Optical systems and display devices

Abstract

This provides a more compact optical system while incorporating a transmission and reflection surface. [Solution] The optical system 100 guides illumination light to a modulation surface and projects modulated light from the modulation surface. The optical system has a transmission-reflection surface P that directs illumination light toward the modulation surface and modulated light toward the projection side, a first positive lens 104 positioned on the modulation surface side of the transmission-reflection surface, and a second positive lens 105 adjacent to the first positive lens on the modulation surface side. When L is the distance on the optical axis between the projection surface in the optical system and the modulation surface, and H is the diagonal length of the effective area of ​​the modulation surface, the condition 0.1 ≤ L / H ≤ 5.0 is satisfied.

Description

Technical Field

[0001] The present invention relates to an optical system used in display devices such as smart glasses and AR (Augmented Reality) glasses.

Background Art

[0002] As an optical system that guides light from a light modulation element such as a reflective liquid crystal element (LCOS) or a digital micromirror device (DMD) to a light guide plate disposed in front of an observer's eyes, there is one that incorporates a transmission-reflection surface such as a polarization separation surface.

Summary of the Invention

Problems to be Solved by the Invention

[0003] A smaller optical system is desired while incorporating a transmission-reflection surface.

Means for Solving the Problems

[0004] The optical system according to one aspect of the present invention guides illumination light to a modulation surface and projects modulated light from the modulation surface. The optical system includes a transmission-reflection surface that directs the illumination light toward the modulation surface side and the modulated light toward the projection side, a first positive lens disposed on the modulation surface side of the transmission-reflection surface, and a second positive lens adjacent to the first positive lens on the modulation surface side. When the distance on the optical axis between the most projection-side surface in the optical system and the modulation surface is L and the diagonal length of the effective area of the modulation surface is H, 0.1 ≦ L / H ≦ 5.0 It is characterized by satisfying the above conditions. Note that a display device having the above optical system also constitutes another aspect of the present invention.

Brief Description of the Drawings

[0005] [Figure 1] Cross-sectional view of the optical system of Example 1. [Figure 2] Aberration diagram of the optical system of Example 1. [Figure 3] Cross-sectional view of the optical system of Example 2. [Figure 4] Aberration diagram of the optical system of Example 2. [Figure 5] Cross-sectional view of the optical system of Example 3. [Figure 6] Aberration diagram of the optical system in Example 3. [Figure 7] Cross-sectional view of the optical system of Example 4. [Figure 8] Aberration diagram of the optical system in Example 4. [Figure 9] A diagram showing a polarization conversion element (PBS). [Figure 10] Schematic diagrams of display devices equipped with the optical systems of Examples 1 to 4. [Modes for carrying out the invention]

[0006] The embodiments of the present invention will now be described with reference to the drawings. Figures 1, 3, 5, and 7 show vertical cross-sections of the optical systems of Embodiments 1 to 4 when in focus on an object at infinity.

[0007] Before describing specific examples 1 to 4, let's first explain the common points across all examples. In each example, the optical system projects modulated light (display light) from a reflective optical modulation element such as LCOS (Liquid Crystal On Silicon) or DMD (Digital Micromirror Device) onto the incident portion of a light guide plate in a glasses-type display device such as smart glasses or AR glasses. The image light propagates through the light guide plate while undergoing total internal reflection, and the image is displayed when it enters the observer's eye from the exit portion of the light guide plate. Note that the optical systems in each example are not limited to the glasses-type display devices described above, but can also be used in projector-type display devices that project image light onto a projection surface such as a screen or wall.

[0008] Therefore, the optical system of each embodiment has a transmission-reflecting surface that directs illumination light toward the modulation surface side (e.g., reflects it) and directs modulated light toward the projection side (e.g., transmits it). As the transmission-reflecting surface, a polarization-separating surface P that transmits or reflects incident light according to its polarization direction can be used. The polarization-separating surface P is provided in a polarization beam splitter (PBS) as a polarization-selective transmission-reflecting element. The polarization-selective transmission-reflecting element is a wire grid polarizer or a phase difference film stacked polarizer. The wire grid formation surface or the phase difference film surface functions as a polarization-separating surface. The wire grid polarizer does not necessarily have to be made of aligned metal wires; it is sufficient if it has thin metal or dielectric layers at predetermined intervals and functions as a polarization-selective transmission-reflecting element. For example, an element in which layers of metal or dielectric are aligned by vapor deposition, printing, or lithography can be used. As the polarization-selective transmission-reflecting element, for example, the product name "WGF" from Asahi Kasei Corporation or the product name "IQPE" from 3M Company can be used.

[0009] Figure 9 shows the configuration of the PBS. The modulation plane IM has an effective area with horizontal size a and vertical size b. The diagonal length of the effective area is H. The size of the PBS can be minimized by irradiating this effective area with illumination light from a rectangular cross-section with a horizontal size:vertical size ratio a:b ≈ a1:b1.

[0010] In Figures 1, 3, 5, and 7, a PBS with vertical size b1 is shown as PBS1. As shown in Figure 9, the angle θP between the optical axis e and the polarization separation plane P in the vertical cross-section is 45°. Also in Figures 1, 3, 5, and 7, the area through which light emitted from the diagonal end of the modulation plane IM passes through PBS is shown as PBS2 by a dashed line.

[0011] In addition, the optical system of each embodiment includes a first positive lens (104, 204, 303, 404) disposed on the modulation surface side with respect to the transmission reflection surface (polarization separation surface P), and a second positive lens (105, 205, 304, 405) adjacent to the first positive lens on the modulation surface side. By providing the lens having a positive refractive power by dividing it into the first and second positive lenses, it is possible to achieve both ease of manufacturing the lens having a positive refractive power and good optical performance as described later.

[0012] In the optical system of each embodiment, it is preferable that the distance L on the optical axis between the most projection-side surface in the optical system and the modulation surface IM and the diagonal length H of the effective area of the modulation surface IM satisfy the condition of the following formula (1). Note that the most projection-side surface may be any of the projection-side surface of the PBS, the lens surface, and the aperture stop SP.

[0013] 0.1 ≦ L / H ≦ 5.0 (1) The condition of formula (1) shows an appropriate relationship between the overall length of the optical system and the size of the modulation surface. If L / H exceeds the upper limit of formula (1), the modulation surface is too small, which causes restrictions on the actually usable reflective optical modulation element or the optical system becomes large, so it is not preferable. Also, since the focal length of the optical system becomes too long and a desired viewing angle cannot be obtained, it is not preferable. If L / H is below the lower limit of formula (1), it is advantageous for miniaturization of the optical system, but it becomes difficult to arrange the lenses or the focal length of the optical system for the display device becomes too short, so it is not preferable.

[0014] Note that it is more preferable that the lower limit of formula (1) is 0.5, 1.0, or 1.4. Also, it is more preferable that the upper limit of formula (1) is 4.0, 3.0, or 2.5.

[0015] By satisfying the above configuration and the condition of formula (1), it is possible to realize a small optical system while incorporating a transmission reflection surface.

[0016] In the optical system of each embodiment, a quarter-wave plate (not shown) is disposed between the lens closest to the modulation surface (the second positive lens) and the modulation surface IM. The linearly polarized light (S-polarized light) reflected by the polarization separation surface P passes through the quarter-wave plate and is converted into circularly polarized light. The circularly polarized light is reflected by the modulation surface IM and becomes counterclockwise circularly polarized light. This counterclockwise circularly polarized light passes through the quarter-wave plate again and is converted into linearly polarized light (P-polarized light). The P-polarized light enters the lens closest to the modulation surface, passes through the polarization separation surface P, and exits to the projection side. A polarization cancellation element may be disposed instead of the quarter-wave plate. As the polarization cancellation element, for example, "Cosmo Shine SRF" of Toyobo Co., Ltd. can be used.

[0017] In addition to the condition of the formula (1), the optical system of each embodiment preferably satisfies at least one of the conditions of the following formulas (2) to (13).

[0018] 0.1 ≦ La / H ≦ 2.0 (2) 0.0 ≦ d / D ≦ 0.3 (3) 0.5 ≦ |rr2| / f ≦ 100.0 (4) 1.5 ≦ |rr2| / de ≦ 300.0 (5) 0.2 ≦ ffa / ffb ≦ 2.3 (6) 0.0 < Sd / L ≦ 0.5 (7) Nd1 ≦ 1.6 (8) Nd2 ≦ 1.6 (9) α1 ≧ 1.0×10 -6 (10) α2 ≧ 1.0×10 -6 (11) 40° ≦ θP ≦ 50° (12) 0.1 ≦ Sk / f ≦ 0.3 (13) In equations (2) to (13), La is the optical axis distance between the projection-side lens surface of the first positive lens and the modulation surface IM. d is the optical axis distance between the modulation-side lens surface of the first positive lens and the projection-side lens surface of the second positive lens, and D is the optical axis distance between the projection-side lens surface of the first positive lens and the modulation-side lens surface of the second positive lens. f is the focal length of the entire optical system, and rr2 is the paraxial radius of curvature of the modulation-side lens surface of the second positive lens. de is the optical axis thickness of the second positive lens (the optical axis distance between the modulation-side lens surface and the projection-side lens surface). ffa is the focal length of the first positive lens, and ffb is the focal length of the second positive lens. Sd is the optical axis distance between the aperture diaphragm SP and the projection-side lens surface of the first positive lens. Nd1 is the refractive index of the first positive lens at the d line, and Nd2 is the refractive index of the second positive lens at the d line. Furthermore, α1 is the coefficient of thermal expansion of the first positive lens, and α2 is the coefficient of thermal expansion of the second positive lens. θP is the angle less than 90° that the transmitted and reflected surface, as a plane, makes with respect to the optical axis. In addition, Sk is the air-equivalent distance on the optical axis between the lens surface on the modulation surface side of the optical system and the modulation surface IM.

[0019] The conditions in equation (2) indicate an appropriate relationship between the distance between the projection-side lens surface of the first positive lens and the modulation surface IM, and the diagonal length of the modulation surface IM. If La / H exceeds the upper limit of equation (2), it is undesirable because the modulation surface becomes too small, limiting the types of reflective optical modulators that can actually be used and leading to a larger optical system. If La / H falls below the lower limit of equation (2), it is advantageous for miniaturizing the optical system, but it is undesirable because it makes lens arrangement difficult.

[0020] Furthermore, it is more preferable to set the lower limit of equation (2) to 0.3, 0.5, or 0.7. Also, it is more preferable to set the upper limit of equation (2) to 1.5, 1.2, or 1.0.

[0021] The condition in equation (3) indicates an appropriate relationship between the distance between the first positive lens and the second positive lens and the distance from the projection-side lens surface of the first positive lens to the modulation-side lens surface of the second positive lens. In other words, it indicates that the first positive lens and the second positive lens are positioned touching or in close proximity to each other. If d / D exceeds the upper limit of equation (3), the first positive lens and the second positive lens are too far apart, resulting in a larger optical system, which is undesirable.

[0022] Furthermore, it is more preferable to set the upper limit of equation (3) to 0.2, 0.1, or 0.05.

[0023] The conditions in equation (4) indicate an appropriate relationship between the paraxial radius of curvature of the lens surface on the modulation side of the second positive lens and the focal length of the entire optical system. If |rr2| / f falls below the lower limit of equation (4), the curvature of the lens surface on the modulation side of the second positive lens becomes too gentle. As a result, the optical system is no longer telecentric and the front-facing condition of the modulation surface cannot be satisfied, which is undesirable. On the other hand, if |rr2| / f exceeds the upper limit of equation (4), the curvature becomes too steep, which is advantageous for making the optical system telecentric, but it is undesirable because it makes it difficult to correct the field curvature.

[0024] Furthermore, it is more preferable to set the lower limit of equation (4) to 0.8 or 1.0. Also, it is more preferable to set the upper limit of equation (4) to 80.0, 50.0, 10.0, 5.0, or 3.0.

[0025] The condition in equation (5) indicates an appropriate relationship between the paraxial radius of curvature of the lens surface on the modulation surface side of the second positive lens and the thickness of the second positive lens. If |rr2| / de falls below the lower limit of equation (5), the curvature of the lens surface on the modulation surface side of the second positive lens becomes too gentle, causing the angle of incidence of the principal ray to deviate significantly from 0° relative to the modulation surface, thus failing to satisfy the frontal view requirement for the modulation surface, which is undesirable. On the other hand, if |rr2| / f exceeds the upper limit of equation (5), the curvature becomes too steep, which is advantageous for making the optical system telecentric, but makes it difficult to correct the field curvature, which is undesirable.

[0026] Furthermore, it is more preferable to set the lower limit of equation (5) to 2.0 or 3.0. Also, it is more preferable to set the upper limit of equation (5) to 250.0, 150.0, 50.0, 10.0, or 5.0.

[0027] The condition in equation (6) indicates an appropriate relationship between the focal length of the first positive lens and the focal length of the second positive lens. In other words, it indicates that the refractive powers of the first and second positive lenses are approximately the same. If ffa / ffb does not satisfy the condition in equation (6), the imaging performance deteriorates and the deviation of the optical system from telecentricity increases, which is undesirable.

[0028] Furthermore, it is more preferable to set the lower limit of equation (6) to 0.3, 0.5, or 0.8. Also, it is more preferable to set the upper limit of equation (6) to 2.0, 1.5, or 1.0.

[0029] The conditions in equation (7) indicate an appropriate relationship between the total length of the optical system and the distance from the aperture diaphragm SP to the projection-side lens surface of the first positive lens. If Sd / L falls below the lower limit of equation (7), the pupil plane will be located within the optical system, which is undesirable because it will cause interference between the optical system and the light guide plate when the modulated light projected from the optical system is incident on a light guide plate such as AR glasses. On the other hand, if Sd / L exceeds the upper limit of equation (7), the outer diameter of the first positive lens will become too large, resulting in an undesirable optical system.

[0030] Furthermore, it is more preferable to set the lower limit of equation (7) to 0.005 or 0.008. Also, it is more preferable to set the upper limit of equation (7) to 0.4 or 0.3.

[0031] The condition in equation (8) indicates an appropriate range for the refractive index of the first positive lens, and shows that the first positive lens is a plastic lens.

[0032] The condition in equation (9) indicates an appropriate range for the refractive index of the second positive lens, and shows that the second positive lens is a plastic lens.

[0033] The condition in equation (10) indicates an appropriate range for the coefficient of linear expansion of the first positive lens, and shows that the first positive lens is a plastic lens.

[0034] The conditions in equation (11) indicate an appropriate range for the coefficient of thermal expansion of the second positive lens, and demonstrate that the second positive lens is a plastic lens.

[0035] The conditions in equation (12) indicate an appropriate range of angles that the transmission / reflection surface makes with respect to the optical axis. Ideally, θP is 45°. When illumination light is incident on the transmission / reflection surface from a direction perpendicular to the optical axis, the required characteristics can be obtained on the modulation surface side if θP is 45°. If θP falls outside the range of equation (12), the illumination light from the transmission / reflection surface will not reach the modulation surface IM, which is undesirable.

[0036] Furthermore, it is more preferable to set the lower limit of equation (12) to 42°, 43°, or 44°. Also, it is more preferable to set the upper limit of equation (7) to 48°, 47°, or 46°.

[0037] The conditions in equation (13) indicate an appropriate relationship between the distance between the lens surface closest to the modulation plane and the modulation plane IM, and the focal length of the entire optical system. If Sk / f falls below the lower limit of equation (13), it becomes difficult to place a quarter-wave plate between the modulation plane IM and the lens surface closest to the modulation plane, which is undesirable. If Sk / f exceeds the upper limit of equation (13), a quarter-wave plate can be placed, but the optical system becomes larger, which is undesirable.

[0038] Furthermore, it is more preferable to set the lower limit of equation (13) to 0.15 or 0.2. Also, it is more preferable to set the upper limit of equation (13) to 0.29 or 0.27.

[0039] The optical system requires a nearly telecentric configuration to utilize the reflection of illumination light from the light source panel. Furthermore, for use with AR glasses, a light guide plate must be placed on the projection side, and the aperture must be positioned closest to the projection side to direct the projected image. These structures constitute the configuration requirements for the projection optical system.

[0040] If the optical system is telecentric, the effective diameter of the lens positioned closest to the modulation plane is equal to the size of the effective area of ​​the modulation plane IM. Modulated light emitted from the modulation plane IM travels toward the projection plane (e.g., aperture diaphragm SP). Therefore, if the optical system is miniaturized in the direction in which the optical axis extends (optical axis direction), it is necessary to bend the light rays with a strong refractive power from the lens closest to the modulation plane to reach the projection plane, and the lens closest to the modulation plane must have a very strong positive refractive power. However, bending light rays with a strong refractive power causes significant chromatic aberration and field curvature. Therefore, it is necessary to correct these aberrations by appropriately setting the shape, refractive power, and Abbe number of the lens closer to the projection plane than the lens closest to the modulation plane.

[0041] Furthermore, increasing the refractive power of a lens generally increases the curvature of the lens surface and thus the lens thickness. In a telecentric optical system, the lens closest to the modulation plane is large due to its large diameter and high refractive index. To make the lens closest to the modulation plane thinner, it is necessary to reduce the curvature by using a high refractive index material. Also, to make the optical system telecentric, the lens surface on the modulation plane side of the lens closest to the modulation plane will have a convex shape with a sharp curvature on the modulation plane side unless a high refractive index material is used for the lens, but the curvature can be reduced by using a high refractive index material. In addition, to correct aberrations caused by strong refraction, it is preferable that at least one lens surface of the lens closest to the modulation plane be an aspherical lens.

[0042] On the other hand, to reduce the weight of the optical system, it is necessary to use plastic lenses. However, plastic materials are limited to those with relatively low refractive indices. Therefore, if, for example, the lens on the modulation side is made of plastic, the thickness along the optical axis becomes large, making processing difficult and degrading optical performance. For this reason, as mentioned above, by dividing the lens with positive refractive power into two, both ease of manufacturing and good optical performance are achieved.

[0043] Furthermore, as shown in the optical systems of Figures 5 and 7, it is preferable to arrange positive lenses (301, 401) and negative lenses (302, 402) in order from the aperture diaphragm side to the transmission / reflection surface side. Since light rays converge near the aperture diaphragm SP, both the on-axial and off-axial light beams pass through almost the same region, and by arranging positive and negative lenses, the aberration correction effect can be enhanced.

[0044] Furthermore, in order to achieve good aberration correction and miniaturization and thinning, it is necessary to use a high refractive index glass material for the positive lens. When using a high refractive index glass material, it is necessary to use a material on the high dispersion side within the range of existing glass maps. In this case, chromatic aberration will occur significantly, and spherical aberration and coma aberration will also occur due to the strong refractive power of the positive lens. To correct the aberrations that occur with a high refractive index, high dispersion positive lens, it is necessary to use a material with even higher dispersion than the positive lens material for the negative lens. By using such glass materials, chromatic aberration can be corrected, and spherical aberration and coma aberration can be well corrected by optimizing the power arrangement of the positive and negative lenses. In addition, it is preferable that the projection-side lens surface of the positive lens be convex toward the projection side. This shortens the length of the optical system along the optical axis, allowing for miniaturization of the optical system.

[0045] Furthermore, by constructing the optical system with five or fewer lenses in total, even higher optical performance can be achieved. Note that a cemented lens, which is formed by joining two lenses together, is counted as two lenses.

[0046] Furthermore, by positioning the transmission-reflecting surface closer to the projection side than the lens closest to the modulation plane, the optical system can be miniaturized. As mentioned above, the lens closest to the modulation plane refracts light from the modulation plane with strong refractive power in order to make the optical system telecentric and miniaturized. Therefore, by positioning the transmission-reflecting surface closer to the projection side, the optical system can be miniaturized. In particular, by positioning the transmission-reflecting surface (PBS) between the first positive lens and the aperture diaphragm SP, the size of the PBS can be minimized.

[0047] The optical systems of Examples 1 to 4 will be described in detail below. After Example 4, numerical examples 1 to 4 corresponding to each of Examples 1 to 4 are shown. [Examples]

[0048] The optical system 100 of Embodiment 1 (Numerical Example 1) shown in Figure 1 consists of an aperture diaphragm SP, a polarization separation surface P (PBS1), a cemented lens formed by joining a positive lens 101 and a negative lens 102, a negative lens 103, a first positive lens 104, and a second positive lens 105, arranged in order from the projection side to the modulation surface side. The negative lens 103, the first positive lens 104, and the second positive lens 105 are plastic lenses.

[0049] Figure 2 shows the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical system 100 in numerical example 1 when focused on an object at infinity. In the spherical aberration diagram, Fno indicates the F number, d indicates the spherical aberration at the d line (wavelength 587.6 nm), and g indicates the spherical aberration at the g line (wavelength 435.8 nm). In the astigmatism diagram, S indicates astigmatism at the sagittal image plane, and M indicates astigmatism at the meridional image plane. The distortion diagram shows the distortion at the d line. The chromatic aberration diagram shows the lateral chromatic aberration at the g line. ω is the half-angle of view (°). The explanation of these aberration diagrams is the same for numerical examples 2 to 4 described later. [Examples]

[0050] The optical system 200 of Example 2 (Numerical Example 2) shown in Figure 3 consists of an aperture diaphragm SP, a polarization separation surface P (PBS1), a cemented lens formed by joining a positive lens 201 and a negative lens 202, a negative lens 203, a first positive lens 204, and a second positive lens 205, arranged in order from the projection side to the modulation surface side. The negative lens 203, the first positive lens 204, and the second positive lens 205 are plastic lenses.

[0051] Figure 4 shows the longitudinal aberration of the optical system 200 in numerical example 2 when it is in focus on an object at infinity. [Examples]

[0052] The optical system 300 of Embodiment 3 (Numerical Example 3) shown in Figure 5 consists of an aperture diaphragm SP, a positive lens 301, a negative lens 302, a polarization separation surface P (PBS1), a first positive lens 303, and a second positive lens 304, arranged in order from the projection side to the modulation surface side. The first positive lens 303 and the second positive lens 304 are plastic lenses.

[0053] Figure 6 shows the longitudinal aberration of the optical system 300 in numerical example 3 when it is in focus on an object at infinity. [Examples]

[0054] The optical system 400 of Embodiment 4 (Numerical Example 4) shown in Figure 7 consists of an aperture diaphragm SP, a bonded lens formed by joining a positive lens 401 and a negative lens 402, a polarization separation surface P (PBS1), a negative lens 403, a first positive lens 404, and a second positive lens 405, arranged in order from the projection side to the modulation surface side. The first positive lens 404 and the second positive lens 405 are plastic lenses.

[0055] Figure 8 shows the longitudinal aberration of the optical system 400 in numerical example 4 when it is in focus on an object at infinity.

[0056] Numerical examples 1 to 4 are shown below. In the surface data for each numerical example, i indicates the order of the surfaces when counted from the projection side (i = 1, 2, 3 or more), the first surface is the aperture diaphragm, and the image surface is the modulation surface. r is the radius of curvature of the i-th surface, and d (mm) represents the on-axial spacing (distance on the optical axis) between the i-th surface and the (i+1)-th surface. nd indicates the refractive index of the optical material between the i-th surface and the (i+1)-th surface at the d-line. νd indicates the Abbe number of the optical material between the i-th surface and the (i+1)-th surface with respect to the d-line. The Abbe number νd with respect to the d-line is given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC, respectively. νd = (Nd-1) / (NF-NC) It is expressed as follows: The effective diameter is the diameter (mm) of the region on the i-th lens surface through which the light rays contributing to image formation pass.

[0057] In each numerical example, the interval d, focal length (mm), F-number, and half-angle of view (°) are all values ​​when the optical system is focused on an object at infinity. Sk is the air-equivalent distance along the optical axis from the lens surface closest to the modulation plane to the modulation plane (paraxial image plane) of the optical system described above. The total length of the lens is the length obtained by adding Sk to the distance along the optical axis from the lens surface closest to the projection plane to the lens surface closest to the modulation plane of the optical system. A lens group refers to an optical system composed of an aperture diaphragm, PBS, and multiple lenses.

[0058] If the lens surface is aspherical, the symbol * is added to the right of the surface number. The aspherical shape is expressed by the following formula, where X is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraaxial radius of curvature, K is the cone constant, and A4, A6, A8, and A10 are the aspherical coefficients of their respective orders.

[0059] X=( h 2 / R) / [1+√{1-(1+K)(h / R)2}] +A4×h4+A6×h6+A8×h8+A10×h10 Note that "e±XX" in the cone constant and aspheric coefficient means "×10±XX". [Numerical Example 1] Unit: mm Surface data Face number rd nd νd Effective diameter 1 (aperture) ∞ 0.00 1.29 2 ∞ 2.80 2.00100 29.1 1.29 3 ∞ 0.30 2.51 4 4.964 1.94 2.05090 26.9 3.01 5 -4.153 0.50 1.89286 20.4 3.09 6 4.571 2.24 3.09 7* -2.562 0.60 1.63550 23.9 3.80 8* -3.417 0.44 4.74 9* -5.292 1.89 1.53160 55.8 5.67 10* -4.013 0.20 6.95 11 34.177 3.38 1.53160 55.8 9.10 12* -16.859 (Variable) 9.90 Image plane ∞ Aspherical data The 7th surface K = 0.00000e+00 A 4=-2.59649e-02 A 6= 4.03139e-03 The 8th surface K = 0.00000e+00 A 4=-1.02227e-02 A 6= 2.30488e-03 A 8= 1.77240e-05 The 9th surface K = 0.00000e+00 A 4= 3.79178e-03 A 6=-2.28605e-04 A 8=-3.40135e-06 The 10th surface K = 0.00000e+00 A 4= 1.14388e-03 A 6= 8.89014e-05 A 8=-1.48394e-06 The 12th surface K = 0.00000e+00 A 4=-1.54677e-03 A 6= 2.89104e-05 A 8=-4.12986e-07 Various data Zoom ratio 1.00 Focal length 10.35 F-number 8.00 Half angle of view (°) 24.64 Image height 4.74 Overall length of lens 17.00 Sk 2.71 d12 2.71 Lens group data Group Starting surface Focal length Lens configuration length Front principal point position Rear principal point position ]1 1 10.35 14.29 7.73 -7.63 Single lens data Lens starting plane, focal length 1 1 0.00 2 4 2.41 3 5 -2.37 4 7 -22.18 5 9 20.65 6 11 21.74 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd Effective diameter 1 (aperture) ∞ 0.00 3.39 2 ∞ 6.00 2.00100 29.1 3.39 3 ∞ 0.30 5.99 4 10.191 2.97 2.05090 26.9 6.83 5 -7.028 0.50 1.89286 20.4 6.85 6 31.731 2.07 6.73 7* -4.334 0.70 1.63540 23.9 6.76 8* 115.293 0.30 7.67 9* -12.260 2.15 1.53160 55.8 7.70 10* -4.782 0.20 8.27 11* 6.054 4.81 1.53160 55.8 10.09 12* 22.674 (variable) 10.20 Image plane ∞ Aspherical data Side 7 K = 0.00000e+00 A 4= 1.49936e-04 A 6= 2.38340e-04 Side 8 K = 0.00000e+00 A 4=-4.16268e-03 A 6= 5.08713e-04 A 8=-1.71992e-05 9th page K = 0.00000e+00 A 4=-2.72391e-03 A 6= 6.34954e-04 A 8=-2.35547e-05 Side 10 K = 0.00000e+00 A 4= 6.32837e-04 A 6= 1.37011e-04 A 8= 2.03858e-06 Page 11 K = 0.00000e+00 A 4=-1.14308e-03 A 6=-1.88044e-05 A 8=-1.64273e-07 Side 12 K = 0.00000e+00 A 4=-1.36503e-04 A 6=-7.77598e-05 A 8= 1.71505e-06 Various data Zoom ratio 1.00 Focal length 10.16 F-number 3.00 Half-angle (°): 25.02 Image height 4.74 Lens length 23.00 Sk 3.00 d12 3.00 Lens group data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 10.16 20.00 8.32 -7.16 Single lens data Lens starting plane, focal length 1 1 0.00 2 4 4.34 3 5 -6.41 4 7 -6.56 5 9 13.41 6 11 14.12 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd Effective diameter 1 (aperture) ∞ 0.20 1.18 2* 2.448 0.61 1.76802 49.2 1.49 3* 25.294 1.07 1.64 4* -1.142 0.50 1.82115 24.1 1.76 5* -2.740 0.03 2.42 6 ∞ 3.50 2.00100 29.1 2.76 7 ∞ 0.75 5.48 8 16.742 2.85 1.53160 55.8 8.13 9* -10.169 0.00 9.00 10 26.239 2.49 1.53160 55.8 9.85 11* -9.777 (variable) 10.00 Image plane ∞ Aspherical data 2nd side K = 0.00000e+00 A 4=-2.76079e-02 A 6=-4.14277e-03 A 8=-5.28881e-02 3rd page K = 0.00000e+00 A 4=-6.02664e-02 A 6=-3.37545e-02 A 8=-3.62072e-02 Side 4 K = 0.00000e+00 A 4= 1.12176e-01 A 6=-4.92845e-03 A 8=-2.22170e-02 5th page K = 0.00000e+00 A 4= 8.36900e-02 A 6=-6.23165e-03 A 8=-8.37846e-04 9th page K = 0.00000e+00 A 4=-3.07285e-04 A 6=-4.85331e-06 A 8= 9.83178e-08 Page 11 K = 0.00000e+00 A 4= 8.49638e-05 A 6= 1.94571e-06 A 8= 2.39547e-07 Various data Zoom ratio 1.00 Focal length 9.48 F-number 8.00 Half-angle (°): 26.60 Image height 4.74 Lens length 14.00 Sk 2.00 d11 2.00 Lens group data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 9.48 12.01 7.90 -7.48 Single lens data Lens starting plane, focal length 1 1 3.49 2 4 -2.77 3 6 0.00 4 8 12.36 5 10 13.73 [Numerical Example 4] Unit: mm Surface data Face number rd nd νd Effective diameter 1 (aperture) ∞ 0.30 1.40 2 4.498 1.05 2.05090 26.9 1.73 3 -7.157 0.50 1.89286 20.4 1.89 4 4.905 0.50 1.99 5 ∞ 2.80 2.00100 29.1 2.29 6 ∞ 1.67 3.29 7* -3.261 0.60 1.63550 23.9 3.80 8* -8.878 0.20 5.15 9* -6.464 2.64 1.53160 55.8 5.48 10* -3.886 0.20 6.97 11 34.177 2.82 1.53160 55.8 9.47 12* -9.453 (variable) 10.00 Image plane ∞ Aspherical data Side 7 K = 0.00000e+00 A 4=-4.22166e-02 A 6= 3.62889e-03 Side 8 K = 0.00000e+00 A 4=-1.46593e-02 A 6= 1.84837e-03 A 8=-5.06694e-05 9th page K = 0.00000e+00 A 4= 3.58998e-03 A 6=-5.30732e-04 A 8= 7.03329e-06 Side 10 K = 0.00000e+00 A 4=-4.82206e-03 A 6= 4.97978e-04 A 8=-1.58179e-05 Side 12 K = 0.00000e+00 A 4= 2.06512e-03 A 6=-9.92771e-05 A 8= 1.17158e-06 Various data Zoom ratio 1.00 Focal length 11.21 F-number 8.00 Half-angle (°): 22.94 Image height 4.74 Lens length: 16.00 Sk 2.72 d12 2.72 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 11.21 13.27 10.77 -8.49 Single lens data Lens starting plane, focal length 1 1 2.76 2 3 -3.20 3 5 0.00 4 7 -8.46 5 9 13.53 6 11 14.25 Table 1 summarizes the values ​​of equations (1) to (13) in numerical examples 1 to 4. "E-06" is "×10 -6 This means that each numerical example satisfies all the conditions of equations (1) to (13).

[0060] [Table 1]

[0061] [Display device] Figure 10 shows the configuration of AR glasses as a display device having the optical systems of Examples 1 to 4. The AR glasses use LCOS, DMD, etc. as the reflective light modulation element 38. 31 is the light source, 32 is the reflective mirror, and 33 is the illumination optical system. 42 is the optical system of any of Examples 1 to 4, and includes, from the projection side, an aperture diaphragm 39, a PBS 35 with a polarization separation surface 34, a lens 36, and a quarter-wave plate 37. Furthermore, the optical system 42 includes a light guide plate 41, and a reflective surface 40 is provided inside the light guide plate 41.

[0062] Illumination light emitted from the light source 31, which is a laser diode (LD) or LED, is reflected by the reflective mirror 32 and incident on the PBS 35 via the illumination optical system 33. It is then reflected on the modulation side by the polarization separation surface 34 and incident on the modulation surface of the reflective optical modulation element 38 via the lens 36. The modulated light, modulated and reflected on the modulation surface, passes through the lens 36, the polarization separation surface 34, and the aperture diaphragm 39 and enters the light guide plate 41 from its incident end. It is then reflected by the reflective surface 40, propagates further within the light guide plate 41 while undergoing total internal reflection, and exits from the light guide plate 41, entering the observer's eye. This allows the observer to observe the image formed by the modulated light.

[0063] The above embodiment includes the following configuration.

[0064] (Composition 1) An optical system that guides illumination light to a modulation surface and projects modulated light from the modulation surface, A transmissive reflective surface that directs the illumination light toward the modulation surface and the modulated light toward the projection side, It has a first positive lens positioned on the modulation surface side of the transmission / reflection surface, and a second positive lens adjacent to the first positive lens on the modulation surface side. When L is the distance along the optical axis between the projection-side surface in the optical system and the modulation surface, and H is the diagonal length of the effective area of ​​the modulation surface, 0.1 ≤ L / H ≤ 5.0 An optical system characterized by satisfying the following conditions. (Configuration 2) The optical system according to configuration 1, characterized in that the surface closest to the projection side is an aperture diaphragm. (Composition 3) The optical system according to configuration 1 or 2, characterized in that the second positive lens is positioned on the side of the optical system that is closest to the modulation surface. (Composition 4) When La is the distance along the optical axis between the projection-side lens surface of the first positive lens and the modulation surface, 0.1 ≤ La / H ≤ 2.0 An optical system according to any one of configurations 1 to 3, characterized by satisfying the following conditions. (Composition 5) When the distance along the optical axis between the lens surface on the modulation side of the first positive lens and the lens surface on the projection side of the second positive lens is d, and the distance along the optical axis between the lens surface on the projection side of the first positive lens and the lens surface on the modulation side of the second positive lens is D, 0.0 ≤ d / D ≤ 0.3 An optical system according to any one of configurations 1 to 4, characterized by satisfying the following conditions. (Composition 6) When the focal length of the optical system is f and the paraxial radius of curvature of the lens surface on the modulation side of the second positive lens is rr2, 0.5 ≤ |rr²| / f ≤ 100.0 An optical system according to any one of configurations 1 to 5, characterized by satisfying the following conditions. (Composition 7) When the thickness of the second positive lens along its optical axis is de and the paraxial radius of curvature of the lens surface on the modulation side of the second positive lens is rr2, 1.5 ≤ |rr²| / de ≤ 300.0 An optical system according to any one of configurations 1 to 6, characterized by satisfying the following conditions. (Composition 8) When the focal length of the first positive lens is ffa and the focal length of the second positive lens is ffb, 0.2 ≤ ffa / ffb ≤ 2.3 An optical system according to any one of configurations 1 to 7, characterized by satisfying the following conditions. (Composition 9) The optical system according to any one of configurations 1 to 8, characterized in that the optical system is composed of five or fewer lenses. (Composition 10) The optical system according to any one of configurations 1 to 9, characterized in that the aperture diaphragm is located on the projection side of the optical system. (Composition 11) When Sd is the distance along the optical axis between the aperture diaphragm and the projection-side lens surface of the first positive lens, 0.0 <Sd / L≦0.5 The optical system according to configuration 10, characterized by satisfying the following conditions. (Composition 12) When the refractive index of the first positive lens at the d line is Nd1, Nd1 ≤ 1.6 An optical system according to any one of configurations 1 to 11, characterized by satisfying the following conditions. (Composition 13) When the refractive index of the second positive lens at the d line is Nd2, Nd2 ≤ 1.6 An optical system according to any one of configurations 1 to 12, characterized by satisfying the following conditions. (Composition 14) When the coefficient of linear expansion of the first positive lens is α1, α1 ≥ 1.0 × 10 -6 An optical system according to any one of configurations 1 to 13, characterized by satisfying the following conditions. (Composition 15) When the coefficient of linear expansion of the aforementioned second positive lens is α2, α² ≥ 1.0 × 10 -6 An optical system according to any one of configurations 1 to 14, characterized by satisfying the following conditions. (Composition 16) The optical system according to any one of configurations 1 to 15, characterized in that the transmitted and reflected surface is planar. (Composition 17) When Sk is the air-equivalent distance on the optical axis between the lens surface on the side of the modulation surface and the modulation surface in the optical system, 0.1 ≤ Sk / f ≤ 0.3 An optical system according to any one of configurations 1 to 16, characterized by satisfying the following conditions. (Composition 18) The aforementioned transmission and reflection surface is a plane arranged to make an angle θP less than 90° with respect to the optical axis. 40°≦θP≦50° An optical system according to any one of configurations 1 to 17, characterized by satisfying the following conditions. (Composition 19) The optical system according to any one of configurations 1 to 18, characterized in that a quarter-wave plate is arranged between the lens surface on the side closest to the modulation surface of the optical system and the modulation surface. (Composition 20) The optical system according to any one of configurations 1 to 19, characterized in that the transmitted reflective surface reflects the incident illumination light toward the modulation surface and transmits the modulated light from the modulation surface toward the projection side. (Composition 21) An optical system that guides illumination light to a modulation surface and projects modulated light from the modulation surface, A transmissive reflective surface that directs the illumination light toward the modulation surface and the modulated light toward the projection side, An optical system characterized by having a first positive lens positioned on the modulation surface side of the transmission / reflection surface, and a second positive lens adjacent to the first positive lens on the modulation surface side. (Composition 22) The optical system described in any one of configurations 1 to 21, A display device characterized by having an optical modulation element having the modulation surface.

[0065] 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]

[0066] 100 Optical system SP aperture diaphragm P polarization separation plane 104 First positive lens 105 Second positive lens IM Modulation Surface

Claims

1. An optical system that guides illumination light to a modulation surface and projects modulated light from the modulation surface, A transmissive reflective surface that directs the illumination light toward the modulation surface and the modulated light toward the projection side, It has a first positive lens positioned on the modulation surface side of the transmission / reflection surface, and a second positive lens adjacent to the first positive lens on the modulation surface side. When L is the distance along the optical axis between the projection-side surface in the optical system and the modulation surface, and H is the diagonal length of the effective area of ​​the modulation surface, 0.1 ≤ L / H ≤ 5.0 An optical system characterized by satisfying the following conditions.

2. The optical system according to claim 1, characterized in that the surface on the projection side is an aperture diaphragm.

3. The optical system according to claim 1, characterized in that the second positive lens is positioned on the side of the optical system that is closest to the modulation surface.

4. When La is the distance along the optical axis between the projection-side lens surface of the first positive lens and the modulation surface, 0.1 ≤ La / H ≤ 2.0 The optical system according to claim 1, characterized in that it satisfies the following conditions.

5. When the distance along the optical axis between the lens surface on the modulation side of the first positive lens and the lens surface on the projection side of the second positive lens is d, and the distance along the optical axis between the lens surface on the projection side of the first positive lens and the lens surface on the modulation side of the second positive lens is D, 0.0 ≤ d / D ≤ 0.3 The optical system according to claim 1, characterized in that it satisfies the following conditions.

6. When the focal length of the optical system is f and the paraxial radius of curvature of the lens surface on the modulation side of the second positive lens is rr2, 0.5≦|rr2| / f≦100.0 The optical system according to claim 1, characterized in that it satisfies the following conditions.

7. When the thickness of the second positive lens along its optical axis is de and the paraxial radius of curvature of the lens surface on the modulation side of the second positive lens is rr2, 1.5≦|rr2| / de≦300.0 The optical system according to claim 1, characterized in that it satisfies the following conditions.

8. When the focal length of the first positive lens is ffa and the focal length of the second positive lens is ffb, 0.2 ≤ ffa / ffb ≤ 2.3 The optical system according to claim 1, characterized in that it satisfies the following conditions.

9. The optical system according to claim 1, characterized in that the optical system is composed of five or fewer lenses.

10. The optical system according to claim 1, characterized in that the aperture diaphragm is located on the projection side of the optical system.

11. When Sd is the distance along the optical axis between the aperture diaphragm and the projection-side lens surface of the first positive lens, 0.0<Sd / L≦0.5 The optical system according to claim 10, characterized in that it satisfies the following conditions.

12. When the refractive index of the first positive lens at the d line is Nd1, Nd1 ≤ 1.6 The optical system according to claim 1, characterized in that it satisfies the following conditions.

13. When the refractive index of the second positive lens at the d line is Nd2, Nd² ≤ 1.6 The optical system according to claim 1, characterized in that it satisfies the following conditions.

14. When the coefficient of linear expansion of the first positive lens is α1, α１≧１．０×１０ －６ The optical system according to claim 1, characterized in that it satisfies the following conditions.

15. When the coefficient of linear expansion of the second positive lens is α2, α２≧１．０×１０ －６ The optical system according to claim 1, characterized in that it satisfies the following conditions.

16. The optical system according to claim 1, characterized in that the transmitted and reflected surface is planar.

17. When Sk is the air-equivalent distance on the optical axis between the lens surface on the side of the modulation surface and the modulation surface in the optical system, 0.1 ≤ Sk / f ≤ 0.3 The optical system according to claim 1, characterized in that it satisfies the following conditions.

18. The aforementioned transmission and reflection surface is a plane arranged to make an angle θP less than 90° with respect to the optical axis. 40° ≤ θP ≤ 50° The optical system according to claim 1, characterized in that it satisfies the following conditions.

19. The optical system according to claim 1, characterized in that a quarter-wave plate is disposed between the lens surface on the side closest to the modulation surface and the modulation surface.

20. The optical system according to claim 1, characterized in that the transmitted reflective surface reflects the incident illumination light toward the modulation surface and transmits the modulated light from the modulation surface toward the projection side.

21. An optical system that guides illumination light to a modulation surface and projects modulated light from the modulation surface, A transmissive reflective surface that directs the illumination light toward the modulation surface and the modulated light toward the projection side, An optical system characterized by having a first positive lens positioned on the modulation surface side of the transmission / reflection surface, and a second positive lens adjacent to the first positive lens on the modulation surface side.

22. An optical system according to any one of claims 1 to 21, A display device characterized by having an optical modulation element having the modulation surface.

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