JP2015138148A - Projection optical system, image projection device, and expanded image shift adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refractive-reflective projection optical system which allows position adjustment of an expanded image in a large area on a screen while minimizing quality deterioration of the expanded image.SOLUTION: A projection optical system is for expanding and projecting an image displayed on an image display element 10 as an expanded image onto a projection surface S and includes, in order from a reduction side to an expansion side, a first refractive optical system 21, a second refractive optical system 22, and a curved mirror 23. The first refractive optical system forms an intermediate image Im1 of the image displayed on the image display element between the first refractive optical system and the second refractive optical system, while the second refractive optical system and the curved mirror function to expand and project the light forming the intermediate image Im1 onto the projection surface to form an expanded image. The first refractive optical system 21 is a coaxial optical system comprising optical elements that share an optical axis, and is also a bi-telecentric optical system that is telecentric both on the image display element side and intermediate image side.

Description

  The present invention relates to a projection optical system, an image projection apparatus, and an enlarged image displacement adjustment method.

  The image projection apparatus can be implemented as a projector. Therefore, the image projection apparatus is also referred to as “projector” below.

  2. Description of the Related Art Conventionally, various image projection apparatuses that enlarge and project an image displayed on an image display element as an enlarged image on a projection surface (hereinafter also referred to as “screen”) by a projection optical system are known (Patent Documents). 1-6).

  Recently, there has been known a projection optical system configured by a combination of a refractive optical system (lens system) and a curved mirror (Patent Documents 2 to 6).

  Hereinafter, such a “projection optical system combining a refractive optical system and a curved mirror” will be referred to as a refractive / reflective projection optical system for convenience.

  Two examples of the refractive / reflective projection optical system will be briefly described with reference to FIGS.

  FIG. 2 is a diagram for explaining a projection optical system in which the refractive optical system L and the convex mirror MN are combined.

  An image displayed on the image display element denoted by reference numeral 0 is enlarged by the refractive optical system L and the convex mirror MN, formed as an enlarged image on the screen S, and enlarged and projected.

  FIG. 3 is a diagram for explaining a projection optical system in which the refractive optical system L and the concave mirror MP are combined.

  The image displayed on the image display element 0 is magnified by the refractive optical system L and the concave mirror MP, formed on the screen S as a magnified image, and magnified and projected.

  Each of the refractive / reflective projection optical systems shown in FIG. 2 and FIG. 3 forms an image on the screen S by folding the imaged light beam with the “curved mirrors MN and MP having an enlargement function”.

  For this reason, the arrangement of the image projection apparatus loaded with the projection optical system can be brought close to the screen S, and a so-called “ultra-close projector” becomes possible.

  By the way, in a projector, “enlarged image displacement adjustment” for adjusting the displacement of the “position of the enlarged image projected on the screen” on the screen is generally desired.

  In the case of a projection optical system composed only of a refractive optical system, this type of enlarged image displacement adjustment can be easily performed by displacing the lens system forming the refractive optical system in the “perpendicular direction to the optical axis”.

  In the refracting / reflecting projection optical system, the simplest method for adjusting the enlarged image displacement is a method of displacing the entire image projection apparatus.

  In the case of this method, in order to displace the entire image projection apparatus, it is troublesome to greatly displace energy necessary for displacement.

Further, when the refractive / reflective projection optical system is displaced in the casing of the image projection apparatus, a space for displacement of the projection optical system is required in the casing.
For this reason, the enlargement of a casing will be caused.

As another method, an enlarged image displacement adjustment method in which only the refractive optical system is displaced in the direction orthogonal to the optical axis can be considered.
However, in this method, due to the displacement of the refractive optical system, the positional relationship of the refractive optical system with respect to the curved mirror changes, so that aberration occurs, and the quality of the projected enlarged image tends to deteriorate.

  For this reason, in the enlarged image displacement adjustment method in which only the refractive optical system is displaced by the refraction / reflection type projection optical system, the displacement amount of the enlarged image (hereinafter referred to as “enlarged image shift amount”) is the size of the enlarged image. About 4% is considered the limit.

  An object of the present invention is to realize a refractive / reflective projection optical system capable of adjusting the position of a magnified image in a large range on a screen while suppressing deterioration in image quality of the magnified image.

  A projection optical system according to the present invention is a projection optical system for enlarging and projecting an image displayed on an image display element as an enlarged image on a projection surface, and sequentially proceeds from a reduction side to an enlargement side. The refractive optical system, the second refractive optical system, and the curved mirror are arranged, and the first refractive optical system converts the intermediate image of the image displayed on the image display element into the first refractive optical system and the second refractive optical system. The second refracting optical system and the curved mirror have a function of enlarging and projecting the light formed on the intermediate image onto the projection surface to form an enlarged image. The first refractive optical system is a coaxial optical system in which the optical elements constituting the first refractive optical system share the optical axis, and both the image display element side and the intermediate image side are telecentric. Telecentric optical system.

  According to the present invention, it is possible to realize a refractive / reflective projection optical system capable of adjusting the position of the enlarged image in a large range on the screen while suppressing the deterioration of the image quality of the enlarged image.

It is a figure for demonstrating a projection optical apparatus. It is explanatory drawing explaining the refraction and reflection type projection optical system using a convex mirror. It is explanatory drawing explaining the refraction and reflection type projection optical system using a concave mirror. It is a figure which shows one Embodiment of a projection optical system as explanatory drawing. It is a figure for demonstrating the expansion image displacement adjustment in the projection optical system of FIG. It is a figure which shows the case where a 1st refractive optical system is not a both-sides telecentric optical system as a comparative example. It is a figure for demonstrating the state which displaced the 1st refractive optical system by the comparative example shown in FIG. It is a figure which shows the 1st refractive optical system of the projection optical system of an Example. It is a figure which shows the data of the 1st refractive optical system of an Example. It is a figure which shows the 2nd refractive optical system and curved-surface mirror of the projection optical system of an Example. It is a figure which shows the data of the 2nd refractive optical system of an Example. It is a figure which shows the data of the aspherical surface in the 2nd refractive optical system of an Example. It is a figure which shows the data of the free-form surface of the curved mirror of an Example. It is a figure for demonstrating an example of the image projection apparatus using the projection optical system of an Example.

Hereinafter, embodiments will be described.
First, an overview of the projection optical apparatus will be described with reference to FIG.
FIG. 1 is a diagram mainly illustrating an image display element and its illumination optical system.

  In FIG. 1, reference numeral 10 denotes an “image display element”.

  As the image display element 10, a known appropriate element such as DMD (Digital Micromirror Array Device manufactured by Texas Instruments) or a liquid crystal panel can be used.

  The liquid crystal panel can be used for both a reflection type and a projection type.

  Since the DMD and the liquid crystal panel do not have a “self-emitting function” that emits light by themselves, an illumination optical system that illuminates a displayed image is required.

  However, the image display element is not limited to these, and an element having a self-luminous function, such as an LED array, can be used. In that case, an illumination optical system is unnecessary.

  For the sake of concreteness of description, the image display element 10 in the embodiment shown in FIG. 1 is assumed to be a DMD. However, the image projection device of the present invention is of course not limited to any kind.

  Illumination by the illumination optical system will be described.

The light source 1 includes a lamp 1A and a reflector 1B.
When the lamp 1 </ b> A emits light, the reflector 1 </ b> B reflects the light from the lamp 1 </ b> A and focuses it on the incident portion of the integrator rod 3.

  The integrator rod 3 is a light pipe in which four strip-shaped plane mirrors are combined in a tunnel shape.

  The light condensed on the incident part of the integrator rod 3 is guided while being repeatedly reflected in the light pipe and emitted from the emission part.

  At this time, the emission part functions as a “surface of uniform light intensity”. The light emitted from the integrator rod 3 passes through the lens system 5 and is bent in the optical path by the mirror 7.

  The light reflected by the mirror 7 is incident on and reflected by the curved mirror 9 and is irradiated on the image display surface of the DMD 10.

  A large number of micromirrors are two-dimensionally arrayed on the image display surface of the DMD 10, and each micromirror can tilt the mirror surface within a tilt angle range of +12 degrees to -12 degrees.

  The “image to be enlarged and projected” is displayed as a two-dimensional distribution of tilted micromirrors.

  The image displayed on the image display surface in this way is illuminated by the reflected light from the curved mirror 9.

  The lens system 5, the mirror 7, and the curved mirror 9 which are optical systems arranged between the integrator rod 3 and the image display surface constitute an “imaging optical system”.

  The imaging optical system forms an enlarged image on the image display surface using the above-mentioned “surface of uniform light intensity” in the exit portion of the integrator rod 3 as an object.

  Therefore, the image display surface is illuminated with “uniform light intensity (uniform illuminance distribution)”. The mirror 7 may be a plane mirror or a curved mirror having power.

  The inclination of the micromirror on the image display surface of the DMD 10 is set so that, for example, the reflected light enters the projection optical system 100 when it is −12 degrees and does not enter when it is + 12 °.

  The light reflected by the image display surface and incident on the projection optical system 100 is intensity-modulated by the image displayed on the image display surface.

The projection optical system 100 forms an image of incident light on a screen (not shown).
The image formed is an enlarged image of the image displayed on the image display surface.

  As will be described below, the projection optical system of the present invention has a refractive optical system and a curved mirror, and the refractive optical system has first and second refractive optical systems.

  Before describing specific examples of the projection optical system, a description will be given through embodiments.

  FIG. 4 is a diagram showing an embodiment of the projection optical system according to the present invention as an explanatory diagram.

In FIG. 4, reference numeral 10 denotes an image display element (assuming a DMD, but of course not limited to this) as in FIG.
FIG. 4 shows an “image display surface portion” of the image display element 10. The same applies to the following drawings.

  Reference numeral 21 denotes a first refractive optical system, reference numeral 22 denotes a second refractive optical system, and reference numeral 23 denotes a curved mirror.

The first refractive optical system 21 and the second refractive optical system 22 constitute a “refractive optical system”, and the refractive optical system and the curved mirror 23 constitute a projection optical system.
Although not shown in FIG. 4, an aperture stop is disposed in the first refractive optical system 22.

  The arrows shown in FIG. 4 are light rays from the image display surface of the image display element 10, and these are all “principal rays”.

  The “principal ray” is a ray passing through the center of the entrance pupil of the imaging optical system (in the illustrated example, located in the first refractive optical system) as generally defined.

  The first refractive optical system 21 is a coaxial optical system in which the optical elements L11 and L12 constituting the first refractive optical system "share the optical axis".

  In FIG. 4, the first refractive optical system 21 is depicted as including two lenses L11 and L12.

  This is for convenience of explanation, and it goes without saying that the number of lenses constituting the first refractive optical system 21 is not limited to two.

  In the state shown in FIG. 4, the first refractive optical system 21 and the second refractive optical system 22 share the optical axis.

  When light from the image display surface of the image display element 10 enters the first refractive optical system 21, an intermediate image Im1 is formed by the imaging action of the first refractive optical system as shown in the figure.

  The imaging position of the intermediate image Im1 is “between the first refractive optical system 21 and the second refractive optical system 22”.

  The light that forms the intermediate image Im1 is incident on the second refractive optical system 22, and the second intermediate image Im2 is formed in front of the curved mirror 23 by using the first intermediate image Im1 as an object.

  The curved mirror 23 is a “concave mirror” in this example, and forms an enlarged image on a screen (not shown) using the second intermediate image Im2 as an object.

  That is, the first refractive optical system 21 has a function of forming an intermediate image Im1 of an image displayed on the image display element 10 between the first refractive optical system 21 and the second refractive optical system 22. .

  The second refractive optical system 22 and the curved mirror 23 have a function of enlarging and projecting the intermediate image Im1 on a screen (projected surface) (not shown) to form an enlarged image.

  Now, all the principal rays shown in FIG. 4 are “parallel to the optical axis” on both the object side (reduction side) and the image side (enlargement side) of the first refractive optical system 21.

  That is, the first refractive optical system 21 is a “bilateral telecentric optical system” that is telecentric on both the image display element 10 side (reduction side) and the intermediate image Im1 side (enlargement side).

  In the state shown in FIG. 4, the first refractive optical system 21 and the second refractive optical system 22 constituting the refractive optical system share the optical axis.

  The positional relationship between the second refractive optical system 22 and the curved mirror 23 is set to “designed positional relationship”.

  Hereinafter, this state is referred to as a “reference state” in the projection optical system.

  In this reference state, the position of the enlarged image projected on the screen is referred to as “reference projected image position”.

  “Displacement adjustment with respect to the reference projected image position” of the position of the enlarged image projected on the screen will be described below.

  FIG. 5 shows a state in which only the first refractive optical system 21 is displaced from the reference state shown in FIG. 4 in a direction (upward in the drawing) perpendicular to the optical axis of the refractive optical system.

  The displacement amount in this displacement is called “shift amount” and is represented by “Δ”.

  That is, the state of FIG. 5 is a state in which only the first refractive optical system 21 is displaced by a shift amount: Δ in the direction orthogonal to the optical axis from the reference state shown in FIG.

  Due to this displacement, the positional relationship between the image display element 10 and the first refractive optical system 21 is relatively shifted in the optical axis orthogonal direction (vertical direction in the figure).

  However, since the first refractive optical system 21 is a “bilateral telecentric optical system”, all principal rays are parallel to the optical axis of the first refractive optical system 21 regardless of the presence of the shift amount Δ.

  At this time, the first intermediate image Im1A imaged by the first refractive optical system 21 is shifted in the direction perpendicular to the optical axis (upward in the drawing) from the imaging position in the reference state.

  The “shift amount with respect to the intermediate image Im1 (FIG. 4)” of the first intermediate image Im1A is the product of the lateral magnification: β1 and the shift amount: Δ of the first refractive optical system 21: Δ · β1.

  The light that forms the first intermediate image Im1A is then imaged by the first refractive optical system 21 as the second intermediate image Im2A.

  At this time, the “deviation amount with respect to the intermediate image Im2 (FIG. 4)” of the second intermediate image Im2A is a product of the lateral magnification: β2 of the second refractive optical system 22 and the deviation amount: Δ · β1. .

  That is, the shift amount of the second intermediate image Im2A is “Δ · β1 · β2”.

  The light that forms the second intermediate image Im2A is then enlarged and projected as an enlarged image on a screen (not shown) by the curved mirror 23.

  The “displacement amount with respect to the reference projection image position” of the enlarged image projected on the screen is a product of the lateral magnification of the curved mirror 23: β3 and the deviation amount: Δ · β1 · β2.

  That is, when the first refractive optical system 21 is displaced by a shift amount: Δ in the direction orthogonal to the optical axis from the reference state shown in FIG. 4, the enlarged image on the screen is displaced by “Δ · β1 · β2 · β3”.

  As shown in FIG. 5, with respect to the shift amount: Δ (≠ 0) in the range where the “bilateral telecentricity” of the first refractive optical system 21 is established, the first intermediate image: Im1A is “aberrated. "Deterioration" does not occur.

  Further, the second refractive optical system 23 always receives parallel principal rays regardless of the shift amount: Δ (≠) due to the bilateral telecentricity of the first refractive optical system 21.

  Accordingly, the aberration does not deteriorate even when the intermediate image Im2A is formed.

  The amount of displacement of the enlarged image on the screen: Δ · β1 · β2 · β3 is determined by the maximum value of the shift amount: Δ and the lateral magnifications: β1, β2, and β3, all of which are determined as design conditions.

  Accordingly, by appropriately setting these, a displacement having a desired size can be given to the enlarged image on the screen.

  As described above, in the projection optical system of the present invention, the first refractive optical system is a “double-sided telecentric optical system” that is telecentric on the enlargement side / reduction side.

  Here, for comparison, an example in which the first refractive optical system is not the “bilateral telecentric optical system” will be described as a “comparative example” with reference to FIGS. 6 and 7.

  In order to avoid complications, for those that are not likely to be confused, the reference numerals in FIGS.

  Accordingly, also in FIGS. 6 and 7, reference numeral 10 denotes an image display element, reference numeral 21 denotes a first refractive optical system, reference numeral 22 denotes a second refractive optical system, and reference numeral 23 denotes a curved mirror.

  In the examples of FIGS. 6 and 7, the first refractive optical system 21 is not telecentric on both the object side (reduction side) and the image side (enlargement side).

  FIG. 6 shows a state in which the optical axis of the first refractive optical system 21 and the optical axis of the second refractive optical system 22 are coincident (also called “reference state” in this case, following the case of FIG. 4). ).

An intermediate image formed by the first refractive optical system 21 in this reference state is referred to as a first intermediate image Im10.
In order to distinguish it from the first intermediate image Im1 in the case of FIG. 4, the symbol is Im10.

  In this case, the chief rays that form the first intermediate image Im10 are not parallel to each other.

  The light formed on the first intermediate image Im10 is formed as a second intermediate image Im20 by the second refractive optical system 22.

  Then, an enlarged image of the second intermediate image Im20 by the curved mirror 23 is enlarged and projected as a “magnified image of the image displayed on the image display element 10” on a screen (not shown).

  4 and FIG. 5, the position of the enlarged image projected on the screen in this case is also referred to as “reference projected image position”.

  At this time, it is of course possible to design the first and second refractive optical systems and the curved mirror so that the enlarged image projected on the “reference projected image position” is good.

  FIG. 7 shows a state in which only the first refractive optical system 21 is displaced from the reference state shown in FIG. 6 by the shift amount Δ in the direction perpendicular to the optical axis.

  Since the first refractive optical system 21 is not telecentric, even when the first refractive optical system 21 is displaced as shown in FIG. 7, the principal rays emitted from the first refractive optical system 21 are not parallel to each other.

  For this reason, “deterioration of aberration” is also likely to occur with respect to the first intermediate image Im10A.

In addition, since the principal rays that form the first intermediate image Im10A are not parallel to each other, the angle of the rays incident on the second refractive optical system 22 changes for each incident position on the lens surface.
For this reason, when the second intermediate image (not shown) is formed by the second refractive optical system 22, the aberration is greatly deteriorated.

  Accordingly, in the case of the projection optical system as shown in FIGS. 6 and 7, “enlarged image displacement adjustment by displacement of only the first refractive optical system” is favorably performed without image quality degradation of the enlarged image. Have difficulty.

  As described with reference to FIGS. 4 and 5, the displacement amount of the enlarged image on the screen is “Δ · β1 · β2 · β3”.

  Δ is the displacement (shift amount) of the first refractive optical system, and β1, β2, and β3 are the lateral magnifications of the first and second refractive optical systems and the curved mirror, respectively.

These Δ, β1 to β3 can be appropriately set as design conditions.
However, from the viewpoint of the compactness of the projection optical system and, in turn, the compactness of the image projection apparatus and the suppression of variations in image quality, the lateral magnification: β1 should satisfy the following conditions.

  That is, it is preferable that the lateral magnification β1 of the first refractive optical system (both sides telecentric optical system) is in the range of 0.9 to 4.0.

  When the lateral magnification β1 of the first refractive optical system is in the above range, the size of the first intermediate images Im1 and Im1A, the second intermediate images Im2 and Im2A, and the size of the curved mirror can be reduced.

  The “size” of the intermediate image and the curved mirror mentioned above is the size in the vertical direction in FIGS. 4 and 5.

  If the size of the intermediate image and the curved mirror can be kept small, the lens size of the second refractive optical system and the size of the curved mirror can be kept small.

  Therefore, suppressing the lateral magnification: β1 within the above range greatly contributes to downsizing (compactness) of the projection optical system and, in turn, the image projection apparatus.

  The lateral magnification β1 of the first refractive optical system is more preferably “substantially the same magnification (ie, near 1 ×)” within the above range.

When the lateral magnification of the first refractive optical system is approximately equal, the longitudinal magnification (= β1 ² ) is also approximately equal to 1.

  Therefore, even if the positional relationship between the first refractive optical system and the image display element is slightly shifted in the normal direction of the image display surface, the imaging position of the first intermediate image is the optical axis direction of the first refractive optical system. Does not change significantly.

  A description will be given with reference to FIGS.

For example, when the lateral magnification of the first refractive optical system is β1 = 1, the longitudinal magnification is also β1.
At this time, it is assumed that the positional relationship between the image display surface and the first refractive optical system is shifted by a minute amount: ΔZ in the optical axis direction of the second refractive optical system 22.

  As described above, when the “positional relationship between the image display surface and the first refractive optical system 21” is shifted by a minute amount: ΔZ, the change in the image forming position of the first intermediate image Im1 or Im1A is also ΔZ. is there.

  Since ΔZ is very small, the positional relationship between the first intermediate image and the second refractive optical system is also very small, and the deterioration of aberration during the formation of the second intermediate image Im2 or Im2A does not increase.

  That is, by setting the lateral magnification β1 to be close to 1, the requirement for the assembly accuracy of the projection optical system is effectively relaxed, and the assembly work of the projection optical system and the projection optical system is facilitated.

  On the other hand, consider a case where the first refractive optical system 21 is assembled with the “position shift of ΔZ” with respect to the image display element 10 in the case of a large lateral magnification such as β1 = 10.

  In this case, the “deviation amount” of the imaging positions of the first intermediate images Im1 and Im1A1 is 100ΔZ, and the positional relationship between the first intermediate image and the second refractive optical system 22 is significantly shifted.

  For this reason, it is conceivable that the image cannot be focused on the screen.

  In order to avoid such a situation, it is necessary to assemble the “image display element and the first refractive optical system” with extremely high accuracy.

  In the projection optical system of the present invention, as described above, the first refractive optical system is a “bilateral telecentric optical system”, but the second refractive optical system is not particularly required to have telecentricity.

However, the second refractive optical system is also preferably “an optical system telecentric with respect to the intermediate image formed by the first refractive optical system”.
In this way, all the principal rays that form the first intermediate image Im1A enter the second refractive optical system “parallel to the optical axis”.

  Accordingly, it is possible to effectively suppress the deterioration of the aberration when the second intermediate image Im2A is formed by the second refractive optical system, and the image quality of the enlarged image whose enlarged image displacement is adjusted can be kept “better”.

  Hereinafter, specific examples of the projection optical system will be described.

  FIG. 8 is a diagram illustrating a “first refractive optical system” in the embodiment of the projection optical system.

  As shown in the figure, the “Z direction” is taken in the optical axis direction of the first optical system, the vertical direction in the figure is taken as the “Y direction”, and the direction orthogonal to the drawing is taken as the “X direction”.

  Since there is no possibility of confusion, the first refractive optical system is represented by reference numeral 21 and the image display element is represented by reference numeral 10 as in FIGS.

  Further, the symbol “Im1” represents a “first intermediate image”.

  The first refractive optical system 21 is rotationally symmetric with respect to the optical axis.

  The image displayed on the image display surface of the image display element 10 is formed as a first intermediate image Im1 by the first refractive optical system 21.

  The first refractive optical system 21 includes 10 lenses and an aperture stop S as shown in the figure, and the aperture stop S is disposed between the fifth and sixth lenses as counted from the object side (reduction side). Has been.

  “A set of five lenses” on the image display element 10 side of the aperture stop S is a lens group L1A, and a “set of five lenses” on the enlargement side is a lens group L1B.

  The light beam width that enters the first refractive optical system 21 from the image display element 10 is regulated by the aperture stop S.

  In FIG. 8, the lens unit L1A is configured so that the focal position is the center position of the aperture stop S when a “parallel light beam parallel to the optical axis” enters from the left to the right in the figure. .

  With this configuration, the lens unit L1A is “telecentric on the object side, that is, on the reduction side”.

  The lens unit L1B is configured such that the focal position is the center position of the aperture stop S when a “parallel light beam parallel to the optical axis” is incident from the right side of the drawing, that is, from the enlargement side. .

  With this configuration, the lens unit L1B is “telecentric on the enlargement side, that is, on the first intermediate image Im1 side”.

  Accordingly, the first refractive optical system 21 including the lens groups L1A and L1B and the aperture stop S is a “both-side telecentric optical system” telecentric on the reduction side and the enlargement side.

  In FIG. 8, “three rays for each of these pixels” are drawn using three pixels on the pixel display surface of the image display element 10 as light sources.

  Of the three rays from each pixel, the principal rays passing through the center of the aperture stop S are orthogonal to the image display surface and the image plane of the first intermediate image Im1, and are parallel to each other. is there.

  That is, even if the first refractive optical system 21 is displaced parallel to the image display surface (Y direction in FIG. 8), the chief ray entering the first intermediate image Im1 is always the first intermediate image Im1. It is perpendicular to the image plane.

  The lateral magnification of the first refractive optical system 21 is 1.0.

  The positional relationship of the first refractive optical system 21 with respect to the image display element 10 may deviate from the normal positional relationship due to, for example, an assembly error at a shipping factory.

  As described above, even if the first refractive optical system 21 is displaced in the Z direction with respect to the image display element 10, the “shift amount in the Z direction” of the first intermediate image Im 1 is the displacement of the first refractive optical system 21. Is the same as the amount.

  Originally, the shift due to the assembly error or the like is “minute”, and therefore the “shift amount” in the Z direction of the first intermediate image Im1 is also minute.

Therefore, a large focus shift does not occur in the “enlarged image on the screen” due to the “shift”.
From the viewpoint of compactness of the image projection apparatus and suppression of variations in image quality, the preferred range of the lateral magnification of the first refractive optical system is the range of 0.9 to 4.0 as described above.

  When the lateral magnification of the first refractive optical system exceeds 4 times, the amount of deviation in the Z direction of the first refractive optical system with respect to the image display element 10 expands to 16 times or more as the amount of deviation of the first intermediate image Im1. Is done.

  For this reason, there is a possibility that “the amount of defocusing of the enlarged image” on the screen exceeds the allowable level.

  In addition, the lens diameter of the second refractive optical system increases, which tends to increase the size of the projection optical system and thus the image projection apparatus.

  The first refractive optical system 21 shown in FIG. 8 is held by a “shift adjusting mechanism” and is displaced in the Y direction in FIG. 8 inside the projector.

  FIG. 9 shows data of the first refractive optical system 21 shown in FIG. In FIG. 9, “surface number” is the surface number counted from the reduction side.

  The image display element is provided with a parallel plate-like cover glass in contact with the image display surface. The image display surface side of this cover glass is surface number: 0, and the surface on the first refractive optical system side is surface number 1.

“1.0E + 18” representing the curvature radii of these surface numbers: 0 and 1 means “1.0 × 10 ¹⁸ ”, and is also used for the following aspheric surfaces and free-form surfaces.

  “1.0E + 18” is substantially infinite.

FIG. 10 shows the “second refractive optical system” of the embodiment and a curved mirror.
Since there is no possibility of confusion, the second refractive optical system is represented by reference numeral 22 and the curved mirror is represented by reference numeral 23 in FIG. 10 as in FIG.

  The second refractive optical system 22 shown in FIG. 10 is combined with the enlargement side of the first refractive optical system 21 shown in FIG.

  The second refractive optical system 22 has a telecentric configuration on the first intermediate image Im1 side.

The second refractive optical system 22 is composed of 15 lenses.
FIG. 11 shows data of the second refractive optical system 22 and the curved mirror 23 shown in FIG.

  As described above, the first refractive optical system 21 shown in FIG. 8 can be displaced in the optical axis orthogonal direction (Y direction) with respect to the second refractive optical system 22.

  In FIG. 11, lenses having surface numbers 1 and 2 are “parallel flat glass”.

  The plane of surface number 1 of the parallel flat glass is located at a distance of 1 mm with respect to the first intermediate image Im1 (indicated as “intermediate image 1” in FIG. 11).

  Surface number 2 is the surface on the enlarged side of the parallel flat glass.

  A “beam stop” having an aperture diameter of 8.5 mm is formed on the lens surface of surface number 9.

  When parallel light rays parallel to the optical axis are incident on the lens groups of surface numbers 1 to 9 from the left in FIG. 10, the focal position is set to “the center of the light beam stop position” of the surface 9.

  That is, the lens groups having the surface numbers 1 to 9 have a configuration in which the first intermediate image Im1 side is telecentric, and aberrations are not deteriorated even when light from the first refractive optical system 21 is received.

  As shown in FIG. 11, the second refractive optical system 22 includes aspheric surfaces (surface numbers: 3, 4, 23 to 28).

Further, the mirror surface shape of the curved mirror 23 (indicated as “concave mirror” in FIG. 11) is a “free curved surface”.
FIG. 12 shows the aspheric data of the second refractive optical system.

  The lower diagram of FIG. 12 shows an “aspheric shape formula” representing an aspheric surface.

  “Aspherical surface” is represented by the following well-known aspherical shape formula.

"Aspherical surface type"
D = C · H ² / [1 + √ {1- (1 + K) C ² · H ² }]
+ E ₄・ H ⁴ + E ₆・ H ⁶ + E ₈・ H ⁸ + E ₁₀・ H ¹⁰ + E ₁₂・ H ¹² + ・ ・
In this aspheric shape formula, “D” is the amount of aspheric surface, “H” is the distance from the optical axis, “C” is the paraxial curvature, “K” is the elliptic constant, “E ₄ , E ₆ ,. “ ₁₂ ...” Is a higher-order aspheric coefficient.

  FIG. 13 shows data of a free curved surface that forms the mirror surface of the curved mirror 23.

  The “free curved surface” is represented by the following well-known “free curved surface shape formula”.

"Free-form surface form"
^{z = c · h 2 / [} 1 + √ {1- (1 + k) c 2 · h 2}] + ΣCjx m y n
In this free-form surface shape formula, “c” on the right side is the curvature in the vicinity of the vertex in the z direction of the free-form surface.
“K” is an elliptic constant, and x and y are two directions orthogonal to the z direction and orthogonal to each other, and are coordinates representing the position of the free-form surface.
“H” represents a distance from an axis passing through the vertex and parallel to the z direction.
“H = √ (x ² + y ² )”.

  In the curved mirror 23, as shown in FIG. 11, the “vertex position” is shifted by “−0.7 mm” in the Y direction with respect to the optical axis of the second refractive optical system, and the z direction is parallel to the YZ plane. In this arrangement, the optical axis is inclined by 3.0 degrees clockwise with respect to the optical axis.

  The x direction intersects the YZ plane, and the y direction is in the YZ plane.

  FIG. 14 shows a projector in which the first refractive optical system 21, the second refractive optical system 22, and the curved mirror 23 are combined in the casing CS in the embodiment described above.

  In FIG. 14, the projection optical system described above is provided together with an image display element, an illumination optical system, and the like in an “casing of the image projection apparatus” indicated by reference character CS.

  The image display element is, for example, a DMD, and the illumination optical system is, for example, “as described with reference to FIG.

  The left diagram of FIG. 14 shows a state when the position of the enlarged image on the screen S is “lowered most in the Y direction”.

  The right diagram in FIG. 14 shows a state when the position of the enlarged image on the screen S is “raised most in the Y direction”.

  The image display surface of the image display element has a rectangular shape, and the length of the side in the Y direction in FIG. 8 is 8.64 mm.

  The first refractive optical system 21 is laid out so that its optical axis coincides with the “upper position in the Y direction” on the image display surface in the reference state.

  Therefore, in this reference state, the lower end position in the Y direction of the first intermediate image formed by the first imaging optical system 21 matches the optical axis position of the first refractive optical system.

  The second refractive optical system 22 is laid out so that the optical axis is shifted by −4.0 mm in the Y direction with respect to the “lower end in the Y direction” of the first intermediate image formed in the reference state. Yes.

  That is, in the reference state, the optical axis of the second refractive optical system 22 is shifted by 4 mm toward the minus side in the Y direction with respect to the optical axis of the first refractive optical system 21.

  In the example described above with reference to FIGS. 4 and 5, the optical axis of the first refractive optical system 21 and the optical axis of the second refractive optical system “match in the reference state”.

  However, a layout in which the optical axes of the first and second refractive optical systems are “shifted from each other in the Y direction in the reference state” is also possible as in the embodiment being described.

  The left diagram of FIG. 14 shows only the first refractive optical system 21 while keeping the relative positions of the second refractive optical system 22 and the curved mirror 23 relative to the image display element 10 with respect to the “reference state”. The state is shown as “displaced by −1 mm in the Y direction” from the state.

  That is, the shift amount of the first refractive optical system: Δ = −1 mm.

  The right diagram of FIG. 14 shows only the first refractive optical system 21 with the relative positions of the second refractive optical system 22 and the curved mirror 23 relative to the image display element 10 as they are with respect to the “reference state”. The state is shown as “displaced by +0.4 mm in the Y direction” from the state.

  That is, the shift amount of the first refractive optical system: Δ = + 4 mm.

In the state of the left figure of FIG. 14, the optical axis of the first refractive optical system is located within the image display surface.
However, the optical axis of the second refractive optical system is deviated by 4 mm from the Y-direction end of the image display surface in the reference state, and the curved mirror also has a vertex position from the optical axis of the second refractive optical system. The deviation, z direction, is tilted clockwise with respect to the optical axis.

  Accordingly, light from the pixel closest to the optical axis of the first refractive optical system 21 on the image display surface is not reflected by the curved mirror 23 and returned to the image display surface side.

  In the state shown in the “left and right views” of FIG. 14, the “difference in the position of the enlarged image” on the screen S is 228 mm as shown in the figure.

  The size of the enlarged image on the screen S in the Y direction is 753 mm. This size is represented by “MS”.

  The ratio between the “difference in the position of the enlarged image” on the screen S and the MS is called “lens shift”.

  In the example being described, the lens shift is 0.3, which is 30% as a percentage.

  That is, the image projection apparatus (projector) shown in FIG. 14 can adjust the displacement of the enlarged image projected on the screen S by “30% of the enlarged image size” in the Y direction.

  If the lens shift is 0.3, the size by which the enlarged image can be displaced on the screen is “0.3 × MS”.

  Such “enlarged image displacement adjustment” is performed by adjusting and displacing only the first refractive optical system in the projection optical system in a direction perpendicular to the optical axis (Y direction in the above description).

  This displacement is performed by a “displacement mechanism” (not shown).

  The displacement of the first refractive optical system necessary for adjusting the enlarged image displacement is “displacement due to parallel movement”.

  Therefore, the displacement mechanism can be configured by appropriately using various conventionally known “mechanisms for adjusting parallel displacement in an adjustable manner”.

  Thus, by using the projection optical system according to the present invention, the conventional “projection optical system constituted only by a refractive optical system can be used without using a large-scale configuration that displaces the entire projection optical system including the curved mirror. The enlarged image displacement adjustment at the same level as in the case of "."

  As described above, in the method of “displacing only the refractive optical system” in the refraction / reflection type projection optical system, the “shift amount” of the enlarged image is considered to be limited to about 4% of the size of the enlarged image. .

  Therefore, even if the lens shift is 10% (0.1 × MS), it can be said that the practically sufficient enlargement image displacement adjustment can be performed.

As shown in FIG. 14, the casing CS is provided with dust-proof glass CG.
The dust-proof glass CG has a function of protecting the inside of the casing CS and emits an “imaging light beam” reflected by the curved mirror 23 toward the screen S side.

  In the image projection apparatus of the present invention, since the enlarged image displacement adjustment is performed by the displacement of the first refractive optical system, the change range of the direction of the imaging light beam reflected by the curved mirror 23 is large.

  When the range of change in the direction of the imaging light beam increases, the “width of the light beam exit surface area” of the dust-proof glass CG needs to be set large.

  This width of the dust-proof glass CG is determined by the light beam path when the position of the enlarged image on the screen S is located at the lower end (the left figure in FIG. 14) and at the upper end (the right figure in FIG. 13).

  In particular, when the enlarged image is positioned at the lower end, the influence on the “width of the light beam exit surface area” is large.

  This is because the ray angle with respect to the screen S becomes nearly vertical as shown in the left diagram of FIG. 14. If this angle is far from the vertical, the width may be small as shown in the right diagram of FIG.

  In order to prevent the width of the light exit surface area of the dust-proof glass CG from becoming too large, the incident angle of the light beam on the lowermost end in the Y direction of the enlarged image on the screen S is preferably 19 degrees or more.

  As shown in FIG. 10, the dust-proof glass CG is provided in contact with the “upper end portion in the Y direction” of the curved mirror 23.

  As shown in FIG. 11, the “position in the Y direction” at the center of the dust-proof glass CG is 31 mm (inner surface) and 34 mm (outer surface) from the optical axis of the first refractive optical system in the reference state. The thickness is 3 mm.

  The projection optical system of the present invention described above is a projection optical system for enlarging and projecting an image displayed on the image display element 10 as an enlarged image on the projection surface S, from the reduction side to the enlargement side. The first refractive optical system 21, the second refractive optical system 22, and the curved mirror 23 are arranged sequentially, and the first refractive optical system 21 is an intermediate image of the image displayed on the image display element 10. Im1 forms an image between the first refracting optical system 21 and the second refracting optical system 22, and the second refracting optical system 22 and the curved mirror 23 receive the light that forms the intermediate image Im1. The first refractive optical system 21 has a function of enlarging and projecting on the projection surface S to form an enlarged image. The first refractive optical system 21 is a coaxial in which each optical element constituting the first refractive optical system shares an optical axis. In the optical system, both the image display element 10 side and the intermediate image Im1 side are telecentric. Do a bilateral telecentric optical system.

  The lateral magnification of the first refractive optical system 21 with respect to the image formation of the intermediate image Im1 is preferably 0.9 times to 4.0 times, and particularly preferably approximately equal. In the embodiment, it is the same magnification.

In the projection optical system shown in the embodiment, the second refractive optical system 22 is an optical system telecentric with respect to the intermediate image Im1 formed by the first refractive optical system 21.
The curved mirror 23 is a concave mirror. However, the curved mirror is not limited to this, and a curved mirror may be formed by a convex mirror.

  The image projection apparatus described with reference to FIG. 14 is an image projection apparatus that enlarges and projects an image displayed on the image display element as an enlarged image on the projection surface S by the projection optical system. A projection optical system according to the present invention described above, and includes a first refractive optical system, a second refractive optical system, and a curved mirror. A displacement mechanism that relatively displaces the first refractive optical system and the image display element in a direction orthogonal to the optical axis of the first refractive optical system 21 is provided.

  This displacement mechanism displaces the first refractive optical system of the projection optical system in a direction perpendicular to the optical axis so that the displacement amount can be adjusted.

  The vertical direction (Y direction) width of the effective area in which the image of the image display element is displayed: the displacement amount that can be displaced by the displacement mechanism is 0.1 × MS or more with respect to MS (0.3 × MS in the embodiment). It is.

  In addition, the angle of light incident on the projection surface S is 19 degrees or more with respect to the outward normal of the projection surface.

  An enlarged image displacement adjustment method for adjusting the displacement of the enlarged image on the projection surface can be implemented using the displacement mechanism.

  In the above, the case where the position of the enlarged image is adjusted by displacing the first refractive optical system in the refractive optical system in the direction perpendicular to the optical axis has been described.

  However, the present invention is not limited to this case, and the enlarged image displacement adjustment can be performed by displacing the image display element 10 in the direction orthogonal to the optical axis of the refractive optical system with respect to the projection optical system.

  In this case, it is not necessary to displace the first refractive optical system in the refractive optical system in the direction orthogonal to the optical axis.

  Even in such a case, since the first refractive optical system is telecentric with respect to the reduction side and the enlargement side, the deviation between the optical axes with respect to the optical axis of the second refractive optical system does not affect the performance.

  Therefore, the assembly of the projection optical system is easy.

10 Image display element
21 First refractive optical system
22 Second refractive optical system
23 Curved mirror
Im1 first intermediate image
Im2 second intermediate image
Im1A First intermediate image when the first refractive optical system 21 is displaced
Im2A second intermediate image when the first refractive optical system 21 is displaced

JP 2011-237482 A Special table 2013-532313 gazette JP2013-15853A JP2013-33283A JP 2011-118548 A Japanese Patent No. 5182440

Claims (10)

A projection optical system for enlarging and projecting an image displayed on an image display element as an enlarged image on a projection surface,
In order from the reduction side to the enlargement side, a first refractive optical system, a second refractive optical system, and a curved mirror are arranged,
The first refractive optical system forms an intermediate image of the image displayed on the image display element between the first refractive optical system and the second refractive optical system,
The second refractive optical system and the curved mirror have a function of enlarging and projecting the light formed on the intermediate image onto the projection surface to form an enlarged image,
The first refractive optical system is a coaxial optical system in which each optical element constituting the first refractive optical system shares an optical axis, and both-side telecentric optics is telecentric on both the image display element side and the intermediate image side. Projection optical system. The projection optical system according to claim 1,
A projection optical system characterized in that the lateral magnification of the first refractive optical system with respect to the formation of the intermediate image is 0.9 times to 4.0 times. In the projection optical system according to claim 2,
A projection optical system characterized in that the lateral magnification of the first refractive optical system with respect to the intermediate image is approximately equal. In the projection optical system according to any one of claims 1 to 3,
A projection optical system, wherein the second refractive optical system is an optical system telecentric with respect to the intermediate image formed by the first refractive optical system. The projection optical system according to any one of claims 1 to 4,
A projection optical system, wherein the curved mirror is a concave mirror. An image projection apparatus that projects an image displayed on an image display element as a magnified image on a projection surface by a projection optical system,
An image display element and a projection optical system,
The projection optical system is described in any one of claims 1 to 5, and includes a first refractive optical system, a second refractive optical system, and a curved mirror,
An image projection apparatus comprising: a displacement mechanism that relatively displaces the first refractive optical system and the image display element of the projection optical system in a direction orthogonal to the optical axis of the first refractive optical system. The image projection apparatus according to claim 6,
The displacement mechanism displaces the first refractive optical system of the projection optical system in a direction orthogonal to the optical axis so that the displacement amount can be adjusted. In the image projection device according to claim 6 or 7,
The vertical width of the effective area where the image of the image display element is displayed:
An image projection apparatus characterized in that a displacement amount displaceable by a displacement mechanism is 0.1 × MS or more. The image projection apparatus according to any one of claims 6 to 8,
An image projection apparatus characterized in that a light ray incident on a projection surface has an angle of 19 degrees or more with respect to an outward normal of the projection surface.   An enlarged image displacement adjustment method for adjusting the displacement of an enlarged image on a projection surface using the displacement mechanism in the image projection apparatus according to claim 6.

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