Optical member, display device, and method of manufacturing optical member

Abstract

To provide an optical member and a display device that have a structure for obtaining a high-quality image, and a method of manufacturing the optical member.SOLUTION: An optical member is used for a display device and guides image light from an image display element for displaying an image. The optical member includes: an incident surface on which the image light is incident from a first direction; an emission surface from which the image light is emitted from a second direction orthogonal to the first direction; a plurality of partial reflection surfaces that are arranged side by side in the first direction, transmit a portion of a light flux included in the image light, and reflect the other portion; and a plurality of bonding layers formed corresponding to the plurality of partial reflection surfaces. At least one of the following conditions is satisfied: on the emission surface, a first covering portion convers a plane including a boundary portion between the emission surface and one end portion of the plurality of bonding layers; and on an opposite surface of the emission surface, a second covering portion covers a plane including a boundary portion between an opposite surface and the other end portion of the plurality of bonding layers.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an optical member, a display device, and a method for manufacturing an optical member. [Background technology]

[0002] Patent document 1 describes an optical device that includes a light-transmitting substrate, optical means for coupling light into the substrate by total internal reflection, and a plurality of partially reflective surfaces possessed by the substrate, the partially reflective surfaces being parallel to each other and not parallel to any edges of the substrate.

[0003] The optical device of Patent Document 1 is applied, for example, as an optical member used in a see-through head-mounted display (HMD). A known configuration of a see-through head-mounted display is, for example, a system in which image light emitted from an image display element is incident on an optical member and reflected by multiple partially reflective surfaces contained in the optical member, thereby emitting the image light toward a user. In this type of optical member, multiple partially reflective surfaces are formed at a desired angle relative to the emission surface. A known method for manufacturing such an optical member is, for example, to apply a coating that forms a partially reflective surface to the surfaces of multiple transparent flat plates, stack them, bond them with an adhesive, and then cut them out. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2003-536102 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the inventor's intensive research, in the prior art including Patent Document 1, the bonding layer (the boundary between the transmitting surface and the partially reflective surface) formed by the adhesive layer used when stacking the multiple transmitting flat plates that form the multiple partially reflective surfaces is exposed on the exit surface of the optical element and the surface facing it (the opposite surface). Furthermore, unevenness may occur on the surface of the optical element due to differences in hardness between the transmitting flat plates and the bonding layer. Furthermore, if unevenness occurs on the surface of the optical element, the image displayed on the display device may be degraded and may be visually perceived by the user. Thus, the prior art including Patent Document 1 leaves room for improvement in terms of providing an optical element, a display device, and a method for manufacturing an optical element that are equipped with a structure for obtaining high-quality images.

[0006] The present invention has been made based on the above-mentioned awareness of the problems, and aims to provide an optical element and a display device equipped with a structure for obtaining high-quality images, as well as a method for manufacturing the optical element. [Means for solving the problem]

[0007] The optical element of the present invention is an optical element used in a display device and guiding image light from an image display element that displays an image, and has an incident surface into which the image light is incident from a first direction, an exit surface from which the image light is exited from a second direction perpendicular to the first direction, a plurality of partially reflecting surfaces arranged in line in the first direction and transmitting a portion of the light beam contained in the image light and reflecting another portion, and a plurality of bonding layers formed corresponding to the plurality of partially reflecting surfaces, and is characterized in that at least one of the following is satisfied: on the exit surface, a plane including a boundary between the exit surface and one end of the plurality of bonding layers is covered by a first covering portion; and on the opposing surface of the exit surface, a plane including a boundary between the opposing surface and the other end of the plurality of bonding layers is covered by a second covering portion. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an optical member and a display device equipped with a structure for obtaining a high-quality image, as well as a method for manufacturing an optical member. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a head-mounted display that is an example of a virtual image display device according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing an example of an optical system for a virtual image display device according to one embodiment of the present invention. [Figure 3] FIG. 1 is a diagram illustrating an example of a conventional technical problem. [Figure 4] 3A and 3B are diagrams illustrating an example of the surface shapes of the light exit surface and the opposing surface of the optical member of the present embodiment. [Figure 5] 1A and 1B are diagrams illustrating an example of the configuration of an optical member according to an embodiment of the present invention. [Figure 6] 3A to 3C are process diagrams illustrating an example of a method for manufacturing an optical member according to the present embodiment. [Figure 7] 10A and 10B are diagrams showing other embodiments of the configuration of the first and second covering portions. [Figure 8] 10A and 10B are diagrams illustrating another example of the configuration of the optical member. [Figure 9] FIG. 10 is a cross-sectional view showing an optical system for a virtual image display device according to a specific numerical example. [Figure 10] 10A and 10B are diagrams showing lateral aberration when image light from an image display element passes through an optical system for a virtual image display device in a numerical example. [Figure 11] 10A and 10B are diagrams showing lateral aberration when light from an object at infinity passes through an optical member in a numerical example. DETAILED DESCRIPTION OF THE INVENTION

[0010] An optical system for a virtual image display device according to one embodiment of the present invention and a head-mounted display, which is an example of a virtual image display device, will be described below with reference to the drawings. In the following description, common or corresponding elements will be denoted by the same or similar reference numerals, and redundant explanations will be appropriately simplified or omitted. Here, "optical system for a virtual image display device" may be read as "optical system," and "virtual image display device" and "head-mounted display" may be read as "display device." Furthermore, "optical member" may be read as "light-guiding member."

[0011] In this specification, the term "image light" may simply be read as "light." In the following embodiments, the light emitted from each pixel of the image display element (light related to a virtual image) is called the image light, but the image light may also be read as "light" guided by the optical member.

[0012] In this specification, the "first direction" and the "second direction" are defined as follows: the direction in which image light (light) from the image display element 10 is incident on the optical member is defined as the "first direction," and the direction perpendicular to this "first direction" is defined as the "second direction." The "first direction" corresponds to the negative side of the y direction in FIG. 2 (the direction from left to right in FIG. 2). The "second direction" corresponds to the positive side of the z direction in FIG. 2 (the direction from top to bottom in FIG. 2).

[0013] <Outline of head-mounted display configuration> FIG. 1 is a schematic diagram of a head-mounted display 1, which is an example of a virtual image display device according to an embodiment of the present invention. The head-mounted display 1 is a virtual image display device that can be worn on the head of a wearer. In this embodiment, the head-mounted display 1 is, for example, smart glasses, which are eyeglass-type wearable devices. Smart glasses may also be called a glass device or a glass display.

[0014] The head mounted display 1 may be a wearable terminal called VR (Virtual Reality) glasses, AR (Augmented Reality) glasses, MR (Mixed Reality) glasses, XR (Extended Reality) glasses, or the like.

[0015] In the example of Fig. 1, the head mounted display 1 is a binocular type head mounted display. In another embodiment, the head mounted display 1 may be a monocular type head mounted display corresponding to one of the left and right eyes. The head mounted display 1 includes an image display element 10 and a lens unit 3. The lens unit 3 includes an optical member (light guide member) 50 used in a see-through type head mounted display.

[0016] 1, a head mounted display 1 includes a frame unit 2 and a lens unit 3. The lens unit 3 is fitted into the frame unit 2. A pair of lens units 3 are provided corresponding to the left and right eyes of the wearer.

[0017] An image display element 10 that displays an image is built into the frame unit 2. In the example of FIG. 1, the image display element 10 is embedded in a portion of the frame unit 2 that covers the upper edge of the lens unit 3. The installation position of the image display element 10 is not limited to the position exemplified in FIG. 1. For example, the image display element 10 may be embedded in a portion of the frame unit 2 that covers the lower edge, right edge, or left edge of the lens unit 3. The image display element 10 may also be used in a manner that includes a control board that drives and controls the image display element 10. In this case, the control board may be embedded in the temple portion of the frame unit 2 (the portion that hangs over the wearer's ears) instead of the portion depicted by reference numeral 10 in FIG. 1.

[0018] The image display element 10 is an element that emits an image to be observed as a virtual image (image light to be displayed to the user), and examples thereof include an OLED (organic light emitting diode) array, an LD (laser diode) array, an LED (light emitting diode) array, a MEMS (micro electro mechanical systems), and a DMD (digital micromirror device). The image display element 10 may also be a micro LED, a micro OLED, or an LCOS (liquid crystal on silicon). The image display element 10 is positioned and fixed (embedded) at a predetermined position in the lens unit 3 so that the image light is incident on the optical member 50. Note that instead of directly incidenting the image light from the image display element 10 on the optical member 50, another optical system may be interposed between the image display element 10 and the optical member 50, so that the image light is indirectly incident on the optical member 50 from the image display element 10.

[0019] 1, the first horizontal direction from the lens unit 3 toward the wearer's eye is referred to as the z direction, the second horizontal direction perpendicular to the z direction is referred to as the x direction, and the vertical direction perpendicular to both the x direction and the z direction is referred to as the y direction. The mutually perpendicular x direction, y direction, and z direction form a left-handed system.

[0020] Note that the names of directions are used for convenience to explain the relative positional relationships of the components, and do not indicate absolute directions. Depending on the posture of the wearer wearing the head mounted display 1, for example, the z direction is not necessarily horizontal, and may be vertical.

[0021] Light emitted from each pixel of the image display element 10 (i.e., image light (light related to a virtual image)) is emitted from the image display element 10 toward the negative side in the y direction, enters the lens unit 3, is guided through the lens unit 3, and is emitted toward the positive side in the z direction (in other words, toward each eye of the wearer) to display a virtual image. That is, each of the pair of left and right lens units 3 forms an eye box in an area including the corresponding eye. More specifically, an optical member 50 is provided within the lens unit 3, and image light from the image display element 10 is guided to the optical member 50 from a first direction. The optical member 50 has a plurality of partially reflective surfaces 53 formed thereon, which reflect the image light guided to the optical member 50 from the first direction and emit it to the outside from a second direction of the optical member 50 (forming the eye box). When a user wears the head-mounted display 1, the optical member 50 is positioned so as to be in front of the user's eyes.

[0022] FIG. 2 is a cross-sectional view showing an example of an optical system for a virtual image display device according to an embodiment of the present invention. As shown in FIG. 2, image light from an image display element 10 that displays an image is guided by an optical member 50. The optical member 50 has an incident surface 51 onto which the image light is incident from a first direction (negative side of the y direction, from left to right in FIG. 2) and an exit surface 52 from which the image light is exited from a second direction (positive side of the z direction, from top to bottom in FIG. 2) that is perpendicular to the first direction. The optical member 50 also has a plurality of partially reflecting surfaces 53 that are arranged in the first direction (negative side of the y direction, from left to right in FIG. 2) and transmit a portion of the light beam contained in the image light and reflect the other portion. As a result, the image light from the image display element 10 is emitted toward each eye of the wearer to display a virtual image, and an eyebox is formed in the area including the corresponding eye. Furthermore, external information (e.g., scenery, etc.) can be viewed from the surface 54 of the optical member 50 opposite the exit surface 52 (the surface opposite to the surface sandwiching the plurality of partially reflective surfaces 53). In other words, the opposite surface 54 serves as an incident surface for external light when used in a glass device such as smart glasses. This allows the user to view the image light from the image display element 10 superimposed on the external information (e.g., scenery, etc.). Note that in FIG. 2, the plurality of partially reflective surfaces 53 are simplified and depicted by dashed lines as if they were a single partially reflective surface.

[0023] The optical element 50 is formed of an optical material such as resin or glass. From the viewpoint of ease of attachment, a lightweight resin material is preferable, and polymethyl methacrylate (PMMA) or cycloolefin polymer (COP) may be used. Considering lightness, the thickness of the optical element 50 from the exit surface 52 to the opposing surface 54 is preferably 5 mm or less. The plurality of partially reflective surfaces 53 may be formed of, for example, half mirrors or polarizing beam splitters (PBS). Furthermore, the plurality of partially reflective surfaces 53 may be formed by coatings applied to a plurality of transmissive flat plates that are the original (material) of the optical element 50. Incidentally, a plurality of bonding layers (layers indicated by reference numeral 55, described later) formed corresponding to the plurality of partially reflective surfaces 53 are not components of the plurality of partially reflective surfaces 53.

[0024] <Technical issues with conventional head-mounted displays> As described above, in the conventional techniques including Patent Document 1, in the manufacturing process of an optical element, first, a plurality of transmitting flat plates with a coating applied to the surface that functions as a partially reflective surface are prepared, and then these are stacked and adjacent transmitting flat plates are bonded (joined) to form a rectangular parallelepiped. After that, the optical element is completed by cutting, grinding and polishing the surface layer so that each partially reflective surface (each bonded surface) has a desired angle with respect to the emission surface.

[0025] However, the adhesive layer (the boundary between the transmitting surface and the partially reflective surface) used when stacking the multiple transmitting flat plates that form the multiple partially reflective surfaces is exposed on the exit surface and the surface facing the exit surface (the opposite surface) of the optical element. Furthermore, due to the difference in hardness between the transmitting flat plates and the bonding layer, unevenness may occur on the surface of the optical element (especially when polishing the optical element after cutting). Furthermore, if unevenness occurs on the surface of the optical element, the image displayed on the display device may be degraded and may be visible to the user (the unevenness may be visible as lines). Thus, the prior art, including Patent Document 1, leaves room for improvement in terms of providing an optical element, a display device, and a method for manufacturing an optical element that have a structure for obtaining high-quality images.

[0026] FIG. 3 is a diagram illustrating an example of a conventional technical problem. As shown in FIG. 3, in the optical element of the prior art including Patent Document 1, when focusing on the light-emitting surface / opposing surface of the optical element, the boundary between the light-emitting surface / opposing surface and the end of the bonding layer is exposed. Moreover, the end of the bonding layer is recessed relative to the light-emitting surface / opposing surface of the optical element. As a result, unevenness occurs on the surface of the optical element, and the image displayed on the display device may be degraded and may be visually recognized by the user. Incidentally, even if the manufacturing method of the optical element does not involve cutting the optical element, unevenness may occur at the boundary between the light-emitting surface / opposing surface of the optical element and the end of the bonding layer.

[0027] <Embodiments of the present invention> In this embodiment, the above-mentioned problem is regarded as an important technical issue, and it is possible to realize an optical element and a display device, as well as a method for manufacturing an optical element, that have a structure for obtaining high-quality images even if unevenness occurs at the boundary between the exit surface / opposing surface of the optical element and the end of the bonding layer.

[0028] More specifically, at the light exit surface of the optical element, a plane including a boundary between the light exit surface and one end of the multiple bonding layers is covered with a first covering portion. Alternatively / additionally, at the surface opposite the light exit surface of the optical element, a plane including a boundary between the opposing surface and the other end of the multiple bonding layers is covered with a second covering portion. That is, at least one of the following is satisfied: the plane including the boundary between the light exit surface of the optical element and one end of the multiple bonding layers is covered with a first covering portion, and the plane including the boundary between the opposing surface of the optical element and the other end of the multiple bonding layers is covered with a second covering portion.

[0029] 4 is a diagram showing an example of the surface shapes of the light-emitting surface and the opposing surface of the optical member of this embodiment. As shown in FIG. 4, by filling the boundary (unevenness) between the light-emitting surface / opposing surface of the optical member and the end of the bonding layer with the covering portion (by making the covering portion penetrate into the minute unevenness), it is possible to obtain a high-quality image. For example, it is possible to prevent the unevenness formed on the light-emitting surface / opposing surface of the optical member from being visually recognized as a line.

[0030] 5 is a diagram showing an example of the configuration of an optical member 50 of this embodiment. The optical member 50 is used in a display device (head-mounted display 1) and guides image light from an image display element 10 that displays an image.

[0031] The optical member 50 has an incident surface 51 through which image light is incident from a first direction, an exit surface 52 through which the image light is exited from a second direction perpendicular to the first direction, a plurality of partially reflective surfaces 53 arranged side by side in the first direction and transmitting a portion of the light beam contained in the image light and reflecting the other portion, and a plurality of bonding layers 55 formed corresponding to the plurality of partially reflective surfaces 53. Furthermore, an opposing surface 54 is formed on the surface opposite to the exit surface 52 of the optical member 50. In the example of FIG. 5, three partially reflective surfaces 53 arranged side by side in the first direction are depicted, and three bonding layers 55 corresponding to these three partially reflective surfaces 53 are depicted.

[0032] As will be described in detail later, the optical member 50 is manufactured, for example, by stacking a plurality of transmitting flat plates each coated to form a partially reflective surface, bonding adjacent transmitting flat plates among the plurality of transmitting flat plates to form a bonded body, and then cutting out from this bonded body a body having an incident surface 51, an exit surface 52, a plurality of partially reflective surfaces 53, an opposing surface 54, and a plurality of bonding layers 55. In other words, the plurality of partially reflective surfaces 53 and the plurality of bonding layers 55 of the optical member 50 are each integrated.

[0033] On the exit surface 52 of the optical member 50, a plane including a boundary between the exit surface 52 and one end (lower end in the figure) of the plurality of bonding layers 55 (for example, the entire surface of the exit surface 52 of the optical member 50) is covered with a first covering portion 56. On the opposing surface 54 of the optical member 50, a plane including a boundary between the opposing surface 54 and the other end (upper end in the figure) of the plurality of bonding layers 55 (for example, the entire surface of the opposing surface 54 of the optical member 50) is covered with a second covering portion 57.

[0034] The main body of the optical element 50, which has an incident surface 51, an exit surface 52, a plurality of partially reflective surfaces 53, an opposing surface 54, and a plurality of bonding layers 55, is formed by stacking a plurality of coated transmissive flat plates that form the plurality of partially reflective surfaces 53, bonding adjacent transmissive flat plates together to form a plurality of bonding layers, and then cutting out the laminate into the shape of the main body.

[0035] 6A, 6B, and 6C are process diagrams showing an example of a method for manufacturing the optical member 50 of this embodiment.

[0036] As shown in FIG. 6A, multiple transmission flat plates, each coated with a partially reflective surface, are stacked. Adjacent transmission flat plates are then bonded together to form a bonded assembly. The boundaries between the multiple transmission flat plates form a bonding layer and a partially reflective surface. Then, a main body of an optical element 50, which includes an incident surface 51, an exit surface 52, multiple partially reflective surfaces 53, an opposing surface 54, and multiple bonding layers 55, is cut out from the bonded assembly. In FIG. 6A, the cutting area for cutting out the main body from the bonded assembly is exemplarily depicted by a dashed line.

[0037] 6B illustrates a main body portion cut out from the bonded body. The main body portion has an incident surface 51 through which image light enters, an exit surface 52 through which the image light exits, and a plurality of bonding layers 55 integrally formed with a plurality of partially reflective surfaces 53 that reflect the image light incident from the incident surface 51 toward the exit surface 52. An opposing surface 54, which is the surface on the opposite side of the exit surface 52 with the plurality of bonding layers 55 sandwiched therebetween, can also be interpreted as a transmitting surface, and transmits external information (e.g., scenery, etc.) toward the exit surface in a manner that allows it to be superimposed on the image light reflected by the plurality of partially reflective surfaces 53.

[0038] 6C , on the exit surface 52 of the optical member 50, a plane including a boundary between the exit surface 52 and one end (the end on the lower surface in the figure) of the plurality of bonding layers 55 is covered with a first covering portion 56. On the opposing surface 54 of the optical member 50, a plane including a boundary between the opposing surface 54 and the other end (the end on the upper surface in the figure) of the plurality of bonding layers 55 is covered with a second covering portion 57.

[0039] In this way, multiple transmitting plates are prepared, and an adhesive is applied to their surfaces, and they are stacked and bonded to form a rectangular parallelepiped. Here, the layer made of adhesive is referred to as the bonding layer. The transmitting plates are plates made of optical material, and by applying a coating that functions as a partially reflective surface to one of the surfaces of the transmitting plates that contact each bonding layer in advance, it is possible to form partially reflective surfaces that are parallel to each other. After cutting the rectangular parallelepiped so that the partially reflective surfaces are at the desired angle relative to the exit surface, the surfaces of the surface where the image light enters and exits, and the transmitting surface (opposing surface) that faces approximately normal to the exit surface, are ground and polished.

[0040] The amount of polishing Δh is proportional to the relative speed ν with the tool, pressure p, and time Δt, with the proportionality constant μ being the "specific polishing amount-pressure ratio" determined by each material, and is calculated using the following formula. (1)Δh=μ×ν×p×Δt

[0041] Assuming that the adhesive layer and the transparent plate are flush with each other on the substrate before polishing, the difference between the adhesive's proportional constant μa and the transparent substrate's proportional constant μp is multiplied by a proportional term to produce a difference in the amount of polishing. As polishing progresses, the unevenness affects pressure changes, so the depth of the unevenness does not increase proportionally. However, unless pressure is controlled according to the polishing location, it is difficult to eliminate the occurrence of minute unevenness. If there are unevenness on the exit surface or opposing surface (transmitting surface) after polishing, the unevenness will be visible as a line when viewing the transmitted light, obstructing the view of the image light or the outside world.

[0042] In the manufacturing method of the optical member exemplified above, the main body is cut out by cutting from a bonded assembly of transmissive flat plates, and this cutting is one of the causes of the generation of irregularities. However, the manufacturing method of the optical member does not necessarily require cutting; for example, it is possible to use a method in which transmissive flat plates are bonded and laminated in a shape optimized in advance to match the shape of the target optical member (the bonded assembly can be used as the optical member without requiring cutting). Even when cutting is not performed, some degree of irregularities may occur.

[0043] Next, we will explain the coating. The coating is formed on the surface of the emission surface and the opposing surface (transmission surface) of the main body. An adhesive is used for the coating, and when the adhesive is applied evenly to the polished surface, it penetrates into the minute irregularities and fills them in. A thin plate of glass or resin is then bonded on top of this and allowed to harden. This reduces scattering at the irregularities, so the irregularities are no longer visible when viewing the transmitted light.

[0044] The unevenness will be several tens of microns deep, so to cover it, the adhesive should preferably be 20 microns thick or more, with a viscosity of 1000 MPa·s or less so that it can penetrate the uneven surface. Also, to avoid the influence of the difference in refractive index with the transmitting plate, it is desirable that the refractive index of the adhesive be about ±5% of the refractive index of the transmitting plate.

[0045] In the above example, a thin plate of glass or resin is bonded after applying an adhesive, but the covering portion may be formed using only an adhesive without bonding a thin plate. This allows the covering portion to be thinner. Alternatively, instead of using an adhesive, a resin such as polymethyl methacrylate (PMMA) may be formed on the surface layer of the main body portion using a cell casting method. By forming the covering portion using a cell casting method, it is possible to make it thinner than when a thin plate is attached.

[0046] In this way, there is a degree of freedom in the method of forming the covering portions (first and second covering portions), and various design changes are possible. For example, the covering portions (first and second covering portions) may be made of an adhesive. Also, the covering portions (first and second covering portions) may be made by adhering a transparent member. In this case, the transparent member may be made of a resin material. Furthermore, the covering portions (first and second covering portions) may be made by cell-cast molding of a resin material.

[0047] The reflectance of the plurality of partially reflective surfaces 53 for S-polarized light (at an incident angle of 45°) is preferably higher than the reflectance of the plurality of partially reflective surfaces 53 for P-polarized light (at an incident angle of 45°). This allows for easy coating to be performed for forming the plurality of partially reflective surfaces 53. When light is incident at an angle on the interface between two materials with different refractive indices, the reflectance differs between the polarized component whose electric field vibration direction is parallel to the incident plane (P-polarized light) and the polarized component whose electric field vibration direction is perpendicular to the incident plane (S-polarized light). Generally, at an incident angle of 45°, the reflectance of S-polarized light is easier to make higher than that of P-polarized light. Furthermore, the number of materials that can be coated onto resin materials is limited, and coating can be easily performed by forming a partially reflective surface whose reflectance of S-polarized light is higher than that of P-polarized light.

[0048] The thickness of the optical member 50 from the light-emitting surface 52 to the opposing surface 54 is preferably 5 mm or less. This allows the optical member 50 to be made lighter.

[0049] 7A and 7B are diagrams showing other embodiments of the configuration of the first covering portion 56 and the second covering portion 57. In the above-mentioned Fig. 5, the first covering portion 56 and the second covering portion 57 have a flat plate shape in cross section that does not have power, but in Fig. 7A and 7B, the first covering portion 56 and the second covering portion 57 have either positive or negative power.

[0050] 7A, the first covering portion 56 forms a concave surface 56X having negative power. By forming a curvature in the first covering portion 56 on the side of the exit surface 52 to give it negative power, it is possible to appropriately set the virtual image distance.

[0051] In FIG. 7B , the first covering portion 56 forms a concave surface 56X having negative power, and the second covering portion 57 forms a convex surface 57X ​​having positive power. By forming a curvature on the first covering portion 56 on the side of the exit surface 52 to give it negative power, it is possible to appropriately set the virtual image distance. Furthermore, by forming a curvature on the second covering portion 57 on the side of the opposing surface 54 to give it positive power, it is possible to appropriately set the appearance of the outside world. By making the first covering portion 56 have negative power, the virtual image distance can be adjusted to an appropriate distance, but the object distance of the outside world viewed through the optical member 50 also changes. Therefore, by making the second covering portion 57 have positive power, it is possible to appropriately adjust the object distance of the outside world. Furthermore, in the case of a glasses-type head-mounted display, a design that is more similar to glasses is more likely to be achieved if the second covering portion 57 has a convex surface having positive power.

[0052] 8A and 8B are diagrams illustrating another embodiment of the configuration of the optical element 50. In FIGS. 8A and 8B, the main body of the optical element 50 is provided with partial cross sections in two directions having different shapes, and the arrows in the figures schematically indicate the rays of image light. In FIGS. 8A and 8B, the optical element 50 is configured by bonding (adhering) a main body 60 and a main body 70. When image light enters the main body 60 through the incident surface 61, the main body 60 repeatedly reflects and transmits the image light in the X direction (the vertical direction in FIG. 8A, the direction perpendicular to the paper surface in FIG. 8B) before allowing the image light to enter the main body 70. The main body 70 has multiple partially reflective surfaces 71. The image light from the main body 60 repeatedly reflects and transmits the image light in the Y direction (the horizontal direction in FIGS. 8A and 8B) before exiting from the exit surface 72. In Figure 8B, on the exit surface 72 of the main body 70, a plane including the boundary between the exit surface 72 and one end (the lower end in the figure) of the multiple partially reflecting surfaces 71 is covered by a first covering portion, and a plane including the boundary between the opposing surface 73 and the other end (the upper end in the figure) of the multiple partially reflecting surfaces 71 is covered by a second covering portion.

[0053] Similar to the manufacturing method of the main body 60, 70 of the optical element 50 described above, the main body 60, 70 is manufactured by laminating and bonding transmissive flat plates, cutting them, and grinding and polishing the incident surface, the exit surface, and the opposing surface (transmission surface) to form the extension portions (horizontal extension portion, vertical extension portion). At this time, the ends of the multiple partially reflective surfaces 71 of the main body 70 are exposed to the exit surface 72 and the opposing surface 73. Therefore, unevenness also occurs in the bonding layer of the extension portion (horizontal extension portion) during polishing. After bonding the extension portion (horizontal extension portion) to the main body with an adhesive, coating portions (first and second coating portions) are formed on the surface layers of the exit surface and the opposing surface (transmission surface). The coating portions (first and second coating portions) soak into and fill in the unevenness, thereby obtaining a high-quality image in which the unevenness is not visible.

[0054] <Specific numerical examples> 9A and 9B are cross-sectional views showing an optical system (optical system) for a virtual image display device according to a specific numerical example. In FIGS. 9A and 9B, a three-dimensional space is defined by mutually orthogonal axes ax, ay, and az. This three-dimensional space does not necessarily coincide with the three-dimensional space defined by the x, y, and z axes described above (they are defined as separate three-dimensional spaces). FIG. 9A shows the ay-az cross section of the optical system for a virtual image display device, and FIG. 9B shows the ax-ay cross section of the optical system for a virtual image display device.

[0055] The optical path of a ray emitted from the center of the effective pixel area of ​​the image display element 10 in a direction perpendicular to the pixel array surface is defined as the "optical axis." This optical axis is also the optical axis of the optical system for a virtual image display device (optical system), and also the optical axis of each optical element included in the optical system for a virtual image display device (optical system) (for example, optical member 50, first optical system 80, and second optical system 90, which will be described later).

[0056] The optical system for a virtual image display device (optical system) functions as a virtual image display device or a head-mounted display when used in combination with an image display element 10. The optical system for a virtual image display device (optical system) has an optical member 50, a first optical system 80, and a second optical system 90. When the optical system for a virtual image display device (optical system) is mounted on the head-mounted display 1 shown in FIG. 1, the optical member 50 is provided in the lens unit 3. The first optical system 80 and the second optical system 90 may also be embedded in the center portion of the frame unit 2 (the portion that rests on the wearer's nose).

[0057] The image display element 10 emits image light toward the negative side of the ay axis (from left to right in FIGS. 9A and 9B).

[0058] The first optical system 80 passes the image light from the image display element 10. In the example of FIGS. 9A and 9B, the first optical system 80 is composed of a negative lens, a positive lens, a positive lens, a diaphragm, a negative lens, and a positive lens. In the first optical system 80, an intermediate image is formed and focused toward the negative side of the ay axis (from left to right in FIGS. 9A and 9B) while passing the image light from the image display element 10, and the intermediate image is incident on the incident surface 51 of the optical member 50.

[0059] The optical member 50 has a plurality of partially reflective surfaces 53 that have the function of transmitting and reflecting image light (seven partially reflective surfaces 53 are provided in FIGS. 9A and 9B as an example). The plurality of partially reflective surfaces 53 transmit the image light from the first optical system 80 toward the negative side of the ay axis (from left to right in FIGS. 9A and 9B). A convex surface shaped toward the second optical system 90 is formed on the surface of the optical member 50 that faces the second optical system 90 (the surface on the opposite side of the ay axis from the incident surface 51).

[0060] The second optical system 90 collimates (converts into parallel light) the intermediate image formed (imaged) by the first optical system 80 by passing the image light from the multiple partially reflecting surfaces 53 of the optical member 50, and then reflects the image light toward the positive side of the ay axis (from right to left in FIGS. 9A and 9B). The second optical system 90 has an optical element (positive lens) with a reflecting surface (reflecting function).

[0061] The plurality of partially reflecting surfaces 53 of the optical element 50 reflect the image light from the second optical system 90 toward the positive side of the az axis (from the upper side to the lower side in FIG. 9A, from the back side to the front side of the page in FIG. 9B), and emits the image light from the emission surface 52 of the optical element 50. This allows the image light to reach the wearer's eyes, and an eyebox is formed.

[0062] A plurality of bonding layers 55 are provided corresponding to the plurality of partially reflecting surfaces 53. As described with reference to Figures 4, 5, 6C, 7A, 7B, etc., at exit surface 52 of optical element 50, a plane including a boundary between exit surface 52 and one end of the plurality of bonding layers 55 is covered with a first covering portion 56, and at opposing surface 54 of optical element 50, a plane including a boundary between opposing surface 54 and the other end of the plurality of bonding layers 55 is covered with a second covering portion 57.

[0063] In a numerical example, the vertical, horizontal, and diagonal angles of view of the virtual image are 20.7 degrees, 34.5 degrees, and 39.4 degrees, respectively. The thickness of the optical member 50 from the exit surface 52 to the opposing surface 54 is 5 mm (since the condition of 5 mm or less is satisfied, the optical member 50 can also be made lighter). The virtual image distance is 0.5 m.

[0064] The dimensions of the image display element 10 in the vertical direction (X-axis direction), horizontal direction (Y-axis direction), and diagonal direction are as follows. Vertical direction (X-axis direction): 3.3mm Horizontal direction (Y-axis direction): 5.8mm Diagonal: 6.67mm

[0065] Table 1 shows lens data of the optical system (optical system) for a virtual image display device in the numerical example of FIGS. 9A and 9B. [Table 1]

[0066] In Table 1, Ry (unit: mm) indicates the radius of curvature (or paraxial radius of curvature) of each surface of the optical element along the y-axis (the y-axis perpendicular to the optical axis), and Rx (unit: mm) indicates the radius of curvature (or paraxial radius of curvature) of each surface of the optical element along the x-axis (the x-axis perpendicular to the optical axis). Furthermore, Nd indicates the refractive index of the d-line (wavelength 587.562 nm), and νd indicates the Abbe number of the d-line (wavelength 587.562 nm). The product names and manufacturers of the materials of the optical element are listed in the column to the right of the Abbe number.

[0067] Number 0 in the table indicates the image display surface (pixel array surface) of the image display element 10. Numbers 1 and 2 in the table indicate the surfaces of the cover glass provided on the image display element 10. The cover glass is a glass member that covers the image display surface of the image display element 10.

[0068] Numbers 3 to 13 in the table indicate the optical surfaces of the first optical system 80. Number 9 in the table indicates the aperture stop. Numbers 14 to 21 in the table indicate the optical surfaces through which the image light passes from the entrance surface 51 of the optical member 50 until it is emitted from the exit surface 52. The distance D in number 21 indicates the eye relief.

[0069] The notation A in the column for spacing D numbered 19 in the table indicates the distance in the optical axis direction from the surface (opposite surface) opposite to incident surface 51 of optical element 50 to each partially reflective surface 53 (each of the seven partially reflective surfaces). For convenience, this distance is referred to as distance A. The distances A are -21 mm, -20 mm, -19 mm, -18 mm, -17 mm, -16 mm, and -15 mm for the seven partially reflective surfaces 53, in order from the one closest to incident surface 51 of optical element 50. In other words, the seven partially reflective surfaces 53 are arranged at equal intervals of 1 mm.

[0070] In Table 1, surfaces marked with "**" are anamorphic aspherical surfaces with anamorphic power. The shape of an anamorphic aspherical surface is expressed by the following equation, where Cx is the paraxial curvature on the x-axis (1 / Rx), Cy is the paraxial curvature on the y-axis (1 / Ry), X (unit: mm) is the height on the x-axis from the optical axis, Y (unit: mm) is the height on the y-axis from the optical axis, Kx is the conic coefficient on the x-axis, Ky is the conic coefficient on the y-axis, AR4, AR6, ... are rotationally symmetric coefficients of even order or higher, and AP4, AP6, ... are rotationally asymmetric coefficients of even order or higher.

[0071] Z=(CxX 2 + CyY 2 ) / {1+√(1-(1+Kx)Cx 2 X 2 -(1+Ky)Cy 2 Y 2 )} +AR4·((1-AP4)X 2+(1+AP4)Y 2 ) 2 +AR6·((1-AP6)X 2 +(1+AP6)Y 2 ) 3 +AR8·((1-AP8)X 2 +(1+AP8)Y 2 ) 4 +AR 10 ·((1-AP 10 )X 2 +(1+AP 10 )Y 2 ) 5

[0072] Table 2 shows data for each aspheric surface in the numerical example. [Table 2]

[0073] Table 3 shows the surface shape data of the opposing surface 54 of the optical member 50 in the numerical example. [Table 3]

[0074] 10A and 10B are diagrams of lateral aberration when image light from the image display element 10 passes through an optical system for a virtual image display device (first optical system 80, optical element 50, second optical system 90) in a numerical example. FIG. 11 is a diagram of lateral aberration when light from an object at infinity passes through the optical element 50 in a numerical example. These aberration diagrams are calculated for an image formed using an ideal lens with a focal length of 17 mm. The aberrations in the numerical example are corrected to a high level. It is clear from this numerical example that the optical system for a virtual image display device (optical system) can ensure very good image performance.

[0075] The above is a description of exemplary embodiments of the present invention. The embodiments of the present invention are not limited to those described above, and various modifications are possible within the scope of the technical concept of the present invention. For example, the embodiments of the present application also include appropriate combinations of embodiments explicitly shown in the specification or obvious embodiments.

[0076] The inventions described in the claims of the present application as originally filed are as follows: [Appendix 1] An optical member used in a display device, which guides image light from an image display element that displays an image, an incident surface onto which the image light is incident from a first direction; an exit surface from which the image light exits in a second direction perpendicular to the first direction; a plurality of partially reflecting surfaces arranged side by side in the first direction, each of which transmits a portion of a light beam included in the image light and reflects another portion; a plurality of bonding layers formed corresponding to the plurality of partially reflective surfaces; and At least one of the following is satisfied: on the light exit surface, a plane including a boundary between the light exit surface and one end of the plurality of bonding layers is covered with a first covering portion; and on a surface opposite to the light exit surface, a plane including a boundary between the opposing surface and the other end of the plurality of bonding layers is covered with a second covering portion. An optical element characterized by: [Appendix 2] On the light-emitting surface, a plane including a boundary between the light-emitting surface and one end of the plurality of bonding layers is covered by the first covering portion, and on the opposing surface, a plane including a boundary between the opposing surface and another end of the plurality of bonding layers is covered by the second covering portion. 2. The optical element according to claim 1, [Appendix 3] The main body of the optical member having the incident surface, the exit surface, the plurality of partially reflecting surfaces, and the plurality of bonding layers is a plurality of transmission flat plates each having a coating that serves as the partially reflective surface, and then adjacent transmission flat plates are joined together to form the joining layer, and the joining layer is then cut out into the shape of the main body portion; 3. The optical member according to claim 1 or 2, [Appendix 4] The first and second covering portions are made of adhesive. 4. The optical element according to claim 1, wherein the optical element is a polyimide. [Appendix 5] The first and second covering portions are formed by bonding transparent members. 4. The optical element according to claim 1, wherein the optical element is a polyimide. [Appendix 6] The transparent member is made of a resin material. 6. The optical element according to claim 5, [Appendix 7] The first and second covering portions are formed by cell casting of a resin material. 4. The optical element according to claim 1, wherein the optical element is a polyimide. [Appendix 8] The reflectance of the plurality of partially reflective surfaces for S-polarized light (at an incident angle of 45°) is higher than the reflectance of the plurality of partially reflective surfaces for P-polarized light (at an incident angle of 45°). 8. The optical element according to claim 1, wherein the optical element is a polyimide. [Appendix 9] a plane including a boundary between the light emitting surface and one end of each of the bonding layers is covered with the first covering portion, the first covering portion forms a concave surface having negative power; 9. The optical element according to any one of claims 1 to 8, [Appendix 10] a plane including a boundary between the opposing surface and another end of the plurality of bonding layers is covered by the second covering portion, the second covering portion forms a convex surface having positive power; 10. The optical element according to any one of claims 1 to 9, [Appendix 11] by grinding or polishing at least one of the entrance surface and the exit surface, an extension portion is formed that extends the exit pupil of the image light with respect to the user's line of sight. 11. The optical element according to claim 1, wherein the optical element is a polyimide. [Appendix 12] The thickness of the optical member from the light exit surface to the opposing surface is 5 mm or less. 12. The optical element according to claim 1, wherein the optical element is a polyimide. [Appendix 13] An optical element according to any one of Supplementary Note 1 to Supplementary Note 12, A display device characterized by: [Appendix 14] A method for manufacturing an optical member that is used in a display device and guides image light from an image display element that displays an image, comprising: stacking a plurality of transmissive flat plates with coatings that provide partially reflective surfaces; bonding adjacent transmission flat plates of the plurality of transmission flat plates to form a bonded body; cutting out from the bonded body a main body portion having an incident surface on which the image light is incident from a first direction, an exit surface on which the image light is exited from a second direction orthogonal to the first direction, a plurality of partially reflecting surfaces arranged side by side in the first direction and transmitting a part of a light beam included in the image light and reflecting another part, and a plurality of bonding layers formed corresponding to the plurality of partially reflecting surfaces; a step of covering, on the light emitting surface, a plane including a boundary between the light emitting surface and one end of the plurality of bonding layers with a first covering portion, and a step of covering, on a surface opposite to the light emitting surface, a plane including a boundary between the opposing surface and another end of the plurality of bonding layers with a second covering portion; A method for manufacturing an optical member, comprising: [Explanation of symbols]

[0077] 1. Head-mounted display (virtual image display, display device) 2 Frame section 3 Lens section 10 Image display element 50 Optical components (light guide components) 51 Incidence plane 52 Exit surface 53 Partially reflective surface 54 Opposite Surface 55 Bonding layer 56 First covering part 56X concave 57X Convex 57 Second covering part 60 Main body 61 Incidence plane 62 Partially reflective surface 70 Main body 71 Partially reflective surface 72 Exit surface 73 Opposite Surface 80 1st optical system 90 Second optical system

Claims

1. An optical member used in a display device, which guides image light from an image display element that displays an image, an incident surface onto which the image light is incident from a first direction; an exit surface from which the image light exits in a second direction perpendicular to the first direction; a plurality of partially reflecting surfaces arranged side by side in the first direction, the partially reflecting surfaces transmitting a part of a light beam included in the image light and reflecting another part of the light beam; a plurality of bonding layers formed corresponding to the plurality of partially reflective surfaces; and At least one of the following is satisfied: on the light exit surface, a plane including a boundary between the light exit surface and one end of the plurality of bonding layers is covered with a first covering portion; and on a surface opposite to the light exit surface, a plane including a boundary between the opposing surface and the other end of the plurality of bonding layers is covered with a second covering portion. An optical member characterized by:

2. On the light-emitting surface, a plane including a boundary between the light-emitting surface and one end of the plurality of bonding layers is covered by the first covering portion, and on the opposing surface, a plane including a boundary between the opposing surface and another end of the plurality of bonding layers is covered by the second covering portion. The optical member according to claim 1 .

3. The main body of the optical member having the incident surface, the exit surface, the plurality of partially reflecting surfaces, and the plurality of bonding layers is a plurality of transmission flat plates each having a coating that serves as the partially reflective surface, and then adjacent transmission flat plates are joined together to form the joining layer, and the joining layer is then cut out into the shape of the main body portion; 3. The optical member according to claim 1 or 2.

4. the first and second covering portions are made of adhesive; 3. The optical member according to claim 1 or 2.

5. The first and second covering portions are formed by bonding transparent members.

3. The optical member according to claim 1 or 2.

6. The transparent member is made of a resin material.

6. The optical member according to claim 5.

7. The first and second covering portions are formed by cell casting of a resin material.

3. The optical member according to claim 1 or 2.

8. The reflectance of the plurality of partially reflective surfaces for S-polarized light (at an incident angle of 45°) is higher than the reflectance of the plurality of partially reflective surfaces for P-polarized light (at an incident angle of 45°).

3. The optical member according to claim 1 or 2.

9. a plane including a boundary between the light exit surface and one end of the plurality of bonding layers is covered by the first covering portion, the first covering portion forms a concave surface having negative power; 3. The optical member according to claim 1 or 2.

10. a plane including a boundary between the opposing surface and another end of the plurality of bonding layers is covered by the second covering portion, the second covering portion forms a convex surface having a positive power; 3. The optical member according to claim 1 or 2.

11. by grinding or polishing at least one of the entrance surface and the exit surface, an extension portion is formed that extends the exit pupil of the image light with respect to the user's line of sight.

3. The optical member according to claim 1 or 2.

12. The thickness of the optical member from the light exit surface to the opposing surface is 5 mm or less.

3. The optical member according to claim 1 or 2.

13. The optical member according to claim 1 or 2, A display device characterized by:

14. A method for manufacturing an optical member that is used in a display device and guides image light from an image display element that displays an image, comprising: stacking a plurality of transmissive flat plates with coatings that provide partially reflective surfaces; bonding adjacent transmission flat plates of the plurality of transmission flat plates to form a bonded body; cutting out from the bonded body a main body portion having an incident surface on which the image light is incident from a first direction, an exit surface on which the image light is exited from a second direction orthogonal to the first direction, a plurality of partially reflecting surfaces arranged side by side in the first direction and transmitting a part of a light beam included in the image light and reflecting another part, and a plurality of bonding layers formed corresponding to the plurality of partially reflecting surfaces; a step of covering a plane including a boundary between the emission surface and one end of the plurality of bonding layers with a first covering portion on the emission surface, and a step of covering a plane including a boundary between the opposing surface and another end of the plurality of bonding layers with a second covering portion on the opposing surface of the emission surface; A method for manufacturing an optical member, comprising:

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