Optical system and display device

Abstract

To provide an optical system having a wide field of view, a small size, and high optical performance.SOLUTION: An optical system that guides light from a display surface (ID) to a pupil surface (SP) includes, in order from the pupil surface side to the display surface side, a first transmission / reflection member having a first transmission / reflection surface (HM1) whose surface shape determined by paraxial curvature is concave toward the pupil surface, a negative first lens (Gn) having a pupil surface side surface (Rn1) whose surface shape determined by paraxial curvature is concave toward the pupil surface, and a second lens (Ga) having a second transmission / reflection surface (HM2) whose surface shape determined by paraxial curvature is concave toward the pupil surface. Light from the display surface passes through the second transmission / reflection surface, passes through the first lens, is reflected by the first transmission / reflection surface, passes through the first lens, is reflected by the second transmission / reflection surface, passes through the first lens, passes through the first transmission / reflection surface, and reaches the pupil plane.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system and a display device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known an optical system (observation optical system) that displays an enlarged version of an original image displayed on a display element such as a liquid crystal display (LCD) for a user to observe. Summary of the Invention [Problem to be solved by the invention]

[0003] There is a demand for an optical system that has a wider field of view, is smaller in size, and has higher optical performance than ever before. [Means for solving the problem]

[0004] An optical system according to one aspect of the present invention is an optical system that guides light from a display surface to a pupil plane, and includes, arranged in order from the pupil plane side to the display surface side, a first transmissive-reflective member having a first transmissive-reflective surface whose surface shape, determined by a paraxial curvature, is concave on the pupil plane side; a negative first lens having a pupil plane side surface whose surface shape, determined by the paraxial curvature, is concave on the pupil plane side; and a second lens having a second transmissive-reflective surface whose surface shape, determined by the paraxial curvature, is concave on the pupil plane side, and the light from the display surface passes through the second transmissive-reflective surface, passes through the first lens, is reflected by the first transmissive-reflective surface, passes through the first lens, is reflected by the second transmissive-reflective surface, passes through the first lens, and passes through the first transmissive-reflective surface to reach the pupil plane.

[0005] Other objects and features of the present invention are illustrated in the following examples. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is a cross-sectional view of an optical system according to the first embodiment. [Figure 2] 3A and 3B are longitudinal aberration diagrams of the optical system in Example 1. FIG. [Figure 3] FIG. 10 is a cross-sectional view of an optical system according to a second embodiment. [Figure 4] 10A and 10B are longitudinal aberration diagrams of the optical system in Example 2. FIG. [Figure 5] FIG. 10 is a cross-sectional view of an optical system according to a third embodiment. [Figure 6] 10A and 10B are longitudinal aberration diagrams of the optical system in Example 3. [Figure 7] FIG. 10 is a cross-sectional view of an optical system according to a fourth embodiment. [Figure 8] 10A and 10B are longitudinal aberration diagrams of the optical system in Example 4. [Figure 9] FIG. 10 is a cross-sectional view of an optical system according to a fifth embodiment. [Figure 10] 10A and 10B are longitudinal aberration diagrams of the optical system in Example 5. [Figure 11] FIG. 10 is a cross-sectional view of an optical system according to a sixth embodiment. [Figure 12] 13A and 13B are longitudinal aberration diagrams of the optical system in Example 6. [Figure 13] FIG. 10 is a cross-sectional view of an optical system according to a seventh embodiment. [Figure 14] FIG. 13 is a longitudinal aberration diagram of the optical system in Example 7. [Figure 15] FIG. 1 is an explanatory diagram of a configuration that uses polarized light. [Figure 16] FIG. 10 is an explanatory diagram of another configuration that utilizes polarized light. [Figure 17] FIG. 1 is a schematic diagram of a display device using the optical system in each example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0008] 1, 3, 5, 7, 9, 11, and 13 are cross-sectional views of optical systems (observation optical systems) according to Examples 1 to 7 of the present invention, respectively.

[0009] Prior to the specific description of Examples 1 to 7, we will explain matters common to all Examples. The optical system of each Example is used in a display device such as a head-mounted display (HMD) or smart glasses, and enlarges and displays an image displayed on a display element, enabling observation by an observer.

[0010] The optical system in each embodiment guides light (observation light) from a display surface ID of a display element to the observation side (pupil plane SP of the optical system where the observer's eye is located). The optical system includes, arranged in order from the observation side (pupil plane side) to the display surface side, a first transmissive-reflective member having a transmissive-reflective surface (first transmissive-reflective surface) HM1, a negative lens (negative first lens) Gn, and a lens (second lens) Ga having a transmissive-reflective surface (second transmissive-reflective surface) HM2. The light (observation light) from the display surface passes through the transmissive-reflective surface HM2, passes through the negative lens Gn, is reflected by the transmissive-reflective surface HM1, passes through the negative lens Gn, is reflected by the transmissive-reflective surface HM2, passes through the negative lens Gn, passes through the transmissive-reflective surface HM1, and then reaches the pupil plane SP.

[0011] The surface shape of the transmission-reflection surface HM1, determined by its paraxial curvature, is preferably concave toward the pupil plane. The negative lens Gn preferably has an observation-side surface (pupil-side surface) Rn1, the surface shape of which, determined by its paraxial curvature, is concave toward the pupil plane. The surface shape of the transmission-reflection surface HM2, determined by its paraxial curvature, is preferably concave toward the pupil plane.

[0012] Here, the lens surface shape determined by the paraxial curvature being concave toward the observation side means that the r term in the aspherical shape equation described in the numerical example below is negative. A specific lens surface shape is that the shape of a reference spherical surface (a spherical surface determined by the coordinates of the vertex of the surface above the optical axis and the surface at a height of about 1 / 10 of the optical effective diameter) in a region near the optical axis, for example, at a height of about 1 / 10 of the optical effective diameter, is concave toward the observation side. More specifically, this means that the shape of the reference spherical surface at a height of about half (about 2 mm) of the observer's standard pupil diameter Φ of 4 mm is concave toward the observation side.

[0013] This allows each lens surface to be concentric with the observer's pupil, thereby enabling excellent correction of field curvature and astigmatism in a wide-field-angle observation optical system. Furthermore, the observation optical system in each embodiment employs a triple-path configuration in which light rays from the display element are transmitted through HM2, Gn, reflected by HM1, transmitted through Gn, reflected by HM2, transmitted through Gn, and transmitted through HM1 to the observation side. By employing such a triple-path configuration, the observation optical system can be made thinner while maintaining a sufficient optical path length. Furthermore, by placing a negative lens Gn in the triple-path (light rays pass three times) optical path, the negative refractive power (the reciprocal of the focal length) is shared three times in the optical system (entire system), enabling excellent correction of chromatic aberration in the optical system (entire system).

[0014] In other words, by optimizing the shapes of the two transmissive and reflective surfaces and the negative lens arrangement in the triple-path optical configuration, it is possible to correct monochromatic aberrations such as field curvature, astigmatism, and chromatic aberration with the minimum number of lens elements.

[0015] In the optical systems of the respective embodiments, the transflective surface HM1 is preferably cemented to the observation-side surface Rn1 of the negative lens Gn. When a configuration utilizing polarized light, as described below, is applied and the transflective surface HM1 is arranged as a polarization-selective transflective element, it is preferable to use a film-type polarizing element. Using a thin film-type polarizing element makes it easy to arrange the transflective surface HM1 as a curved surface. In this case, laminating (cementing) a film onto the lens surface is effective for stably maintaining the surface shape of the transflective surface HM1. Here, by adopting a configuration in which the transflective surface HM1 is cemented to the observation-side surface Rn1 of the negative lens Gn, the curved transflective surface HM1 can be stably arranged in the optical system without increasing the number of lenses.

[0016] More preferably, in the optical systems of each embodiment, the surface shapes of the transmission-reflection surface HM1 and the observation-side surface Rn1 are substantially identical (have substantially the same shape). When a film-type element is bonded to a lens surface, it is preferable for the transmission-reflection surface HM1 and the observation-side surface Rn1 to have the same shape. However, due to factors such as the thickness of the polarizing film, the influence of the adhesive used for bonding, and the stretching of the film when bonding a flat film to a curved surface, the transmission-reflection surface HM1 and the observation-side surface Rn1 generally do not have completely identical shapes. The term "substantially the same shape" here is intended to take such influences into consideration. Specifically, the difference in the surface shapes of the two surfaces is within 0.05 mm of the difference in sag in the optical axis direction within the optical effective diameter. More preferably, the difference in sag is within 0.01 mm, and even more preferably within 0.005 mm.

[0017] In the optical systems of the respective embodiments, it is preferable that the transmissive-reflective surface HM1 and the observation-side surface Rn1 are a common surface (the same surface). It is preferable to use another configuration utilizing polarized light, as described below, and arrange a half mirror made of a metal or dielectric multilayer film on the observation-side surface Rn1 to make the transmissive-reflective surface HM1 the same surface. This allows a curved transmissive-reflective surface HM1 to be arranged in the optical system without increasing the number of lenses. Furthermore, when using a configuration utilizing polarized light, as described below, and arranging the transmissive-reflective surface HM1 as a polarization-selective transmissive-reflective element, it is possible to arrange it on the same surface as the transmissive-reflective surface HM1 by employing a configuration in which a wire grid structure is integrally molded on the observation-side surface Rn1.

[0018] Here, the focal length of the negative lens Gn in air is fGn, and the focal length of the optical system (entire system) is f. The refractive index of the optical material of the negative lens Gn at the d-line is NdGn, and the Abbe number at the d-line is vdGn. The paraxial radius of curvature of the observation-side surface Rn1 of the negative lens Gn is Rna, and the paraxial radius of curvature of the display-side surface Rnb. It is preferable to satisfy at least one of the following conditional expressions (1) to (4):

[0019] 2<|fGn| / f<50 …(1) 1.4 <NdGn<1.8 …(2) 10<νdGn<50 …(3) 1≦(Rnb+Rna) / (Rnb-Rna)<30 …(4) Conditional formula (1) defines the ratio between the focal length of the negative lens Gn and the focal length of the entire observation optical system. By satisfying conditional formula (1), the refractive power arrangement of the negative lens Gn within the optical system is optimized, thereby achieving both chromatic aberration correction and a compact optical system. Here, since the negative lens Gn is disposed in a triple-path optical path, providing three times the negative refractive power of the entire optical system, it is particularly preferable to optimize the refractive power arrangement. Below the lower limit of conditional formula (1), the negative refractive power of the negative lens Gn becomes too large compared to the focal length of the optical system (entire system), which is undesirable because chromatic aberration in the optical system (entire system) is overcorrected. Alternatively, the focal length of the optical system (entire system) becomes too long, which increases the size of the optical system. On the other hand, above the upper limit of conditional formula (1), the negative refractive power of the negative lens Gn becomes too small compared to the focal length of the optical system (entire system), which is undesirable because chromatic aberration in the optical system (entire system) is undercorrected. Alternatively, the focal length of the optical system (entire system) may become too short, making it difficult to correct monochromatic aberrations such as curvature of field in the optical system (entire system).

[0020] Conditional formula (2) defines the refractive index of the negative lens Gn at the d-line. Satisfying conditional formula (2) achieves both monochromatic aberration correction and lightweighting of the optical system. If the lower limit of conditional formula (2) is exceeded, the refractive index of the negative lens Gn at the d-line becomes too small, making it difficult to correct spherical aberration and higher-order components of monochromatic aberration in the entire optical system, which is undesirable. On the other hand, if the upper limit of conditional formula (2) is exceeded, the refractive index of the negative lens Gn at the d-line becomes too large, which requires the selection of a lens material with a high specific gravity (for example, high refractive index optical glass), thereby increasing the weight of the optical system.

[0021] Conditional formula (3) defines the Abbe number of the negative lens Gn at the d-line. Satisfying conditional formula (3) effectively corrects chromatic aberration in the optical system. Below the lower limit of conditional formula (3), the Abbe number of the negative lens Gn at the d-line becomes too small, resulting in overcorrection of chromatic aberration in the entire optical system, which is undesirable. Furthermore, optical materials with small Abbe numbers generally have low transmittance in the short wavelength range, which can lead to excessively low transmittance in the entire optical system when used in a lens disposed in a triple-path optical path. Furthermore, resin materials with small Abbe numbers generally have difficulty reducing birefringence, making it difficult to reduce unwanted light when using a polarized light configuration, as described below. On the other hand, above the upper limit of conditional formula (3), the Abbe number of the negative lens Gn at the d-line becomes too large, resulting in undercorrection of chromatic aberration in the entire optical system.

[0022] Conditional formula (4) defines the lens shape of the negative lens Gn. By satisfying conditional formula (4), both compactness and chromatic aberration correction are achieved in the entire optical system. If the lower limit of conditional formula (4) is not met, the shape of the negative lens Gn becomes biconcave. This undesirably increases the lens volume and weight of the optical system. Furthermore, when a resin lens material is used to reduce the weight of the optical system, a biconcave lens with a large thickness deviation ratio generally poses challenges in reducing birefringence. This makes it difficult to reduce unwanted light when a polarized light configuration, as described below, is used. On the other hand, if the upper limit of conditional formula (4) is exceeded, the negative lens Gn becomes an extremely flat negative meniscus lens. In this case, the paraxial negative refractive power of the negative lens Gn becomes too small, resulting in insufficient correction of chromatic aberration in the entire optical system.

[0023] More preferably, the upper limit of conditional expression (1) is set to 45, 40, 35, 30, 25, 20, or 15. More preferably, the lower limit of conditional expression (1) is set to 3, 4, 5, 6, 7, 8, 9, or 10.

[0024] More preferably, the upper limit of conditional expression (2) is set to 1.78, 1.76, 1.74, 1.72, 1.70, 1.68, or 1.67, and more preferably, the lower limit of conditional expression (2) is set to 1.45, 1.50, 1.55, 1.60, or 1.63.

[0025] More preferably, the upper limit of conditional expression (3) is set to 45, 40, 35, 30, 25, or 24. More preferably, the lower limit of conditional expression (3) is set to 11, 12, 13, 15, 17, 19, or 20.

[0026] More preferably, the upper limit of conditional expression (4) is set to 27, 25, 23, 20, 17, 15, or 13. More preferably, the lower limit of conditional expression (4) is set to 1.5, 2.0, 2.5, 3.0, 3.5, or 3.8. [When lens Ga is a negative lens] When the lens Ga is a negative lens, the transmissive-reflective surface HM2 is preferably the observation side (pupil surface side) of the lens Ga. By using the transmissive-reflective surface HM2 as the observation side of the lens Ga, the lens Ga can be arranged in a single-pass configuration (where light passes only once) outside the triple-pass optical path. This prevents overcorrection of chromatic aberration and Petzval sum when combined with a negative lens Gn arranged in the triple-pass optical path. Furthermore, when a polarized light configuration (described below) is adopted and a resin lens is used for the lens Ga, ghost light generated by birefringence in the lens material can be minimized.

[0027] Here, when the focal length of the lens Ga in air is fGa, it is preferable to satisfy the following conditional expression (5):

[0028] 3 <fGn / fGa<40 …(5) Conditional expression (5) defines the ratio of the focal lengths of the lens Ga and the negative lens Gn. By satisfying conditional expression (5), the refractive power distribution of the two negative lenses arranged in the optical system is optimized, thereby achieving both correction of chromatic aberration and correction of field curvature. Below the lower limit of conditional expression (5), the negative refractive power of the lens Ga arranged in the single-path optical path becomes too small compared to the negative refractive power of the negative lens Gn arranged in the triple-path optical path. This is undesirable because the negative refractive power distribution of the negative lens Gn arranged in the triple-path optical path becomes too strong, resulting in overcorrection of chromatic aberration in the entire optical system and overcorrection of field curvature due to the Petzval sum being negative. On the other hand, above the upper limit of conditional expression (5), the negative refractive power distribution of the negative lens Gn arranged in the triple-path optical path becomes too weak, resulting in undercorrection of chromatic aberration and field curvature in the entire optical system.

[0029] More preferably, the upper limit of conditional expression (5) is set to 35, 30, 25, 20, or 16. More preferably, the lower limit of conditional expression (5) is set to 3.5, 4.0, 4.5, 5.0, 5.5, or 6.0.

[0030] It is also preferable to have a positive lens (third lens) Gb on the observation side of the lens Ga. By placing the lens Gb between the negative lens Gn and the lens Ga, the lens Gb is placed in a triple-path optical path. In this way, the lens Gb shares the positive refractive power three times in the optical system (entire system), allowing the optical system to achieve both high magnification (wider angle of view) and compactness.

[0031] Here, the focal length of lens Gb in air is defined as fGb. Furthermore, the Abbe number at the d-line of the optical material of lens Ga is defined as νdGa, and the Abbe number at the d-line of the optical material of lens Gb is defined as νdGb. In this case, it is preferable to satisfy at least one of the following conditional expressions (6) and (7):

[0032] 0.8 <fGb / |fGa|<3.5 …(6) 0.15<νdGa / νdGb<0.80 …(7) Conditional formula (6) defines the ratio of the focal lengths of the lenses Gb and Ga. By satisfying conditional formula (6), chromatic aberration in the optical system (entire system) is well corrected. If the lower limit of conditional formula (6) is not met, the negative refractive power of the lens Gb becomes too small relative to the positive refractive power of the lens Gb, resulting in an arrangement in which chromatic aberration in the optical system (entire system) is undercorrected, which is undesirable. On the other hand, if the upper limit of conditional formula (6) is exceeded, the negative refractive power of the lens Gb becomes too large, resulting in overcorrection of chromatic aberration in the optical system (entire system).

[0033] Conditional formula (7) defines the ratio of the Abbe numbers of the lens materials of lens Gb and lens Ga at the d-line. By satisfying conditional formula (7), both monochromatic aberration and chromatic aberration can be corrected in the entire optical system. Below the lower limit of conditional formula (7), the ratio of the Abbe numbers of lens Ga and lens Gb becomes too large. In this case, an optical material with an extremely large Abbe number is used for lens Gb, while an optical material with an extremely small Abbe number is used for lens Ga. Optical materials with extremely large Abbe numbers generally have a low refractive index, making it difficult to correct monochromatic aberration. Furthermore, optical materials with extremely small Abbe numbers generally have low transmittance in the short wavelength range, which reduces the transmittance of the entire optical system, making this undesirable. On the other hand, above the upper limit of conditional formula (7), the ratio of the Abbe numbers of lens Ga and lens Gb becomes too small, resulting in an arrangement in which the Abbe numbers of lens Ga and lens Gb are too close to each other. Here, when achromatization is performed using the lenses Ga and Gb, the refractive power of each single lens becomes too large, making it difficult to simultaneously correct both monochromatic aberration and chromatic aberration in the optical system (entire system).

[0034] More preferably, the upper limit of conditional expression (6) is set to 3.4, 3.2, 3.0, 2.8, 2.6, 2.5, or 2.4, and the lower limit of conditional expression (6) is set to 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or 1.6.

[0035] More preferably, the upper limit of conditional expression (7) is set to 0.7, 0.6, 0.5, 0.45, or 0.42, and the lower limit of conditional expression (7) is set to 0.18, 0.20, 0.25, 0.30, or 0.35.

[0036] Furthermore, it is preferable that the lenses Ga and Gb are cemented together. By cementing the lenses Ga and Gb together, the air gap between the lenses can be reduced, thereby reducing the overall lens length. Furthermore, by locating the transmission-reflection surface HM2 on the observation side of the lens Ga at the cemented surface, total reflection, which becomes an issue when the transmission-reflection surface HM2 is given a strong positive reflective power in order to increase the magnification of the optical system, can be avoided. Furthermore, because the cemented surface is less exposed to the external environment, it is also advantageous in terms of environmental resistance when a metal film or a dielectric multilayer film is used as the transmission-reflection surface. [When lens Ga is positive] When the lens Ga is a positive lens, the transmissive-reflective surface HM2 is preferably the display surface side of the lens Ga (the surface on the display surface ID side). By using the display surface side of the lens Ga as the transmissive-reflective surface HM2, the lens Ga can be positioned in the round-trip optical path of the observation light, allowing the optical system (entire system) to share the positive refractive power multiple times. This allows the observation optical system to be both high-magnification and compact.

[0037] Here, when the focal length of the lens Ga in air is fGa, it is preferable to satisfy the following conditional expression (8):

[0038] 1<|fGn| / fGa<10 …(8) Conditional expression (8) defines the ratio of the focal lengths of the lens Ga and the negative lens Gn. Satisfying conditional expression (8) optimizes the refractive power distribution between the negative and positive lenses in the optical system, thereby achieving both chromatic aberration correction and high magnification of the optical system. Below the lower limit of conditional expression (8), the positive refractive power of the lens Gb arranged in the single-path optical path becomes too small compared to the negative refractive power of the negative lens Gn arranged in the triple-path optical path. This is undesirable because the negative refractive power distribution of the negative lens Gn arranged in the triple-path optical path becomes too strong, resulting in overcorrection of chromatic aberration in the optical system (entire system) and difficulty in achieving high magnification. On the other hand, above the upper limit of conditional expression (8), the negative refractive power distribution of the negative lens Gn arranged in the triple-path optical path becomes too weak, resulting in undercorrection of chromatic aberration in the optical system (entire system).

[0039] More preferably, the upper limit of conditional expression (8) is set to 9, 8, 7, 6, or 5. More preferably, the lower limit of conditional expression (8) is set to 1.5, 2.0, 2.5, 3.0, or 3.1.

[0040] At least one of the two transmission-reflection surfaces may be configured with a polarization-selective transmission-reflection element. This allows for the use of polarization, as described below, to block unwanted light (leakage light) such as ghosts. Examples of polarization-selective transmission-reflection elements include a wire grid element such as Asahi Kasei's WGF, a reflective linear polarization element such as 3M's IQP-E, and a circular polarization reflection element using cholesteric liquid crystal. When a reflective linear polarization element is used, a quarter-wave plate is placed between the two transmission-reflection surfaces. Various known methods can be used to arrange the polarization elements, such as bonding a film-like polarization element to the optical surface of the lens or molding a wire grid structure integrally with the lens base material during resin lens molding.

[0041] The following explains the configuration using polarized light. By adopting this configuration, it is possible to suppress the decrease in the amount of light in the normal optical path within the observation optical system, while reducing the amount of unwanted light that passes through the transmission-reflection surface and heads toward the observation side without ever being reflected by it. [Configuration using polarized light] 15 is an explanatory diagram of a configuration (first configuration) that uses polarized light. The first configuration has a polarization-selective transmission / reflection element (PBS) A arranged on the observation side (pupil plane SP side) and a half mirror (HM) C arranged on the display element side (display surface ID side). A first quarter-wave plate (QWP1) B is arranged between the PBS and HM. Furthermore, a second quarter-wave plate (QWP2) D and a linear polarizer (POL) E are arranged between the HM and ID from the HM side.

[0042] The PBS is configured to reflect linearly polarized light with the same polarization direction as the linearly polarized light that passes through the POL and to transmit linearly polarized light with a polarization direction perpendicular to that of the linearly polarized light that passes through the POL. The PBS is, for example, a wire grid polarizer or a reflective polarizer with a laminated retardation film structure. In this case, the wire grid-formed surface or retardation film surface of the PBS functions as the second transmission-reflection surface.

[0043] Furthermore, QWP1 and QWP2 are arranged with their slow axes tilted at 45° with respect to the polarization transmission axis of the POL. Furthermore, it is preferable that QWP1 and QWP2 are arranged with their slow axes tilted at 90° with respect to each other. With this arrangement, the wavelength dispersion characteristics of QWP1 and QWP2 cancel each other out when light passes through them.

[0044] The HM is a half mirror formed by, for example, a dielectric multilayer film or metal deposition, and functions as a first transmissive-reflective surface. From the perspective of the transmittance of the entire optical system, the ratio of reflectance to transmittance of the half mirror is preferably 50:50, but this ratio can be adjusted as desired. The POL is, for example, an absorptive linear polarizer.

[0045] The unpolarized light emitted from the ID becomes first linearly polarized light at the POL, and this first linearly polarized light is converted to first circularly polarized light by the QWP2 and enters the HM. A portion of the first circularly polarized light that enters the HM is reflected by the HM and becomes second circularly polarized light with a polarization direction opposite to that of the first circularly polarized light, and the second circularly polarized light returns to the QWP2. The second circularly polarized light that returns to the QWP2 is converted into second linearly polarized light with a polarization direction perpendicular to that of the first linearly polarized light. The second linearly polarized light returns to the POL and is absorbed by the POL.

[0046] Meanwhile, the other part of the first circularly polarized light that entered the HM is transmitted through it and converted by the QWP1 into third linearly polarized light with the same polarization direction as the first linearly polarized light, and this third linearly polarized light enters the PBS, where it is reflected due to the polarization selectivity of the PBS.

[0047] The third linearly polarized light reflected by the PBS is converted by QWP1 into third circularly polarized light with the same rotation as the first circularly polarized light. The third circularly polarized light is then incident on the HM and reflected, becoming fourth circularly polarized light with the opposite rotation to the third circularly polarized light. The fourth circularly polarized light then enters QWP1 and is converted into fourth linearly polarized light with a polarization direction perpendicular to the polarization direction of the third linearly polarized light. The fourth linearly polarized light then enters the PBS, where it passes through due to the polarization selectivity of the PBS and is guided to the pupil plane SP.

[0048] Due to the above optical action, only the light that passes through the HM, is reflected by the PBS, is reflected by the HM, and passes through the PBS is guided to the pupil plane SP and enters the eye (pupil) of the observer located at the pupil plane SP. [Another configuration using polarized light] Figure 16 is an explanatory diagram of another configuration (second configuration) that uses polarized light. This configuration has a polarization-selective transmission / reflection element (PBS) A arranged on the display element side (display surface ID side) and a half mirror (HM) C arranged on the observation side (pupil surface SP side). A first quarter-wave plate (QWP1) B is arranged between the PBS and HM. Furthermore, a second quarter-wave plate (QWP2) D and a linear polarizer (POL) E are arranged from the HM side between the HM and SP. The configuration of each element and the preferred optical axis orientation are the same as in the first configuration.

[0049] Unpolarized light emitted from the ID enters the PBS. Due to the wavelength selectivity of the PBS, the first linearly polarized light, which has a polarization direction perpendicular to the transmission axis of the POL, is transmitted through the PBS. The first linearly polarized light that passes through the PBS is converted into first circularly polarized light by QWP1, and this first circularly polarized light enters the HM. A portion of the first circularly polarized light that enters the HM is transmitted through and enters QWP2, where it is converted into second linearly polarized light with the same polarization direction as the first linearly polarized light. The second linearly polarized light enters the POL and is absorbed by the POL.

[0050] Meanwhile, the other portion of the first circularly polarized light that entered the HM is reflected by the HM and becomes second circularly polarized light with a polarization direction opposite to that of the first circularly polarized light, and the second circularly polarized light returns to QWP1. After returning to QWP1, the second circularly polarized light is converted by QWP1 into third linearly polarized light with a polarization direction perpendicular to that of the first linearly polarized light. The third linearly polarized light returns to the PBS. After returning to the PBS, the third linearly polarized light is reflected by the polarization selectivity of the PBS and returns to QWP1, where it is converted into third circularly polarized light with the same polarization direction as the first circularly polarized light. The third circularly polarized light again enters the HM, passes through it, and enters QWP2, where it is converted by QWP2 into fourth linearly polarized light with a polarization direction parallel to the transmission axis of the POL. The fourth linearly polarized light passes through the POL and is directed to the pupil plane SP.

[0051] Due to the above optical action, only the light that passes through the PBS, is reflected by the HM, is reflected by the PBS, and passes through the HM is guided to the pupil plane SP and enters the eye of the observer positioned at the pupil plane SP.

[0052] In the two polarized light configurations, it is preferable to add various polarizing elements to block unwanted light reflections on the PBS surface or display element surface. For example, in Figure 15, an absorptive linear polarizer with the same transmission axis as the PBS can be placed on the observation side of the polarization-selective reflector (PBS) A to block external light reflections on the PBS surface. Furthermore, in Figure 15, a phase plate can be placed between the linear polarizer (POL) E and the display surface ID, and in Figure 16, between the polarization-selective reflector (PBS) A and the display surface ID to block unwanted light reflections on the display surface ID. Here, it is preferable to use a phase plate equivalent to a quarter-wave plate with its slow axis tilted 45 degrees relative to the transmission axis of the POL PBS.

[0053] In each embodiment, the optical material of each lens may be a resin material, which is advantageous in terms of reducing the weight compared to when a glass material is used.

[0054] Furthermore, in the optical systems of the respective embodiments, diopter adjustment can be performed using various methods. For example, diopter adjustment can be performed by moving the entire observation optical system, a part of it, or the display element in the direction of the optical axis. In this case, an inner focus system in which the lens group located closest to the observation side is fixed is preferable from the viewpoint of dustproof construction. In addition to the method of moving lenses in the direction of the optical axis, diopter adjustment can also be performed by providing an optical element whose refractive power is variable by mechanical or electrical action, such as a shape-changeable lens that utilizes pressure or electrowetting, or a liquid crystal lens. [Example]

[0055] The optical system (observation optical system) of Example 1 (Numerical Example 1) shown in FIG. 1 is an optical system with a total field of view angle of approximately 100 degrees. The optical system of this example includes, in order from the pupil plane SP side to the display surface ID side, a negative lens (first lens) Gn with a meniscus shape concave on the observation side and negative refractive power, and a biconvex lens (second lens) Ga with positive refractive power. Here, the first lens is a negative lens Gn with an observation-side surface Rn1 concave on the observation side, and a concave transmission-reflection surface HM1 is disposed on the observation side of the negative lens Gn. The second lens is a lens Ga with a transmission-reflection surface HM2, and a concave transmission-reflection surface HM2 is disposed on the display element side of the lens Ga. In this example, the lens Ga is a positive lens.

[0056] Light from display surface ID passes through HM2, is reflected by HM1, is reflected by HM2, passes through HM1, and is directed to pupil plane SP.

[0057] This embodiment employs a configuration that utilizes polarized light. Specifically, a reflective polarizing film is used as the transflective surface HM1, and is bonded to the observation side surface R1n of the negative lens Gn together with a quarter-wave plate (QWP1). In Numerical Example 1, the transflective surface HM1 and the observation side surface R1n of the negative lens Gn are arranged to have the same surface shape. Furthermore, the quarter-wave plate (QWP2) and linear polarizer (POL) are bonded to the observation side surface of the glass block CG.

[0058] The values ​​of the conditional expressions (1) to (4) and (8) in Numerical Example 1 are summarized in Table 1. The optical system of this example satisfies all of the conditional expressions (1) to (4) and (8).

[0059] FIG. 2 shows longitudinal aberration diagrams (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) for the optical system of this example (visor: -0.67 diopter). In the spherical aberration diagram, EPD indicates pupil diameter, the solid line indicates spherical aberration for the d-line, the two-dot chain line indicates spherical aberration for the C-line, and the one-dot chain line indicates spherical aberration for the F-line. In the astigmatism diagram, the solid line ΔS indicates astigmatism on the sagittal image plane, and the dashed line ΔM indicates astigmatism on the meridional image plane. The distortion diagram shows distortion at the d-line. The lateral chromatic aberration diagram shows lateral chromatic aberration for the C-line (two-dot chain line) and the F-line (one-dot chain line). ω is the half field of view (°). The explanations regarding these longitudinal aberration diagrams also apply to the longitudinal aberration diagrams (FIGS. 4, 6, 8, 10, 12, and 14) of the optical systems in Examples 2 to 7 described later. [Example]

[0060] The optical system (observation optical system) of Example 2 (Numerical Example 2) shown in Fig. 3 is an optical system with a total field of view angle of approximately 95 degrees. The basic configuration of the optical system of this example is the same as that of Example 1. Compared to Example 1, the optical system of this example has a smaller display element and a negative lens added to the display element side of lens Ga having transmission-reflection surface HM2, thereby achieving high magnification and miniaturization while maintaining optical performance.

[0061] The basic arrangement of the observation light path leading from the display surface ID to the pupil surface SP and the configuration using polarized light is the same as in Example 1. However, in this example, the reflective polarizing film used in Example 1 is reversed and attached to the observation side surface R1n, and the transmissive-reflective surface HM1 is arranged on the display surface side of the reflective polarizing film.

[0062] The values ​​of the conditional expressions (1) to (4) and (8) in Numerical Example 2 are summarized in Table 1. The optical system of this example satisfies all of the conditional expressions (1) to (4) and (8). [Example]

[0063] The optical system (observation optical system) of Example 3 (Numerical Example 3) shown in FIG. 5 is an optical system with a total field of view angle of approximately 90 degrees. The optical system of this example has, arranged in order from the pupil plane SP side to the display plane ID side, a lens (fourth lens) Gc with positive refractive power, a negative lens (first lens) Gn with negative refractive power, a lens (third lens) Gb with positive refractive power, and a lens (second lens) Ga with negative refractive power. The lens Gc is a positive lens with a plano-convex shape. The negative lens Gn is a negative lens with a concave meniscus shape facing the observation side. The lens Gb is a positive lens with a plano-convex shape. The lens Ga is a negative lens with a concave meniscus shape facing the observation side.

[0064] Here, the first lens is a negative lens Gn having a concave observation side surface Rn1 on the observation side, and a concave transmission-reflection surface HM1 is arranged on the observation side of the negative lens Gn. The second lens is a lens Ga having a transmission-reflection surface HM2, and a concave HM2 is arranged on the observation side of the lens Ga. In this embodiment, the lens Ga is a negative lens.

[0065] The observation light path leading from the display surface ID to the pupil surface SP and the basic arrangement of the configuration using polarized light are the same as in Example 1. In this example, the quarter-wave plate (QWP1) in the configuration using polarized light is placed on the observation-side flat surface of the third lens, which is a plano-convex lens. By placing the quarter-wave plate as a flat surface, changes in polarization characteristics and poor appearance during film lamination processing can be suppressed.

[0066] The values ​​of the conditional expressions (1) to (7) in Numerical Example 3 are summarized in Table 1. The optical system of this example satisfies all of the conditional expressions (1) to (7). [Example]

[0067] The optical system (observation optical system) of Example 4 (Numerical Example 4) shown in Fig. 7 is an optical system with a total field of view angle of approximately 90 degrees. The basic configuration of the optical system of this example is the same as that of Example 3. This example differs from Example 3 in that the optical element arranged closest to the observation side is changed to a flat protective window and the number of lenses is changed to three.

[0068] The optical system of this embodiment has a negative lens (first lens) Gn, a lens (third lens) Gb, and a lens (second lens) Ga, arranged in this order from the pupil plane SP side to the display plane ID side. The negative lens Gn is a lens with negative refractive power and a meniscus shape concave on the observation side. The lens Gb is a lens with positive refractive power and a meniscus shape concave on the observation side. The lens Ga is a lens with negative refractive power and a meniscus shape concave on the observation side.

[0069] Here, the first lens is a negative lens Gn having a concave observation side surface Rn1 on the observation side, and a concave transmission-reflection surface HM1 is arranged on the observation side of the negative lens Gn. The second lens is a lens Ga having a transmission-reflection surface HM2, and a concave HM2 is arranged on the observation side of the lens Ga. In this embodiment, the lens Ga is a negative lens.

[0070] The observation light path leading from the display surface ID to the pupil surface SP and the basic arrangement of the polarized light configuration are the same as in Example 1. In this Example, the reflective polarizing film used in Example 1 is reversed and attached to the observation side surface R1n, and the transmissive-reflective surface HM1 is positioned on the display element side of the reflective polarizing film. Furthermore, the quarter-wave plate (QWP1) in the polarized light configuration is positioned on the observation-side concave surface of the second lens, which is a meniscus-shaped positive lens. Positioning the quarter-wave plate as a curved surface ensures flexibility in aberration correction, achieving high optical performance.

[0071] The values ​​of the conditional expressions (1) to (7) in Numerical Example 4 are summarized in Table 1. The optical system of this example satisfies all of the conditional expressions (1) to (7). [Example]

[0072] The optical system (observation optical system) of Example 5 (Numerical Example 5) shown in FIG. 9 is an optical system with a total field of view angle of approximately 80 degrees. The basic configuration of the optical system of this example is the same as that of Example 1. Compared to Example 1, the arrangement of the polarizing elements in the configuration that utilizes polarized light is changed, and in this example, each polarizing film is modeled including adhesives, etc. Specifically, the observation side of the second lens is made flat, and a quarter-wave plate (QWP1) is bonded to this lens surface. Here, by adopting an arrangement in which the quarter-wave plate is bonded to the flat surface, changes in polarization characteristics and poor appearance can be suppressed during the film bonding process.

[0073] Here, the lens Ga is a positive lens, and the optical system of Numerical Example 5 satisfies all of conditional expressions (1) to (4) and (8). The values ​​of conditional expressions (1) to (4) and (8) in Numerical Example 5 are summarized in Table 1. [Example]

[0074] The optical system (observation optical system) of Example 6 (Numerical Example 6) shown in FIG. 11 is an optical system with a total field of view angle of approximately 80 degrees. The basic configuration of the optical system of this example is the same as that of Example 5. In this example, the polarizing element in the configuration that utilizes polarized light is changed compared to Example 5. Specifically, a wire grid polarizer is used as the transmission-reflection surface HM1. Furthermore, by integrally molding a wire grid structure with the lens base material on the observation side surface Rn1 of the first lens, the transmission-reflection surface HM1 is positioned on the same plane as the Rn1 surface. Here, by integrally molding the wire grid structure with the lens, it is possible to improve the surface precision of the polarized reflection surface and reduce processing costs compared to film lamination.

[0075] Here, the lens Ga is a positive lens, and the optical system of Numerical Example 6 satisfies all of conditional expressions (1) to (4) and (8). The values ​​of conditional expressions (1) to (4) and (8) in Numerical Example 6 are summarized in Table 1. [Example]

[0076] The optical system (observation optical system) of Example 7 (Numerical Example 7) shown in FIG. 13 is an optical system with a total field of view angle of approximately 80 degrees. The basic configuration of the optical system of this example is the same as that of Example 5. This example differs from Example 5 in that it employs a different configuration that utilizes polarized light. Specifically, a reflective polarizing film is used as the transflective surface HM2 and is bonded to the display side of the lens (second lens) Ga. In addition, a half mirror made of a multilayer film of metal or dielectric is formed on the observation side R1n of the negative lens (first lens) Gn, and is arranged on the same surface as the transflective surface HM1.

[0077] Here, the lens Ga is a positive lens, and the optical system of Numerical Example 7 satisfies all of conditional expressions (1) to (4) and (8). The values ​​of conditional expressions (1) to (4) and (8) in Numerical Example 7 are summarized in Table 1.

[0078] Numerical Examples 1 to 7 corresponding to Examples 1 to 7, respectively, are shown below. In each numerical example, ri is the radius of curvature of the ith surface, in order from the object side, di is the distance between the ith surface and the (i+1)th surface (lens thickness or air distance), and ndi and vdi are the refractive index and Abbe number of the material of the ith lens at the d-line, respectively. Note that the Abbe number vd of a certain material is given by: 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, respectively. νd=(Nd-1) / (NF-NC) It is expressed as:

[0079] * indicates an aspherical surface. k, A4, A6, A8, and A10 are aspherical coefficients. The aspherical shape is expressed by the following formula, where x is the displacement in the optical axis direction at a position of height h from the optical axis, relative to the vertex of the surface.

[0080] 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 where r is the paraxial radius of curvature.

[0081] (Numerical Example 1) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 (pupil plane) ∞ (variable) 4.00 2* -65.322 0.12 1.48000 50.0 44.00 3* -65.322 0.06 1.56000 30.0 44.00 HM1 4* -65.322 0.12 1.58000 30.0 44.00 5* -65.322 1.80 1.64220 22.4 44.00 Rn1 6* -111.491 0.50 44.00 7* 492.845 10.00 1.54390 56.0 48.00 8* -46.246 -10.00 Reflective surface 48.00 HM2 9* 492.845 -0.50 48.00 10* -111.491 -1.80 1.64220 22.4 44.00 11* -65.322 -0.12 1.58000 30.0 44.00 Rn1 12* -65.322 0.12 Reflective surface 44.00 HM1 13* -65.322 1.80 1.64220 22.4 44.00 Rn1 14* -111.491 0.50 44.00 15* 492.845 10.00 1.54390 56.0 48.00 16* -46.246 1.01 48.00 HM2 17 ∞ 0.12 1.58000 30.0 35.00 18 ∞ 0.12 1.48000 50.0 35.00 19 ∞ 0.84 1.51633 64.1 35.00 CG 20 ∞ 0.00 35.00 Image plane ∞ Aspheric data 2nd side K = 2.79561e+00 A 4= 1.16757e-05 A 6=-3.62846e-09 A 8= 1.01882e-11 A10=-1.25791e-14 3rd page K = 2.79561e+00 A 4= 1.16757e-05 A 6=-3.62846e-09 A 8= 1.01882e-11 A10=-1.25791e-14 Side 4 K = 2.79561e+00 A 4= 1.16757e-05 A 6=-3.62846e-09 A 8= 1.01882e-11 A10=-1.25791e-14 5th page K = 2.79561e+00 A 4= 1.16757e-05 A 6=-3.62846e-09 A 8= 1.01882e-11 A10=-1.25791e-14 Page 6 K = 0.00000e+00 A 4= 1.44734e-05 A 6=-3.01334e-08 A 8= 5.99000e-11 A10=-3.87106e-14 Side 7 K = 0.00000e+00 A 4= 2.06354e-06 Side 8 K =-2.91092e-02 A 4= 9.10118e-07 A 6= 2.10641e-09 A 8= 3.37645e-12 A10=-4.32806e-15 9th page K = 0.00000e+00 A 4= 2.06354e-06 Side 10 K = 0.00000e+00 A 4= 1.44734e-05 A 6=-3.01334e-08 A 8= 5.99000e-11 A10=-3.87106e-14 Page 11 K = 2.79561e+00 A 4= 1.16757e-05 A 6=-3.62846e-09 A 8= 1.01882e-11 A10=-1.25791e-14 Side 12 K = 2.79561e+00 A 4= 1.16757e-05 A 6=-3.62846e-09 A 8= 1.01882e-11 A10=-1.25791e-14 Page 13 K = 2.79561e+00 A 4= 1.16757e-05 A 6=-3.62846e-09 A 8= 1.01882e-11 A10=-1.25791e-14 Side 14 K = 0.00000e+00 A 4= 1.44734e-05 A 6=-3.01334e-08 A 8= 5.99000e-11 A10=-3.87106e-14 Page 15 K = 0.00000e+00 A 4= 2.06354e-06 Page 16 K =-2.91092e-02 A 4= 9.10118e-07 A 6= 2.10641e-09 A 8= 3.37645e-12 A10=-4.32806e-15 Various data Focal length 20.17 EPD 4.00 Half viewing angle 50.00 Image height 15.00 Lens length 14.69 (in G) BF 1.72 (in Air) d 1 15.00 Single lens data Lens starting surface focal length 1(Gn) 5 -249.43 2(Ga) 7 78.24 3(CG) 19 0.00 (Numerical Example 2) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 (Aperture) ∞ (Variable) 4.00 2* -43.403 0.10 1.48000 50.0 36.70 3* -43.403 0.06 1.56000 30.0 36.70 4* -43.403 1.70 1.64220 22.4 36.70 5* -53.999 0.20 36.70 Rn1=HM1 6 ∞ 0.10 1.58000 30.0 39.50 7 ∞ 7.28 1.49171 57.4 39.50 8* -36.276 -7.28 Reflective surface 39.50 HM2 9 ∞ -0.10 1.58000 30.0 39.50 10 ∞ -0.20 39.50 11* -53.999 -1.70 1.64220 22.4 36.70 12* -43.403 1.70 Reflective surface 36.70 Rn1=HM1 13* -53.999 0.20 36.70 14 ∞ 0.10 1.58000 30.0 39.50 15 ∞ 7.28 1.49171 57.4 39.50 16* -36.276 0.38 39.50 HM2 17* -52.406 1.95 1.64220 22.4 28.40 18* 192.163 0.78 26.30 19 ∞ 0.10 1.58000 30.0 30.00 20 ∞ 0.10 1.48000 50.0 30.00 21 ∞ 0.70 1.51633 64.1 30.00 CG 22 ∞ 0.00 30.00 Image plane ∞ Aspheric data 2nd side K = 1.29038e+00 A 4= 3.83206e-05 A 6=-8.31343e-08 A 8= 1.62856e-10 A10=-1.26453e-13 3rd page K = 1.29038e+00 A 4= 3.83206e-05 A 6=-8.31343e-08 A 8= 1.62856e-10 A10=-1.26453e-13 Side 4 K = 1.29038e+00 A 4= 3.83206e-05 A 6=-8.31343e-08 A 8= 1.62856e-10 A10=-1.26453e-13 5th page K = 0.00000e+00 A 4= 4.04263e-05 A 6=-1.44228e-07 A 8= 3.49682e-10 A10=-2.90790e-13 Side 8 K =-1.39879e+00 A 4=-1.05407e-06 A 6= 7.63095e-09 A 8=-1.20914e-12 A10=-1.45310e-14 Page 11 K = 0.00000e+00 A 4= 4.04263e-05 A 6=-1.44228e-07 A 8= 3.49682e-10 A10=-2.90790e-13 Side 12 K = 1.29038e+00 A 4= 3.83206e-05 A 6=-8.31343e-08 A 8= 1.62856e-10 A10=-1.26453e-13 Page 13 K = 0.00000e+00 A 4= 4.04263e-05 A 6=-1.44228e-07 A 8= 3.49682e-10 A10=-2.90790e-13 Page 16 K =-1.39879e+00 A 4=-1.05407e-06 A 6= 7.63095e-09 A 8=-1.20914e-12 A10=-1.45310e-14 Page 17 K = 9.72780e+00 A 4= 2.52085e-05 A 6= 3.05661e-07 A 8=-1.09729e-09 A10= 3.22599e-12 Side 18 K = 0.00000e+00 A 4=-7.97669e-05 A 6= 7.76147e-07 A 8=-2.14262e-09 A10= 1.67580e-13 A12= 2.33779e-16 Various data Focal length 17.87 EPD 4.00 Half viewing angle 47.50 Image height 12.00 Lens length 13.45 (in G) BF 1.37 (in Air) d 1 15.00 Single lens data Lens starting surface focal length 1(Gn) 4 -367.50 2(Ga) 7 73.77 3 17 -63.92 4(CG) 21 0.00 (Numerical Example 3) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 (pupil plane) ∞ (variable) 4.00 2 ∞ 0.12 1.48000 50.0 37.00 3 ∞ 3.50 1.54390 56.0 37.00 4* -73.052 0.06 1.56000 30.0 37.00 HM1 5* -73.052 1.80 1.66100 20.4 37.00 Rn1 6* -112.588 0.12 37.00 7 ∞ 0.12 1.58000 30.0 40.50 8 ∞ 7.65 1.54390 56.0 40.50 9* -43.946 -7.65 Reflective surface 40.50 HM2 10 ∞ -0.12 1.58000 30.0 40.50 11 ∞ -0.12 40.50 12* -112.588 -1.80 1.66100 20.4 37.00 13* -73.052 -0.06 1.56000 30.0 37.00 Rn1 14* -73.052 0.06 Reflective surface 37.00 HM1 15* -73.052 1.80 1.66100 20.4 37.00 Rn1 16* -112.588 0.12 37.00 17 ∞ 0.12 1.58000 30.0 40.50 18 ∞ 7.65 1.54390 56.0 40.50 19* -43.946 2.10 1.64220 22.4 40.50 20* 115.285 0.96 30.50 21 ∞ 0.12 1.58000 30.0 30.00 22 ∞ 0.12 1.48000 50.0 30.00 23 ∞ 0.70 1.51633 64.1 30.00 CG 24 ∞ 0.00 30.00 Image plane ∞ Aspheric data Side 4 K = 0.00000e+00 A 4= 9.79739e-06 A 6=-7.60934e-09 A 8=-5.11674e-12 A10= 3.77033e-14 5th page K = 0.00000e+00 A 4= 9.79739e-06 A 6=-7.60934e-09 A 8=-5.11674e-12 A10= 3.77033e-14 Page 6 K = 0.00000e+00 A 4= 1.21581e-05 A 6=-3.63947e-08 A 8= 8.45097e-11 A10=-3.88384e-14 9th page K = 0.00000e+00 A 4=-6.02356e-07 A 6= 6.40374e-09 A 8=-7.39365e-12 A10=-7.63048e-16 Side 12 K = 0.00000e+00 A 4= 1.21581e-05 A 6=-3.63947e-08 A 8= 8.45097e-11 A10=-3.88384e-14 Page 13 K = 0.00000e+00 A 4= 9.79739e-06 A 6=-7.60934e-09 A 8=-5.11674e-12 A10= 3.77033e-14 Side 14 K = 0.00000e+00 A 4= 9.79739e-06 A 6=-7.60934e-09 A 8=-5.11674e-12 A10= 3.77033e-14 Page 15 K = 0.00000e+00 A 4= 9.79739e-06 A 6=-7.60934e-09 A 8=-5.11674e-12 A10= 3.77033e-14 Page 16 K = 0.00000e+00 A 4= 1.21581e-05 A 6=-3.63947e-08 A 8= 8.45097e-11 A10=-3.88384e-14 Page 19 K = 0.00000e+00 A 4=-6.02356e-07 A 6= 6.40374e-09 A 8=-7.39365e-12 A10=-7.63048e-16 Page 20 K = 0.00000e+00 A 4=-1.95891e-04 A 6= 1.11105e-06 A 8=-3.22088e-09 A10= 3.77579e-12 Various data Focal length 18.22 F-number 4.55 EPD 4.00 Half viewing angle 45.00 Lens length 17.37 (in G) BF 1.58 (in Air) d 1 15.00 Single lens data Lens starting surface focal length 1 3 134.31 2(Gn) 5 -320.53 3(Gb) 8 80.80 4(Ga) 12 -320.53 5(CG) 23 0.00 (Numerical Example 4) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 (Aperture) ∞ (Variable) 4.00 2 ∞ 0.12 1.48000 50.0 37.30 3 ∞ 1.00 1.51633 64.1 37.30 4 ∞ 1.75 37.30 5* -41.046 0.06 1.56000 30.0 37.30 6* -41.046 2.00 1.63500 23.5 37.30 Rn1=HM1 7* -48.354 0.15 37.30 8 -500.000 0.12 1.58000 30.0 40.70 9 -500.000 7.60 1.54390 56.0 40.70 10* -37.339 -7.60 Reflective surface 40.70 HM2 11 -500.000 -0.12 1.58000 30.0 40.70 12 -500.000 -0.15 40.70 13* -48.354 -2.00 1.63500 23.5 37.30 14* -41.046 2.00 Reflective surface 37.30 Rn1=HM1 15* -48.354 0.15 37.30 16 -500.000 0.12 1.58000 30.0 40.70 17 -500.000 7.60 1.54390 56.0 40.70 18* -37.339 1.80 1.66100 20.4 40.70 HM2 19* 47.032 0.97 32.00 20 ∞ 0.12 1.58000 30.0 30.00 21 ∞ 0.12 1.48000 50.0 30.00 22 ∞ 0.70 1.51633 64.1 30.00 CG 23 ∞ 0.00 30.00 Image plane ∞ Aspheric data 5th page K = 1.18943e+00 A 4= 4.61666e-05 A 6=-9.20677e-08 A 8= 1.50417e-10 A10=-1.06309e-13 Page 6 K = 1.18943e+00 A 4= 4.61666e-05 A 6=-9.20677e-08 A 8= 1.50417e-10 A10=-1.06309e-13 Side 7 K = 0.00000e+00 A 4= 3.66249e-05 A 6=-8.66298e-08 A 8= 1.80074e-10 A10=-1.31416e-13 Side 10 K =-3.78982e+00 A 4=-4.53656e-06 A 6= 9.67519e-09 A 8=-1.05483e-11 A10=-5.73428e-15 Page 13 K = 0.00000e+00 A 4= 3.66249e-05 A 6=-8.66298e-08 A 8= 1.80074e-10 A10=-1.31416e-13 Side 14 K = 1.18943e+00 A 4= 4.61666e-05 A 6=-9.20677e-08 A 8= 1.50417e-10 A10=-1.06309e-13 Page 15 K = 0.00000e+00 A 4= 3.66249e-05 A 6=-8.66298e-08 A 8= 1.80074e-10 A10=-1.31416e-13 Side 18 K =-3.78982e+00 A 4=-4.53656e-06 A 6= 9.67519e-09 A 8=-1.05483e-11 A10=-5.73428e-15 Page 19 K = 0.00000e+00 A 4=-3.10636e-04 A 6= 2.38425e-06 A 8=-1.12488e-08 A10= 3.19668e-11 A12=-5.10860e-14 A14= 3.57845e-17 Various data Zoom ratio 1.00 Focal length 18.75 EPD 4.00 Half viewing angle 45.00 Image height 12.00 Lens length 16.51 (in G) BF 1.59 (in Air) d 1 15.00 Single lens data Lens starting surface focal length 1(Gn) 6 -478.57 2(gb) 9 73.76 3(Ga) 18 -31.22 4(CG) 22 0.00 (Numerical Example 5) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 (pupil plane) ∞ (variable) 4.00 2 ∞ 1.20 1.49171 57.4 26.50 3 ∞ 0.03 1.46000 50.0 26.50 4 ∞ 0.12 1.48000 50.0 26.50 5 ∞ 1.30 26.50 6* -42.712 0.05 1.56000 30.0 26.50 HM1(PBS) 7* -42.712 0.01 1.46000 50.0 26.50 8* -42.712 1.80 1.64220 22.4 26.50 Gn_Rn1 9* -65.681 0.15 26.50 10 ∞ 0.12 1.58000 30.0 29.50 (QWP1) 11 ∞ 0.03 1.46000 50.0 29.50 12 ∞ 6.85 1.54390 56.0 29.50 Ga 13* -32.358 -6.85 Reflective surface 29.50 Ga_HM2(HM) 14 ∞ -0.03 1.46000 50.0 29.50 15 ∞ -0.12 1.58000 30.0 29.50 (QWP1) 16 ∞ -0.15 29.50 17* -65.681 -1.80 1.64220 22.4 26.50 Gn 18* -42.712 -0.01 1.46000 50.0 26.50 Gn_Rn1 19* -42.712 0.01 Reflective surface 26.50 HM1 (PBS) 20* -42.712 1.80 1.64220 22.4 26.50 Gn_Rn1 21* -65.681 0.15 26.50 22 ∞ 0.12 1.58000 30.0 29.50 (QWP1) 23 ∞ 0.03 1.46000 50.0 29.50 24 ∞ 6.85 1.54390 56.0 29.50 Ga 25* -32.358 0.80 29.50 Ga_HM2(HM) 26 ∞ 0.12 1.58000 30.0 25.00 (QWP2) 27 ∞ 0.03 1.46000 50.0 25.00 28 ∞ 0.12 1.48000 50.0 25.00 (POL) 29 ∞ 0.03 1.46000 50.0 25.00 30 ∞ 0.70 1.51633 64.1 25.00 CG 31 ∞ 0.00 25.00 Image plane ∞ Aspheric data Page 6 K = 1.29488e+00 A 4= 5.99577e-05 A 6=-2.21058e-07 A 8= 8.69824e-10 A10=-1.52787e-12 Side 7 K = 1.29488e+00 A 4= 5.99577e-05 A 6=-2.21058e-07 A 8= 8.69824e-10 A10=-1.52787e-12 Side 8 K = 1.29488e+00 A 4= 5.99577e-05 A 6=-2.21058e-07 A 8= 8.69824e-10 A10=-1.52787e-12 9th page K = 0.00000e+00 A 4= 5.03478e-05 A 6=-2.45471e-07 A 8= 9.99789e-10 A10=-1.58083e-12 Page 13 K =-2.01312e-01 A 4= 4.72560e-06 A 6= 8.03175e-09 A 8=-1.30696e-11 A10= 3.34964e-14 Page 17 K = 0.00000e+00 A 4= 5.03478e-05 A 6=-2.45471e-07 A 8= 9.99789e-10 A10=-1.58083e-12 Side 18 K = 1.29488e+00 A 4= 5.99577e-05 A 6=-2.21058e-07 A 8= 8.69824e-10 A10=-1.52787e-12 Page 19 K = 1.29488e+00 A 4= 5.99577e-05 A 6=-2.21058e-07 A 8= 8.69824e-10 A10=-1.52787e-12 Page 20 K = 1.29488e+00 A 4= 5.99577e-05 A 6=-2.21058e-07 A 8= 8.69824e-10 A10=-1.52787e-12 Page 21 K = 0.00000e+00 A 4= 5.03478e-05 A 6=-2.45471e-07 A 8= 9.99789e-10 A10=-1.58083e-12 Page 25 K =-2.01312e-01 A 4= 4.72560e-06 A 6= 8.03175e-09 A 8=-1.30696e-11 A10= 3.34964e-14 Various data Focal length 14.62 EPD 4.00 Half viewing angle 40.00 Image height 9.00 Lens length 13.44 (in G) BF 1.45 (in Air) d 1 12.00 Single lens data Lens starting surface focal length 1(Gn) 8 -196.20 2(Ga) 12 59.49 3(CG) 30 0.00 (Numerical Example 6) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 (pupil plane) ∞ 12.00 4.00 2 ∞ 1.20 1.49171 57.4 26.50 3 ∞ 0.03 1.46000 50.0 26.50 4 ∞ 0.12 1.48000 50.0 26.50 5 ∞ 1.30 26.50 6* -42.650 1.80 1.64220 22.4 26.50 Gn_Rn1=HM1(PBS) 7* -65.093 0.15 26.50 8 ∞ 0.12 1.58000 30.0 29.50 (QWP1) 9 ∞ 0.03 1.46000 50.0 29.50 10 ∞ 6.85 1.54390 56.0 29.50 Ga 11* -32.357 -6.85 Reflective surface 29.50 Ga_HM2(HM) 12 ∞ -0.03 1.46000 50.0 29.50 13 ∞ -0.12 1.58000 30.0 29.50 (QWP1) 14 ∞ -0.15 29.50 15* -65.093 -1.80 1.64220 22.4 26.50 Gn 16* -42.650 1.80 Reflective surface 26.50 Gn_Rn1=HM1(PBS) 17* -65.093 0.15 26.50 18 ∞ 0.12 1.58000 30.0 29.50 (QWP1) 19 ∞ 0.03 1.46000 50.0 29.50 20 ∞ 6.85 1.54390 56.0 29.50 Ga 21* -32.357 0.80 29.50 Ga_HM2(HM) 22 ∞ 0.12 1.58000 30.0 25.00 (QWP1) 23 ∞ 0.03 1.46000 50.0 25.00 24 ∞ 0.12 1.48000 50.0 25.00 (POL) 25 ∞ 0.03 1.46000 50.0 25.00 26 ∞ 0.70 1.51633 64.1 25.00 CG 27 ∞ 0.00 25.00 Image plane ∞ Aspheric data Page 6 K = 1.28965e+00 A 4= 5.89925e-05 A 6=-2.09236e-07 A 8= 8.11541e-10 A10=-1.42208e-12 Side 7 K = 0.00000e+00 A 4= 5.17317e-05 A 6=-2.62931e-07 A 8= 1.08369e-09 A10=-1.70755e-12 Page 11 K =-2.51534e-01 A 4= 4.12029e-06 A 6= 1.02199e-08 A 8=-1.37709e-11 A10= 2.09374e-14 Page 15 K = 0.00000e+00 A 4= 5.17317e-05 A 6=-2.62931e-07 A 8= 1.08369e-09 A10=-1.70755e-12 Page 16 K = 1.28965e+00 A 4= 5.89925e-05 A 6=-2.09236e-07 A 8= 8.11541e-10 A10=-1.42208e-12 Page 17 K = 0.00000e+00 A 4= 5.17317e-05 A 6=-2.62931e-07 A 8= 1.08369e-09 A10=-1.70755e-12 Page 21 K =-2.51534e-01 A 4= 4.12029e-06 A 6= 1.02199e-08 A 8=-1.37709e-11 A10= 2.09374e-14 Various data Focal length 14.61 EPD 4.00 Half viewing angle 40.00 Image height 9.00 Lens length 13.38 (in G) BF 1.45 (in Air) d 1 12.00 Single lens data Lens starting surface focal length 1(Gn) 6 -198.86 2(Ga) 10 59.49 3(CG) 26 0.00 (Numerical Example 7) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 (pupil plane) ∞ (variable) 4.00 2 ∞ 1.20 1.49171 57.4 26.50 3 ∞ 0.03 1.46000 50.0 26.50 4 ∞ 0.12 1.48000 50.0 26.50 (POL) 5 ∞ 0.03 1.46000 50.0 26.50 6 ∞ 0.12 1.58000 30.0 26.50 (QWP2) 7∞ 1.30 26.50 8* -42.589 1.80 1.64220 22.4 26.50 Gn_Rn1=HM1(HM) 9* -64.509 0.15 26.50 10 ∞ 0.12 1.58000 30.0 29.50 (QWP1) 11 ∞ 0.03 1.46000 50.0 29.50 12 ∞ 6.85 1.54390 56.0 29.50 Ga 13* -32.350 0.01 1.46000 50.0 29.50 14* -32.350 -0.01 Reflective surface 29.50 Ga_HM2(PBS) 15* -32.350 -6.85 1.54390 56.0 29.50 Ga 16 ∞ -0.03 1.46000 50.0 29.50 17 ∞ -0.12 1.58000 30.0 29.50 (QWP1) 18 ∞ -0.15 29.50 19* -64.509 -1.80 1.64220 22.4 26.50 Gn 20* -42.589 1.80 Reflective surface 26.50 Gn_Rn1=HM1(HM) 21* -64.509 0.15 26.50 22 ∞ 0.12 1.58000 30.0 29.50 (QWP1) 23 ∞ 0.03 1.46000 50.0 29.50 24 ∞ 6.85 1.54390 56.0 29.50 Ga 25* -32.350 0.01 1.46000 50.0 29.50 26* -32.350 0.05 1.56000 30.0 29.50 Gn_Rn1=HM1(HM) 27* -32.350 0.82 29.50 28 ∞ 0.12 1.48000 50.0 25.00 29 ∞ 0.03 1.46000 50.0 25.00 30 ∞ 0.70 1.51633 64.1 25.00 CG 31 ∞ 0.00 25.00 Image plane ∞ Aspheric data Side 8 K = 1.29138e+00 A 4= 5.90837e-05 A 6=-2.11842e-07 A 8= 8.25953e-10 A10=-1.44470e-12 9th page K = 0.00000e+00 A 4= 5.27004e-05 A 6=-2.72125e-07 A 8= 1.11728e-09 A10=-1.73001e-12 Page 13 K =-2.60569e-01 A 4= 3.92869e-06 A 6= 1.04218e-08 A 8=-1.19360e-11 A10= 1.14498e-14 Side 14 K =-2.60569e-01 A 4= 3.92869e-06 A 6= 1.04218e-08 A 8=-1.19360e-11 A10= 1.14498e-14 Page 15 K =-2.60569e-01 A 4= 3.92869e-06 A 6= 1.04218e-08 A 8=-1.19360e-11 A10= 1.14498e-14 Page 19 K = 0.00000e+00 A 4= 5.27004e-05 A 6=-2.72125e-07 A 8= 1.11728e-09 A10=-1.73001e-12 Page 20 K = 1.29138e+00 A 4= 5.90837e-05 A 6=-2.11842e-07 A 8= 8.25953e-10 A10=-1.44470e-12 Page 21 K = 0.00000e+00 A 4= 5.27004e-05 A 6=-2.72125e-07 A 8= 1.11728e-09 A10=-1.73001e-12 Page 25 K =-2.60569e-01 A 4= 3.92869e-06 A 6= 1.04218e-08 A 8=-1.19360e-11 A10= 1.14498e-14 Page 26 K =-2.60569e-01 A 4= 3.92869e-06 A 6= 1.04218e-08 A 8=-1.19360e-11 A10= 1.14498e-14 Page 27 K =-2.60569e-01 A 4= 3.92869e-06 A 6= 1.04218e-08 A 8=-1.19360e-11 A10= 1.14498e-14 Various data Focal length 14.59 EPD 4.00 Half viewing angle 40.00 Image height 9.00 Lens length 13.46 (in G) BF 1.38 (in Air) d 1 12.00 Single lens data Lens starting surface focal length 1(Gn) 8 -201.64 2(Ga) 12 59.48 3(CG) 30 0.00

[0082] [Table 1]

[0083] [Display device] 17 is a schematic diagram of a head-mounted display (HMD) 1 as a display device using the optical system (observation optical system) of each embodiment. The HMD is worn on the head (in front of the eyes) of the observer by a mounting gear (not shown). The HMD has a right-eye display element RID, a left-eye display element LID, a right-eye optical system ROS that guides display light from the right-eye display element RID to the observer's right eye, and a left-eye optical system LOS that guides display light from the left-eye display element LID to the observer's left eye.

[0084] According to each embodiment, an optical system that can obtain high optical performance with excellent correction of chromatic aberration in a wide-field, compact optical system can be realized. Furthermore, by using the optical system of each embodiment as each of the right-eye optical system ROS and the left-eye optical system LOS, a display device that is compact and capable of viewing high-quality images over a wide viewing angle can be realized.

[0085] The disclosure of each embodiment includes the following configuration. (Configuration 1) An optical system that guides light from a display surface to a pupil plane, The optical system includes a first transmission-reflection member arranged in order from the pupil plane side to the display plane side, the first transmission-reflection member having a first transmission-reflection surface whose surface shape determined by the paraxial curvature is concave on the pupil plane side, a negative first lens having a pupil plane side surface whose surface shape determined by the paraxial curvature is concave on the pupil plane side, and a second lens having a second transmission-reflection surface whose surface shape determined by the paraxial curvature is concave on the pupil plane side, the light from the display surface is transmitted through the second transmissive-reflective surface, transmitted through the first lens, reflected by the first transmissive-reflective surface, transmitted through the first lens, reflected by the second transmissive-reflective surface, transmitted through the first lens, transmitted through the first transmissive-reflective surface, and reaches the pupil plane. (Configuration 2) 2. The optical system according to configuration 1, wherein the first transmission-reflection surface of the first transmission-reflection member is cemented to the pupil plane side of the first lens. (Configuration 3) 3. The optical system according to configuration 2, wherein the first transmitting-reflecting surface and the surface on the side of the pupil plane have substantially the same surface shape. (Configuration 4) 2. The optical system according to configuration 1, wherein the first transmitting-reflecting surface and the pupil plane side surface are a common surface. (Configuration 5) When the focal length of the first lens is fGn and the focal length of the optical system is f, 2<|fGn| / f<50 5. The optical system according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) When the refractive index of the material of the first lens at the d-line is NdGn, 1.4 <NdGn<1.8 6. The optical system according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 7) When the Abbe number of the material of the first lens at the d-line is νdGn, 10<νdGn<50 7. The optical system according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) When the paraxial radius of curvature of the pupil plane side surface of the first lens is Rna and the paraxial radius of curvature of the display plane side surface of the first lens is Rnb, 1≦(Rnb+Rna) / (Rnb-Rna)<30 8. The optical system according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) the second lens is a negative lens, 9. The optical system according to any one of configurations 1 to 8, wherein the second transmitting-reflecting surface is a pupil plane side surface of the second lens. (Configuration 10) When the focal length of the first lens is fGn and the focal length of the second lens is fGa, 3 <fGn / fGa<40 10. The optical system according to configuration 9, wherein the following condition is satisfied: (Configuration 11) 11. The optical system according to configuration 9 or 10, further comprising a positive third lens on the pupil plane side of the second lens. (Configuration 12) When the focal length of the second lens is fGa and the focal length of the third lens is fGb, 0.8 <fGb / |fGa|<3.5 12. The optical system according to configuration 11, wherein the following condition is satisfied: (Configuration 13) When the Abbe number of the material of the second lens at the d line is νdGa and the Abbe number of the material of the third lens at the d line is νdGb, 0.15<νdGa / νdGb<0.80 13. The optical system according to configuration 11 or 12, wherein the following condition is satisfied: (Configuration 14) 14. The optical system according to any one of configurations 11 to 13, wherein the second lens and the third lens are cemented together. (Configuration 15) a positive fourth lens on the pupil plane side of the first lens, 15. The optical system according to any one of configurations 11 to 14, wherein the first lens and the fourth lens are cemented together. (Configuration 16) the second lens is a positive lens, 9. The optical system according to any one of configurations 1 to 8, wherein the second transmissive-reflective surface is a surface on the display surface side of the second lens. (Configuration 17) When the focal length of the first lens is fGn and the focal length of the second lens is fGa, 1<|fGn| / fGa<10 17. The optical system according to configuration 16, wherein the following condition is satisfied: (Configuration 18) 18. The optical system according to any one of configurations 1 to 17, wherein at least one of the first transmission-reflection surface and the second transmission-reflection surface is configured by a polarization-selective transmission-reflection element. (Configuration 19) An optical system that guides light from a display surface to a pupil plane, a first transmission-reflection member having a first transmission-reflection surface, a negative first lens, and a second lens having a second transmission-reflection surface, which are arranged in this order from the pupil plane side to the display surface side; the light from the display surface is transmitted through the second transmissive-reflective surface, transmitted through the first lens, reflected by the first transmissive-reflective surface, transmitted through the first lens, reflected by the second transmissive-reflective surface, transmitted through the first lens, transmitted through the first transmissive-reflective surface, and reaches the pupil plane. (Configuration 20) 20. A display device comprising the optical system according to any one of configurations 1 to 19 and a display element.

[0086] 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 invention. [Explanation of symbols]

[0087] SP pupil plane ID display surface HM1 Transmissive reflective surface (1st transmissive reflective surface) HM2 Transmissive reflective surface (second transmissive reflective surface) R1n Observation side (pupil side) Gn negative lens (first lens) Ga lens (second lens)

Claims

1. An optical system that guides light from a display surface to a pupil plane, the lens includes a first transmission-reflection member arranged in order from the pupil plane side to the display plane side, the first transmission-reflection member having a first transmission-reflection surface whose surface shape determined by the paraxial curvature is concave on the pupil plane side; a negative first lens having a pupil plane side surface whose surface shape determined by the paraxial curvature is concave on the pupil plane side; and a second lens having a second transmission-reflection surface whose surface shape determined by the paraxial curvature is concave on the pupil plane side; the light from the display surface is transmitted through the second transmissive-reflective surface, transmitted through the first lens, reflected by the first transmissive-reflective surface, transmitted through the first lens, reflected by the second transmissive-reflective surface, transmitted through the first lens, transmitted through the first transmissive-reflective surface, and reaches the pupil plane.

2. 2. The optical system according to claim 1, wherein the first transmission-reflection surface of the first transmission-reflection member is cemented to a surface of the first lens facing the pupil plane.

3. 3. The optical system according to claim 2, wherein the first transmitting-reflecting surface and the surface on the side of the pupil plane have substantially the same surface shape.

4. 2. The optical system according to claim 1, wherein the first transmissive-reflective surface and the pupil plane side surface are a common surface.

5. When the focal length of the first lens is fGn and the focal length of the optical system is f, 2<|fGn| / f<50 2. The optical system according to claim 1, wherein the following condition is satisfied:

6. When the refractive index of the material of the first lens at the d-line is NdGn, 1.4<NdGn<1.8 2. The optical system according to claim 1, wherein the following condition is satisfied:

7. When the Abbe number of the material of the first lens at the d line is νdGn, 10<νdGn<50 2. The optical system according to claim 1, wherein the following condition is satisfied:

8. When the paraxial radius of curvature of the pupil plane side surface of the first lens is Rna and the paraxial radius of curvature of the display plane side surface of the first lens is Rnb, 1≦(Rnb+Rna) / (Rnb-Rna)<30 2. The optical system according to claim 1, wherein the following condition is satisfied:

9. the second lens is a negative lens, 9. The optical system according to claim 1, wherein the second transmitting / reflecting surface is a surface on a side of the second lens facing a pupil plane.

10. When the focal length of the first lens is fGn and the focal length of the second lens is fGa, 3<fGn / fGa<40 10. The optical system according to claim 9, wherein the following condition is satisfied:

11. 10. The optical system according to claim 9, further comprising a positive third lens on the pupil plane side of the second lens.

12. When the focal length of the second lens is fGa and the focal length of the third lens is fGb, 0.8<fGb / |fGa|<3.5 12. The optical system according to claim 11, wherein the following condition is satisfied:

13. When the Abbe number of the material of the second lens at the d line is νdGa and the Abbe number of the material of the third lens at the d line is νdGb, 0.15<νdGa / νdGb<0.80 12. The optical system according to claim 11, wherein the following condition is satisfied:

14. The optical system according to claim 11 , wherein the second lens and the third lens are cemented together.

15. a positive fourth lens on the pupil plane side of the first lens, The optical system according to claim 11 , wherein the first lens and the fourth lens are cemented together.

16. the second lens is a positive lens, 9. The optical system according to claim 1, wherein the second transmissive-reflective surface is a display surface side surface of the second lens.

17. When the focal length of the first lens is fGn and the focal length of the second lens is fGa, 1<|fGn| / fGa<10 17. The optical system according to claim 16, wherein the following condition is satisfied:

18. 9. The optical system according to claim 1, wherein at least one of the first transmission-reflection surface and the second transmission-reflection surface is configured by a polarization-selective transmission-reflection element.

19. An optical system that guides light from a display surface to a pupil plane, a first transmission-reflection member having a first transmission-reflection surface, a negative first lens, and a second lens having a second transmission-reflection surface, which are arranged in this order from the pupil plane side to the display surface side; the light from the display surface is transmitted through the second transmissive-reflective surface, transmitted through the first lens, reflected by the first transmissive-reflective surface, transmitted through the first lens, reflected by the second transmissive-reflective surface, transmitted through the first lens, transmitted through the first transmissive-reflective surface, and reaches the pupil plane.

20. 20. A display device comprising the optical system according to claim 1 and a display element.

Images