JP3275634B2 - Projection optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical apparatus for enlarging and projecting an object plane provided by a film image, a video image or the like on a screen.

[0002]

2. Description of the Related Art Various projection optical devices for enlarging and projecting a film image, a video image, and the like on a screen have been developed so far. Therefore, a method of projecting an image obliquely to the screen has been proposed in order to suppress the enlargement of the projection optical system while achieving the enlargement of the screen.

However, when an image is projected obliquely to the screen, a so-called trapezoidal distortion occurs in the projected image.
Various proposals have been made to correct this. For example, Japanese Unexamined Patent Publication No. Hei 3-84515 discloses a method in which a trapezoidal distortion generating optical system is inserted between a projection lens and an image display device, and an image in which reverse trapezoidal distortion is given by the trapezoidal distortion generating optical system is temporarily formed on an intermediate screen. It is stated that trapezoidal distortion of the final projected image can be suppressed by forming an image and obliquely projecting this on a final screen by a projection lens.

Japanese Patent Laid-Open No. Hei 3-113432 discloses that
A correction optical system and a correction optical system driving device are provided on the projection lens, and the correction optical system is decentered by, for example, parallel decentering in the vertical direction with respect to the optical axis of the projection lens to intentionally generate eccentric distortion. It can be used to correct trapezoidal distortion. Japanese Unexamined Patent Publication No. 3-141337 discloses a device for eccentrically driving a part of the projection lens. By driving and eccentrically driving at least two of the projection lenses, the eccentric distortion is generated. According to the document, the trapezoidal distortion of the image on the final screen and the movement of the origin can be corrected.

Further, Japanese Patent Laid-Open No. 5-100312 discloses that a light valve and a screen for displaying an image by a liquid crystal display or the like are displaced in parallel with each other and in directions opposite to each other with respect to the optical axis of the projection optical system. By disposing a light valve and a screen, forming a projection lens with a wide-angle lens having a large angle of view, and using a part of the angle of view of the wide-angle lens, a projection image without distortion can be obtained.

[0006]

However, each of the projection optical devices described in the above publications has drawbacks in terms of specificity and practicality. For example, JP-A-3-84515 discloses that
No specific configuration and numerical data are disclosed for the trapezoidal distortion generating optical system. In addition, an image with inverted trapezoidal distortion given by the trapezoidal distortion generating optical system is once formed on an intermediate screen, and this is projected obliquely on the final screen by a projection lens. It becomes.

In Japanese Patent Application Laid-Open No. 3-113432, distortion is corrected without considering only eccentric distortion caused by eccentric driving of the correction optical system up to the third order or region. It is difficult to achieve sufficient aberration correction because it does not mention aberration correction. Japanese Patent Laid-Open No. 3-141337 discloses that at least two of the projection lenses are driven and decentered to generate eccentric distortion, thereby correcting the trapezoidal distortion of the image on the final screen. Publication (Example)
In the parallel eccentricity of the two lenses disclosed in the above section, it is difficult to satisfy the actual requirement because aberration cannot be sufficiently taken.

Further, in Japanese Patent Application Laid-Open No. Hei 5-100312, only a part of the angle of view of a projection lens is used to project an image on a screen, so that the cost is relatively high. There are still problems such as not being able to take a large plane tilt. Therefore, the present invention is directed to a projection optical apparatus for enlarging and projecting an image of an object plane provided by a film image, a video image, and the like on a screen, and obtaining a projection image in which trapezoidal distortion and distortion are sufficiently corrected. It is an object of the present invention to provide a practical projection optical device that can be provided at a low cost and can be reduced in size.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is a projection optical apparatus for enlarging and projecting an image of an object plane on a screen, and comprises a stop and an object plane adjacent to the stop. A projection optical system including an axial system lens group and a coaxial system lens group on the screen side, wherein the projection optical system forms no real image up to the final image plane on the screen, and the object plane side adjacent to the stop. Lens unit magnification β ₁ is | 1
/ Β ₁ | <meets the 0.05 conditions of, the Subscription
The lens group of the coaxial system on the zoom side
A projection optical apparatus is provided , wherein the two lens groups are decentered from each other by being rotationally decentered .

Here, “magnification β ₁ of the lens group on the object plane side adjacent to the stop” means a paraxial magnification determined under the Scheimpflug condition with respect to the center point of the object plane. According to the projection optical device of the present invention, an object plane provided by a film image, a video image, or the like is enlarged and projected on a screen. The projection optical system in this optical device has an optical system having a decentered lens group. In this system, a real image is not formed up to the final image plane. With this configuration, the overall length of the projection optical system can be shortened, and the entire apparatus can be reduced in size.

The paraxial magnification β ₁ determined by the Scheimpflug condition with respect to the center point of the object plane of a lens group forming a coaxial system on the object plane side adjacent to the stop is given by
While satisfying the condition of 1 / β ₁ | <0.05,
The coaxial lens group on the screen side is located at the center of the diaphragm.
Since the two lens groups adjacent to the stop are eccentric to each other due to the rotational eccentricity about the center, the image plane is rotated by the eccentricity in a portion which is substantially parallel to the stop. Since the lens groups before and after the stop are decentered with respect to the substantially parallel light, aberration correction almost equivalent to the aberration correction in the coaxial system is partially performed, and a practically good final projection image is obtained with a small number of lenses. Aberration correction (coma,
Correction of trapezoidal distortion and distortion) is achieved. further,
The light incident on the aperture is made almost parallel light, and the lens group before and after the aperture
Eccentricity is defined as rotational eccentricity with the center of rotation as the rotation center
Therefore, when viewed from the aperture direction, the lens before and after the aperture
Because the intermediate image plane for the group is almost infinite,
Even if the symmetry is not destroyed, and the image plane can be rotated
Eccentricity, because it is possible to make it more similar in design to a coaxial system.
Aberration correction is possible with a small number of lenses despite the system
Become. Furthermore, in the conventional decentered optical system, the rotation of the image plane
Required complicated movement of the lens group for
With such a projection optical system, good results are obtained as the rotational eccentricity increases.
Because the image plane can be rotated while maintaining the image relationship,
The advantage is that the image plane can be rotated by simply rotating the lens group.
is there.

Further, since aberration can be sufficiently corrected with such a small number of lenses and without employing an additional optical system for the projection optical system as in the conventional apparatus, the entire apparatus can be provided at low cost. Here, the magnification β ₁ (magnification of Scheimpflug with respect to the center of the object plane) of the lens group on the object plane side from the stop will be further described. As described above, the conditional expression of | 1 / β ₁ | <0.05 is satisfied. It is desirable that, if it is out of this range, the light passing through the stop is likely to be convergent light or divergent light, and the deviation from the parallel light will be large, so that it will be intermediate at a distance closer to the lens group on the image plane side. As a result of forming the image plane, if the image plane is rotated due to the eccentricity of the lens group, the intermediate image plane inclined to the lens group on the image plane side from the aperture is projected onto the screen (relaying if necessary). This is because aberration correction becomes difficult unless a large number of lenses are used, and the overall length of the projection optical system becomes longer.

The projection optical device according to the present invention is as follows.
~ Can be exemplified. The object side
The aperture position of the lens group is determined by the focal position of the lens group.
Projection light with the object plane side telecentric system
Equipment. The aperture position of the lens group on the object plane side
Is located at the focal position of the lens group, and the object plane side is telecentric.
By using a trick system, each point on the object plane (for example, liquid crystal display
From each pixel point on the image display surface of the device, etc.
The angle of the light incident on the
LCD devices and dichroic mirrors with different light transmission characteristics
It can also be applied to color synthesis optical systems.

[0014]  The two lasers provided adjacent to the aperture
All have substantially f-θ characteristics when viewed from the aperture side.
A projection optical device comprising a lens group.

Here, the lens group having the f-θ characteristic is as follows.
Generally called fθ lens (F-theta lens)
The image height is proportional to the light incident tilt angle θ to the lens.
Things. Note that f is the focal length. like this
In addition, each of the lens groups before and after the aperture is not viewed from the aperture side.
These are also constituted by a lens group having substantially f-θ characteristics.
The f-θ lens group adjusts the light incident angle and image height from the stop side.
A proportional relationship holds. For this reason, the angle of the light beam on the aperture side changes.
The relationship between the image heights does not change. this
Therefore, the f-θ lens system is rotated around the aperture position as the rotation center.
Trapezoidal distortion due to simple movement of lens group
Image plane while maintaining the state of correction of various aberrations such as curvature and coma
Can be rotated.  The projection optical system is most
Partially coaxial lens group with magnification on the image side
And the angle θ between the symmetry axis of the lens group and the image plane_One Is
Projection optical device that satisfies the following conditions.

| Θ ₁ | <5 ° In the projection optical apparatus of the present invention, when it is desired to obtain a wider angle of view, it is effective to employ a lens unit having a magnification on the image plane side. Further, in order to prevent trapezoidal distortion from being caused by the lens group having this magnification, the angle θ ₁ between the symmetry axis of this lens group and the final image plane may be set to the above condition.

If the condition of | θ ₁ | <5 ° is not satisfied, the trapezoidal distortion generated in this lens group becomes large, and it becomes difficult to correct the distortion in the lens group preceding this lens group.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 relate to one embodiment of the present invention.
FIG. 1 is a sectional view of a lens group in a projection optical system of a projection optical apparatus according to a first embodiment, and FIG. 2 is a diagram showing a schematic configuration of a projection optical apparatus having the projection optical system and its optical path. FIG. 3 is a spot diagram showing a point at which a ray coming from an object point on the object plane cuts the image plane on the screen. FIG. 4 is a projection distortion image (image shown by a solid line) on the screen and an ideal image without distortion (broken line). FIG.

As shown in FIG. 2 , the image display apparatus 1 of this embodiment provides an object plane 10 to be enlarged and projected.
And a projection optical system P1 and a screen 5 for forming the final image plane 50. The object plane 10 here is one side 4
This is a 0 mm square object plane (grating pattern). The projection optical system P1 includes a stop 2, and lens groups 3 and 4 disposed adjacent to and before and after the stop 2.

For the lens group 3 on the object side, the stop 2
The position is located at the focal position of the lens group, and the object plane side is a telesetrick system. The lens group 3 closer to the object plane than the diaphragm 2 is a coaxial lens group including lenses 31, 32, and 33 exhibiting f-θ characteristics in the entire lens group. The lens group 4 closer to the image plane than the diaphragm 2 is a coaxial lens group including lenses 41, 42, 43, and 44 exhibiting f-θ characteristics in the entire lens group.

For the f-θ lens group 3 on the object plane side ,
The position of the object point on the object plane 10 on the image display device 1 (hereinafter referred to as “object height”) is proportional to the exit angle on the aperture 2 side (the tilt angle of the exit light with the optical axis of the lens group 3). . As for the f-θ lens group 4 on the image plane side, the position of the image point on the final image plane 50 (hereinafter, referred to as “image height”) and the incident angle (the tilt angle between the incident light and the optical axis of the lens group 4) are determined. They are arranged in proportion to each other, and are eccentrically rotated by a predetermined angle around the center of the incident light as a rotation center, whereby the final image plane 50 can be rotated. That is, the lens group 4 passes through the intersection of the plane including the diaphragm 2 and the optical axis of the lens group 4 (here, the diaphragm 2 is circular, so the center of the diaphragm)
It is rotationally eccentric about an axis parallel to the Z axis described later.

The magnification β ₁ of the lens unit 3 on the object plane side is | 1
/ Β ₁ | = 8.446 × 10 ⁻⁵ <0.05. Lens group 3, lens group 4, and object plane 10
And specifications regarding the image plane 50 are as shown in Table 1. In Table 1, “r1... R6, r7.
As shown in FIG. 1, lens surfaces of the lenses 31 to 33 and 41 to 44 are shown, and “radius of curvature” is a radius of curvature (unit: mm) of each lens surface. Is indicated as “positive” and the concave surface is indicated as “negative”. The “axis top surface interval” is a distance (unit: mm) on the optical axis between adjacent lens surfaces and between the lens surface and the diaphragm.
The “refractive index” is the refractive index of each substance between adjacent lens surfaces (behind the lens surface closest to the image plane of the lens group) and between the lens surface and the diaphragm. No lens means that the substance is air.

The aperture has an infinite radius of curvature (∞), which is also shown in Table 1 together with the aperture radius (unit: mm). In Table 1, “lens group 3”, “lens group 4”,
Numerical values of X, Y, and Z shown in the display columns of “object plane” and “image plane” indicate the lens surface and the diaphragm closest to the object plane (r1 and diaphragm 2 in FIG. ), The (X, Y, Z) coordinate position of the surface vertex and the aperture center, and the object surface,
The (X, Y, Z) coordinate position of the image plane is shown. In this embodiment and other embodiments described later, (X, Y, Z)
The X axis in the (Y, Z) coordinates is the optical axis direction of the lens (positive in the light traveling direction) with the vertex of the lens closest to the object plane 10 (the vertex of the lens 31 in the example shown in FIG. 1) as the origin. , Y axis is a vertical axis perpendicular to the X axis, and Z axis is X axis.
The direction perpendicular to both the axis and the Y axis (in this case, the direction perpendicular to the page)
Axis. “ANG” indicates the rotational eccentric angle (unit degree) of the lens group 3 and the aperture 2 with respect to the X axis, and the object plane and the image plane indicate the inclination angles with respect to the X axis. In each case, the clockwise direction in the figures is “positive”.

In the column of the object plane, ymax, ymin
Indicates the area of the object plane in the Y-axis direction, and zmax and zmin indicate the areas of the object plane in the Z-axis direction.

[0025]

[Table 1] The distortion at the final image plane 50 is as shown in the following table. In the following table, the "object height" is represented by a coordinate in terms of a distance in the Y-axis direction and a distance in the Z-axis direction (both in mm) from the point at which the X axis passes through the object plane 10 to the object point. are doing. The “image height” is defined as a point at which a ray from the object plane center (0, 0) passes through the image plane 50 as an origin.
The straight line intersecting 0 is determined by (y, z) coordinates, where the y-axis (the direction in which the positive direction of the Y-axis is projected on the image plane 50 is positive) and the axis perpendicular to the y-axis is the z-axis (the direction in front of the paper is positive). , The ideal image height is (y,
z), the image height with distortion is (y + dy, z + dz). dy / r is the distortion rate in the y-axis direction, and dz / r is the distortion rate in the z-axis direction. r = √ (y ² + z ² ). Note that the image height with distortion used for obtaining the distortion rate is the center of gravity of the spot diagram at each image height.

FIG. 3 shows a spot diagram for an object point at each object height. The projected image on the screen 5 is as shown in FIG. Distortion object height dy / r dz / r (20,0) 0.0008 0.0000 (-20,0) 0.0046 0.0000 (20,20) 0.0162 -0.0224 (0,20) 0.0235 -0.0042 (-20,20) 0.0234 0.0101 From this distortion factor and FIG. 4, it is possible to obtain a final projection image in which trapezoidal distortion and distortion are sufficiently corrected by this projection optical device. I understand.

Next, the second embodiment of the present invention will be described with reference to FIGS.
An example apparatus will be described. FIG. 5 is a cross-sectional view of a lens group in the projection optical system of the projection optical apparatus according to this embodiment.
FIG. 6 is a diagram showing a schematic configuration of a projection optical device having the projection optical system and its optical path. FIG. 7 is a spot diagram showing a point at which a ray coming from an object point on the object plane cuts the image plane on the screen, and FIG. 8 is a projection distortion image (image shown by a solid line) on the screen and an ideal image without distortion (broken line). FIG.

This embodiment has an image display device 1 for providing an object plane 10 to be magnified and projected, as in the above-described embodiment, and further comprises a projection optical system P2 and a final image plane 90. And a screen 9 for The object plane 10 is a square object plane (lattice pattern) having a side of 40 mm. The projection optical system P <b> 2 includes a stop 20, lens groups 6 and 7 disposed adjacent to and before and after the stop 20, and a lens group 8 disposed between the lens group 7 and the screen 9.

For the lens group 6 on the object plane side, the stop 2
The 0 position is located at the focal position of the lens group, and the object plane side is a telesetrick system. The lens group 6 is a coaxial positive lens group including lenses 61, 62, and 63, the lens group 7 is a coaxial positive lens group including lenses 71, 72, 74, and 74, and the lens group 8 is Lens 8
This is a coaxial negative lens group consisting of 1, 82 and 83.

The functions of the positive lens group 6, the stop 20, and the positive lens group 7 are almost the same as those of the projection optical system P1 in the above-described embodiment, and the negative lens group 8 shortens the focal length of the entire projection optical system. By making the angle wider, the image on the object plane side is further enlarged and projected. The lens group 7 passes through the intersection of the plane including the stop 20 and the optical axis of the lens group 7 (the center of the stop because the stop is circular), and is rotationally eccentric about an axis parallel to the Z axis. In the lens group 8, the surface vertex position of the lens surface closest to the object plane in the lens group 8 (here, the lens surface r15 shown in FIG. 5) is shown in Table 2 as (X,
Y), and is eccentric of rotation about an axis parallel to the Z-axis about this surface vertex.

The magnification β ₁ of the lens unit 6 on the object side is | 1 /
β ₁ | = 0.01617 <0.05 is satisfied. Further, an angle θ ₁ formed between the symmetry axis of the lens group 8 and the image plane 90.
Satisfies the condition | θ ₁ | = 1.02 °. Lens groups 6, 7 and 8 as well as object plane 10 and image plane 90
Specifications are shown in Table 2 in the same manner as in Table 1 above.

In Table 2, "r1... R6, r7.
.. R20 ”are lenses 61 to 63, 71 to 74, lenses 81 to 83, as shown in FIG.
3 shows the lens surface. The stop 20 has an infinite radius of curvature (∞), which is also shown in Table 2 together with the stop radius (unit: mm). Also in Table 2, the numerical values of X, Y, and Z shown in the display columns of “lens groups 6, 7, 8”, “object plane”, and “image plane” are the same for the lens groups 6, 7, and 8 columns. The lens surface and the diaphragm closest to the object surface (r1 in the illustrated example)
, Stop 20, and (X, Y, Z) coordinate positions of the surface vertex and stop center of r15), and (X,
(Y, Z) coordinate positions. "ANG"
The rotation eccentric angle (unit degree) of the lens group 6, the aperture 20, and the lens group 8 with respect to the X axis is shown, and the object plane and the image plane are shown with respect to the X axis.

[0033]

[Table 2] The distortion at the final image plane 90 is as shown in the following table. The spot diagram for the object point at each object height is shown in FIG.
As shown in FIG. The projected image on the screen 9 is as shown in FIG. Distortion object height dy / r dz / r (20,0) -0.0164 0.0000 (-20,0) -0.0196 0.0000 (20,20) 0.0088 -0.0356 (0,0) 20) 0.0263 0.0022 (−20, 20) 0.0041 0.0305 From this distortion rate and FIG. 8, the projection optical apparatus can provide a final projection image in which trapezoidal distortion and distortion are sufficiently corrected. You can see that.

[0034]

As described above, according to the present invention, there is provided a projection optical apparatus for enlarging and projecting an image of an object plane provided by a film image, a video image or the like onto a screen, and having sufficient trapezoidal distortion and distortion. Thus, it is possible to provide a practical projection optical device which can obtain a projection image corrected in a small amount, can be provided at a low cost, and can be downsized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens group in a projection optical system of a projection optical apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a projection optical device having the projection optical system shown in FIG. 1 and its optical path.

FIG. 3 is a spot diagram showing a point where a light beam coming from an object point on an object plane cuts an image plane on a screen in the apparatus shown in FIG. 2;

FIG. 4 is a diagram showing a projection distortion image (image indicated by a solid line) of a quadrangular object plane (grating pattern) on a screen and an ideal image without distortion (image indicated by a broken line).

FIG. 5 is a sectional view of a lens group in a projection optical system of a projection optical apparatus according to another embodiment of the present invention.

6 is a diagram showing a schematic configuration of a projection optical device having the projection optical system shown in FIG. 5 and an optical path thereof.

FIG. 7 is a spot diagram showing a point where a light beam from an object point on an object plane cuts an image plane on a screen in the apparatus shown in FIG. 6;

FIG. 8 is a diagram showing a projection distortion image (image indicated by a solid line) of a quadrangular object plane (grating pattern) on a screen and an ideal image without distortion (image indicated by a broken line).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image display apparatus 10 Object plane P1 Projection optical system 2 Aperture 3, 4 f-theta characteristic lens group 31-33, 41-44 Lens r1-r20 Lens surface 5 Screen 50 Image plane P2 Projection optical system 20 Aperture 6, 7 Positive Lens group 61-63, 71-74 Lens 8 Negative lens group 81-83 Lens 9 Screen 90 Image plane

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 27/18

Claims (1)

(57) [Claims] 1. A projection optical apparatus for enlarging and projecting an image on an object plane onto a screen, comprising: a stop; a coaxial lens group on the object plane side adjacent to the stop; and a coaxial lens group on the screen side. The projection optical system does not form a real image up to the final image plane on the screen, and the magnification β ₁ of the lens group on the object plane side adjacent to the stop is | 1 / β ₁
| <0.05 is satisfied and the screen side
The coaxial lens group has a rotational deviation centered on the center of the diaphragm.
The projection optical device , wherein the two lens groups are decentered from each other by being centered.