Display optical system and display device

Abstract

To reduce the weight of a display optical system.SOLUTION: The display optical system 1000 guides the display light from the display surface of the display element 1400 to the pupil plane SP. The display optical system includes a first optical system 1100, a first transmission / reflection surface A, a second optical system 1200, a second transmission / reflection surface C, and a third optical system 1300 arranged in order from the pupil surface side to the display surface side. The second optical system includes a lens having a positive axial power and a lens having a negative axial power and having an Abbe number with respect to a d-line different from that of the lens having the positive axial power. At least one of the first optical system and the third optical system has a curved surface serving as an interface with air. The Abbe number of the lens having positive on-axis power with respect to the d-line is larger than the Abbe number of the lens having negative on-axis power with respect to the d-line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a display optical system suitable for a display device such as a head-mounted display (HMD). [Background technology]

[0002] As an example of such a display optical system, Patent Document 1 discloses a display optical system that has high optical performance and reduces chromatic aberration by using a cemented lens. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 07-261088 Summary of the Invention [Problem to be solved by the invention]

[0004] The display optical system of a display device worn on the viewer's head is required to be lightweight. [Means for solving the problem]

[0005] A display optical system according to one aspect of the present invention guides display light from a display surface of a display element to a pupil plane. The display optical system includes a first optical system, a first transmissive-reflective surface, a second optical system, a second transmissive-reflective surface, and a third optical system, arranged in this order from the pupil plane side to the display surface side. The second optical system includes a lens having positive axial power and a lens having negative axial power and having a different Abbe number referenced to the d-line from that of the lens having positive axial power. At least one of the first optical system and the third optical system has a curved surface that forms an interface with air. The Abbe number referenced to the d-line of the lens having positive axial power is larger than the Abbe number referenced to the d-line of the lens having negative axial power. Note that a display device including the above display optical system also constitutes another aspect of the present invention. [Effects of the Invention]

[0006] According to the present invention, a lightweight display optical system can be provided. [Brief explanation of the drawings]

[0007] [Figure 1] 3A and 3B are a cross-sectional view and an aberration diagram of the display optical system without adjustment in Example 1. [Figure 2] FIG. 2 is a diagram showing the optical path of the display optical system in the first embodiment. [Figure 3] 4A and 4B are a cross-sectional view and an aberration diagram of the display optical system during −4D adjustment in Example 1. [Figure 4] FIG. 2 is a diagram illustrating a first transmissive-reflective surface and a second transmissive-reflective surface. [Figure 5] 4 is a diagram showing an output angle β of a display element relative to a field angle α in Example 1. FIG. [Figure 6] FIG. 2 is a diagram showing a cross-sectional shape of an optical element in Example 1. [Figure 7] 5A and 5B are a cross-sectional view and aberration diagrams of an optical system according to Example 2. [Figure 8] 10 is a diagram showing an output angle β of a display element relative to a field angle α in Example 2. FIG. [Figure 9] FIG. 10 is a diagram showing a cross-sectional shape of an optical element in Example 2. [Figure 10] FIG. 1 is a perspective view of an HMD equipped with the display optical systems of the first and second embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, before describing the first and second embodiments in detail, matters common to the first and second embodiments will be described.

[0009] The HMD as a display device in each embodiment has a display element provided for each right eye and a display optical system that guides display light from the display surface of the display element to a pupil plane. Each display optical system guides a light beam from the display surface of the display element (panel) to the pupil plane as an observation plane, and displays an enlarged version of the original image displayed on the display surface.

[0010] The display optical system of each embodiment includes, arranged in order from the pupil plane side to the display surface side, a pupil plane side optical system as a first optical system, a first transmission-reflection surface (first transmission-reflection member), a transmission-reflection optical system as a second optical system, a second transmission-reflection surface (second transmission-reflection member), and a panel side optical system as a third optical system. Both the first transmission-reflection surface and the second transmission-reflection surface are curved surfaces.

[0011] The pupil plane side optical system is an optical system arranged between the pupil plane and the first transmission-reflection surface. The transmission-reflection optical system is an optical system arranged between the first transmission-reflection surface and the second transmission-reflection surface (sandwiched between the first transmission-reflection surface and the second transmission-reflection surface). The panel side optical system is an optical system arranged between the second transmission-reflection surface and the display element.

[0012] The display optical systems of the display devices of the first and second embodiments will be specifically described below. [Example]

[0013] 1(A) shows the configuration of a display optical system 1000 for one eye in an HMD of Example 1. The display optical system 1000 has, in order from the pupil plane side to the display surface side, a pupil plane side optical system (first optical system) 1100, a first transmissive reflective member (A) having a first transmissive reflective surface, a transmissive reflective optical system (second optical system) 1200, a second transmissive reflective member (C) having a second transmissive reflective surface, and a panel side optical system (third optical system) 1300.

[0014] The pupil-plane-side optical system 1100 has a first lens 1101 as a first optical element. The transmission-reflection optical system 1200 has a second lens 1201 as a second optical element and a third lens 1202 as a third optical element. The panel-side optical system 1300 has a fourth lens 1301 as a fourth optical element. As described above, in this embodiment, the pupil-plane-side optical system 1100 has one optical element (1101, 1201, 1202, 1301) that refracts, reflects, or diffracts light rays, the transmission-reflection optical system 1200 has two optical elements (1101, 1201, 1202, 1301) that refract, reflect, or diffract light rays. Each optical element has two optical surfaces, R1 and R2, from the pupil-plane side, and all of these optical surfaces are curved.

[0015] Display light from the panel unit 1400 including the display element passes through the panel-side optical system 1300, the second transmission-reflection surface (C), and the transmission-reflection optical system 2200. The display light is then reflected once each by the first transmission-reflection surface (A) and the second transmission-reflection surface (C), passes through the transmission-reflection optical system 1200, and then passes through the pupil-plane-side optical system 1100 toward the pupil plane SP. This allows the observer to view a virtual image (display image) of the original image displayed on the display element through their eye, which is located at the pupil plane SP where the exit pupil of the display optical system 1000 is located. The light that follows the optical path for forming the display image at this time is referred to as display light, and the rest is referred to as unwanted light. In this embodiment (and other embodiments described below), the pupil plane SP is the position of the entrance pupil of the observer's eye, not the vertex of the cornea.

[0016] 1B shows the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the display optical system 1000 in this embodiment when the eye relief is 12 mm and a virtual image is displayed at a position 1600 mm from the pupil plane SP. The eye relief is the distance on the optical axis (hereinafter simply referred to as on the axis) from the pupil plane SP to the lens surface of the pupil plane-side optical system 1100 closest to the pupil plane. Here, the longitudinal aberration is shown when the panel unit 1400 is the image plane in the reverse optical path (reverse tracing) from the pupil plane SP to the panel unit 1400, rather than the forward optical path (forward tracing) from the panel unit 1400 to the pupil plane SP. The longitudinal aberration in the reverse tracing corresponds to the longitudinal aberration in the forward tracing.

[0017] In the spherical aberration diagrams, Fno indicates the F-number, the solid line indicates the spherical aberration at the reference wavelength, the d-line (wavelength 587.6 nm), the two-dot chain line indicates the spherical aberration at the g-line (wavelength 435.8 nm), and the one-dot chain line indicates the spherical aberration at the C-line (wavelength 656.3 nm). In the astigmatism diagrams, the solid line S indicates the astigmatism at the sagittal image plane, and the dashed line M indicates the astigmatism at the meridional image plane. The distortion aberration diagrams show the distortion aberration at the d-line. The chromatic aberration diagrams show the chromatic aberration of magnification at the g-line and C-line. These aberration diagrams show that the display optical system 1000 of this embodiment has good imaging performance.

[0018] The polarizing plate described below has the following specifications: thickness 0.1 mm, refractive index at d-line 1.52, and Abbe number based on d-line 50. The quarter-wave plate and the laminated element of the quarter-wave plate and the polarization-selective transmission / reflection element have the following specifications: thickness 0.3 mm, refractive index at d-line 1.52, and Abbe number based on d-line 50. However, the actual specifications may differ from these.

[0019] 2 shows the direction and polarization state of display light passing through each surface in the display optical system 1000. The panel unit 1400 has a display element (light modulation element) such as a liquid crystal display element or an organic EL element, a polarizing plate E, and a second quarter-wave plate D. The shape of the display element is a square with a diagonal of 2.1 inches (each side is 37.7 mm). In order towards the pupil plane, the display element, polarizing plate E, and second quarter-wave plate D are arranged close to each other.

[0020] The display light emitted from the display element as unpolarized light is converted into linearly polarized light by the polarizing plate E. This linearly polarized light is converted into circularly polarized light by the second quarter-wave plate D, and the circularly polarized light passes through the panel-side optical system 1300, and further passes through a transmission-reflection film (half mirror) C serving as a second transmission-reflection member having a second transmission-reflection surface, and enters the transmission-reflection optical system 1200.

[0021] The transflective film C is formed of a dielectric multilayer film or a metal film, and is deposited on the R1 surface of the fourth lens 1301 of the panel-side optical system 1300, and is further bonded to the R2 surface of the third lens 1202. The thickness of the transflective film C is usually 1000 nm or less or 5000 nm or less, and will not be shown in the figures or described in the numerical examples to be described later.

[0022] The polarizing plate E may be integrally formed with the display element. For example, many liquid crystal display elements include a polarizing plate in their construction, and polarizing plates are sometimes used in organic EL elements for the purpose of anti-reflection. In such cases, the light emitted from the display element becomes linearly polarized. In this case, there is no need to provide a separate polarizing plate E.

[0023] The transmission-reflection optical system 1200 has a third lens 1202, a first quarter-wave plate B, and a second lens 1201. The first quarter-wave plate B is arranged so that its slow axis is inclined at 90° with respect to the slow axis of the second quarter-wave plate D, and is also inclined at 45° with respect to the polarization transmission axis of the polarizing plate E. The first quarter-wave plate B is bonded to the R1 surface of the second lens 1201.

[0024] The circularly polarized light incident on the transmission-reflection optical system 1200 is converted by the first quarter-wave plate B into linearly polarized light having the same polarization direction as when it passed through the polarizing plate E, and then incident on the polarization-selective transmission-reflection element A. This linearly polarized light is reflected by the polarization selectivity of the polarization-selective transmission-reflection element A.

[0025] The polarization-selective transmission-reflection element A is an element that reflects linearly polarized light in the same polarization direction as when it passed through the polarizing plate E and transmits linearly polarized light in a polarization direction perpendicular to the polarized light, and is configured, for example, by a wire grid polarizer or a laminated birefringent film polarizer. Examples of wire grid polarizers include the "WGF" manufactured by Asahi Kasei Corporation, and the wire grid-formed surface functions as the transmission-reflection surface. In this embodiment, the polarization-selective transmission-reflection element A typically has a thickness of 0.5 mm or less or 1 mm or less, and is bonded to the R2 surface of the first lens 1101 of the pupil-plane-side optical system 1100.

[0026] Each transmissive-reflective member includes a transmissive-reflective surface, is an integral member with the transmissive-reflective surface, has almost no refractive power, and is primarily responsible for optical functions other than refraction (such as absorption according to the polarization state, change in the polarization state, and anti-reflection) and mechanical functions (such as adhesion and protection). In this embodiment, the polarization-selective transmissive-reflective element A corresponds to a first transmissive-reflective member having a first transmissive-reflective surface, and the transmissive-reflective film C corresponds to a second transmissive-reflective member having a second transmissive-reflective surface. Each transmissive-reflective member may be composed of a series of members having multiple functions.

[0027] The display light reflected by the polarization-selective transflective element A is converted by the first quarter-wave plate B into circularly polarized light with the same rotation as when it was first converted into circularly polarized light by the second quarter-wave plate D, and then enters the transflective film C, where it is reflected.

[0028] The display light reflected by the transflective film C becomes circularly polarized light in the opposite direction to the light before reflection, enters the first quarter-wave plate B again, and is converted into linearly polarized light with a polarization direction perpendicular to the polarization direction when the light first passed through the polarizer E, and then enters the polarization-selective transflective element A. This linearly polarized light is transmitted by the polarization-selective transflective element A and directed to the pupil plane SP. In this way, the display optical system 1000 employs a triple-path design that folds the optical path twice, thereby enabling it to display a sufficiently enlarged display image despite its compact configuration.

[0029] [Weight of display optical system] The transmission-reflection optical system 1200, in which light rays pass three times, is more effective in reducing chromatic aberration than the pupil-plane-side optical system 1100 or the panel-side optical system 1300, in which light rays pass only once. In this case, the shape of the optical surface for reducing chromatic aberration does not need to have a large curvature, and only a small amount of sag from the plane is required, which is also preferable from the perspective of weight.

[0030] The display optical system disclosed in Patent Document 1 reduces chromatic aberration by using a cemented lens in a transflective optical system. Furthermore, by selecting a combination of glass materials with an appropriate refractive index and Abbe number, curvature of field and astigmatic difference are reduced without providing curved surfaces at the interface with air in the pupil-side optical system and the panel-side optical system. However, the combinations of glass materials that can achieve this are quite limited, and it is also difficult to select a glass material that is preferable from the perspective of weight.

[0031] To reduce the weight of a display optical system, it is particularly effective to use a resin material with a low specific gravity rather than a glass material. However, resin materials have fewer variations in refractive index and Abbe number than glass materials. Moreover, for lenses used in transmission / reflection optical systems in particular, only resin materials with a very small amount of birefringence that changes the polarization state can be used in order to avoid the generation of unwanted light.

[0032] Therefore, it is important to effectively reduce chromatic aberration, curvature of field, and astigmatic difference while ensuring a certain degree of freedom in selecting lens materials.One approach is to select a resin material that reduces chromatic aberration in situations where there is little freedom in selecting a resin material with an appropriate refractive index and Abbe number, and thereby correct the increased curvature of field and astigmatic difference.

[0033] As described above, reducing chromatic aberration in the transmission-reflection optical system 1200 is effective for reducing chromatic aberration. Specifically, a lens having positive axial power (power is the reciprocal of focal length, and is also called refractive power) and a lens having negative axial power are provided in the transmission-reflection optical system 1200. When the Abbe number of the lens having positive axial power based on the d-line is v1 and the Abbe number of the lens having negative axial power based on the d-line is v2, it is preferable to satisfy the condition of the following formula (1):

[0034] 20≦ν1-ν2 (1) It is more preferable that the numerical range of the formula (1) is as follows:

[0035] 25≦ν1-ν2 (1a) Furthermore, it is more preferable that the numerical range of formula (1) is as follows:

[0036] 30≦ν1-ν2 (1b) Although the condition of having these Abbe number differences imposes some constraints on the selection of resin materials, there is ample freedom in the selection of resin materials since there are no constraints on the refractive index.

[0037] To correct the increased field curvature and astigmatic difference, it is effective to provide a curved surface at least in one of the pupil-plane-side optical system 1100 and the panel-side optical system 1300 that serves as an interface with air. Because the light rays passing through the transmission-reflection optical system 1200 three times pass through different positions on the optical surfaces, it is difficult to optimize the field curvature and astigmatic difference of the light beam for each angle of view using the optical surfaces within the transmission-reflection optical system 1200. To reduce both the field curvature and astigmatic difference, it is preferable to provide the pupil-plane-side optical system 1100 and the panel-side optical system 1300 spaced apart from each other and provide a curved surface at least in one of them that serves as an interface with air, thereby optimizing the field curvature and astigmatic difference of the light beam for each angle of view. This allows for satisfactory reduction of chromatic aberration, field curvature, and astigmatic difference while maintaining sufficient flexibility in the selection of resin materials.

[0038] Even if a curved surface is provided at the cemented surface instead of at the interface with air, it is difficult to sufficiently correct the curvature of field and astigmatic difference because the effect of refraction is small.

[0039] In this embodiment, a second lens 1201 having positive axial power and a third lens 1202 having negative axial power are provided in a transmission / reflection optical system 1200. The Abbe number of the second lens 1201 based on the d-line is defined as ν1, and the Abbe number of the third lens 1202 cemented to the second lens 1201 with a first quarter-wave plate B sandwiched therebetween is defined as ν2 based on the d-line. In this case, ν1=56.0, ν2=22.38 Therefore, 30≦ν1-ν2=34.62 This satisfies the condition of equation (1).

[0040] The second lens 1201 and the third lens 1202 are both made of resin, and by using them, the weight can be reduced compared to when glass lenses are used. Also, as mentioned above, the birefringence of these resin materials is quite small, so unwanted light can be reduced.

[0041] As described above, in this embodiment, by providing lenses having positive and negative axial powers in the transmission-reflection optical system 1200 and setting the difference between their Abbe numbers to a predetermined value or more, it is possible to reduce the weight of the display optical system 1000 while reducing chromatic aberration. Note that the bonding in this embodiment is not limited to bonding using an adhesive, and includes vapor deposition, pressure bonding, and the like. Furthermore, it is sufficient that the bonding is performed at least in the effective light beam area through which light beams pass.

[0042] In this embodiment, the R1 surface of the first lens 1101 in the pupil plane side optical system 1100 and the R2 surface of the fourth lens 1301 in the panel side optical system 1300 are curved surfaces that interface with air. In this way, by providing a curved surface that interfaces with air in at least one of the panel side optical system 1300 and the pupil plane side optical system 1100, it is possible to correct field curvature and astigmatic difference.

[0043] In a display optical system with a wide viewing angle like this embodiment, the curvature of field and astigmatic difference tend to be large. For this reason, it is desirable to provide an aspherical surface to correct these. In this case, surfaces with particularly strong curvature tend to have a shape that requires only a small amount of sag from a flat surface, which is also preferable from the perspective of reducing the weight of the lens.

[0044] Furthermore, in this embodiment, aspherical surfaces are provided at the interfaces with air on both the panel-side optical system 1300 and the pupil-plane-side optical system 1100, which are spaced apart from each other. This makes it possible to reduce field curvature and astigmatic difference with higher precision than when an aspherical surface is provided on only one of the panel-side optical system 1300 and the pupil-plane-side optical system 1100. This configuration also contributes to reducing the exit angle, which will be described later.

[0045] As a result, in this embodiment, chromatic aberration, field curvature, and astigmatism (astigmatic difference) can be effectively reduced as shown in FIG. 1(B) while ensuring sufficient freedom in selecting the resin material.

[0046] Furthermore, in this embodiment, the transmission-reflection optical system 1200 includes a cemented surface where the second lens 1201 and the third lens 1202 are cemented with the first quarter-wave plate B sandwiched therebetween, which contributes to reducing chromatic aberration. The shapes of the first transmission-reflection surface and the second transmission-reflection surface affect the overall imaging performance, and therefore do not offer design freedom primarily aimed at reducing chromatic aberration. When a cemented surface is provided within the transmission-reflection optical system 1200, as in this embodiment, its shape does not significantly affect imaging performance other than chromatic aberration, and design freedom is increased primarily aimed at reducing chromatic aberration, resulting in a significant reduction in chromatic aberration. Furthermore, compared to when the second lens 1201 and the third lens 1202 are not cemented together, the increase in chromatic aberration due to assembly errors during manufacturing is reduced, and manufacturing is made easier.

[0047] Furthermore, in order to reduce sensitivity to imaging performance due to manufacturing errors, positioning errors, and the like other than chromatic aberration, it is preferable that the difference in power between the lens with positive axial power and the lens with negative axial power is not large. Specifically, it is preferable that the focal length f1 of the second lens 1201 with positive axial power and the focal length f2 of the third lens 1202 with negative axial power satisfy the condition of the following formula (2). The focal lengths referred to here are paraxial focal lengths.

[0048] 0.25≦|f2 / f1|≦4.00 (2) In this embodiment, f1=100.9mm f2=-215.1mm 0.25≦|f2 / f1|=2.13≦4.00 This satisfies the condition of equation (2).

[0049] In this embodiment, as described above, the second lens 1201 and the third lens 1202 are cemented together with the first quarter-wave plate B sandwiched therebetween. This reduces the refractive power at the surface of the first quarter-wave plate B, which has the advantage of allowing the surface roughness standard of the first quarter-wave plate B, which is made of a material softer than the lens, to be tolerated. Furthermore, it is not necessary to provide an anti-reflection coating on the first quarter-wave plate B, and the first quarter-wave plate B can be manufactured separately from the transmissive / reflective member.

[0050] In this embodiment, the cemented surfaces are spherical, which makes it easier to manufacture the second lens 1201 and the third lens 1202 than if they were complex aspherical surfaces.

[0051] In terms of weight reduction, it is preferable for the display optical system 1000 for HMD to have a total thickness on the optical axis of optical elements having refractive power or diffractive power of 20 mm or less. In this embodiment, the thicknesses d111, d121, d122, and d131 of the first lens 1101, second lens 1201, third lens 1202, and fourth lens 1301, respectively, and their total thickness d1sum, are as follows:

[0052] d111=5.4mm d121=5.8mm d122=1.5mm d131=6.7mm d1sum=19.4mm The sum d1sum is 20 mm or less. Note that the polarizing plate, quarter-wave plate, and polarization-selective transmission / reflection element have little effect on the weight of the display optical system 1000, so their thicknesses do not need to be taken into consideration.

[0053] Furthermore, in this embodiment, there is an air gap between the polarization-selective transmission-reflection element A and the optical element 1201. That is, the transmission-reflection optical system 1200 sandwiched between the first transmission-reflection surface and the second transmission-reflection surface includes an air gap. This allows the weight of the display optical system 1000 to be reduced compared to when the transmission-reflection optical system 1200 is made up of optical elements without an air gap.

[0054] Furthermore, this embodiment has a diopter adjustment mechanism that utilizes the air gap to adjust the diopter by driving a first lens 1101 having a polarization-selective transmission / reflection element A as shown in Fig. 1(A). This allows focus adjustment (diopter adjustment) to be performed to suit the visual acuity (field of view) of various observers.

[0055] Figure 3(A) shows the optical path when the diopter is adjusted for a person with a viewing angle of -4D (nearsightedness), and Figure 3(B) shows the longitudinal aberration at that time. Figure 3(B) shows that even with diopter adjustment, sufficiently good imaging performance is obtained.

[0056] In this embodiment, the distance between the polarization-selective transmission / reflection element A and the transmission / reflection film C is highly sensitive to the focus position, so the driving amount of the first lens 1101 when adjusting the diopter is reduced. As a result, the HMD can be made smaller (thinner) and lighter in weight while still having a diopter adjustment mechanism.

[0057] Furthermore, by reducing the size (thinning) of the display optical system 1000, the components supporting the display optical system 1000 can be made smaller, further reducing the weight of the HMD. To reduce the size of the display optical system 1000, shortening the focal length of the display optical system 1000 is beneficial. However, shortening the focal length at a wide viewing angle tends to increase field curvature and astigmatic difference. This disadvantage is preferably addressed by providing a curved surface at the interface with air, as described above. In other words, combining this configuration with the previous configuration is preferable. Therefore, it is effective to make the axial powers of both the pupil-plane-side optical system 1100 and the panel-side optical system 1300 positive. From the perspective of imaging performance, the axial power of the transmission-reflection optical system 1200 is positive. As a result, the axial powers of all three optical systems 1100, 1200, and 1300 are positive. In this case, it is easier to shorten the focal length of the display optical system 1000 than when the axial power of at least one of the pupil-plane-side optical system 1100 and the panel-side optical system 1300 is negative.

[0058] In this embodiment, the focal length of the pupil plane side optical system 1100 is 176.5 mm, and the focal length of the panel side optical system 1300 is 109.9 mm, both of which are positive.

[0059] In this embodiment, the R1 surface of the first lens 1101, which serves as the pupil-facing surface facing the pupil plane SP, has a convex shape toward the pupil plane. When tracing the optical path back from the pupil plane SP, the refraction of the light beam at the pupil-facing surface is greater when the pupil-facing surface has a flat or convex shape than when the pupil-facing surface has a concave shape toward the pupil plane. This allows the display optical system 1000 to be made smaller in the radial direction, and the weight of the display optical system 1000 to be reduced.

[0060] Furthermore, if the pupil-facing surface has a concave shape toward the pupil plane, the optical surface will protrude toward the pupil plane beyond the eye relief, which may interfere with the observing eye, which is undesirable. In particular, there is a high possibility that the holding member that holds the first lens 1101 having the pupil-facing surface will protrude toward the pupil plane. For this reason, it is preferable that the pupil-facing surface has at least a flat shape, and it is more preferable that it has a convex shape toward the pupil plane.

[0061] As described above, the display optical system 1000 of this embodiment has a total of four optical elements, including one lens in the pupil-plane-side optical system 1100, two lenses in the transmission-reflection optical system 1200, and one lens in the panel-side optical system 1300. This is the minimum number of optical elements required to obtain the effects described above, and is therefore preferable not only from the perspective of reducing the size (thinning) and weight of the display optical system 1000, but also from the perspective of ease of manufacture.

[0062] Next, we will explain the emission angle of display light from a display element, which is related to field curvature, astigmatic difference, and miniaturization. Figures 4(A) and (B) respectively show the optical path of a light ray emitted from an image height h on a display element, the emission angle β of the light ray from the display element, and the angle of view α on the pupil plane SP when the first transflective surface (polarization-selective transflective element A) has a planar shape and a concave shape toward the pupil plane side. Here, refraction is not shown in order to explain the reflection of the light ray. Also, curved surfaces will be described as spherical surfaces.

[0063] Since display elements typically emit Lambertian light, the smaller the emission angle β, the greater the amount of light taken in by the display optical system, and the greater the emission angle β, the less light taken in by the display optical system. Therefore, if the maximum value of the emission angle β is large within the range of the designed viewing angle, unevenness in the amount of light will occur within the field of view of the observer. As mentioned above, a larger angle of view α (i.e., a wider viewing angle) is preferable because it makes it easier for the observer to feel immersed, but the maximum value of the emission angle β tends to become larger.

[0064] Figure 4(A) shows a case where the first transmission-reflection surface has a flat shape and the second transmission-reflection surface (transmission-reflection film C) has a concave shape facing the pupil plane. This configuration is suitable for increasing the angle of view α, but is not suitable for decreasing the exit angle β. Figure 4(B) shows a case where both the first transmission-reflection surface and the second transmission-reflection surface have a concave shape facing the pupil plane. This configuration is suitable for decreasing the exit angle β and increasing the angle of view α.

[0065] In other words, when only reflection is considered, a configuration in which both the first and second transmission-reflection surfaces have a concave shape facing the pupil plane, as shown in FIG. 4(B), is preferable in terms of the exit angle β and the angle of view α.

[0066] It is preferable that the first and second transflective surfaces, which are concave toward the pupil plane, are aspherical in order to effectively reduce field curvature and astigmatic difference, particularly in a display optical system with a wide viewing angle. In this embodiment, the R2 surface of the first lens 1101, which is modeled by the first transflective surface (polarization-selective transflective element A), is an aspherical surface rather than a spherical surface.

[0067] In this embodiment, the third lens 1202 and the fourth lens 1301, which are refractive elements, are cemented together with a second transmissive-reflective member (transmissive-reflective film C) including a second transmissive-reflective surface sandwiched therebetween. This configuration reduces the refractive power of the second transmissive-reflective surface compared to when the second transmissive-reflective surface is in contact with air. As a result, when determining the shape of the second transmissive-reflective surface, it is sufficient to mainly consider the influence of the reflective power, thereby increasing the degree of freedom in optical design. This allows for improved imaging performance while reducing the exit angle β. This is particularly effective in reducing field curvature and astigmatic difference in the display optical system 1000 with a wide viewing angle. Furthermore, cementing the third lens 1202 and the fourth lens 1301 improves the relative positional accuracy of these lenses, thereby improving ease of manufacturing.

[0068] Although it depends on the characteristics of the display element, generally, if the maximum absolute value of the emission angle β is greater than 35°, unevenness in the amount of light is likely to occur. For this reason, the maximum absolute value of the emission angle β is preferably 35° or less, and more preferably 30° or less.

[0069] In order to reduce the maximum absolute value of the emission angle β, it is effective to provide an aspheric surface on the optical surface that interfaces with air in the panel-side optical system 1300. This is because the light beams in the panel-side optical system 1300 are separated for each angle of view compared to the pupil-plane-side optical system 1100 and the transmission-reflection optical system 1200.

[0070] In this embodiment, a maximum half angle of 50° is assumed as the design nominal viewing angle. Specifically, the maximum angle of the chief ray of the display light passing through the pupil plane SP (the light ray passing through the center of the pupil plane SP) is set to 50°. Generally, a maximum half angle of 30° or more can be said to be a wide viewing angle, and a maximum half angle of 40° or more is more preferable. This is because the wider the viewing angle (the larger the output angle β), the more likely it is that the unevenness in the amount of light will increase.

[0071] 5 shows the angle of emergence β (angle with respect to the normal to the display element) of the chief ray from the display element relative to the angle of view α of the display optical system 1000. The angle of emergence β is negative (-) when emitted in a direction away from the optical axis, and positive (+) when emitted in a direction toward the optical axis.

[0072] From Figure 5, it can be seen that the output angle β at the maximum half angle of view is -9.1°, and the maximum absolute value of the output angle β is smaller than 30°. When evaluating the unevenness in the amount of light, the output angle β is evaluated not by whether it is positive or negative, but by its absolute value.

[0073] Furthermore, when the output angle β at the maximum half angle of view is negative as in this embodiment, the size of the display element relative to the viewing angle and eye relief specifications can be reduced, which is preferable from the viewpoint of weight.

[0074] Next, the aspherical shapes of the optical surfaces of the pupil-plane-side optical system 1100 and the panel-side optical system 1300, which are interfaces with air, will be described.

[0075] In order to reduce the field curvature and astigmatic difference for each angle of view with high precision in the wide-viewing-angle display optical system 1000, it is preferable that the effective light area (the range through which display light from the display element can pass) of at least one optical surface has a high-order aspherical shape. Specifically, it is preferable that the cross-sectional shape including the optical axis cannot be expressed by a conic section (i.e., an ellipse, a parabola, or a hyperbola). This is also preferable from the viewpoint of reducing the output angle β.

[0076] 6(A) and (B) respectively show, with solid lines, the cross-sectional shape of the R1 surface of the first lens 1101, including the optical axis, and the cross-sectional shape of the R2 surface of the fourth lens 1301, including the optical axis. The position of each surface along the optical axis is z (mm), with the vertex of the surface z = 0, and positive values ​​are assumed from the pupil plane side to the display surface side. The radial distance from the optical axis is y (mm). The scale of the graphs differs for each surface. The R1 surface of the first lens 1101 and the R2 surface of the fourth lens 1301 have cross-sectional shapes that cannot be expressed by conic sections.

[0077] 6(A) further shows the paraxial curvature surface shape of a cross section including the optical axis of surface R1 of first lens 1101 with a dashed line, and the difference from the cross section shape shown with a solid line is shown with a two-dot chain line. Fig. 6(B) further shows the paraxial curvature surface shape of a cross section including the optical axis of surface R2 of fourth lens 1301 with a dashed line, and the difference from the cross section shape shown with a solid line is shown with a two-dot chain line.

[0078] The absolute value of the ratio of the above difference to the paraxial curvature surface shape indicates the degree of aspherization (hereinafter referred to as asphericity). Although it is not proportional to the asphericity, a certain degree of asphericity is more effective in reducing the exit angle β and reducing the field curvature and astigmatic difference with high precision for each angle of view. Generally, the asphericity becomes larger toward the edge of the effective light beam area, and the above effect is easily achieved if the asphericity at the edge of the effective light beam area is 30% or more. In other words, when the sag amount of the paraxial curvature surface shape at the edge of the effective light beam area of ​​an aspheric surface is SagR and the sag amount of the cross-sectional shape of the aspheric surface is SagA, 0.3 ≤ |(SagA-SagR) / SagR| It is preferable to satisfy the following conditions.

[0079] Furthermore, if the asphericity at the edge of the effective light area is 50% or more, the above effect can be sufficiently obtained. However, even if the asphericity at the edge of the effective light area is less than 30%, the above effect can be obtained to some extent.

[0080] In this embodiment, the sag amount SagA of the cross-sectional shape including the optical axis at the edge of the effective beam area of ​​the R1 surface of the first lens 1101 (maximum effective diameter Φ40 mm) is 0.96 mm, and the sag amount SagR of the paraxial curvature surface shape is 0.20 mm. The asphericity at the edge of the effective beam area is |(SagA-SagR) / SagR| = 380% This becomes:

[0081] The sag amount SagA of the cross section including the optical axis at the edge of the effective beam area of ​​the R2 surface of the fourth lens 1301 (maximum effective diameter Φ46 mm) is −10.73 mm, and the sag amount SagR of the paraxial curvature surface shape is −12.34 mm. The asphericity at the edge of the effective beam area is |(SagA-SagR) / SagR| = 13.0% This becomes:

[0082] In this way, by making the asphericity at the edge of the effective light area, particularly on the R1 surface of the first lens 1101, 50% or more, it is possible to obtain sufficient effects such as reducing the exit angle β and reducing the field curvature and astigmatic difference with high precision for each angle of view.

[0083] According to the present embodiment described above, the display optical system 1000 can ensure high optical performance and reduce chromatic aberration and weight. [Example]

[0084] Second Embodiment Next, a display optical system 2000 according to a second embodiment of the present invention will be described. In this embodiment, the same description as in the first embodiment will be omitted.

[0085] 7(A) shows the configuration of a display optical system 2000. The display optical system 2000 has, in order from the pupil plane side to the display surface side, a pupil plane side optical system (first optical system) 2100, a first transmissive reflecting member (A) having a first transmissive reflecting surface, a transmissive reflecting optical system (second optical system) 2200, a second transmissive reflecting member (C) having a second transmissive reflecting surface, and a panel side optical system (third optical system) 2300.

[0086] The pupil plane side optical system 2100 has a first lens 2101 as a first optical element. The transmission / reflection optical system 2200 has a second lens 2201 as a second optical element and a third lens 2202 as a third optical element. The panel side optical system 2300 has a fourth lens 2301 as a fourth optical element. Thus, the pupil plane side optical system 2100 has one optical element (2101, 2201, 2202, 2301) that refracts, reflects, or diffracts light rays, the transmission / reflection optical system 2200 has two optical elements, and the panel side optical system 2300 has one optical element (2101, 2201, 2202, 2301). The R1 and R2 surfaces of the first lens 2101 are both curved surfaces. The R1 surface of the second lens 2201 is a curved surface and the R2 surface is flat. The R1 surface of the third lens 2202 is a flat surface and the R2 surface is curved. The R1 and R2 surfaces of the fourth lens 2301 are both curved surfaces.

[0087] Display light from the panel unit 2400 including a display element passes through the panel-side optical system 2300, the second transmission-reflection surface (C), and the transmission-reflection optical system 2200. The display light is then reflected once each by the first transmission-reflection surface (A) and the second transmission-reflection surface (C), passes through the transmission-reflection optical system 2200, and further passes through the pupil-plane-side optical system 2100 toward the pupil plane SP. This allows the viewer to view a virtual image (display image) of the original image displayed on the display element through their eye, which is located on the pupil plane SP where the exit pupil of the display optical system 2000 is located.

[0088] 7(B) shows the longitudinal aberration of the display optical system 2000 when the eye relief (the distance from the pupil plane SP to the lens surface of the pupil plane-side optical system 2100 closest to the pupil plane) is set to 12 mm and a virtual image is displayed at a position 1600 mm from the pupil plane SP. The explanation of each aberration diagram is the same as in Example 1 (FIG. 1(B), etc.). From FIG. 7(B), it can be seen that the display optical system 2000 of this example has good imaging performance.

[0089] The configuration of the panel unit 2400 is the same as that of the panel unit 1400 of Example 1. A transmission-reflection film (half mirror) C is deposited on the R1 surface of the fourth lens 2301. A first quarter-wave plate B is bonded to the R2 surface of the second lens 2201 and the R1 surface of the third lens 2201. A polarization-selective transmission-reflection element A is bonded to the R2 surface of the first lens 2101 in the pupil-plane-side optical system 2100 and the R1 surface of the second lens 2201 in the transmission-reflection optical system 2200. In this example as well, the polarization-selective transmission-reflection element A corresponds to the first transmission-reflection member having a first transmission-reflection surface, and the transmission-reflection film C corresponds to the second transmission-reflection member having a second transmission-reflection surface.

[0090] 8 shows the direction and polarization state of the display light passing through each surface in the display optical system 2000. The direction and polarization state of the display light are the same as those in the first embodiment (FIG. 2).

[0091] In this embodiment, a transmission-reflection optical system 2200 has a third lens 2202 having positive axial power and a second lens 2201 having negative axial power. The third lens 2202 and the second lens 2201 are cemented together with a first quarter-wave plate B sandwiched therebetween. When the Abbe number of the third lens 2202 based on the d-line is v1 and the Abbe number of the second lens 2201 based on the d-line is v2, ν1=56.0, ν2=22.38 Therefore, 30≦ν1-ν2=34.62 This satisfies the condition of equation (1).

[0092] As in Example 1, the second lens 2201 and the third lens 2202 are both resin lenses, which allows for a reduction in weight compared to when glass lenses are used. Furthermore, these resin materials have significantly small birefringence, which allows for a reduction in unwanted light.

[0093] In this way, by providing two lenses with positive and negative axial power in the transmission-reflection optical system 2200 and ensuring that the difference in the Abbe numbers of the respective resin materials is equal to or greater than a predetermined value, it is possible to reduce the weight of the display optical system 2000 while also reducing chromatic aberration.

[0094] Furthermore, in this embodiment, the R1 surface of the first lens 2101 of the pupil plane side optical system 2100 and the R2 surface of the fourth lens 2301 of the panel side optical system 2300 are curved surfaces that interface with air. In this way, by providing a curved surface that interfaces with air in at least one of the panel side optical system 2300 and the pupil plane side optical system 2100, it is possible to correct field curvature and astigmatic difference.

[0095] Also in this embodiment, as in Example 1, the R1 surface of the first lens 2101, which is the interface with air, and the R2 surface of the fourth lens 2301 of the panel-side optical system 2300 are aspheric surfaces in both the panel-side optical system 2300 and the pupil-plane-side optical system 2100. This configuration has the effect of reducing the exit angle β and reducing the field curvature and astigmatic difference with high precision. This configuration also contributes to reducing the exit angle from the display element.

[0096] As a result, in this embodiment as well, chromatic aberration, field curvature, and astigmatism (astigmatic difference) can be reduced satisfactorily, as shown in FIG. 7(B), while ensuring sufficient freedom in selecting the resin material.

[0097] In this embodiment, as in the first embodiment, the transmission-reflection optical system 2200 has a cemented surface where the second lens 2201 and the third lens 2202 are cemented together with the first quarter-wave plate B sandwiched therebetween, thereby reducing chromatic aberration.

[0098] In this embodiment, the focal length f1 of the third lens 2202 having positive axial power and the focal length f2 of the lens having negative axial power are f1=90.1mm f2=-186.9mm Therefore, 0.25≦|f2 / f1|=2.07≦4.00 This satisfies the condition of formula (2), making it possible to reduce sensitivity to imaging performance due to manufacturing errors, placement errors, and the like other than chromatic aberration.

[0099] Also in this embodiment, similarly to Example 1, by cementing the second lens 2201 and the third lens 2202 with the first quarter-wave plate B sandwiched therebetween, it is possible to allow for the surface roughness standard of the first quarter-wave plate B. Furthermore, it is not necessary to provide an anti-reflection coating on the first quarter-wave plate B, and the first quarter-wave plate B can be manufactured separately from the transmissive / reflective member.

[0100] In this embodiment, the bonding surfaces are flat. This makes it easier to manufacture the second lens 2201 and the third lens 2202 compared to when they are spherical as in Example 1. Furthermore, since there is no need to bend the first quarter-wave plate B sandwiched between the second lens 2201 and the third lens 2202, it is easier to bond the second lens 2201 and the third lens 2202 with the first quarter-wave plate B sandwiched between them.

[0101] The thicknesses d211, d221, d222, and d231 on the optical axis of the first lens 2101, second lens 2201, third lens 2202, and fourth lens 2301 of the display optical system 2000 of this embodiment, and their sum d2sum, are as follows:

[0102] d211=5.0mm d221=1.9mm d222=7.2mm d231=4mm d2sum=18.1mm The total sum d2sum is 20 mm or less, which reduces the weight of the display optical system 200.

[0103] In this embodiment, there is an air gap between the third lens 2202 and the transmission-reflection film C. That is, the transmission-reflection optical system 2200 sandwiched between the first transmission-reflection surface and the second transmission-reflection surface includes an air gap. This allows the weight of the display optical system 2000 to be reduced.

[0104] Furthermore, by making the display optical system 2000 smaller (thinner), the components that support the display optical system 2000 can be made smaller, and the weight of the HMD can be further reduced. In this embodiment, too, it is effective to make the axial powers of both the pupil-plane-side optical system 2100 and the panel-side optical system 2300 positive. In terms of imaging performance, the axial power of the transmission-reflection optical system 2200 is positive. As a result, the axial powers of all three optical systems 2100, 2200, and 2300 are positive, which makes it easier to shorten the focal length of the display optical system 2000 compared to when the axial power of at least one of the pupil-plane-side optical system 2100 and the panel-side optical system 2300 is negative.

[0105] In this embodiment, the focal length of the pupil-side optical system 2100 is 218.2 mm, and the focal length of the panel-side optical system 2300 is 150.2 mm, both of which are positive. Therefore, similar to the first embodiment, the display optical system 2000 can be made thinner.

[0106] In this embodiment, the R1 surface of the first lens 2101, which serves as the pupil-facing surface, has a convex shape facing the pupil plane. This allows the display optical system 200 to be made smaller in the radial direction, similar to the first embodiment.

[0107] Also in this embodiment, similarly to the first embodiment, a total of four optical elements are provided, including one lens in the pupil plane side optical system 2100, two lenses in the transmission / reflection optical system 2200, and one lens in the panel side optical system 2300. This is preferable not only from the viewpoint of reducing the thickness and weight of the display optical system 2000, but also from the viewpoint of ease of manufacture.

[0108] Also in this embodiment, similar to the first embodiment, the shape of the R2 surface of the second lens 2101, which is imitated by the first transmission-reflection surface (polarization-selective transmission-reflection element A), is aspherical, thereby effectively reducing the field curvature and astigmatic difference.

[0109] In this embodiment, the first lens 2101 and the second lens 2201, which are refractive elements, are cemented together with a first transmissive-reflective member (polarization-selective transmissive-reflective element A) including a first transmissive-reflective surface sandwiched therebetween. This configuration reduces the refractive power of the first transmissive-reflective surface compared to when the first transmissive-reflective surface is in contact with air. As a result, when determining the shape of the first transmissive-reflective surface, it is sufficient to mainly consider the influence of the reflective power, thereby increasing the degree of freedom in optical design. This allows for improved imaging performance while reducing the output angle β. This is particularly effective in reducing field curvature and astigmatic difference in the display optical system 2000 with a wide viewing angle. Furthermore, cementing the first lens 2101 and the second lens 2201 improves the relative positional accuracy of these lenses, thereby improving ease of manufacturing.

[0110] Also in this embodiment, a maximum half angle of 50° is assumed as the nominal design viewing angle, as in Example 1. Specifically, the maximum angle of the chief ray of the display light passing through the pupil plane SP is set to 50°, thereby realizing a display optical system 2000 with a wide viewing angle.

[0111] FIG. 8 shows the angle of emergence β of the chief ray from the display element relative to the angle of view α of the display optical system 2000. From FIG. 8, it can be seen that the angle of emergence β at the maximum half angle of view is −15.0°, and the maximum absolute value of the angle of emergence β is less than 30°. This reduces unevenness in the amount of light. Furthermore, because the angle of emergence β at the maximum half angle of view is negative, the size of the display element can be reduced.

[0112] 9(A) and 9(B) respectively show by solid lines the cross-sectional shape including the optical axis of the R1 surface of the first lens 2101 and the cross-sectional shape including the optical axis of the R2 surface of the fourth lens 2301. The R1 surface of the first lens 2101 and the R2 surface of the fourth lens 2301 have cross-sectional shapes that cannot be expressed by conic sections.

[0113] 9(A) further shows the paraxial curvature surface shape of a cross section including the optical axis of surface R1 of first lens 2101 with a dashed line, and the difference from the cross section shape shown with a solid line is shown with a two-dot chain line. Fig. 9(B) further shows the paraxial curvature surface shape of a cross section including the optical axis of surface R2 of fourth lens 2301 with a dashed line, and the difference from the cross section shape shown with a solid line is shown with a two-dot chain line.

[0114] In this embodiment, the sag amount SagA of the cross-sectional shape including the optical axis at the edge of the effective beam area of ​​the R1 surface of the first lens 2101 (maximum effective diameter Φ40 mm) is 0.37 mm, and the sag amount SagR of the paraxial curvature surface shape is 0.20 mm. The asphericity at the edge of the effective beam area is |(SagA-SagR) / SagR| = 85% This becomes:

[0115] The sag amount SagA of the cross-sectional shape including the optical axis at the edge of the effective beam area of ​​the R2 surface of the fourth lens 2301 (maximum effective diameter Φ46 mm) is −7.56 mm, and the sag amount SagR of the paraxial curvature surface shape is −9.34 mm. The asphericity at the edge of the effective beam area is |(SagA-SagR) / SagR| = 19.0% This becomes:

[0116] In this way, by setting the asphericity at the edge of the effective light area to 50% or more, particularly on the R1 surface of the first lens 2101, sufficient effects are obtained, such as reducing the exit angle β and reducing the field curvature and astigmatic difference with high precision for each angle of view. However, even if the asphericity at the edge of the effective light area is less than 30%, the above effects can be obtained to some extent.

[0117] According to the present embodiment described above, the display optical system 2000 can ensure high optical performance and reduce chromatic aberration and weight.

[0118] Numerical Examples 1 and 2 corresponding to Examples 1 and 2, respectively, are shown below. In the surface data, surface number i indicates the ith surface when counted from the pupil surface side. r is the radius of curvature (mm) of the ith surface, and d is the lens thickness or air gap (mm) between the ith and (i+1)th surfaces. d is the value when no adjustment is performed. nd is the refractive index at the d-line of the material of the ith optical element. νd is the Abbe number based on the d-line of the material of the ith optical element. The Abbe number based on the d-line, νd, is given by: νd=(Nd-1) / (NF-NC) It is expressed as:

[0119] An asterisk (*) next to a surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following equation, where x is the displacement in the optical axis direction at a position of height h from the optical axis relative to the vertex of the surface, R is the paraxial radius of curvature, k is the conic constant, and Ai (i = 4, 6, 8, 10, ...) are the aspherical coefficients of each order.

[0120]

number

[0121] In addition, "e±XX" in the conic constant and aspherical coefficient is "×10± XX " means.

[0122] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1 (Aperture) ∞ (Variable) 2* 1000.000 5.40 1.54390 56.0 3* -106.000 0.30 1.52000 50.0 4* -106.000 (variable) 5* -110.000 5.80 1.54390 56.0 6 -37.300 0.30 1.52000 50.0 7 -37.300 1.50 1.64220 22.4 8* -51.900 -1.50 9 -37.300 -0.30 1.52000 50.0 10 -37.300 -5.80 1.54390 56.0 11* -110.000 (variable) 12* -106.000 (variable) 13* -110.000 5.80 1.54390 56.0 14 -37.300 0.30 1.52000 50.0 15 -37.300 1.50 1.64220 22.4 16* -51.900 6.70 1.49171 57.4 17* -27.600 2.61 18 ∞ 0.30 1.52000 50.0 19 ∞ 0.10 1.52000 50.0 20 ∞ 0.40 1.51633 64.1 Image plane ∞ Aspheric data 2nd side K = 0.00000e+00 A 4= 8.07611e-06 A 6=-1.15573e-08 A 8= 8.41102e-12 3rd page K = 2.90000e+00 Side 4 K = 2.90000e+00 5th page K = 1.88000e+01 Side 8 K =-7.00000e-01 Page 11 K = 1.88000e+01 Side 12 K = 2.90000e+00 Page 13 K = 1.88000e+01 Page 16 K =-7.00000e-01 Page 17 K = 0.00000e+00 A 4= 2.44265e-06 A 6= 1.09841e-08 A 8=-8.88768e-12 Without diopter adjustment - With 4D adjustment Focal length 23.09 22.83 d 1 12.00 12.63 d 4 1.75 1.12 d11 -1.75 -1.12 d12 1.75 1.12 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1 (Aperture) ∞ 12.00 2* 1000.000 5.00 1.49171 57.4 3* -120.000 0.30 1.52000 50.0 4* -120.000 1.90 1.64220 22.4 5 ∞ 0.30 1.52000 50.0 6 ∞ 7.20 1.54390 56.0 7 -49.000 2.09 8* -53.000 -2.09 9 -49.000 -7.20 1.54390 56.0 10 ∞ -0.30 -1.52000 50.0 11 ∞ -1.90 1.64220 22.4 12* -120.000 1.90 13 ∞ 0.30 1.52000 50.0 14 ∞ 7.20 1.54390 56.0 15 -49.000 2.09 16* -53.000 0.00 17* -53.000 4.00 1.54390 56.0 18* -33.000 0.82 19 ∞ 0.30 1.52000 50.0 20 ∞ 0.10 1.52000 50.0 21 ∞ 0.40 1.51633 64.1 Image plane ∞ Aspheric data 2nd side K = 0.00000e+00 A 4= 4.69747e-06 A 6=-1.04348e-08 A 8= 3.20166e-12 3rd page K = 0.00000e+00 A 4= 6.53685e-07 A 6=-1.98380e-09 A 8= 1.52535e-12 Side 4 K = 0.00000e+00 A 4= 6.53685e-07 A 6=-1.98380e-09 A 8= 1.52535e-12 Side 8 K =-1.20000e+00 Side 12 K = 0.00000e+00 A 4= 6.53685e-07 A 6=-1.98380e-09 A 8= 1.52535e-12 Page 16 K =-1.20000e+00 Page 17 K =-1.20000e+00 Side 18 K = 0.00000e+00 A 4= 7.23521e-06 A 6=-3.73503e-09 A 8= 3.90389e-12 Focal length 22.27 [Display device] 10 shows a head mounted display (HMD) 1 as a display device using the display optical systems of Examples 1 and 2. The HMD 1 is worn on the head (in front of the eyes) of a viewer by means of a wearing gear (not shown).

[0123] The HMD1 has display elements RID and LID for the right and left eyes, a right-eye display optical system ROS that guides display light from the right-eye display element RID to the observer's right eye, and a left-eye display optical system LOS that guides display light from the left-eye display element LID to the observer's left eye.

[0124] By using the display optical systems shown in the first and second embodiments as the right-eye and left-eye display optical systems ROS and LOS, it is possible to realize an HMD that allows the viewer to view good images.

[0125] The above embodiment includes the following configurations.

[0126] (Configuration 1) A display optical system that guides display light from a display surface of a display element to a pupil plane, the optical system includes a first optical system, a first transmission-reflection surface, a second optical system, a second transmission-reflection surface, and a third optical system, which are arranged in this order from the pupil plane side to the display surface side; the second optical system includes a lens having positive axial power and a lens having negative axial power and an Abbe number based on the d-line different from that of the lens having positive axial power, At least one of the first optical system and the third optical system has a curved surface that forms an interface with air, a display optical system, wherein the Abbe number of the lens having positive axial power with respect to the d-line is greater than the Abbe number of the lens having negative axial power with respect to the d-line; (Configuration 2) When the Abbe number of the lens having positive axial power with respect to the d-line is ν1 and the Abbe number of the lens having negative axial power with respect to the d-line is ν2, 20≦ν1-ν2 2. The display optical system according to configuration 1, wherein the following condition is satisfied: (Configuration 3) 3. The display optical system according to configuration 1 or 2, wherein the curved surface is an aspherical surface. (Configuration 4) 4. The display optical system according to configuration 3, wherein the first optical system and the third optical system each have the aspherical surface. (Configuration 5) 5. The display optical system according to any one of configurations 1 to 4, wherein the lens having positive axial power and the lens having negative axial power are cemented together. (Configuration 6) The display optical system according to configuration 5, wherein the lens having positive axial power and the lens having negative axial power are cemented together with a wave plate sandwiched therebetween. (Configuration 7) 7. The display optical system according to configuration 5 or 6, wherein the cemented surface between the lens having positive axial power and the lens having negative axial power is a flat surface or a spherical surface. (Configuration 8) When the focal length of the lens having the positive axial power is f1 and the focal length of the lens having the negative axial power is f2, 0.25≦|f2 / f1|≦4.00 8. The display optical system according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) 9. The display optical system according to any one of configurations 1 to 8, wherein the second optical system has an air gap between it and the first transmission-reflection surface or the second transmission-reflection surface. (Configuration 10) 10. The display optical system according to configuration 9, wherein focus adjustment is performed by changing the air gap. (Configuration 11) 11. The display optical system according to any one of configurations 1 to 10, wherein the sum of the thicknesses of all lenses included in the display optical system on the optical axis is 20 mm or less. (Configuration 12) 12. The display optical system according to any one of configurations 1 to 11, wherein at least one of the lens having positive axial power and the lens having negative axial power is a resin lens. (Configuration 13) 13. The display optical system according to any one of configurations 1 to 12, wherein the on-axis power of the first optical system and the on-axis power of the third optical system are both positive. (Configuration 14) 14. The display optical system according to any one of configurations 1 to 13, wherein the optical surface in the first optical system that faces the pupil plane is a plane or a surface that has a convex shape facing the pupil plane side. (Configuration 15) The display optical system according to configuration 3, wherein the cross-sectional shape of the aspherical surface of at least one of the first optical system and the third optical system is a shape other than a conic section. (Configuration 16) When the sag amount of the paraxial curvature surface shape at the edge of the effective light beam area of ​​the aspherical surface is SagR and the sag amount of the cross-sectional shape of the aspherical surface is SagA, 0.3 ≤ |(SagA-SagR) / SagR| 16. The display optical system according to configuration 15, wherein the following condition is satisfied: (Configuration 17) the first optical system has a first lens, the second optical system has a second lens and a third lens, the third optical system has a fourth lens, 17. The display optical system according to any one of configurations 1 to 16, wherein one of the second lens and the third lens is a lens having the positive axial power, and the other is a lens having the negative axial power. (Configuration 18) 18. The display optical system according to any one of configurations 1 to 17, wherein the first transmission-reflection surface and the second transmission-reflection surface both have a concave shape facing the pupil plane side. (Configuration 19) The display optical system described in any one of configurations 1 to 18, characterized in that the lens of the second optical system closest to the display surface and the lens of the third optical system closest to the pupil plane are cemented to each other with the second transmitting and reflecting surface in between. (Configuration 20) A display optical system described in any one of configurations 1 to 19, characterized in that the lens of the first optical system closest to the display surface and the lens of the second optical system closest to the pupil plane are cemented to each other with the first transmitting and reflecting surface in between. (Configuration 21) a maximum half angle of view formed by a chief ray of the display light passing through the pupil plane is 30° or more; 21. The display optical system according to any one of configurations 1 to 20, wherein the angle of emergence of the chief ray from the display element is 35° or less. (Configuration 22) 22. The display optical system according to any one of configurations 1 to 21, wherein the exit angle of the chief ray is an angle directed away from the optical axis of the display optical system. (Configuration 23) 23. The display optical system according to any one of configurations 1 to 22, wherein the display light is guided to the pupil plane after being transmitted through the second transmission-reflection surface, reflected through the first transmission-reflection surface, reflected through the second transmission-reflection surface, and transmitted through the first transmission-reflection surface. (Configuration 24) A display device comprising the display optical system according to any one of configurations 1 to 23.

[0127] The embodiments described above are merely representative examples, and various modifications and alterations are possible to each embodiment when implementing the present invention. [Explanation of symbols]

[0128] 1000,2000 Display optical system 1400,2400 Panel section 1100,2100 1200,2200 1300,2300 A. Polarization-selective transmission / reflection element C Transmissive reflective film SP pupil plane

Claims

1. A display optical system that guides display light from a display surface of a display element to a pupil plane, the optical system includes a first optical system, a first transmission-reflection surface, a second optical system, a second transmission-reflection surface, and a third optical system, which are arranged in this order from the pupil plane side to the display surface side; the second optical system includes a lens having positive axial power and a lens having negative axial power and an Abbe number based on the d-line different from that of the lens having positive axial power, At least one of the first optical system and the third optical system has a curved surface that forms an interface with air, The display optical system is characterized in that the Abbe number of the lens having positive axial power with respect to the d-line is larger than the Abbe number of the lens having negative axial power with respect to the d-line.

2. When the Abbe number of the lens having positive axial power with respect to the d-line is ν1 and the Abbe number of the lens having negative axial power with respect to the d-line is ν2, 20≦ν1−ν2 2. The display optical system according to claim 1, wherein the following condition is satisfied:

3. 2. The display optical system according to claim 1, wherein the curved surface is an aspherical surface.

4. 4. The display optical system according to claim 3, wherein each of the first optical system and the third optical system has the aspherical surface.

5. 2. The display optical system according to claim 1, wherein the lens having positive axial power and the lens having negative axial power are cemented together.

6. 6. The display optical system according to claim 5, wherein the lens having positive axial power and the lens having negative axial power are cemented together with a wave plate sandwiched therebetween.

7. 6. The display optical system according to claim 5, wherein the cemented surface between the lens having positive axial power and the lens having negative axial power is a flat or spherical surface.

8. When the focal length of the lens having the positive axial power is f1 and the focal length of the lens having the negative axial power is f2, 0.25≦|f2 / f1|≦4.00 2. The display optical system according to claim 1, wherein the following condition is satisfied:

9. 2. The display optical system according to claim 1, wherein the second optical system has an air gap between the first transmissive-reflective surface or the second transmissive-reflective surface.

10. 10. The display optical system according to claim 9, wherein focus adjustment is performed by changing the air gap.

11. 2. The display optical system according to claim 1, wherein the sum of the thicknesses of all lenses included in the display optical system on the optical axis is 20 mm or less.

12. 2. The display optical system according to claim 1, wherein at least one of the lens having positive axial power and the lens having negative axial power is a resin lens.

13. 2. The display optical system according to claim 1, wherein the on-axis power of the first optical system and the on-axis power of the third optical system are both positive.

14. 2. The display optical system according to claim 1, wherein an optical surface of the first optical system facing the pupil plane is a flat surface or a surface having a convex shape facing the pupil plane side.

15. 5. The display optical system according to claim 4, wherein the cross-sectional shape of the aspherical surface of at least one of the first optical system and the third optical system is not a conic section.

16. When the sag amount of the paraxial curvature surface shape at the edge of the effective light beam area of ​​the aspherical surface is SagR and the sag amount of the cross-sectional shape of the aspherical surface is SagA, 0.3≦|(SagA−SagR) / SagR| 16. The display optical system according to claim 15, wherein the following condition is satisfied:

17. the first optical system has a first lens, the second optical system includes a second lens and a third lens; the third optical system has a fourth lens, 2. The display optical system according to claim 1, wherein one of the second lens and the third lens is a lens having the positive axial power, and the other is a lens having the negative axial power.

18. 2. The display optical system according to claim 1, wherein both the first transmissive-reflective surface and the second transmissive-reflective surface have a concave shape facing the pupil plane side.

19. 2. The display optical system according to claim 1, wherein the lens of the second optical system closest to the display surface and the lens of the third optical system closest to the pupil plane are cemented together with the second transmissive-reflective surface in between.

20. 2. The display optical system according to claim 1, wherein the lens of the first optical system closest to the display surface and the lens of the second optical system closest to the pupil plane are cemented together with the first transmissive-reflective surface in between.

21. a maximum half angle of view formed by a chief ray of the display light passing through the pupil plane is 30° or more; 2. The display optical system according to claim 1, wherein the angle of emergence of the chief ray from the display element is 35 degrees or less.

22. 2. The display optical system according to claim 1, wherein the exit angle of the chief ray is an angle directed away from the optical axis of the display optical system.

23. 2. The display optical system according to claim 1, wherein the display light is guided to the pupil plane after being transmitted through the second transmission-reflection surface, reflected by the first transmission-reflection surface, reflected by the second transmission-reflection surface, and transmitted through the first transmission-reflection surface.

24. A display device comprising the display optical system according to any one of claims 1 to 23.

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