Observation optics and display devices

Abstract

To improve transmittance with respect to polarized light transmitting a metal wire microstructure without relying upon an incidence angle in an observation optical system performing an optical path return, using the metal wire microstructure.SOLUTION: An observation optical system has: a lens GP that has a first half-transmission reflection surface R1; and a second half-transmission reflection surface R2 that is disposed on a display element side further than the first half-transmission reflection surface. The observation optical system is configured to guide light from a display element ID to an observation side via transmission of the second half-transmission reflection surface, reflection upon the first half-transmission reflection surface, reflection upon the second half-transmission reflection surface and transmission of the first half-transmission reflection surface. The first half-transmission reflection surface has a polarized light selectivity half-transmission reflection function by a metal wire microstructure, in which a pitch of the metal wire microstructure varies according to a height from an optical axis of the lens.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an observation optical system suitable for an image display device such as a head-mounted display (HMD) that enlarges and displays an original image displayed on a display element.

Background Art

[0002] As a wide-angle and small-sized observation optical system, Patent Document 1 discloses an observation optical system that performs an optical path折返 using a wire grid polarizer and a half mirror. Further, Patent Document 2 discloses that the incident angle characteristic of the transmittance with respect to polarized light changes by changing the pitch of the metal wire structure of the wire grid polarizer, and further discloses a configuration for obtaining an optimum incident angle for the wire grid polarizer by controlling the arrangement angle of the wire grid polarizer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The wire grid polarizer used in the observation optical system of Patent Document 1 has a metal wire structure with a uniform period, and the incident angle characteristic of the transmittance with respect to the polarized light transmitted through it is constant. However, in the optical path折返 using polarized light, the light rays are incident perpendicularly on the wire grid polarizer on the axis, while the light rays are incident obliquely on the peripheral portion. Therefore, if the wire grid polarizer has a metal wire microstructure suitable for normal incidence, the amount of transmitted polarized light may decrease in the peripheral portion.

[0005] It should be noted that the term "光路折り返し" in the original text seems to be a misspelling or an unclear term. I translated it as "optical path折返" for the purpose of maintaining the original text as accurately as possible. If there is a correct term, it should be replaced for a more accurate translation.Furthermore, in optical systems that perform optical path folding using wire grid polarizers, light is incident on the wire grid polarizer at spatially different angles of incidence. Therefore, even if the arrangement angle of the wire grid polarizers is controlled, as in the optical device disclosed in Patent Document 2, it is difficult to maximize the transmittance for polarization for all light at spatially different angles of incidence.

[0006] The present invention provides an observation optical system that performs optical path folding using a metal wire microstructure, and which is capable of increasing the transmittance to polarized light passing through the metal wire microstructure regardless of the angle of incidence, and a display device equipped therewith. [Means for solving the problem]

[0007] An observation optical system, as one aspect of the present invention, comprises a lens having a first semi-transparent reflective surface and a second semi-transparent reflective surface positioned closer to the display element than the first semi-transparent reflective surface, and guides light from the display element to the observation side through transmission through the second semi-transparent reflective surface, reflection at the first semi-transparent reflective surface, reflection at the second semi-transparent reflective surface, and transmission through the first semi-transparent reflective surface. The first semi-transparent reflective surface has a polarization-selective semi-transparent reflective function due to a metal wire microstructure, and the optical axis of the lens Perpendicular to A key feature of this invention is that the pitch of the metal wire microstructure changes according to the height. Furthermore, a display device using the above observation optical system also constitutes another aspect of this invention. [Effects of the Invention]

[0008] According to the present invention, in an observation optical system that performs optical path folding using a metal wire microstructure, the transmittance for polarized light passing through the metal wire microstructure can be increased regardless of the angle of incidence. [Brief explanation of the drawing]

[0009] [Figure 1] A diagram showing the optical paths of the principal rays in the on-axis and peripheral regions of the observation optical system of the embodiment. [Figure 2] A diagram illustrating the method for creating a metal wire microstructure in the example. [Figure 3]Cross-sectional view of the observation optical system of Example 1. [Figure 4] Longitudinal aberration diagram of the observation optical system of Example 1. [Figure 5] Cross-sectional view of the observation optical system of Example 2. [Figure 6] Longitudinal aberration diagram of the observation optical system of Example 2. [Figure 7] Cross-sectional view of the observation optical system of Example 3. [Figure 8] Longitudinal aberration diagram of the observation optical system of Example 3. [Figure 9] Diagram showing the spatial distribution of the incident angle of the principal ray passing through the metal wire microstructure in each example. [Figure 10] Diagram showing the spatial distribution of the metal wire microstructure in each example. [Figure 11] Diagram showing the HMD using the observation optical systems of Examples 1 to 3.

Mode for Carrying Out the Invention

[0010] Hereinafter, examples of the present invention will be described with reference to the drawings.

[0011] FIG. 1 shows the basic configuration of the observation optical system of the example. The observation optical system has a configuration for performing the optical path folding described later, and guides the light from the display element to the observation side. The observation optical system includes, in order from the observation side to the display element side, a pupil plane SP, a resin lens GP having a first semi-transmissive reflection surface R1, a first quarter-wave plate 11, a second semi-transmissive reflection surface R2, a second quarter-wave plate 12, and a polarizing plate 13. The pupil plane SP is an observation surface where the pupil of the observer is disposed. The first semi-transmissive reflection surface R1 has a polarization-selective semi-transmissive reflection function due to the metal wire microstructure. ID is the display surface of the display element, and a liquid crystal display element (LCD), an organic EL element, or the like is disposed as the display element.

[0012] Of the light emitted from the display surface ID and transmitted through the polarizing plate 13 and the second quarter-wave plate 12, a part thereof passes through the second semi-transmissive reflective surface R2, further passes through the first quarter-wave plate 11, and heads towards the first semi-transmissive reflective surface R1. A part of the light incident on the first semi-transmissive reflective surface R1 is reflected by the first semi-transmissive reflective surface R1, passes through the first quarter-wave plate 11, and heads towards the second semi-transmissive reflective surface R2. A part of the light incident on the second semi-transmissive reflective surface R2 is reflected by the second semi-transmissive reflective surface R2, passes through the first quarter-wave plate 11, and heads towards the first semi-transmissive reflective surface R1 again. A part of the light incident on the first semi-transmissive reflective surface R1 again passes through the first semi-transmissive reflective surface R1 and reaches the pupil plane SP. The divergent light emitted from a point on the display surface ID is made to approach parallel light while following the above optical path and is guided to the pupil plane SP. For this reason, the image displayed on the display surface ID is observed as a virtual image formed distantly by an observer placing the pupil near the pupil plane SP.

[0013] The first semi-transmissive reflective surface R1 has a polarization-selective semi-transmissive reflection function that reflects linearly polarized light in the same first polarization direction as the linearly polarized light transmitted through the polarizing plate 13 and transmits linearly polarized light in a second polarization direction orthogonal to the first polarization direction. Also, the slow axes of the first quarter-wave plate 11 and the second quarter-wave plate 12 are inclined by 90° with respect to each other. Also, the slow axis of the first quarter-wave plate 11 is inclined by 45° with respect to the polarization transmission axis of the polarizing plate 13. The second semi-transmissive reflective surface R2 is a half mirror formed with a dielectric multilayer film or the like.

[0014] The utilization of polarization in the observation optical system of this embodiment will be described. The light emitted from the display surface ID becomes linearly polarized by the polarizing plate 13, becomes circularly polarized by the second quarter-wave plate 12, and heads towards the second semi-transmissive reflective surface R2. A part of the circularly polarized light incident on the second semi-transmissive reflective surface R2 is reflected by the second semi-transmissive reflective surface R2 and becomes counterclockwise circularly polarized light and returns to the second quarter-wave plate 12. The counterclockwise circularly polarized light returning to the second quarter-wave plate 12 returns to the polarizing plate 13 as linearly polarized light in a second polarization direction orthogonal to the first polarization direction when it passed through the polarizing plate 13 earlier by the second quarter-wave plate 12, and is absorbed by the polarizing plate 13.

[0015] On the other hand, circularly polarized light incident on the second semi-transparent reflective surface R2 and transmitted through it is converted by the first quarter-wave plate 11 into linearly polarized light with the same polarization direction as when it first passed through the polarizer plate 13, and then incident on the first semi-transparent reflective surface (polarization-selective semi-transparent reflective surface) R1 of the resin lens GP. The linearly polarized light reflected here by the polarization-selective semi-transparent reflective function of the first semi-transparent reflective surface R1 is converted by the first quarter-wave plate 11 into circularly polarized light with the opposite polarization direction to when it was first converted into circularly polarized light by the second quarter-wave plate 12, and then incident on the second semi-transparent reflective surface R2 and reflected here. The circularly polarized light reflected by the second semi-transparent reflective surface R2, with the opposite polarization direction to before reflection, is incident on the first quarter-wave plate 11, and becomes linearly polarized light with a second polarization direction perpendicular to the first polarization direction when it first passed through the polarizer plate 13. This linearly polarized light is incident on the first semi-transparent reflective surface R1, passes through it, and is guided to the pupil surface SP.

[0016] Thus, of the light emitted from the display surface ID, only the light that passes through the polarizer 13 and the second semi-transparent reflective surface R2, is reflected by the first semi-transparent reflective surface R1, is reflected by the second semi-transparent reflective surface R2, and passes through the first semi-transparent reflective surface R1 is guided to the pupil surface SP. Optical path reversal occurs between the first semi-transparent reflective surface R1 and the second semi-transparent reflective surface R2. In the following explanation, the transmittance of the first semi-transparent reflective surface R1 for the effective light rays (polarized) guided from the display surface ID to the pupil surface SP is called the effective polarization transmittance.

[0017] In this embodiment, the pitch of the metal wire microstructure on the first semi-transparent reflective surface R1 is changed according to the height from the optical axis of the resin lens GP, in other words, according to the angle of incidence of the light (principal ray) that is reflected by the second semi-transparent reflective surface R2 and transmitted through the first semi-transparent reflective surface R1 to the first semi-transparent reflective surface R1. This optimizes the spatial distribution of the metal wire microstructure to match the spatial distribution of the angle of incidence of the principal ray to the first semi-transparent reflective surface R1, thereby increasing the effective polarization transmittance of the first semi-transparent reflective surface R1, that is, increasing the amount of light transmitted through the first semi-transparent reflective surface R1.

[0018] Specifically, as shown in Figure 1, the principal rays on the axis (on-axis rays) traveling along the optical axis of the resin lens GP within the observation optical system are incident perpendicularly to the first semi-transparent reflective surface R1, while the principal rays in the peripheral area are incident obliquely to the first semi-transparent reflective surface R1. For this reason, the pitch of the metal wire microstructure is made different on the axis and in the peripheral area (i.e., according to the height from the optical axis). That is, the pitch of the metal wire microstructure on the axis is set according to the incident angle on the axis, and the pitch of the metal wire microstructure in the peripheral area is set according to the incident angle in the peripheral area. As a result, an observation optical system is obtained in which the effective polarization transmittance of the first semi-transparent reflective surface R1 is high not only on the axis but also in the peripheral area.

[0019] Figure 2 schematically shows the method for forming a metal wire microstructure. First, a mold 21 having a fine uneven grid is used to transfer a grid of multiple protrusions 22 onto the surface of a resin lens GP. Next, metal is deposited onto the multiple protrusions 22 from an oblique angle by vapor deposition to form a fine grid-like metal wire microstructure 23. This metal wire microstructure 23 has a polarization-selective semi-transmissive reflective function.

[0020] The pitch of the uneven grid of mold 21, the pitch P of the grid-like protrusions 22 transferred to the resin lens GP, and the pitch of the fine grid-like metal wire microstructure 23 are approximately equal. Therefore, by setting the pitch of the uneven grid of mold 21, the desired pitch of the metal wire microstructure 23 can be easily obtained.

[0021] The effective diameter (effective range) is defined as the area through which effective light rays from the display surface ID to the pupil surface SP pass in the first semi-transparent reflective surface R1. In Examples 1 to 3 described later, the pitch of the convex portion 22 of the resin lens GP within the effective diameter (in other words, the pitch of the metal wire microstructure 23) is made smaller or larger in the peripheral area than in the axial area. As a result, obliquely incident light rays to the peripheral area satisfy the conditions for primary or secondary band excitation of surface plasmons of the metal wire microstructure, and an observation optical system with high effective polarization transmittance in the peripheral area of ​​the first semi-transparent reflective surface R1 is obtained.

[0022] Furthermore, in order for the fine lattice-like metal wire microstructure 23 to obtain polarization-selective semi-transmissive reflective function, it is desirable that the pitch of the protrusions 22 of the resin lens GP be 400 nm or less. In addition, by setting the shape of the mold 21 to match the shape of the surface forming the protrusions 22 of the resin lens GP, polarization-selective semi-transmissive reflective function can be imparted to the surface of the resin lens GP of various shapes.

[0023] Next, we will describe the numerical conditions that the observation optical system of the example preferably satisfies.

[0024] Within the effective diameter of the first semi-transparent reflective surface R1, if the pitch of the metal wire microstructure 23 is smaller in the peripheral region than on the axis, it is preferable that the following condition (1) is satisfied. Note that the pitch of the metal wire microstructure 23 can be considered equivalent to the pitch of the convex portion 22. Here, let P0 [nm] be the pitch on the axis, P1 [nm] be the pitch in the peripheral region, and θ [rad] be the angle of incidence to the first semi-transparent reflective surface R1 of the principal ray that passes through the first semi-transparent reflective surface R1 and reaches the pupil surface SP (towards the observation side). -0.6·{θ+(5 / 36)π}≦(P1-P0) / P0<0 (1) The condition in equation (1) concerns the relationship between the angle of incidence of the principal ray onto the first semi-transparent reflective surface R1 (i.e., the metal wire microstructure 23) and the amount of reduction in the pitch P1 at the periphery relative to the pitch P0 on the axis. θ + (5 / 36)π on the left side of equation (1) represents the angle of incidence of the effective ray, which has a larger angle of incidence relative to the principal ray at the periphery.

[0025] By satisfying the conditions of equation (1), the effective rays in the peripheral area satisfy the primary band excitation conditions for surface plasmons of the metal wire microstructure 23. Furthermore, by making the pitch P1 smaller than the pitch P0, the metal wire microstructure 23 satisfies the primary band excitation conditions for surface plasmons for broadband light including shorter wavelengths.

[0026] Furthermore, it is preferable to set the numerical range of equation (1) as follows. -0.55·{θ+(5 / 36)π}≦(P1-P0) / P0<0 (1a) Furthermore, it is even preferable to set the numerical range of equation (1) as follows.

[0027] More preferably, the numerical range of conditional expression (3) should be as follows.

[0028] -0.55·{θ+(1 / 9)π}≦(P1-P0) / P0<0 (1b) On the other hand, within the effective system of the first semi-transparent reflective surface R1, if the pitch of the metal wire microstructure 23 is larger in the peripheral area than on the axis, it is preferable that the following condition of equation (2) is satisfied. 0<(P1-P0) / P0≦1.2·(θ+(5 / 36)π) The condition in equation (2) concerns the relationship between the angle of incidence of the effective ray onto the first semi-transparent reflecting surface R1 and the amount of expansion of the peripheral pitch P1 relative to the pitch P0 on the axis. The right-hand side of equation (2), θ + (5 / 36)π, is the same as the left-hand side of equation (1).

[0029] By satisfying the conditions of equation (2), the effective rays in the peripheral area satisfy the conditions for secondary band excitation of surface plasmons in the metal wire microstructure 23. In addition, by making the pitch P1 larger than the pitch P0, the manufacturing of the metal wire microstructure 23 becomes easier.

[0030] Furthermore, it is preferable to set the numerical range of equation (2) as follows. 0<(P1-P0) / P0≦1.1·{θ+(5 / 36)π} (2a) More preferably, the numerical range of conditional expression (2) should be as follows:

[0031] 0 <(P1-P0) / P0≦1.1·{θ+(1 / 9)π} (2b) The following describes specific examples 1 to 3. Figures 3, 5, and 7 show the configurations of the observation optical systems for Examples 1, 2, and 3, respectively. Following Example 3, the numerical examples corresponding to Examples 1, 2, and 3 are shown.

[0032] Furthermore, Figure 9 shows the spatial distribution of the incident angle of effective rays to the first semi-transparent reflective surface R1 in each embodiment. Figure 9 shows the incident angle θ [rad] of effective rays when Y [mm] is the distance from the optical axis to the incident position of the effective rays to the first semi-transparent reflective surface R1. In each embodiment, on-axis rays are incident perpendicularly (θ=0) to the first semi-transparent reflective surface R1 at Y=0, whereas the incident angle of the principal rays in the peripheral area increases as Y increases.

[0033] Figure 10 shows the spatial distribution of the metal wire microstructure in each embodiment. Figure 10 shows (P1-P0) / P0 in equations (1) and (2) when Y [mm] is the distance from the optical axis to the incident position of the effective ray on the first semi-transparent reflective surface R1.

[0034] The observation optical system of Example 1 has a total field of view of 50° (half field of view of 25°) and a maximum pupil diameter of approximately Φ9 mm. A first semi-transparent reflective surface R1 having a polarization-selective semi-transparent reflective function due to a metal wire microstructure is provided on the observation-side plane of the resin lens GP.

[0035] As shown in Figure 10, in Example 1, the pitch of the metal wire microstructure is smaller in the peripheral region than along the axis, and the numerical value (P1-P0) / P0 in Example 1 satisfies the condition of equation (1).

[0036] The observation optical system of Example 2 also has a full field of view of 50° (half field of view of 25°) and a maximum pupil diameter of approximately Φ9mm. However, in this example, a first semi-transparent reflective surface R1 having a polarization-selective semi-transparent reflective function due to a metal wire microstructure is provided on the curved (concave) surface on the observation side of the resin lens GP. Conventional sheet-shaped metal wire grids are difficult to bond to curved surfaces, but in this example, a metal wire microstructure can be provided on the curved surface of the resin lens GP using the method shown in Figure 2.

[0037] As shown in Figure 10, in Example 2, the pitch of the metal wire microstructure is larger in the peripheral area than along the axis, and the numerical value (P1-P0) / P0 in Example 2 satisfies the condition of equation (2).

[0038] The observation optical system of Example 3 has a total field of view of 76° (half field of view of 38°) and a maximum pupil diameter of approximately Φ14mm. In this example, a first semi-transparent reflective surface R1 having a polarization-selective semi-transparent reflective function due to a metal wire microstructure is provided on the aspherical surface, which is the curved surface on the observation side of the resin lens GP. By using the method shown in Figure 2, the degree of freedom of the shape of the first semi-transparent reflective surface R1 is increased, and a wider-angle observation optical system can be constructed. In addition, a larger display element can be used compared to Examples 1 and 2. When a larger display element is used, as shown in Figure 9, the angle of incidence θ to the first semi-transparent reflective surface R1 in the peripheral area becomes larger than in Examples 1 and 2. In conventional metal wire grids with a uniform pitch, there is a concern that the effective polarization transmittance will decrease, especially in the peripheral area where the angle of incidence θ is large. In contrast, in this example, by making the spatial distribution of the metal wire microstructure different on the axis and in the peripheral area, the effective polarization transmittance can be increased even in the peripheral area where the angle of incidence θ is larger.

[0039] As shown in Figure 10, in Example 3, the pitch of the metal wire microstructure is smaller in the peripheral region than on the axis, and the numerical value (P1-P0) / P0 in Example 3 satisfies the condition of equation (1).

[0040] Figures 4, 6, and 8 show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the observation optical systems for numerical examples 1, 2, and 3, respectively. In each numerical example, the eye relief, which is the distance between a point on the optical axis at the pupil plane SP and the lens surface closest to the observer (the first semi-transparent reflective surface R1), is 15 mm. In the spherical aberration diagram, Fno indicates the F number, the solid line shows the spherical aberration with respect to the d line (wavelength 587.6 nm), and the dashed line shows the spherical aberration with respect to the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line ΔS shows the sagittal image plane, and the dashed line ΔM shows the meridional image plane. The distortion diagram shows the distortion with respect to the d line. The chromatic aberration diagram shows the lateral chromatic aberration at the g line. ω is the half-angle of view (°).

[0041] Furthermore, since there is a one-to-one correspondence between the aberration of light rays reaching the pupil surface SP from the light-emitting point on the display surface ID and the aberration of light rays reaching the display surface ID from the light-emitting point on the pupil surface SP, each aberration diagram shows the aberration on the display surface ID. In addition, although the diameter of the human pupil is usually around Φ4.0 mm, the pupil surface SP in each embodiment is positioned to be larger than Φ4.0 mm to account for variations in the position of the pupil.

[0042] Numerical examples 1 to 3 are shown below. In each numerical example, the surface number i indicates the order of the surfaces when counted from the pupil surface SP. r is the radius of curvature of the i-th surface (mm), d is the lens thickness or air gap between the i-th and (i+1)-th surfaces (mm), 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 based on the d-line of the optical material between the i-th and (i+1)-th surfaces. The Abbe number νd is expressed as νd = (Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the Fraunhofer lines d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm).

[0043] BF represents the back focus (mm). The back focus is the distance along the optical axis from the surface closest to the display element in the observation optical system to the display surface ID, 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 observation element to the final surface of the observation optical system, plus the back focus.

[0044] 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, R is the radius of paraxial curvature, k is the cone constant, and A4, A6, A8, and A10 are aspherical coefficients. The "ex" of the aspherical coefficient is ×10 -x It means...

[0045] x=( h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ] +A4·h 4 +A6·h6 +A8·h 8 +A10·h 10 (Numerical Example 1) Unit: mm Surface data Face number rd nd νd 1(SP) ∞ 15.00 2 ∞ 5.32 1.54390 56.0 3 ∞ 0.20 1.58 50.0 4 ∞ 4.03 1.54390 56.0 5 -42.812 -4.03 Reflective surface 6 ∞ -0.20 1.58 50.0 7 ∞ -5.32 1.54390 56.0 8 ∞ 5.32 reflective surface 9 ∞ 0.20 10 ∞ 4.03 1.54390 56.0 11 -42.812 0.50 12 ∞ 0.20 1.58 50.0 13 ∞ 0.20 1.58 50.0 14 ∞ 0.65 Image plane ∞ Focal length 13.62 F-number 1.50 Half-angle (°): 25.00 Image height 6.35 Lens length: 45.19 BF 0.65 (Numerical Example 2) Unit: mm Surface data Face number rd nd νd 1(SP) ∞ 15.00 2 -28.565 2.25 1.54390 56.0 3 ∞ 0.20 1.58 50.0 4 ∞ 5.51 1.54390 56.0 5 -24.063 -5.51 Reflective surface 6 ∞ -0.20 1.58 50.0 7 ∞ -2.25 1.54390 56.0 8 -28.565 2.25 Reflective surface 9 ∞ 0.20 1.58 50.0 10 ∞ 5.51 1.54390 56.0 11 -24.063 0.50 12 ∞ 0.20 1.58 50.0 13 ∞ 0.20 1.58 50.0 14 ∞ 0.65 Image plane ∞ Focal length 13.62 F-number 1.50 Half-angle (°): 25.00 Image height 6.35 Lens length: 40.45 BF 0.65 (Numerical Example 3) Unit: mm Surface data Face number rd nd νd 1(SP) ∞ 15.00 2* -35.343 1.00 1.54390 56.0 3 ∞ 0.20 1.58 50.0 4 ∞ 7.93 1.54390 56.0 5* -28.755 -7.93 6 ∞ -0.20 1.58 50.0 7 ∞ -1.00 1.54390 56.0 8* -35.343 1.00 9 ∞ 0.20 1.58 50.0 10 ∞ 7.93 1.54390 56.0 11* -28.755 2.00 1.64240 22.5 12* -14.875 0.28 13 ∞ 0.20 1.58 50.0 14 ∞ 0.20 1.58 50.0 15 ∞ 0.60 Image plane ∞ Aspherical data 2nd side K = 0.00000e+000 A 4=-5.87948e-005 A 6= 4.93835e-007 A 8=-1.20470e-009 A10 = 1.12314e-012 5th page K = 0.00000e+000 A 4=-7.44051e-006 A 6= 1.76963e-008 A 8= 2.04028e-012 A10 = 5.33233e-014 Side 8 K = 0.00000e+000 A 4=-5.87948e-005 A 6= 4.93835e-007 A 8=-1.20470e-009 A10 = 1.12314e-012 Page 11 K = 0.00000e+000 A 4=-7.44051e-006 A 6= 1.76963e-008 A 8= 2.04028e-012 A10 = 5.33233e-014 Side 12 K = 0.00000e+000 A 4= 1.12173e-004 A 6= 5.62249e-007 A 8=-6.35442e-009 A10 = 2.58902e-011 Focal length 16.26 F-number 1.19 Half-angle (°): 38.00 Image height 12.70 Lens length: 45.67 BF 0.60 [Display device] Figure 11 shows a head-mounted display (HMD) as an image display device using the observation optical systems of Examples 1 to 3. The HMD is mounted on the observer's head (in front of the eyes) by mounting gear (not shown).

[0046] 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.

[0047] By using the observation optical systems shown in Examples 1-3 as the right-eye and left-eye observation optical systems ROS and LOS, it is possible to realize an HMD capable of observing bright images across the entire field of view.

[0048] 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]

[0049] GP resin lens R1 First semi-transparent reflective surface R2 Second semi-transparent reflective surface SP pupil plane ID display surface 23 Metal Wire Microstructure

Claims

1. An observation optical system that guides light from a display element to the observation side, A lens having a first semi-transparent reflective surface, It has a second semi-transparent reflective surface positioned closer to the display element than the first semi-transparent reflective surface, Light from the display element is guided to the observation side via transmission through the second semi-transparent reflective surface, reflection by the first semi-transparent reflective surface, reflection by the second semi-transparent reflective surface, and transmission through the first semi-transparent reflective surface. The first semi-transparent reflective surface has a polarization-selective semi-transparent reflective function due to a metal wire microstructure. An observation optical system characterized in that the pitch of the metal wire microstructure changes according to the height of the lens perpendicular to the optical axis.

2. The observation optical system according to claim 1, characterized in that the pitch of the metal wire microstructure changes according to the angle of incidence of the principal ray onto the first semi-transparent reflective surface, which is reflected by the second semi-transparent reflective surface and transmitted through the first semi-transparent reflective surface.

3. Starting from the observer, The lens having the first semi-transparent reflective surface, The first quarter-wave plate and The second semi-transparent reflective surface, It has a second quarter-wave plate, An observation optical system according to claim 1 or 2, characterized in that it guides light from the display element to the observation side via transmission through the second quarter-wave plate, the second semi-transparent reflective surface and the first quarter-wave plate, reflection at the first semi-transparent reflective surface, transmission through the first quarter-wave plate, reflection at the second semi-transparent reflective surface, transmission through the first quarter-wave plate and transmission through the first semi-transparent reflective surface.

4. The aforementioned lens is a resin lens. The observation optical system according to any one of claims 1 to 3, characterized in that the metal wire microstructure is formed by providing metal to a plurality of protrusions on the resin lens such that the pitch differs according to the height perpendicular to the optical axis.

5. The observation optical system according to any one of claims 1 to 4, characterized in that, within the effective range of the first semi-transparent reflective surface, the pitch is smaller in the peripheral portion than on the optical axis.

6. When the pitch on the optical axis is P0, the pitch in the peripheral area is P1, and the angle of incidence of the principal ray passing through the first semi-transparent reflective surface to the first semi-transparent reflective surface is θ, -0.6×{θ+(5 / 36)π}≦(P1-P0) / P0<0 The observation optical system according to claim 5, characterized in that it satisfies the following conditions.

7. The observation optical system according to any one of claims 1 to 4, characterized in that, within the effective range of the first semi-transparent reflective surface, the pitch is larger in the peripheral portion than on the optical axis.

8. When the pitch on the optical axis is P0, the pitch in the peripheral area is P1, and the angle of incidence of the principal ray passing through the first semi-transparent reflective surface to the first semi-transparent reflective surface is θ, 0<(P1-P0) / P0≦1.2×{θ+(5 / 36)π} The observation optical system according to claim 7, characterized in that it satisfies the following conditions.

9. The observation optical system according to any one of claims 1 to 8, characterized in that the pitch on the optical axis is 400 nm or less.

10. The observation optical system according to claim 3, characterized in that the slow axis of the first quarter-wave plate and the slow axis of the second quarter-wave plate are tilted 90° relative to each other.

11. The polarizing plate is provided on the display element side of the second quarter-wave plate, The observation optical system according to claim 10, characterized in that the slow phase axis of the second quarter-wave plate is tilted at 45° with respect to the polarization transmission axis of the polarizing plate.

12. An observation optical system according to any one of claims 1 to 11, A display device characterized by having the aforementioned display element.

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