JP2014048498A - Eccentric optical system, image projection device using eccentric optical system, and image pickup device using eccentric optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eccentric optical system that is able to project or pickup an image despite its small and simple structure, an image projection device using the eccentric optical system, and an image pickup device using the eccentric optical system.SOLUTION: An eccentric optical system comprises, in order from an image face to an object face, a first reflection member having a first reflection face oriented toward the image face side, and a second reflection member having a second reflection face oriented toward the object face side, opposite the first reflection face. Where an exit pupil is formed on the image face side of the first reflection face, and a beam from the image face to the center of the object face through the center of the exit pupil is assumed as an on-axis principal beam, the first reflection face and the second reflection face are arranged so as to be eccentric with respect to the on-axis principal beam.

Description

  The present invention relates to a decentered optical system in which reflecting mirrors are decentered, an image projecting apparatus using the decentered optical system, and an image pickup apparatus using the decentered optical system.

  2. Description of the Related Art Conventionally, there are known image projection apparatuses that use small image display elements and project an image obtained by enlarging an original image of these display elements with an optical system (Patent Documents 1 to 4). In order to make it high, it is desired to reduce the size and weight of the entire apparatus. In order to present an image, an optical system that can project an original image of a display element with a field angle for enlarging the image to a certain size and express it with a high resolution is required. As means for satisfying such a requirement, a decentered mirror, which is a concave mirror whose projecting optical system is decentered with respect to the observer's visual axis, is provided to project an enlarged virtual image of the image display element.

JP 2001-215212 A JP 2004-295042 A Japanese Patent No. 2004-258620 Japanese Patent No. 2006-235516

  Japanese Patent Application Laid-Open No. 2004-228561 corrects a chromatic aberration of a primary image of an image display element through a dichroic prism by a coaxial refraction system, forms an exit pupil, and a reflecting mirror disposed after a stop at the exit pupil position. The two images are enlarged and projected. In this projection optical system, since a refractive system is used between the primary image and the exit pupil, the number of optical elements is large, leading to high costs. Furthermore, since two reflecting mirrors are arranged after the exit pupil, the optical path length from the primary image to the two reflecting mirrors becomes long and the reflecting mirror becomes large, so that the entire apparatus becomes large.

  In Patent Documents 2 to 4, an original image of an image display element is enlarged and projected using a plurality of reflecting mirrors. In these projection optical systems, an intermediate image is formed between the primary image and the object surface to be projected, so that it is impossible to achieve the constituent optical elements with only two reflecting mirrors. Furthermore, an optical system for forming an intermediate image and further projecting the intermediate image in an enlarged manner is required, and the entire optical system is increased in size.

  In the present invention, the two reflecting surfaces are decentered with respect to the axial principal ray passing through the centers of the image plane, the exit pupil, and the object plane, so that the structure is small and simple. An object of the present invention is to provide a decentered optical system capable of projecting or capturing an image, an image projecting apparatus using the decentered optical system, and an image capturing apparatus using the decentered optical system.

  A decentered optical system according to an embodiment of the present invention includes a first reflecting member having a first reflecting surface directed toward the image plane in order from the image plane to the object plane, and facing the first reflecting surface. A second reflecting member having a second reflecting surface directed toward the object plane side, forming an exit pupil on the image plane side of the first reflecting surface, passing through the exit pupil center from the image plane, When the light beam up to the center of the object plane is an axial principal ray, the first reflection surface and the second reflection surface are each arranged eccentrically with respect to the axial principal ray.

Further, if the angle formed by the extension line of the axial principal ray at the center of the exit pupil and the object plane is α, the following expression (1) is satisfied.
50 ° ≦ α ≦ 120 ° (1)

Further, when the angle of the axial principal ray between the first reflecting surface and the second reflecting surface with respect to the first reflecting surface is β, the following expression (2) is satisfied.
10 ° ≦ β ≦ 50 ° (2)

  Further, at least one of the first reflecting surface and the second reflecting surface is a surface reflecting surface.

  Further, at least one of the first reflecting surface and the second reflecting surface is a back surface reflecting surface.

  The center of at least one of the first reflecting surface and the second reflecting surface is deviated from the visual axis of the observer.

  In addition, at least one of the first reflecting surface and the second reflecting surface is a rotationally asymmetric surface.

  In addition, at least one of the first reflecting surface and the second reflecting surface is a free-form surface.

  Further, at least one of the first reflecting surface and the second reflecting surface is a rotationally symmetric surface.

  An image projection apparatus according to an embodiment of the present invention includes the decentration optical system and an image display element that is disposed on the object plane and displays an image, and the image displayed on the image display element is Reflected by the second reflecting surface, reflected by the first reflecting surface, passes through the exit pupil, and is enlarged and projected onto the image surface without forming an intermediate image.

  The decentered optical system switches between a state of projecting a real image and a state of projecting a virtual image by changing the imaging distance.

  The center of the exit pupil is the origin, the direction of the axial principal ray from the center of the exit pupil toward the first reflecting surface is the positive direction of the Z axis, and the axial principal ray is orthogonal to the Z axis. The direction in which the line projected on the surface to be projected is from the origin to the object plane is defined as the negative direction of the Y axis, the axis perpendicular to the Z axis and the Y axis, and the axis forming the right-handed orthogonal coordinate system is defined as the X axis. Conditional expression (3) and conditional expression (4) are satisfied.

0.1 ≦ 2fx / DLx ≦ 10 (3)
0.1 ≦ 2fy / DLy ≦ 8 (4)
However,
fx is the focal length in the XZ plane,
DLx is the length in the XZ plane of the image display element,
fy is the focal length in the YZ plane,
DLy is the length in the YZ plane of the image display element,
It is.

  In addition, an aperture stop is provided that can be moved to a position of the exit pupil or a predetermined position facing the first reflecting surface.

  In addition, a first holding unit that holds the image display element, a second holding unit that holds the first reflecting member movably with respect to the image display element, and the second reflection with respect to the image display element. A holding member having a third holding portion that holds the member in a movable manner.

  Further, the second holding unit stores the first reflecting member so as to overlap the image display element, and a projection state in which an image displayed on the image display element is projected onto the image plane. The third holding unit stores the second reflecting member so as to overlap the image display element, and a projection state in which an image displayed on the image display element is projected. Switch to and hold.

  In addition, a virtual path for the image of the image display element is projected by changing the optical path length from the position of the exit pupil to the image display element.

  The second holding unit moves the first reflecting member with respect to the image display element, and the third holding unit moves the second reflecting member with respect to the image display element. Project.

  Further, the first reflecting member and the second reflecting member move relatively.

  Further, by moving the image display element, a virtual image with respect to the image of the image display element is projected.

  The first reflecting member has a transmittance greater than zero.

  The first reflecting member has a reflectance of 10% or more.

  The first reflecting member is a half mirror.

  The decentered optical system has a transmittance of 5% or more with respect to external light.

  In addition, the first reflecting member includes a transmission surface that faces the second reflection member, and the first reflection surface that is disposed on the opposite side of the transmission surface with respect to the second reflection member. The transmission surface and the first reflection surface have the same shape.

  The image display element is a reflective liquid crystal or a transflective liquid crystal, and includes an illumination unit that illuminates the image display element.

  The illumination unit includes a polarization beam splitter.

  The illumination unit includes a diffractive optical element.

  An image pickup apparatus according to an embodiment of the present invention includes the decentered optical system, an image pickup element that is arranged on the image plane and picks up an image, and a predetermined position facing the position of the exit pupil or the first reflecting surface. An aperture stop serving as an entrance pupil that is movably installed at the position, and the image of the object plane passes through the aperture stop, is reflected by the first reflecting surface, and is reflected by the second reflecting surface. The image is picked up by the image pickup device.

  According to the decentered optical system which is an embodiment of the present invention, the two reflecting surfaces are decentered with respect to the axial principal ray passing through the respective centers of the image plane, the exit pupil, and the object plane, An object of the present invention is to provide a decentered optical system capable of projecting or capturing an image while having a small and simple structure.

1 is a cross-sectional view of an image projection apparatus using a decentered optical system according to an embodiment of the present invention. It is a figure which shows the coordinate system of the decentration optical system which concerns on one Embodiment of this invention. It is a figure which shows the positional relationship of the decentering optical system which concerns on one Embodiment of this invention, an image surface, an object surface, and an exit pupil. It is a figure which shows the projection state of the image projector which concerns on one Embodiment of this invention. It is a figure which shows the accommodation state of the image projector which concerns on one Embodiment of this invention. It is a figure which shows the movement state of the image projector which concerns on one Embodiment of this invention. It is a figure which shows the incident optical path of external light with the see-through function which concerns on one Embodiment of this invention. It is a figure which shows the image projector provided with the illumination part which concerns on one Embodiment of this invention. It is a figure which shows Example 1 which used the decentration optical system for the image projector. It is a figure which shows Example 2 which used the decentration optical system for the image projector. It is a figure which shows Example 2 using the decentration optical system for the image projection apparatus which projects a virtual image. It is a figure which shows Example 2 using the decentration optical system for the image projector which projects a real image. It is a figure which shows the image projector which projects the real image of Example 2. FIG. It is a figure which shows Example 3 which used the decentration optical system for the image projector. It is a figure which shows Example 3 using the decentration optical system for the image projection apparatus which projects a virtual image. It is a figure which shows Example 3 using the decentration optical system for the image projector which projects a real image. It is a figure which shows the distortion map at the time of projecting using the decentration optical system which concerns on one Embodiment of this invention for an image projector. It is a figure which shows the spot diagram at the time of projecting using the eccentric optical system which concerns on one Embodiment of this invention for an image projector.

  A decentering optical system according to an embodiment of the present invention, an image projection apparatus using the decentering optical system, and an image pickup apparatus using the decentering optical system will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view of an image projection apparatus using a decentered optical system according to an embodiment of the present invention. FIG. 2 is a diagram showing a coordinate system of a decentered optical system according to an embodiment of the present invention.

  When the decentering optical system 2 according to an embodiment of the present invention is used as an image projection apparatus for design convenience, the image plane ([0163] to [0165] Examples 1 to 1) as a projection plane is used. In the configuration parameters of Example 3, the description will be made by back ray tracing from the object plane) to the object plane that is the original image (the image plane in the configuration parameters of Embodiments 1 to 3 of [0163] to [0165]). Further, when used as an image capturing device, description will be made by forward ray tracing.

  When used as an image projection device, the first reflecting member 21 having the first reflecting surface 21a facing the image surface 11 side in order from the image surface 11 to the object surface 12, and the first reflecting surface 21a are opposed to each other. A second reflecting member 22 having a second reflecting surface 22a directed toward the object plane side, and forming an exit pupil 13 on the image surface 11 side of the first reflecting surface 21a, from the image surface 11 to the exit pupil 13 The first reflecting surface 21a and the second reflecting surface 22a are each arranged eccentrically with respect to the axial principal ray Lc, when a light ray passing through the center of the object surface 12 and reaching the center of the object plane 12 is defined as the axial principal ray Lc. .

  Here, the merit of configuring with such a decentered optical system 2 will be described.

  A refractive optical element such as a lens can be given power only by giving a curvature to its boundary surface. For this reason, when light rays are refracted at the boundary surface of the lens, the occurrence of chromatic aberration due to the wavelength dispersion characteristics of the refractive optical element is inevitable. As a result, another refractive optical element is generally added for the purpose of correcting chromatic aberration.

  On the other hand, a reflective optical element such as a mirror does not pass through the medium even if its reflecting surface has power, so in principle there is no chromatic aberration, and another optical element is used for the purpose of correcting chromatic aberration. There is no need to add. Therefore, the optical system using the reflective optical element can reduce the number of constituent elements of the optical element from the viewpoint of chromatic aberration correction, compared to the optical system using the refractive optical element.

  At the same time, since the reflection optical system using the reflection optical element folds the optical path, the optical system itself can be made smaller than the refractive optical system. Moreover, since the reflecting surface has a higher eccentricity error sensitivity than the refracting surface, high accuracy is required for assembly adjustment.

  In the reflection optical system having such a configuration, a rotationally asymmetric curved surface is formed that gives optical power to the two reflecting surfaces of the first mirror and the second mirror and corrects decentration aberrations. It is possible to correct aberrations well. By adopting such a basic configuration, the number of optical elements is small compared to an optical system using a refracting optical system or a rotationally symmetric relay optical system, and a compact image display device with good performance from the center to the periphery. Can be obtained.

  Here, when the light ray that passes through the center of the exit pupil 13 and reaches the center of the display surface of the image display element 3 is set as the axial principal ray Lc in reverse ray tracing, at least one reflection surface of the reflection surface is on the axis. If it is not decentered with respect to the principal ray Lc, the incident ray and the reflected ray of the axial principal ray Lc take the same optical path, and the axial principal ray Lc is blocked in the optical system. As a result, an image is formed only with a light beam whose central portion is shielded from light, and the center becomes dark or no image is formed at the center. It is also possible to decenter the reflecting surface with power with respect to the axial principal ray Lc.

  In addition, it is preferable that at least one of the first reflecting surface 21a and the second reflecting surface 22a is a surface reflecting surface.

  In the present embodiment, the second reflecting surface 22a is a surface reflecting surface. Since the second reflecting surface 22a is a surface reflecting surface, the light reaches the observer's eyeball without passing through a medium other than air, so that no chromatic aberration occurs in the optical system.

  The first reflecting surface 21a may be a surface reflecting surface.

  In addition, at least one of the first reflecting surface 21a and the second reflecting surface 22a of the present embodiment is preferably a back surface reflecting surface.

  In this embodiment, the 1st reflective surface 21a was made into the back surface reflective surface. By making the first reflecting surface 21a back-surface reflected, the first reflecting surface 21b is reflected in the optical medium sandwiched between the incident exit surface 21b of the first reflecting member 21 and the first reflecting surface 21a. The power φ of 21a is φ = n / r, where r is the curvature radius of the surface and n is the refractive index of the medium. For example, in the case of an optical plastic or the like, since n = 1.5, the power is 1.5 times that of surface reflection. Therefore, since the radius of curvature of the reflecting surface can be designed to be larger than that of the surface reflection, it is possible to suppress the aberration generated on this surface to be small.

  Furthermore, since the refraction action of the incident light exit surface 21b and the reflection action of the first reflection surface 21a are received, a large aberration correction effect is obtained as compared with the surface reflection. Therefore, it is possible to present a clear image with a well-corrected aberration to the observer.

  The second reflection surface 22a may be a back surface reflection surface.

  Further, it is preferable that the center of at least one of the first reflecting surface 21a and the second reflecting surface 22a is deviated from the visual axis of the observer.

If the reflecting surface with power is decentered, it will not be a coaxial optical system. In such a non-coaxial optical system, that is, a decentered optical system, an asymmetrical aberration due to decentration that does not occur in a normal optical system, that is, decentration aberration occurs. In order to correct the decentration aberration, it is desirable for the correction of the asymmetric aberration that the reflecting surface of the mirror, which is a decentered optical system, has asymmetry. Therefore, the local coordinate origin, which is the center point of the reflecting surface, does not coincide with the observer's visual axis, so that the reflecting surface has an asymmetry effect. With such a configuration, it becomes easy to correct asymmetric decentration aberrations.

  In addition, at least one of the first reflecting surface 21a and the second reflecting surface 22a is preferably a rotationally asymmetric surface.

  In order to correct asymmetrical aberrations such as decentration aberrations, it is desirable that the reflecting surface, which is a decentered optical system, has asymmetry. Therefore, it is realizable by making a reflective surface into a non-rotation symmetrical surface.

  The coordinate system and rotationally asymmetric surface used in this embodiment will be described.

  The optical axis defined by the straight line until the axial principal ray intersects the first reflecting surface 21a of the decentered optical system 2 is defined as the Z axis, and is orthogonal to the Z axis and is used for each surface constituting the optical system. The axis in the eccentric plane is defined as the Y axis, and the axis that is orthogonal to the optical axis and that is orthogonal to the Y axis, that is, the axis that extends from the front to the back in FIG. The ray tracing direction will be described by the backward ray tracing from the exit pupil 13 toward the image display element 3 as described above.

  In general, in a lens system composed only of spherical lenses, the spherical aberration generated by the spherical surface, coma aberration, curvature of field, and other aberrations are corrected with respect to each other to reduce aberrations as a whole. ing.

  On the other hand, a rotationally symmetric aspherical surface or the like is used to satisfactorily correct aberrations with a small number of surfaces. This is to reduce various aberrations that occur in a single spherical surface. However, in a decentered optical system, it is impossible to correct rotationally asymmetric decentering aberration caused by the decentering of the optical surface with a rotationally symmetric optical system. This decentration aberration includes asymmetric distortion, curvature of field, astigmatism occurring on the axis, and coma.

  First, rotationally asymmetric field curvature will be described. For example, a light beam incident on a concave mirror decentered from an object point at infinity is reflected and imaged by hitting the concave mirror, but after the light beam hits the concave mirror, the back focal length to the image plane is the light beam when the image plane side is air. It becomes half the radius of curvature of the part hit. The light reflected by the eccentric concave surface forms an image plane inclined with respect to the axial principal ray. Thus, it is impossible to correct rotationally asymmetric field curvature with a rotationally symmetric optical system.

  In order to correct this tilted field curvature with the concave mirror itself that is the source of the tilt, it is necessary to configure the concave mirror with a rotationally asymmetric surface. In the present embodiment, the correction can be made by increasing the curvature, that is, the refractive power in the positive direction of the Y axis and decreasing the curvature, that is, the refractive power in the negative direction of the Y axis. Further, by arranging a rotationally asymmetric surface having the same effect as the above configuration in the optical system separately from the concave mirror, a flat image surface can be obtained with a small number of components. In addition, the rotationally asymmetric surface preferably has a rotationally asymmetric surface shape that does not have a rotationally symmetric axis both in and out of the surface.

  Next, rotationally asymmetric astigmatism will be described. Similar to the above description, the astigmatism is generated for the axial ray in the concave mirror arranged eccentrically. In order to correct this astigmatism, it is possible to appropriately change the curvature in the X-axis direction and the curvature in the Y-axis direction of the rotationally asymmetric surface as in the above description.

  Further, rotationally asymmetric coma will be described. As in the above description, coma aberration occurs with respect to the axial principal ray in the concave mirror arranged eccentrically. In order to correct this coma, it is possible to change the inclination of the surface as it moves away from the origin of the X axis of the rotationally asymmetric surface and to change the inclination of the surface appropriately depending on whether the Y axis is positive or negative. In the imaging optical system of the present invention, it is possible to adopt a configuration in which at least one surface having the reflecting action described above is decentered with respect to the axial principal ray and has a rotationally asymmetric surface shape and power. By adopting such a configuration, it becomes possible to correct decentration aberration generated by giving power to the reflecting surface by the surface itself.

  Moreover, it is preferable that the reflection surface as a rotationally asymmetric surface used in the present embodiment is a plane-symmetric free-form surface having only one plane of symmetry.

  The shape of the free-form surface FFS used in the present embodiment is defined by the following equation (a). Note that Z in the definition formula is the Z axis of the free-form surface FFS. The coefficient term for which no data is described is zero.

Z = cr ² / [1 + √ {1- (1 + k) c ² r ² }]
₆₆
+ Σ C _j X ^m Y ⁿ (a)
^{j = 2}
Here, the first term of the equation (a) is a spherical term, and the second term is a free-form surface term.
In the spherical term,
c: curvature of vertex k: conic constant (conical constant)
r = √ (X ² + Y ² )
It is.

The free-form surface term is
₆₆
ΣC _j X ^m Y ^{n
j = 2}
= C ₂ X + C ₃ Y
+ C ₄ X ² + C ₅ XY + C ₆ Y ²
+ C ₇ X ³ + C ₈ X ² Y + C ₉ XY ² + C ₁₀ Y ³
+ C ₁₁ X ⁴ + C ₁₂ X ³ Y + C ₁₃ X ² Y ² + C ₁₄ XY ³ + C ₁₅ Y ⁴
+ C ₁₆ X ⁵ + C ₁₇ X ⁴ Y + C ₁₈ X ³ Y ² + C ₁₉ X ² Y ³ + C ₂₀ XY ⁴
+ C ₂₁ Y ⁵
+ C ₂₂ X ⁶ + C ₂₃ X ⁵ Y + C ₂₄ X ⁴ Y ² + C ₂₅ X ³ Y ³ + C ₂₆ X ² Y ⁴
+ C ₂₇ XY ⁵ + C ₂₈ Y ⁶
+ C ₂₉ X ⁷ + C ₃₀ X ⁶ Y + C ₃₁ X ⁵ Y ² + C ₃₂ X ⁴ Y ³ + C ₃₃ X ³ Y ⁴
+ C ₃₄ X ² Y ⁵ + C ₃₅ XY ⁶ + C ₃₆ Y ⁷
・ ・ ・ ・ ・ ・

However, Cj (j is an integer of 2 or more) is a coefficient. In general, the free-form surface does not have a symmetric plane in both the XZ plane and the YZ plane, but in this embodiment, by setting all odd-order terms of X to 0, the YZ plane Is a free-form surface having only one plane of symmetry parallel to the. For example, in the above defining equation _{(a), C 2, C} 5, C 7, C 9, C 12, C 14, C 16, C 18, C 20, C 23, C 25, C 27, C 29, This is possible by setting the coefficient of each term of C ₃₁ , C ₃₃ , C ₃₅ .

Further, by setting all odd-numbered terms of Y to 0, a free-form surface having only one symmetry plane parallel to the XZ plane is obtained. For example, in the above definition formula, C ₃ , C ₅ , C ₈ , C ₁₀ , C ₁₂ , C ₁₄ , C ₁₇ , C ₁₉ , C ₂₁ , C ₂₃ , C ₂₅ , C ₂₇ , C ₃₀ , C ₃₂ , This is possible by setting the coefficient of each term of C ₃₄ , C ₃₆ .

  Further, any one of the directions of the symmetry plane is set as a symmetry plane, and the eccentricity in the corresponding direction, for example, the eccentric direction of the optical system with respect to the symmetry plane parallel to the YZ plane is in the Y-axis direction, For the symmetry plane parallel to the Z plane, the decentering direction of the optical system is set to the X-axis direction, so that it is possible to improve the manufacturability while effectively correcting the rotationally asymmetric aberration caused by the decentering. It becomes.

  The definition formula (a) is shown as an example as described above, and the free-form surface of the present invention uses a rotationally asymmetric surface to correct rotationally asymmetric aberration caused by decentration. At the same time, the feature is that the manufacturability is also improved, and it goes without saying that the same effect can be obtained for any other defining formula.

  Further, at least one of the first reflecting surface 21a and the second reflecting surface 22a may be a rotationally symmetric surface.

  If the reflecting surface is a rotationally symmetric surface, the optical element can be processed by a rotary motion using a lathe or the like, so that it can be processed with high accuracy and at a relatively low cost. For asymmetric decentration aberrations, a correction effect is provided by shifting or tilting the reflecting surface. That is, a reflective surface with high surface accuracy can be manufactured at low cost.

  Further, it is preferable that the decentering optical system 2 satisfies the following expression (1), where α is an angle formed by the extension line of the axial principal ray Lc at the center of the exit pupil 13 and the object plane 12.

    50 ° ≦ α ≦ 120 ° (1)

  FIG. 3 is a diagram showing a positional relationship between the decentering optical system 2 and the image plane 11, the object plane 12, and the exit pupil 13 according to an embodiment of the present invention.

  Conditional expression (1) indicates that the image of the image display element 3 arranged on the object plane 12 is projected onto the eyeball at the position of the exit pupil 13 with a wide angle of view by one reflecting mirror, and the image display. This is a condition for determining the relative positional relationship of the elements.

  When the value goes below the lower limit of conditional expression (1), direct light from the display surface of the image display element reaches the eyeball, which makes it difficult to observe through the decentered optical system. If the value exceeds the upper limit of conditional expression (1), the image display element and the face of the observer interfere with each other, which makes it difficult to arrange.

  Further, the decentering optical system 2 satisfies the following expression (2), where β is the angle of the axial principal ray Lc between the first reflecting surface 21a and the second reflecting surface 22a with respect to the first reflecting surface 21a. preferable.

    10 ° ≦ β ≦ 50 ° (2)

  As shown in FIG. 3, the conditional expression (2) is an observer for projecting an image of the image display element 3 arranged on the object plane 12 onto an eyeball at the position of the exit pupil 13 with a wide angle of view by one reflection mirror. And a condition for determining the relative positional relationship between the observation optical system and the image display element 3.

  When the value is smaller than the lower limit of the conditional expression (2), the image display element 3 and the face of the observer interfere with each other, which makes it difficult to arrange. When the value exceeds the upper limit of conditional expression (2), the decentration aberration generated in the decentration optical system 2 becomes too large to be corrected, and it becomes difficult to present a clear observation image.

  Furthermore, the image projection apparatus 1 of the present embodiment includes a decentering optical system 2 and an image display element 3 that is arranged on the object plane 12 and displays an image. An image displayed on the image display element 3 is Reflected by the two reflecting surfaces 22, reflected by the first reflecting surface 21, passes through the exit pupil 13, and is enlarged and projected onto the image surface 11 without forming an intermediate image.

  By configuring the image projecting device in this way, it is possible to project an image with less aberration while having a small and simple structure.

  In the coordinate system described with reference to FIG. 2, it is preferable that the following conditional expressions (3) and (4) are satisfied.

0.1 ≦ 2fx / DLx ≦ 10 (3)
0.1 ≦ 2fy / DLy ≦ 8 (4)
However,
fx is the focal length in the XZ plane,
DLx is the length in the XZ plane of the image display element,
fy is the focal length in the YZ plane,
DLy is the length in the YZ plane of the image display element,
It is.

  Conditional expression (3) and conditional expression (4) indicate the focal length of the decentering optical system 2 and the image display element 3 necessary for projecting the image of the image display element 3 onto the eyeball with a wide angle of view by one reflection mirror. It is a conditional expression that determines the size relationship.

  If the lower limit of conditional expression (3) and conditional expression (4) is exceeded, the image display element becomes too large with respect to the focal length of the optical system, making it difficult to correct peripheral aberrations and presenting the observed image clearly. Difficult to do. If the upper limit of conditional expression (3) and conditional expression (4) is exceeded, the focal length becomes longer with respect to the image element, so that the enlargement ratio is small and observation with a sufficient angle of view is not possible.

  In addition, it is preferable to include an aperture stop S that is movably installed at the position of the exit pupil 13 or a predetermined position facing the first reflecting surface 21a.

  For example, when a real image is projected like a projector, an aperture stop S is provided in the vicinity of the position of the exit pupil 13 of the decentration optical system 2, so that the diameter of the exit pupil 13 set at the time of designing the decentration optical system 2. Will be projected. Without this aperture stop S, projection is performed with an exit pupil 13 that is greater than or equal to the design value, which may reduce the resolution of the projected image. Further, by making the aperture stop S variable, it is possible to adjust brightness and resolution.

  In addition, the image projection apparatus 1 includes a first holding unit 41 that holds the image display element 3, a second holding unit 42 that holds the first reflecting member 21 movably with respect to the image display element 3, and an image display element. It is preferable to include a holding member 4 having a third holding portion 43 that holds the second reflecting member 22 movably with respect to the third holding member 43.

  Further, the second holding unit 42 has a projection state in which the image displayed on the image display element 3 is projected on the image plane 11 and a storage state in which the first holding member 21 is stored so as to overlap the image display element 3. The third holding unit 43 stores the second reflecting member 22 so as to overlap the projection state in which the image displayed on the image display element 3 is projected and the image display element 3. It is preferable to hold the switchable state.

  FIG. 4 is a diagram showing a projection state of the image projection apparatus 1 according to an embodiment of the present invention. FIG. 5 is a diagram illustrating a storage state of the image projection apparatus 1 according to an embodiment of the present invention.

  As shown in FIG. 4, in the projection state of the image projector 1, the second holding part 42 of the holding member 4 sets the first reflecting member 21 to a predetermined reflecting position, and the third holding part 43 is the second reflecting member. 22 is set to a predetermined reflection position.

  Further, as shown in FIG. 5, in the storage state of the image projection apparatus 1, the second holding portion 42 of the holding member 4 is set at a predetermined storage position such that the first reflecting member 21 overlaps the second reflecting member 22. The third holding portion 43 is set at a predetermined storage position such that the second reflecting member 22 overlaps the image display element 3.

  The structure of the second holding portion 42 is that the first reflecting member 21 is supported and can be rotated with respect to a shaft member (not shown), and the rotation is stopped at the reflection position in the observation state and the storage position in the storage state. It is desirable to provide a lock mechanism that can temporarily fix the position such as a latch so as to be fixed.

  The third holding portion 43 has a structure that supports the second reflecting member 22 and can be rotated with respect to a shaft member (not shown) as in the case of the second holding portion 42. It is desirable to provide a lock mechanism that can temporarily fix the position such as a latch so that the rotation is stopped and fixed at the storage position in the storage state.

  By holding with such a holding member 4, when the first reflecting member 21 and the second reflecting member 22 are in the reflection position in the observation state, the observer can observe the image on the image display element 3. Thus, when the first reflection member 21 and the second reflection member 22 are in the storage position in the storage state, it can be folded into a compact shape. Therefore, it is convenient to carry the image projector 1.

  In addition, it is preferable to project a virtual image by changing the optical path length from the position of the exit pupil 13 to the image display element 3.

  FIG. 6 is a diagram illustrating a moving state of the image projector 1 according to the embodiment of the present invention. FIG. 7 is a diagram showing a virtual image observation state by the image projection apparatus 1 according to an embodiment of the present invention.

  In FIG. 6, what is indicated by a solid line is the decentered optical system 2 in a state of projecting a real image. Also, a broken line shows the decentered optical system 2 in a state of projecting a virtual image.

  In order to project a virtual image from a real image projection state, the distance from the position of the exit pupil 13 to the image display element 3 is shortened in order to change the imaging distance of the decentered optical system 2 to minus. By such a simple change, a projector that forms a real image can be switched to an observation optical device that projects a virtual image onto an eyeball E as shown in FIG.

  As shown in FIG. 7, the external light Lo from the outside is incident from the outer surface of the surface having substantially the same shape as the reflecting surface of the first reflecting member 21, and the inner reflecting surface is a half mirror surface, The external light Lo enters the eyeball E of the observer whose pupil is located at the position of the exit pupil 13 and observes the external world. The first surface and the second surface of the first reflecting member 21 are similar free-form curved surfaces, and can be observed with almost no aberration and magnification of 1 × in almost all angles of view with a horizontal angle of view of 35 degrees. .

  Further, the second holding unit 42 moves the first reflecting member 21 with respect to the image display element 3, and the third holding unit 43 moves the second reflecting member 22 with respect to the image display element 3, thereby generating a virtual image. It is preferable to project.

  By moving the reflecting members 21 and 22 such as two mirrors relative to the image display element 3, it becomes possible to project a virtual image. By changing the positions of the two reflecting members 21 and 22 relative to the image display element 3, changing the power of the decentering optical system 2, and changing the imaging distance to minus, a virtual image is projected. Therefore, when the pupil of the observer's eyeball E is positioned near the position of the exit pupil 13 of the decentration optical system 2, an enlarged virtual image can be observed.

  Moreover, it is preferable that the 1st reflection member 21 and the 2nd reflection member 22 move relatively.

  It is desirable that the relative positional relationship between the reflecting members 21 and 22 such as two mirrors be variable. Changing the effective range of reflection of the two reflecting members 21 and 22 or changing the distance between the two reflecting members 21 and 22 to change the power of the decentered optical system 2 changes the short imaging distance. In this case, it is possible to maintain high imaging performance. Therefore, even when a virtual image is observed as a near-eye display, it is possible to present a good image with little aberration.

  In addition, it is good also as a structure which projects a virtual image by moving the image display element 3. FIG. It is possible to project a virtual image by simple and stable movement.

  The first reflecting member 21 preferably has a transmittance greater than zero.

  Since the surface on the opposite side of the observer has a transmittance greater than 0, the external light Lo can reach the eyeball E, so that the observer can observe the external world. Since the outside world can be observed through the first reflecting member 21, it is possible to superimpose the outside world image and the observation image of the image display element 3 for observation.

  Moreover, it is preferable that the 1st reflection member 21 has a reflectance of 10% or more.

  If the reflectance of the first reflecting member 21 is 10% or more, the observer can observe the image displayed on the image display element 3.

  Moreover, it is preferable that the 1st reflection member 21 is a half mirror.

For example, the first reflecting member 21 is made of a transparent member such as optical plastic or optical glass, and a predetermined metal thin film, dielectric film or the like is formed so that the reflecting surface has a finite value of reflectance and transmittance. Thus, a half mirror that partially reflects and transmits incident light can be obtained. in this way,
Since the outside world can be observed through the first reflecting member 21, it is possible to superimpose the outside world image and the observation image of the image display element 3 for observation.

  Moreover, it is preferable that the decentration optical system 2 has a transmittance of 5% or more with respect to external light.

  If the transmittance of the decentered optical system 2 is 5% or more, the observer can observe the outside through the decentered optical system 2.

  The first reflecting member 21 includes a transmissive surface 21b that faces the second reflective member 22, and a first reflective surface 21a that is disposed on the opposite side of the transmissive surface 21b from the second reflective member 22. The transmission surface 21b and the first reflection surface 21a preferably have the same shape.

  By making the incident and exit transmitting surface 21b of the first reflecting member 21 and the first reflecting surface 21a on the back surface thereof the same, it is possible to realize a state where there is no power with respect to external light. Moreover, the state which has almost no power with respect to external light can be implement | achieved by making it substantially the same. A see-through effect or a superimpose effect of superimposing an electronic image on an external image can be obtained.

  The image display element 3 is a reflective liquid crystal or a transflective liquid crystal, and preferably includes an illumination unit 5 that illuminates the image display element 3.

  FIG. 8 is a diagram illustrating the image projection apparatus 1 including the illumination unit 5 according to an embodiment of the present invention.

  By using reflective liquid crystal or transflective liquid crystal on the display surface of the image display element 3, illumination light can be irradiated from the front of the display surface. By making the numerical aperture of the illumination light close to the numerical aperture of the projection light, the light utilization efficiency is increased, the projected image becomes bright even with a small amount of light, and a projection image that is easy to see for the observer is presented Can do.

  In the example illustrated in FIG. 8, the triangular prism 6 is provided between the image display element 3 and the second reflecting member 22, and the illumination unit 5 is provided below the bottom of the triangular prism 6. The light emitted from the light source 5 is linearly polarized light by a polarizing element (not shown). For simplicity, it is assumed here to be S polarized light. Further, although not shown, the light beam is a substantially parallel light beam by a Fresnel lens or the like. The light enters from the bottom side of the triangular prism 6, is totally reflected on the surface on the image display element 3 side, and is reflected on the surface on the second reflecting member 22 side. This surface is a polarizing beam splitter using thin film deposition or film bonding, and the S-polarized light of the light source is reflected with a high reflectance. The reflected light is emitted from the triangular prism 6 and illuminates the image display element 3. The light modulated by the image display element 3 becomes P-polarized light, which becomes an optical path that passes through the polarizing beam splitter above the triangular prism 6 and enters the observation optical system.

  Moreover, it is preferable that the illumination part 5 has a polarization beam splitter.

The illumination unit 5 receives illumination light from the front of the display surface of the image display element 3, and the illumination light is polarized light in which light is polarized in the direction reflected by the polarization beam splitter. The light reflected by the polarization beam splitter is When the light is reflected by the liquid crystal surface, the polarization direction is rotated by 90 degrees, and is incident on the polarization beam splitter again, the polarized light is transmitted in the vibration direction and introduced into the decentered optical system 2. Therefore, after the illumination light becomes polarized light, it is illuminated and projected theoretically without loss.

  Moreover, it is preferable that the illumination part 5 has a diffractive optical element.

  The illumination unit 5 receives illumination light from the front of the display surface of the image display element 3, and the diffractive optical element is designed to have a reflecting action with respect to the incident angle of the illumination light. The projection light reflected from the display surface and emitted from the image display element is designed and made to have a transmission effect. By disposing the diffractive optical element having such an action at an angle in front of the display surface, it is possible to illuminate with high efficiency regardless of the polarization state.

  Furthermore, the image pickup apparatus of the present embodiment includes the decentered optical system 2, the image pickup element that is arranged on the image plane 3 and picks up an image, and the position of the exit pupil 13 or the predetermined position facing the first reflecting surface 21a. The image of the object plane 11 passes through the entrance pupil 13, is reflected by the first reflecting surface 21a, is reflected by the second reflecting surface 22a, and is reflected on the image pickup device. Imaged.

  By configuring the image capturing apparatus in this way, it is possible to capture an image with less aberration while having a small and simple structure.

  Next, each example according to an embodiment of the present invention will be described.

  FIG. 9 is a diagram illustrating Example 1 in which a decentered optical system is used in an image projection apparatus.

  The decentered optical system 2 of Example 1 has a first reflecting surface 21a that is directed from the image plane toward the object plane 12 in order from the image plane (not shown in FIG. 9 because the figure is small). A first reflecting member 21 and a second reflecting member 22 having a second reflecting surface 22a facing the first reflecting surface 21a and facing the object surface, and is emitted to the image surface side of the first reflecting surface 21a. When the light beam from the image plane passing through the center of the exit pupil 13 to the center of the object plane 12 is defined as an axial principal ray Lc, the first reflection surface 21a and the second reflection surface 22a are It is arranged eccentric with respect to the upper principal ray Lc.

  The first reflecting member 21 is a back reflecting mirror and has a first reflecting surface 21a and a transmitting surface 21b. The second reflecting member 22 is a surface reflecting mirror and has a second reflecting surface 22a.

  Ray tracing when the decentered optical system 2 is used in the image projection apparatus 1 will be described. The light beam emitted from the object surface 12 as the display surface of the image display element 3 is reflected by the second reflecting surface 22 a of the second reflecting member 22. The light beam reflected by the second reflecting member 22 enters from the transmitting surface 21b of the first reflecting member 21, is reflected by the first reflecting surface 21a, and exits from the transmitting surface 21b. The light beam emitted from the first reflecting member 21 passes through the exit pupil 13 and is imaged and projected on a screen or the like disposed on the image plane.

  The image display element 3 of Example 1 is assumed to have an aspect ratio of 2: 3 and a display area of 3.5 inches. The horizontal angle in the YZ plane and the vertical angle of view in the XZ plane are 29.3 ° and 19.6 °, respectively, and the exit pupil diameter is 12 mm.

  The decentering optical system 2 is used for the image projection apparatus 1 in which the image display element 3 is arranged on the object plane 12 and for the image imaging apparatus in which 12 is used as the image plane and the image imaging element is arranged in 3. There are cases.

  Ray tracing in the case where the decentering optical system 2 is used in an image pickup apparatus will be described. A light beam emitted from an object surface not shown in FIG. 9 passes through the entrance pupil 13 and enters the first reflecting member 21. In the first reflecting member 21, the light beam enters from the transmitting surface 21b, is reflected by the first reflecting surface 21a, and exits from the transmitting surface 21b. The light beam emitted from the first reflecting member 21 is reflected by the second reflecting surface 22 a of the second reflecting member 22. The light beam reflected by the second reflecting member 22 enters the image plane 12 and is imaged.

  FIG. 10 is a diagram illustrating a second embodiment in which a decentered optical system is used in an image projection apparatus. FIG. 11 is a diagram illustrating a second embodiment in which an eccentric optical system is used in an image projection apparatus that projects a virtual image in the optical system illustrated in FIG. 10. FIG. 12 is a diagram illustrating a second embodiment in which an eccentric optical system is used in an image projection apparatus that projects a real image in the optical system illustrated in FIG. 10. FIG. 13 is a diagram illustrating an entire image projection apparatus that projects a real image according to the second embodiment.

  The decentering optical system 2 of Example 2 is opposed to the first reflecting member 21 having the first reflecting surface 21a facing the image surface side in order from the image surface to the object surface 12, and the first reflecting surface 21a. A second reflecting member 22 having a second reflecting surface 22a directed toward the object plane side, the exit pupil 13 is formed on the image plane side of the first reflecting surface 21a, and the center of the exit pupil 13 from the image plane 11 , The first reflecting surface 21a and the second reflecting surface 22a are each arranged eccentrically with respect to the axial principal ray Lc.

  The first reflecting member 21 has a first reflecting surface 21a. The second reflecting member 22 has a second reflecting surface 22a. The 1st reflective surface 21a and the 2nd reflective surface 22a of Example 2 are free-form surface shapes.

  The position of the first reflecting member 21 and the second reflecting member 22 can be relatively changed. As shown in FIG. 10, by changing the position relatively, a case where a virtual image is projected as shown in FIG. 11 and a case where a real image is projected as shown in FIGS. 12 and 13 are selected. It becomes possible.

  Ray tracing when the decentered optical system 2 is used in an image projection apparatus will be described. The light beam emitted from the object surface 12 as the display surface of the image display element is reflected by the second reflection surface 22 a of the second reflection member 22. The light beam reflected by the second reflecting member 22 is reflected by the first reflecting surface 21 a of the first reflecting member 21. The light beam reflected by the first reflecting member 21 reaches the exit pupil 13.

  When a virtual image as shown in FIG. 11 is projected, it is possible to present an enlarged virtual image to the viewer by arranging the iris or eyeball center of the viewer near the exit pupil 13. When a real image as shown in FIGS. 12 and 13 is projected, the light beam passes through the exit pupil 13 and is projected onto a screen or the like disposed on the image plane.

  In this case, the image display element is assumed to have an aspect ratio of 2: 3 and a display area of 3.5 inches. When projecting a virtual image, the horizontal angle in the YZ plane and the vertical field angle in the XZ plane are 35.0 ° and 23.8 °, respectively, and the exit pupil diameter is 6 mm. The horizontal angle in the YZ plane and the vertical field angle in the XZ plane are 29.0 ° and 19.6 °, respectively, and the exit pupil diameter is 15 mm.

  The decentering optical system 2 is used for an image projection apparatus in which an image display element is arranged on the object plane 12 and a real image and a virtual image are projected, and in an image imaging apparatus in which an image imaging element is arranged on the image plane 12. There is.

  Ray tracing in the case where the decentering optical system 2 is used in an image pickup apparatus will be described. The light beam emitted from the object plane 11 passes through the entrance pupil 13 and enters the first reflecting member 21. In the first reflecting member 21, the light beam enters from the transmitting surface 21b, is reflected by the first reflecting surface 21a, and exits from the transmitting surface 21b. The light beam emitted from the first reflecting member 21 is reflected by the second reflecting surface 22 a of the second reflecting member 22. The light beam reflected by the second reflecting member 22 enters the image plane 12 and is imaged.

  FIG. 14 is a diagram illustrating Example 3 in which a decentered optical system is used in an image projection apparatus. FIG. 15 is a diagram illustrating Example 3 in which an eccentric optical system is used in an image projection apparatus that projects a virtual image. FIG. 16 is a diagram illustrating Example 3 in which an eccentric optical system is used in an image projection apparatus that projects a real image.

  The decentering optical system 2 of Example 3 is opposed to the first reflecting member 21 having the first reflecting surface 21a facing the image surface side in order from the image surface 11 to the object surface 12, and the first reflecting surface 21a. A second reflecting member 22 having a second reflecting surface 22a directed toward the image plane side, forming an exit pupil 13 on the image plane side of the first reflecting surface 21a, and from the image plane 11 to the exit pupil 13 When the light beam that passes through the center and reaches the center of the object plane 12 is the axial principal ray Lc, the first reflection surface 21a and the second reflection surface 22a are arranged eccentrically with respect to the axial principal ray Lc.

  The first reflecting member 21 has a first reflecting surface 21a. The second reflecting member 22 has a second reflecting surface 22a. The 1st reflective surface 21a and the 2nd reflective surface 22a of Example 2 are free-form surface shapes.

  The position of the first reflecting member 21 and the second reflecting member 22 can be relatively changed. As shown in FIG. 14, by changing the position relatively, it is possible to select a case where a virtual image is projected as shown in FIG. 15 or a case where a real image is projected as shown in FIG. It becomes.

  Ray tracing when the decentered optical system 2 is used in an image projection apparatus will be described. The light beam emitted from the object surface 12 as the display surface of the image display element is reflected by the second reflection surface 22 a of the second reflection member 22. The light beam reflected by the second reflecting member 22 is reflected by the first reflecting surface 21 a of the first reflecting member 21. The light beam reflected by the first reflecting member 21 reaches the exit pupil 13.

  When a virtual image as shown in FIG. 14 is projected, it is possible to present an enlarged virtual image to the viewer by arranging the iris or eyeball center of the viewer near the exit pupil 13. When a real image as shown in FIG. 15 is projected, the light beam passes through the exit pupil 13 and is projected onto a screen or the like disposed on the image plane.

  In this case, the image display element is assumed to have an aspect ratio of 2: 3 and a display area of 3.5 inches. When projecting a virtual image, the horizontal angle in the YZ plane and the vertical field angle in the XZ plane are 35.0 ° and 23.8 °, respectively, and the exit pupil diameter is 6 mm. The horizontal angle in the YZ plane and the vertical field angle in the XZ plane are 29.0 ° and 19.6 °, respectively, and the exit pupil diameter is 15 mm.

  The decentering optical system 2 is used in an image projection apparatus in which an image display element is arranged on the object plane 12 to project a real image and a virtual image, and an image pickup in which an image imaging element is arranged in 3 using 12 as an image plane. There are cases where it is used for a device.

  Ray tracing in the case where the decentering optical system 2 is used in an image pickup apparatus will be described. The light beam emitted from the object plane 11 passes through the entrance pupil 13 and enters the first reflecting member 21. In the first reflecting member 21, the light beam enters from the transmitting surface 21b, is reflected by the first reflecting surface 21a, and exits from the transmitting surface 21b. The light beam emitted from the first reflecting member 21 is reflected by the second reflecting surface 22 a of the second reflecting member 22. The light beam reflected by the second reflecting member 22 enters the image plane 12 and is imaged.

  The configuration parameters of the first to third embodiments are shown below.

  In each embodiment, each surface is decentered in the YZ plane, and the only symmetric surface of each rotationally asymmetric free-form surface is the YZ plane. For the eccentric surface, from the origin of the corresponding coordinate system, the amount of eccentricity of the surface top position of the surface (X-axis direction, Y-axis direction, Z-axis direction is X, Y, Z, respectively) and the center axis of the surface ( As for the free-form surface, inclination angles (α, β, γ (°), respectively) about the X axis, the Y axis, and the Z axis of the equation (a) are given. In this case, positive α and β mean counterclockwise rotation with respect to the positive direction of each axis, and positive γ means clockwise rotation with respect to the positive direction of the Z axis.

  In addition, a surface interval is given when a specific surface (including a virtual surface) and a subsequent surface among the optical action surfaces constituting the optical system of each embodiment constitute a coaxial optical system. After the eccentricity, it returns to the origin before the eccentricity and proceeds in the Z-axis direction given by the surface interval to be the origin of the next surface.

  In addition, the refractive index and Abbe number of the medium are given according to conventional methods. Further, the shape of the surface of the free curved surface used in the present invention is defined by the equation (a), and the Z axis of the defining equation becomes the axis of the free curved surface.

The symbol “e” indicates that the subsequent numerical value is a power exponent with 10 as the base. For example, “1.0e-5” means “1.0 × 10 ⁻⁵ ”.

Example 1
Projection optics surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ 2000.00
1 Diaphragm surface 0.00
2 FFS [1] 0.00 Eccentricity (1) 1.5 256 56.4
3 FFS [1] 0.00 Eccentricity (2) 1.5 256 56.4
4 FFS [1] 0.00 Eccentricity (1)
5 FFS [2] 0.00 Eccentricity (3)
6 ∞ 0.00 Eccentricity (4)
Image plane ∞ 0.00

FFS [1]
C4 -2.5766e-003 C6 -2.0435e-003 C8 2.8731e-006
C10 -7.9739e-006 C11 3.4572e-007 C13 -2.2244e-007
C15 4.3487e-008 C17 -2.8059e-008 C19 -6.4257e-009
C21 1.6737e-009

FFS [2]
C4 -2.7993e-003 C6 2.3620e-004 C8 4.0263e-005
C10 -1.0601e-005 C11 2.7088e-006 C13 -1.3654e-007
C15 -6.8551e-008 C17 -6.0725e-008 C19 -6.0832e-009
C21 1.2011e-009 C

Eccentric [1]
X 0.00 Y -4.96 Z 67.89
α 21.44 β 0.00 γ 0.00

Eccentric [2]
X 0.00 Y -2.96 Z 69.68
α 21.44 β 0.00 γ 0.00

Eccentric [3]
X 0.00 Y -75.00 Z 27.31
α 7.71 β 0.00 γ 0.00

Eccentric [4]
X 0.00 Y -73.16 Z 82.38
α -6.54 β 0.00 γ 0.00

Example 2
Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ -800.00
1 Diaphragm surface 0.00
2 FFS [1] 0.00 Eccentricity (1)
3 FFS [2] 0.00 Eccentricity (2)
4 ∞ 0.00 Eccentricity (3)
Image plane ∞ 0.00

FFS [1]
C4 -2.5525e-003 C6 -1.8406e-003 C8 -2.0524e-006
C10 -3.5796e-006 C11 -7.0945e-008 C13 1.1801e-007
C15 -8.4837e-008 C17 1.9863e-009 C19 -4.5831e-009
C21 2.2551e-009

FFS [2]
C4 -1.6201e-003 C6 -4.0531e-004 C8 -5.6132e-006
C10 3.3735e-006 C11 -1.8844e-007 C13 -7.8778e-008
C15 -2.0300e-007 C17 2.4500e-010 C19 1.7835e-009
C21 2.1645e-009

Eccentric [1]
X 0.00 Y -7.35 Z 67.42
α 24.32 β 0.00 γ 0.00

Eccentric [2]
X 0.00 Y -68.37 Z 30.81
α 9.39 β 0.00 γ 0.00

Eccentric [3]
X 0.00 Y -69.92 Z 64.26
α -22.00 β 0.00 γ 0.00

Virtual image projection Real image projection Exit pupil diameter 6 15
Surface number Object surface -800 2000

Surface number 3 Eccentric Y -68.37105 -68.37105
Surface number 3 Eccentric Z 30.81394 27.36526
Surface number 3 Eccentric α 9.39432 7.77886

Surface number 4 Eccentric Y -69.91578 -90.00619
Surface number 4 Eccentric Z 64.25846 81.54933
Surface number 4 Eccentric α -22 -22

Example 3
Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ -800.00
1 Diaphragm surface 0.00
2 FFS [1] 0.00 Eccentricity (1)
3 FFS [2] 0.00 Eccentricity (2)
4 ∞ 0.00 Eccentricity (3)
Image plane ∞ 0.00

FFS [1]
C4 -2.5303e-003 C6 -1.7640e-003 C8 -3.3451e-006
C10 -8.7746e-006 C11 -1.2080e-007 C13 2.6813e-007
C15 7.6133e-008 C17 7.3669e-009 C19 -1.4412e-008
C21 6.8840e-010

FFS [2]
C4 -1.3756e-003 C6 -2.0607e-004 C8 -1.2488e-005
C10 -1.6146e-005 C11 -5.3829e-007 C13 4.6677e-007
C15 2.7885e-007 C17 1.2728e-008 C19 -1.0300e-008
C21 -1.0543e-009

Eccentric [1]
X 0.00 Y -9.24 Z 65.03
α 24.01 β 0.00 γ 0.00

Eccentric [2]
X 0.00 Y -65.19 Z 29.86
α 10.05 β 0.00 γ 0.00

Eccentric [3]
X 0.00 Y -68.82 Z 67.41
α -10.00 β 0.00 γ 0.00

Virtual image projection Real image projection Exit pupil diameter 6 15
Surface number Object surface -800 2000

Surface number 4 Eccentric Y -65.18976 -83.18976
Surface number 3 Eccentric Z 29.86106 19.86106
Surface number 3 Eccentric α 10.05029 10.05029

Surface number 4 Eccentric Y -68.82188 -87.1885
Surface number 4 Eccentric Z 67.40844 63.58981
Surface number 4 Eccentric α -10 -10

  Regarding Examples 1 to 3, the values of conditional expressions (1) to (4) are shown below.

Example 1 (real image) Example 2 (virtual image) Example 2 (real image)
α 70 80.729 77.124
β 22.733 26.078 26.078
2fx / DLx 4.99 5.42 5.13
2fy / DLy 3.06 3.55 3.41

Example 3 (virtual image) Example 3 (real image)
α 70 70.526
β 26.208 26.208
2fx / DLx 5.06 4.62
2fy / DLy 3.24 3.03

  FIG. 17 is a diagram showing a distortion map when a decentered optical system according to an embodiment of the present invention is projected using an image projection apparatus.

  As the image, a rectangular grid that can easily visually recognize the distortion in the projected image was used. The maximum distortion amount in the entire screen is 1.78%, and it can be seen that the lattice pattern has a well-corrected aberration up to the periphery of the screen.

  As described above, according to the decentered optical system 2, it is possible to appropriately correct distortion and project or capture an image while having a small and simple structure.

  FIG. 18 is a diagram showing a spot diagram when a decentered optical system according to an embodiment of the present invention is projected on an image projection apparatus.

  In FIG. 18, the vertical axis is divided according to each angle of view, and the angle of view is described in the order of horizontal and vertical. The evaluation wavelength is set to be white light at a ratio of 65 wavelengths of 656.3, 587.6, 546.1, 486.1, and 435.8 (nm) according to the relative visibility. From FIG. 18, the change of the spot diagram due to the change of the angle of view can be confirmed. Although it tends to expand as it goes off-axis, it can be seen that chromatic aberration of magnification is generally well corrected.

  Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention. Is.

1. Image projection device (image pickup device)
2 ... Decentered optical system 3 ... Image display element (however, in the case of an image projection apparatus. In the case of an image imaging apparatus, "image imaging element")
4 ... Holding member 5 ... Illuminating unit 6 ... Prism 11 ... Image plane (however, in the case of an image projection apparatus, "object plane" in an image pickup apparatus)
12: Object plane (however, in the case of an image projection apparatus, “image plane” in an image pickup apparatus)
13... Exit pupil (however, in the case of an image projector, “incident pupil” in an image pickup device)

Claims (28)

From the image plane to the object plane,
A first reflecting member having a first reflecting surface directed toward the image plane side;
A second reflecting member having a second reflecting surface facing the first reflecting surface and facing the object surface;
Have
Forming an exit pupil on the image plane side of the first reflecting surface;
When a light ray passing from the image plane through the exit pupil center to the center of the object plane is an axial principal ray, the first reflection surface and the second reflection surface are respectively relative to the axial principal ray. A decentered optical system characterized by being decentered. 2. The decentered optical system according to claim 1, wherein an angle formed by an extension line of the axial principal ray at the center of the exit pupil and the object plane is α, and the following expression (1) is satisfied. system.
50 ° ≦ α ≦ 120 ° (1) The following expression (2) is satisfied, where β is an angle of the axial principal ray between the first reflecting surface and the second reflecting surface with respect to the first reflecting surface. The decentered optical system described in 1.
10 ° ≦ β ≦ 50 ° (2) 4. The decentered optical system according to claim 1, wherein at least one of the first reflecting surface and the second reflecting surface is a surface reflecting surface. 5. 4. The decentered optical system according to claim 1, wherein at least one of the first reflecting surface and the second reflecting surface is a back surface reflecting surface. 5. 6. The eccentricity according to claim 1, wherein a center of at least one of the first reflecting surface and the second reflecting surface is deviated from an observer's visual axis. Optical system. The decentered optical system according to any one of claims 1 to 6, wherein at least one of the first reflecting surface and the second reflecting surface is a rotationally asymmetric surface. The decentered optical system according to claim 7, wherein at least one of the first reflecting surface and the second reflecting surface is a free-form surface. The decentered optical system according to claim 1, wherein at least one of the first reflecting surface and the second reflecting surface is a rotationally symmetric surface. A decentered optical system according to any one of claims 1 to 9,
An image display element arranged on the object plane to display an image;
With
An image displayed on the image display element is reflected by the second reflecting surface, reflected by the first reflecting surface, passes through the exit pupil, and is enlarged to the image surface without forming an intermediate image. An image projector characterized by being projected. The image projection apparatus according to claim 10, wherein the decentering optical system switches between a state of projecting a real image and a state of projecting a virtual image by changing an imaging distance. The origin is the center of the exit pupil,
The axial principal ray direction from the center of the exit pupil toward the first reflecting surface is the positive direction of the Z axis,
A direction in which a line obtained by projecting the axial principal ray on a plane orthogonal to the Z-axis toward the object plane from the origin is a negative direction of the Y-axis,
The following conditional expression (3) and conditional expression (4) are satisfied, where an axis that is orthogonal to the Z axis and the Y axis and that forms a right-handed orthogonal coordinate system is an X axis: The image projection apparatus described.
0.1 ≦ 2fx / DLx ≦ 10 (3)
0.1 ≦ 2fy / DLy ≦ 8 (4)
However,
fx is the focal length in the XZ plane,
DLx is the length in the XZ plane of the image display element,
fy is the focal length in the YZ plane,
DLy is the length in the YZ plane of the image display element,
It is. 13. The image projection apparatus according to claim 10, further comprising an aperture stop movably installed at a position of the exit pupil or a predetermined position facing the first reflecting surface. A first holding unit for holding the image display element;
A second holding unit that holds the first reflecting member so as to be movable with respect to the image display element;
A third holding part for holding the second reflecting member so as to be movable with respect to the image display element;
The image projection apparatus according to claim 10, further comprising a holding member having the following. The second holding unit includes a storage state in which the first reflection member is stored so as to overlap the image display element, and a projection state in which an image displayed on the image display element is projected onto the image plane. Hold switchable,
The third holding unit holds the second reflecting member so as to be switchable between a storage state in which the second reflection member is stored so as to overlap the image display element and a projection state in which an image displayed on the image display element is projected. The image projector according to claim 14, wherein The image projection apparatus according to claim 14, wherein a virtual image with respect to an image of the image display element is projected by changing an optical path length from the position of the exit pupil to the image display element. The second holding unit moves the first reflecting member relative to the image display element;
The image projection apparatus according to claim 16, wherein the third holding unit projects a virtual image by moving the second reflecting member with respect to the image display element. The image projection apparatus according to claim 17, wherein the first reflecting member and the second reflecting member move relatively. The image projection device according to claim 16, wherein a virtual image with respect to an image of the image display element is projected by moving the image display element. The image projection apparatus according to claim 10, wherein the first reflecting member has a transmittance greater than zero. 21. The image projection apparatus according to claim 10, wherein the first reflecting member has a reflectance of 10% or more. The image projection apparatus according to claim 20, wherein the first reflecting member is a half mirror. The image projection apparatus according to claim 10, wherein the decentered optical system has a transmittance of 5% or more with respect to external light. The first reflective member includes a transmission surface facing the second reflection member, and the first reflection surface disposed on the opposite side of the transmission surface with respect to the second reflection member.
The image projection apparatus according to claim 10, wherein the transmission surface and the first reflection surface have the same shape. The image display element is a reflective liquid crystal or a transflective liquid crystal,
The image projection device according to claim 10, further comprising an illumination unit that illuminates the image display element. 26. The image projection apparatus according to claim 25, wherein the illumination unit includes a polarization beam splitter. The image projection apparatus according to claim 25, wherein the illumination unit includes a diffractive optical element. A decentered optical system according to any one of claims 1 to 9,
An image pickup device that is arranged on the image plane and picks up an image;
An aperture stop serving as an entrance pupil that is movably installed at a predetermined position facing the first reflecting surface;
With
The image pickup apparatus according to claim 1, wherein an image of the object plane passes through the aperture stop, is reflected by the first reflection plane, is reflected by the second reflection plane, and is picked up by the image pickup element.

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