Optical system and observation apparatus having the same

Abstract

To provide a compact optical system having a wide viewing angle.SOLUTION: An optical system that forms an enlarged image of a display surface in an exit pupil and forms a reduced image of the exit pupil on an imaging surface, the optical system including a first semi-transmissive reflective surface and a second semi-transmissive reflective surface that are arranged in order in a first optical path from the display surface to the exit pupil, and an aperture stop and an optical element that are arranged in order in a second optical path from the exit pupil to the imaging surface, light from the display surface being transmitted through the first semi-transmissive reflective surface and reflected by the second semi-transmissive reflective surface, light from the exit pupil is transmitted through the second semi-transmissive reflection surface, transmitted through the first semi-transmissive reflection surface, and guided to the imaging surface via the aperture stop and the optical element, and in a direction perpendicular to an optical axis of the optical system, a distance from the optical axis to a center of the imaging surface is less than or equal to a distance from the optical axis to a center of the aperture stop.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system and an observation device having the same. [Background technology]

[0002] Patent Document 1 discloses an optical system including a first optical path that guides light from a display surface to a viewer's pupil, and a second optical path that guides light from the viewer's pupil to an imaging element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-86613 Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical system of Patent Document 1, the imaging optical system that guides light from the observer's pupil, which has passed through a part of the observation optical system along the first optical path, to the imaging element is located outside the effective light beam area of ​​the first optical path. However, as the viewing angle of the observation optical system becomes wider, the imaging angle of the observer's eye increases, and the number of components increases, resulting in a larger system.

[0005] An object of the present invention is to provide a compact optical system with a wide viewing angle. [Means for solving the problem]

[0006] An optical system as one aspect of the present invention is an optical system that forms an enlarged image of a display surface at an exit pupil and forms a reduced image of the exit pupil at an imaging surface, and has a first semi-transparent reflective surface and a second semi-transparent reflective surface arranged in that order on a first optical path from the display surface to the exit pupil, and an aperture stop and an optical element arranged in that order on a second optical path from the exit pupil to the imaging surface, wherein light from the display surface passes through the first semi-transparent reflective surface, is reflected by the second semi-transparent reflective surface, is reflected by the first semi-transparent reflective surface, passes through the second semi-transparent reflective surface, and is directed to the exit pupil, and light from the exit pupil passes through the second semi-transparent reflective surface, passes through the first semi-transparent reflective surface, and is directed to the imaging surface via the aperture stop and the optical element, and wherein in a direction perpendicular to the optical axis of the optical system, the distance from the optical axis to the center of the imaging surface is equal to or less than the distance from the optical axis to the center of the aperture stop. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a compact optical system with a wide viewing angle. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of an optical system according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating a first optical path. [Figure 3] FIG. 2 is a diagram showing details of a first lens unit. [Figure 4] FIG. 10 is a diagram showing the second optical path in detail. [Figure 5] FIG. 10 is a cross-sectional view of an optical system according to a modified example. [Figure 6] FIG. 10 is a cross-sectional view of an optical system according to a second embodiment. [Figure 7] FIG. 1 is a diagram showing an observation device including an optical system according to a first or second embodiment. [Figure 8] FIG. 2 is a diagram showing a display unit of the observation device. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted. [First embodiment] FIG. 1 is a cross-sectional view of an optical system 1 according to this embodiment. The optical system 1 is mounted on an observation device such as a head-mounted display (HMD). The optical system 1 includes a first lens unit (first optical system) LU1 and a second lens unit (second optical system) LU2. The first lens unit LU1 is an observation optical system that forms an enlarged image of a display surface PNL on a pupil (exit pupil) EP of the observer's eye EYE. The second lens unit LU2 is an imaging optical system that guides light emitted from the cornea of ​​the eye EYE and transmitted through the first lens unit LU1 to an imaging surface IM, forming a reduced image of the pupil EP on the imaging surface. The optical path from the display surface PNL to the pupil EP is referred to as a first optical path RY1, and the optical path from the eye EYE to the imaging surface IM is referred to as a second optical path RY2. A polarizing unit (circular polarization conversion element) FL is disposed on the first optical path RY1.

[0010] The display surface PNL can be the display surface of a display element (spatial modulation element) such as an LCD (Liquid Crystal Display) or an LED (Light Emitting Diode) display. For example, in an LCD, the polarization state can be controlled by the orientation of the liquid crystal. That is, the function of the polarizer FL can be realized within the display element. In this case, the polarizer FL does not need to be disposed on the first optical path RY1. The imaging surface IM is the light receiving surface of an imaging element. Examples of imaging elements include a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), and a SPAD (Single Photon Avalanche Diode).

[0011] The first lens unit LU1 includes a first lens G11 and a second lens G12 arranged in this order from the pupil EP toward the display surface PNL. In this embodiment, the lens surfaces included in the first lens unit LU1 have a surface shape that is rotationally symmetric with respect to the optical axis of the first lens unit LU1. The first lens G11 includes a first semi-transmissive reflective surface HM1, and the second lens G12 includes a second semi-transmissive reflective surface HM2. Note that the number of lenses constituting the lens unit LU1 may be increased as necessary to correct various aberrations. Furthermore, in this embodiment, the first semi-transmissive reflective surface HM1 and the second semi-transmissive reflective surface HM2 are included in the refractive surfaces of the first lens G11 and the second lens G12, respectively. However, the present invention is not limited to this. For example, the first semi-transmissive reflective surface HM1 and the second semi-transmissive reflective surface HM2 may be provided on both sides of the first lens G11. Alternatively, a cover glass or the like may be provided to provide a semi-transmissive reflective surface.

[0012] 2 is a diagram illustrating the first optical path RY1. The polarizing unit FL is composed of a polarizing element PL and a first quarter-wave plate QWP1. It is desirable that light having an axis perpendicular to the transmission axis of the polarizing element PL be absorbed by the polarizing element PL. The second semi-transmissive reflective surface HM2 is composed of a second quarter-wave plate QWP2 and a polarization-selective reflective polarizing element PBS.

[0013] The light beam from the display surface PNL is linearly polarized by the polarizing element PL. In FIG. 2, the light is formed in the vertical direction of the page. The linearly polarized light that passes through the polarizing element PL is circularly polarized by the first quarter-wave plate QWP1. In FIG. 2, the light is formed clockwise with respect to the traveling direction. The circularly polarized light that passes through the first quarter-wave plate QWP1 passes through the first semi-transmissive reflective surface HM1. The light beam (not shown) reflected by the first semi-transmissive reflective surface HM1 is formed into counterclockwise circularly polarized light with respect to the traveling direction, and is absorbed by the polarizing element PL after passing through the first quarter-wave plate QWP1.

[0014] The light beam transmitted through the first semi-transmissive reflecting surface HM1 is converted into linearly polarized light by the second quarter-wave plate QWP2 and enters the polarization-selective reflective polarizing element PBS. The polarization-selective semi-transmissive reflecting element PBS is configured to reflect linearly polarized light polarized in the same direction as when it passed through the polarizing element PL and to transmit linearly polarized light perpendicular to that direction. Therefore, the light beam transmitted through the first semi-transmissive reflecting surface HM1 is reflected once by the polarization-selective reflective polarizing element PBS. The reflected light beam is converted into circularly polarized light by passing through the second quarter-wave plate QWP2 again and is reflected by the first semi-transmissive reflecting surface HM1. The direction of rotation of the circularly polarized light relative to the traveling direction when it enters the first semi-transmissive reflecting surface HM1 is orthogonal to the direction of rotation of the circularly polarized light relative to the traveling direction after reflection. Therefore, the polarization state of the light beam after passing through the second quarter-wave plate QWP2 a second time is orthogonal to the polarization state after passing through the first time, and the light beam that has passed through the second quarter-wave plate QWP2 a second time passes through the polarization-selective reflective polarizing element PBS and reaches the pupil EP. Therefore, the light beam from the display surface PNL is reflected twice along the first optical path RY1. This makes it possible to widen the viewing angle and effectively correct various aberrations while minimizing the thickness of the first lens unit LU1 in the optical axis direction.

[0015] On the other hand, in the second optical path RY2, as shown in Figure 1, the light beam from the pupil EP side passes through the second semi-transmissive reflective surface HM2 and the first semi-transmissive reflective surface HM1, and is then guided to the imaging plane IM by the second lens unit LU2. By not using an optical path that reflects off the first semi-transmissive reflective surface HM1 and the second semi-transmissive reflective surface HM2, the number of times the light passes through semi-transmissive reflective surfaces can be reduced, making it possible to suppress a decrease in the amount of light incident on the imaging plane IM. Furthermore, by passing the light through the first lens unit LU1, the imaging angle of the eye EYE can be restricted, and vignetting of the pupil and iris due to the eyelid, eyeball rotation, etc. can be reduced.

[0016] The first optical path RY1 is not limited to the optical path shown in FIG. 2, and the transmission axis of the polarizing element PL and the slow axis of the quarter-wave plate may be changed as appropriate. Furthermore, the polarization-selective reflective polarizing element PBS transmits or reflects linearly polarized light in this embodiment, but may also be configured to transmit or reflect circularly polarized light depending on the direction of rotation. The semi-transmissive reflective surface may also be configured to transmit or reflect depending on the direction of linearly polarized light or circularly polarized light. In this case, the quarter-wave plate must be positioned appropriately, but appropriate modifications and variations are possible within the scope of the present embodiment.

[0017] Fig. 3 is a diagram showing the details of the first lens unit LU1, and Fig. 4 is a diagram showing the details of the second optical path RY2.

[0018] In the second optical path RY2, the light beam from the pupil EP side passes through the second lens G12 and the peripheral portion of the first lens G11 included in the first lens unit LU1, and is guided to the imaging plane IM by the second lens unit LU2.

[0019] The second lens unit LU2 is disposed outside the effective light beam region (the region where the light beam used for image observation exists) of the first optical path RY1, i.e., in the non-effective light beam region (the region where the light beam used for image observation does not exist). In this embodiment, the second lens unit LU2 includes an aperture stop SP, a third lens G21, and a fourth lens G22, arranged in this order from the pupil EP side to the display surface PNL side. The second lens unit LU2 corrects decentering aberrations that occur when light passes through the peripheral portions of the second lens G12 and the first lens G11, thereby improving detection accuracy at the imaging surface IM. Note that, to correct various aberrations, the order of optical elements may be changed or lenses may be added as necessary.

[0020] The optical system 1 is configured so that, in a direction perpendicular to the optical axis O of the first lens unit LU1, the distance from the optical axis O to the center of the imaging surface IM is equal to or less than the distance from the optical axis O to the center of the aperture of the aperture stop SP of the second lens unit LU2. This configuration makes it possible to realize a compact optical system 1 with a wide field of view. Furthermore, by integrating the image sensor that forms the imaging surface IM and the display device that forms the display surface PNL, the entire device can be made more compact. The optical axis O is defined by the reference axis of the rotationally symmetric optical surface of the first lens unit LU1 and is an axis that passes through the vertices of the surfaces of the lenses included in the first lens unit LU1.

[0021] The following describes the configuration that the optical system 1 preferably satisfies.

[0022] It is preferable that the optical system 1 satisfies the following conditional expression (1).

[0023] 0.6≦S2 / S1≦1.0 (1) Here, S1 is the distance from the optical axis O to the center of the aperture stop SP of the second lens unit LU2 in a direction perpendicular to the optical axis O. S2 is the distance from the optical axis O to the center of the imaging surface IM in a direction perpendicular to the optical axis O.

[0024] By satisfying conditional expression (1), even if the photographing angle of the eye EYE becomes large, the imaging plane IM can be brought close to the display plane PNL, and the entire device can be made smaller, which is preferable. In conditional expression (1), if the upper limit value is exceeded, the optical system 1 becomes large, which is not preferable. If the lower limit value is not satisfied, the display plane PNL and the imaging plane IM will interfere with each other, which is not preferable.

[0025] It is more preferable that the numerical range of conditional expression (1) be the numerical range of conditional expression (1a) below.

[0026] 0.7≦S2 / S1≦1.0 (1a) It is more preferable that the numerical range of conditional expression (1) be the numerical range of the following conditional expression (1b).

[0027] 0.70≦S2 / S1≦0.98 (1b) In this embodiment, the amounts of separation S1 and S2 are −16.3 and −14.4, respectively, and the value S2 / S1 is 0.883.

[0028] The optical system 1 is preferably configured so that, in a direction perpendicular to the optical axis O, the distance from the optical axis O to the intersection of an extension of the chief ray of a light beam that emerges from an extension of the image pickup surface IM and a position on the optical axis O of the pupil EP and then enters the second lens unit LU2 is equal to or less than the distance from the optical axis O to the intersection of an extension of the chief ray of a light beam that emerges from the extension of the image pickup surface IM and a position on the optical axis O of the pupil EP and then emerges from the second lens unit LU2. This configuration is preferable because it enables the realization of a compact optical system 1 with a wide field of view.

[0029] It is preferable that the optical system 1 satisfy the following conditional expression (2).

[0030] 0.6≦L2 / L1≦1.0 (2) L1 is the distance, in a direction perpendicular to the optical axis O, from the optical axis O to the intersection of an extension of the chief ray of a light beam that emerges from an extension of the image pickup surface IM and a position on the optical axis O of the pupil EP and then enters the second lens unit LU2. L2 is the distance, in a direction perpendicular to the optical axis O, from the optical axis O to the intersection of an extension of the chief ray of a light beam that emerges from an extension of the image pickup surface IM and a position on the optical axis O of the pupil EP and then emerges from the second lens unit LU2. The chief ray is defined as a light beam that passes through the center position of the aperture of the aperture stop SP in the second lens unit LU2.

[0031] By satisfying conditional expression (2), even if the photographing angle of the eye EYE becomes large, the imaging plane IM can be brought close to the display plane PNL, and the entire device can be made compact, which is preferable. In conditional expression (2), if the upper limit is exceeded, the optical system 1 becomes large, which is not preferable. If the lower limit is not satisfied, the display plane PNL and the imaging plane IM will interfere with each other, which is not preferable.

[0032] It is more preferable that the numerical range of conditional expression (2) be the numerical range of the following conditional expression (2a).

[0033] 0.7≦L2 / L1≦1.0 (2a) It is more preferable that the numerical range of conditional expression (2) be the numerical range of the following conditional expression (2b).

[0034] 0.70≦L2 / L1≦0.95 (2b) In this embodiment, the distances L1 and L2 are −17.6 and −16.4, respectively, and the value L2 / L1 is 0.825.

[0035] It is preferable that the optical system 1 satisfy the following conditional expression (3).

[0036] 0≦θ≦π / 3 (3) Here, θ is the angle [rad] made by a first line parallel to the optical axis O and an extension of the chief ray of the light beam that emerges from the pupil EP at a position on the optical axis O and then emerges from the second lens unit LU2. Note that, in the direction parallel to the optical axis O, the sign of the angle θ is positive when the intersection of the extension of the chief ray and the extension of the optical axis O is on the imaging plane IM side of the second lens unit LU2, and the sign of the angle θ is negative when it is on the pupil EP side.

[0037] In conditional expression (3), if the upper limit is exceeded, the bending angle of the light beam in the second lens unit LU2 must be increased, making correction difficult, or the angle of the light beam incident on the imaging surface IM becomes too large, reducing detection accuracy, which is undesirable. If the lower limit is not reached, the imaging surface IM and the display surface PNL are spaced apart, making the entire device larger, which is undesirable.

[0038] It is more preferable that the numerical range of conditional expression (3) be the numerical range of conditional expression (3a) below.

[0039] π / 12≦θ≦π / 3 (3a) It is more preferable that the numerical range of conditional expression (3) be the numerical range of the following conditional expression (3b).

[0040] π / 6≦θ≦π / 3 (3b) In this embodiment, the angle θ is 0.181π [rad].

[0041] The second lens unit LU2 preferably includes an optical surface that is asymmetrical in the vertical direction in the direction perpendicular to the optical axis O, with respect to the intersection of the chief ray of the second optical path RY2 and the optical surface. This is preferable because it makes it possible to more effectively correct decentering aberrations that occur when light passes through the peripheral portions of the second lens G12 and the first lens G11, and to bend the traveling direction of the light beam in a direction closer to the display surface PNL.

[0042] In the second lens unit LU2, the third lens G21 and the fourth lens G22 preferably include a diffractive surface. This is preferable because it makes it possible to effectively bend the traveling direction of the light beam toward the display surface PNL, thereby enabling the imaging surface IM and the display surface PNL to be closer to each other. It is more preferable that the second lens unit LU2 include two or more diffractive surfaces.

[0043] When the second lens unit LU2 includes two or more diffractive surfaces, it is preferable that the distance from the optical axis O to the center of the optically effective area (optically effective area) of each diffractive surface differs in the direction perpendicular to the optical axis O. Specifically, the optically effective areas of the multiple optical elements are arranged so that the diffractive surface closest to the imaging plane IM has a smaller distance from the optical axis O than the diffractive surface closest to the imaging plane IM. In this embodiment, the distance from the optical axis O to the center of the optically effective area of ​​the diffractive surface of the fourth lens G22 is smaller than the distance from the optical axis O to the center of the optically effective area of ​​the diffractive surface of the third lens G21. In this embodiment, the distance from the optical axis O to the center of the optically effective area of ​​the diffractive surface of the third lens G21 is −16.3 mm, and the distance from the optical axis O to the center of the optically effective area of ​​the diffractive surface of the fourth lens G22 is −15.5 mm.

[0044] Furthermore, it is more preferable to arrange the optical elements so that the chief ray of the light beam incident on each diffractive surface substantially coincides with the center of the optically effective area of ​​each diffractive surface, which is preferable because it bends the traveling direction of the light beam toward the display surface PNL and makes it possible to effectively correct various aberrations and improve the detection accuracy by the imaging surface IM.

[0045] In this embodiment, the third lens G21 and the fourth lens G22 each have a diffractive surface, but this is not limiting, and for example, diffractive surfaces may be provided on both sides of the third lens G21. Furthermore, the diffractive surfaces are not limited to diffractive surfaces, and may include refractive surfaces and reflective surfaces.

[0046] The imaging surface IM and the display surface PNL are preferably arranged so that their normals are parallel to each other, or so that the extension of the imaging surface IM and the extension of the display surface PNL are on the same plane. This results in a configuration that is suitable for integrating the imaging element that constitutes the imaging surface IM and the display element that constitutes the display surface PNL, making it possible to reduce the size of the entire device. Note that "parallel" and "coplanar" do not have to be strictly parallel or coplanar, and may be substantially parallel (approximately parallel) or substantially coplanar (approximately coplanar).

[0047] FIG. 5 is a cross-sectional view of optical system 2, a modified example of optical system 1. In addition to the components of optical system 1, optical system 2 includes a third lens unit (third unit) LU3 that forms a third optical path RY3 to guide light emitted from the light-emitting surface LS to the eye EYE. In the third optical path RY3, the light emitted from the light-emitting surface LS passes through the third lens unit LU3, then passes through the first semi-transmissive reflective surface HM1 of the first lens G11 and the second semi-transmissive reflective surface HM2 of the second lens G12, respectively, to illuminate the eye EYE. By passing the light through the third lens unit LU3, the unit size can be made more compact than when the light-emitting surface is located outside the lens outer diameter. Light diffused by the eye EYE or light reflected by the cornea is guided to the imaging plane IM by the first lens unit LU1 and the second lens unit LU2.

[0048] From the viewpoint of miniaturization, it is preferable that the display element, the imaging element, and the light-emitting element are arranged so that the normal to the display surface PNL, the normal to the imaging surface IM, and the light-emitting surface LS are parallel to one another. Also, from the viewpoint of miniaturization, it is preferable that the display element, the imaging element, and the light-emitting element are arranged so that the extended plane of the display surface PNL, the extended plane of the imaging surface IN, and the extended plane of the light-emitting surface LS are in the same plane.

[0049] 5, only one light-emitting surface LS is arranged, but light-emitting surfaces LS may be arranged at multiple positions to suppress vignetting of reflected light by the cornea of ​​the eye EYE due to eyelids, eyeball rotation, etc. In this case, it is preferable to arrange the third lens unit LU3 so as to correspond to the multiple light-emitting surfaces LS. Furthermore, it is preferable that the light emitted by the light-emitting surface LS is near-infrared light.

[0050] The third lens unit LU3 preferably includes an asymmetric optical surface to properly illuminate the eye EYE, thereby making it possible to keep the orientation angle of the light-emitting surface LS constant regardless of the first lens unit LU1. [Second embodiment] In the optical system of this embodiment, the basic configuration of the observation optical system is the same as in the first embodiment, but the configuration of the imaging optical system is different from that in the first embodiment. In this embodiment, only the configuration that is different from the first embodiment will be described, and a description of the configuration that is the same as in the first embodiment will be omitted.

[0051] FIG. 6 is a cross-sectional view of the optical system 2 of this embodiment. The second lens unit LU2 has an aperture stop SP, a third lens G21, and a fourth lens G22, arranged in this order from the pupil EP side to the display surface PNL side. The third lens G21 has a refractive surface. This reduces sensitivity due to lens temperature rise and manufacturing errors, while bending the traveling direction of the light beam toward the display surface PNL, thereby bringing the imaging surface IM closer to the display surface PNL. Furthermore, the imaging element that constitutes the imaging surface IM and the display element that constitutes the display surface PNL can be integrated, making it possible to reduce the size of the entire device.

[0052] In this embodiment, the third lens G21 has a refractive surface and the fourth lens G22 has a diffractive surface. However, this is not limiting. For example, the third lens G21 may have a refractive surface on one side and a diffractive surface on the other side. Also, an optical surface including a metasurface may be configured. Furthermore, to correct various aberrations, the order of optical elements may be changed or lenses may be added as necessary.

[0053] In this embodiment, the amounts of separation S1 and S2 are −17.0 and −16.4, respectively, and the value S2 / S1 is 0.964.

[0054] In this embodiment, the distances L1 and L2 are −18.5 and −16.4, respectively, and the value L2 / L1 is 0.886.

[0055] Furthermore, in this embodiment, the angle θ is 0.104π [rad]. [Observation equipment] 7 is a diagram showing an observation device 100 including the optical system of the first or second embodiment. FIG. 8 is a diagram showing the display units 102, 202 of the observation device 100. As shown in FIG.

[0056] The observation device 100 has an optical system 101, 201 and a display unit 102, 202. The display unit 102, 202 includes a display element PE, an imaging element SE, and a light-emitting element LE. The display element PE, the imaging element SE, and the light-emitting element LE may be formed on a single panel surface, or may be configured as separate members.

[0057] In the observation device 100, an image displayed by the display unit 102 is viewed as an enlarged image on the right eye side of the observer through the optical system 101, and an image displayed by the display unit 202 is viewed as an enlarged image on the left eye side of the observer through the optical system 201. Depending on the eyesight of the observer, the display unit or optical system may be different for the left and right. Also, although one image sensor SE and four light-emitting elements LE are disposed, the positions, numbers, and sizes can be modified and changed as appropriate.

[0058] The image of the observer's pupil and the image reflected from the cornea acquired by the image sensor SE are converted into the gaze direction by a calculation unit 301 built into the observation device 100 or connected externally. Depending on the gaze direction, the resolution of the image displayed on the display unit 102, 202 can be changed, or a user interface on the display (not shown) can be processed. This can also be used as an authentication means for identifying the observer by the image of the observer's iris. The pupil image, the image reflected from the cornea, and the iris image may be acquired using only one eye. (Numerical example) Numerical Examples 1 and 2 corresponding to the first and second embodiments, respectively, are shown below.

[0059] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d represents the distance on the optical axis of the first lens unit LU1 between the mth surface and the (m+1)th surface. Each unit is mm. However, m is the surface number counted from the pupil EP side. nd and vd represent the refractive index and Abbe number of the optical member with the d-line as the reference for the corresponding surface number. Note that the Abbe number vd of a certain material is given by the following equation, where Nd, NF, and NC are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines: νd=(Nd-1) / (NF-NC) It is expressed as:

[0060] The imaging angle means the angle that the chief ray of the light beam guided from a position on the optical axis O of the pupil EP makes with respect to the optical axis O on the second optical path RY2.

[0061] If the optical surface is aspherical, an * is added to the right of the surface number. The aspherical shape is expressed as follows, where y is the height from the optical axis in the direction perpendicular to the optical axis, r is the radius of curvature, Z is the amount of displacement from the vertex of the surface in the optical axis direction, k is the Conic coefficient, and A4, A6, A8, and A10 are the aspherical coefficients of each order: Z=(y 2 / r) / [1+{1-(1+k)(y / k) 2} 1 / 2 ]+A4·y 4 ++A6·y 6+A8·y 8 +A10·y 10 It is expressed as:

[0062] If the optical surface is a diffractive surface, ** is added to the right of the surface number. A diffractive surface gives a rotationally asymmetric phase change centered on the vertex of the surface, and when the direction from the optical axis O to the center position of the imaging surface IM in the direction perpendicular to the optical axis O (Z axis) is the Y direction (Y axis), the direction perpendicular to the Y axis and Z axis is the X axis, and Cn is the diffraction coefficient, F=Σ (i=0、j=0) C n x i y j The coefficient number n is expressed as n={(i+j) 2 +i+3j} / 2.

[0063] The eccentricities Y1 and Y2 represent the parallel eccentricity amounts in the Y-axis direction in the first and second embodiments, respectively, and are expressed in units of mm. α2 represents the tilt eccentricity around the X-axis, and the tilt angle is expressed as an angle in the YZ plane with respect to the optical axis direction (Z-axis) in which the counterclockwise direction is positive, and is expressed in units of rad.

[0064] In addition, "E±XX" in each coefficient is "×10 ±XX " means. [Numerical Example 1] The characteristics of the optical system 1 of the first embodiment are shown in the following Tables 1-1, 1-2, 1-3, 1-4, and 1-5. (Table 1-1) Surface Data JPEG2026000499000002.jpg121148

[0065] (Table 1-2) Aspheric data JPEG2026000499000003.jpg7473

[0066] (Table 1-3) Diffraction property data Diffraction order: 1st order, normalized wavelength: 870 mm JPEG2026000499000004.jpg158141

[0067] (Table 1-4) Eccentricity data JPEG2026000499000005.jpg2544

[0068] (Table 1-5) Various data JPEG2026000499000006.jpg3843

[0069] [Numerical Example 2] The characteristics of the optical system 2 of the second embodiment are shown in the following Tables 2-1, 2-2, 2-3, 2-4 and 2-5. (Table 2-1) Surface Data JPEG2026000499000007.jpg121152

[0070] (Table 2-2) Aspheric data JPEG2026000499000008.jpg6656

[0071] (Table 2-3) Diffraction property data Diffraction order: 1st order, normalized wavelength: 870 mm JPEG2026000499000009.jpg197101

[0072] (Table 2-4) Eccentricity data JPEG2026000499000010.jpg2144

[0073] (Table 2-5) Various data JPEG2026000499000011.jpg4352

[0074] The disclosure of this embodiment includes the following configuration. (Configuration 1) An optical system that forms an enlarged image of a display surface at an exit pupil and forms a reduced image of the exit pupil on an imaging surface, a first semi-transmissive reflective surface and a second semi-transmissive reflective surface arranged in this order on a first optical path from the display surface to the exit pupil; an aperture stop and an optical element arranged in order on a second optical path from the exit pupil to the image pickup surface; light from the display surface is transmitted through the first semi-transmissive reflective surface, reflected by the second semi-transmissive reflective surface, reflected by the first semi-transmissive reflective surface, transmitted through the second semi-transmissive reflective surface, and guided to the exit pupil; the light from the exit pupil is transmitted through the second semi-transmissive reflective surface, transmitted through the first semi-transmissive reflective surface, and guided to the imaging surface via the aperture stop and the optical element; 1. An optical system, wherein in a direction perpendicular to an optical axis of the optical system, the distance from the optical axis to the center of the imaging surface is equal to or less than the distance from the optical axis to the center of the aperture stop. (Configuration 2) When the distance from the optical axis to the center of the aperture stop is S1 and the distance from the optical axis to the center of the imaging surface is S2, 0.6≦S2 / S1≦1.0 The optical system according to configuration 1, characterized in that the following condition is satisfied: (Configuration 3) 3. The optical system according to configuration 1 or 2, wherein, in a direction perpendicular to the optical axis, a distance from the optical axis to an intersection point between an extension of the imaging plane and an extension of a chief ray of a light beam that is emitted from an extension of the imaging plane and an exit pupil on the optical axis and then exits the optical element is equal to or less than a distance from the optical axis to an intersection point between an extension of the imaging plane and an extension of a chief ray of a light beam that is emitted from an extension of the exit pupil and then enters the optical element. (Configuration 4) In a direction perpendicular to the optical axis, when the distance from the optical axis to the intersection of an extension of the imaging plane and an extension of the chief ray of the light beam that is incident on the optical element after being emitted from a position on the optical axis of the exit pupil and the extension of the imaging plane is L1, and the distance from the optical axis to the intersection of an extension of the chief ray of the light beam that is emitted from the optical element after being emitted from a position on the optical axis of the exit pupil and the extension of the imaging plane is L2, 0.6≦L2 / L1≦1.0 4. The optical system according to any one of the configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) Let θ be the angle [rad] formed by a first line parallel to the optical axis and an extension of the chief ray of the light beam that is emitted from the exit pupil at a position on the optical axis and then emitted from the optical element, and let the sign of the angle be positive when the intersection of the extension of the chief ray and the extension of the optical axis in a direction parallel to the optical axis is on the imaging plane side of the optical element, and let the sign of the angle be negative when the intersection is on the exit pupil side of the optical element, 0≦θ≦π / 3 5. The optical system according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) 6. The optical system according to any one of configurations 1 to 5, wherein a lens surface included in the first optical system has a surface shape that is rotationally symmetric with respect to the optical axis. (Configuration 7) 8. The optical system according to any one of configurations 1 to 7, wherein the optical element has a surface shape that is rotationally asymmetric with respect to the optical axis of the second lens unit. (Configuration 8) 8. The optical system according to any one of configurations 1 to 7, wherein the optical element has a diffractive surface. (Configuration 9) 9. An optical system according to any one of configurations 1 to 8, wherein the second optical system has a plurality of diffractive surfaces. (Configuration 10) 10. The optical system according to configuration 9, wherein the distances from the optical axis to the centers of the respective optically effective areas of the plurality of diffractive surfaces in a direction perpendicular to the optical axis are different from one another. (Configuration 11) 9. The optical system according to any one of configurations 1 to 8, wherein the optical element has a refractive surface. (Configuration 12) 12. The optical system according to any one of configurations 1 to 11, wherein the second semi-transmissive reflective surface is a surface provided on a polarization-selective reflective polarizing element. (Configuration 13) 13. The optical system according to any one of configurations 1 to 12, wherein the normal to the display surface and the normal to the imaging surface are parallel to each other. (Configuration 14) 14. The optical system according to any one of configurations 1 to 13, wherein an extension of the display surface and an extension of the imaging surface are in the same plane. (Configuration 15) 15. The optical system according to any one of configurations 1 to 14, further comprising a circular polarization conversion element disposed on the display surface side of the first semi-transmissive reflective surface. (Configuration 16) 16. The optical system according to configuration 15, wherein the circular polarization conversion element comprises a linear polarizer and a λ / 4 plate. (Configuration 17) 17. The optical system of claim 16, wherein the linear polarizer is disposed only in the first optical path. (Configuration 18) a third unit that guides light from a light-emitting surface of the light-emitting element to the exit pupil; The optical system described in any one of configurations 1 to 17, characterized in that the optical system includes a third optical path in which light from the light-emitting surface passes through the third unit, passes through the first semi-transmissive reflective surface, passes through the second semi-transmissive reflective surface, and is guided to the exit pupil. (Configuration 19) 19. The optical system according to configuration 18, wherein the normal to the display surface, the normal to the imaging surface, and the normal to the light-emitting surface are parallel to one another. (Configuration 20) 20. The optical system according to configuration 18 or 19, wherein the extension of the display surface, the extension of the imaging surface, and the extension of the light-emitting surface are in the same plane. (Configuration 21) an optical system according to any one of configurations 1 to 17; a display element having the display surface; and an imaging element having the imaging surface. (Configuration 22) an optical system according to any one of configurations 18 to 20; a display element having the display surface; an imaging element having the imaging surface; An observation device comprising: a light-emitting element having the light-emitting surface.

[0075] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. (Explanation of symbols) 1 Optical system G21 Third lens (optical element) G22 Fourth lens (optical element) HM1 First semi-transparent reflective surface HM2 Second semi-transparent reflective surface IM imaging plane LU1 First lens unit (first optical system) LU2 Second lens unit (second optical system) PNL display surface SP aperture stop

Claims

1. An optical system that forms an enlarged image of a display surface at an exit pupil and forms a reduced image of the exit pupil on an imaging surface, a first semi-transmissive reflective surface and a second semi-transmissive reflective surface arranged in this order on a first optical path from the display surface to the exit pupil; an aperture stop and an optical element arranged in order on a second optical path from the exit pupil to the image pickup surface; light from the display surface is transmitted through the first semi-transmissive reflective surface, reflected by the second semi-transmissive reflective surface, reflected by the first semi-transmissive reflective surface, transmitted through the second semi-transmissive reflective surface, and guided to the exit pupil; the light from the exit pupil is transmitted through the second semi-transmissive reflective surface, transmitted through the first semi-transmissive reflective surface, and guided to the imaging surface via the aperture stop and the optical element; 1. An optical system, wherein in a direction perpendicular to an optical axis of the optical system, the distance from the optical axis to the center of the imaging surface is equal to or less than the distance from the optical axis to the center of the aperture stop.

2. In a direction perpendicular to the optical axis, when the distance from the optical axis to the center of the aperture stop is S1 and the distance from the optical axis to the center of the imaging surface is S2, 0.6≦S2 / S1≦1.0 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. 3. The optical system according to claim 1, wherein, in a direction perpendicular to the optical axis, a distance from the optical axis to an intersection point between an extension of the imaging plane and an extension of a chief ray of a light beam that is emitted from the optical element after being emitted from a position on the optical axis of the exit pupil is equal to or less than a distance from the optical axis to an intersection point between an extension of the imaging plane and an extension of a chief ray of a light beam that is incident on the optical element after being emitted from a position on the optical axis of the exit pupil.

4. In a direction perpendicular to the optical axis, when the distance from the optical axis to the intersection point between the extension of the imaging plane and the extension of the chief ray of the light beam that is incident on the optical element after being emitted from a position on the optical axis of the exit pupil is defined as L1, and the distance from the optical axis to the intersection point between the extension of the imaging plane and the extension of the chief ray of the light beam that is emitted from the optical element after being emitted from a position on the optical axis of the exit pupil is defined as L2, 0.6≦L2 / L1≦1.0 3. The optical system according to claim 1, wherein the following condition is satisfied:

5. Let θ be the angle [rad] formed by a first line parallel to the optical axis and an extension of a chief ray of a light beam that is emitted from a position on the optical axis of the exit pupil and then emitted from the optical element, and let the sign of the angle be positive when the intersection of the extension of the chief ray and the extension of the optical axis in a direction parallel to the optical axis is on the imaging plane side of the optical element, and let the sign of the angle be negative when the intersection is on the exit pupil side of the optical element, 0≦θ≦π / 3 3. The optical system according to claim 1, wherein the following condition is satisfied:

6. 3. The optical system according to claim 1, wherein a lens surface included in the first optical system has a surface shape that is rotationally symmetric with respect to the optical axis.

7. 3. The optical system according to claim 1, wherein the optical element has a surface shape that is rotationally asymmetric with respect to the optical axis of the second optical system.

8. 3. The optical system according to claim 1, wherein the optical element has a diffractive surface.

9. 3. The optical system according to claim 1, wherein the second optical system has a plurality of diffractive surfaces.

10. 10. The optical system according to claim 9, wherein the distances from the optical axis to the centers of the respective optically effective areas of the plurality of diffractive surfaces are different from one another in a direction perpendicular to the optical axis.

11. 3. The optical system according to claim 1, wherein the optical element has a refractive surface.

12. 3. The optical system according to claim 1, wherein the second semi-transmissive reflective surface is a surface provided on a polarization-selective reflective polarizing element.

13. 3. The optical system according to claim 1, wherein a normal to the display surface and a normal to the imaging surface are parallel to each other.

14. 3. The optical system according to claim 1, wherein an extension of the display surface and an extension of the imaging surface are in the same plane.

15. 3. The optical system according to claim 1, further comprising a circular polarization conversion element disposed on the display surface side of the first semi-transmissive reflective surface.

16. 16. The optical system according to claim 15, wherein the circular polarization conversion element comprises a linear polarizer and a λ / 4 plate.

17. The optical system of claim 15 , wherein the linear polarizer is disposed only in the first optical path.

18. a third unit that guides light from a light-emitting surface of the light-emitting element to the exit pupil; 3. The optical system according to claim 1, further comprising a third optical path along which light from the light-emitting surface passes through the third unit, passes through the first semi-transmissive reflective surface, passes through the second semi-transmissive reflective surface, and is guided to the exit pupil.

19. The optical system of claim 18 , wherein the normal to the display surface, the normal to the imaging surface, and the normal to the light-emitting surface are parallel to one another.

20. The optical system according to claim 18 , wherein an extension of the display surface, an extension of the imaging surface, and an extension of the light-emitting surface are in the same plane.

21. The optical system according to claim 1 or 2; a display element having the display surface; and an imaging element having the imaging surface.

22. an optical system according to claim 18; a display element having the display surface; an imaging element having the imaging surface; An observation device comprising: a light-emitting element having the light-emitting surface.

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