface number with a “**” mark indicates a free-form surface. A surface number with a “*” mark indicates a lens that can be shifted in the Y-axis direction.
(Table 7)
Numerical aperture: 0.200

Table 8 is a specific example of the lens interval at the time of focusing of the projection optical system 100 according to the second embodiment.
(Table 8)
Variable interval focusing

Table 9 is a specific example of each numerical value of the aspheric coefficient in the projection optical system 100 according to the second embodiment. The aspheric surface is expressed by the above formula 1.
(Table 9)
Aspheric coefficient

Table 10 is a specific example of each numerical value of the free-form surface coefficient in the projection optical system 100 according to the present embodiment. The free-form surface is expressed by the above equation 2.
(Table 10)
Free-form surface coefficient

Table 11 shows specific examples of the image forming unit 10 in the projection optical system 100 according to the present embodiment. The image forming unit 10 according to the second embodiment is an example using DMD. The entrance pupil position in the projection optical system 100 is 58.48 mm. That is, the projection optical system 100 according to the present embodiment is a non-telecentric optical system.
(Table 11)

Table 12 shows the position coordinates of the plane mirror 102 and the concave mirror 103 from the apex of the lens located closest to the plane mirror 102 among the lenses of the projection optical system 100 in the in-focus state where the projection image is maximum. It is a specific example of the angle of α rotation. The rotation indicates an angle formed by the surface normal and the A axis.
(Table 12)

  Next, suppression of image degradation at each projection distance in the projection optical system 100 according to Example 2 will be described with reference to FIGS. FIGS. 27 to 32 show an example in which an image showing a principal ray position of a wavelength of 550 nm is displayed on the screen 200 at each zoom position and each projection distance in the projection optical system 100 according to the second embodiment, and at each angle of view. It is a figure which illustrates distortion of an image.

  FIG. 27 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 at the time of short distance projection. FIG. 28 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. 29 is an example of an image showing a spot position of a wavelength of 550 nm displayed on the screen in the projection optical system 100 at the time of projecting the reference distance. FIG. 30 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. 31 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 during long-distance projection. FIG. 32 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. 31.

  As described above, as shown in FIGS. 27 to 32, the projection optical system 100 according to the second embodiment can project an image with little distortion at each zoom and each projection distance.

  Next, it will be described with reference to FIGS. 33 to 35 that the change in the image is suppressed during zooming at each angle of view using the spot diagram in the projection optical system 100 according to the second embodiment. Each spot of the spot diaphragm shown in FIGS. 33 to 35 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. 33 is a spot diagram at the time of short-distance projection. FIG. 34 is a spot diagram during reference distance projection. FIG. 35 is a spot diagram during long distance projection.

  As shown in FIGS. 33 to 35, according to the projection optical system 100 according to the first embodiment, fluctuations in image quality at each zoom and each projection distance are suppressed.

  Next, suppression of image degradation when the cemented lens D11 is shifted in the Y-axis direction at each projection distance of the projection optical system 100 according to the present embodiment will be described with reference to FIGS. The shift amount of the cemented lens D11 is 0.1 mm in the Y-axis direction.

  FIGS. 36 to 41 are diagrams showing an image showing the principal ray position at a wavelength of 550 nm and images showing the principal ray position on the screen at each zoom position and each projection distance in the projection optical system 100 according to the second embodiment. It is a figure which illustrates the distortion of the image in each view angle when it displays.

  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 100 at the time of short distance projection in which the cemented lens D11 is shifted in the Y-axis direction. 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 100 at the time of reference distance projection in which the cemented lens D11 is shifted in the Y-axis direction. 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.

  FIG. 40 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 during long-distance projection in which the cemented lens D11 is shifted in the Y-axis direction. FIG. 41 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.

  As described above, as shown in FIGS. 36 to 41, according to the projection optical system 100 according to the present embodiment, even when the cemented lens D11 is shifted (decentered), distortion is caused at each zoom and each projection distance. A small number of images can be projected.

  Next, it will be described with reference to FIGS. 42 to 44 that the change in the image is suppressed during zooming at each angle of view using the spot diagram in the projection optical system 100 according to the present embodiment. Each spot of the spot diaphragm shown in FIGS. 42 to 44 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. 42 is a spot diagram at the time of short-distance projection in which the cemented lens D11 is shifted in the Y-axis direction. FIG. 43 is a spot diagram at the time of reference distance projection in which the cemented lens D11 is shifted in the Y-axis direction. FIG. 44 is a spot diagram at the time of long-distance projection in which the cemented lens D11 is shifted in the Y-axis direction.

  As shown in FIGS. 42 to 44, according to the projection optical system 100 according to the second embodiment, even if the cemented lens D11 is shifted (decentered), fluctuations in image quality at each zoom and each projection distance are suppressed. Has been.

The shift amount of the image position when the cemented lens D11 is shifted by 0.1 mm is shown below.

  In the projection optical system 100 specified by the specific numerical examples shown in the first and second embodiments described above, the optical element (lens) on the enlargement side with respect to the stop S is moved in the vertical direction (Y-axis direction). To move. By using the projection optical system 100 that can move this optical element, it is possible to obtain an image projection apparatus that is small in size, has little performance deterioration, and can move the image position.

  In addition, each Example mentioned above shows the suitable Example of this invention. Therefore, the present invention is not limited to the contents. In particular, the specific shapes and values of the parts exemplified in the examples are only examples of the implementations performed in carrying out the present invention, and thus the technical scope of the present invention is interpreted in a limited manner. There must not be.

  Thus, the present invention is not limited to the contents described using the embodiments, and can be appropriately changed without departing from the gist thereof.

  Hereinafter, main features of the projection optical system and the image display apparatus according to the present invention described in the above embodiment will be described.

● Feature 1
A projection optical system according to the present invention is a projection optical system that projects an image formed on an image forming unit onto a projection surface, and includes a refractive optical system and a reflective optical system in order from the reduction side to the enlargement side. The refractive optical system includes a stop, a free-form surface lens, and an optical element having at least one power; the reflective optical system includes at least one reflective optical element; Among the plurality of lenses constituting the system, when the axis shared by a plurality of target lenses is an axis A, the optical element is movable in a direction perpendicular to the axis A. Do

  By making it possible to move the optical element having power (negative lens D12 or cemented lens D11), the image position can be moved by the prism action. Further, by using a free-form surface lens, it is possible to effectively correct decentration aberrations that occur when the optical element is moved.

  In a conventional projector that can adjust the image position, the image position is adjusted by moving the entire optical system. Such a projector is increased in size, and particularly in a mirror optical system, it causes interference of light rays and an increase in the size of a moving mechanism.

  In this respect, the projection optical system according to the present invention and the image display apparatus including the projection optical system enable the movement adjustment of the image position by moving one of the optical elements included in the projection optical system. . For this reason, not only the image display apparatus can be reduced in size and the moving mechanism can be simplified, but also the performance deterioration after the image position adjustment can be reduced.

● Feature 2
In addition to the feature 1, the projection optical system according to the present invention further includes an in-plane axis including a light beam that is emitted from the center of the image forming unit and passes through the center of the stop included in the refractive optical system, When the axis perpendicular to the A axis is the Y axis and the axis perpendicular to the A axis and the Y axis is the X axis, the surface of the free-form surface lens is rotationally asymmetric on the concave mirror side, and the Y axis And the absolute value of the power change amount in the Y-axis direction is smaller than the absolute value of the power change amount in the X-axis direction.

  According to this feature, when the optical element is decentered in the Y direction, the amount of change in power in the Y direction can be reduced. Thus, the reason for reducing the amount of change in the power in the Y direction is that the change in the light beam position on the free-form surface lens is sensitive to the X direction. By reducing the amount of change in power in the Y direction, the occurrence of decentration aberrations can be suppressed.

● Feature 3
The projection optical system according to the present invention is characterized in that, in addition to the features 1 and 2, the optical element moves along the Y axis.

  According to this feature, since adjustment in the Y-axis direction is particularly difficult, the movement mechanism can be simplified by only moving in the Y-axis direction. In addition, an image display device including a projection optical system having this feature can reduce the size and cost of the image display device.

● Feature 4
The projection optical system according to the present invention is characterized in that, in addition to the features 1 to 3, the optical element is disposed closer to the reflective optical element than the stop.

  According to this feature, by arranging the image position adjusting optical element on the enlargement side with respect to the stop, the occurrence of decentration aberration is reduced and the image position can be adjusted.

● Feature 5
The projection optical system according to the present invention is characterized in that, in addition to features 1 to 4, the reflective optical element is a concave mirror and has a free-form surface.

  According to this feature, by using a concave free-form surface mirror, together with the effect of the free-form surface lens, it becomes possible to effectively correct the decentration aberration of the optical element.

● Feature 6
The projection optical system according to the present invention is characterized in that, in addition to the features 1 to 5, the optical element has a negative power.

  According to this feature, the image position can be effectively moved by moving the optical element having negative power.

● Feature 7
The projection optical system according to the present invention is characterized in that, in addition to features 1 to 6, the refractive optical system further includes a drive mechanism for moving the optical element.

  According to this feature, by providing a drive mechanism for decentering the optical element, any decentering can be easily performed.

● Feature 8
In the projection optical system according to the present invention, in addition to features 1 to 7, the refractive optical system further includes a gap between the inner diameter of the holding portion of the optical element and the outer diameter of the optical element. It is characterized by.

  According to this feature, it is possible to adjust the image position without having a complicated mechanism.

● Feature 9
The projection optical system according to the present invention further includes a plurality of lens groups in addition to the characteristics 1 to 8, and the optical element is included in a lens group that does not move during focusing among the plurality of lens groups. It is characterized by that.

  According to this feature, the moving mechanism can be simplified by moving the optical element included in the lens group fixed at the time of focusing, so that the apparatus can be downsized.

● Feature 10
The projection optical system according to the present invention is characterized in that, in addition to the features 1 to 9, the projection optical system is a non-telecentric optical system.

  According to this feature, the non-telecentric optical system is advantageous for downsizing.

● Feature 11
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 any one of the features 1 to 10 described above.

  According to this feature, it is possible to obtain an image display device in which the projection distance is very short, the image position can be adjusted with a small size, and the performance change is small.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 11 1st lens group 12 2nd lens group 13 3rd lens group 100 Projection optical system 101 Refraction optical system 102 Plane mirror 103 Concave mirror

JP 2007-079524 A JP 2009-251458 A JP 2011-242606 A JP 2009-216883 A

Claims (11)

A projection optical system that projects an image formed on an image forming unit onto a projection surface,
In order from the reduction side to the enlargement side, it has a refractive optical system and a reflective optical system,
The refractive optical system is
Aperture,
A free-form surface lens,
An optical element having at least one power;
Have
The reflective optical system has at least one reflective optical element,
Among the plurality of lenses constituting the refractive optical system, when an axis shared by a plurality of lenses targeted for the axis is an axis A,
The optical element is movable in a direction perpendicular to the axis A;
A projection optical system characterized by that. An axis in a plane including a light beam emitted from the center of the image forming unit and passing through the center of the stop included in the refractive optical system, and an axis perpendicular to the A axis is a Y axis,
When the X axis is an axis perpendicular to the A axis and the Y axis,
The free-form surface lens is
The surface on the concave mirror side is rotationally asymmetric,
Convex shapes in the Y-axis direction and the X-axis direction,
The absolute value of the power change amount in the Y-axis direction is smaller than the absolute value of the power change amount in the X-axis direction;
The projection optical system according to claim 1. The optical element moves along the Y axis;
The projection optical system according to claim 2. The optical element is disposed closer to the reflective optical element than the diaphragm.
The projection optical system according to claim 1. The reflective optical element is a concave mirror and has a free-form surface;
The projection optical system according to claim 1. The optical element has a negative power;
The projection optical system according to claim 1. The refractive optical system is
A drive mechanism for moving the optical element;
The projection optical system according to claim 1. The refractive optical system is
There is a gap between the inner diameter of the holding portion of the optical element and the outer diameter of the optical element,
The projection optical system according to claim 1. With multiple lens groups,
The optical element is included in a lens group that does not move during focusing among the plurality of lens groups.
The projection optical system according to claim 1. The projection optical system is a non-telecentric optical system;
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.

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