Virtual image display device

Abstract

This virtual image display device comprises: a plurality of image forming elements which include a first image forming element that outputs a first image to a front region in a viewer's field of view, and a second image forming element that outputs a second image different from the first image to a peripheral region in the viewer's field of view, and which outputs a plurality of images including the first and second images such that at least part of an image region of each thereof overlaps with the first image; and a plurality of eyepiece optical systems which are provided to respectively correspond to the plurality of image forming elements and form one virtual image as a whole from the plurality of images. A lens surface located closest to the viewer's eye side is a lens surface shared among the respective eyepiece optical systems, a lens surface facing the lens surface and located second from the viewer's eye side is designed as a Fresnel lens surface, and a lens located closest to the viewer's eye side is integrally molded.

Description

Virtual image display device

[0001] The present disclosure relates to a virtual image display device, and more particularly to a head-mounted virtual image display device.

[0002] For example, virtual image display devices worn on the observer's head are required to have both high resolution and a wide viewing angle to enhance the sense of immersion. At the same time, the device worn by the observer must be small and lightweight to ensure a comfortable fit.

[0003] Generally, when an image-forming element with a finite number of pixels is observed through an eyepiece optical system, the number of pixels per angle is determined depending on the viewing angle, so there is a trade-off between resolution and viewing angle. In order to overcome this trade-off and achieve a compact and lightweight device, various techniques have been reported that use multiple image-forming elements and eyepiece optical systems to stitch together images into a single virtual image for observation (see Patent Documents 1 to 4 and Non-Patent Documents 1 and 2).

[0004] JP 2018-5221 A JP 2016-541031 A JP 2019-74678 A JP 2018-17942 A

[0005] Philipp Wartenberg et al.,High Frame-Rate 1" WUXGA OLED Microdisplay and Advanced Free-Form Optics for Ultra-Compact VR Headsets,SID 2018 DIGEST,pp.514-517Kiseung Bang et al.,Lenslet VR: Thin,Flat and Wide-FOV Virtual Reality Display Using Fresnel Lens and Lenslet Array,IEEE Transactions on Visualization and Computer Graphics,pp.2545-2554,2021

[0006] In a head-mounted virtual image display device that uses multiple image-forming elements and eyepiece optical systems to stitch together a single virtual image for viewing, while achieving both high resolution and a high viewing angle, if a physical boundary between adjacent eyepiece optical systems is formed on the lens surface closest to the observer's eye, there are issues with reduced design and ease of cleaning. Furthermore, if there is a step at the boundary, light hitting the side becomes loss or stray light, which creates a design constraint that requires the ridgelines determined by the curvature of each lens surface to coincide.

[0007] It is desirable to provide a head-mounted virtual image display device that allows the viewer to feel comfortable and immersed by increasing the degree of freedom in the design and arrangement of multiple eyepiece optical systems.

[0008] One aspect of the present disclosure aims to achieve both a comfortable fit and a sense of immersion.

[0009] A virtual image display device according to one aspect of the present disclosure includes a first image forming element that outputs a first image in a frontal region in the viewer's field of view, and a second image forming element that outputs a second image different from the first image in a peripheral region in the viewer's field of view, and includes a plurality of image forming elements that output a plurality of images including the first and second images such that at least a portion of each image region overlaps with the first image, and a plurality of eyepiece optical systems that are provided corresponding to the plurality of image forming elements and form a single virtual image as a whole from the plurality of images, wherein in the plurality of eyepiece optical systems, the lens surface that is closest to the viewer's eye is a lens surface shared by the respective eyepiece optical systems, and further, the lens surface that is second from the viewer's eye opposite the lens surface is designed as a Fresnel lens surface, and the lens that is closest to the viewer's eye is molded as a single unit.

[0010] 1 is a diagram showing an example of a schematic configuration of a virtual image display device 1E according to a comparative example. A diagram showing an example of a design of a boundary portion 31 in the comparative example. A diagram showing the design concept leading to the embodiment. A diagram showing an example of a schematic configuration of a virtual image display device 1 according to the first embodiment. A perspective view showing the S2 lens surface of the L1 lens. A diagram showing an example of a design of a virtual image surface. A diagram showing an example of a region of an angle of view displayed by an optical unit 10. A diagram showing an example of a schematic configuration of a virtual image display device 1 according to a second embodiment. A diagram showing an example of a schematic configuration of a virtual image display device 1 according to the second embodiment. A perspective view showing the S2 lens surface of the L1 lens. A diagram showing an example of a region of an angle of view displayed by an optical unit 10. A diagram showing an example of a schematic configuration of a virtual image display device 1 according to a third embodiment. A diagram showing an example of a schematic configuration of a virtual image display device according to a fourth embodiment. A diagram showing an example of a schematic configuration of a virtual image display device according to a fifth embodiment. A diagram showing an example of a gaze direction detection.

[0011] 0. Introduction For example, a technique using two image forming elements per eye is known in order to widen the viewing angle while suppressing increases in the size and weight of a virtual image display device (see, for example, Patent Document 1).

[0012] On the other hand, in order to widen the field of view while maintaining high resolution, a technology is also known that realizes a compact optical design by observing one image-forming element per eye through an eyepiece optical system divided into multiple small lenses including free-form surfaces (see, for example, Patent Document 2).

[0013] Furthermore, in order to widen the field of view while maintaining high resolution, a technology is also known in which two small, high-definition image-forming elements per eye are observed through two eyepiece optical systems including free-form surfaces, thereby achieving a compact optical design (see, for example, Non-Patent Document 1).

[0014] In the above technology, all lens surfaces, from the S1 lens surface (the definition of the S1 lens surface will be described later) located closest to the viewer's eye to the lens surface located closest to the image-forming element, are divided to correspond to each of the adjacent eyepiece optical systems. Because light that crosses the boundary between adjacent eyepiece optical systems and enters the viewer's pupil becomes stray light, at least the S1 lens surface needs to have a strong positive refractive power near the boundary, resulting in a large curvature of the lens surface. In this case, ridges are formed on the appearance surface, which poses issues of reduced design and ease of cleaning. Furthermore, if there is a step at the boundary, light that strikes the side becomes a loss or stray light, resulting in a strong design constraint of having to match the ridges determined by the curvature of each lens surface.

[0015] On the other hand, in order to prevent degradation of image quality or loss of image near the boundary between multiple eyepiece optical systems, a technology is known that improves image quality by making the S1 lens surface, which is located closest to the observer's eye, a common curved surface expressed by a single curvature (see, for example, Patent Document 3).

[0016] Furthermore, Patent Document 4 discloses a technology in which a third eyepiece optical system is provided between a first eyepiece optical system for the left eye and a second eyepiece optical system for the right eye in order to widen the inner field of view for each eye, thereby avoiding interference between the eyepiece optical systems for the left and right eyes and ensuring the necessary eye relief. In the technology described in Patent Document 4, the S1 lens surface located closest to the viewer's eye is formed as a lens surface common to the three eyepiece optical systems in order to present a defect-free, naturally continuous observation image.

[0017] In the technologies described in Patent Documents 3 and 4, the S1 lens surface, which is located closest to the viewer's eye, is made a common lens surface for multiple eyepiece optical systems, thereby ensuring aesthetic appeal and ease of cleaning. However, because light that crosses the boundary between adjacent eyepiece optical systems and enters the viewer's pupil becomes stray light, the S2 lens surface, which is located second from the viewer's eye and opposite the S1 lens surface, needs to have a strong positive refractive power near the boundary, resulting in a large curvature for the S2 lens surface. In this case, a ridgeline is formed on the S2 lens surface, but if there is a step at the boundary, light that strikes the side surface will become loss or stray light, so the strong design constraint of having the ridgelines determined by the curvatures of the respective lens surfaces coincide still exists.

[0018] On the other hand, Non-Patent Document 2 discloses a technology that realizes an extremely low-profile, compact optical design by forming the L1 lens, which is located closest to the viewer's eye, as a single convex Fresnel lens shared by multiple eyepiece optical systems, and the L2 lens, which is located second from the viewer's eye, as an array of convex Fresnel lenses that are divided corresponding to each of the multiple eyepiece optical systems, and by folding back the optical path using a reflective polarizer. Because the L2 lens is formed by arranging Fresnel lenses, there is no step at the boundary between adjacent eyepiece optical systems, but because the L1 lens is a single lens, it is not easy to achieve a field of view of more than 120°.

[0019] Furthermore, in the technologies described in Patent Document 2 and Non-Patent Document 2, a single image-forming element is shared by multiple eyepiece optical systems, and an image-forming device of several inches is required to achieve a wide viewing angle. In recent years, development of high-pixel-density liquid crystal displays and OLED (organic light-emitting diode) displays has progressed as image-forming devices of several inches, but the angular resolution of the virtual image observed using either of these is 10 to 20 ppd. This falls short of the angular resolution of the human eye, which is 30 to 60 ppd, making it difficult to achieve a sufficient sense of immersion.

[0020] At least some of the above problems are addressed by the disclosed technology.

[0021] 1. Embodiments Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, the same elements are designated by the same reference numerals, and redundant description will be omitted.

[0022] Unless otherwise specified, the lens name refers to the Nth lens counting from the viewer's (which can also be called the user's) eye side as the LN lens. For example, the lens closest to the viewer's eye side is the L1 lens. Furthermore, the lens surface of each lens that faces the viewer's eye side is referred to as the S1 lens surface, and the lens surface facing the image-forming element side (the side opposite the S1 lens surface) is referred to as the S2 lens surface. A single lens may refer to one (single) lens, or may refer to a group of lenses formed by bonding multiple lenses together.

[0023] 1.0 Overview A virtual image display device (e.g., a head-mounted virtual image display device) according to an embodiment of the present disclosure includes an image forming element that outputs multiple images, and multiple eyepiece optical systems that are provided corresponding to the multiple image forming elements and that form a single virtual image as a whole from the multiple images. The multiple image forming elements include a high-definition, compact first image forming element that displays an image to be output in a front region in the viewer's field of view, and second to Nth image forming elements (N is an integer greater than or equal to 3) that have a lower resolution than the first image forming element and display an image to be output in a peripheral region in the viewer's field of view. The multiple eyepiece optical systems include a first eyepiece optical system provided corresponding to the first image forming element, and second to Nth eyepiece optical systems (other eyepiece optical systems). Each of the second to Nth eyepiece optical systems may be designed differently from the first eyepiece optical system. Examples of different designs include designs with different resolutions and different angles of view. A virtual image display device according to one embodiment is characterized in that a first image displayed by a first image forming element is not a subset of any of the second to Nth images displayed by the second to Nth image forming elements. At least a portion of the image area of ​​each of the images output by the first to Nth image forming elements may overlap with each other. A head-mounted virtual image display device according to one embodiment is configured so that an observer can observe the first to Nth images displayed by the first to Nth image forming elements in a state in which the images are stitched together into a single virtual image via first to Nth eyepiece optical systems that are respectively suited to the first to Nth images.

[0024] 1 is a diagram showing an example of a schematic configuration of a virtual image display device 1E according to a comparative example. The virtual image display device 1E is used by being worn on the head of a viewer U, for example. Among the components included in the virtual image display device 1E, an optical unit 10E corresponding to the right eye 40R of the viewer U is shown as an example.

[0025] The components of the optical unit 10E are illustrated by reference numerals, including the image-forming element 11, the image-forming element 12, the eyepiece optical system 21E, and the eyepiece optical system 22E. A schematic optical path is also illustrated, in which a bundle of rays passing near the boundary surface 30 of the eyepiece optical system 21E and the eyepiece optical system 22E is traced back from the right eye 40R side.

[0026] The eyepiece optical system 21E is located between the image forming element 11 and the right eye 40R of the observer U, and outputs a virtual image in the front region in the field of view of the observer U. The eyepiece optical system 22E is located between the image forming element 12 and the right eye 40R of the observer U, and outputs a virtual image in the peripheral region in the field of view of the observer U.

[0027] In this example, the eyepiece optical system 21E includes a lens L11E, a lens L12E, and a lens L13E, which are located in this order between the right eye 40R and the image forming element 11. The eyepiece optical system 22E includes a lens L21E, a lens L22E, and a lens L23E, which are located in this order between the right eye 40R and the image forming element 12. A partially enlarged view of a boundary 31 between the lens L11E and the lens L21E is also shown on the right side of Figure 1.

[0028] Of the lenses, the lens located closest to the right eye 40R is the L1 lens. In this example, the lenses L11E and L21E correspond to the L1 lens.

[0029] A ray traced from the right eye 40R is split into a ray bundle R11 that passes through the eyepiece optical system 21E and a ray bundle R21 that passes through the eyepiece optical system 22E. The ray bundle RE1 that intersects with the boundary surface 30 after being refracted by the lens surfaces of the L1 lens (lenses L11E and L21E) becomes stray light and is lost. A reduction in the amount of light occurs due to vignetting of the ray bundle, and the image at the splice position becomes dark. An example of a design for suppressing vignetting of the ray bundle in a comparative example will be described with reference to FIG. 2.

[0030] 2 is a diagram showing an example of the design of boundary portion 31 in a comparative example. Lenses L11E and L21E are designed to suppress the above-mentioned vignetting of the light beam. The S1 lens surface and S2 lens surface of lens L11E are illustrated and referred to as lens surface S11E and lens surface S12E. The S1 lens surface and S2 lens surface of lens L21E are illustrated and referred to as lens surface S21E and lens surface S22E.

[0031] 2A, the lenses L11E and L21E are designed so that the light beams R11 and R21 after being refracted at the lens surfaces S11E and S21E do not intersect with the boundary surface 30. The lens surfaces S11E and S21E are given strong positive refractive power.

[0032] 2B, the lenses L11E and L21E are designed so that the bundles of rays R11 and R21, after being refracted by the lens surfaces S21E and S22E, do not intersect with the boundary surface 30. The lens surfaces S12E and S22E are given strong positive refractive power. In this case, the lens surfaces S11E and S21E are shared by the eyepiece optical systems 21E and 22E as lens surfaces expressed by a single design formula, and the starting position of the boundary surface 30 between them is shifted from the lens surfaces S11E and S21E to the lens surfaces S12E and S22E (from the S1 lens surface to the S2 lens surface).

[0033] FIG. 3 is a diagram illustrating the design concept leading to the embodiment. FIG. 3A shows a schematic configuration of the L1 lens portion (the portion of lenses L11E and L21E) of the optical unit 10E of the comparative example, corresponding to FIG. 2A described above. Because the curvatures of lens surfaces S11E and S21E are large, the ridges formed at boundary portion 31 (see also FIGS. 1 and 2 ) of lens surfaces S11E and S21E, which serve as the appearance surface (the surface observed by observer U), reduce design aesthetics and ease of cleaning. Furthermore, if there is a step at boundary portion 31, the reflected light RE2 and transmitted light RE3 at the side surfaces become losses or stray light, creating a design constraint that requires the ridges determined by the curvatures of lens surfaces S11E and S21E to coincide. In general, to perfectly coincide the ridges, it is necessary to match the curvatures of adjacent lens surfaces and position the boundary surfaces symmetrically, which can be a significant design constraint in lens design.

[0034] 3B shows a schematic configuration of the L1 lens portion of optical unit 10E of the comparative example, which corresponds to FIG. 2B described above. Because the starting position of boundary surface 30 is shifted to lens surfaces S12E and S22E (to the S2 lens surface), the design and cleanability of lens surfaces S11E and S21E, which serve as the appearance surfaces, are ensured. However, if there is a step at boundary portion 31 between lens surfaces S12E and S22E, reflected light RE2 and transmitted light RE3 from the side surfaces will be lost or become stray light. Therefore, the strong design constraint of matching the ridge lines determined by the curvatures of lens surfaces S12E and S22E remains.

[0035] FIG. 3C shows a schematic configuration of the L1 lens portion of the virtual image display device and optical unit according to the embodiment. The virtual image display device and optical unit according to the embodiment are illustrated as a virtual image display device 1 and an optical unit 10. The first and second eyepiece optical systems included in the optical unit 10 are illustrated as eyepiece optical systems 21 and 22. FIG. 3C shows only the L1 lens among the components of the eyepiece optical systems 21 and 22. The L1 lens included in the eyepiece optical system 21 is illustrated as lens L11. The L1 lens included in the eyepiece optical system 22 is illustrated as lens L21. The S1 lens surface and S2 lens surface of the lens L11 are illustrated as lens surface S11 and lens surface S12. The S2 lens surface of the lens L21 is illustrated as lens surface S21 and lens surface S22.

[0036] 2B, their S2 lens surfaces, i.e., lens surfaces S12 and S22, are both designed as Fresnel lens surfaces. In this case, even if the designs of lens surfaces S12 and S22 are different, the ridgelines coincide. This allows for a flexible optical design depending on the characteristics required for each eyepiece optical system, such as prioritizing definition for eyepiece optical system 21, which outputs a virtual image in the front region, and field of view for eyepiece optical system 22, which outputs a virtual image in the peripheral region.

[0037] In the configuration shown in Figure 3C, lens surfaces S11 and S21 are shared by eyepiece optical systems 21E and 22E, and lens surfaces S12 and S22 are the starting points of interface 30. Therefore, light rays traced from the right eye 40R of observer U do not have any optical paths within lenses L11 and L21 that would cause vignetting problems until they reach lens surfaces S12 and S22. However, when individually formed lenses are adhesively fixed, many optical paths intersect at shallow angles (incident angle near 90°) that are nearly parallel to the bonded interface. Even if the refractive index of the adhesive is matched to within one decimal place, Fresnel reflection can increase the reflectivity to nearly 100%. To address this, lenses L11 and L21 are preferably molded as a single unit to avoid any physical bonded interface. Furthermore, when lenses L11 and L21 are formed by adhesive fixation, the relative position accuracy between the individually formed lenses is approximately 100 μm, whereas when they are formed by integral molding, the relative position accuracy between the lens surfaces in each eyepiece optical system is guaranteed by the processing accuracy of the mold, and is therefore improved to the order of 10 μm.

[0038] To abstract and generalize the technical concept of the embodiment, more preferably, the second to Nth eyepiece optical systems provided corresponding to the second to Nth image-forming elements may be designed to include a free-form lens or anamorphic lens that lacks rotational symmetry with respect to the optical axis of the first eyepiece optical system provided corresponding to the first image-forming element, or a decentered lens or lens surface. As a result, in the second to Nth eyepiece optical systems that output a wide-field virtual image in the peripheral field of view, at least the S2 lens surface of the L1 lens has large decentering and tilt, making it possible to design an optical system that efficiently corrects decentering aberrations that occur there.

[0039] More preferably, the S1 lens surface of the L1 lens shared by the multiple eyepiece optical systems may be designed as a gently concave surface expressed by a single design formula. As a result, it becomes possible to design an optical arrangement with a high degree of freedom, such as by taking an optical path that emits light with a wide angle of peripheral vision toward the eyes of the observer U, while ensuring sufficient space in front of the eyes (the space from the face of the observer U to the lens surface closest to the eyes) assuming that the observer will wear glasses while wearing the virtual image display device.

[0040] With this configuration, a high-resolution virtual image is output using a high-definition first image-forming element in the stable fixation field where human visual function is excellent, and a virtual image with relatively low manufacturing costs is output in the peripheral field where information discrimination ability is low. This prevents the virtual image display device 1 from becoming unnecessarily over-specified, and optimizes the balance between resolution and manufacturing costs.

[0041] Furthermore, by adjusting the arrangement and number of the second to Nth image forming elements and the second to Nth eyepiece optical systems according to the viewing angle required for the virtual image display device 1, a wide viewing angle can be realized relatively easily.

[0042] Furthermore, because the first image-forming element disposed in front of the observer U is small and the angle of view of the virtual image is limited to a stable field of view, the corresponding first eyepiece optical system can be designed to be relatively compact. Furthermore, when designing an optical system with a wide field of view, dividing the eyepiece optical system into multiple parts rather than a single one makes it easier to ensure optical performance and allows each eyepiece optical system to be made low-profile, which results in the virtual image display device 1 as a whole being smaller and lighter in weight.

[0043] In one embodiment, the first eyepiece optical system of the virtual image display device 1 may output a virtual image with a horizontal angle of view of 60° to 120° and a vertical angle of view of 40° to 120°. As a result, the virtual image output from the first eyepiece optical system and the virtual images output from the second to Nth eyepiece optical systems are joined in the transition region from the stable fixation field to the peripheral field, thereby avoiding the risk of the image boundaries being visible. Furthermore, this configuration also reduces the risk of the physical boundaries between the first eyepiece optical system and the adjacent second to Nth eyepiece optical systems being visible.

[0044] In one embodiment, for example, the first image-forming element has a resolution of 2000 ppi or more, and the second through Nth image-forming elements have resolutions of less than 2000 ppi. This allows a virtual image to be output with an angular resolution of 30 ppd or more, at least in a stable field of view where human visual function is excellent. As a result, a virtual image equivalent to or better than the angular resolution of the human eye (30 to 60 ppd) can be observed, allowing the observer U to obtain a sufficient sense of resolution.

[0045] In the first to Nth eyepiece optical systems, the third lens surface counting from the eye of observer U, i.e., the S1 lens surface of the L2 lens, may be designed as a Fresnel lens surface in each eyepiece optical system, so that there is no step at the boundary between adjacent eyepiece optical systems. Light rays traced from the eye side are divided into ray bundles that pass through each eyepiece optical system at the boundary at the S2 lens surface of the L1 lens, but if the S1 lens surface of the L2 lens is a Fresnel lens surface, the ray will be refracted by the S2 lens surface of the L1 lens and then by the S1 lens surface of the L2 lens immediately afterwards. In order to suppress vignetting of the ray bundle at the boundary surface, it is sufficient to use two Fresnel lens surfaces and design the ray bundle so that it does not intersect with the boundary surface. As a result, the refractive power required to prevent ray bundles (for example, ray bundles R11 and R21 described above with reference to FIG. 2) from intersecting boundary surface 30 can be dispersed by the two Fresnel lens surfaces formed on the opposing surfaces of the L1 lens and L2 lens, rather than being imparted only to the S2 lens surface of the L1 lens, making it possible to design an optical system with a well-balanced power arrangement.

[0046] More preferably, in each of the first to Nth eyepiece optical systems, the third lens surface counting from the eye of the observer U, i.e., the S1 lens surface of the L2 lens, is designed as a Fresnel lens surface, and the L2 lens is formed as a single unit so as not to have a physical cemented interface. As a result, the relative positional accuracy between the lens surfaces in each eyepiece optical system can be guaranteed by the machining accuracy of the mold, achieving an accuracy on the order of 10 μm.

[0047] The first to Nth eyepiece optical systems are designed so that, while each eyepiece optical system forms a flat virtual image surface, the more peripherally positioned eyepiece optical systems form inclined virtual image surfaces, thereby forming a discretely curved virtual image surface as a whole to cover the viewer U's field of view. Furthermore, the distance (virtual image distance) from the viewer U to the virtual image surface of each of the multiple eyepiece optical systems may be designed to be the same in the direction of observing the boundaries of the images output by adjacent eyepiece optical systems (see Figure 6 described below). Here, if the virtual image surfaces of the peripherally positioned eyepiece optical systems are not inclined, when the viewer U moves his / her gaze toward his / her ear, the single virtual image formed by the multiple eyepiece optical systems as a whole will appear to have a narrower vertical angle of view toward the periphery due to trapezoidal distortion, giving the viewer U the impression that a flat screen is placed in front of him / her, which inhibits immersion. Therefore, with this configuration, the viewer U can experience a visual experience that surrounds him / her, and even when the viewer U moves his / her gaze, the continuous virtual image distance reduces the risk of the viewer U seeing the boundaries of the image, resulting in a high level of immersion.

[0048] In one embodiment, the virtual image display device 1 may further include a sliding mechanism capable of controlling the virtual image distance. The sliding mechanism may be capable of controlling the virtual image distance of each of the first to Nth eyepiece optical systems by sliding the positions of the constituent mechanisms, such as lenses and lens groups, that constitute each of the first to Nth eyepiece optical systems, or the positions of the image forming elements corresponding to each of the eyepiece optical systems.

[0049] Instead of the sliding mechanism, the virtual image display device 1 may include a voltage-driven liquid crystal lens between the observer U and the multiple eyepiece optical systems. By adjusting the voltage applied to the liquid crystal layer to change the refractive index of the liquid crystal and thereby changing the focal length of the lens, it may be possible to control the virtual image distance of a single virtual image formed by the multiple eyepiece optical systems as a whole. As a result, the absence of a sliding mechanism can be expected to provide high-speed control and high reliability.

[0050] For example, the first to Nth eyepiece optical systems are designed so that the virtual image distance can be controlled from 20 mm in front of the observer U to infinity as the distance from the observer U. As a result, the problem of mismatch between the convergence distance and the accommodation distance in conventional virtual image observation devices is resolved, and discomfort such as nausea during observation is reduced.

[0051] In one embodiment, the virtual image display device 1 may detect the line of sight of the observer U and control the virtual image distance from the observer U to the virtual image plane of each of the first to Nth eyepiece optical systems in accordance with the convergence angle of the observer U. This method solves the "problem of mismatch between the convergence distance and the accommodation distance" in conventional virtual image observation devices, reduces discomfort such as nausea during observation, and makes it possible to output a virtual image with a natural sense of depth in conjunction with the position at which the observer U is gazing.

[0052] As more specific embodiments, the first to fifth embodiments will be described in order as examples.

[0053] 1.1 First Embodiment The virtual image display device 1 according to the first embodiment includes an optical unit corresponding to the left eye of the observer U and an optical unit corresponding to the right eye. In the following, the optical unit corresponding to the right eye of the observer U will be taken as an example and will be referred to as the optical unit 10 as before. Unless otherwise specified, the optical unit corresponding to the left eye of the observer U may be understood to have the same configuration as the optical unit 10.

[0054] The optical unit 10 includes a plurality of image forming elements including an image forming element 11 (first image forming element) and an image forming element 12 (second image forming element), and a plurality of eyepiece optical systems including an eyepiece optical system 21 (first eyepiece optical system) and an eyepiece optical system 22 (second eyepiece optical system) corresponding to the image forming element 11 (first image forming element) and the image forming element 12 (second image forming element).

[0055] The image forming elements 11 and 12 are not arranged on the same plane, but are arranged at an appropriate inclination in three-dimensional space (see FIG. 4, etc., which will be described later).

[0056] The image forming element 11 is a high-definition, compact image forming element that displays an image to be output in a front area in the field of view of the observer U. The image forming element 11 has, for example, a pixel pitch of 6.3 μm, a diagonal size of 1.28 inches, and a resolution of 4032 ppi. The image forming element 11 is, for example, an M-OLED (Micro Organic Light Emitting Diode).

[0057] The image forming element 12 is disposed to the right of the image forming element 11 when viewed from the observer U, and displays an image to be output to a peripheral region on the right side of the observer U's visual field. The pixel pitch of the image forming element 12 is larger than that of the image forming element 11, for example, 24.0 μm, and the diagonal size is 2.89 inches. The resolution of the image forming element 12 is, for example, 1058 ppi. The image forming element 12 is, for example, an LTPS (Low Temperature Polycrystalline Silicon)-LCD (Liquid Crystal Display). Note that in the case of the optical unit for the left eye, the image forming element 12 is disposed to the left of the image forming element 11, and displays an image to be output to a peripheral region on the left side of the observer U's visual field.

[0058] Table 1 shows examples of the design (specifications) of the corresponding optical elements (lenses in this example) and image-forming elements for each of the eyepiece optical systems 21 and 22, as well as the field of view range of the virtual images output by each of the eyepiece optical systems 21 and 22.

[0059] In Table 1 above, the center position of the field of view area of ​​the entire image displayed by the optical unit 10 for the left eye and the optical unit 10 for the right eye 40R is set to a horizontal field of view (X field of view) of 0° and a vertical field of view (Y field of view) of 0°. The right side of the horizontal field of view is set to the positive direction, and the left side is set to the negative direction. The upper side of the vertical field of view is set to the positive direction, and the lower side is set to the negative direction. This also applies to the following explanations of other tables and figures.

[0060] As shown in Table 1 above, in the optical unit 10 for the right eye 40R, the field angle range of the virtual image output by the eyepiece optical system 21 is, for example, a horizontal field angle range of -45° to 40° and a vertical field angle range of -38° to 38° when observed in a direction directly facing the virtual image plane. Furthermore, the field angle range of the virtual image output by the eyepiece optical system 22 is, for example, a horizontal field angle range of 5° to 70° and a vertical field angle range of -38° to 38° when observed in a direction directly facing the virtual image plane.

[0061] The configuration of the optical unit for the left eye is basically the same as the configuration of the optical unit 10 for the right eye 40R, and the field of view area of ​​the virtual image divided and output by the eyepiece optical system 21 and the eyepiece optical system 22 included in the optical unit for the left eye is equal to the range obtained by swapping the positive and negative sides of the horizontal field of view (X field of view) in Table 1 above.

[0062] Therefore, the optical units for the left and right eyes overlap in a field angle region of -45° to 45° horizontally and -38° to 38° vertically, and this field angle region is useful for providing depth perception to the observer U through parallax images. Furthermore, any two adjacent images are arranged so as to have an overlap region of at least a field angle of 35° or more, and the direction in which the observer gazes at the boundary between the eyepiece optical systems 21 and 22 due to eye movement is 20° horizontally.

[0063] 4A and 4B are diagrams illustrating an example of a schematic configuration of the virtual image display device 1 according to the first embodiment. The diagram illustrates an example of a cross-sectional configuration (horizontal cross-section) of the optical unit 10 for the right eye 40R when viewed in plan. (B) of FIG. 4 also schematically illustrates several optical paths of light rays passing through the right eye 40R of the observer U and the optical unit 10.

[0064] The eyepiece optical system 21 includes lenses L11, L12, L13, and L14, which are located in this order between the right eye 40R and the image-forming element 11. The eyepiece optical system 22 includes lenses L21 and L22, which are located in this order between the right eye 40R and the image-forming element 12. The S2 lens surface of lens L12 is illustrated as lens surface S14. The S1 and S2 lens surfaces of lens L22 are illustrated as lens surfaces S23 and S24.

[0065] The eyepiece optical systems 21 and 22 are designed to output the field angle regions that are divided and displayed by the corresponding image forming elements 11 and 12. The optical unit 10 for the right eye 40R outputs a virtual image that has a horizontal field angle in the range of −45° to 70° as a whole.

[0066] 4, the lens surface S11 of the lens L11 and the lens surface S21 of the lens L21 are common surfaces shared by the eyepiece optical system 21 and the eyepiece optical system 22 (for example, the lens surface S11 and the lens surface S22 can be collectively referred to as one lens surface S11), and are designed as concave spherical surfaces with a radius of curvature of 1000 mm. As a result, assuming that the observer U wears glasses while wearing the virtual image display device, sufficient space is secured in front of the eyes, an optical path with a wide viewing angle of 70° horizontal angle of view is formed, and the design and cleanability of the lens surfaces S11 and S21, which serve as the appearance surfaces, are ensured.

[0067] 4, the lens surfaces indicated by dashed lines, i.e., lens surface S12 of lens L11, lens surface S22 of lens L21, and lens surface S23 of lens L22, are all designed as Fresnel lens surfaces. In order to reduce light loss and stray light at interface 30, lens surfaces S12 and S22 are given particularly strong positive refractive power, preventing light rays traced from the right eye 40R of observer U from intersecting with interface 30 after being refracted by lens surfaces S12 and S22. Furthermore, lens surface S24 of lens L22 in the eyepiece optical system 22 is a rotationally asymmetric free-form surface, which efficiently corrects decentering aberrations caused by the decentering and tilt of lens surface S22 of lens L21 and lens surface S23 of lens L22.

[0068] 5 is a perspective view showing the S2 lens surface of the L1 lens. The lenses L11 and L21 are integrally formed as a single lens (a single L1 lens) with no physical boundary between them. They can also be collectively referred to as lens L11.

[0069] Lens surface S12 and lens surface S22 are both designed as Fresnel lens surfaces, and even if the designs of the respective lens surfaces are different, no steps are created at the boundaries, so there are no optical paths that result in loss or stray light at the boundaries. Therefore, the eyepiece optical system 21, which outputs a virtual image in the front region of the field of view of the observer U, can be designed with an emphasis on resolution, while the eyepiece optical system 22, which outputs a virtual image in the peripheral region of the field of view of the observer U, can be designed with an emphasis on the viewing angle, and so on. As a result, the virtual image display device 1 as a whole can be made smaller and lighter.

[0070] 6 is a diagram showing an example of a design of a virtual image plane. The virtual image plane observed by the observer U through the eyepiece optical system 21 is shown as a virtual image plane 61. The virtual image plane observed by the observer U through the eyepiece optical system 22 is shown as a virtual image plane 62.

[0071] Both the virtual image planes 61 and 62 are flat surfaces, but the virtual image plane 62 output from the peripheral eyepiece optical system 22 is designed to be tilted horizontally by 15° relative to the virtual image plane 61 output from the eyepiece optical system 21 placed in front, so that the observer U observes discrete virtual image planes that cover the field of view.

[0072] 6 , the virtual image distance of the virtual image plane 61 output from the eyepiece optical system 21 is 2500 mm in the front direction directly facing the virtual image plane 61, and the virtual image distance of the virtual image plane 61 output from the eyepiece optical system 21 is 2500 mm in the front direction directly facing the virtual image plane 61. The virtual image distance of the virtual image plane 62 output from the eyepiece optical system 22 is 2650 mm in the horizontal direction of 15° directly facing the virtual image plane 62. When the virtual image planes 61 and 62 are designed in this arrangement, as described above, the horizontal 20° direction in which the boundary between the eyepiece optical system 21 and the eyepiece optical system 22 is gazed upon by eye movement coincides with the direction in which the boundary position 50 where the respective virtual image planes intersect is gazed upon. As a result, even if the viewer U moves his or her line of sight, the virtual image distance remains continuous, reducing the risk of the viewer U perceiving the boundary between the images.

[0073] The effect obtained by tilting the virtual image plane 62 with respect to the virtual image plane 61 will be described with reference to FIG.

[0074] 7 is a diagram showing an example of the region of the angle of view displayed by the optical unit 10. An image corresponding to the virtual image output by the image forming element 11 and the eyepiece optical system 21 is shown as image 11R (first image). An image corresponding to the virtual image output by the image forming element 12 and the eyepiece optical system 22 is shown as image 12R (second image). Parts of the images 11R and 12R may overlap each other.

[0075] 7A shows the range of the angle of view observed when observer U is looking at gaze point 70 in front (when the gaze direction is directly facing virtual image plane 61). In this case, image 11R is observed as a rectangle, but because the gaze direction is tilted by 15° horizontally with respect to virtual image plane 62, the vertical angle of view of image 12R increases to a maximum of ±53° as it moves toward the ear due to trapezoidal distortion.

[0076] 7B shows the range of the angle of view observed when the observer U is looking at the gaze point 71 at 15° in the horizontal direction (when the gaze direction is directly facing the virtual image surface 62). Only by moving the line of sight to 15° in the horizontal direction can the image 12R be observed as a rectangular image. Here, if the virtual image surface 62 is not tilted, the vertical angle of view appears narrower toward the periphery due to keystone distortion, which inhibits the sense of immersion. However, according to this embodiment, the observer U can obtain a high sense of immersion by experiencing a video that seems to surround him / her.

[0077] While the design of the virtual image plane in the horizontal direction has been described using Figures 6 and 7, if multiple eyepiece optical systems are provided in the vertical direction, a similar design is possible for the vertical direction.

[0078] As described above, the virtual image display device 1 according to the first embodiment is relatively small and lightweight, and achieves both high definition and a wide viewing angle while keeping manufacturing costs down, thereby providing the observer U with a comfortable fit and a sense of immersion.

[0079] 1.2 Second embodiment In the virtual image display device 1 according to the second embodiment, the optical unit for the left eye and the optical unit 10 for the right eye 40R each include a plurality of image forming elements including an image forming element 11 (first image forming element), an image forming element 12 (second image forming element), an image forming element 13 (third image forming element), and an image forming element 14 (fourth image forming element), and a plurality of ocular optical systems including an ocular optical system 21 (first ocular optical system), an ocular optical system 22 (second ocular optical system), an ocular optical system 23 (third ocular optical system), and an ocular optical system 24 (fourth ocular optical system) corresponding to the image forming elements (see Figures 8 and 9, etc., described later).

[0080] The image forming elements 11 to 14 are not arranged on the same plane, but are arranged at appropriate inclinations in three-dimensional space (see FIGS. 8 and 9, which will be described later).

[0081] The image forming element 11 is a high-definition, compact image forming element that displays an image to be output in a front area in the field of view of the observer U. The image forming element 11 has, for example, a pixel pitch of 6.3 μm, a diagonal size of 1.28 inches, and a resolution of 4032 ppi. The image forming element 11 is, for example, an M-OLED.

[0082] The image forming element 12 is disposed to the right of the image forming element 11, and displays an image to be output to the right peripheral region in the field of view of the observer U. The pixel pitch of the image forming element 12 is larger than that of the image forming element 11, for example, 24.0 μm, and the diagonal size is 2.89 inches. The resolution of the image forming element 12 is, for example, 1058 ppi. The image forming element 12 is, for example, an LTPS-LCD. Note that in the case of the optical unit for the left eye, the image forming element 12 is disposed to the left of the image forming element 11, and displays an image to be output to the left peripheral region in the field of view of the observer U.

[0083] The image forming element 13 is disposed above the image forming element 11 and displays an image to be output in an upper peripheral region in the field of view of the observer U. The image forming element 14 is disposed below the image forming element 11 and displays an image to be output in a lower peripheral region in the field of view of the observer U. The pixel pitch of the image forming element 13 and the image forming element 14 is both larger than that of the image forming element 11, for example, 24.0 μm, the diagonal size of both is for example 2.89 inches, and the resolution of both is for example 1058 ppi. The image forming element 13 and the image forming element 14 are each, for example, an LTPS-LCD.

[0084] An image corresponding to the virtual image output by the image forming element 13 and the eyepiece optical system 23 is referred to as image 13R (third image). An image corresponding to the virtual image output by the image forming element 14 and the eyepiece optical system 24 is referred to as image 14R (fourth image).

[0085] Table 2 shows examples of the design (specifications) of the corresponding optical elements (lenses in this example) and image-forming elements for each of the eyepiece optical systems 21 to 24, as well as the field of view range of the virtual images output by each of the eyepiece optical systems 21 to 24.

[0086] As shown in Table 2 above, in the optical unit 10 for the right eye 40R, the field angle range of the virtual image output by the eyepiece optical system 21 is, for example, a horizontal field angle range of -43° to 43° and a vertical field angle range of -36° to 36° when observed in a direction directly facing the virtual image plane. Also, in the optical unit 10 for the right eye 40R, the field angle range of the virtual image output by the eyepiece optical system 22 is, when observed in a direction directly facing the virtual image plane, a horizontal field angle range of 18° to 73° and a vertical field angle range of -48° to 48°. Also, in the optical unit 10 for the right eye 40R, the field angle range of the virtual image output by the eyepiece optical system 23 is, when observed in a direction directly facing the virtual image plane, a horizontal field angle range of -43° to 43° and a vertical field angle range of 11° to 50°. The field angle range of the virtual image output by the eyepiece optical system 24 is a horizontal field angle range of -43° to 43° and a vertical field angle range of -50° to -11° when observed in a direction directly facing the virtual image plane.

[0087] Furthermore, since the image forming element 11 corresponding to the eyepiece optical system 21 is a high-resolution, compact image forming element as described above, it is generally difficult to design a small, low-profile eyepiece optical system that can output the field of view required for the observer U to feel immersed using only a small image forming element of about 1 inch. According to this embodiment, the image forming elements 13 and 14 are disposed above and below the image forming element 11, respectively, and the corresponding eyepiece optical systems 23 and 24 output virtual images to peripheral regions above and below the field of view of the observer U. This allows the optical unit 10 for the right eye 40R as a whole to widen the vertical field of view to a range of ±50° in the observation direction directly facing the virtual image plane, thereby allowing the observer U to feel a high level of immersion through a wide-field-angle video experience.

[0088] Furthermore, the configuration of the optical unit for the left eye is basically the same as the configuration of the optical unit 10 for the right eye 40R, and the field of view area of ​​the virtual image divided and output by the eyepiece optical systems 21 to 24 included in the optical unit for the left eye is equal to the range obtained by swapping the positive and negative signs of the horizontal field of view (X field of view) in Table 2 above.

[0089] Therefore, the optical units for the left eye and right eye 40R overlap a field angle region of −43° or more and 43° or less horizontally and −50° or more and 50° or less vertically, and this field angle region is useful for providing depth perception to the observer U through parallax images. Furthermore, any two adjacent images are arranged so that they have an overlap region of at least a field angle of 25° or more, and due to eye movement, the direction in which the viewer gazes at the joining position between images 11R and 12R is 24° horizontally, the direction in which the viewer gazes at the joining position between images 11R and 13R is 17° vertically, and the direction in which the viewer gazes at the joining position between images 11R and 14R is −17° vertically.

[0090] 8 and 9 are diagrams illustrating an example of a schematic configuration of a virtual image display device 1 according to a second embodiment. FIG. 8 illustrates an example of a cross-sectional structure (horizontal cross-sectional view) of the optical unit 10 for the right eye 40R when viewed from above. FIG. 9 illustrates an example of a cross-sectional structure (vertical cross-sectional view) of the optical unit 10 for the right eye 40R when viewed from the side. Note that (B) of FIG. 8 and (B) of FIG. 9 also schematically illustrate several optical paths of light rays passing through the right eye 40R of the observer U and the optical unit 10.

[0091] 8, the eyepiece optical system 21 includes a lens L11, a lens L12, a lens L13, and a lens L14 located between the right eye 40R and the image forming element 11. The eyepiece optical system 22 includes a lens L21, a lens L22, and a lens L23 located in this order between the right eye 40R and the image forming element 12.

[0092] The eyepiece optical systems 21 and 22 are designed to output the field angle regions that are divided and displayed by the corresponding image forming elements 11 and 12. The optical unit 10 for the right eye 40R outputs a virtual image that has a horizontal field angle in the range of −43° to 73° as a whole.

[0093] 9, the eyepiece optical system 23 includes a lens L31, a lens L32, and a lens L33, which are positioned in this order between the right eye 40R and the image forming element 13. The eyepiece optical system 24 includes a lens L41, a lens L42, and a lens L43, which are positioned in this order between the right eye 40R and the image forming element 14.

[0094] The S1 and S2 lens surfaces of lens L31 are illustrated as lens surfaces S31 and S32. The S1 lens surface of lens L32 is illustrated as lens surface S33. The S1 and S2 lens surfaces of lens L41 are illustrated as lens surfaces S41 and S42. The S1 lens surface of lens L42 is illustrated as lens surface S43.

[0095] 9, the eyepiece optical system 21, the eyepiece optical system 23, and the eyepiece optical system 24 are designed so that the corresponding image forming elements 11, 13, and 14 can output the field angle regions that are divided and displayed. The optical unit 10 for the right eye 40R outputs a virtual image as a whole with a vertical field angle in the range of −50° to 50° inclusive in the observation direction directly facing the virtual image plane.

[0096] 8 and 9, the lens surface S11 of the lens L11 is shared by the eyepiece optical systems 21 to 24 and is designed as a concave spherical surface with a radius of curvature of 200 mm. As a result, assuming that the observer U wears glasses while wearing the virtual image display device 1, a sufficient amount of space is secured in front of the eyes, an optical path with a wide viewing angle of 73° horizontal angle of view is formed, and the design and cleanability of the S1 lens surface of the L1 lens, which serves as the appearance surface, i.e., the lens surface S11 of L11, the lens surface S21 of the lens L21, the lens surface S31 of the lens L31, and the lens surface S41 of the lens L41, are ensured.

[0097] Furthermore, in Figures 8 and 9, the lens surfaces indicated by dashed lines, i.e., lens surface S12 of lens L11, lens surface S22 of lens L21, lens surface S32 of lens L31, lens surface S42 of lens L41, as well as lens surface S14 of lens L12, lens surface S33 of lens L32, and lens surface S43 of lens L42, are all designed as Fresnel lens surfaces.

[0098] In order to suppress light loss and stray light at boundary surface 30, the above-mentioned lens surfaces S21, S22, S32, and S42 are particularly given strong positive refractive power, and are designed to prevent light rays traced from the eye side of observer U from intersecting boundary surface 30 after being refracted by lens surfaces S12, S22, S32, and S42. Note that lens surface S23 of lens L22 is a rotationally asymmetric free-form surface, which efficiently corrects decentering aberrations caused by decentering and tilt of lenses L21, L22, etc.

[0099] 10 is a perspective view showing the S2 lens surface of the L1 lens. Lenses L11 to L41 are integrally formed as a single lens (single L1 lens) with no physical boundaries. They can also be collectively referred to as lens L11.

[0100] The lens surface S12 of lens L11, the lens surface L22 of lens L21, the lens surface S32 of lens L31, and the lens surface S42 of lens L41 are all designed as Fresnel lens surfaces. Even if the designs of the lens surfaces differ, there are no steps at the boundaries, eliminating the need for optical paths that result in loss or stray light at the boundaries. This embodiment makes it possible to design an optical layout that would have been impossible if the S2 lens surface were not a Fresnel lens surface due to the design constraint of matching the ridgelines determined by the curvature of each lens surface. Therefore, the eyepiece optical system 21, which outputs a virtual image in the front region of the observer U's field of view, prioritizes resolution, while the eyepiece optical systems 22 to 24, which output virtual images in the peripheral region of the observer U's field of view, prioritize field of view. This allows for efficient design based on the characteristics required of each eyepiece optical system, such as prioritizing resolution and focusing on the viewing angle, thereby enabling the virtual image display device 1 as a whole to be made smaller and lighter.

[0101] 11 is a diagram showing an example of a region of the angle of view displayed by the optical unit 10. Parts of the images 11R to 14R may overlap with each other.

[0102] 11A shows the range of the angle of view observed when observer U is looking at gaze point 70 in front (when the gaze direction is directly facing the virtual image planes created by eyepiece optical system 21, eyepiece optical system 23, and eyepiece optical system 24). At this time, images 11R, 13R, and 14R are each observed as a rectangle, but because the gaze direction is tilted by 15° horizontally with respect to the virtual image plane created by eyepiece optical system 22, the vertical angle of view of image 12R widens to a maximum of ±63° as it moves toward the ear due to trapezoidal distortion.

[0103] 11B shows the range of the angle of view observed when the observer U is looking at the gaze point 71 at 15° in the horizontal direction (when the gaze direction is directly facing the virtual image plane created by the eyepiece optical system 22). Only by moving the line of sight to 15° in the horizontal direction can the image 12R be observed as a rectangular image. Here, if the virtual image plane created by the eyepiece optical system 22 is not tilted, the vertical angle of view appears narrower toward the periphery due to trapezoidal distortion, which inhibits the sense of immersion. However, according to this embodiment, the observer U can obtain a high sense of immersion by experiencing an image that seems to surround him or her.

[0104] As described above, the virtual image display device 1 according to the second embodiment facilitates a design that widens the vertical angle of view of the virtual image output to the peripheral region in the field of view of the observer U, while maintaining high definition of the virtual image output to the front region in the field of view of the observer U. Other configurations and effects may be substantially the same as those of the virtual image display device 1 according to the first embodiment described above.

[0105] 1.3 Third Embodiment In the virtual image display device 1 according to the third embodiment, the optical unit for the left eye and the optical unit 10 for the right eye 40R each include a plurality of image forming elements including an image forming element 11 (first image forming element) and an image forming element 12 (second image forming element), and a plurality of ocular optical systems including corresponding ocular optical systems 21 (first ocular optical system) and 22 (second ocular optical system) (see FIG. 12 , etc., described later).

[0106] The image forming elements 11 and 12 are not arranged on the same plane, but are arranged at an appropriate inclination in three-dimensional space (see FIG. 12, etc., described later).

[0107] For each of the eyepiece optical system 21 and the eyepiece optical system 22, the design (specifications) of the corresponding optical elements and image-forming elements, as well as the field of view area of ​​the virtual images output by each of the eyepiece optical system 21 and the eyepiece optical system 22, are the same as those in Table 1 of the first embodiment described above.

[0108] 12 is a diagram illustrating an example of a schematic configuration of a virtual image display device 1 according to a third embodiment. The diagram illustrates an example of a cross-sectional structure (horizontal cross-section) of the optical unit 10 for the right eye 40R when viewed from above. (B) of FIG. 12 also schematically illustrates several optical paths of light rays passing through the right eye 40R of the observer U and the optical unit 10.

[0109] The eyepiece optical system 21 includes lenses L11, L12, L13, and L14, which are positioned in this order between the right eye 40R and the image forming element 11. The eyepiece optical system 22 includes lenses L21 and L22, which are positioned in this order between the right eye 40R and the image forming element 12. The S1 lens surface of the lens L12 is illustrated as lens surface S13.

[0110] The S1 lens surface of the L1 lens, i.e., the lens surface S11 of the lens L11 and the lens surface S21 of the lens L21, is shared by the eyepiece optical system 21 and the eyepiece optical system 22, and is designed as a concave spherical surface with a radius of curvature of 1000 mm. As a result, assuming that the observer U will wear glasses while wearing the virtual image display device 1, a sufficient amount of space is secured in front of the eyes, an optical path with a wide viewing angle of 70° horizontal angle of view is formed, and the design and cleanability of the S1 lens surface of the L1 lens, which serves as the appearance surface, i.e., the lens surface S11 of the lens L11 and the lens surface S21 of the lens L21, is ensured.

[0111] 12, the lens surface S12 of the lens L11, the lens surface S22 of the lens L21, and the lens surface S13 of the lens L12 and the lens surface S23 of the lens L22 are all designed as Fresnel lens surfaces. In this case, in each of the eyepiece optical systems 21 and 22, a light ray traced from the eye side of the observer U is refracted by the lens surface S12 of the lens L11 and the lens surface S22 of the lens L21, and then is further refracted by the lens surface S13 of the lens L12 and the lens surface S23 of the lens L22. It is sufficient to design the systems using two Fresnel lens surfaces so that the bundle of rays does not intersect with the boundary surface 30. As a result, the refractive power required to prevent the bundle of rays from intersecting the boundary surface 30 is not imparted only to the lens surface S12 of the lens L11 and the lens surface S22 of the lens L21 in the eyepiece optical system 21 and the eyepiece optical system 22, respectively, but can be dispersed by two Fresnel lens surfaces formed on the opposing surfaces of the lenses L11 and L21 and the lenses L12 and L22, enabling an optical design with a well-balanced power distribution. Note that the lens surface S24 of the lens L22 is a rotationally asymmetric free-form surface, which efficiently corrects decentering aberrations caused by decentering and tilt of the lens surface S22 of the lens L21 and the lens surface S23 of the lens L22.

[0112] In addition, in Figure 12, lenses L12 and L22 are integrally formed so as to have no physical bonded interface. If lens surface S13 of lens L12 and lens surface S23 of lens L22 were not Fresnel lens surfaces and if the ridgelines determined by the respective curvatures of lens surfaces S13 and S23 did not coincide, an inverted tapered step would be formed at the boundary between lens surfaces S13 and S23, making them difficult to remove from the mold and thus difficult to mold integrally. According to this embodiment, lenses L12 and L22 do not have an inverted tapered structure, making it possible to mold lenses L12 and L22 integrally. As a result, the relative positional accuracy between the lens surfaces in eyepiece optical system 21 and eyepiece optical system 22 can be guaranteed by the machining accuracy of the mold, achieving accuracy on the order of 10 μm. As a further advantage, according to this embodiment, the assembly of the eyepiece optical system 22 is completed when the integrally molded lenses L11 and L21, and the lenses L12 and L22 are incorporated into the lens barrel, thereby significantly simplifying the manufacturing process.

[0113] As described above, the virtual image display device 1 according to the third embodiment enables a design with high definition while suppressing manufacturing costs. Other configurations and effects may be substantially the same as those of the virtual image display device 1 according to the first embodiment described above.

[0114] 1.4 Fourth Embodiment As described above, the virtual image display device 1 may include a sliding mechanism capable of controlling the virtual image distance. Such a virtual image display device 1 according to a fourth embodiment will be described with reference to FIG. 13 .

[0115] Fig. 13 is a diagram showing an example of a schematic configuration of a virtual image display device according to a fourth embodiment. The virtual image display device 1 includes a sliding mechanism 90. Although not shown in Fig. 13, the virtual image display device 1 may have the same configuration as the embodiments described so far.

[0116] For example, the sliding mechanism 90 slides (moves) the image forming element 11 so that the image forming element 11 approaches or moves away from the eyepiece optical system 21. The sliding mechanism 90 may also move the eyepiece optical system 21 so that (at least some of the lenses constituting) the eyepiece optical system 21 approaches or moves away from the image forming element 11.

[0117] By moving the image forming element 11 or the eyepiece optical system 21, the distance of the virtual image output by the eyepiece optical system 21 can be controlled, for example, from 20 mm in front of the observer U to infinity. The sliding mechanism 90 may be acted upon by a relatively small, fast-response actuator using a piezoelectric element or the like.

[0118] As described above, the image-forming elements 12 to 14 and the eyepiece optical systems 22 to 24 may also have their virtual image distances controlled by sliding them using the sliding mechanism 90. By increasing the degree of freedom in optical design, it is possible to meet requirements for image quality and housing size while controlling the virtual image distance.

[0119] 1.5 Fifth Embodiment As described above, the virtual image display device 1 may include a liquid crystal lens instead of the sliding mechanism 90. Such a virtual image display device 1 according to a fifth embodiment will be described with reference to FIG.

[0120] 14 is a diagram illustrating an example of a schematic configuration of a virtual image display device according to the fifth embodiment. The virtual image display device 1 further includes a liquid crystal lens 80. The illustrated liquid crystal lens 80 is disposed between a plurality of ocular optical systems, in this example, the ocular optical systems 21 and 22, and the right eye 40R.

[0121] The liquid crystal lens 80 includes a liquid crystal layer and is driven by a voltage from a voltage source circuit 81. The refractive index of the liquid crystal lens 80 changes in response to the voltage from the voltage source circuit 81, and the focal length also changes. In this way, the virtual image distance can also be controlled. Since there is no mechanical mechanism such as the sliding mechanism 90 described above, there is a greater possibility of speeding up control and improving reliability.

[0122] In addition, in the configuration including the image forming elements 13 and 14 and the eyepiece optical systems 23 and 24 described above, the virtual image distance may be controlled using the liquid crystal lens 80 in the same manner as described above.

[0123] The control of the virtual image distance in the fourth or fifth embodiment may be performed based on the convergence angle of the viewer U, and for this purpose, the line of sight direction of the viewer U may be detected. The following description will also refer to FIG. 15 .

[0124] 15 is a diagram showing an example of detecting the direction of the line of sight. The virtual image display device 1 includes an imaging device 45. Note that imaging may be interpreted to include photography.

[0125] 15A and 15B, the imaging device 45 is disposed outside the eyepiece optical systems 21 to 24. The single imaging device 45 directly captures an image of the eye of the observer U from the nose side of the observer U.

[0126] 15C , four imaging devices 45 are arranged around the periphery of the image forming element 11 between the image forming elements 11 to 14 and the eyepiece optical systems 21 to 24. These four imaging devices 45 are referred to as imaging devices 45-1 to 45-4 and are illustrated. An image of the eye of the observer U is captured through one of the eyepiece optical systems 21 to 24. The imaging devices 45-2 to 45-4 are arranged between the image forming element 11 and the image forming elements 12 to 14. It should be noted that three or fewer, or five or more, imaging devices 44 may be arranged between the image forming elements 11 to 14 and the eyepiece optical systems 21 to 24.

[0127] The convergence angle of the observer U is obtained based on the image capture result of the imaging device 45. Various image recognition processing techniques may be used. Depending on the obtained convergence angle, the sliding mechanism 90 or the liquid crystal lens 80 described above controls the virtual image distance.

[0128] 2. Summary The techniques described above can be specified, for example, as follows. One of the techniques disclosed is a virtual image display device 1. As described with reference to FIGS. 4 to 15 , the virtual image display device 1 includes a first image forming element (image forming element 11) that outputs a first image (image 11R) in a frontal region in the field of view of the observer U, and a second image forming element (image forming element 12) that outputs a second image (image 12R) different from the first image in a peripheral region in the field of view of the observer U. The virtual image display device 1 also includes a plurality of image forming elements that output a plurality of images including the first and second images (images 11R and 12R) such that at least a portion of each image region overlaps with the first image (image 11R), and a plurality of eyepiece optical systems (e.g., eyepiece optical systems 21 and 22, and also eyepiece optical systems 23 and 24) that are provided corresponding to the plurality of image forming elements and that form a single virtual image as a whole from the plurality of images. In the multiple eyepiece optical systems, the lens surfaces located closest to the eye of the observer U (for example, the right eye 40R side) (for example, lens surfaces S11 and S21, or further, lens surfaces S31 and S41) are lens surfaces shared by the respective eyepiece optical systems, and further, the lens surfaces located second from the eye of the observer U opposite the lens surfaces (for example, lens surfaces S12 and S22, or further, lens surfaces S32 and S42) are designed as Fresnel lens surfaces, and the lenses located closest to the eye of the observer U (for example, lens L11 and L21, or further, lens L31 and L41) are molded as a single unit.

[0129] As described above, the above-described virtual image display device 1 can achieve both a comfortable fit and a sense of immersion. As a more specific configuration, for example, the following configuration may be adopted.

[0130] As explained with reference to Tables 1 and 2, etc., in the multiple eyepiece optical systems, the multiple eyepiece optical systems (e.g., eyepiece optical system 22 to eyepiece optical system 24) provided corresponding to the multiple image forming elements (e.g., image forming element 12 to image forming element 14) including the second image forming element (image forming element 12) that outputs an image in the peripheral region in the field of view of observer U may each be designed differently (e.g., with a different resolution or angle of view) from the first eyepiece optical system (ocular optical system 21) provided corresponding to the first image forming element (image forming element 11).

[0131] As explained with reference to Figures 4, 8, 9 and 12, among the multiple eyepiece optical systems, the multiple eyepiece optical systems (e.g., eyepiece optical system 22 to eyepiece optical system 24) provided corresponding to the multiple image forming elements (e.g., image forming elements 12 to 14) including the second image forming element (image forming element 12) may each be configured to include at least one lens surface (e.g., lens surface S23, lens surface S24) that is not rotationally symmetric with respect to the optical axis of the first eyepiece optical system (ocular optical system 21) provided corresponding to the first image forming element (image forming element 11).

[0132] As described with reference to Figures 4, 8, 9, and 12, etc., lens surfaces shared by multiple eyepiece optical systems (e.g., lens surfaces S11 and S21, and further lens surfaces S31 and S41) may be designed as concave surfaces.

[0133] As explained with reference to Tables 1 and 2, the first image (image 11R) may have a higher resolution than the second image (image 12R).

[0134] The plurality of eyepiece optical systems may include a first eyepiece optical system (eyepiece optical system 21) provided corresponding to a first image forming element (image forming element 11), and the first eyepiece optical system may be configured to output a virtual image with a horizontal angle of view of 60° to 120° and a vertical angle of view of 40° to 120°. The resolution of the first image forming element (image forming element 11) may be 2000 ppi or more, and the resolution of the second image forming element (image forming element 12) may be less than 2000 ppi.

[0135] 4, 8, 9, 12, etc., in the plurality of eyepiece optical systems, the lens surface located third from the eye of the observer U (e.g., lens surface S23, lens surface S33, lens surface S43) may be designed as a Fresnel lens surface. In the plurality of eyepiece optical systems, the lens located second from the eye of the observer U (e.g., lenses L11 and L21, or further lenses L31 and L41) may be formed integrally.

[0136] As explained with reference to Figure 6 etc., in multiple eyepiece optical systems, the distance from the observer U to the virtual image plane of each of the multiple eyepiece optical systems may be designed so that the boundary between the images output by adjacent eyepiece optical systems matches in the direction in which the images are observed.

[0137] As described with reference to FIG. 13 and other figures, the virtual image display device 1 may further include a sliding mechanism 90 that controls the virtual image distance from the observer U to the virtual image plane formed by each of the multiple eyepiece optical systems by sliding the position of each lens constituting the multiple eyepiece optical systems or the position of each of the multiple image forming elements. Alternatively, as described with reference to FIG. 14 and other figures, the virtual image display device 1 may further include a liquid crystal lens 80 that is disposed between the observer U and the multiple eyepiece optical systems and controls the virtual image distance from the observer U to a single virtual image plane formed by the multiple eyepiece optical systems as a whole. The controlled virtual image distance may range from 20 mm in front of the observer U to infinity. As described with reference to FIG. 15 and other figures, the virtual image distance may be controlled according to the convergence angle of the observer U obtained from the detection result of the gaze direction of the observer U.

[0138] The virtual image display device 1 may be used by being worn on the head of the observer U. That is, the virtual image display device 1 may be a head-mounted type virtual image display device 1.

[0139] The effects described in this disclosure are merely examples and are not limited to the disclosed contents. Other effects may also be obtained.

[0140] Although the embodiments of the present disclosure have been described above, the technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, components of different embodiments and modifications may be combined as appropriate.

[0141] The present technology can also be configured as follows: (1) A virtual image display device including a first image forming element that outputs a first image in a front region in a viewer's field of view, and a second image forming element that outputs a second image different from the first image in a peripheral region in the viewer's field of view, the image forming elements outputting a plurality of images including the first and second images such that at least a portion of each image region overlaps with the first image, and a plurality of eyepiece optical systems that are provided corresponding to the plurality of image forming elements and form a single virtual image as a whole from the plurality of images, wherein a lens surface of each of the plurality of eyepiece optical systems that is closest to the viewer's eye is a lens surface shared by each of the eyepiece optical systems, and further, a lens surface that is opposite to the lens surface and that is second from the viewer's eye is designed as a Fresnel lens surface, and the lens that is closest to the viewer's eye is molded as a single unit. (2) The virtual image display device according to (1), wherein, in the plurality of eyepiece optical systems, each of the plurality of eyepiece optical systems provided corresponding to a plurality of image forming elements including the second image forming element that outputs an image to a peripheral region in the viewer's field of view has a different design from that of the first eyepiece optical system provided corresponding to the first image forming element. (3) The virtual image display device according to (2), wherein the different designs include at least one of different resolution designs and different angle of view designs. (4) The virtual image display device according to any of (1) to (3), wherein, in the plurality of eyepiece optical systems, each of the plurality of eyepiece optical systems provided corresponding to a plurality of image forming elements including the second image forming element is configured to include at least one lens surface that does not have rotational symmetry with respect to the optical axis of the first eyepiece optical system provided corresponding to the first image forming element. (5) The virtual image display device according to any of (1) to (4), wherein the lens surface shared by the plurality of eyepiece optical systems is designed as a concave surface. (6) The virtual image display device according to any one of (1) to (5), wherein the first image has a higher resolution than the second image.(7) The virtual image display device according to any one of (1) to (6), wherein the plurality of eyepiece optical systems includes a first eyepiece optical system provided corresponding to the first image-forming element, and the first eyepiece optical system is configured to output a virtual image with a horizontal angle of view of 60° to 120° and a vertical angle of view of 40° to 120°. (8) The virtual image display device according to any one of (1) to (7), wherein the resolution of the first image-forming element is 2000 ppi or more, and the resolution of the second image-forming element is less than 2000 ppi. (9) The virtual image display device according to any one of (1) to (8), wherein, in the plurality of eyepiece optical systems, a lens surface located third from the viewer's eye side is designed as a Fresnel lens surface. (10) The virtual image display device according to any one of (1) to (9), wherein, in the plurality of eyepiece optical systems, a lens located second from the viewer's eye side is formed integrally. (11) The virtual image display device according to any one of (1) to (10), wherein the plurality of eyepiece optical systems are designed so that the distance from the viewer to a virtual image surface formed by each of the plurality of eyepiece optical systems matches in a direction in which a boundary between images output by adjacent eyepiece optical systems is observed. (12) The virtual image display device according to any one of (1) to (11), further comprising a sliding mechanism that controls a virtual image distance from the viewer to a virtual image surface formed by each of the plurality of eyepiece optical systems by sliding the position of each lens constituting the plurality of eyepiece optical systems or the position of each of the plurality of image forming elements. (13) The virtual image display device according to any one of (1) to (11), further comprising a liquid crystal lens that is disposed between the viewer and the plurality of eyepiece optical systems and controls a virtual image distance from the viewer to a single virtual image surface formed by the plurality of eyepiece optical systems as a whole. (14) The virtual image display device according to (12) or (13), wherein the control range of the virtual image distance is from 20 mm in front of the viewer to infinity. (15) The virtual image display device according to any one of (12) to (14), wherein the virtual image distance is controlled in accordance with a convergence angle of the observer obtained from a detection result of a line-of-sight direction of the observer. (16) The virtual image display device according to any one of (1) to (15), wherein the virtual image display device is used by being worn on the head of the observer.

[0142] REFERENCE SIGNS LIST 1 Virtual image display device 10 Optical unit 11 Image forming element (first image forming element) 12 Image forming element (second image forming element) 13 Image forming element (third image forming element) 14 Image forming element (fourth image forming element) 21 Eyepiece optical system (first eyepiece optical system) 22 Eyepiece optical system (second eyepiece optical system) 23 Eyepiece optical system (third eyepiece optical system) 24 Eyepiece optical system (fourth eyepiece optical system) 30 Boundary surface 31 Boundary portion 40R Right eye 45 Imaging device 50 Boundary position 61 Virtual image surface 62 Virtual image surface 70 Point of gaze 71 Point of gaze 80 Liquid crystal lens 81 Voltage source circuit 90 Sliding mechanism L11 Lens L12 Lens L13 Lens L14 Lens L21 Lens L22 Lens L23 Lens L31 lens L32 lens L33 lens L41 lens L42 lens L43 lens S11 lens surface S12 lens surface S13 lens surface S14 lens surface S21 lens surface S22 lens surface S23 lens surface S24 lens surface S31 lens surface S32 lens surface S33 lens surface S41 lens surface S42 lens surface S43 lens surface U observer

Claims

1. A virtual image display device comprising: a first image forming element which outputs a first image in a frontal region in a viewer's field of view; and a second image forming element which outputs a second image different from the first image in a peripheral region in the viewer's field of view, the first image being a plurality of image forming elements which output a plurality of images including the first and second images such that at least a portion of each image region overlaps with the first image; and a plurality of eyepiece optical systems which are provided corresponding to the plurality of image forming elements and which form a single virtual image as a whole from the plurality of images, the lens surface of the plurality of eyepiece optical systems which is closest to the viewer's eye is a lens surface shared by each of the eyepiece optical systems, the second lens surface from the viewer's eye opposite the lens surface is designed as a Fresnel lens surface, and the lens which is closest to the viewer's eye is molded as a single unit.

2. A virtual image display device as described in claim 1, wherein, in the plurality of eyepiece optical systems, the plurality of eyepiece optical systems provided corresponding to the plurality of image forming elements including the second image forming element that outputs an image to a peripheral region in the viewer's field of view are each designed differently from the first eyepiece optical system provided corresponding to the first image forming element.

3. The virtual image display device according to claim 2, wherein the different designs include at least one of a different resolution design and a different angle of view design.

4. A virtual image display device as described in claim 1, wherein among the multiple eyepiece optical systems, each of the multiple eyepiece optical systems provided corresponding to the multiple image forming elements including the second image forming element is configured to include at least one lens surface that does not have rotational symmetry with respect to the optical axis of the first eyepiece optical system provided corresponding to the first image forming element.

5. The virtual image display device according to claim 1, wherein the lens surface shared by the plurality of eyepiece optical systems is designed as a concave surface.

6. The virtual image display device according to claim 1, wherein the first image has a higher resolution than the second image.

7. The virtual image display device according to claim 1, wherein the plurality of eyepiece optical systems include a first eyepiece optical system provided corresponding to the first image forming element, and the first eyepiece optical system is configured to output a virtual image having a horizontal angle of view of 60° or more and 120° or less and a vertical angle of view of 40° or more and 120° or less.

8. The virtual image display device according to claim 1, wherein the resolution of the first image forming element is 2000 ppi or more, and the resolution of the second image forming element is less than 2000 ppi.

9. The virtual image display device according to claim 1, wherein, in said plurality of eyepiece optical systems, the lens surface located third from the eye side of the observer is designed as a Fresnel lens surface.

10. The virtual image display device according to claim 1, wherein, in said plurality of eyepiece optical systems, the lens located second from the observer's eye side is integrally formed.

11. A virtual image display device as described in claim 1, wherein the plurality of eyepiece optical systems are designed such that the distance from the viewer to the virtual image surface of each of the plurality of eyepiece optical systems coincides in the direction in which the boundary between the images output by adjacent eyepiece optical systems is observed.

12. The virtual image display device according to claim 1, further comprising a sliding mechanism that controls the virtual image distance from the observer to the virtual image surface formed by each of the plurality of eyepiece optical systems by sliding the position of each lens constituting the plurality of eyepiece optical systems or the position of each of the plurality of image forming elements.

13. The virtual image display device according to claim 1, further comprising a liquid crystal lens disposed between the observer and the plurality of eyepiece optical systems, for controlling a virtual image distance from the observer to a single virtual image surface formed as a whole by the plurality of eyepiece optical systems.

14. The virtual image display device according to claim 12, wherein the control range of the virtual image distance is from 20 mm in front of the viewer to infinity.

15. The virtual image display device according to claim 12, wherein the virtual image distance is controlled in accordance with a convergence angle of the observer obtained from a detection result of the line of sight of the observer.

16. The virtual image display device according to claim 1, which is used by being worn on the head of the observer.

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