Optical systems and display devices

Abstract

There is a need for optical systems for displays that have good optical performance. [Solution] The optical system includes a cemented lens formed by joining at least three lenses, including a negative lens Gn, and a first transmission-reflecting surface HM1 and a second transmission-reflecting surface HM2, each having a concave shape on the observation side in the paraxial direction. At least one of the first and second transmission-reflecting surfaces is located at the cemented surface of the cemented lens. Image light is guided to the observation side through transmission at the second transmission-reflecting surface, reflection at the first transmission-reflecting surface, reflection at the second transmission-reflecting surface, and transmission at the first transmission-reflecting surface. When the Abbe number of the negative lens is νdGn, the focal length of the negative lens is fGn, the focal length of the optical system is f, the paraxial radius of curvature of the first transmission-reflecting surface is R_HM1, and the paraxial radius of curvature of the second transmission-reflecting surface is R_HM2, then 10.0 ≤ νdGn ≤ 50.0, -10.0 ≤ fGn / f ≤ -1.0 and 0.0

Description

Technical Field

[0001] The present invention relates to an optical system suitable for display devices such as head-mounted displays (HMDs) and smart glasses.

Background Art

[0002] As an optical system of the above type, Patent Document 1 discloses an optical system having two transflective surfaces and a cemented lens formed by cementing three lenses together.

Prior Art Literature

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] There is a demand for an optical system that is more improved than conventional ones.

Means for Solving the Problem

[0005] An optical system as one aspect of the present invention guides image light from a display element to an observation side. The optical system includes a cemented lens formed by cementing at least three lenses including a negative lens, and a first transflective surface and a second transflective surface each having a concave shape toward the observation side in the paraxial region. At least one of the first and second transflective surfaces is arranged on a cemented surface of the cemented lens. The image light is guided to the observation side through transmission at the second transflective surface, reflection at the first transflective surface, reflection at the second transflective surface, and transmission at the first transflective surface. When νdGn is the Abbe number of the negative lens based on the d-line, fGn is the focal length of the negative lens in refraction in air, f is the focal length of the optical system, R_HM1 is the paraxial radius of curvature of the first transflective surface, and R_HM2 is the paraxial radius of curvature of the second transflective surface, 10.0≦νdGn≦50.0 -10.0≦fGn / f≦-1.0 0.0 <R_HM2 / R_HM1≦1.0 It is characterized by satisfying the following conditions. Furthermore, a display device having the above-mentioned optical system and display element also constitutes another aspect of the present invention. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide an optical system having good optical performance. [Brief explanation of the drawing]

[0007] [Figure 1] Cross-sectional view of the optical system of Example 1. [Figure 2] Longitudinal aberration diagram of the optical system in Example 1. [Figure 3] Cross-sectional view of the optical system in Example 2. [Figure 4] Longitudinal aberration diagram of the optical system in Example 2. [Figure 5] Cross-sectional view of the optical system of Example 3. [Figure 6] Longitudinal aberration diagram of the optical system in Example 3. [Figure 7] Cross-sectional view of the optical system of Example 4. [Figure 8] Longitudinal aberration diagram of the optical system in Example 4. [Figure 9] Cross-sectional view of the optical system of Example 5. [Figure 10] Longitudinal aberration diagram of the optical system in Example 5. [Figure 11] Cross-sectional view of the optical system of Example 6. [Figure 12] Longitudinal aberration diagram of the optical system in Example 6. [Figure 13] A diagram showing polarization utilization configuration 1. [Figure 14] A diagram showing polarization utilization configuration 2. [Figure 15] A diagram showing an HMD using the optical systems of Examples 1 to 6. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0009] Figure 1, Figure 3, Figure 5, Figure 7, Figure 9 and Figure 11 respectively show the configurations of the optical systems of Examples 1 to 6. The optical system of each example is an optical system that guides image light from a display element (display surface ID) to the observation side (exit pupil side or the observer's eye). More specifically, it is an optical system that enlarges an image displayed on a display element and presents the enlarged image to an observer in a display device such as an HMD or smart glasses.

[0010] In such an optical system, when an electronic device such as an LCD is used as the display element, the lateral chromatic aberration of the optical system can be electronically corrected by adjusting the magnification of the image displayed for each of the RGB color channels in the display element. However, chromatic aberration occurring within each RGB color channel cannot be electronically corrected. For this reason, when a high-definition display element with a narrow pixel pitch is used as the display element, the image quality of the displayed image may be degraded due to the chromatic aberration of the optical system.

[0011] Patent Document 1 discloses a configuration example in which a plano-concave lens is arranged in an optical system in Figure 6. The role of the plano-concave lens in this configuration example is to minimize the stress acting on the quarter-wave plate by arranging the quarter-wave plate on the flat surface of the lens. Further, Patent Document 1 discloses a configuration that minimizes stress by arranging a quarter-wave plate on a cylindrical surface in Figures 7 to 9. In such a configuration, in order to correct chromatic aberration of the optical system, the lens on the observation side and the lens on the display element side of the surface on which the quarter-wave plate is arranged need to be formed of optical materials having different refractive indices and Abbe numbers. At this time, if different materials are used for the lens on the observation side and the lens on the display element side of the cylindrical surface, asymmetric aberration occurs due to the refractive action of the cylindrical surface. On the other hand, if the same material is used for the lens on the observation side and the lens on the display element side of the cylindrical surface, chromatic aberration cannot be corrected.

[0012] Accordingly, the optical system of each embodiment has a cemented lens formed by cementing at least three lenses including a negative lens Gn. By using this cemented lens, the chromatic aberration of the entire optical system can be favorably corrected, and the number of lens surfaces that are in contact with air among the lens surfaces of the three lenses is minimized, so that unnecessary light (ghost) generated by reflection on the lens surfaces can be reduced. Furthermore, by using the negative lens Gn, the chromatic aberration of the entire optical system can be favorably corrected. The number of lenses constituting the cemented lens may be four or more.

[0013] In addition, the optical system of each embodiment has a first transflective surface (hereinafter abbreviated as HM1) and a second transflective surface (hereinafter abbreviated as HM2), each having a concave shape on the observation side in the paraxial region. HM2 and HM1 are arranged in this order from the display element side or the observation side. "Having a concave shape on the observation side in the paraxial region" means that the r term of the equation representing the aspherical shape in the numerical examples described later is negative. Specifically, it means that the reference spherical surface in the region near the optical axis, for example, at a height of about 1 / 10 of the effective diameter, is a concave surface facing the observation side. More specifically, it means that the shape of the reference spherical surface at a height of about half (2 mm) of Φ4 mm, which is the standard pupil diameter of an observer, is a concave surface facing the observation side. The effective diameter is the diameter of the region of the optical surface through which light rays contributing to image display pass. The reference spherical surface is a spherical surface determined by the surface vertex on the optical axis and the coordinates of the surface at a height of about 1 / 10 of the effective diameter. By using such HM1 and HM2, each lens surface has a concentric shape with respect to the pupil of the observer, and field curvature and astigmatism can be favorably corrected in the optical system with a wide viewing angle.

[0014] The display element is not limited to a panel-shaped electronic device that displays a two-dimensional image such as an LCD, and includes those having a light source that emits laser light or LED light and a scanning device that two-dimensionally scans the light from the light source.

[0015] Furthermore, in the optical system of each embodiment, at least one of HM1 and HM2 is placed on the bonding surface of the bonded lens. This prevents the transmission-reflective surface placed on the bonding surface from directly contacting the external environment. Therefore, when a half-mirror or film-shaped element made of metal or dielectric multilayer film is used as the transmission-reflective surface, the film or film can be stably positioned within the optical system in response to changes in the external environment such as temperature and humidity.

[0016] The optical systems in each embodiment using HM1 and HM2 form a triple-pass optical path that guides image light from the display element to the observation side via transmission through HM2, reflection through HM1, reflection through HM2, and transmission through HM1. By employing such a triple-pass optical path in which the image light travels three times between HM1 and HM2, the optical system can be made thinner by folding the optical path.

[0017] Here, the Abbe number νdGn is defined as the d-line of the optical material of the negative lens Gn. The definition of the Abbe number with respect to the d-line will be described later. Also, the focal length of the negative lens Gn in refraction in air is denoted as fGn. The focal length of the negative lens Gn in refraction here does not include the focal length of reflection when a transmitting and reflecting surface is placed on the lens surface of the negative lens Gn. Furthermore, the focal length of the entire optical system is denoted as f, the paraxial radius of curvature of HM1 is R_HM1, and the paraxial radius of curvature of HM2 is R_HM2. In this case, it is preferable that the optical system of each embodiment satisfies at least one of the following conditions of equations (1), (2), and (3).

[0018] 10.0 ≤ νdGn ≤ 50.0 (1) -10.0 ≤ fGn / f ≤ -1.0 (2) 0.0 <R_HM2 / R_HM1≦1.0 (3) The conditions in equation (1) indicate the appropriate Abbe number range for the negative lens Gn. By using an optical material with an appropriate Abbe number for the negative lens Gn, both monochromatic and chromatic aberration correction can be achieved. If νdGn falls below the lower limit of equation (1), the Abbe number of the negative lens Gn is too small, resulting in overcorrection of chromatic aberration. Moreover, the amount of light absorbed by the optical material of the negative lens Gn in the visible light region increases, reducing the transmittance of the entire optical system, which is undesirable. If νdGn exceeds the upper limit of equation (1), the Abbe number of the negative lens Gn is too large, resulting in undercorrection of chromatic aberration, making it difficult to achieve both monochromatic and chromatic aberration correction, which is also undesirable.

[0019] Furthermore, it is more preferable to set the lower limit of formula (1) to 12.0, 15.0, 18.0, or 20.0. Also, it is more preferable to set the upper limit of formula (1) to 45.0, 40.0, 35.0, or 30.0.

[0020] The conditions in equation (2) indicate an appropriate relationship between the focal length of the negative lens Gn and the focal length of the entire optical system. When fGn / f satisfies the conditions in equation (2), the refractive power of the negative lens Gn within the optical system is optimized, enabling both correction of chromatic aberration and miniaturization of the optical system. If fGn / f falls below the lower limit of equation (2), the negative refractive power of the negative lens Gn becomes too large compared to the focal length of the entire system, resulting in overcorrection of chromatic aberration in the entire optical system, which is undesirable. Alternatively, the focal length of the entire system becomes too large, resulting in a larger optical system, which is also undesirable. If fGn / f exceeds the upper limit of equation (2), the negative refractive power of the negative lens Gn becomes too small compared to the focal length of the entire system, resulting in insufficient correction of chromatic aberration in the entire optical system, which is also undesirable. Alternatively, the focal length of the entire system becomes too small, making it difficult to correct monochromatic aberrations such as field curvature in the entire optical system, which is also undesirable.

[0021] Furthermore, it is more preferable to set the lower limit of equation (2) to -8.0, -6.0, -5.0, or -3.0. Also, it is more preferable to set the upper limit of equation (2) to -1.5, -2.0, -2.5, or -4.0.

[0022] The conditions in equation (3) indicate an appropriate relationship between the paraxial radii of curvature of HM1 and HM2. In the optical system of each embodiment, HM1 has negative optical power (reciprocal of the focal length) in reflection, and HM2 has positive optical power in reflection. By optimizing the arrangement of each transmitted reflective surface, it is possible to achieve both a wide field of view (high optical magnification) and correction of field curvature and astigmatism. If R_HM2 / R_HM1 falls below the lower limit of equation (3), the radius of curvature of HM1 becomes too large relative to the radius of curvature of HM2. As a result, the negative optical power that HM1 contributes to by reflection becomes too weak, making it difficult to correct field curvature, which is undesirable. If R_HM2 / R_HM1 exceeds the upper limit of equation (3), the radius of curvature of HM1 becomes too small relative to the radius of curvature of HM2. As a result, the negative optical power borne by HM1 through reflection becomes too strong, making it difficult to widen the field of view of the optical system, which is undesirable. Alternatively, in order to maintain the field of view (magnification) of the optical system, it becomes necessary to make the radius of curvature of HM2 smaller, which is undesirable because it increases the aberration sensitivity of HM2 too much.

[0023] Furthermore, it is more preferable to set the lower limit of equation (3) to 0.2, 0.4, or 0.5. Also, it is more preferable to set the upper limit of equation (3) to 0.95, 0.9, or 0.8.

[0024] Furthermore, it is preferable that the optical system of each embodiment satisfies at least one of the following configurations a to f and the conditions of equations (4) and (5).

[0025] (Configuration a) In each embodiment, it is preferable to place the negative lens Gn between HM1 and HM2. With this configuration, the negative lens Gn is placed in the triple pass. In this case, the negative lens Gn bears the negative refractive power (reciprocal of the focal length) for three passes, so chromatic aberration in the entire optical system can be corrected well.

[0026] (configuration b) In each embodiment, it is preferable that the negative lens Gn has a plano-concave shape. By configuring one side of the negative lens Gn as a plane, when employing the polarization utilization configuration described later, a quarter-wave plate can be placed on the plane, and the stress acting on the quarter-wave plate can be reduced.

[0027] (configuration c) In each embodiment, it is preferable that the negative lens Gn is provided on the display element side of HM2. With this configuration, the negative lens Gn is positioned in a single-pass region through which image light passes only once. In the polarization utilization configuration described later, unwanted light leakage occurs due to birefringence of the lens in the optical path of polarized light. By positioning the negative lens Gn, which is made of a resin lens material that satisfies equation (1), in a single-pass region, the effect of birefringence of the lens can be reduced.

[0028] (configuration d) In each embodiment, it is preferable to place HM1 on the bonding surface of the cemented lens. HM1, which is positioned on the observation side of the optical system, may be in a position where the observer can directly touch it. By placing HM1 on the bonding surface of the cemented lens, it is possible to avoid the observer directly touching HM1. In addition, HM1 can be stably positioned in response to changes in the external environment.

[0029] (configuration e) In each embodiment, it is preferable to place lens Ga as an intermediate lens between HM1 and HM2. Furthermore, when the Abbe number referenced to the d line of lens Ga is νdGa, it is preferable that the following condition of equation (4) is satisfied.

[0030] 40.0 ≤ νdGa ≤ 90.0 (4) In this configuration, lens Ga is placed in the triple pass. By forming lens Ga from a lens material that satisfies equation (4), it is possible to reduce the occurrence of chromatic aberration while ensuring the transmittance of the entire optical system, and to achieve both a wide field of view and aberration correction of the optical system.

[0031] If νdGa falls below the lower limit of equation (4), the Abbe number of lens Ga becomes too small, resulting in excessively large chromatic aberration during triple-pass refraction, which is undesirable. Furthermore, if lens Ga is replaced with a resin lens to reduce the weight of the optical system, the amount of light absorbed by the optical material in the visible light region increases, reducing the overall transmittance of the optical system, which is also undesirable. If νdGa exceeds the upper limit of equation (4), the Abbe number of lens Ga becomes too large. As a result, although the chromatic aberration during refraction is small, the optical material satisfying the conditions of equation (4) has too low a refractive index, making it difficult to achieve both a wide field of view and aberration correction in the optical system, which is also undesirable.

[0032] Furthermore, it is more preferable to set the lower limit of equation (4) to 45.0, 50.0, or 52.0. Also, it is more preferable to set the upper limit of equation (4) to 80.0, 70.0, or 60.0.

[0033] (configuration f) In the above configuration e, when the focal length of lens Ga in refraction in air is fGa, it is preferable that the following condition of equation (5) is satisfied.

[0034] 1.0 ≤ fGa / f ≤ 100.0 (5) The condition in equation (5) assumes that lens Ga, placed in the triple-pass system, is a positive lens and indicates its appropriate refractive power. By appropriately setting the positive refractive power of lens Ga, it is possible to achieve both a wide field of view and chromatic aberration correction in the optical system.

[0035] If fGa / f falls below the lower limit of equation (5), the positive refractive power of lens Ga is too high, resulting in excessive chromatic aberration during refraction in the triple pass, which is undesirable. If fGa / f exceeds the upper limit of equation (5), the positive refractive power of lens Ga is too low, resulting in excessively low positive refractive power during refraction in the triple pass. This is undesirable because it makes it difficult to widen the field of view of the optical system.

[0036] Furthermore, it is more preferable to set the lower limit of equation (5) to 2.0, 3.0, 10.0, 15.0, or 18.0. Also, it is more preferable to set the upper limit of equation (5) to 80.0, 60.0, 40.0, or 35.0.

[0037] As another preferred configuration, at least one of HM1 and HM2 may be made of a polarization-selective transmission-reflection element. This allows for the reduction of unwanted light (leakage light) such as ghosting by adopting the polarization utilization configuration described later. Examples of polarization-selective transmission-reflection elements include wire grid elements such as Asahi Kasei's WGF, reflective linear polarizers such as 3M's IQP-E, and circular polarizers using cholesteric liquid crystals. When using a reflective linear polarizer, a quarter-wave plate is placed between HM1 and HM2.

[0038] Furthermore, various methods can be selected for arranging each polarizing element, such as HM1 and HM2, including methods such as bonding film-like polarizing elements to the lens surface, or integrally molding a wire grid structure with the lens base material during the molding of the resin lens.

[0039] The following describes the configuration utilizing polarization. By adopting this configuration, it is possible to suppress the decrease in the amount of light in the normal optical path of the image light within the optical system, while reducing unwanted light that passes through without being reflected even once at the transmission and reflection surfaces and heads toward the observation side.

[0040] [Polarization Utilization Configuration 1] Figure 13 shows polarization utilization configuration 1. In this configuration, a polarization-selective transmission and reflection element (PBS) A, which is HM1, is placed on the observation side (pupil surface SP side), and a half mirror (HM) C, which is HM2, is placed on the display element side (display surface ID side). A first quarter-wave plate (QWP1) B is placed between the PBS and the HM. A second quarter-wave plate (QWP2) D and a linear polarizer (POL) E are placed between the HM and the ID, from the HM side.

[0041] A PBS is configured to reflect linearly polarized light with the same polarization direction as the linearly polarized light transmitted through the POL, and to transmit linearly polarized light with a polarization direction perpendicular to that linearly polarized light. A PBS is, for example, a wire grid polarizer or a reflective polarizer with a phase difference film laminate configuration. In this case, the wire grid forming surface or phase difference film surface of the PBS functions as a transmitting and reflecting surface.

[0042] QWP1 and QWP2 are positioned so that their slow phase axes are tilted 45° with respect to the polarization transmission axis of the POL. Alternatively, it is preferable that QWP1 and QWP2 are positioned so that their respective slow phase axes are tilted 90° relative to each other. This arrangement cancels out the wavelength dispersion characteristics of QWP1 and QWP2 when light passes through them.

[0043] HM is a half-mirror formed, for example, by dielectric multilayer film or metal deposition. The ratio of reflectance to transmittance of the half-mirror is preferably 50:50 from the viewpoint of the transmittance of the entire optical system, but other ratios are also acceptable. POL is, for example, an absorption-type linear polarizer.

[0044] The image light emitted from the ID as unpolarized light becomes first linearly polarized light in the POL, and this first linearly polarized light is converted to first circularly polarized light by QWP2 and incident on HM. A portion of the first circularly polarized light incident on HM is reflected by HM and becomes second circularly polarized light with a polarization direction opposite to that of the first circularly polarized light, and this second circularly polarized light returns to QWP2. The second circularly polarized light that returns to QWP2 is converted to second linearly polarized light with a polarization direction perpendicular to the polarization direction of the first linearly polarized light. The second linearly polarized light returns to POL and is absorbed by POL.

[0045] On the other hand, the first circularly polarized light transmitted through HM is converted by QWP1 into a third linearly polarized light with the same polarization direction as the first linearly polarized light, and this third linearly polarized light is incident on PBS. The third linearly polarized light incident on PBS is reflected by the polarization selectivity of PBS.

[0046] The third linearly polarized light reflected by PBS is converted by QWP1 to a third circularly polarized light with the same rotation as the first circularly polarized light. The third circularly polarized light is incident on HM and reflected, becoming a fourth circularly polarized light with the opposite rotation to the third circularly polarized light. The fourth circularly polarized light is incident on QWP1 and converted to a fourth linearly polarized light with a polarization direction perpendicular to the polarization direction of the third linearly polarized light. The fourth linearly polarized light is incident on PBS and, due to the polarization selectivity of PBS, is transmitted through it and guided to SP.

[0047] Due to the optical effects described above, only the light that passes through HM (HM1), is reflected by PBS (HM2), is reflected by HM again, and passes through PBS is guided to SP and enters the observer's eye (pupil) positioned at SP.

[0048] [Polarization Utilization Configuration 2] Figure 14 shows polarization utilization configuration 2. In this configuration, a polarization-selective transmission / reflection element (PBS) A, designated as HM2, is located on the display element side (display surface ID side), and a half mirror (HM) C, designated as HM1, is located on the observation side (pupil surface SP side). A first quarter-wave plate (QWP1) B is placed between the PBS and the HM. A second quarter-wave plate (QWP2) D and a linear polarizer (POL) E are placed between the HM and SP, in order from the HM side. The configuration of each element and the orientation of the preferred optical axis are the same as in the first configuration.

[0049] Image light, emitted from the ID as unpolarized light, is incident on the PBS. Of the unpolarized light incident on the PBS, the first linearly polarized light with a polarization direction perpendicular to the transmission axis of the POL is transmitted through it. The first linearly polarized light transmitted through the PBS is converted to first circularly polarized light by QWP1, and this first circularly polarized light is incident on the HM. A portion of the first circularly polarized light incident on the HM is transmitted through it and incident on QWP2, where it is converted to second linearly polarized light with the same polarization direction as the first linearly polarized light. The second linearly polarized light is incident on the POL and absorbed by the POL.

[0050] On the other hand, the first circularly polarized light is reflected by HM, becoming a second circularly polarized light with a polarization direction opposite to that of the first circularly polarized light. The second circularly polarized light returns to QWP1. The second circularly polarized light that returns to QWP1 is converted by QWP1 into a third linearly polarized light with a polarization direction perpendicular to the polarization direction of the first linearly polarized light. The third linearly polarized light returns to PBS. The third linearly polarized light that returns to PBS is reflected by PBS and returns to QWP1 again, where it is converted into a third circularly polarized light with a polarization direction equal to that of the first circularly polarized light. The third circularly polarized light is again incident on HM, passes through it, and is incident on QWP2, where it is converted by QWP2 into a fourth linearly polarized light with a polarization direction parallel to the transmission axis of POL. The fourth linearly polarized light passes through POL and is led to SP.

[0051] Due to the optical effects described above, only the light that passes through PBS (HM2), is reflected by HM (HM1), reflected again by PBS, and passes through HM is guided to SP and incident on the observer's eye, which is positioned at SP.

[0052] In the two polarization utilization configurations described above, it is preferable to add and arrange various polarizing elements to reduce the reflection component of unwanted light in the PBS and display surface ID. For example, in Figure 13, by placing an absorbing linear polarizer having a transmission axis in the same direction as the transmission axis of the PBS on the observation side of the PBS, the reflection of ambient light in the PBS can be reduced. Also, in Figure 14, by placing a phase plate between the PBS and the display surface ID, the reflection component of unwanted light in the display surface ID can be reduced. As the phase plate, it is preferable to use a quarter-wave plate or the like having a transmission axis tilted at 45° with respect to the transmission axes of the POL and PBS.

[0053] Furthermore, in each embodiment, the optical material of each lens may be a resin material. Using a resin material for the optical material is advantageous in terms of weight reduction compared to using a glass material.

[0054] Furthermore, in each embodiment, diopter adjustment is possible using various methods. For example, diopter adjustment can be performed by moving the entire optical system or the display element in the direction in which the optical axis of the optical system extends (left-right direction in each figure). In addition to moving the optical system along the optical axis, diopter adjustment is also possible by providing optical elements that change refractive power through mechanical or electrical action, such as variable-shape lenses or liquid crystal lenses that utilize pressure or electrowetting.

[0055] The optical systems of Examples 1 to 6 will be described in detail below. Following Example 6, numerical examples 1 to 6 corresponding to each of Examples 1 to 6 are shown. [Examples]

[0056] The optical system of Example 1 (Numerical Example 1) shown in Figure 1 is an optical system with a total field of view of approximately 90°. The optical system of Example 1 has a biconvex first lens with positive refractive power, a plano-concave second lens with negative refractive power (negative lens Gn), and a plano-convex third lens with positive refractive power (lens Ga), arranged in order from the pupil plane SP side to the display surface ID side. The first, second, and third lenses are joined together to form a cemented lens. HM1 is placed on the bonding surface between the first and second lenses, and HM2 is placed on the lens surface of the third lens on the display surface side. The negative lens Gn, which is the second lens, is placed between HM1 and HM2.

[0057] Image light from the display surface ID passes through HM2, is reflected by HM1, reflected again by HM2, passes through HM1, and is guided to the pupil surface SP.

[0058] In this embodiment, the polarization utilization configuration 1 described above is adopted, with a reflective polarizing film (PBS) used as HM1 and a half mirror (HM) used as HM2. A quarter-wave plate (QWP1) is placed at the bonding surface of the second and third lenses. Furthermore, the quarter-wave plate (QWP2) and a linear polarizer (POL) are bonded to the pupil surface SP side of the glass block (cover glass) CG that covers the display surface ID. In addition, a linear polarizer is placed on the lens surface on the pupil surface SP side of the first lens to reduce the reflection of external light by the reflective polarizing film.

[0059] The values ​​of equations (1) to (5) in numerical example 1 are summarized in Table 1. The optical system in numerical example 1 satisfies all the conditions of equations (1) to (5).

[0060] Figure 2 shows the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) in the optical system of Numerical Example 1 (diopter: -0.77 diopters). In the spherical aberration diagram, EPD represents the pupil diameter, the solid line represents the spherical aberration relative to the d line, the long dashed line represents the spherical aberration relative to the C line, and the dashed line represents the spherical aberration relative to the F line. In the astigmatism diagram, the solid line ΔS represents the astigmatism at the sagittal image plane, and the dashed line ΔM represents the astigmatism at the meridional image plane. The distortion diagram shows the distortion at the d line. The chromatic aberration diagram shows the chromatic aberration relative to the C line (long dashed line) and the F line (dashed line). ω is the half-field angle (°). The explanations for these longitudinal aberration diagrams are the same for other numerical examples. [Examples]

[0061] The optical system of Example 2 (Numerical Example 2) shown in Figure 3 has a total field of view of approximately 95°. The basic configuration of the optical system of Example 2 is the same as that of Example 1. However, compared to Example 1, the size of the display element has been increased, and the second lens (negative lens Gn) has been changed from a plano-concave shape to a meniscus shape with a convex surface facing the display surface.

[0062] The polarization utilization configuration and the optical path of the image light guided from the display surface ID to the pupil surface SP are the same as in Example 1.

[0063] The values ​​of equations (1) to (5) in numerical example 2 are summarized in Table 1. The optical system in numerical example 2 satisfies all the conditions of equations (1) to (5).

[0064] Figure 4 shows the longitudinal aberrations in the optical system of numerical example 2. [Examples]

[0065] The optical system of Example 3 (Numerical Example 3) shown in Figure 5 has a total field of view of approximately 110°. The basic configuration of the optical system of Example 3 is the same as that of Example 1. However, the size of the display element is larger compared to Example 1.

[0066] The polarization utilization configuration and the optical path of the image light guided from the display surface ID to the pupil surface SP are the same as in Example 1. However, in this example, the linear polarizer that was placed on the observation-side lens surface of the first lens in Example 1 is laminated with a reflective polarizing film (PBS) and placed on the bonding surface of the first lens and the second lens.

[0067] The values ​​of equations (1) to (5) in numerical example 3 are summarized in Table 1. The optical system in numerical example 3 satisfies all the conditions of equations (1) to (5).

[0068] Figure 6 shows the longitudinal aberrations in the optical system of numerical example 3. [Examples]

[0069] The optical system of Example 4 (Numerical Example 4) shown in Figure 7 is an optical system with a total field of view of approximately 95°. The optical system of Example 4 has a first lens with a plano-convex shape and positive refractive power, arranged in order from the pupil plane SP side to the display plane ID side, a second lens (lens Ga) with a convex meniscus shape and positive refractive power facing the display plane side, and a third lens (negative lens Gn) with a biconcave shape in the paraxial region and negative refractive power. The first, second, and third lenses are joined together to form a cemented lens.

[0070] HM1 is positioned at the junction of the first and second lenses, and HM2 is positioned at the junction of the second and third lenses. In addition, the negative lens Gn is positioned on the display surface ID side of HM2.

[0071] Image light from the display surface ID passes through HM2, is reflected by HM1, reflected again by HM2, passes through HM1, and is guided to the pupil surface SP.

[0072] This embodiment also employs polarization utilization configuration 1. Specifically, a reflective polarizing film (PBS) is used as HM1 and is placed together with a quarter-wave plate (QWP1) at the junction of the first and second lenses. In addition, a half-mirror (HM) is used as HM2.

[0073] Furthermore, the quarter-wave plate (QWP2) and the linear polarizer (POL) are bonded to the pupil-side SP side of the glass block CG. In addition, the linear polarizer is placed on the lens surface on the pupil-side SP side of the first lens to reduce the reflection of external light from the reflective polarizing film.

[0074] The values ​​of equations (1) to (5) in numerical example 4 are summarized in Table 1. The observation optical system in numerical example 4 satisfies all the conditions of equations (1) to (5).

[0075] Figure 8 shows the longitudinal aberration in the optical system of numerical example 4. [Examples]

[0076] The optical system of Example 5 (Numerical Example 5) shown in Figure 9 has a total field of view of approximately 100°. The basic configuration of the optical system of Example 5 is the same as that of Example 4. However, compared to Example 4, the field of view and lens material have been changed, and the first lens has been changed to a biconvex shape.

[0077] The polarization utilization configuration and the optical path of the image light guided from the display surface ID to the pupil surface SP are the same as in Example 4. However, in this example, the linear polarizer that was placed on the lens surface on the pupil surface SP side of the first lens in Example 4 is laminated with a reflective polarizing film (PBS) and placed on the bonding surface of the first lens and the second lens.

[0078] The values ​​of equations (1) to (5) in numerical example 5 are summarized in Table 1. The observation optical system in numerical example 5 satisfies all the conditions of equations (1) to (5).

[0079] Figure 10 shows the longitudinal aberrations in the optical system of numerical example 5. [Examples]

[0080] The optical system of Example 6 (Numerical Example 6) shown in Figure 11 has a total field of view of approximately 105°. The basic configuration of the optical system of Example 6 is the same as that of Example 4. However, compared to Example 4, the size of the display element has been increased, the first lens has been changed to a biconvex shape, and the third lens has been changed to a meniscus shape with the convex surface facing the display surface ID side.

[0081] The polarization utilization configuration and the optical path of the image light guided from the display surface ID to the pupil surface SP are the same as in Example 4.

[0082] The values ​​of equations (1) to (5) in numerical example 6 are summarized in Table 1. The observation optical system in numerical example 6 satisfies all the conditions of equations (1) to (5).

[0083] Figure 12 shows the longitudinal aberrations in the optical system of numerical example 6.

[0084] Examples 1 to 6 above employ polarization utilization configuration 1, but polarization utilization configuration 2 may also be used.

[0085] Numerical examples 1 to 6 are shown below. In each numerical example, the surface number i indicates the order of the surfaces when counted from the object side. r is the radius of curvature (mm) of the i-th surface from the object side, d is the lens thickness or air gap (mm) on the optical axis between the i-th and (i+1)-th surfaces, and nd is the refractive index of the optical material at the d-line between the i-th and (i+1)-th surfaces. νd is the Abbe number with respect to the d-line of the optical material between the i-th and (i+1)-th surfaces.

[0086] The Abbe number νd, with respect to the d line, is expressed as νd = (Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices of the Fraunhofer lines d (587.6 nm), F (486.1 nm), and C (656.3 nm), respectively.

[0087] The effective diameter is the diameter (in mm) of the region on the i-th lens surface through which the light rays contributing to image formation pass.

[0088] EPD indicates the pupil diameter (mm). BF indicates the back focus (mm). Back focus is the distance along the optical axis from the surface closest to the display surface ID (final surface) of the optical system to the display surface ID (referred to as the image plane in numerical examples), expressed in terms of air equivalent length. The total length of the lens is the distance along the optical axis from the surface closest to the pupil surface SP (frontmost surface) of the optical system to the final surface, plus the back focus.

[0089] The asterisk (*) next to the surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following formula, where X is the displacement from the surface vertex in the direction of the optical axis, H is the height from the optical axis in the direction perpendicular to the optical axis, the direction of light propagation is positive, r is the radius of paraxial curvature, K is the cone constant, and A4, A6, A8, A10 are aspherical coefficients.

[0090]

number

[0091] The cone constant and aspheric coefficient "e±x" are multiplied by 10. ±x It means...

[0092] (Numerical example 1) Unit: mm Surface data Face number rd nd νd Effective diameter 1 (pupil surface) ∞ (variable) 4.00 2* 94.986 0.20 1.48000 50.0 36.00 3* 94.986 5.50 1.49171 57.4 36.00 4* -71.282 0.10 1.58000 30.0 36.00 5* -71.282 1.80 1.58306 30.2 36.00 HM1 6 ∞ 0.10 1.58000 30.0 39.50 7 ∞ 8.00 1.54390 56.0 39.50 8* -39.963 -8.00 Reflective surface 41.60 HM2 9 ∞ -0.10 1.58000 30.0 39.50 10 ∞ -1.80 1.58306 30.2 39.50 11* -71.282 1.80 Reflective surface 36.00 HM1 12 ∞ 0.10 1.58000 30.0 39.50 13 ∞ 8.00 1.54390 56.0 39.50 14* -39.963 0.77 41.60 HM2 15 ∞ 0.10 1.58000 30.0 30.00 16 ∞ 0.10 1.48000 50.0 30.00 17 ∞ 0.70 1.51633 64.1 30.00 18 ∞ 0.00 30.00 Image plane ∞ Aspherical data 2nd side K = 0.00000e+00 A 4=-4.87128e-06 A 6= 1.72268e-08 A 8=-3.73426e-11 3rd page K = 0.00000e+00 A 4=-4.87128e-06 A 6= 1.72268e-08 A 8=-3.73426e-11 Side 4 K = 0.00000e+00 A 4= 8.50581e-07 A 6= 2.41342e-09 A 8= 2.07690e-12 5th page K = 0.00000e+00 A 4= 8.50581e-07 A 6= 2.41342e-09 A 8= 2.07690e-12 Side 8 K = 0.00000e+00 A 4=-2.89351e-07 A 6= 2.17156e-09 A 8=-3.28232e-12 A10 = 5.62384e-15 Page 11 K = 0.00000e+00 A 4= 8.50581e-07 A 6= 2.41342e-09 A 8= 2.07690e-12 Page 14 K = 0.00000e+00 A 4=-2.89351e-07 A 6= 2.17156e-09 A 8=-3.28232e-12 A10 = 5.62384e-15 Various data Focal length 17.07 EPD 4.00 Half viewing angle (°) 50.00 Lens length: 17.37 (in G) BF 1.37 (in Air) d 1 15.00 Single lens data Lens starting plane, focal length 1 3 83.73 2(Gn) 5 -122.25 3(Ga) 7 73.48 4(CG) 17 0.00 (Numerical example 2) Unit: mm Surface data Face number rd nd νd Effective diameter 1 (pupil surface) ∞ (variable) 7.39 2* 256.852 0.20 1.48000 50.0 39.00 3* 256.852 6.80 1.53500 56.0 39.00 4* -65.567 0.10 1.58000 30.0 39.00 5* -65.567 2.75 1.63500 23.9 39.00 HM1 6 -121.543 0.10 1.58000 30.0 43.00 7 -121.543 8.00 1.50000 53.0 43.00 8* -45.082 -8.00 Reflective surface 46.50 HM2 9 -121.543 -0.10 1.58000 30.0 43.00 10 -121.543 -2.75 1.63500 23.9 43.00 11* -65.567 2.75 Reflective surface 39.00 HM1 12 -121.543 0.10 1.58000 30.0 43.00 13 -121.543 8.00 1.50000 53.0 43.00 14* -45.082 3.53 46.50 HM2 15 ∞ 0.10 1.58000 30.0 40.00 16 ∞ 0.10 1.48000 50.0 40.00 17 ∞ 0.70 1.51633 64.1 40.00 18 ∞ 0.00 40.00 Image plane ∞ Aspherical data 2nd side K = 0.00000e+00 A 4=-1.22299e-06 A 6= 5.45602e-09 A 8=-1.09803e-11 3rd page K = 0.00000e+00 A 4=-1.22299e-06 A 6= 5.45602e-09 A 8=-1.09803e-11 Side 4 K = 0.00000e+00 A 4=-1.05644e-06 A 6= 4.29253e-09 A 8=-5.02523e-12 5th page K = 0.00000e+00 A 4=-1.05644e-06 A 6= 4.29253e-09 A 8=-5.02523e-12 Side 8 K = 0.00000e+00 A 4=-1.35968e-07 A 6=-4.86800e-11 A 8= 1.74545e-12 A10 = -2.00638e-15 Page 11 K = 0.00000e+00 A 4=-1.05644e-06 A 6= 4.29253e-09 A 8=-5.02523e-12 Page 14 K = 0.00000e+00 A 4=-1.35968e-07 A 6=-4.86800e-11 A 8= 1.74545e-12 A10 = -2.00638e-15 Various data Focal length 22.16 EPD 4.00 Half viewing angle (°) 47.50 Lens length: 22.38 (in G) BF 4.12 (in Air) d 1 15.00 Single lens data Lens starting plane, focal length 1 3 98.36 2(Gn) 5 -228.56 3(Ga) 7 138.50 4(CG) 17 0.00 (Numerical example 3) Unit: mm Surface data Face number rd nd νd Effective diameter 1 (pupil surface) ∞ (variable) 7.29 2* 384.803 7.50 1.64220 22.4 41.40 3* -61.478 0.10 1.48000 50.0 41.40 4* -61.478 0.10 1.58000 30.0 41.40 5* -61.478 1.80 1.64220 22.4 41.40 HM1 6 ∞ 0.10 1.58000 30.0 46.50 7 ∞ 9.85 1.54390 56.0 46.50 8* -43.478 -9.85 Reflective surface 49.20 HM2 9 ∞ -0.10 1.58000 30.0 46.50 10 ∞ -1.80 1.64220 22.4 46.50 11* -61.478 1.80 Reflective surface 41.40 HM1 12 ∞ 0.10 1.58000 30.0 46.50 13 ∞ 9.85 1.54390 56.0 46.50 14* -43.478 0.80 49.20 HM2 15 ∞ 0.10 1.58000 30.0 40.00 16 ∞ 0.10 1.48000 50.0 40.00 17 ∞ 0.70 1.51633 64.1 40.00 18 ∞ 0.00 40.00 Image plane ∞ Aspherical data 2nd side K = 0.00000e+00 A 4= 9.51944e-07 A 6= 3.19792e-09 A 8=-4.88232e-12 3rd page K = 0.00000e+00 A 4= 2.94638e-06 A 6=-8.41332e-10 A 8=-1.89185e-13 Side 4 K = 0.00000e+00 A 4= 2.94638e-06 A 6=-8.41332e-10 A 8=-1.89185e-13 5th page K = 0.00000e+00 A 4= 2.94638e-06 A 6=-8.41332e-10 A 8=-1.89185e-13 Side 8 K = 0.00000e+00 A 4= 3.12976e-07 A 6= 3.91888e-10 A 8= 4.45492e-13 A10 = 2.13999e-16 Page 11 K = 0.00000e+00 A 4= 2.94638e-06 A 6=-8.41332e-10 A 8=-1.89185e-13 Page 14 K = 0.00000e+00 A 4= 3.12976e-07 A 6= 3.91888e-10 A 8= 4.45492e-13 A10 = 2.13999e-16 Various data Focal length 20.56 EPD 4.00 Half viewing angle (°) 55.00 Lens length: 21.15 inches (in G) BF 1.39 (in Air) d 1 12.00 Single lens data Lens starting plane, focal length 1 1 83.09 2(Gn) 5 -95.73 3(Ga) 7 79.94 4(CG) 17 0.00 (Numerical example 4) Unit: mm Surface data Face number rd nd νd Effective diameter 1 (pupil surface) ∞ (variable) 7.08 2 ∞ 0.20 1.48000 50.0 37.00 3 ∞ 6.50 1.54390 56.0 37.00 4* -28.195 0.10 1.58000 30.0 37.00 5* -28.195 0.10 1.58000 30.0 37.00 HM1 6* -28.195 7.48 1.54390 56.0 37.00 7* -28.195 -7.48 Reflective surface 41.00 HM2 8* -28.195 -0.10 1.58000 30.0 37.00 9* -28.195 0.10 Reflective surface 37.00 HM1 10* -28.195 7.48 1.54390 56.0 37.00 11* -28.195 2.22 1.64220 22.4 41.00 HM2 12* 270.534 0.80 29.80 13 ∞ 0.10 1.58000 30.0 30.00 14 ∞ 0.10 1.48000 50.0 30.00 15 ∞ 0.70 1.51633 64.1 30.00 16 ∞ 0.00 30.00 Image plane ∞ Aspherical data Side 4 K = 0.00000e+00 A 4= 3.18176e-05 A 6=-2.54232e-08 A 8= 1.73818e-11 5th page K = 0.00000e+00 A 4= 3.18176e-05 A 6=-2.54232e-08 A 8= 1.73818e-11 Side 6 K = 0.00000e+00 A 4= 3.18176e-05 A 6=-2.54232e-08 A 8= 1.73818e-11 Side 7 K = 0.00000e+00 A 4= 2.78325e-06 A 6= 4.17527e-09 A 8= 3.96250e-13 A10 = 1.29453e-14 Side 8 K = 0.00000e+00 A 4= 3.18176e-05 A 6=-2.54232e-08 A 8= 1.73818e-11 9th page K = 0.00000e+00 A 4= 3.18176e-05 A 6=-2.54232e-08 A 8= 1.73818e-11 Side 10 K = 0.00000e+00 A 4= 3.18176e-05 A 6=-2.54232e-08 A 8= 1.73818e-11 Page 11 K = 0.00000e+00 A 4= 2.78325e-06 A 6= 4.17527e-09 A 8= 3.96250e-13 A10 = 1.29453e-14 Side 12 K = 0.00000e+00 A 4=-1.33350e-04 A 6= 8.94427e-07 A 8=-3.14443e-09 A10 = 4.25092e-12 Various data Focal length 17.22 EPD 4.00 Half viewing angle (°) 47.50 Lens length: 18.30 (in G) BF 1.40 (in Air) d 1 15.00 Single lens data Lens starting plane, focal length 1 3 51.84 2(Ga) 6 554.37 3(Gn) 11 -39.65 4(CG) 15 0.00 (Numerical example 5) Unit: mm Surface data Face number rd nd νd Effective diameter 1 (pupil surface) ∞ (variable) 7.05 2 248.102 7.20 1.54390 56.0 34.80 3* -29.288 0.10 1.48000 50.0 34.80 4* -29.288 0.10 1.58000 30.0 34.80 5* -29.288 0.10 1.58000 30.0 34.80 HM1 6* -29.288 6.90 1.54390 56.0 34.80 7* -27.824 -6.90 Reflective surface 38.50 HM2 8* -29.288 -0.10 1.58000 30.0 34.80 9* -29.288 0.10 Reflective surface 34.80 HM1 10* -29.288 6.90 1.54390 56.0 34.80 11* -27.824 2.50 1.58306 30.2 38.50 HM2 12* 58.424 0.99 27.00 13 ∞ 0.10 1.58000 30.0 30.00 14 ∞ 0.10 1.48000 50.0 30.00 15 ∞ 0.70 1.51633 64.1 30.00 16 ∞ 0.00 30.00 Image plane ∞ Aspherical data 3rd page K = 0.00000e+00 A 4= 2.73479e-05 A 6=-1.30936e-08 A 8= 3.65649e-12 Side 4 K = 0.00000e+00 A 4= 2.73479e-05 A 6=-1.30936e-08 A 8= 3.65649e-12 5th page K = 0.00000e+00 A 4= 2.73479e-05 A 6=-1.30936e-08 A 8= 3.65649e-12 Side 6 K = 0.00000e+00 A 4= 2.73479e-05 A 6=-1.30936e-08 A 8= 3.65649e-12 Side 7 K = 0.00000e+00 A 4= 3.02459e-06 A 6= 4.30603e-09 A 8= 2.51882e-12 A10 = 1.52296e-14 Side 8 K = 0.00000e+00 A 4= 2.73479e-05 A 6=-1.30936e-08 A 8= 3.65649e-12 9th page K = 0.00000e+00 A 4= 2.73479e-05 A 6=-1.30936e-08 A 8= 3.65649e-12 Side 10 K = 0.00000e+00 A 4= 2.73479e-05 A 6=-1.30936e-08 A 8= 3.65649e-12 Page 11 K = 0.00000e+00 A 4= 3.02459e-06 A 6= 4.30603e-09 A 8= 2.51882e-12 A10 = 1.52296e-14 Side 12 K = 0.00000e+00 A 4=-3.09815e-04 A 6= 2.95945e-06 A 8=-1.35266e-08 A10 = 2.30855e-11 Various data Focal length 16.87 EPD 4.00 Half viewing angle (°) 50.00 Lens length: 18.79 inches (in G) BF 1.58 (in Air) d 1 12.00 Single lens data Lens starting plane, focal length 1 1 48.61 2(Ga) 6 384.65 3(Gn) 11 -31.98 4(CG) 15 0.00 (Numerical example 6) Unit: mm Surface data Face number rd nd νd Effective diameter 1 (pupil surface) ∞ (variable) 7.36 2 872.526 0.20 1.48000 50.0 44.00 3 872.526 7.50 1.54390 56.0 44.00 4* -37.862 0.10 1.58000 30.0 44.00 5* -37.862 0.10 1.58000 30.0 44.00 HM1 6* -37.862 7.60 1.49171 57.4 44.00 7* -34.077 -7.60 Reflective surface 48.00 HM2 8* -37.862 -0.10 1.58000 30.0 44.00 9* -37.862 0.10 Reflective surface 44.00 HM1 10* -37.862 7.60 1.49171 57.4 44.00 11* -34.077 2.80 1.66100 20.4 48.00 HM2 12* -196.909 3.72 39.00 13 ∞ 0.10 1.58000 30.0 40.00 14 ∞ 0.10 1.48000 50.0 40.00 15 ∞ 0.70 1.51633 64.1 40.00 16 ∞ 0.00 40.00 Image plane ∞ Aspherical data Side 4 K = 0.00000e+00 A 4= 7.78987e-06 5th page K = 0.00000e+00 A 4= 7.78987e-06 Side 6 K = 0.00000e+00 A 4= 7.78987e-06 Side 7 K = 0.00000e+00 A 4= 8.59302e-07 A 6= 1.79369e-09 A 8=-1.62389e-12 A10 = 3.74479e-15 Side 8 K = 0.00000e+00 A 4= 7.78987e-06 9th page K = 0.00000e+00 A 4= 7.78987e-06 Side 10 K = 0.00000e+00 A 4= 7.78987e-06 Page 11 K = 0.00000e+00 A 4= 8.59302e-07 A 6= 1.79369e-09 A 8=-1.62389e-12 A10 = 3.74479e-15 Side 12 K = 0.00000e+00 A 4=-2.34199e-05 A 6= 4.84486e-08 A 8=-6.30264e-11 A10 = 3.54562e-14 Various data Focal length 21.81 EPD 4.00 Half viewing angle (°) 52.50 Lens length: 22.92 (in G) BF 4.32 (in Air) d 1 15.00 Single lens data Lens starting plane, focal length 1 3 66.91 2(Ga) 6 417.12 3(Gn) 11 -62.77 4(CG) 15 0.00

[0093] [Table 1]

[0094] [Display device] Figure 15 shows a head-mounted display (HMD) as an image display device using the observation optical systems of Examples 1 to 6. The HMD is mounted on the observer's head (in front of the eyes) by mounting gear (not shown).

[0095] The HMD includes image display elements RID and LID for the right and left eyes, a right-eye observation optical system ROS that directs the display light from the right-eye image display element RID to the observer's right eye, and a left-eye observation optical system LOS that directs the display light from the left-eye image display element LID to the observer's left eye.

[0096] By using the observation optical systems shown in Examples 1 to 6 as the right-eye and left-eye observation optical systems ROS and LOS, it is possible to realize a compact HMD capable of observing high-quality images with a wide field of view.

[0097] The above embodiments include the following configuration.

[0098] (Composition 1) An optical system that guides image light from a display element to the observation side. A cemented lens formed by joining at least three lenses, including a negative lens, Each has a first transmissive reflective surface and a second transmissive reflective surface, both having a concave shape on the observation side in the paraxial direction. At least one of the first and second transmission and reflection surfaces is located on the bonding surface of the bonding lens, The image light is guided to the observation side through transmission by the second transmission-reflecting surface, reflection by the first transmission-reflecting surface, reflection by the second transmission-reflecting surface, and transmission by the first transmission-reflecting surface. When the Abbe number with respect to the d line of the negative lens is νdGn, the focal length of the negative lens in refraction in air is fGn, the focal length of the optical system is f, the paraxial radius of curvature of the first transmission / reflecting surface is R_HM1, and the paraxial radius of curvature of the second transmission / reflecting surface is R_HM2, 10.0 ≤ νdGn ≤ 50.0 -10.0 ≤ fGn / f ≤ -1.0 0.0 <R_HM2 / R_HM1≦1.0 An optical system characterized by satisfying the following conditions. (Configuration 2) The optical system according to configuration 1, characterized in that the negative lens is disposed between the first transmission reflective surface and the second transmission reflective surface. (Composition 3) The optical system according to configuration 2, characterized in that the negative lens has a plano-concave shape. (Composition 4) The optical system according to any one of configurations 1 to 3, characterized in that the negative lens is positioned on the display element side of the second transmission / reflection surface. (Composition 5) The optical system according to any one of configurations 1 to 4, characterized in that the first transmission-reflection surface is arranged on the bonding surface. (Composition 6) An intermediate lens is positioned between the first transmissive reflective surface and the second transmissive reflective surface. When the Abbe number with respect to the d line of the intermediate lens is denoted by νdGa, 40.0 ≤ νdGa ≤ 90.0 An optical system according to any one of configurations 1 to 5, characterized by satisfying the following conditions. (Composition 7) An intermediate lens is positioned between the first transmissive reflective surface and the second transmissive reflective surface. When the focal length of the intermediate lens in refraction in air is fGa, 1.0 ≤ fGa / f ≤ 100.0 An optical system according to any one of configurations 1 to 6, characterized by satisfying the following conditions. (Composition 8) The optical system according to any one of configurations 1 to 7, characterized in that one of the first transmission-reflective surface and the second transmission-reflective surface is composed of a polarization-selective transmission-reflective element. (Composition 9) An optical system that guides image light from a display element to the observation side. A cemented lens formed by joining at least three lenses, including a negative lens, Each has a first transmissive reflective surface and a second transmissive reflective surface, both having a concave shape on the observation side in the paraxial direction. At least one of the first and second transmission and reflection surfaces is located on the bonding surface of the bonding lens, An optical system characterized by guiding the image light to the observation side through transmission by the second transmission-reflecting surface, reflection by the first transmission-reflecting surface, reflection by the second transmission-reflecting surface, and transmission by the first transmission-reflecting surface. (Composition 10) The optical system described in any one of configurations 1 to 9, A display device characterized by having the aforementioned display element.

[0099] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of Symbols]

[0100] SP pupil plane ID display surface HM1 First Transmitting Reflective Surface HM2 Second Transmittent Reflective Surface Gn negative lens Ga lens

Claims

1. An optical system that guides image light from a display element to the observation side, A cemented lens formed by joining at least three lenses, including a negative lens, Each has a first transmissive reflective surface and a second transmissive reflective surface, both having a concave shape on the observation side in the paraxial direction. At least one of the first and second transmission and reflection surfaces is located on the bonding surface of the bonding lens, The image light is guided to the observation side after being transmitted through the second transmission reflective surface, reflected by the first transmission reflective surface, reflected again by the second transmission reflective surface, and transmitted through the first transmission reflective surface. When the Abbe number with respect to the d line of the negative lens is νdGn, the focal length of the negative lens in refraction in air is fGn, the focal length of the optical system is f, the paraxial radius of curvature of the first transmission / reflecting surface is R_HM1, and the paraxial radius of curvature of the second transmission / reflecting surface is R_HM2, 10.0 ≤ νdGn ≤ 50.0 -10.0 ≤ fGn / f ≤ -1.0 0.0<R_HM2 / R_HM1≦1.0 An optical system characterized by satisfying the following conditions.

2. The optical system according to claim 1, characterized in that the negative lens is disposed between the first transmission reflective surface and the second transmission reflective surface.

3. The optical system according to claim 2, characterized in that the negative lens has a plano-concave shape.

4. The optical system according to claim 1, characterized in that the negative lens is positioned on the display element side of the second transmission / reflection surface.

5. The optical system according to claim 1, characterized in that the first transmission / reflection surface is arranged on the bonding surface.

6. An intermediate lens is positioned between the first transmissive reflective surface and the second transmissive reflective surface. When the Abbe number with respect to the d line of the intermediate lens is denoted as νdGa, 40.0 ≤ νdGa ≤ 90.0 The optical system according to claim 1, characterized in that it satisfies the following conditions.

7. An intermediate lens is positioned between the first transmissive reflective surface and the second transmissive reflective surface. When the focal length of the intermediate lens in refraction in air is fGa, 1.0 ≤ fGa / f ≤ 100.0 The optical system according to claim 1, characterized in that it satisfies the following conditions.

8. The optical system according to claim 1, characterized in that one of the first transmission-reflective surface and the second transmission-reflective surface is composed of a polarization-selective transmission-reflective element.

9. An optical system that guides image light from a display element to the observation side. A cemented lens formed by joining at least three lenses, including a negative lens, Each has a first transmissive reflective surface and a second transmissive reflective surface, both having a concave shape on the observation side in the paraxial direction. At least one of the first and second transmission and reflection surfaces is located on the bonding surface of the bonding lens, An optical system characterized by guiding the aforementioned image light to the observation side through transmission by the second transmission-reflecting surface, reflection by the first transmission-reflecting surface, reflection by the second transmission-reflecting surface, and transmission by the first transmission-reflecting surface.

10. An optical system according to any one of claims 1 to 9, A display device characterized by having the aforementioned display element.

Images