JP2004045718A - Illumination optical system and magnified projection display device - Google Patents

Illumination optical system and magnified projection display device Download PDF

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JP2004045718A
JP2004045718A JP2002202622A JP2002202622A JP2004045718A JP 2004045718 A JP2004045718 A JP 2004045718A JP 2002202622 A JP2002202622 A JP 2002202622A JP 2002202622 A JP2002202622 A JP 2002202622A JP 2004045718 A JP2004045718 A JP 2004045718A
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optical system
surface
image forming
forming element
axis
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JP2002202622A
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JP3686887B2 (en
Inventor
Jun Ogawa
小川 潤
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Nec Viewtechnology Ltd
Necビューテクノロジー株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To improve the utilization rate of light by correcting keystone distortion and by making the shape of the irradiation region formed by an illumination optical system nearly the same as the shape of an image forming device. <P>SOLUTION: The magnified projection display device has the image forming device represented by a light valve, a DMD (Digital Micromirror Device), etc. The illumination optical system comprises: a light source; a condenser mirror which forms a virtual secondary light source by condensing the luminous flux from the light source; a luminance unevenness reducing element the incident end face of which is arranged at the position of a secondary light source, and which uniformizes the luminance distribution of the luminous flux from the secondary light source and emits the resultant luminous flux from an exit surface; and an afocal optical system which guides the emitted luminous flux from the luminance unevenness reducing element to the image forming element. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnifying projection type display apparatus for magnifying and projecting an image provided by an image forming element such as a liquid crystal light valve or a DMD (Digital Micromirror Device (registered trademark of Texas Instruments)) on a screen. And an illumination optical system used for an enlarged projection display device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various types of enlargement projection type display devices that enlarge and project an image provided by an image forming element such as a liquid crystal light valve or a DMD onto a screen have been proposed. In such an enlarged projection display device, in recent years, the amount of luminous flux reaching the screen is small, that is, the light use efficiency is required to be improved with the improvement in performance. In particular, there is an increasing need for an enlarged projection display device using a DMD as an image forming element.
[0003]
WO98 / 029773 discloses a compact and highly efficient illumination optical system using a reflective optical element as an illumination optical system for a magnified projection display device using a DMD as an image forming element. The illumination optical system described in this publication is configured such that a light beam emitted from an arc lamp of a white light source enters a DMD at a high angle via a condenser lens and a spherical mirror.
[0004]
[Problems to be solved by the invention]
However, in the illumination optical system described in the above publication, keystone distortion and the like are not corrected, and no means is used to make the shape of the irradiation area similar to the shape of an image forming element such as a DMD. For this reason, the lighting efficiency is poor.
[0005]
An object of the present invention is to achieve high efficiency of light utilization by correcting keystone distortion and making the shape of an irradiation area formed by an illumination optical system substantially the same as the shape of an image forming element. Further, in order to achieve further miniaturization, an illumination optical system for an image forming element such as a specular reflection type image forming element (eg, a regular reflection type liquid crystal light valve) or a transmission type image forming element (eg, a transmission type liquid crystal light valve). Another object of the present invention is to provide an illumination optical system and a projection display device in which the illumination light path is folded back by a reflection mirror or the like, and the utilization rate of light is high even when the image forming element is obliquely illuminated.
[0006]
[Means for Solving the Problems]
The present invention relates to an afocal optical system (an afocal system means that a parallel light beam passes through a lens system and then reappears) in an enlarged projection display apparatus having an image forming element represented by a liquid crystal light valve, a DMD, or the like. (An optical system that forms a parallel light beam) to improve the light use efficiency and achieve miniaturization.
[0007]
The illumination optical system according to the present invention includes a light source, a light-collecting mirror that collects a light beam from the light source to form a virtual secondary light source, and an incident end face disposed at a position of the secondary light source, and A luminance non-uniformity reducing element that makes the luminance distribution of the light beam uniform and emits light, such as a so-called light tunnel or a rod lens, and an optical element that makes the luminance non-uniformity at the light exit surface uniform by repeatedly reflecting the light beam on the inner surface; An illumination optical system characterized by having an emission surface of the unevenness reduction element as an object surface and an afocal optical system for guiding a light beam from the object surface to an irradiation surface, a so-called image surface. At the time of incorporation, any light beam passing through the center of the light beam from an arbitrary point on the object surface in the afocal optical system has an angle of 5 ° or more with the normal to the image surface when emitted from the image surface. To become It is desirable.
[0008]
An afocal optical system provided between an image forming element and a luminance unevenness reducing element typified by a light tunnel or a rod lens emits light from the image forming element 6 as shown in FIGS. The principal ray 8 (“principal ray”) of an arbitrary light beam (emission light beam 8 b) heading toward a projection optical system (not shown) defined as a light beam from an arbitrary object point passing through the center of the light beam, The “optical axis ray” is defined as a ray passing through the center of a light beam passing through the origin of the virtual object plane and the origin of the irradiation plane.) And the normal θ of the image forming element 6 is not less than 5 °. is there. Here, FIGS. 1A to 1C ((a) is a top view, (b) is a front view, and (c) is a side view) show a case where the image forming element 6 is a DMD. The angle θ described above is an angle when projected on a cross section in the plane of the paper as shown in the side view of FIG. 2 (a) and 2 (b) ((a) is a front view and (b) is a side view) show a case where the image forming element 6 is a regular reflection type, in which the principal ray 8 and the normal 10 of the emitted light beam 8b are shown. Is the angle shown in the side view of FIG. 2B, that is, the so-called reflection angle. 3 (a) and 3 (b) ((a) is a front view, (b) is a side view) shows a case where the image forming element 6 is of a transmissive type, in which a principal ray 8 and a normal 10 of an emitted light beam 8b are formed. The angle θ is the angle shown in the side view of FIG. In the figure, reference numeral 8a denotes an incident light beam incident on the image forming element.
[0009]
A second feature of the illumination optical system of the present invention is that each element constituting the afocal optical system is arranged in a three-dimensional space. FIG. 4 shows an example in which a DMD is used as an image forming element. FIG. 4 is a side view in which the illumination optical system of the present invention is applied to an illumination optical system of a magnified projection display device using a DMD as the image forming element 6.
[0010]
In FIG. 4, the light tunnel 3 is used as the luminance unevenness reducing element. The light tunnel 3 is arranged such that the incident end face 3a is located at a position of a virtual secondary light source formed by condensing a light beam from the light source 1 by the condensing mirror 2. The afocal optical system arranged on the exit surface 3b side of the light tunnel 3 includes three lenses 4a, 4b, 4c and a reflection mirror 5. The reflection mirror 5 provided between the second lens 4b and the third lens 4c (the first, second, and third lenses in order from the one closest to the light source) is a plane mirror, and only changes the optical path. It is not necessary because it is not an essential element of the focal optical system. It may be provided as needed, for example, when the optical path is folded to reduce the size of the device.
[0011]
In the three lenses 4a, 4b, and 4c constituting the afocal optical system, the first lens 4a is shifted vertically from an optical axis O connecting the light source 1 and the center of the light tunnel 3 which is a luminance unevenness reducing element. I have. That is, the center of the first lens 4a is not on the optical axis O. The second lens 4b shifts up, down, left, and right from the optical axis O, and is further decentered in rotation. The optical axis of the second lens 4b is not parallel to the optical axis O. The third lens 4 c is parallel to the optical axis of the projection lens and is shifted and decentered from the normal to the center of the image forming element 6. When the reflection mirror 5 is not provided, each optical element is disposed obliquely downward from the image forming element 6 while securing the relative positions of the optical elements as viewed from the image forming element 6.
[0012]
In the illumination optical system of the present invention, the afocal optical system may be composed of at least two refractive optical elements (a first lens 4a and a second lens 4b) as shown in FIG. This is the same as in the case of FIG. 4). Further, at least one of the optical elements constituting the afocal optical system may be constituted by a reflective optical element having a curved surface. For example, the reflection mirror 5 in FIGS. 4 and 5 may be configured as a concave mirror. Further, at least one of the optical elements constituting the afocal optical system may be constituted by an aspherical optical element.
[0013]
When at least one of the optical elements constituting the afocal optical system is formed of a plastic optical element, the illumination optical system can be formed easily and inexpensively.
[0014]
As shown in FIGS. 4 and 5, the enlarged projection display apparatus using the above-mentioned illumination optical system is arranged on the above-mentioned illumination optical system and the irradiation surface (image plane) of the afocal optical system constituting the illumination optical system. And a projection optical system disposed on the emission side of the image forming element 6 and projecting light emitted from the image forming element 6 onto a screen. The projection optical system can be composed of a projection lens 7 which is a refraction type imaging optical system, a reflection type imaging optical system including one or a plurality of reflection mirrors, and the like.
[0015]
An enlarged projection display apparatus using a refraction imaging optical system as a projection optical system includes an illumination optical system having a light source and an afocal optical system, and an image forming apparatus arranged on an illumination surface (image surface) of the illumination optical system. Element, and at least a telecentric refraction imaging optical system for refracting and projecting a light beam emitted from the image forming element onto a screen, wherein the stop of the refraction imaging optical system is a refraction imaging optical system. Is disposed at a position decentered from the optical axis.
[0016]
When the stop of the refraction-type imaging optical system is decentered, the upper and lower rays of light emitted from a specific light spot on the image forming element have their emission directions asymmetric with respect to the projection optical axis, and the emitted light is It is tilted with respect to the projection optical axis. As a result, light rays emitted from each point on the image forming element become parallel, and projection light having no unevenness in brightness can be obtained. Thereby, the illuminance non-uniformity of the projected image is reduced, and the projected image has high luminance.
[0017]
An enlarged projection display apparatus using a reflection type imaging optical system as a projection optical system includes an illumination optical system having a light source and an afocal optical system, and an image forming apparatus arranged on an illumination surface (image surface) of the illumination optical system. Element, and at least a telecentric reflection-type imaging optical system that reflects and projects a light beam emitted from the image-forming element onto a screen, wherein the reflection-type imaging optical system directs a reflection surface to the image-forming element. A first reflecting mirror having a rotationally symmetric aspherical concave reflecting surface, and a second reflecting mirror having a rotationally symmetrical aspherical convex reflecting surface directed at a light beam from the first reflecting mirror. A reflecting mirror, a third reflecting mirror having a concave reflecting surface having a rotationally symmetric aspherical shape or a convex reflecting surface having a rotationally symmetrical aspherical shape with a reflecting surface facing a light beam from the second reflecting mirror; Reflection surface on the light beam from the third reflector It is characterized in that it is composed of a fourth reflecting mirror having a convex reflecting surface of rotationally symmetric aspheric shape directed.
[0018]
More specifically, the reflecting surface shape of the reflecting mirror is such that the optical axis of the reflecting mirror is the z-axis, the plane perpendicular to the z-axis is the xy plane, the intersection point between the z-axis and the xy plane is the origin O, the origin is When coordinate axes are set with the axes intersecting at O and the axes orthogonal to each other on the xy plane as the x axis and the y axis, a rotationally symmetric aspheric surface represented by the following equations (1) to (3) is obtained. .
[0019]
ρ2= X2+ Y2(2)
c = 1 / r (3)
Where αi(I = 1, 2,..., 8) is a correction coefficient, k is a cone coefficient, and r is a radius of curvature of the reflection surface.
[0020]
In the above-mentioned enlarged projection display device, if the illumination optical system is provided with an optical path conversion element represented by a reflecting mirror, a prism or the like, there is an advantage that the depth of the enlarged projection display device can be reduced.
[0021]
(Action / Principle)
Generally, as shown in FIGS. 1, 2 and 3, when the principal ray 8 has an angle θ, the principal ray 8 of the light beam 8a incident on the image forming element 6 also has a predetermined angle. In particular, when a DMD is used for the image forming element 6, as shown in FIG. 1, the principal ray 8 of the incident light beam 8a is greatly inclined at a predetermined angle in two directions.
[0022]
FIG. 7 is a schematic diagram showing a state in which an emission surface image of the luminance unevenness reducing element is guided to the image forming element surface from an oblique direction using a normal imaging optical system (lens system 40). FIG. 8 is a diagram showing the irradiation state on the irradiation surface in FIG. 7, that is, the illuminance distribution. A contour-like curve drawn around the image forming element 6 is an iso-illuminance curve. As shown in FIG. 7, when the chief ray 8 is incident on the image forming element 6 from a greatly inclined direction, the exit face 3b of the emission non-uniformity reducing element has the same exit point 3b at the intersection of the optical axis of the optical system and the ray. Even at the upper points A and B, the distances A 'and B' between the optical axis and the intersections on the irradiation surface are greatly different on the irradiation surface. The difference in magnification generated in this manner is an aberration called keystone distortion. When this aberration occurs, the irradiation area 60 and the image forming element 6 do not have a similar shape, and the irradiation area (the area surrounded by the equal illuminance curve in FIG. 8) 60 is distorted as shown in FIG. descend. Therefore, the present invention corrects this keystone distortion using an afocal optical system as the illumination optical system, and improves the light use efficiency.
[0023]
The reason why the afocal optical system can correct the keystone distortion will be described with reference to FIG.
[0024]
FIG. 9 is a schematic diagram showing the basic concept of keystone distortion correction. In the optical system of FIG. 9, between the illumination optical system described in FIG. 7 (the light source and the luminance unevenness reducing element are not shown; only the emission surface 3b of the luminance unevenness reducing element and the lens system 40 are drawn) and the irradiation area 60 , An optical system (refractive optical element) 41 having a new positive power is newly disposed. At this time, if the optical system 41 having positive power is arranged so that the angle between the principal ray 8 and the irradiation area 60 is constant, the above-mentioned distances A ′ and B ′ can be made substantially equal. .
[0025]
As described above, by disposing the optical system 41 having a positive power, the keystone distortion can be effectively corrected. The illumination optical system in which the optical system 41 having the positive power is disposed has an angle between the principal ray 8 incident on the image forming element 6 disposed in the irradiation area 60 and the normal line of the image forming element 6 as described above. It will be constant. Therefore, light rays incident from the same direction over the entire surface of the image forming element 6 can be emitted in the direction of the projection optical system (not shown), and the light can be efficiently emitted by the projection optical system that receives light rays only from a specific direction. Can be led to a projection screen, a so-called screen (not shown). Further, by using a reflection type optical element as an optical system having a plane and positive power, the space occupied by the entire optical system can be reduced. However, simply arranging a reflection type optical element instead of a refraction type optical element requires a contrivance because a new distortion is generated as shown in FIG.
[0026]
As shown in FIG. 10, when an optical system having a positive power is constituted by the reflective optical element 42, interference between a light ray incident on the reflective optical element 42 and a light ray emitted from the image forming element 6 does not occur. , The reflection type optical element 42 must be disposed. This means that the reflection type optical element 42 is arranged to be inclined with respect to the optical axis. Therefore, the principal rays corresponding to the two points A and B equidistant from the optical system optical axis on the exit surface 3b enter the reflective optical element 42 at different incident heights. Therefore, the distances A 'and B' from the intersection of the irradiation area 60 and the optical axis of the optical system to the two points A and B on the emission surface 3b and the two points on the irradiation area 60 passing through the optical system differ. This is a new distortion.
[0027]
The distortion caused by tilting the optical system having a positive power is corrected by using the following two components alone or in combination. The first configuration is a method in which the lens system 40 of the illumination optical system is composed of a plurality of lens groups that are rotationally eccentric with each other, as shown in FIG. This lens group may be rotationally eccentric with one piece. Distortion can be corrected by eccentrically rotating some lens groups so that the height of the chief ray incident on the optical system 41 having positive power is aligned.
[0028]
The second configuration is a configuration in which the exit surface 3b is inclined in the same direction as the optical system having a positive power with respect to the optical axis of the lens system 40. With this configuration, the height of incidence on an optical system having a positive power can be corrected, and distortion is corrected. Further, as shown in FIG. 11, when the configuration in which the principal ray is incident on the lens system from the exit surface 3b substantially in parallel is adopted, the configuration of the illumination optical system can be simplified, the focus is further improved, and the irradiation area 60 is improved. The distinction from the other areas is clear (see the configurations in FIGS. 4 and 5).
[0029]
From the above description, the illumination optical system of the present invention can provide an illumination area substantially similar to the shape of the image forming element. However, when a DMD or a regular reflection type image forming element is used, the illumination Since the optical paths of the light and the emitted light overlap each other, it is apparent that the projection optical system and the optical elements that constitute the illumination optical system placed on the optical path interfere with each other. For this reason, the principal ray of the light emitted from the image forming element has a predetermined angle θ (the angle formed with the normal to the image forming element), and the projection optical system is constituted by an angled telecentric optical system, so that no light quantity loss is caused. It is desirable to do so. In the present invention, the angle θ is set to θ ≧ 5 ° to prevent interference.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
One embodiment of the illumination optical system of the present invention is shown in FIG. FIG. 4 is a side view in which the image forming element 6 is a DMD and the illumination optical system of the present invention is applied to the illumination optical system of the enlarged projection display device. As shown in FIG. 4, the enlarged projection display device includes an illumination optical system that illuminates the image forming element 6, an image forming element 6, and a projection lens (not shown) that projects a light beam from the image forming element 6 onto a screen (not shown). (Projection optical system) 7.
[0031]
The illumination optical system is arranged such that a light source 1, a condensing mirror 2 for condensing a light beam from the light source 1 to form a virtual secondary light source, and an incident end face 3 a at a position of the secondary light source. A light tunnel 3 (brightness unevenness reducing element) that emits light from the emission surface 3b by uniformizing the brightness distribution of the light flux from the secondary light source, and an afocal that guides the light flux emitted from the light tunnel 3 to the DMD that is the image forming element 6 It consists of an optical system.
[0032]
The light tunnel 3 used was a hollow quadrangular prism so that the illumination area was square because the shape of the image forming element was square. The inner wall of the light tunnel 3 is a reflection surface, and the light beam incident on the light tunnel 3 is repeatedly reflected and travels inside several times, thereby reducing the brightness unevenness at the light tunnel exit end. The same effect as in the light tunnel can be obtained by using a prismatic, cylindrical, or rod-shaped lens, a so-called rod lens, instead of the light tunnel 3. Note that the contour shape of the light tunnel and the rod lens may be adjusted to the shape of the image forming element.
[0033]
The afocal optical system includes first to third lenses 4a to 4c and a reflection mirror 5, and the exit surface 3b of the light tunnel 3 is an object surface. The reflection mirror 5 is a plane mirror, has only a function of changing the optical path, and is not essential because it is not an essential element of the afocal optical system. In the present embodiment, it is provided between the second lens 4b and the third lens 4c for the purpose of turning the optical path back to make the device smaller. A DMD is arranged as an image forming element 6 on an irradiation surface (image surface) of the afocal optical system.
[0034]
Of the three lenses constituting the afocal optical system, the first lens 4a is a plano-convex lens, and the plane side faces the light tunnel 3, so that the first lens 4a extends from the optical axis O connecting the light source 1 and the center of the light tunnel 3. The center of the first lens 4a is displaced from the optical axis O by shifting vertically. The second lens 4b is also a plano-convex lens, which is shifted vertically and horizontally from the optical axis O and is arranged so as to be rotationally eccentric. The third lens 4c uses a convex lens, is shifted from the normal line of the center point of the DMD, and is installed so as to be decentered, and irradiates the DMD with a light beam from the reflection mirror 5. The DMD is arranged at the position of the irradiation surface of the afocal optical system. Since the DMD of the image forming element 6 and the projection lens 7 of the projection optical system are known, their description is omitted.
[0035]
According to the configuration shown in FIG. 4, the light beam emitted from the light source 1 is reflected by the condenser mirror 2 to create a virtual secondary light source. The light beam emitted from the virtual secondary light source enters the light tunnel 3 in which the incident end face 3a is arranged at the position of the virtual secondary light source. The light beam incident on the light tunnel 3 is repeatedly reflected a plurality of times inside the light tunnel 3, exits from the light tunnel 3, and enters an afocal optical system having first to third lenses 4 a to 4 c. The principal rays of the light beam emitted after passing through the afocal optical system become parallel and reach the irradiation surface of the afocal optical system, that is, the DMD of the image forming element 6. The light beam incident on the DMD is reflected by the DMD and is projected on a screen (not shown) through the projection lens 7. At this time, the angle between the principal ray of the light beam from the DMD toward the projection lens 7 and the normal to the irradiation surface is set to 7.78 °.
[0036]
Table 1 and FIGS. 6A to 6C show the specific configuration of each optical element of the illumination optical system shown in FIG. 4 including the DMD. Here, Table 1 shows specific positions and directions of the respective optical elements by numerical values. 6 (a) to 6 (c) are diagrams schematically showing the arrangement of each optical element. FIG. 6 (a) is a top view, FIG. 6 (b) is a side view, and FIG. 6 (c) is a front view. Is shown.
[0037]
[Table 1]
[0038]
The “outgoing surface” of surface number 1 in the surface attribute column of Table 1 refers to the light exit surface (the outgoing surface 3b in FIGS. 4 and 6) of the luminance unevenness reducing element (the light tunnel 3 in this embodiment). The center point of the light exit surface 3b of the light tunnel 3 is set as the original initial origin, the axis passing through the origin and perpendicular to the light exit surface 3b is the z-axis, and the direction from the light source 1 toward the light tunnel 3 is "+" of the z-axis. The direction perpendicular to the xy plane and the z-axis, and the axes orthogonal to each other, are respectively the x-axis and the y-axis (in FIG. 4, the axis perpendicular to the paper surface is the x-axis, and the axis on the paper surface is the y-axis. The initial coordinate system (see FIG. 6) is used as the initial coordinate system (see FIG. 6), and the next origin, that is, the center coordinate position of the surface of the optical element, is represented by “coordinate conversion” in the order of the surface numbers. The coordinate system is a right-handed coordinate system, and the signs of “+” and “−” in the shift amount and the rotation amount in the table follow the display of FIGS. 6A to 6C.
[0039]
In the table, the surface numbers "2" to "4" are the first lens 4a, the surface numbers "5" to "10" are the second lens 4b, and the surface numbers "11" to "17" are the reflection mirror 5 and the surface. Numbers "18" to "26" indicate the third lens 4c, and surface numbers "27" to "34" indicate the arrangement position, direction, and shape of the DMD, respectively. The “plane” of the surface numbers “32” and “33” means a cover glass provided on the DMD surface.
[0040]
The “inter-plane distance” indicates the distance (unit: mm) in the z-axis direction from the plane of the plane number to the next plane. In other words, it is the distance that the coordinate system has been translated (or translated) in the z-axis direction from the plane of the plane number to the next plane. For example, the inter-plane distance of the plane number “1” is the parallel movement distance along the z-axis from the plane of the plane number (the exit plane 3b) to the plane of the plane number “3”, and the inter-plane distance of the plane number “3”. Is the translation distance along the z-axis from the plane of the surface number "3" to the spherical surface of the surface number "4", and the distance between the surfaces of the surface number "4" is from the spherical surface of the surface number "4" to the surface number "9". Represents the parallel movement distance along the z-axis up to the plane. The same applies to the following inter-plane distances.
[0041]
The “x-axis direction” and “y-axis direction” in the column of the shift amount indicate the coordinates origin of the surface of the optical element in the x-axis direction and the y-axis direction from the position of the origin determined by the surface number in front of the surface. The shift amount (the unit is mm) is shown. For example, in the example of the first lens 4a, the distance between the exit surfaces at the surface number "1" is 5.3 mm, the shift amount of the coordinate conversion at the surface number "2" is -2.18 mm in the x-axis direction, Since it is 0.86 mm in the y-axis direction, the center of the light exit surface 3b of the light tunnel 3 is the coordinate origin, the axis perpendicular to the light exit surface 3b is the z axis, the light exit surface 3b is the xy plane, and the horizontal direction is the x axis. In a coordinate system where the vertical direction is the y-axis, the light beam of the first lens 4a is 5.3 mm in the z-axis direction, -2.18 mm in the x-axis direction, and 0.86 mm in the y-axis direction from the emission surface 3b. This indicates that there is an input plane, that is, the center of the plane with the plane number “3”. Also, since the surface attribute of the surface number “3” is a plane, the distance between the planes is 10 mm, the surface attribute of the surface number 4 is a spherical surface, and the radius of curvature of the spherical surface is −12 mm, the first lens is a plano-convex lens. The surface on the light incident side, that is, the surface facing the light tunnel 3 is a flat surface (the surface with the smaller surface number is the light incident side), the light emitting side is a convex surface, and the flat surface (surface number “3”) and a spherical surface (surface). The number “4”) indicates that the distance between the centers is 10 mm.
[0042]
The radius of curvature is represented by "-" because the attribute of the surface is coordinate transformation and there is no definition of the radius of curvature itself. It is correct that all virtual surfaces are represented by “−”.
[0043]
“Center of x-axis”, “center of y-axis”, and “center of z-axis” in the rotation amount column respectively mean a rotation axis when the optical element is rotated. For example, in the case of the surface number “1”, the center of the x-axis and the center of the y-axis are 0 and the center of the z-axis is 21.4 °. ) Shows that it is rotated 21.4 ° counterclockwise.
[0044]
Coordinate conversion is performed in ascending order of plane number, (1) parallel movement on the z-axis (movement of distance between planes), (2) parallel movement on the x-axis (x shift amount), (3) parallel movement on the y-axis (y shift). (Amount) (4) rotation about the z-axis, (5) rotation about the y-axis, and (6) rotation about the x-axis.
[0045]
According to this coordinate conversion, in the example of the second lens 4b (surface numbers “5” to “10”), the inter-surface distance on the spherical surface (the light emitting surface of the first lens 4a) of the surface number “4” is 18 mm. The shift amount in the coordinate conversion of the surface number “5” is 1.3 mm in the x-axis direction, −0.6 mm in the y-axis direction, the shift amount of the surface number “6” is 0.5 mm in the x-axis direction, and the y-axis direction. Is -1 mm, the center (coordinate origin) of the plane (the light ray input surface of the second lens 4b) at the surface number "9" is the coordinate system of the spherical surface (surface number "4") (surface numbers "1" to "4"). The coordinate system after the coordinate transformation in 3 ". The coordinate origin is located at the center of the spherical surface, and the z-axis is perpendicular to the spherical surface. It is moved 18 mm on the z-axis from the origin (spherical surface (surface number" 4 ")). From the point moved by 1.3 mm in the x-axis direction and -0.6 mm in the y-axis direction (surface number "5"), the x-axis direction 0.5 mm, -1 mm movement in the y-axis direction (surface number "6") were in position. In addition, since the rotation amount in the coordinate conversion of the surface numbers “7” and “8” is −5.2 ° around the y-axis and 11.7 ° around the x-axis, the coordinates of the spherical surface (surface number “4”) The coordinate system formed by translating the origin to the position of the coordinate origin of the plane (surface number "9") is rotated by -5.2 [deg.] With the y axis as the center axis of rotation (surface number "7"). Further, the coordinate system rotated by 11.7 ° (surface number “8”) with the x axis as the center axis of rotation becomes the coordinate system of the plane (surface number “9”). The xy plane of this coordinate system is the plane of the plane number “9”, and the center position and the inclination of the plane (plane number “9”) with respect to the initial coordinate system are determined. The center (not the center of curvature) of the spherical surface (light exit surface) of the surface number “10” has a plane-to-plane distance of 10 mm on the plane (surface number “9”), so the coordinate system of the plane (surface number “9”) At 10 mm from the coordinate origin (the center of the plane (surface number “9”)) in the z-axis direction. The z-axis of the plane (surface number “9”) is the optical axis of the second lens 4b.
[0046]
The coordinate system of the plane (surface number "10") is translated by 10 mm along the z-axis, and the coordinate origin is shifted to the center of the spherical surface (surface number "10"). (Coordinate system) is a starting coordinate system for performing coordinate transformation to determine the position and orientation of the next optical element, in this embodiment, the reflection mirror 5, that is, the coordinate system of the reflection mirror 5.
[0047]
In the example of the reflection mirror 5 (surface numbers “11” to “17”), the distance between the surfaces on the spherical surface having the surface number “10” (the light emitting surface of the second lens 4b) is 0 mm, and the coordinates of the surface number “11”. The rotation amount in the transformation is -11.7 ° around the x-axis, the rotation amount in the coordinate transformation of the plane number “12” is 5.2 ° around the y-axis center, and the shift amount in the coordinate transformation of the plane number “13” is the x-axis. Since the direction is -0.5 mm and the y-axis direction is 1 mm, the coordinate origin is not moved in the z-axis direction. First, in the spherical (surface number "10") coordinate system, the x-axis is the center of rotation. It rotates -11.7 ° as the axis (surface number “11”), and rotates 5.2 ° around the y-axis as the center axis of rotation (surface number “12”). Each coordinate axis of the coordinate system obtained by the coordinate transformation of this rotation operation becomes a coordinate system parallel to the corresponding coordinate axis of the initial coordinate system. Thereafter, in this coordinate system (a coordinate system obtained by performing coordinate conversion by rotating the surface numbers “11” and “12”), the coordinate origin (the spherical surface (located at the center of the surface number “10”) is set to −0 in the x-axis direction. A coordinate system formed by performing a parallel movement of 0.5 mm and 1 mm in the y-axis direction (surface number “13”) is defined as a coordinate system of a virtual surface (surface number “17”), and the xy plane of this coordinate system is defined as a virtual surface ( The coordinate origin is set to the center of the virtual surface (surface number “17”).
[0048]
The distance between the surfaces in the virtual surface (surface number “17”) is 40 mm, the rotation amount in the coordinate conversion of the surface number “15” is −34 ° around the y-axis, and the rotation amount in the coordinate conversion of the surface number “16” is the x-axis. Since the center is 15 °, in the coordinate system of the virtual plane, after moving the coordinate origin by 40 mm on the z-axis and translating the coordinate system, the coordinate axis is −34 ° with the y-axis as the rotation center axis, and the x-axis is The coordinate system obtained by sequentially rotating the rotation mirror by 15 ° becomes the coordinate system of the reflection mirror 5. The xy plane of this coordinate system is the reflection surface of the reflection mirror 5, the coordinate origin is the center of the reflection mirror 5, and the position and orientation of the reflection mirror 5 are determined.
[0049]
In the above, the coordinate conversion in Table 1 has been described using the second lens 4b and the reflection mirror 5 as an example. However, the coordinates of other optical elements may be converted in the same manner as described above according to the notation in Table 1.
[0050]
Illumination states on the image forming element obtained in the present embodiment are shown in FIGS. 12 and 13A (the same figure as FIG. 12). FIG. 13B shows the illuminance distribution on the image forming element. As shown in FIG. 12, the image forming element size and the irradiation area 60 could be made substantially the same, and a uniform illuminance distribution without distortion was obtained. Note that the curves around the image forming element in FIG. 12 and FIG.
[0051]
FIG. 13B is a diagram showing the illuminance distribution on AA and BB shown in FIG. 13A on the image forming element. In the figure, the vertical axis indicates the illuminance, the horizontal axis indicates the position on the image forming element, the curve 13a indicates the illuminance distribution on AA, and the curve 13b indicates the illuminance distribution on BB. FIG. 13B shows that the image forming element is illuminated with uniform illuminance.
[0052]
(Second embodiment)
FIG. 5 shows a second embodiment of the illumination optical system of the present invention. FIG. 5 is a side view in which the image forming element 6 is a DMD and the illumination optical system of the present invention is applied to the illumination optical system of the enlarged projection display device. As shown in FIG. 5, the enlarged projection display device includes an illumination optical system that illuminates the image forming element 6, an image forming element 6, and a projection lens 7 that projects a light beam from the image forming element 6 onto a screen (not shown). And a projection optical system of a so-called refraction image forming optical system. The illumination optical system includes a light source 1, a condenser mirror 2 for condensing a light beam from the light source 1 to form a virtual secondary light source, and an incident surface 3a at a position of the virtual secondary light source. And a light tunnel 3 (brightness unevenness reducing element) that makes the luminance distribution of the light flux from the virtual secondary light source uniform and emits the light from the emission surface 3b, and outputs the light flux from the light tunnel 3 using the image forming element 6. And an afocal optical system for guiding to a certain DMD.
[0053]
As shown in FIG. 5, the afocal optical system used for the illumination optical system includes two refractive optical elements, a first lens 4a and a second lens 4b, and a reflection mirror 5. As in the case of the first embodiment, the reflection mirror 5 is a plane mirror, has only a function of changing the optical path, and is not essential because it is not an essential element of the afocal optical system. In the present embodiment, the optical path is provided between the first lens 4a and the fifth lens 4b for the purpose of folding the optical path to reduce the size of the apparatus. A DMD is arranged as an image forming element 6 on the irradiation surface of the afocal optical system. In this embodiment, θ is 7.8 °, and the illumination state on the image forming element can be substantially the same as the irradiation area with the image forming element size ゛ as shown in FIG. The illuminance distribution was obtained. Note that the curve around the image forming element in FIG. 14 indicates an equal illuminance curve.
[0054]
Table 2 shows a specific configuration of each optical element of the illumination optical system shown in FIG. 5, including the DMD.
[0055]
[Table 2]
[0056]
The “outgoing surface” of surface number 1 in the surface attribute column of Table 2 is the light exit surface (outgoing surface 3b) of the luminance unevenness reducing element (light tunnel 3), as in the first embodiment. Further, setting the initial coordinate system with the center point of the light exit surface 3b of the light tunnel 3 as the original initial origin is the same as in the first embodiment.
[0057]
In the table, the surface numbers "2" to "4" are the first lens 4a, the surface numbers "5" to "8" are the reflection mirror 5, and the surface numbers "9" to "17" are the second lens 4b. The numbers “18” to “25” indicate the respective arrangement positions, orientations, and shapes of the DMD. The planes with surface numbers “23” and “24” mean the cover glass provided on the DMD surface.
[0058]
(Third embodiment)
FIG. 15 shows a third embodiment of an enlarged projection display device using the illumination optical system of the present invention. This embodiment is an example of a configuration in which one reflecting mirror having a positive power is used for an afocal optical system. As shown in FIG. 15, the enlarged projection display apparatus has an illumination optical system for illuminating the image forming element 6, an image forming element 6, and a projection lens for projecting a light beam from the image forming element 6 onto a screen (not shown). 7 The illumination optical system includes a light source 1, a condenser mirror 2 for condensing a light beam from the light source 1 to form a virtual secondary light source, and an incident surface 3a at a position of the virtual secondary light source. And a light tunnel 3 (brightness unevenness reducing element) that makes the luminance distribution of the light flux from the virtual secondary light source uniform and emits the light from the emission surface 3b, and outputs the light flux from the light tunnel 3 using the image forming element 6. And an afocal optical system for guiding to a certain DMD.
[0059]
As shown in FIG. 15, the afocal optical system used for the illumination optical system includes two refractive optical elements, a first lens 4a and a second lens 4b, a reflecting mirror 4d having a positive power, and an optical path bending optical system. Of the reflection mirror 5. The reflection mirror 5 used was a convex mirror. A DMD is arranged as an image forming element 6 on the irradiation surface of the afocal optical system. In this embodiment, θ is 7.8 °, and the illumination state on the image forming element can be substantially the same as the irradiation area on the image forming element size ゛ as shown in FIG. The illuminance distribution was obtained. Note that the curve around the image forming element in FIG. 16 shows an equal illuminance curve. Become.
[0060]
Table 3 shows a specific configuration of each optical element of the illumination optical system shown in FIG.
[0061]
[Table 3]
[0062]
The “outgoing surface” of the surface number 1 in the surface attribute column of Table 3 is the light exit surface (outgoing surface 3b) of the luminance unevenness reducing element (light tunnel 3), as in the first embodiment. Further, setting the initial coordinate system with the center point of the light exit surface 3b of the light tunnel 3 as the original initial origin is the same as in the first embodiment.
[0063]
In the table, the surface numbers "2" to "4" are the first lens 4a, the surface numbers "5" to "9" are the second lens 4b, and the surface numbers "10" to "15" are the reflection mirror 5 and the surface. Numbers "16" to "23" represent the reflective optical element 4d having a positive power, and surface numbers "24" to "31" represent the respective arrangement positions, directions, and shapes of the DMD. The planes of the surface numbers “29” and “30” mean cover glasses provided on the DMD surface.
[0064]
(Fourth embodiment)
This embodiment is an example of a magnified projection display device in which an illumination optical system includes an aspherical optical element. This enlarged projection display device is the same as the above three embodiments, and comprises an illumination optical system for illuminating the image forming element, an image forming element, and a projection lens for projecting a light beam from the image forming element onto a screen. is there. The enlarged projection display device of the present embodiment has a configuration in which the reflection mirror 5 is replaced with an aspherical reflection mirror in FIG. 15, and the other configuration is the same as that of the third embodiment. Table 4 shows the specific configuration of each optical element of the illumination optical system in this apparatus, including the DMD. The illumination state on the image forming element was as shown in FIG.
[0065]
[Table 4]
[0066]
Note that the cylinder of surface number 16 in Table 4 has a semi-cylindrical shape, and the surface of surface number 16 has a non-cross section cut by an arbitrary surface parallel to the yz plane (the coordinate system of the surface number 16). That is, the expression for the spherical surface is satisfied. The aspherical surface is a surface represented by a normal aspherical expression (Equations (1) to (3) described in the section of "Means for Solving the Problems").
[0067]
The way of reading the table is the same as in the above three embodiments. In the table, surface numbers "2" to "4" are the first lens 4a, surface numbers "5" to "9" are the second lens 4b, surface numbers "10" to "16" are aspherical reflecting mirrors, The surface numbers "16" to "25" represent the reflective optical element 4d having a positive power, and the surface numbers "26" to "33" represent the arrangement position, direction, and shape of the DMD, respectively. The planes of the surface numbers “31” and “32” mean the cover glass provided on the DMD surface.
[0068]
In this embodiment, the reflection mirror is an aspherical optical element. However, the present invention is not limited to the reflection mirror, and an aspheric lens may be used for the aspherical optical element.
[0069]
(Fifth embodiment)
The present embodiment is an example of an enlarged projection display device in which the projection optical system is modified to reduce unevenness in illuminance of a projected image.
[0070]
The enlarged projection display device is the same as the above-described embodiment in that it includes an illumination optical system that illuminates the image forming element, an image forming element, and a projection optical system that projects a light beam from the image forming element onto a screen. . An illumination optical system is arranged such that the incident end face is located at a position of a virtual secondary light source, and a light source and a condensing mirror that collects a light beam from the light source to form a virtual secondary light source. A light tunnel (brightness unevenness reducing element) that makes the luminance distribution of the light beam from the secondary light source uniform and exits from the exit surface, and an afocal optical system that guides the light beam emitted from the light tunnel to the DMD that is an image forming element. The configuration is the same as in the above four embodiments. In the present embodiment, the illumination optical system having the configuration shown in FIG. 4, that is, the same illumination optical system as that of the first embodiment is used.
[0071]
The projection optical system uses a telecentric refraction imaging optical system (projection lens), and the center of the diaphragm used in the refraction imaging optical system is set to the optical axis of the refraction imaging optical system (see FIG. 18). L1) is eccentric (the eccentric amount h in FIG. 18). FIG. 18 shows a specific example of the projection optical system.
[0072]
As shown in FIG. 18, the projection lens is composed of a total of 14 lenses including a first lens group G1 to a fourth lens group G4 in order from the screen side, and a parallel flat glass G5. A stop S is provided between the second lens group G2 and the third lens group G3. The center of this stop is decentered by h from the optical axis L1 of the projection lens. Table 5 shows data of each lens in the lens groups G1 to G4 constituting the projection lens.
[0073]
[Table 5]
[0074]
In the table, the surface number i is assigned in order from the refractive surface closest to the screen, and the refractive surface for the d-line (wavelength 587.6 nm) indicates the refractive index, and the refractive surface next to the number indicates the refractive index. One optical element is configured. The surface distance d (unit: mm) indicates the lens thickness or air space between the corresponding refraction surface and the next refraction surface. The surface distance of the final surface is the distance from the parallel flat glass to the image forming element.
[0075]
The first lens group G1 includes a total of three lenses: a convex meniscus lens G11 having a convex surface facing the screen, a concave meniscus lens G12 having a concave surface facing the image forming element, and a concave lens G13. The second lens group G2 includes a cemented lens of a convex meniscus lens G21 having a convex surface facing the image forming element side, a concave meniscus lens G22 having a concave surface facing the screen side, and a convex lens G23. The third lens group G3 includes a cemented lens of a concave lens G31 and a convex lens G32. The fourth lens group G4 includes a concave lens G41, a convex meniscus lens G42 having a convex surface facing the image forming element, a cemented lens of the concave lens G43 and the convex lens G44, and a convex meniscus lens G45 and a convex lens G46 having a convex surface facing the image forming element. It is configured. The cemented lens of the concave lens G43 and the convex lens G44 is arranged with its concave surface facing the screen.
[0076]
In the projection lens, at the time of focusing, the surface distance d6 in the surface number 6 changes, and the first lens group G1 advances and retreats along the optical axis L1 between the screen side and the image forming element side. The other lens groups G2 to G4 other than the first lens group G1 are fixed. At the time of zooming, the surface distances d11 and d15 in the surface numbers 11 and 15 change, and the second lens group G2, the stop S1, and the third lens group G3 move along the optical axis L1. The stop S is eccentric in a direction perpendicular to the optical axis L1, and the distance h from the center of the opening of the stop S to the optical axis L1 is shown as the amount of stop eccentricity. Table 6 shows the focal length, f-number, and variable surface interval of the entire system at the wide-angle end, standard, and telephoto end when the projection distance is set to infinity.
[0077]
[Table 6]
[0078]
The total length L of the lens system when the projection distance is infinity, the amount of stop eccentricity h1, the focal lengths f1 to f4 of the lens groups G1 to G4, and the combined focal length fw of the entire system at the wide-angle end are respectively
L = 139.5 mm
h = 4.5 mm
f1 = −34.97 mm
f2 = 37.24 mm
f3 = 125.91 mm
f4 = 49.03 mm
fw = 28.58 mm
It is.
[0079]
In the first to fifth embodiments, a projection lens (refractive image forming optical system) is used as a projection optical system. However, instead of this projection lens, a reflection image formed by one or a plurality of reflection mirrors is used. An optical system may constitute a projection optical system. In each of the above embodiments, the DMD is used as the image forming element 6. However, for example, an enlarged projection display using an image forming element other than the DMD, such as a reflective liquid crystal light valve or a transmissive liquid crystal light valve. Even when the apparatus is configured, the same effects as those of the above embodiment can be obtained.
[0080]
(Sixth embodiment)
FIG. 19 shows a sixth embodiment of an enlarged projection display apparatus using the illumination optical system of the present invention. This embodiment is an example in which a reflection type imaging optical system is used as a projection optical system.
[0081]
As shown in FIG. 19, the enlarged projection display device includes an image forming element 6, an illumination optical system 11 for illuminating the image forming element 6, and a projection for projecting a light beam emitted from the image forming element 6 onto a screen (not shown). And an optical system. The image forming element 6 and the illumination optical system 11 are the same as those in the first embodiment, and have the same arrangement.
[0082]
The projection optical system comprises a telecentric reflection type imaging optical system comprising four reflecting mirrors. The telecentric reflection type imaging optical system constituting the projection optical system has a first reflecting mirror 7a having a concave reflecting surface having a rotationally symmetric aspherical shape, and a reflecting surface directed to a light beam from the first reflecting mirror. A second reflecting mirror 7b having a rotationally symmetric aspherical convex reflecting surface, and a third reflecting surface having a rotationally symmetric aspherical concave reflecting surface whose reflecting surface is directed to a light beam from the second reflecting mirror. A mirror 7c, and a fourth reflecting mirror 7d having a rotationally symmetric aspherical convex reflecting surface whose reflecting surface is directed to the light beam from the third reflecting mirror, and includes four reflecting mirrors 7a and 7b. , 7c, 7d, the reflecting mirrors are arranged such that the optical paths of the light beams sequentially reflected are zigzag, and the light beams reflected by the fourth reflecting mirror 7d are enlarged and projected on a projection screen (not shown). It is a telecentric reflection type imaging optical system. A reflection type image forming element 6 composed of DMD is arranged on the image forming surface of the reflection type image forming optical system.
[0083]
As shown in FIG. 20, the reflecting surfaces of the reflecting mirrors 7a to 7d (rotationally symmetric aspherical surfaces) are formed such that the optical axis is a z-axis and a plane perpendicular to the z-axis is an xy plane (four vertices A, B, C, and D), the intersection of the z-axis and the xy plane is the origin O, and the axes that intersect at the origin O and are orthogonal to each other on the xy plane are x-axis and coordinate axes are set to the y-axis. The shape satisfies the following expressions (1) to (3).
[0084]
ρ2= X2+ Y2(2)
c = 1 / r (3)
Where αi(I = 1, 2,..., 8) is a correction coefficient, r is a radius of curvature of the reflection surface, and k is a cone coefficient.
[0085]
A reflecting mirror having a reflecting surface shape that satisfies the above equation may be a reflecting mirror having a curved surface α (curved by points a, b, c, and d in FIG. 20) passing through the center of the z axis, or z. A reflection mirror having a so-called offset-type curved surface β (a curved surface formed by points a ′, b ′, c ′, and d ′ in FIG. 20) whose axis does not pass through the center may be used. In the present embodiment, an offset type is adopted.
[0086]
The spatial positional relationship between the reflecting mirrors is arranged so that the origin of the coordinate system of each reflecting mirror that defines the reflecting surface shape is on the same plane, but is expressed by a simple relational expression unlike the reflecting surface shape It is difficult to determine the shape of the reflecting surface, and the above expressions (1) to (3), the incident angle of the chief ray to the image forming element 6, the opening angle of the light beam emitted from the image forming element 6, and the space of the optical system. Based on the design specifications such as the limitation of the target size, the type and size of the image forming element 6 (liquid crystal display element or DMD, etc.) combined with the reflection type imaging optical system, the screen projection position, etc., the reflection surface is determined by a known ray tracing simulation. The arrangement positions of the reflecting mirrors 7a to 7d are determined together with the shape. At this time, when the angle between the optical axis of the reflection type imaging optical system (A-A axis in FIG. 22, that is, the Z-axis) and the light reaching the screen (see FIG. 22), that is, the half angle of view is 40 ° or more and less than 90 °. In addition, the principal ray angle θ from the image forming element 6 to the reflection type imaging optical system (projection optical system) (the angle formed by the principal ray emitted from the image forming element 6 and the normal line of the image forming element (see FIG. 1) )) Is set to 5 ° or more. When the chief ray angle is 5 ° or less, the chief ray angle θ is set to 5 ° or less because the ray from the image forming element 6 to the reflection type imaging optical system interferes with the illumination optical system to cause vignetting of the ray. Is undesirable. There is no particular upper limit for the principal ray angle θ, but the upper limit is determined by the size of the enlarged projection display device incorporating the reflective imaging optical system. In order to keep the space between the reflecting mirrors in the vertical direction too small and to keep the size compact, it is preferable to keep the upper limit of the principal ray angle at about 20 °.
[0087]
As shown in FIG. 21, the procedure for obtaining the spatial positional relationship between the reflecting mirrors by the ray tracing simulation is as follows: first, the angle of view, the screen size, the spatial size of the optical system, the type and size of the image forming element, Design specifications such as a screen projection position are determined (step S1). Next, based on the design specifications, the design concept such as the type of the optical system (whether or not it is a telecentric system; the telecentric system is selected in the present invention), the number of reflecting mirrors (four in the present embodiment), the optical axis shift amount, and the like. Is determined (step S2). Based on the information of steps S1 and S2, the diaphragm position and the spatial arrangement of the reflecting mirrors (arranged so that the reflecting mirrors do not interfere with each other to block part of the reflected light beam), Initial data such as a mirror shape determining equation (the present invention uses the above equations (1) to (3)) and initial values of optical system elements necessary for ray tracing are created (step S3). A ray tracing simulation is performed based on the initial data, and the size, spatial position, tilt angle, and the like of each reflecting mirror are determined. In the ray tracing simulation, a known method was used. The inventor performed a ray tracing simulation using commercially available optical system design software. In the ray tracing simulation, first, by ray tracing, the range of x and y in equations (1) to (3), αi, R, and k, and the values of parameters that determine the size, spatial position, tilt angle, and the like of each reflecting mirror are calculated (step S4). Based on the result of step S4, performance evaluation such as MTF, tolerance, curvature, aberration, and effective luminous flux margin of the reflector is performed (step S5), and calculation and performance evaluation of parameters are repeated until the evaluation result satisfies the design specification. , Determine the shape and spatial position of the reflector.
[0088]
By optimizing the shape of each of the four reflecting surfaces based on the above procedure, a reflecting mirror shape suitable for widening the angle of view and miniaturizing the telecentric optical system is obtained. An example of the obtained result is shown in FIG.
[0089]
[Table 7]
[0090]
FIG. 22 is a schematic diagram showing the arrangement of the reflecting mirrors, and Table 7 is a table showing specific numerical values of each parameter indicating the reflecting mirrors and their arrangement.
[0091]
In FIG. 22, the coordinate system of the optical system including the image forming element 6 and the four reflecting mirrors 7a to 7d (coordinate axes are represented by capital letters) is such that the optical axis AA of the image forming element 6 is the Z axis and the Z axis. The axis perpendicular to the plane of intersection is the X axis, the axis perpendicular to the Z axis and parallel to the plane of the paper (the axis on the plane of the paper) is the Y axis, and the right direction in the figure is the positive direction of the Z axis, and the left direction is the Z axis. The negative direction, the upper part of the figure is set to the positive direction of the Y-axis, the lower part of the figure, the negative direction of the Y-axis is set below the Z-axis, and the direction from the surface to the back is set to the positive direction of the X-axis. Are in the YZ plane. Although the coordinate origin may be set anywhere, the intersection of the Z axis and the image forming element 6 is set as the coordinate origin for convenience.
[0092]
"No" in Table 7 indicates a number for identifying the reflecting mirrors 7a to 7d and the image forming element 6, "0" indicates the image forming element 6, "1" indicates the first reflecting mirror 7a, "2" indicates the second reflecting mirror 7b, "3" indicates the third reflecting mirror 7c, and "4" indicates the fourth reflecting mirror 7d. “Dj” represents the distance between the reflecting mirrors, and is a column of image forming elements, that is, No. Dj in the column of 0 indicates d0 shown in FIG. 22, and indicates the distance from the image forming element 6 to the first reflecting mirror 7a. Similarly, No. In column 1, that is, in the column of the first reflecting mirror, dj indicates d1 shown in FIG. 22, and indicates the distance from the first reflecting mirror 7a to the second reflecting mirror 7b. Hereinafter, the same applies. No. In column 4 (the column of the fourth reflecting mirror), dj, that is, d4 indicates the distance from the fourth reflecting mirror 7d to the screen 9.
[0093]
22, each parameter in Table 7, namely, the radius of curvature r of the reflecting mirrors 7a to 7d, the distance d0 between the image forming element 6 and the first reflecting mirror 7a, the distances d1 to d3 between the reflecting mirrors, and the fourth reflection From the distance d4 from the mirror 7d to the screen 9 and the Z-axis (optical axis AA of the image forming element), the coordinate origin of the reflecting mirrors 7a to 7d (the coordinate origin defining the reflecting mirror surface shape, ie, the reflecting mirror surface shape) is calculated. The unit of the distances X and Y to the origin (the origin of the coordinates in this case) is “mm”. The unit of the rotation angle a of the reflecting mirrors 7a to 7d is “degrees”, and the coordinate axes x, y, and z of the coordinate system (coordinate axes are represented by lowercase letters) defining the reflecting surface shape of the reflecting mirror are the coordinate axes X, Y of the optical system. , A clockwise (clockwise) rotation of the x-axis as a rotation axis with respect to a state parallel to Z (a state in which the y-axis is perpendicular to the Z-axis (optical axis A-A)) is “+” and a counterclockwise rotation (Counterclockwise) The rotation was marked "-". The other parameters (cone coefficient k, correction coefficients α1 to α7) are anonymous. The distance dj (j = 0 to 4, that is, d0, d1, d2, d3, d4 in the figure) is set between the origins of the coordinates defining each reflecting surface shape in parallel with the optical axis AA (Z axis). The measured distance, that is, the interval between the Z coordinates of the origin of each coordinate defining each reflecting surface shape, and X is the origin of the coordinates defining each reflecting surface shape from the optical axis AA (Z axis) to the X axis direction. Is the distance measured perpendicular to the optical axis AA (Z axis), and Y is the origin of the coordinates defining each reflecting mirror surface shape in the Y axis direction from the optical axis AA (Z axis) to the optical axis AA ( (Z axis). In the example of FIG. 22, since the reflecting mirror is of the offset type, the coordinate origin of the reflecting mirror is shifted from the center of the reflecting mirror, and the distance dj (j = 0 to 4) defines each reflecting mirror surface shape. Since the relative Z coordinate of the origin of each coordinate need only be known (the X coordinate and the Y coordinate are unnecessary), the figure shows the position of the Z coordinate of the coordinate origin of each coordinate defining each reflecting mirror surface shape, The positions of the X coordinate and the Y coordinate are not specified. Although the reflecting mirror 3d is rotated to the left, it is apparently rotated to the right due to the offset type reflecting mirror surface shape. The size of the reflecting mirror is arbitrary, and the size may be set so that light rays are not blocked in the above-described positional relationship of the reflecting mirror.
[0094]
In FIG. 19, a light beam emitted from a light source is incident on an image forming element 6 arranged on an irradiation surface of an illumination optical system 11 (which is also an imaging surface of a reflection type imaging optical system), and has a light intensity corresponding to an image. The light is spatially modulated into a distribution and reflected, and is incident on a reflection type imaging optical system. The light beam incident on the reflection type imaging optical system is sequentially reflected and enlarged by the first reflection mirror 7a, the second reflection mirror 7b, the third reflection mirror 7c, and the fourth reflection mirror 7d, and the fourth reflection is performed. The light beam reflected by the mirror is enlarged and projected on a projection screen (not shown). The projection angle of view of the projection image at this time was a wide angle of view of 140 ° or more.
[0095]
The reflection type imaging optical system is a telecentric optical system, and the principal ray has a predetermined angle θ with respect to the normal of the image forming element 6 as shown in FIG. When a light beam having an opening angle ψ of the light beam with respect to the main light beam 8 (usually corresponding to NA and FNO) enters the image forming element 6 and is reflected, the main light ray is normal to the normal line of the image forming element 6. Has an angle θ, the interference with the optical components of the illumination unit can be eliminated, and an optical system can be configured without causing vignetting or the like. Further, by using an afocal optical system for the illumination optical system, distortion on the irradiation surface is eliminated, and the illumination efficiency is improved. In addition, a display device such as a magnified projection display device can be constituted by the same reflective image forming optical system whether the image forming element is a transmission type or a reflection type.
[0096]
In the reflection-type imaging optical system, since the light beam has the principal ray angle θ, a fan-shaped distortion in which the lower side of the projection screen generally becomes narrower and the upper side expands, inevitably occurs. Moreover, it becomes more remarkable as the angle of view becomes wider. This embodiment improves the distortion with the configuration of four reflecting mirrors having a rotationally symmetric aspherical shape, and has a disadvantage of the telecentric optical system that each optical component is relatively large and expensive. By using reflectors, the processing accuracy of each reflector was eased, and even relatively large reflectors could be made of plastic, and the cost of the reflector was reduced by using resin. In addition, since the reflecting surface has a rotationally symmetric aspherical shape, the distance between the reflecting mirrors can be reduced to 150 mm or less, and the apparatus is compact.
[0097]
When applied to a magnified projection display device, it is necessary to consider the thermal effect from the light source. In particular, since the reflecting mirror 7b shown in FIG. 19 is disposed near the image forming element 6 and is easily affected by heat, the linear expansion coefficient .alpha.
α <6 × 10-5
It is desirable to suppress it.
[0098]
(Seventh embodiment)
FIG. 24 shows an example in which a rear projection type display device integrated with a screen using the illumination optical system of the present invention is configured. The rear projection display device of FIG. 24 includes a projection optical system including an illumination optical system 11, a transmission type image forming element 6a, a reflection type imaging optical system 70, plane reflection mirrors 12a and 12b, and a transmission type screen 9. It is composed of The illumination optical system 11, the transmission type image forming element 6a, and the first reflection mirror 7a of the reflection type imaging optical system 70 are on a straight line, and the imaging plane of the reflection type imaging optical system 70 (the image plane of the illumination optical system) The transmission type image forming element 6a is disposed at the same time. The illumination optical system 11 is the same illumination optical system as that of the first embodiment. Further, as the reflection type imaging optical system 70 constituting the projection optical system, the same telecentric reflection type imaging optical system as that of the sixth embodiment was used.
[0099]
A light beam emitted from a light source of the illumination optical system 11 enters a transmission type image forming element 6a represented by a transmission type liquid crystal light valve. The light beam transmitted through the transmission type image forming element 6a enters the projection optical system including the telecentric reflection type imaging optical system 70 while keeping the divergence angle with respect to the principal ray. The reflection type imaging optical system 70 is composed of four reflecting mirrors 7a to 7d having a rotationally symmetric aspherical shape shown in FIG. 19, and the luminous flux emitted from the reflection type imaging optical system 70 has uniform illuminance. Wide angle of view. The light beam emitted from the reflection type imaging optical system 70 is reflected by the plane reflection mirror 12a having the reflection surface arranged vertically so as to face the reflection mirror 3d on the emission side of the reflection type imaging optical system 70, and above the plane reflection mirror 12a. The light is sequentially reflected by the plane reflecting mirror 12b having the reflecting surface arranged horizontally with the reflecting surface facing downward (perpendicular to the plane reflecting mirror 12a), and is enlarged to the transmission screen 9 arranged in parallel to the plane reflecting mirror 12a. Is projected.
[0100]
As shown in FIG. 24, when the transmission type screen 9 and the plane reflection mirrors 12a and 12b are arranged with respect to the reflection type imaging optical system 70, it is possible to enlarge and project the image on the screen 9 in a small space. In particular, by arranging and configuring the plane reflecting mirror 12b in parallel to the normal line of the image forming element 6a, the entire apparatus can be made invisible from the field of view of the observer who observes the transmission screen 9. Further, as shown in FIG. 4, the illumination optical system 11 has a reflection mirror for turning back the optical path, and has an advantage that the depth of the display device can be reduced.
[0101]
The sixth and seventh embodiments are examples in which a rotationally symmetric aspherical concave mirror is used as the third reflecting mirror 7c of the reflective imaging optical system 70, but the third reflecting mirror 7c is rotationally symmetric. The same effect as in the case of a concave mirror having a rotationally symmetric aspherical shape can be obtained even with an aspherical convex mirror. In the sixth and seventh embodiments, a telecentric reflection imaging optical system is used as the projection optical system. However, instead of the telecentric reflection imaging optical system, a normal reflection optical system, for example, an extreme example. The optical path may be folded back by one or a plurality of reflecting mirrors.
[0102]
【The invention's effect】
According to the present invention, by including an afocal optical system in the illumination optical system, it is possible to suppress the occurrence of keystone distortion and distortion due to the use of a reflection optical element for turning back the optical path, and to substantially reduce the size of the image forming element and the irradiation area. Could be the same. In addition, a rectangular irradiation region having a high illuminance and a uniform illuminance distribution can be formed while maintaining the luminance distribution on the emission surface of the luminance nonuniformity reduction element, and the light use efficiency is improved. Further, the use of one reflection type optical element having both the function of folding the optical path and the function of forming the afarcal optical system as the optical element forming the afocal optical system has made it possible to reduce the size of the entire apparatus.
[0103]
The angle θ between the principal ray of the light beam emitted from the image forming element arranged on the irradiation surface (image plane) of the illumination optical system to the projection optical system and the normal to the image forming element (see FIGS. 1, 2, and 3) Was set to 5 ° or more, interference between the illumination optical system and the projection optical system could be eliminated.
[0104]
Since the projection optical system is composed of a telecentric reflection imaging optical system composed of a rotationally symmetric aspherical reflecting mirror, a wide angle of view can be realized, and the spacing between the reflecting mirrors can be reduced, thereby enabling miniaturization. . Further, since the reflection mirror constituting the reflection imaging optical system has a rotationally symmetric aspherical shape, it can be easily processed, can be made of resin, and can be realized at low cost. As a result, it has become possible to reduce the price of the enlarged projection display device. In addition, since a telecentric refraction-type imaging optical system in which the diaphragm is decentered from the optical axis is used for the projection optical system, uneven illuminance of the projection image can be reduced, and a high-brightness projection image can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a state of a light beam and a principal ray entering and exiting an image forming element including a DMD.
FIG. 2 is a diagram illustrating a state of a light beam and a principal ray entering and exiting a regular reflection image forming element.
FIG. 3 is a diagram illustrating a state of a light beam and a principal ray entering and exiting a transmission type image forming element.
FIG. 4 is a perspective view of the first embodiment.
FIG. 5 is a perspective view of a second embodiment.
FIG. 6 is a diagram schematically showing the relationship between the arrangement of optical elements and coordinate axes.
FIG. 7 is a schematic view showing a state in which an image forming element is irradiated from an oblique direction by a conventional illumination optical system.
FIG. 8 is a diagram showing an illumination state on an image forming element by a conventional illumination optical system.
FIG. 9 is a schematic diagram showing a basic concept of keystone distortion correction.
FIG. 10 is a diagram showing how distortion occurs when a reflective optical element having positive power is used.
FIG. 11 is a schematic diagram showing a basic concept of distortion correction.
FIG. 12 is a diagram illustrating an illumination state on an image forming element according to the first embodiment.
FIG. 13 is a diagram illustrating an illuminance distribution on an image forming element according to the first embodiment.
FIG. 14 is a diagram illustrating an illumination state on an image forming element according to the second embodiment.
FIG. 15 is a perspective view of a third embodiment.
FIG. 16 is a diagram illustrating an illumination state on an image forming element according to a third embodiment.
FIG. 17 is a diagram illustrating an illumination state on an image forming element according to a fourth embodiment.
FIG. 18 is a schematic diagram of a projection optical system used in the fifth embodiment.
FIG. 19 is a schematic view of a sixth embodiment.
FIG. 20 is a diagram showing the relationship between the shape of a reflecting mirror used in a projection optical system according to a sixth embodiment and coordinate axes.
FIG. 21 is a flowchart showing a procedure for determining the shape and arrangement of a reflecting mirror;
FIG. 22 is a diagram showing a positional relationship of each reflecting mirror and each parameter of a reflecting surface shape.
FIG. 23 is a partially enlarged view of an image forming element and a reflective imaging optical system.
FIG. 24 is a schematic view of a seventh embodiment.
[Explanation of symbols]
1 Light source
2 Focusing mirror
3 Light tunnel (brightness unevenness reduction element)
3a incident end face
3b emission surface
4a @ First lens
4b @ second lens
4c @ 3rd lens
4d Reflective optical element with positive power
40 ° lens system
Optical system with 41 ° positive power
42 Reflective optical element with positive power
5 reflection mirror
6 Image forming element
6a @ Transmissive image forming element
60 ° irradiation area
7 Projection lens
7a 1st reflector (concave mirror)
7b Second reflector (convex mirror)
7c @ 3rd reflecting mirror (concave mirror or convex mirror)
7d 4th reflector (convex mirror)
70 ° reflective imaging optics
8 chief ray
8a incident light flux
8b @ outgoing beam
9 screen
10 ° normal of image forming element
11 illumination optical system
12a flat mirror
12b flat mirror
13a Curve showing illuminance distribution
13b Curve indicating illuminance distribution

Claims (15)

  1. A light source, a condensing mirror for converging light rays from the light source to form a virtual secondary light source, and an incident end face at the position of the secondary light source to make the luminance distribution of the luminous flux from the secondary light source uniform. Having an afocal optical system having an emission surface for emitting a light beam from the object surface as an image surface and an emission surface of the brightness unevenness reduction element as an image surface. Lighting optics.
  2. In a light beam from an arbitrary point on the object plane in the afocal optical system, any ray passing through the center of the light beam has an angle of 5 ° with the normal to the image plane when exiting from the image plane of the afocal optical system. 2. The illumination optical system according to claim 1, wherein:
  3. 3. The illumination optical system according to claim 1, wherein the afocal optical system has at least two refractive optical elements.
  4. 3. The illumination optical system according to claim 1, wherein the afocal optical system has at least one refractive optical element and at least one reflective optical element.
  5. 5. The illumination optical system according to claim 1, wherein the afocal optical system has at least one aspherical optical element.
  6. 6. The illumination optical system according to claim 1, wherein each of the optical elements constituting the afocal optical system is disposed so as to be rotationally eccentric with respect to an optical axis passing through the center of the luminance unevenness reducing element. system.
  7. An illumination optical system including an afocal optical system; an image forming element disposed at a position of an irradiation surface of the afocal optical system forming the illumination optical system; and an image forming element disposed on an emission side of the image forming element. A projection optical system for projecting a light beam emitted from the element onto a screen, and any light ray passing through the center of the light beam emitted from an arbitrary point of the image forming element has an angle with the normal line of the image forming element. An enlarged projection display device characterized by being at least 5 °.
  8. The enlarged projection type display device according to claim 7, wherein the afocal optical system has at least two refractive optical elements.
  9. The enlarged projection display apparatus according to claim 7, wherein the afocal optical system has at least one refractive optical element and at least one reflective optical element.
  10. 10. The enlarged projection display device according to claim 7, wherein the afocal optical system has at least one aspherical optical element.
  11. Each optical element constituting the afocal optical system included in the illumination optical system is arranged so as to be rotationally eccentric with respect to an optical axis passing through the center of the luminance unevenness reduction element constituting the illumination optical system. The enlarged projection display device according to any one of claims 7 to 10.
  12. A projection optical system for projecting a light beam emitted from the image forming element onto a screen comprises a telecentric refraction imaging optical system, and the refraction imaging optical system is decentered with respect to an optical axis of the refraction imaging optical system. The enlarged projection type display device according to any one of claims 7 to 11, wherein the enlarged projection type display device has a squeezed aperture.
  13. A projection optical system for projecting a light beam emitted from the image forming element onto a screen comprises a telecentric reflection type imaging optical system, and the reflection type imaging optical system has a rotationally symmetric aspheric surface having a reflection surface facing the image forming element. A first reflecting mirror having a concave reflecting surface having a shape; a second reflecting mirror having a convex reflecting surface having a rotationally symmetric aspherical shape with a reflecting surface directed to a light beam from the first reflecting mirror; A third reflecting mirror having a rotationally symmetric aspherical concave reflecting surface in which the reflecting surface is directed to the light beam from the second reflecting mirror, and a rotationally symmetric in which the reflecting surface is directed to the light beam from the third reflecting mirror The enlarged projection display device according to any one of claims 7 to 11, comprising a fourth reflecting mirror having an aspherical convex reflecting surface.
  14. A projection optical system for projecting a light beam emitted from the image forming element onto a screen comprises a telecentric reflection type imaging optical system, and the reflection type imaging optical system has a rotationally symmetric aspheric surface having a reflection surface facing the image forming element. A first reflecting mirror having a concave reflecting surface having a shape; a second reflecting mirror having a convex reflecting surface having a rotationally symmetric aspherical shape with a reflecting surface directed to a light beam from the first reflecting mirror; A third reflecting mirror having a rotationally symmetric aspherical convex reflecting surface having a reflecting surface directed to a light beam from the second reflecting mirror, and a rotationally symmetric having a reflecting surface facing the light beam from the third reflecting mirror The enlarged projection display device according to any one of claims 7 to 11, comprising a fourth reflecting mirror having an aspherical convex reflecting surface.
  15. The reflecting surface shape of the reflecting mirror constituting the reflective imaging optical system is such that the optical axis of the reflecting mirror is the z-axis, the plane perpendicular to the z-axis is the xy plane, and the origin is the intersection of the z-axis and the xy plane. When the coordinate axes are set with the axes O and the origin O intersecting at right angles on the xy plane and orthogonal to each other on the xy plane, a rotationally symmetric aspherical shape expressed by the following equations (1) to (3) is used. An enlarged projection display device according to claim 13 or 14.
    ρ 2 = x 2 + y 2 (2)
    c = 1 / r (3)
    Here, α i (i = 1, 2,..., 8) is a correction coefficient, k is a cone coefficient, and r is a radius of curvature.
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