JP2018205699A - Imaging optical system, and imaging device and projection device including the same - Google Patents

Abstract

To provide a wide-angle and compact imaging optical system having high optical performance, and an imaging device and a projection device including the imaging optical system.SOLUTION: An imaging optical system 1 comprises, in order from an enlargement side, a first optical system 111 having a reflection surface, and a second optical system 112 having a refractive surface, wherein between the first optical system 111 and the second optical system 112, an intermediate image 104 of an object is formed. The first optical system 111 comprises, in order from the enlargement side, a first reflection group 113 composed of one or more negative power reflection surfaces 115, and a second reflection group 114 composed of plural positive power reflection surfaces 116, 117, wherein an absolute value of power of the reflection surface 115 arranged closest to the enlargement side in the first reflection group 113 becomes the smallest value in the first optical system 111.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging optical system, and is suitable, for example, for an imaging device that acquires an image and a projection device that projects an image.

  2. Description of the Related Art Conventionally, an imaging optical system used in an optical apparatus such as an imaging apparatus or a projection apparatus has been known that includes a reflective optical element such as a mirror and a refractive optical element such as a lens.

  Patent Document 1 describes a projection optical system including a mirror including a concave reflecting surface and a plurality of lenses. In Patent Document 1, the projection optical system is made compact by appropriately setting the distance from the most magnified reflective surface to the display surface of the display element and the distance from the optical axis to the end of the display surface. And high resolution.

  Patent Document 2 describes a projection optical system including a mirror including a convex reflecting surface, a mirror including a concave reflecting surface, and a plurality of lenses. In Patent Literature 2, the projection optical system is widened and made compact by appropriately setting the arrangement and focal length of each mirror.

JP 2008-250296 A JP 2009-157223 A

  However, in the projection optical system described in Patent Document 1, since the reflecting surface on the most enlarged side has a concave shape, it is necessary to enlarge the reflecting surface in order to realize a wide angle. In order to widen the angle while suppressing an increase in the size of the reflecting surface, it is necessary to increase the curvature of the reflecting surface, but it is necessary to increase the number of lenses in order to correct the increased aberration. It becomes difficult to make the whole system compact.

  In addition, in the projection optical system described in Patent Document 2, since only one concave reflecting surface is disposed, both the aberration generated on the convex reflecting surface and the aberration generated on the plurality of lenses are favorably corrected. I can't. In order to correct each aberration, it is necessary to increase the number of lenses, which makes it difficult to make the entire system compact.

  An object of the present invention is to provide an imaging optical system having high optical performance while being wide-angle and compact, and an imaging apparatus and a projection apparatus including the same.

  In order to achieve the above object, an imaging optical system as one aspect of the present invention includes a first optical system having a reflecting surface and a second optical system having a refracting surface, which are arranged in order from the magnification side. An imaging optical system that forms an intermediate image of an object between the first optical system and the second optical system, wherein the first optical system is arranged in order from the magnification side. A first reflecting group composed of a negative power reflecting surface and a second reflecting group composed of a plurality of positive power reflecting surfaces, and the reflecting surface disposed on the most enlarged side in the first reflecting group. The absolute value of power is the smallest in the first optical system.

  An imaging optical system as another aspect of the present invention includes a first optical system having a reflecting surface and a second optical system having a refracting surface, which are arranged in order from the magnification side. An imaging optical system that forms an intermediate image of an object between an optical system and the second optical system, wherein the first optical system is arranged in order from the magnification side and has one or more negative powers The absolute value of the power of one reflecting surface which is composed of a first reflecting group consisting of reflecting surfaces and a second reflecting group consisting of a plurality of reflecting surfaces of positive power and which is arranged on the most enlarged side in the first reflecting group. The value is larger than the absolute value of the power of each of the second reflecting surface arranged on the most enlarged side in the second reflecting group and the third reflecting surface adjacent to the second reflecting surface. To do.

  According to the present invention, it is possible to provide an imaging optical system having high optical performance while being wide-angled and compact, and an imaging apparatus and a projection apparatus including the same.

FIG. 3 is a power arrangement diagram of the imaging optical system according to the embodiment of the present invention. 1 is a schematic diagram of a main part of an imaging optical system according to an embodiment of the present invention. The figure for demonstrating the calculation method of the power of an aspherical reflective surface. 1 is a schematic diagram of a main part of an imaging optical system according to Embodiment 1 of the present invention. FIG. 5 is a schematic diagram of a main part of an imaging optical system according to Example 2 of the present invention. FIG. 6 is a schematic diagram of a main part of an imaging optical system according to Example 3 of the present invention. FIG. 9 is a schematic view of the main part of an imaging optical system according to Example 4 of the present invention. FIG. 6 is an aberration diagram of the imaging optical system according to Example 1 of the present invention. FIG. 6 is an aberration diagram of the imaging optical system according to Example 2 of the present invention. FIG. 10 is an aberration diagram of the imaging optical system according to Example 3 of the present invention. FIG. 10 is an aberration diagram of the imaging optical system according to Example 4 of the present invention. 1 is a schematic view of a main part of an optical device according to an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Each drawing may be drawn on a different scale for convenience. Moreover, in each drawing, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

FIG. 1 is a power layout diagram of an imaging optical system 1 according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a main part schematically showing the imaging optical system 1 (a cross-sectional view including an optical axis). It is. 1 and 2, an alternate long and short dash line 121 indicates an optical axis of a second optical system 112 described later, and a broken line AP _IMG indicates a position of an image (aperture image) of an aperture stop AP described later. Further, in FIG. 1, a solid line 103 indicates a paraxial ray passing through the center of the pupil of the imaging optical system 1, and a cross mark 104 is an intermediate having a conjugate relationship with the enlargement side conjugate surface 101 or the reduction side conjugate surface 102. The position of the image is shown.

  The imaging optical system 1 can be applied to an optical device such as an imaging device or a projection device. When the imaging optical system 1 is applied as an imaging optical system (reduction system) to an imaging apparatus, the imaging surface (light receiving surface) of the imaging element is disposed at the position of the reduction-side conjugate surface 102 of the imaging optical system 1. . When the imaging optical system 1 is applied as a projection optical system (enlargement system) to a projection apparatus, the display surface of the display element is disposed at the position of the reduction-side conjugate surface 102 of the imaging optical system 1. At this time, in the imaging optical system and the projection optical system, the object side and the image side are reversed, and the optical paths are reversed. In the following description, it is assumed that the imaging optical system 1 is applied to an imaging apparatus.

  The imaging optical system 1 includes a first optical system 111 having a reflecting surface and a refracting surface, which are arranged in order from the side of the enlargement side conjugate surface 101 (enlargement side) to the side of the reduction side conjugate surface 102 (reduction side). And a second optical system 112. Further, the imaging optical system 1 forms an intermediate image 104 between the first optical system 111 and the second optical system 112. The first optical system 111 includes a first reflection group 113 including one or more negative power reflecting surfaces 115 arranged in order along the optical path from the enlargement side, and positive power reflecting surfaces 116 and 117. And a second reflection group 114 including

  However, the power of the reflecting surface in the present embodiment indicates the degree of light collection by the reflecting surface and is represented by the reciprocal of the focal length of the reflecting surface. That is, the power of the reflecting surface corresponds to the power (refractive power) of the refracting surface, and is proportional to the curvature of the reflecting surface. Note that the sign of power when the reflecting surface is convex is negative, and the sign of power when the reflecting surface is concave is positive. Further, the reflection group in the present embodiment means an aggregate of reflection surfaces having one or more powers.

  Thus, the 1st optical system 111 can implement | achieve widening, without enlarging a reflective surface, by taking the structure by which the reflective surface 115 which has negative power is arrange | positioned at the most expansion side. In addition, the first optical system 111 adopts a configuration in which the reflecting surfaces 116 and 117 having positive power are arranged on the reduction side with respect to the reflecting surface 115, so that the aberration generated in the reflecting surface 115 and the second optical system is reduced. It can be corrected. Specifically, it is possible to correct curvature of field and distortion generated in the second optical system by the reflecting surface 117 while correcting the distortion occurring on the reflecting surface 115 by the reflecting surface 116. Therefore, according to the imaging optical system 1 according to the present embodiment, high optical performance can be realized while being wide-angle and compact.

  In the present embodiment, the first optical system 111 has a positive power as a whole, the first reflection group 113 has a negative power, and the second reflection group 114 has a positive power. The first reflection group 113 includes one reflective optical element (convex mirror) including a convex reflection surface 115, and the second reflection group 114 includes two reflection surfaces 116 and 117 each having a concave shape. It consists of a reflective optical element (concave mirror).

  However, a configuration in which the first reflection group 113 includes a plurality of reflection surfaces and a configuration in which the second reflection group 114 includes three or more reflection surfaces may be employed as necessary. At this time, in order to reduce the aberration generated in the first reflection group 113 and the second reflection group 114, the first reflection group 113 is configured only by a reflection surface having a negative power, and the second reflection group 114 is positive. It is desirable to configure only with a reflective surface having power.

  The second optical system 112 according to this embodiment includes one (single) refractive optical element (lens) 118 having positive power and an aperture stop AP for determining the F value of the imaging optical system 1. It has a positive power as a whole. The aperture stop AP is disposed on the reduction side with respect to the refractive optical element 118, but may be disposed on the enlargement side as necessary. Further, the second optical system 112 may include a plurality of refractive optical elements as necessary. At this time, the aperture stop AP may be disposed between the refractive optical elements.

  The optical axis 121 of the second optical system 112 is determined by the refractive optical element 118 and the aperture stop AP. Specifically, the optical axis 121 is an axis passing through the center of curvature of each refractive surface (lens surface) of the refractive optical element 118 and the center of the aperture stop AP. That is, the optical axis 121 coincides with the rotational symmetry axis of each refractive surface. When the second optical system 112 includes a plurality of refractive optical elements, at least one of some refractive optical elements or the aperture stop AP may be decentered as necessary. In this case, the axis that passes through the center of curvature of the refracting surface and the center of the aperture stop AP most often is the optical axis 121.

In the present embodiment, the aperture image AP _IMG is formed between the reflecting surface 116 and the reflecting surface 117 in the second reflecting group 114. As described above, the astigmatism of the intermediate image 104 can be favorably corrected by disposing the reflecting surfaces having positive power on the enlargement side and the reduction side of the aperture image AP _IMG . Accordingly, correction of aberrations by the second optical system 112 is facilitated, so that the number of refractive optical elements can be reduced and the entire system can be made compact.

Even when the second reflection group 114 includes three or more reflection surfaces, a configuration in which the aperture image AP _IMG is formed between two adjacent reflection surfaces having positive power may be employed. If necessary, a configuration in which a plurality of aperture images are formed, for example, a configuration in which an aperture image is formed not only on the second reflection group 114 but also on the optical path of the second optical system 112 may be adopted.

In the present embodiment, among the reflecting surfaces of the second reflecting group 114, the effective region (the region through which the effective light beam contributing to image formation) of the reflecting surface 117 disposed on the most reduction side is an aspherical surface. It is desirable. The reflecting surface 117 is the reflecting surface farthest from the aperture image AP _IMG , in other words, the reflecting surface closest to the second optical system 112. By making the reflecting surface 117 an aspherical surface, the height of light incident on the second optical system 112 can be controlled, and distortion in the imaging optical system 1 can be corrected well. When the second reflecting group 114 has three or more reflecting surfaces, at least the reflecting surface having the positive power disposed on the most reduction side may be an aspherical surface, and other reflecting surfaces may be used as necessary. Or an aspherical surface.

  Here, in order to make the imaging optical system 1 more compact, a method of arranging the reflecting surfaces closer to each other can be considered. However, when the interval between the reflecting surfaces is reduced, it is necessary to increase the power of each reflecting surface, so that it is difficult to correct various aberrations by each reflecting surface. Therefore, it is more preferable that not only the reflecting surface 117 in the second reflecting group 114 but also the reflecting surface 115 in the first reflecting group 113 is an aspherical surface. As a result, the effect of correcting aberrations by the reflecting surface 117 can be compensated by the reflecting surface 115, so that various aberrations can be corrected well even when the interval between the reflecting surfaces is reduced.

In addition, when the 1st reflection group 113 has a some reflective surface, it is desirable to make the reflective surface of the negative power arrange | positioned at the most expansion side into an aspherical surface. This is because the light beams are most separated from each other when they are incident on the reflecting surface arranged on the most enlarged side (most distant from the aperture image AP _IMG ). This is because it becomes easy to control each light beam. However, other reflective surfaces in the first reflective group 113 may be aspherical surfaces as necessary.

When both the first reflection group 113 and the second reflection group 114 have aspheric surfaces, the maximum value of the aspheric amount of the aspheric surface in the first reflection group 113 is Q ₁ , and the aspheric surface of the aspheric surface in the second reflection group 114. when the maximum value of the amount and Q _2, it is preferable to satisfy the following condition (1).
0.35 ≦ | Q ₁ / Q ₂ | ≦ 0.80 (1)

By satisfying conditional expression (1), various aberrations can be easily corrected by each aspherical surface even when the interval between the reflecting surfaces is reduced. If the lower limit of conditional expression (1) is not reached, it may be difficult to correct distortion by each aspherical surface. If the upper limit of conditional expression (1) is exceeded, it may be difficult to correct various aberrations generated on the reflecting surface 115 by the reflecting surface 116. It is more preferable to satisfy the following conditional expression (2).
0.42 ≦ | Q ₁ / Q ₂ | ≦ 0.70 (2)

In general, since negative distortion tends to occur in the refraction system (refractive group), it is desirable to reduce the power at the peripheral portion of the reflecting surface by setting the aspheric amount of the reflecting surface to be negative. As a result, the height of the light beam incident on the refraction system can be increased toward the periphery, so that negative distortion occurring in the refraction system can be favorably corrected. Therefore, it is desirable to satisfy at least one of the following conditional expressions (3) and (4).
Q ₁ <0 (3)
Q ₂ <0 (4)

  In addition, it is desirable that the reflecting surface 115 disposed on the most enlarged side in the first reflecting group 113 according to the present embodiment be a reflecting surface having the smallest power. That is, it is desirable to make the absolute value of the power of the reflecting surface 115 the smallest in the first optical system 111. Thereby, various aberrations generated in the first optical system 111 and the second optical system 112 can be corrected more favorably. When the absolute value of the power of the reflecting surface arranged on the most enlarged side in the first reflecting group 113 is larger than that of other reflecting surfaces, negative distortion is likely to occur. In this case, it is necessary to increase the reflecting surface of the second reflecting group 114 and the refracting surface of the second optical system 112 in order to correct the distortion, which may make it difficult to reduce the size of the entire system.

  Alternatively, the absolute value of the power of the first reflecting surface disposed on the most magnified side in the first reflecting group 113 is set as the second reflecting surface disposed on the most enlarging side in the second reflecting group 114 and the second reflecting surface. You may make larger than the absolute value of each power of the 3rd reflective surface adjacent to a reflective surface. Accordingly, it is possible to realize a wide-angle imaging optical system while being small. If the above relationship is not satisfied, field curvature of the intermediate image is likely to occur. In this case, it is necessary to increase the refracting surface of the second optical system 112 in order to correct the curvature of field, which may make it difficult to reduce the size of the entire system.

  Furthermore, it is desirable that the reflective surface 117 arranged on the most reduced side among the reflective surfaces included in the second reflective group 114 according to the present embodiment be a reflective surface having the largest power. That is, it is desirable that the absolute value of the power of the reflecting surface 117 is maximized in the first optical system 111. As described above, by appropriately setting the power of the reflecting surface 117 closest to the second optical system 112, it is possible to satisfactorily correct astigmatism in the intermediate image 104.

  Further, it is desirable that at least one of the reflection surfaces provided in the first optical system 111 has a rotationally symmetric shape with respect to the optical axis 121 of the second optical system 112. By adopting a configuration in which the first optical system 111 includes a rotationally symmetric reflecting surface, it is possible to easily position the reflecting surface around the optical axis 121. As shown in FIG. 2, each reflecting surface in the first optical system 111 does not intersect with the optical axis 121, but all have a rotationally symmetric shape with respect to the optical axis 121. That is, each reflecting surface can be considered as a part of a rotationally symmetric reflecting surface having a center of curvature on the optical axis 121.

  As described above, the imaging optical system 1 according to this embodiment forms the intermediate image 104 between the first optical system 111 and the second optical system 112. Thereby, since the effective area | region in each reflective surface and each refractive surface can be made small, it becomes possible to reduce each reflective optical element and each refractive optical element.

  Furthermore, it is desirable to shift the position where the intermediate image 104 is formed from the axial direction to the axial direction toward the reduction side by setting the Petzval sum of the first optical system 111 to a negative value. Thereby, since the curvature of field caused by the second optical system 112 can be canceled, aberration correction in the entire imaging optical system 1 is facilitated, and the number of refractive optical elements in the second optical system 112 can be reduced. It becomes possible to reduce.

  Specifically, it is desirable that the Petzval sum of the first optical system 111 when the focal length of the entire imaging optical system 1 is normalized as 1, is a value smaller than −0.05. Thereby, the curvature of field caused by the second optical system 112 can be corrected, and the incident angle of the light beam with respect to the second optical system 112 can be reduced, so that the intermediate image 104 in the second optical system 112 is the most intermediate image 104. It is possible to reduce the size of the near refractive optical element. Furthermore, it is more preferable to set the normalized Petzval sum of the first optical system 111 to a value smaller than −0.07.

  Further, by providing a moving mechanism for moving the entire second optical system 112 or only the refractive optical element 118 in the optical axis direction, it is possible to perform focusing adjustment of the imaging optical system 1. Also good. Thereby, for example, even when the position of the enlargement-side conjugate surface 101 moves in the optical axis direction, it is possible to focus well. As the moving mechanism, a driving member such as a holding member or a motor that movably holds the refractive optical element 118 and the aperture stop AP can be employed.

  When the second optical system 112 includes a plurality of refractive optical elements, at least one refractive optical element, or at least one refractive optical element and the aperture stop AP may be moved. At this time, the moving amount and moving direction of each refractive optical element and the aperture stop AP may be made different from each other as necessary. In this way, by adopting a configuration in which focusing is performed by moving the refractive optical element, the moving mechanism can be simplified and the entire apparatus can be downsized as compared with a configuration in which focusing is performed by moving the reflective optical element. It becomes possible.

  In addition, you may employ | adopt a prism as a reflective optical element in the 1st optical system 111 as needed. In order to make the imaging optical system 1 more compact, a reflecting optical element such as a folding mirror may be disposed on the optical path of the second optical system 112. Further, as a measure against dust, an optical member such as a cover glass or a protective film may be disposed at any position on the optical path of the imaging optical system 1.

  Here, a method for calculating the power of the reflecting surface when the effective area of the reflecting surface in the first optical system 111 is an aspherical surface will be described with reference to FIG. First, if the effective area of the reflecting surface is a rotationally symmetric aspherical surface, the axis of rotation symmetry is the optical axis, and the point on the optical axis in the effective area (center point) and the point farthest from the center point are A spherical surface that passes and whose center of curvature is located on the optical axis is defined as a reference spherical surface. Further, when the effective area of the reflecting surface is a free-form surface, an arbitrary point P in the effective area is determined, and a perpendicular passing through the point P on the plane in contact with the point P, that is, the surface normal of the effective area at the point P is expressed as light. Axis. A spherical surface that passes through the point P in the effective area and the point farthest from the point P and whose center is located on the optical axis is defined as a reference spherical surface.

  As described above, when the effective area of the reflecting surface is an aspherical surface, a reference spherical surface is determined, and power may be calculated based on the reference spherical surface. Note that the effective diameter of the reference spherical surface can be calculated from the imaging magnification, F value, maximum image height, and the like of the imaging optical system 1. Further, it is possible to determine whether the power of the reflecting surface is positive or negative depending on whether the reference spherical surface is concave or convex.

[Example]
Each of FIGS. 4 to 7 is a schematic diagram of a main part of the imaging optical system according to Examples 1 to 4 of the present invention. Each of the first optical systems 41, 51, 61, and 71 includes negative power convex mirrors 8a, 9a, 10a, and 11a that constitute the first reflection group, and a positive power concave mirror that constitutes the second reflection group. 8b, 8c, 9b, 9c, 9d, 10b, 10c, 11b, and 11. 4 to 7 show the non-effective areas (areas where the effective light beam contributing to image formation is not incident) on each reflecting surface without being omitted.

  Each of the second optical systems 42, 52, 62, 72 includes an aperture stop AP, a first group 8F, 9F, 10F, 11F, and a second group 8FL, 9FL, 10FL, 11FL. . In each second optical system, each of the first group and the second group is a lens group that can move in the optical axis direction. By adjusting the positions of these two lens groups, it is possible to satisfactorily perform focus adjustment and correction of field curvature.

  In each of the imaging optical systems according to Examples 1 to 4, each of the reflecting surfaces 8c, 9d, 10c, and 11c on the most reduced side is an aspherical surface. Each imaging optical system uses this aspherical surface to control the height of light rays incident on the second optical system and to correct distortion well. In each of the imaging optical systems according to Examples 1 to 4, all the reflecting surfaces are rotationally symmetric with respect to the optical axis of the second optical system. With this configuration, positioning of each reflecting surface is facilitated, and the manufacturing process of the imaging optical system is simplified.

  8 to 11 are aberration diagrams on the reduction-side conjugate surface of the imaging optical system according to Examples 1 to 4, respectively. The solid line in the spherical aberration diagram indicates the d line, the two-dot chain line indicates the g line, the solid line in the astigmatism diagram indicates the sagittal ray, the dotted line indicates the meridional ray, the solid line in the distortion diagram shows the d line, and 2 in the chromatic aberration diagram The dotted line indicates the g line.

Hereinafter, Numerical Examples 1 to 4 corresponding to the respective imaging optical systems according to Examples 1 to 4 are shown in Tables 1 to 12, respectively. In each numerical example, the surface number indicates the number (i) of the optical surface counted from the enlargement side, “R” indicates the radius of curvature of the i-th optical surface (i-th surface), and “D” indicates the number of the surface. The inter-surface distance (distance on the optical axis) between the i-plane and the (i + 1) -th plane is shown. Each of “N _d ” and “ν _d ” indicates the refractive index and the Abbe number for the d-line of the medium between the i-th surface and the (i + 1) -th surface. The Abbe number ν _d is expressed by the following equation when the refractive indexes for the F-line and C-line of the medium between the i-th surface and the (i + 1) -th surface are N _F and N _C , respectively.

  “F” indicates the focal length, “Fno” indicates the F value on the reduction side, “β” indicates the imaging magnification, and “L” indicates the maximum axis from the on-axis image height on the reduction-side conjugate plane. The distance to the outside image height (position where the most off-axis light beam is incident) is shown. In each numerical example, “Refl” is added to the reflecting surface after the surface number, “AP” is added to the aperture stop after the surface number, and “* (asterisk) is added to the aspheric surface after the surface number. ) ”.

The aspherical shape has a conic constant of K, an aspherical coefficient of C ₄ , C ₆ , C ₈ , C ₁₀ , a height from the optical axis in a direction perpendicular to the optical axis of the second optical system, and a height When the surface position in the optical axis direction with respect to the center point (surface vertex) at r is A (r), it is expressed by the following equation. In each numerical example, “ ^EN ” in the numerical values of the conic constant K and the aspheric coefficients C ₄ , C ₆ , C ₈ , and C ₁₀ means “× 10 ^−N ”.

  (Numerical example 1)

  (Numerical example 2)

  (Numerical Example 3)

  (Numerical example 4)

  Table A shows the absolute value of the power of each reflecting surface in the imaging optical systems of Examples 1 to 4. Surface number 1 indicates the reflective surface (first reflective surface) disposed on the most enlarged side in the first reflective group 113. Surface numbers 2 and 3 indicate a reflective surface (second reflective surface) disposed on the most enlarged side in the second reflective group 114 and a reflective surface (third reflective surface) adjacent to the reflective surface. From Table A, it can be seen that in Examples 1, 3, and 4, the absolute value of the power of the reflecting surface arranged on the most enlarged side is the smallest in the first optical system 111. Moreover, about Example 2, it turns out that the absolute value of the power of a 1st reflective surface is larger than the absolute value of each power of a 2nd and 3rd reflective surface.

[Optical device]
FIG. 12 is a schematic diagram of a main part of an optical device 100 including the imaging optical system according to the above-described embodiment. When the optical device 100 is an imaging device, the subject on the placement surface arranged on the enlargement-side conjugate surface 101 can be imaged by an imaging element arranged at the position of the reduction-side conjugate surface of the imaging optical system. it can. As the imaging element, a CCD (Charge Coupled Device) sensor, a CMOS (Complementary Metal Oxide Semiconductor) sensor, or the like can be employed.

  When the optical device 100 is a projection device, the image displayed by the display element disposed at the position of the reduction-side conjugate surface of the imaging optical system is projected onto the projection surface disposed at the magnification-side conjugate surface 101. can do. As the display element, LCD (Liquid Crystal Display), LCOS (Liquid Crystal On Silicon), DMD (Digital Mirror Device), or the like can be used.

  The preferred embodiments and examples of the present invention have been described above, but the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes can be made within the scope of the gist.

DESCRIPTION OF SYMBOLS 1 Imaging optical system 104 Intermediate image 111 1st optical system 112 2nd optical system 113 1st reflection group 114 2nd reflection group 115,116,117 Reflection surface

Claims (11)

An intermediate image of an object between the first optical system and the second optical system, which is composed of a first optical system having a reflecting surface and a second optical system having a refractive surface, which are arranged in order from the magnification side. An imaging optical system for forming
The first optical system includes a first reflection group including one or more negative power reflection surfaces and a second reflection group including a plurality of positive power reflection surfaces arranged in order from the magnification side. And
An imaging optical system characterized in that the absolute value of the power of the reflecting surface disposed on the most enlarged side in the first reflecting group is the smallest in the first optical system. An intermediate image of an object between the first optical system and the second optical system, which is composed of a first optical system having a reflecting surface and a second optical system having a refractive surface, which are arranged in order from the magnification side. An imaging optical system for forming
The first optical system includes a first reflection group including one or more negative power reflection surfaces and a second reflection group including a plurality of positive power reflection surfaces arranged in order from the magnification side. And
The absolute value of the power of the first reflecting surface disposed on the most magnified side in the first reflecting group is the same as that on the second reflecting surface and the second reflecting surface disposed on the most magnified side in the second reflecting group. An imaging optical system characterized in that it is larger than the absolute value of the power of each of the adjacent third reflecting surfaces.   The imaging optical system according to claim 1, wherein the second optical system includes an aperture stop.   The imaging optical system according to claim 3, wherein the positive power reflecting surface is disposed on each of an enlargement side and a reduction side of an image of the aperture stop.   5. The imaging optical system according to claim 1, wherein the reflecting surface disposed closest to the reduction side in the second reflecting group is an aspherical surface.   The imaging according to any one of claims 1 to 5, wherein the absolute value of the power of the reflecting surface arranged closest to the reduction side in the second reflecting group is the largest in the first optical system. Optical system.   The imaging optical system according to claim 1, wherein the Petzval sum of the first optical system when the focal length of the entire system is 1 is smaller than −0.05. .   8. The imaging optical system according to claim 1, wherein the first optical system includes a reflecting surface that is rotationally symmetric with respect to the optical axis of the second optical system. 9.   The imaging optical system according to any one of claims 1 to 8, wherein the second optical system includes a refractive optical element that moves during focusing.   An imaging apparatus comprising: the imaging optical system according to claim 1; and an imaging element including an imaging surface disposed on a reduction-side conjugate surface of the imaging optical system.   A projection apparatus comprising: the imaging optical system according to claim 1; and a display element including a display surface disposed on a reduction-side conjugate surface of the imaging optical system.

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