Optical system and observation apparatus having the same

Abstract

To provide a compact and thin optical system and an observation device having the same, while possessing a wide field of view and high optical performance. [Solution] The optical system is an optical system that forms an enlarged image of the display surface of an image display element, and has a first semi-transparent reflective surface and a second semi-transparent reflective surface arranged in order from the exit pupil side to the display surface side, and the optical system includes a first optical path through which light from the display surface passes through the second semi-transparent reflective surface, is reflected by the first semi-transparent reflective surface, is reflected by the second semi-transparent reflective surface, passes through the first semi-transparent reflective surface again, and is guided to the exit pupil, and a second optical path through which light from the exit pupil side passes through the first semi-transparent reflective surface, passes through the second semi-transparent reflective surface again, and is guided to the image sensor.

Description

Technical Field

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

Background Art

[0002] In recent years, an observation device is known that enlarges an original image displayed on an image display element through an eyepiece optical system and has functions such as personal authentication using an iris image and gaze detection using a pupil image, which are acquired by a photographing optical system that photographs the pupil of an observer. Patent Document 1 discloses a configuration in which the same optical system using a free-form prism is used for an observation optical path for image viewing and a photographing optical path for gaze tracking.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration of Patent Document 1, when trying to expand the viewing angle of the eyepiece optical system, the size of the free-form prism increases, and the thickness of the optical system increases.

[0005] Conventionally, as a configuration capable of realizing thinning while expanding the viewing angle, a configuration (triple-pass optical system) that folds the observation optical path on the optical axis using two half mirrors is known. When arranging the photographing optical system in the triple-pass optical system, as shown in FIG. 7, a configuration in which the photographing optical system is arranged outside the eyepiece optical system can be considered. However, in such a configuration, since the lens outer diameter of the wide-viewing-angle eyepiece optical system is large, the photographing angle of the pupil of the observer becomes too large, and separation between the pupil image and the iris image due to eyelid and eyeball rotation occurs.

[0006] The present invention aims to provide a compact and thin optical system and an observation device having the same, while possessing a wide field of view and high optical performance. [Means for solving the problem]

[0007] An optical system as one aspect of the present invention is an optical system for forming an enlarged image of the display surface of an image display element, and has a first semi-transparent reflective surface and a second semi-transparent reflective surface arranged in order from the exit pupil side to the display surface side, and the optical system includes a first optical path through which light from the display surface passes through the second semi-transparent reflective surface, is reflected by the first semi-transparent reflective surface, is reflected by the second semi-transparent reflective surface, passes through the first semi-transparent reflective surface again, and is led to the exit pupil, and a second optical path through which light from the exit pupil side passes through the first semi-transparent reflective surface, is passed through the second semi-transparent reflective surface again, and is led to the image sensor, and when Ltp is the distance on the optical axis of the first optical path from the surface closest to the exit pupil to the second semi-transparent reflective surface, and Cx is the distance on the optical axis of the first optical path from the surface closest to the exit pupil to the center of the image sensor, 0.5 <Cx / Ltp<1.5 It is characterized by satisfying the following conditional expression. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a compact and thin optical system and an observation device having the same, while possessing a wide field of view and high optical performance. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of the optical system of Example 1. [Figure 2] This is a cross-sectional view of the optical system of Example 2. [Figure 3] This is a cross-sectional view of the optical system of Example 3. [Figure 4] This is a cross-sectional view of the optical system of Example 4. [Figure 5] This is a cross-sectional view of the optical system of Example 5. [Figure 6] This diagram illustrates a configuration that utilizes polarization in the eyepiece optical system. [Figure 7]This is a cross-sectional view of the optical system of the comparative example. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. In each drawing, the same reference numeral is used for identical components, and redundant descriptions are omitted.

[0011] Figures 1 to 5 are cross-sectional views of the optical systems of Examples 1 to 5, respectively. The optical systems of each example are used in observation devices such as head-mounted displays (HMDs) and form an enlarged image of the image display surface (display surface) ID of an image display element such as an LCD.

[0012] In each cross-sectional view, the left side is the exit pupil side (observation side), and the right side is the image display surface ID side. EYE represents the observer's eye. SP represents the exit pupil (pupil surface). CAM represents the camera equipped with an image sensor.

[0013] The optical system of each embodiment includes an observation optical path (first optical path) that guides light from the image display surface ID to the exit pupil SP, and a photographing optical path (second optical path) that guides light from the side of the exit pupil SP to the imaging device. The optical system of each embodiment has a first semi-transmissive reflecting surface HM1 and a second semi-transmissive reflecting surface HM2 that are arranged in order from the side of the exit pupil SP to the side of the image display surface ID. Further, the optical system of each embodiment has an eyepiece optical system for magnifying and observing the image displayed on the image display surface ID, and a photographing optical system that forms an image of light from the side of the exit pupil SP on the imaging device. The eyepiece optical system is a coaxial optical system that takes the observation optical path. In the observation optical path, the light from the image display surface ID passes through the second semi-transmissive reflecting surface HM2, is reflected by the first semi-transmissive reflecting surface HM1, is reflected by the second semi-transmissive reflecting surface HM2, passes through the first semi-transmissive reflecting surface HM1, and is guided to the exit pupil SP. The photographing optical system is an optical system that takes a photographing optical path using a part of the eyepiece optical system. In the photographing optical path, the light from the side of the exit pupil SP passes through the first semi-transmissive reflecting surface HM1, passes through the second semi-transmissive reflecting surface HM2, and is guided to the imaging device. In the photographing optical path, the light from the side of the exit pupil SP is not reflected by the first semi-transmissive reflecting surface HM1 and the second semi-transmissive reflecting surface HM2.

[0014] With the above configuration, the observation optical path has a triple-pass configuration, and the photographing optical path has a single-pass configuration that passes through at least a part of the eyepiece optical system. Thereby, while arranging an eyepiece optical system having a triple-pass configuration that can achieve a thin profile while having a wide viewing angle, by arranging the photographing optical system on the side of the image display surface ID, it is possible to reduce the offset amount in the direction perpendicular to the optical axis of the photographing optical path of the imaging device. That is, it is possible to reduce the photographing angle on the side of the exit pupil SP in the photographing optical system.

[0015] By having the above-described configuration, it is possible to realize a small and thin optical system while having a wide viewing angle and high optical performance. <OO00091>

[0016] Hereinafter, a preferable configuration that the optical system of each embodiment satisfies will be described. <OO000SS> It is preferable to arrange the refraction region RR outside the optically effective region of the observation optical path and inside the optically effective region of the imaging optical path. Here, the outside of the optically effective region means the optically ineffective region. Also, the inside of the optically effective region means within the optically effective region. In the imaging optical path, light from the side of the exit pupil SP passes through the first semi-transmissive reflecting surface HM1, passes through the second semi-transmissive reflecting surface HM2, passes through the refraction region RR, and is guided to the imaging element. Thereby, it becomes possible to arrange the imaging element closer to the optical axis of the eyepiece optical system, and it is possible to reduce the imaging angle on the side of the exit pupil SP in the imaging optical system. In the optical systems of each embodiment, the refraction region RR is a refracting surface.

[0018] The refracting surface is preferably rotationally symmetric with respect to the optical axis of the observation optical path. Thereby, in the eyepiece optical system which is a coaxial optical system, processing of the refracting surface is easy. Also, when a configuration using polarization described later is adopted using a resin material as the lens constituting the eyepiece optical system, management of form birefringence becomes important. A lens having a rotationally symmetric shape is advantageous for reducing form birefringence.

[0019] The refracting surface is preferably a plane. Thereby, in the imaging optical system, it is possible to reduce the aberration generated at the refracting surface.

[0020] In the imaging optical path, it is preferable to arrange a rotationally asymmetric optical element OE on the side of the imaging element with respect to the refracting surface. Thereby, in the imaging optical system, it is possible to correct the aberration generated in the observation optical path which shares a part with the eyepiece optical system, and it is possible to image the side of the exit pupil SP with higher definition. Also, it is preferable that the optically effective surface on the side of the imaging element of the optical element OE is a plane. Thereby, it is possible to reduce the aberration generated at the optically effective surface on the side of the imaging element of the optical element OE. Also, it is preferable to join the optical element OE to the refracting surface. Thereby, it is possible to realize a stable configuration in holding the optical element OE and the like.

[0021] In the optical systems of each embodiment, it is preferable that the first semi-transparent reflective surface HM1 be a plane. By adopting this configuration and appropriately arranging the refractive region RR, it is possible to reduce aberrations occurring in the observation light path that is partially shared with the eyepiece optical system in the imaging optical system. For example, in the configuration shown in Figure 5, the portion of the imaging optical system shared with the eyepiece optical system acts as a parallel plate.

[0022] The first semi-transparent reflective surface HM1 is preferably a surface provided on a polarization-selective reflective polarizing element. Furthermore, it is preferable to place a circular polarization conversion element on the image display surface ID side of the second semi-transparent reflective surface HM2. The circular polarization conversion element preferably consists of a linear polarizer and a λ / 4 plate. With this configuration, by adopting a configuration that utilizes polarization as described later, it is possible to block the single-pass optical path in the eyepiece optical system and realize high-quality virtual image observation. The linear polarizer is preferably placed only in the observation optical path. This results in a configuration in which the linear polarizer is not placed in the imaging optical path, making it possible to avoid a decrease in light intensity due to absorption by the polarizing element.

[0023] The optical system of each embodiment preferably consists of a single cemented lens. This makes it possible to achieve sufficient aberration correction while also enabling a thinner design, including the lens barrel.

[0024] The optical system of each embodiment preferably satisfies the following condition (1).

[0025] 0.5 <Cx / Ltp<1.5 (1) Here, Ltp is the distance along the optical axis of the observation light path from the surface closest to the exit pupil SP to the second semi-transparent reflective surface HM2. Cx is the distance along the optical axis of the observation light path from the surface closest to the exit pupil SP to the center of the image sensor.

[0026] Condition (1) specifies the arrangement of the imaging optical system. If the value falls below the lower limit of condition (1), it becomes difficult to reduce the imaging angle on the exit pupil SP side of the imaging optical system, or the thickness of the eyepiece optical system increases, which is undesirable. If the value exceeds the upper limit of condition (1), it is possible to reduce the imaging angle on the exit pupil SP side of the imaging optical system, but the thickness of the imaging device CAM becomes too large.

[0027] Furthermore, it is preferable that the numerical range of conditional expression (1) be the numerical range of conditional expression (1a) below.

[0028] 0.7 <Cx / Ltp< 1.3 (1a) Furthermore, it is even more preferable to set the numerical range of condition (1) to the numerical range of condition (1b) below.

[0029] 0.8 <Cx / Ltp<1.1 (1b) The following describes a configuration utilizing polarization, referring to Figures 1 and 6. Figure 6 is a diagram illustrating a configuration that utilizes polarization in the eyepiece optical system.

[0030] The first semi-transparent reflective surface HM1 is formed by arranging a polarization-selective semi-transparent semi-reflective element (PBS) and a first λ / 4 plate (QWP1) in order from the exit pupil SP. A second semi-transparent reflective surface HM2 is formed by arranging a half mirror, for example, formed by dielectric multilayer film or metal deposition. A second λ / 4 plate (QWP2) and a linear polarizer (POL) are arranged between the half mirror (second semi-transparent reflective surface HM2) and the image display surface ID.

[0031] A polarization-selective semi-transparent reflecting element (PBS) is an element configured to reflect linearly polarized light polarized in the same direction as when it passed through a linear polarizer (POL), and to transmit linearly polarized light perpendicular to that direction. A polarization-selective semi-transparent reflecting element (PBS) is, for example, a wire grid polarizer, where the wire grid forming surface functions as a semi-transparent semi-reflective surface. Furthermore, the first λ / 4 (QWP1) and the second λ / 4 plate (QWP1) are arranged with their respective slow axes tilted at 90°. In addition, the first λ / 4 (QWP1) is arranged with its slow axis tilted at 45° with respect to the polarization transmission axis of the linear polarizer (POL).

[0032] Light emitted from the image display surface ID becomes linearly polarized by the linear polarizer (POL), then becomes circularly polarized by the second λ / 4 plate (QWP2), and is incident on the half mirror (second semi-transparent reflective surface HM2). A portion of the light that reaches the half mirror (second semi-transparent reflective surface HM2) is reflected and becomes circularly polarized in the opposite direction, returning to the second λ / 4 plate (QWP2). The reverse-polarized circularly polarized light that returns to the second λ / 4 plate (QWP2) is polarized by the second λ / 4 plate (QWP2) in a direction perpendicular to the direction in which it first passed through the linear polarizer (POL), and returns to the linear polarizer (POL) as linearly polarized light, which is absorbed by the linear polarizer (POL).

[0033] Furthermore, some of the light that reaches the half-mirror (second semi-transparent reflective surface HM2) passes through the half-mirror (second semi-transparent reflective surface HM2). Subsequently, it is polarized in the same direction as when it passed through the linear polarizer (POL) by the first λ / 4 plate (QWP1), and then incident on the polarization-selective semi-transparent reflective element (PBS). The linearly polarized light, polarized in the same direction as when it passed through the linear polarizer (POL), is reflected by the polarization selectivity of the polarization-selective semi-transparent reflective element (PBS). The light reflected by the polarization-selective semi-transparent reflective element (PBS) is then polarized in the opposite direction to when it was first polarized by the second λ / 4 plate (QWP2) by the first λ / 4 plate (QWP1), and then incident on the half-mirror (second semi-transparent reflective surface HM2).

[0034] Light reflected by the half-mirror (second semi-transparent reflective surface HM2) becomes circularly polarized in the opposite direction to the light before reflection. Then, it is incident on the first λ / 4 plate (QWP1) and becomes linearly polarized in a direction perpendicular to the direction in which it first passed through the linear polarizer (POL), before being incident on the polarization-selective semi-transparent reflective element (PBS).

[0035] Linearly polarized light, polarized in a direction perpendicular to the direction in which it passed through the linear polarizer (POL), is transmitted through the polarization-selective semi-transparent reflecting element (PBS) due to the polarization selectivity of the PBS and guided to the exit pupil SP.

[0036] As described above, only light that passes through the half-mirror (second semi-transparent reflective surface HM2), is reflected by the polarization-selective semi-transparent reflective element (PBS), is reflected again by the half-mirror (second semi-transparent reflective surface HM2), and passes through the polarization-selective semi-transparent reflective element (PBS) is guided to the exit pupil SP. [Example 1] The observation apparatus of this embodiment will be described below with reference to Figure 1.

[0037] The observation device of this embodiment has a first lens G1, a second lens G2, and a third lens G3 arranged in order from the exit pupil SP side to the image display surface ID side. A first semi-transparent reflective surface HM1 is provided on the exit pupil SP side of the first lens G1. A second semi-transparent reflective surface HM2 is provided on the exit pupil SP side of the second lens G2. The observation device of this embodiment also has a camera CAM equipped with an image display element and an image sensor. The observation device of this embodiment also has an eyepiece optical system and a imaging optical system which are coaxial optical systems with a diagonal field of view of about 58 degrees. The aspect ratio of the image display surface ID is 4:3. The effective light beam in the observation light path is shown by a dotted line, and the effective light beam in the imaging light path is shown by a solid line.

[0038] In the observation light path, light from the image display surface ID passes through the second semi-transparent reflective surface HM2, is reflected by the first semi-transparent reflective surface HM1, is reflected again by the second semi-transparent reflective surface HM2, passes through the first semi-transparent reflective surface HM1, and is guided to the exit pupil SP. By adopting a triple-pass configuration for the eyepiece optical system, it is possible to achieve both a wide field of view and a thin profile in the observation device.

[0039] In the imaging light path, the light passes through the first semi-transparent reflective surface HM1, then through the second semi-transparent reflective surface HM2, and is guided to the image sensor. This makes it possible to reduce the imaging angle on the side of the exit pupil SP in the imaging optical system.

[0040] Furthermore, the refractive region RR is positioned outside the optically effective area of ​​the observation light path and inside the optically effective area of ​​the imaging light path. This makes it possible to position the camera CAM (image sensor) closer to the optical axis of the eyepiece optical system, and further reduces the imaging angle on the side of the exit pupil SP in the imaging optical system. In this embodiment, the refractive region RR is a sphere that is rotationally symmetric with respect to the optical axis of the observation light path. [Example 2] The observation apparatus of this embodiment will be described below with reference to Figure 2.

[0041] The basic configuration of the observation apparatus in this embodiment is the same as that of the observation apparatus in Embodiment 1. This embodiment differs from Embodiment 1 in the configuration of the eyepiece optical system and the arrangement of the imaging optical system. In this embodiment, only the configurations that differ from Embodiment 1 will be described, and the configurations that are the same as those in Embodiment 1 will not be described.

[0042] The observation device of this embodiment has a first lens G1 and a second lens G2 arranged in order from the exit pupil SP side to the image display surface ID side. A first semi-transparent reflective surface HM1 is provided on the exit pupil SP side of the first lens G1. A second semi-transparent reflective surface HM2 is provided on the exit pupil SP side of the second lens G2.

[0043] The eyepiece optical system in this embodiment has a diagonal field of view of approximately 80 degrees and is composed of a single cemented lens.

[0044] The refractive region RR is positioned outside the optically effective area of ​​the observation light path and inside the optically effective area of ​​the imaging light path. In this embodiment, the refractive region RR is a conical surface that is rotationally symmetric with respect to the optical axis of the observation light path. [Example 3] The observation apparatus of this embodiment will be described below with reference to Figure 3.

[0045] The basic configuration of the observation apparatus in this embodiment is the same as that of the observation apparatus in Embodiment 2. In this embodiment, the configuration of the refractive region RR differs from that of Embodiment 2. In this embodiment, only the configuration that differs from that of Embodiment 2 will be described, and the configuration that is the same as that of Embodiment 2 will not be described.

[0046] In this embodiment, the refractive region RR is a plane that is rotationally symmetric with respect to the optical axis of the observation light path. By making the refractive region RR a plane, it is possible to reduce the asymmetric aberration, particularly the as component, that occurs due to the refraction of the refractive region RR. [Example 4] The observation apparatus of this embodiment will be described below with reference to Figure 4.

[0047] The basic configuration of the observation device in this embodiment is the same as that of the observation device in Embodiment 2. This embodiment differs from Embodiment 2 in that a rotationally asymmetric optical element OE is placed on the side of the image sensor in the refractive region RR. In this embodiment, only the configurations that differ from Embodiment 2 will be described, and the configurations that are the same as those in Embodiment 2 will not be described.

[0048] The optical element OE plays a role in correcting the asymmetric aberrations that occur in the refractive region RR, which is a conical surface. Furthermore, by joining the optical element OE to the refractive region RR and configuring the surface of the optical element OE on the side facing the image sensor as a flat plane, it is possible to effectively correct the asymmetric aberrations, especially the as component, that remain in the imaging optical system. [Example 5] The observation apparatus of this embodiment will be described below with reference to Figure 5.

[0049] The basic configuration of the observation apparatus in this embodiment is the same as that of the observation apparatus in Embodiment 1. This embodiment differs from Embodiment 1 in the configuration of the eyepiece optical system and the arrangement of the imaging optical system. In this embodiment, only the configurations that differ from Embodiment 1 will be described, and the configurations that are the same as those in Embodiment 1 will not be described.

[0050] The observation device of this embodiment has first to seventh lenses G1 to G7 arranged sequentially from the exit pupil SP side to the image display surface ID side. A first semi-transparent reflective surface HM1 is provided on the exit pupil SP side of the first lens G1. A second semi-transparent reflective surface HM2 is provided on the exit pupil SP side of the second lens G2.

[0051] The eyepiece optical system of this embodiment has a diagonal field of view of approximately 69 degrees and is configured to form an intermediate image.

[0052] The first semi-transparent reflective surface HM1 is planar, and the first lens G1 and the second lens G2 are constructed as cemented lenses made of the same material. This configuration allows the shared portion of the eyepiece optical system and the imaging optical system to be considered a parallel plate, thus minimizing the impact on aberrations. In this case, it is not necessary to design a dedicated camera CAM for photographing the exit pupil SP; a general-purpose camera module can be used.

[0053] As described above, the eyepiece optical system of this embodiment is constructed with the first lens G1 and the second lens G2 as a cemented lens made of the same material and is considered as a parallel plate. Furthermore, the semi-transparent reflective surface HM1 on the exit pupil SP side of the first lens G1 is arranged as a polarization-selective semi-transparent semi-reflective element and a λ / 4 plate. In addition, a λ / 4 wave plate is placed on the side of the image display surface IP of the second lens G2, and the reflective surface (the ninth surface in numerical embodiment 3) is arranged as a planar combiner consisting of a polarization-selective semi-transparent semi-reflective element. With this configuration, it is possible to realize a so-called optical see-through type eyepiece optical system in which ambient light passes through the cemented lens in a single pass and is observed at approximately 1:1 magnification, and the image light from the image display element passes through the cemented lens in a triple pass and is observed at magnification.

[0054] Numerical Example 1 corresponding to Example 1, Numerical Example 2 corresponding to Examples 2 to 4, and Numerical Example 3 corresponding to Example 3 are shown below.

[0055] In the surface data for each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (distance along the optical axis) between the m-th surface and the (m+1)-th surface. Here, m is the surface number counted from the exit pupil SP side. Also, nd represents the refractive index of each optical element with respect to the d line, and νd represents the Abbe number of the optical element. Note that the Abbe number νd of a certain material is given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0056] The viewing angle is the viewing angle in the direction of the shorter side of the image display surface ID.

[0057] Furthermore, if the optical surface is aspherical, the sign * is added to the right of the surface number. The aspherical shape is defined as follows, where X is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis perpendicular to the optical axis, R is the paraaxial radius of curvature, K is the cone constant, and A4, A6, A8, and A10 are the aspherical coefficients of their respective orders. X=( h 2 / R) / [1+{1-(1+K)(h / R) 2} 1 / 2 +A4·h 4 +A6·h 6 +A8·h 8 +A10·h 10 This is expressed as follows. Note that "e±XX" in each aspherical coefficient is "×10± XX It means "...".

[0058] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd Effective diameter (Y,Z) 1 (aperture) ∞ 18.00 4.0 2 ∞ 0.20 1.50000 50.0 27.5 3 ∞ 3.00 1.53000 55.9 27.5 4* -38.483 1.87 (Reflective surface: HM2) 27.5 5 -38.005 -1.87 (Reflective surface: HM1) 27.5 6* -38.483 -3.00 1.53000 55.9 27.5 7 ∞ 3.00 27.5 8* -38.483 1.87 27.5 9 -38.005 1.83 1.63600 23.9 27.5 10* 99.896 0.85 23.5 11 ∞ 0.20 1.50000 50.0 (12.6,21.0) 12 ∞ 3.00 1.48749 70.2 21.0 13 -30.050 0.76 21.0 14 ∞ 0.40 1.51633 64.1 (8.2,11.0) 15 ∞ 0.00 (8.2, 11.0) Image plane ∞ Aspherical data Side 4 K = 0.00000e+00 A 4= 1.14783e-05 A 6= 8.12048e-08 A 8=-3.42503e-10 A10 = 1.00372e-12 Page 6 K = 0.00000e+00 A 4= 1.14783e-05 A 6= 8.12048e-08 A 8=-3.42503e-10 A10 = 1.00372e-12 Side 8 K = 0.00000e+00 A 4= 1.14783e-05 A 6= 8.12048e-08 A 8=-3.42503e-10 A10 = 1.00372e-12 Side 10 K = 0.00000e+00 A 4=-2.17485e-04 A 6= 1.14074e-06 A 8=-3.03928e-09 A10 = 2.89322e-12 Various data Focal length 12.97 Pupil diameter 4.00 Viewing angle 17.20 Lens length: 12.11 Single lens data Lens starting plane, focal length SP 1 0.00 POL 2 0.00 G1 3 72.61 G2 9 -43.07 POL 11 0.00 G3 12 61.64 CG 14 0.00 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd Effective diameter 1 (aperture) ∞ 18.00 4.0 2 ∞ 0.20 1.50000 50.0 38.0 3 ∞ 7.00 1.53000 55.9 38.0 4* -41.951 -7.00 (Reflective surface: HM2) 38.0 5 ∞ 7.00 (Reflective surface: HM1) 38.0 6* -41.951 2.40 1.63600 23.9 38.0 7* -73.131 0.95 27.0 8 ∞ 0.30 1.50000 50.0 30.0 9 ∞ 0.30 1.50000 50.0 30.0 10 ∞ 1.25 30.0 11 ∞ 0.70 1.51633 64.1 30.0 12 ∞ 0.00 30.0 Image plane ∞ Aspherical data Side 4 K = 0.00000e+00 A 4=-2.58220e-06 A 6= 1.47199e-08 A 8=-5.32418e-11 A10 = 7.50680e-14 Page 6 K = 0.00000e+00 A 4=-2.58220e-06 A 6= 1.47199e-08 A 8=-5.32418e-11 A10 = 7.50680e-14 Side 7 K = 0.00000e+00 A 4= 1.82030e-04 A 6=-1.33313e-06 A 8= 2.80530e-09 Various data Focal length 13.50 Pupil diameter 4.00 Viewing angle 40.00 Lens length: 13.10 Single lens data Lens starting plane, focal length SP 1 0.00 POL 2 0.00 G1 3 79.15 G2 6 -159.48 POL 8 0.00 POL 9 0.00 CG 11 0.00 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd Effective diameter (Y,Z) 1 (aperture) ∞ 19.00 4.0 2 ∞ 0.20 1.50000 50.0 43.0 3 ∞ 4.38 1.54400 56.0 43.0 4* -80.834 -4.38 (Reflective surface: HM2) 43.0 5 ∞ 4.38 (Reflective surface: HM1) 43.0 6* -80.834 1.50 1.54400 56.0 43.0 7 ∞ 0.20 1.50000 50.0 (32.0,43.0) 8 ∞ 15.47 (32.0, 43.0) 9 ∞ -14.80 (reflective surface) (21.0,17.0) 10 98.671 38.80 (reflective surface) (12.0,15.0) 11 16.049 3.47 1.95375 32.3 14.5 12 -69.698 2.09 14.0 13 -19.195 2.01 1.85150 40.8 12.7 14 -11.340 1.20 1.95906 17.5 12.5 15 -65.988 2.59 13.4 16 12.157 6.50 1.65160 58.5 15.7 17 -23.061 0.66 14.7 18* 63.474 3.50 1.63600 23.9 12.8 19* 20.422 3.55 12.1 20 ∞ 0.70 1.51633 64.1 13.7 21 ∞ 0.00 13.7 Image plane ∞ Aspherical data Side 4 K = 0.00000e+00 A 4= 7.33649e-07 A 6=-1.66877e-09 A 8= 5.28772e-12 A10 = -5.05759e-15 Page 6 K = 0.00000e+00 A 4= 7.33649e-07 A 6=-1.66877e-09 A 8= 5.28772e-12 A10 = -5.05759e-15 Page 18 K = 0.00000e+00 A 4=-5.74635e-04 Page 19 K = 0.00000e+00 A 4= 5.49158e-05 A 6= 6.48873e-06 Various data Focal length -9.05 Pupil diameter 4.00 Viewing angle 22.90 Lens length: 129.38 Single lens data Lens starting plane, focal length SP 1 0.00 POL 2 0.00 G1 3 148.59 G2 6 -148.59 POL 7 0.00 G3 11 13.95 G4 13 29.12 G5 14 -14.43 G6 16 13.18 G7 18 -48.89 CG 20 0.00 The various values ​​in each numerical example are summarized in Table 1 below.

[0059] [Table 1]

[0060] Although preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of its gist. [Explanation of symbols]

[0061] ID image display surface (display surface) HM1 First semi-transparent semi-reflective surface HM2 Second semi-transparent semi-reflective surface SP exit pupil

Claims

1. An optical system for forming an enlarged image of the display surface of an image display element, It has a first semi-transparent reflective surface and a second semi-transparent reflective surface arranged in order from the exit pupil side to the display surface side, The optical system described above is Light from the display surface passes through the second semi-transparent reflective surface, is reflected by the first semi-transparent reflective surface, is reflected by the second semi-transparent reflective surface, passes through the first semi-transparent reflective surface, and is guided to the exit pupil in a first optical path, The light from the side of the exit pupil passes through the first semi-transparent reflective surface, passes through the second semi-transparent reflective surface, and includes a second optical path that is guided to the image sensor. When Ltp is the distance along the optical axis of the first optical path from the surface closest to the exit pupil to the second semi-transparent reflective surface, and Cx is the distance along the optical axis of the first optical path from the surface closest to the exit pupil to the center of the image sensor, 0.5<Cx / Ltp<1.5 An optical system characterized by satisfying the following conditional equation.

2. The optical system according to claim 1, further comprising a refractive region located outside the optically effective region of the first optical path and inside the optically effective region of the second optical path.

3. The optical system according to claim 2, characterized in that, in the second optical path, light from the side of the exit pupil passes through the first semi-transparent reflective surface, passes through the second semi-transparent reflective surface, passes through the refractive region, and is guided to the image sensor.

4. The optical system according to claim 3, characterized in that the refractive region is a refractive surface.

5. The optical system according to claim 4, characterized in that the refractive surface is rotationally symmetric with respect to the optical axis of the first optical path.

6. The optical system according to claim 4 or 5, characterized in that the refractive surface is planar.

7. The optical system according to any one of claims 4 to 6, further comprising a rotationally asymmetric optical element positioned on the side of the image sensor from the refractive surface in the second optical path.

8. The optical system according to claim 7, characterized in that the optically effective surface of the optical element on the side facing the image sensor is planar.

9. The optical system according to claim 7 or 8, characterized in that the optical element is joined to the refractive surface.

10. The optical system according to any one of claims 2 to 9, characterized in that the first semi-transparent reflective surface is planar.

11. The optical system according to any one of claims 2 to 9, characterized in that the first semi-transparent reflective surface is a surface provided on a polarization-selective reflective polarizing element.

12. The optical system according to any one of claims 2 to 11, further comprising a circular polarization conversion element disposed on the display surface side of the second semi-transparent reflective surface.

13. The optical system according to claim 12, characterized in that the circular polarization conversion element comprises a linear polarizer and a λ / 4 plate.

14. The optical system according to claim 13, characterized in that the linear polarizer is arranged only within the first optical path.

15. The optical system according to any one of claims 1 to 14, characterized in that the optical system comprises a single cemented lens.

16. The eyepiece optical system, which is a coaxial optical system taking the first optical path, The optical system according to any one of claims 1 to 15, further comprising a photographic optical system that takes the second optical path.

17. The image display button and, Image sensor and An observation apparatus characterized by having an optical system according to any one of claims 1 to 15.

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