Light guide member, optical system, and display device

Abstract

To provide a light guide member, an optical system, and a display device capable of displaying a bright image by increasing the quantity of light directed toward an eye box.SOLUTION: In a light guide member for guiding incident light, multiple first partial reflection surfaces that transmit first luminous flux that is one portion of luminous flux included in the light and reflect second luminous flux that is the other portion of the light are provided in the light guide member, the multiple first partial reflection surfaces are disposed side by side in a second direction orthogonal to a first direction and constitute a first partial reflection surface group when a direction in which the light is incident to the light guide member is defined as the first direction, and the light is simultaneously incident to the multiple first partial reflection surfaces when the light is incident to the first partial reflection surface group.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a light guide member, an optical system, and a display device. [Background technology]

[0002] For example, in recent years, head mounted displays (HMDs) have become widely used as display devices, and small, see-through HMDs similar to glasses have been developed. A technology is also known that arranges an image display element near the glass part of glasses to reduce the size of the glasses. Glass devices such as smart glasses that allow the observer to observe a virtual image superimposed on a landscape or the like, and head mounted displays (HMDs) are also known. Furthermore, glass devices that can accommodate the wearer's eye movements and differences in interpupillary distance are becoming more common.

[0003] For example, Patent Document 1 describes a head mounted display device having a display, a first waveguide element, and a second waveguide element. The display provides an image light beam, which is projected onto a projection target. The first waveguide element includes a first light entrance surface, a first light exit surface, and a plurality of first light splitting elements, the image light beam from the display enters the first waveguide element via the first light entrance surface, the image light beam converges at a first aperture in the first waveguide element, the image light beam leaves the first waveguide element via the first light exit surface, and the first aperture is located within the first waveguide element. The second waveguide element includes a second light entrance surface, a second light exit surface, and a plurality of second light splitting elements, the image light beam from the first waveguide element enters the second waveguide element via the second light entrance surface, and the image light beam leaves the second waveguide element via the second light exit surface. Before the main image light beam is guided to the second waveguide element by the plurality of first light splitting elements, the main image light beam is prevented from undergoing total reflection in the first waveguide element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6952587 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the inventors' intensive research, the head mounted display device of Patent Document 1 has room for improvement in terms of increasing the amount of light directed toward the eyebox and displaying a bright image.

[0006] The present invention has been made based on the above-mentioned awareness of the problems, and aims to provide a light-guiding member, an optical system, and a display device that can increase the amount of light directed toward the eye box to display a bright image. [Means for solving the problem]

[0007] The light-guiding member of the present invention is a light-guiding member that guides incident light, and has within the light-guiding member a plurality of first partial reflective surfaces that transmit a first light flux that is a portion of the light flux contained in the light and reflect a second light flux that is the other portion of the light, and when the direction in which the light is incident on the light-guiding member is defined as a first direction, the plurality of first partial reflective surfaces are arranged side by side in a second direction perpendicular to the first direction and constitute a first partial reflective surface group, and the light is incident on the plurality of first partial reflective surfaces simultaneously when it enters the first partial reflective surface group. Effect of the Invention

[0008] According to the present invention, it is possible to provide a light guide member, an optical system, and a display device that can increase the amount of light directed toward the eye box to display a bright image. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a head-mounted display, which is an example of a virtual image display device according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a conceptual diagram showing an example of a technical problem in conventional exit pupil expansion. [Diagram 3]FIG. 4 is a conceptual diagram showing an example of exit pupil expansion according to the present embodiment. [Figure 4] 1 is a conceptual diagram illustrating an example of a light guide member, an optical system, and a display device according to an embodiment of the present invention. [Diagram 5] 10 is a diagram illustrating optical paths of on-axis and off-axis light beams of image light incident on a light-guiding member with respect to a first partially reflecting surface group. FIG. [Figure 6] 13 is a diagram showing an eye box formed by image light reflected by the second partially reflective surface group. FIG. [Figure 7] 1 is a cross-sectional view showing an optical system for a virtual image display device according to a first numerical example. [Figure 8] 4 is a diagram showing an example of an illuminance distribution on the retina of a wearer by the optical system for a virtual image display device of Numerical Example 1. FIG. [Figure 9] FIG. 11 is a cross-sectional view showing an optical system for a virtual image display device according to a second numerical example. [Figure 10] 13 is a diagram showing an example of an illuminance distribution on the retina of a wearer by the optical system for a virtual image display device according to Numerical Example 2. FIG. [Figure 11] FIG. 11 is a cross-sectional view showing an optical system for a virtual image display device according to a numerical example 3. [Figure 12] FIG. 11 is a diagram showing an example of an illuminance distribution on the retina of a wearer by the optical system for a virtual image display device according to Numerical Example 3. [Figure 13] FIG. 11 is a cross-sectional view showing an optical system for a virtual image display device according to Numerical Example 4. [Figure 14] FIG. 13 is a diagram showing an example of an illuminance distribution on the retina of a wearer by the optical system for a virtual image display device according to Numerical Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an optical system for a virtual image display device, a virtual image display device, and a head-mounted display according to an embodiment of the present invention will be described with reference to the drawings. In the following description, common or corresponding elements are denoted by the same or similar reference symbols, and duplicated descriptions are appropriately simplified or omitted. Here, the "optical system for a virtual image display device" may be read as an "optical system", and the "virtual image display device" and "head-mounted display" may be read as a "display device".

[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 10 (light associated with a virtual image) is called the image light, but the image light may also be read as "light" guided by the light-guiding member 50.

[0012] In this specification, the "first direction" and the "second direction" are defined as follows. That is, the direction in which the image light (light) from the image display element 10 enters the light-guiding member 50 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. 4B (the left-right direction in FIG. 4B). The "second direction" corresponds to the negative side of the x direction in FIG. 4B (the up-down direction in FIG. 4B).

[0013] <Outline of head-mounted display configuration> 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. In addition, the head mounted display is a virtual image display device in a form 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 glasses-type wearable terminals. The 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. Note that the lens unit 3 includes at least a light guiding member 50, a first partial reflection surface group 51, and a second partial reflection surface group 52 as an optical system.

[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 a wearer.

[0017] An image display element 10 for displaying 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 illustrated 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 be used in a concept including 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 on the wearer's ear) instead of the portion depicted by reference numeral 10 in FIG. 1.

[0018] The image display element 10 is an element that displays an image to be observed as a virtual image, and is, for example, an OLED (Organic Light Emitting Diode) array, an LD (Laser Diode) array, an LED (Light Emitting Diode) array, a MEMS (Micro Electro Mechanical Systems), a DMD (Digital Micromirror Device), etc. The image display element 10 may also be a micro LED, a micro OLED, or an LCOS (Liquid crystal on silicon).

[0019] 1, the first horizontal direction from the lens unit 3 toward the wearer's eye is defined as the z direction, the second horizontal direction perpendicular to the z direction is defined as the x direction, and the vertical direction perpendicular to both the x direction and the z direction is defined 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 the directions are used for convenience in explaining the relative positional relationship of the components, and do not indicate absolute directions. For example, the z direction is not necessarily the horizontal direction, but may be the vertical direction, depending on the posture of the wearer who wears the head mounted display 1.

[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 to 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) for displaying a virtual image. That is, the pair of left and right lens units 3 form eye boxes in areas including the corresponding eyes. More specifically, a light guide member 50 is provided in the lens unit 3, and image light from the image display element 10 is guided to the light guide member 50 from a first direction. The light guide member 50 is formed with a first partial reflection surface group 51 having a plurality of first partial reflection surfaces and a second partial reflection surface group 52 having a plurality of second partial reflection surfaces, and the first partial reflection surface group 51 and the second partial reflection surface group 52 reflect the image light guided to the light guide member 50 from the first direction and emit it to the outside from the second direction of the light guide member (forming an eye box). The first group of partially reflective surfaces 51 and the second group of partially reflective surfaces 52 will be described in detail later.

[0022] <Technical issues with conventional head-mounted displays> For example, the conventional head mounted display including the above-mentioned Patent Document 1, that is, the conventional Exit Pupil Expander (EPE), is a technology that can be applied when the pupil of the incident optical system is located near the partially reflecting surface. Therefore, the distance between the pupil and the eye becomes long, and some light is not incident on the eye box, so there is room for improvement in terms of light utilization efficiency.

[0023] FIG. 2 is a conceptual diagram showing an example of a technical problem of conventional exit pupil expansion (EPE). As shown in FIG. 2, as an incidence method and optical path of image light in conventional partially reflective surfaces (group), for example, first, image light is incident on a certain partially reflective surface, and the light transmitted through the partially reflective surface heads toward the eye box, while the light reflected on the partially reflective surface heads toward the adjacent partially reflective surface, while the light transmitted through the adjacent partially reflective surface heads toward the eye box, and the light reflected on the adjacent partially reflective surface heads toward the eye box, while the light transmitted through the adjacent partially reflective surface heads toward the adjacent partially reflective surface. In this case, there is a risk that the light incident on the eye box will be small and uneven. In addition, the partially reflective surface (group) must be arranged strictly so as not to block the image light (there are large layout constraints). Furthermore, in order to miniaturize the optical system, it is necessary to arrange the exit pupil of the incident optical system in a position close to the partially reflective surface, and the amount of light that does not enter the eye box increases, so there is room for improvement in terms of light utilization efficiency. For example, of the image light (light) depicted by the two solid lines and two dashed lines shown as examples in Figure 2, only the image light (light) depicted by the inner solid line and dashed line contributes to the formation of the eyebox, and the remaining image light (light) depicted by the outer solid line and dashed line becomes wasted light that does not contribute to the formation of the eyebox.

[0024] <Technical Concept of the Light Guide Member, Optical System, and Display Device of the Present Invention> The light guide member, optical system, and display device of the present invention solve the above technical problems, and by designing the pupil of the optical system at the eyebox position, it is possible to reduce wasted light that does not enter the eyebox and improve light utilization efficiency. In other words, it is possible to increase the amount of light directed toward the eyebox and display a bright image.

[0025] The light guide member of this embodiment is a light guide member that guides incident light. The light guide member has a plurality of first partial reflection surfaces that transmit a first light flux, which is a portion of the light flux contained in the light, and reflect a second light flux, which is the other portion of the light. Here, if the direction in which the light enters the light guide member is defined as a first direction, the plurality of first partial reflection surfaces are arranged side by side in a second direction perpendicular to the first direction, forming a first partial reflection surface group. When the light enters the first partial reflection surface group, it is simultaneously incident on the plurality of first partial reflection surfaces.

[0026] The light-guiding member also includes a second group of partial reflecting surfaces onto which light that has passed through the first group of partial reflecting surfaces is incident, and the second group of partial reflecting surfaces is composed of a plurality of second partial reflecting surfaces arranged in a line in the first direction.

[0027] Furthermore, a first light beam transmitted through a first partially reflecting surface n, which is one of the multiple first partially reflecting surfaces, is incident on a second group of partially reflecting surfaces, and a second light beam reflected by the first partially reflecting surface n is further reflected by a first partially reflecting surface n+1 adjacent to the first partially reflecting surface n, and then is incident on the second group of partially reflecting surfaces, where n is a positive integer in this specification.

[0028] The first partially reflective surface group has a plurality of adjacent partially reflective surfaces (e.g., a first partially reflective surface n and a first partially reflective surface n+1 adjacent thereto), and in the first partially reflective surface group, a portion of the image light transmitted through a certain partially reflective surface (e.g., the first partially reflective surface n) is emitted to a projection target to form an eyebox, while another portion of the image light reflected from a certain partially reflective surface (e.g., the first partially reflective surface n) is further reflected by an adjacent partially reflective surface (e.g., the first partially reflective surface n+1) and emitted to a projection target to form an eyebox. In other words, when focusing on one of the first partially reflective surfaces, and defining a portion of the image light transmitted through the partially reflective surface as a first light beam and defining the other portion of the image light reflected from the partially reflective surface as a second light beam, the first and second light beams are delivered to the eye, and the eyebox can be expanded.

[0029] In addition, the image light guided from the first direction to the light guiding member is incident across each of the partial reflecting surfaces (plurality of first partial reflecting surfaces) of the first partial reflecting surface group (plurality of first partial reflecting surfaces), so that the image light is efficiently emitted to the outside to form an eyebox, and as a result, the amount of light directed to the eyebox can be increased to display a bright image. Also, by widening the width of the image light incident on each of the partial reflecting surfaces (plurality of first partial reflecting surfaces) of the first partial reflecting surface group, the amount of light itself can be increased to display a bright image.

[0030] Furthermore, by optimally setting the reflectance of each partial reflective surface (multiple first partial reflective surfaces) of the first partial reflective surface group, it is possible to reduce brightness unevenness and form a high-quality eye box with excellent visibility.

[0031] FIG. 3 is a conceptual diagram showing an example of an exit pupil expander (EPE) according to the present embodiment. As shown in FIG. 3, image light from an image display element is incident on a first partial reflection surface group of a light guide member via an incident optical system. In FIG. 3, three partial reflection surfaces (which may be called first partial reflection surfaces n-1, n, and n+1 in order from the left side to the right side in FIG. 3) are illustrated as the first partial reflection surface group by way of example. In FIG. 3, image light from an image display element is incident across (simultaneously incident on) three partial reflection surfaces (first partial reflection surfaces) of the first partial reflection surface group. Image light depicted as exiting from the center of the image display element is transmitted through the central partial reflection surface (e.g., the first partial reflection surface n) of the first partial reflection surface group, contributing to the formation of an eye box, and is also reflected off the central partial reflection surface of the first partial reflection surface group and reflected off the left partial reflection surface (e.g., the first partial reflection surface n-1) to contribute to the formation of an eye box. The image light depicted as going out from the right end of the image display element passes through the right partial reflecting surface (e.g., the first partial reflecting surface n+1) of the first partial reflecting surface group, contributing to the formation of the eyebox, and also reflects off the right partial reflecting surface of the first partial reflecting surface group and reflects off the central partial reflecting surface (e.g., the first partial reflecting surface n) to contribute to the formation of the eyebox. The image light depicted as going out from the left end of the image display element passes through the central partial reflecting surface (e.g., the first partial reflecting surface n) of the first partial reflecting surface group, contributing to the formation of the eyebox, and also reflects off the central partial reflecting surface of the first partial reflecting surface group and reflects off the left partial reflecting surface (e.g., the first partial reflecting surface n-1) to contribute to the formation of the eyebox. In this way, it can be understood that the image light from the image display element contributes to the formation of the eyebox efficiently without loss. More specifically, in FIG. 3, the image light (solid line) depicted as exiting the center of the image display element, the image light (dashed line) depicted as exiting the right end of the image display element, and the image light (dashed line) depicted as exiting the left end of the image display element contribute to the formation of the eyebox without loss.

[0032] It is preferable that the first group of partially reflective surfaces satisfy the following conditional expression (1). (1) 0%≦Rd<40% however, Rd: the difference in reflectance between any two of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%).

[0033] Conditional formula (1) specifies the difference in reflectance between any two of the multiple first partially reflective surfaces that make up the first partially reflective surface group. For example, if the difference between the highest reflectance and the lowest reflectance among the multiple first partially reflective surfaces that make up the first partially reflective surface group satisfies conditional formula (1), then the difference between any two of the reflectances among the multiple first partially reflective surfaces that make up the first partially reflective surface group will also satisfy conditional formula (1). By satisfying conditional expression (1), it is possible to reduce luminance unevenness and form a high-quality eye box with high visibility. If the upper limit of conditional expression (1) is exceeded, the difference in reflectance between any two of the multiple first partially reflective surfaces that make up the first partially reflective surface group will become too large, resulting in large brightness unevenness, which may degrade the visibility and quality of the eye box.

[0034] The light guiding member includes a second partial reflective surface group into which light having passed through the first partial reflective surface group is incident, and the second partial reflective surface group is composed of a plurality of second partial reflective surfaces arranged side by side in a first direction. By cooperation between the first and second partial reflective surface groups (by forming an eyebox by outputting image light from the first partial reflective surface group to the outside via the second partial reflective surface group), one of the long side and the short side of the rectangular image in the eyebox can be defined (secured) by the first partial reflective surface group, and the other of the long side and the short side of the rectangular image in the eyebox can be defined (secured) by the second partial reflective surface group.

[0035] A first light beam transmitted through a first partially reflective surface n, which is one of the multiple first partially reflective surfaces, is incident on a second partially reflective surface group, and a second light beam reflected by the first partially reflective surface n is further reflected by a first partially reflective surface n+1 adjacent to the first partially reflective surface n and is incident on the second partially reflective surface group. Since the intensity of image light emitted after being reflected and transmitted by a partially reflective surface decreases during transmission, by generating image light (first light beam) transmitted through a partially reflective surface and image light (second light beam) reflected twice between adjacent partially reflective surfaces, it is possible to form a high-quality eye box with high visibility by reducing luminance unevenness.

[0036] The first partially reflective surface group has a plurality of partially reflective surfaces (first partially reflective surfaces) on which light beams having different angles of view of the image light are incident. That is, light beams having different angles of view are incident on different partially reflective surfaces (first partially reflective surfaces) of the first partially reflective surface group. For example, a light beam having a certain angle of view is incident on one partially reflective surface, and a light beam having a different angle of view is incident on another partially reflective surface. This makes it possible to reduce the size of the first partially reflective surface group. If light beams having different angles of view are incident on one partially reflective surface, this leads to an increase in the size of the partially reflective surface.

[0037] It is preferable that the light guide member of the present embodiment satisfies the following conditional expression (2). (2) 1 mm <D<7mm however, D: The spacing between adjacent first partially reflective surfaces among the plurality of first partially reflective surfaces that constitute the first partially reflective surface group.

[0038] By satisfying conditional expression (2), the efficiency of using the image light can be improved, and the amount of light directed toward the eye box can be increased to display a bright image. If the upper limit value of conditional expression (2) is exceeded, the spacing between the transmitting partially reflective surface and the reflecting partially reflective surface in the first partially reflective surface group (the spacing between adjacent first partially reflective surfaces) will be wider than the light beam width, causing the spacing between the light beams at the eye box position to become wider, resulting in missing parts of the image. If the lower limit of conditional expression (2) is exceeded, in the first group of partially reflective surfaces, the distance between the transmitting partially reflective surface and the reflecting partially reflective surface (the distance between adjacent first partially reflective surfaces) will be narrower than the light beam width, causing overlap of the light beams, and therefore the light cannot be spread sufficiently, making it impossible to ensure an eye box.

[0039] Even within the range in which conditional formula (2) is satisfied, if the following conditional formula (2') is satisfied, an even greater effect can be obtained. (2')2mm <D<6mm

[0040] It is preferable that the light guide member of the present embodiment satisfies the following conditional expression (3). (3) 40°<θ1<50° however, θ1: the angle of incidence of light with respect to the first group of partially reflective surfaces.

[0041] By satisfying conditional expression (3), the angle of incidence of the image light with respect to the first partial reflective surface group, and ultimately the spacing and size of the partial reflective surfaces (first partial reflective surfaces) in the first partial reflective surface group can be appropriately set, thereby making it possible to make the light beam passing through the first partial reflective surface group uniform and preventing unevenness in the image light. If the upper limit value of conditional expression (3) is exceeded, the spacing between the partially reflective surfaces (first partially reflective surfaces) in the first group of partially reflective surfaces will become too narrow, causing intensity differences in the light beam transmitted through the partially reflective surfaces, leading to unevenness in the image light. If the lower limit of conditional expression (3) is exceeded, the partially reflective surface (first partially reflective surface) in the first group of partially reflective surfaces will become too large, causing intensity differences in the light beam transmitted through the partially reflective surface, leading to unevenness in the image light.

[0042] It is preferable that the light guide member of the present embodiment satisfies the following conditional expression (4). (4) T1×0.5 <R1×R1<T1×7 however, T1: transmittance of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%), R1: reflectance of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%).

[0043] For example, R1 can be 0.6 and T1 can be 0.4. By satisfying conditional expression (4), the balance between reflected light and transmitted light at the first partially reflective surface group can be appropriately set, making the light flux intensity distribution at the eye box position uniform and preventing image unevenness. If the upper limit value of conditional expression (4) is exceeded, the reflected light from the first partially reflective surface group will become stronger (the intensity of the second light beam will become stronger), which may cause unevenness in the intensity distribution of the light beam at the eye box position and unevenness in the image. If the lower limit of conditional expression (4) is exceeded, the transmitted light in the first partially reflecting surface group will become stronger (the intensity of the first light beam will become stronger), which may cause unevenness in the intensity distribution of the light beam at the eye box position and unevenness in the image.

[0044] It is preferable that the light guide member of the present embodiment satisfies the following conditional expression (5). (5) Ts × 0.5 <Rs×Rs<Ts×7 however, Ts: transmittance of S-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%), Rs: reflectance of S-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%).

[0045] For example, Rs can be 0.6 and Ts can be 0.4. By satisfying conditional expression (5), the balance between reflected light and transmitted light at the first partially reflective surface group can be appropriately set, making the light flux intensity distribution at the eye box position uniform and preventing image unevenness. If the upper limit value of conditional expression (5) is exceeded, the reflected light from the first partially reflective surface group will become stronger (the intensity of the second light beam will become stronger), which may cause unevenness in the intensity distribution of the light beam at the eye box position and unevenness in the image. If the lower limit of conditional expression (5) is exceeded, the transmitted light in the first partially reflecting surface group will become stronger (the intensity of the first light beam will become stronger), which may cause unevenness in the intensity distribution of the light beam at the eye box position and unevenness in the image.

[0046] It is preferable that the light guide member of the present embodiment satisfies the following conditional expression (6). (6) 0%≦Rp<40% however, Rp: reflectance of P-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%).

[0047] By satisfying conditional expression (6), an appropriate amount of light from the outside world is reflected by the first partially reflecting surface group, making it possible to improve visibility. If the upper limit of condition (6) is exceeded, the visibility of the outside world will deteriorate, and light from the outside world will be reflected by the first partially reflective surface group and enter the eyes, resulting in stray light.

[0048] The optical system of this embodiment forms an intermediate image of image light from an image display element that displays an image. For example, a possible mode is one in which a first optical system passes the image light and forms (imaging) an intermediate image of the image light, and a second optical system collimates (makes into parallel light) the intermediate image formed (imaging) by the first optical system.

[0049] The optical system and display device of the present invention include a first optical system, a second optical system, an optical member, and a light guide member. The optical member is provided between the first optical system and the second optical system and in front of the light guide member, and has a partially reflective surface having a function of transmitting and reflecting image light. Image light from an image display element that displays an image enters the first optical system, transmits or reflects the partially reflective surface of the optical member, enters the second optical system, reflects or transmits the partially reflective surface of the optical member, enters the light guide member, and is emitted from the light guide member toward the wearer's eye.

[0050] More specifically, the first optical system passes image light from an image display element that displays an image (forms / focuses an intermediate image). The optical member has a partially reflective surface that has the functions of transmitting and reflecting the image light. The second optical system passes the image light that has passed through the first optical system and been transmitted or reflected by the partially reflective surface of the optical member, and then reflects it back to the optical member (collimating the image light in the process). The light guide member guides the image light that has reflected by the second optical system and been reflected or transmitted by the partially reflective surface of the optical member.

[0051] Here, "transmission or reflection" by the partially reflective surface of the optical member may be read as "one of transmission and reflection," and "reflection or transmission" by the partially reflective surface of the optical member may be read as "the other of transmission and reflection." That is, if the partially reflective surface of the optical member transmits the image light when the image light is guided from the first optical system to the second optical system, the partially reflective surface of the optical member reflects the image light when the image light is guided from the second optical system to the light guiding member. Conversely, if the partially reflective surface of the optical member reflects the image light when the image light is guided from the first optical system to the second optical system, the partially reflective surface of the optical member transmits the image light when the image light is guided from the second optical system to the light guiding member.

[0052] Furthermore, reflection of image light does not necessarily mean total reflection of image light, and may be, for example, reflection of a portion (most portion) of the image light and transmission of the other portion (small portion). Moreover, transmission of image light does not necessarily mean total transmission of image light, and may be, for example, transmission of a portion (most portion) of the image light and reflection of the other portion (small portion).

[0053] The optical member and the light guide member may be separate members, or may be separate members integrated together by bonding or the like, or may be integrally molded as a single member.

[0054] The optical system and display device of the present invention are provided with an optical member having a partially reflective surface between the first optical system and the second optical system and in front of the light guide member, and the image light is transmitted and reflected by the partially reflective surface of the optical member before being guided to the light guide member, so that the image light is emitted to the wearer's eye without traveling back and forth in the first direction of the light guide member, and the image light can be prevented from leaking to the outside. That is, by defining the route (optical path) of the image light to be the first optical system, the optical member, the second optical system, the optical member, and the light guide member, the image light is emitted to the wearer's eye without traveling back and forth in the first direction of the light guide member, and the image light can be prevented from leaking to the outside. Furthermore, by adopting a folding structure of the image light, the optical system and the display device can be made smaller.

[0055] The light guiding member has partial reflection surfaces (first partial reflection surface group, second partial reflection surface group) that guide the image light in a first direction of the light guiding member and reflect the image light to be emitted to the outside from a second direction of the light guiding member (to reach the wearer's eye, forming an eye point). At this time, a part (most of, almost all) of the image light is reflected by the partial reflection surfaces (first partial reflection surface group, second partial reflection surface group) of the light guiding member and emitted to the outside, and the image light does not go back and forth in the first direction of the light guiding member, so that excess light that does not reach the wearer's eye is not emitted in the opposite direction to the wearer's eye, and leakage of the image light to the outside can be suppressed.

[0056] For example, in the conventional technology in which image light travels back and forth in the first direction of the light guide member, the components of the optical system are arranged in series (straight line), and the image light from the image display element enters the first optical system, passes through the polarizing plate, enters the light guide member, passes through the partial reflection surface, passes through the quarter wave plate, enters the second optical system, passes through the quarter wave plate, enters the light guide member, is reflected by the partial reflection surface, and the image light reaches the wearer's eye. At that time, it is considered that the light in the polarization direction passing through the polarizing plate is approximately the same as the polarization direction with low reflectance of the partial reflection surface, so that more light passes through the partial reflection surface and reaches the wearer's eye. However, light leaks due to reflection in the polarization direction with low reflectance of the partial reflection surface.

[0057] In the optical system and display device of the present invention, image light from an image display element that displays an image enters the first optical system, passes through or is reflected by the partially reflective surface of the optical member, enters the second optical system, reflects through or is transmitted by the partially reflective surface of the optical member, enters the light guide member, and is emitted from the partially reflective surface of the light guide member toward the wearer's eye. An optical member having a partially reflective surface is disposed between the first optical system and the second optical system and in front of the light guide member, and the first optical system, the second optical system, and the optical member cooperate to form an intermediate image, so that the exit pupil can be set at an appropriate position. Therefore, a compact optical system can be realized while ensuring an eye box. In particular, an optical member is disposed between the first optical system and the second optical system, and the partially reflective surface of the optical member is utilized to efficiently guide the image light to the light guide member (a light path based on a folding structure of the first optical system → optical member → second optical system → optical member → light guide member is defined), so that the overall length of the optical system can be suppressed, and the optical system and the display device can be made compact.

[0058] Theoretically, it is also possible to separately provide a first optical member corresponding to the first optical system and a second optical member corresponding to the second optical system, so that the image light enters the first optical system, enters the first optical member, passes through its partially reflective surface, enters the second optical system, enters the second optical member, is reflected by its partially reflective surface, enters the light guide member, is reflected by its partially reflective surface, and reaches the wearer's eye. However, in this case, the first optical system, the first optical member, the second optical system, and the second optical member are arranged in series (in a straight line), so that the overall length of the optical system becomes too large, and the optical system and the display device are inevitably enlarged.

[0059] It is preferable that the optical system of this embodiment satisfies the following condition (7). (7) 40% <R0≦60% however, R0: reflectance of the partially reflecting surface of the optical member (incident angle 45°, light absorption 0%).

[0060] By satisfying conditional expression (7), the balance between reflection and transmission of the image light on the partially reflecting surface of the optical member can be appropriately set, thereby optimizing the amount of light entering the light guide member. If the upper limit of conditional expression (7) is exceeded, the light transmitted through the partially reflecting surface of the optical member becomes too weak, resulting in a reduced amount of light entering the light guide member. If the lower limit of condition (7) is exceeded, the light reflected by the partially reflecting surface of the optical member becomes too strong, resulting in a decrease in the amount of light entering the light guide member.

[0061] It is preferable that the optical system of this embodiment satisfies the following conditions (8) and (9). (8)60% <Rs0≦100% (9) 0%≦Rp0<30% however, Rs0: reflectance of S-polarized light of the partially reflective surface of the optical member (incident angle 45°, light absorption 0%), Rp0: reflectance of P-polarized light on the partially reflecting surface of the optical member (incident angle 45°, light absorption 0%).

[0062] By satisfying conditional expressions (8) and (9), the amount of image light reaching the light guide member from the optical member can be increased, thereby improving the light utilization efficiency. If the lower limit of conditional expression (8) is exceeded and / or the upper limit of conditional expression (9) is exceeded, the amount of image light reaching the light guide member from the optical member decreases, resulting in a decrease in light utilization efficiency.

[0063] The optical element may further include a wave plate for switching the polarization of the image light, positioned between the first and second partially reflective surface groups and / or between the optical element and the light guiding element. The wave plate provided between the first and second partially reflective surface groups is preferably a half-wave plate, and the light utilization efficiency can be improved by controlling the polarization to be optimal for the partially reflective surface with the wave plate. The wave plate provided between the optical element and the light guiding element is preferably a half-wave plate, and the light utilization efficiency can be improved by controlling the polarization to be optimal for the partially reflective surface with the wave plate.

[0064] It is preferable that the light guide member of the present embodiment satisfies the following conditional expression (10). (10) Ts' × 0.5 <Rs’×Rs’<Ts’×7 however, Ts': transmittance of any one of the second partially reflective surfaces for S-polarized light (incident angle 45°, light absorption 0%). Rs': reflectance of any one of the second partial reflecting surfaces for S-polarized light (incident angle 45°, light absorption 0%).

[0065] By satisfying conditional expression (10), the balance between the reflected light and the transmitted light at the second partially reflective surface group can be appropriately set while taking polarization into consideration, making it possible to uniform the light flux intensity distribution at the eye box position and preventing image unevenness. If the upper limit value of conditional expression (10) is exceeded, the reflected light from the second partially reflective surface group will become stronger (the intensity of the second light beam will become stronger), which may cause unevenness in the intensity distribution of the light beam at the eye box position and unevenness in the image. If the lower limit of conditional expression (10) is exceeded, the transmitted light in the second partially reflecting surface group will become stronger (the intensity of the first light beam will become stronger), which may cause unevenness in the intensity distribution of the light beam at the eye box position and unevenness in the image.

[0066] The optical system of this embodiment forms an intermediate image of the image light from the image display element, and may include an optical element having an anamorphic surface. By adopting an anamorphic optical system as the optical system that forms the intermediate image, the exit pupil position of the incident optical system can be set to different positions in the horizontal and vertical directions of the image display element, and the image light can be efficiently delivered to the eye while being compact.

[0067] 4A and 4B are conceptual diagrams showing an example of a light guide member, an optical system, and a display device according to this embodiment. As shown in Fig. 4A, image light from an image display element is guided to a first optical system, an optical member (partially reflecting surface), a second optical system, an optical member (partially reflecting surface), and a light guide member. As shown in Fig. 4A and 4B, inside the light guide member, the image light is incident across the first partially reflecting surface group (simultaneously), then incident on the second partially reflecting surface group in sequence, and is emitted to the outside (forming an eye box).

[0068] More specifically, the first partially reflective surface group has a plurality of adjacent first partially reflective surfaces (FIG. 4B exemplarily illustrates three partially reflective surfaces arranged at an interval D), and in the first partially reflective surface group, a portion of the image light transmitted through a certain partially reflective surface (e.g., the first partially reflective surface n) is guided to a projection target (the second partially reflective surface group) to form an eyebox, while another portion of the image light reflected from a certain partially reflective surface is further reflected by an adjacent partially reflective surface (e.g., the first partially reflective surface n+1) and guided to the projection target (the second partially reflective surface group) to form an eyebox. In other words, when focusing on one of the first partially reflective surface groups, and the portion of the image light transmitted through the partially reflective surface is defined as a first light beam, and the other portion of the image light reflected from the partially reflective surface is defined as a second light beam, the first and second light beams are delivered to the eye in a separated form, so that the eyebox can be expanded. In addition, in Figure 4B, on-axis light incident on the central partially reflective surface of the three partially reflective surfaces in the first partially reflective surface group is depicted by a solid line, and off-axis light incident on the peripheral partially reflective surface of the three partially reflective surfaces in the first partially reflective surface group is depicted by a fine dashed line.

[0069] 5A, 5B, and 5C are diagrams illustrating the optical paths of the on-axis and off-axis (peripheral) light beams of image light incident into the light-guiding member with respect to the first partially reflective surface group. In Figs. 5A to 5C, the image light incidence range from the optical member (partially reflective surface) to the light-guiding member (first partially reflective surface group) is illustrated. Fig. 5A illustrates the optical path of the on-axis light incident into the light-guiding member, particularly the optical path of the on-axis light incident into the center side of the three first reflective surface groups arranged in the vertical direction (second direction) in Fig. 5A. Fig. 5B illustrates the optical path of the off-axis light incident into the light-guiding member, particularly the optical path of the off-axis light incident into the upper side of the three first reflective surface groups arranged in the vertical direction (second direction) in Fig. 5B. Figure 5C illustrates the optical path of off-axis light that enters the light-guiding member, in particular, the optical path of off-axis light that enters the lower side of a first group of three reflecting surfaces arranged in the vertical direction (second direction) in Figure 5C.

[0070] 6 is a diagram showing an eyebox formed by image light reflected by the second partially reflective surface group. It can be seen that a suitable eyebox (wide and with uniform luminous intensity) is formed by the cooperation of the first partially reflective surface group (plurality of first partially reflective surfaces) and the second partially reflective surface group (plurality of second partially reflective surfaces).

[0071] <Numerical Example 1> Fig. 7 is a cross-sectional view showing an optical system for a virtual image display device (optical system) of Numerical Example 1. Fig. 7 shows a yz cross section (cross section including the optical axis) of the image display element 10 and the optical system for a virtual image display device. In Fig. 7, a three-dimensional space is defined by ax-axis, ay-axis, and az-axis that are perpendicular to each other. This three-dimensional space does not necessarily coincide with the three-dimensional space defined by the x-axis, y-axis, and z-axis depicted in Figs. 1 and 4 (each is defined as a separate three-dimensional space).

[0072] In this embodiment, the "optical axis" is defined as the optical path of a light 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. This optical axis is also the optical axis of the virtual image display optical system (optical system), and also the optical axis of each optical element (for example, a first optical system 20, an optical member 30, a second optical system 40, and a light guide member 50, which will be described later) included in the virtual image display optical system (optical system).

[0073] 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 a first optical system 20, an optical member 30, a second optical system 40, and a light guide member 50. 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 light guide member 50 becomes the lens unit 3. The first optical system 20, the optical member 30, and the second optical system 40 are embedded in the center part of the frame unit 2 (the part that is placed on the wearer's nose).

[0074] The image display element 10 emits image light toward the negative side of the az axis (upper side in FIG. 7).

[0075] The first optical system 20 passes the image light from the image display element 10. In the example of FIG. 7, the first optical system 20 is composed of a negative lens, a positive lens, a positive lens, a diaphragm, a negative lens, a positive lens, and two reflecting surfaces (mirrors). The five lenses (negative lens, positive lens, positive lens, negative lens, and positive lens) of the first optical system 20 are aspheric lenses having aspheric surfaces on both sides (optical elements having anamorphic surfaces (aspheric surfaces)). In the first optical system 20, an intermediate image is formed and focused by the five lenses while passing the image light from the image display element 10 toward the negative side of the az axis (upper side in FIG. 7), and the image light is reflected (folded back) by the two reflecting surfaces (mirrors) toward the positive side of the az axis (lower side in FIG. 7).

[0076] The optical member 30 has a partially reflective surface 31 that has a function of transmitting and reflecting image light. The partially reflective surface 31 of the optical member 30 transmits the image light from the first optical system 20 (the reflective surface (mirror) of the first optical system 20) toward the positive side of the az axis (the lower side in FIG. 7). The partially reflective surface 31 of the optical member 30 is implemented by, for example, a half mirror, a PBS (Polarizing Beam Splitter), a coating, or the like. In addition, a quarter-wave plate and a positive lens (an aspheric lens having aspheric surfaces on both sides) are provided at the rear stage of the optical member 30 (on the second optical system 40 side). These components may be regarded as components of the optical member 30, or may be regarded as components of the second optical system 40.

[0077] The second optical system 40 collimates (converts into parallel light) the intermediate image formed (focused) by the first optical system 20 by passing the image light from the partially reflecting surface 31 of the optical member 30, and then reflects the image light toward the negative side of the az axis (upper side in FIG. 7). The second optical system 40 has an optical element (positive lens) with an anamorphic surface (aspheric surface), and has a reflecting surface that is an anamorphic surface (aspheric surface).

[0078] The partially reflecting surface 31 of the optical member 30 reflects the image light from the second optical system 40 toward the negative side of the ay axis (the right side in FIG. 7) and causes the image light to enter the light-guiding member 50.

[0079] The light guiding member 50 is an optical member having a first direction along the ay axis and a second direction along the ax axis and az axis perpendicular to the ay axis. The light guiding member 50 has a first partial reflection surface group 51 and a second partial reflection surface group 52. The first partial reflection surface group 51 is aligned in the second direction of the light guiding member 50, and the image light guided from the first direction is incident across (simultaneously). The second partial reflection surface group 52 is aligned in the first direction of the light guiding member 50, and the image light passing through the first partial reflection surface group 51 is incident in sequence.

[0080] In other words, the light guide member 50 has a plurality of first partial reflection surfaces that transmit a first light beam, which is a part of the light beam contained in the light, and reflect a second light beam, which is the other part of the light. Here, if the direction in which the light enters the light guide member 50 is defined as a first direction, the plurality of first partial reflection surfaces are arranged side by side in a second direction perpendicular to the first direction, and constitute a first partial reflection surface group 51. When the light enters the first partial reflection surface group 51, the light simultaneously enters the plurality of first partial reflection surfaces. The light guide member 50 also has a second partial reflection surface group 52 into which the light that has passed through the first partial reflection surface group 51 enters, and the second partial reflection surface group 52 is composed of a plurality of second partial reflection surfaces arranged side by side in the first direction.

[0081] The first partial reflective surface group 51 and the second partial reflective surface group 52 cooperate to reflect the image light incident from the first direction toward the positive side of the az axis (the lower side in FIG. 7) and emit it to the outside from the second direction of the light guiding member 50, so that the image light reaches the wearer's eyes (forming the eyepoint). The first partial reflective surface group 51 and the second partial reflective surface group 52 of the light guiding member 50 are implemented by, for example, a half mirror, a PBS (Polarizing Beam Splitter), a coating, or the like.

[0082] The first partial reflection surface group 51 is provided in plurality along the second direction (along the ax axis) of the light guiding member 50, and six partial reflection surfaces (first partial reflection surfaces) formed in a planar shape are arranged here. The six partial reflection surfaces (first partial reflection surfaces) of the first partial reflection surface group 51 are arranged in a direction such that the image light forms a predetermined angle (for example, 45°) with the ax axis.

[0083] The second partial reflection surface group 52 is provided in a plurality of groups along the first direction (along the ay axis) of the light guiding member 50, and seven partial reflection surfaces (second partial reflection surfaces) formed in a planar shape are arranged here. The seven partial reflection surfaces (second partial reflection surfaces) of the second partial reflection surface group 52 are arranged in a direction in which the image light forms a predetermined angle (for example, 45°) with the ay axis. Moreover, the seven partial reflection surfaces (second partial reflection surfaces) of the second partial reflection surface group 52 are arranged at intervals of 1.7 mm along the first direction (along the ay axis) of the light guiding member 50.

[0084] A half-wave plate 60 that switches the polarization of the image light is provided between the optical member 30 and the light-guiding member 50. A half-wave plate 70 that switches the polarization of the image light is provided between the first partial reflection surface group 51 and the second partial reflection surface group 52. These half-wave plates 60 and 70 control the polarization to be optimal for the first partial reflection surface group 51 and the second partial reflection surface group 52 of the light-guiding member 50, thereby improving the light utilization efficiency.

[0085] Here, the reflectance of the partially reflective surface 31 of the optical member 30 for S-polarized light (incident angle 45°, light absorption 0%) is 90%, and the reflectance of the partially reflective surface 31 of the optical member 30 for P-polarized light (incident angle 45°, light absorption 0%) is 19%, satisfying the above-mentioned conditional expressions (8) and (9). This increases the amount of image light that reaches the light guide member 50 from the optical member 30, thereby improving the light utilization efficiency.

[0086] Moreover, the reflectance of the six partially reflective surfaces of the first partially reflective surface group 51 for S-polarized light (incident angle 45°, light absorption 0%) is 65%, and the reflectance of the six partially reflective surfaces of the first partially reflective surface group 51 for P-polarized light (incident angle 45°, light absorption 0%) is 12%, satisfying the above-mentioned conditional expressions (5) and (6). As a result, the balance between the reflected light and the transmitted light in the first partially reflective surface group 51 can be appropriately set, the intensity distribution of the light flux at the eye box position can be made uniform, and image unevenness can be prevented. Furthermore, since an appropriate amount of light from the outside is reflected by the first partially reflective surface group 51, visibility can be improved.

[0087] Furthermore, the interval D (the interval between adjacent partial reflecting surfaces) of the six partial reflecting surfaces (first partial reflecting surfaces) of the first partial reflecting surface group 51 is as follows. The six partial reflecting surfaces (first partial reflecting surfaces) are arranged from the positive side to the negative side in the ax axis direction. Since the interval D (the interval between adjacent partial reflecting surfaces) of the six partial reflecting surfaces (first partial reflecting surfaces) of the first partial reflecting surface group 51 satisfies the above-mentioned conditional expressions (2) and (2'), it is possible to increase the efficiency of use of image light and increase the amount of light directed toward the eye box to display a bright image. [Spacing between six partial reflecting surfaces (first partial reflecting surfaces) of first partial reflecting surface group 51] 3.6mm 3.6mm 4.1mm 4.6mm 5.0mm

[0088] The seven partially reflective surfaces (second partially reflective surfaces) of the second partially reflective surface group 52 have the following reflectances for S-polarized light (incident angle 45°, light absorption 0%) and P-polarized light (incident angle 45°, light absorption 0%). The values ​​are arranged from the positive side to the negative side in the ay axis direction (from the left to the right in FIG. 7, from the side closer to the optical member 30 to the side farther away). This configuration satisfies the above-mentioned conditional formula (10), and therefore the balance between reflected light and transmitted light in the second partially reflective surface group 52 can be appropriately set while taking polarization into consideration, so that the intensity distribution of the light flux at the eye box position can be made uniform, and image unevenness can be prevented. [Reflectance of S-polarized light and P-polarized light of the seven partial reflecting surfaces (second partial reflecting surfaces) of the second partial reflecting surface group 52] S polarized light P polarized light 12% 1% 13% 1% 19% 2% 22% 2% 23% 3% 32% 4% 50% 19%

[0089] Moreover, the angle of incidence of the image light on the six partial reflecting surfaces (first partial reflecting surfaces) of the first partial reflecting surface group 51 is 45°, which satisfies the above-mentioned conditional expression (3). As a result, by appropriately setting the angle of incidence of the image light on the first partial reflecting surface group 51, and in turn the intervals and sizes of the partial reflecting surfaces (first partial reflecting surfaces) in the first partial reflecting surface group 51, it is possible to make the light flux transmitted through the partial reflecting surfaces (first partial reflecting surfaces) uniform and prevent unevenness in the image light.

[0090] In Numerical Example 1, the light utilization efficiency was defined and calculated by the following formula, and as a result, the light utilization efficiency was 74%, and good light utilization efficiency was achieved. Light utilization efficiency (%)=(light intensity in the eye box when the first partial reflective surface group 51 is present) / (light intensity in the eye box when the first partial reflective surface group 51 is not present)×100

[0091] Fig. 8 is a diagram showing an example of the illuminance distribution on the retina of a wearer by the optical system for a virtual image display device of Numerical Example 1. Fig. 8 shows the illuminance distribution assuming an eye with a pupil diameter of 2.5 mm, the eye being placed 15 mm away from the lower surface of the optical unit, and light of 35° x 20° (horizontal x vertical) is projected.

[0092] Table 1 shows lens data of the optical system for a virtual image display device (optical system) of Numerical Example 1 (FIG. 7). [Table 1]

[0093] In Table 1, Ry (unit: mm) indicates the radius of curvature (or paraxial radius of curvature) of each surface of the optical element on the y-axis (axis perpendicular to the optical axis), Rx (unit: mm) indicates the radius of curvature (or paraxial radius of curvature) of each surface of the optical element on the x-axis (axis perpendicular to the optical axis), D (unit: mm) indicates the thickness of the optical element on the optical axis or the spacing between the optical elements, Nd indicates the refractive index of the d-line (wavelength 587.562 nm), and νd indicates the Abbe number of the d-line. The product name and manufacturer of the material of the optical element are listed in the column to the right of the Abbe number.

[0094] The numbers in Table 1 are given to each surface of the virtual image display device (head mounted display) in order from the image display element 10 side. Number 0 in Table 1 indicates the display surface (pixel array surface) of the image display element 10. Numbers 1 and 2 in Table 1 indicate each surface of a cover glass provided on the image display element 10. The cover glass is a glass member that covers the display surface of the image display element 10. Numbers 3 to 27 in Table 1 indicate the first optical system 20, the optical member 30, the second optical system 40, and the light guiding member 50 (first partially reflective surface group 51, second partially reflective surface group 52).

[0095] The designation A in the column for spacing D of number 25 in Table 1 indicates the spacing in the optical axis direction between the six partially reflective surfaces (first partially reflective surfaces) of the first partially reflective surface group 51 of the light guide member 50, and for convenience, this is referred to as spacing A. As described above, the spacing A is 3.6 mm, 3.6 mm, 4.1 mm, 4.6 mm, and 5.0 mm, in that order, from the partial reflective surface on the near side (the side closer to the partially reflective surface 31 of the optical member 30).

[0096] The vertical, horizontal, and diagonal angles of the displayed image (virtual image) are 35°, 20°, and 40°, respectively. The virtual image distance is infinite.

[0097] In Table 1, the surfaces marked with an "*" are aspheric surfaces. More specifically, these aspheric surfaces are anamorphic aspheric surfaces having anamorphic power. Table 2 shows the data for each aspheric surface. [Table 2]

[0098] In Table 2, the notation E indicates a power with 10 as the base and the number to the right of E as the exponent. The anamorphic aspheric shape is expressed by the following formula, where the paraxial curvature on the x-axis (1 / Rx) is Cx, the paraxial curvature on the y-axis (1 / Ry) is Cy, the height on the x-axis from the optical axis is X (unit: mm), the height on the y-axis from the optical axis is Y (unit: mm), the conic coefficient on the x-axis is Kx, the conic coefficient on the y-axis is Ky, the rotationally symmetric coefficients of the fourth or higher even order are AR4, AR6, ..., and the rotationally asymmetric coefficients of the fourth or higher even order are AP4, AP6, .... Z=(CxX 2 + CyY 2 ) / {1+√(1-(1+Kx)Cx 2 X 2 -(1+Ky)Cy 2 Y 2 )} +AR 4 ((1-AP 4 )X 2 +(1+AP 4 )Y 2 ) 2 +AR 6 ((1-AP 6 )X 2 +(1+AP 6 )Y 2 ) 3 +AR 8 ((1-AP 8 )X 2 +(1+AP 8 )Y 2 ) 4 +AR 10 ((1-AP 10 )X 2 +(1+AP 10 )Y 2 ) 5

[0099] <Numerical Example 2> Fig. 9 is a cross-sectional view showing an optical system for a virtual image display device (optical system) of Numerical Example 2. Fig. 9 shows an xy cross section (cross section including the optical axis) of the image display element 10 and the optical system for a virtual image display device. Regarding components (constituent requirements) and conditional expressions common to Numerical Example 1, redundant explanations will be omitted. From Fig. 9, it can be seen that the intervals A in the optical axis direction between the six partially reflective surfaces (first partially reflective surfaces) of the first partially reflective surface group 51 of the light guide member 50 are different in order from the front side (the side closer to the partially reflective surface 31 of the optical member 30) (3.6 mm, 3.6 mm, 4.1 mm, 4.6 mm, 5.0 mm).

[0100] In Numerical Example 2, the reflectance of the partially reflective surface 31 of the optical member 30 (incident angle 45°, light absorption 0%) is 50%, which satisfies the above-mentioned conditional formula (7). This makes it possible to appropriately set the balance between reflection and transmission of image light on the partially reflective surface 31 of the optical member 30, thereby optimizing the amount of light entering the light guide member 50.

[0101] Furthermore, the reflectance of the six partial reflection surfaces of the first partial reflection surface group 51 of the light guide member 50 is as follows. The reflectances are arranged from the positive side to the negative side in the ax axis direction. The reflectance is unpolarized. The reflectance of the six partial reflection surfaces (first partial reflection surfaces) of the first partial reflection surface group 51 is such that 60% and 80% are alternately repeated three at a time, and the difference in reflectance is 0% when small and 20% when large, thereby satisfying the above-mentioned conditional formula (1). This makes it possible to reduce luminance unevenness and form a high-quality eye box with high visibility. In addition, since the above-mentioned conditional formula (4) is also satisfied, it is possible to appropriately set the balance between the reflected light and the transmitted light in the first partial reflection surface group 51, uniformize the intensity distribution of the light beam at the eye box position, and prevent unevenness in the image. [Reflectance of Six Partially Reflecting Surfaces (First Partially Reflecting Surfaces) of First Partially Reflecting Surface Group 51 of Light-Guiding Member 50] 60% 80% 60% 80% 60% 80%

[0102] The seven partially reflective surfaces (second partially reflective surfaces) of the second partially reflective surface group 52 of the light-guiding member 50 have the following reflectances. The reflectances are arranged from the positive side to the negative side in the ay axis direction. The reflectances are for unpolarized light. [Reflectance of Seven Partially Reflecting Surfaces (Second Partially Reflecting Surfaces) of Second Partially Reflecting Surface Group 52 of Light-Guiding Member 50] 12% 14% 18% twenty one% twenty four% 31% 55%

[0103] In Numerical Example 2, the light utilization efficiency was defined and calculated by the following formula, and as a result, the light utilization efficiency was 72%, and good light utilization efficiency was achieved. Light utilization efficiency (%)=(light intensity in the eye box when the first partial reflective surface group 51 is present) / (light intensity in the eye box when the first partial reflective surface group 51 is not present)×100

[0104] Fig. 10 is a diagram showing an example of the illuminance distribution on the retina of a wearer by the optical system for a virtual image display device of Numerical Example 2. Fig. 10 shows the illuminance distribution assuming an eye with a pupil diameter of 2.5 mm, the eye being placed 15 mm away from the lower surface of the optical unit, and light of 35° x 20° (horizontal x vertical) is projected.

[0105] <Numerical Example 3> Fig. 11 is a cross-sectional view showing an optical system for a virtual image display device of Numerical Example 3. Fig. 11 (third embodiment) shows a yz cross section (a cross section including the optical axis) of the image display element 10 and the optical system for a virtual image display device. Duplicate explanations of components (constituent requirements) and conditional expressions common to Numerical Examples 1 and 2 will be omitted.

[0106] In numerical example 3, the number of partial reflecting surfaces (first partial reflecting surfaces) in the first partial reflecting surface group 51 is increased from six to seven, and the spacing between the seven partial reflecting surfaces (first partial reflecting surfaces) in the first partial reflecting surface group 51 and the reflectance taking polarization into consideration are optimally set.

[0107] In the third numerical embodiment, the reflectance of S-polarized light (incident angle 45°, light absorption 0%) and the reflectance of P-polarized light (incident angle 45°, light absorption 0%) of the seven partially reflective surfaces (first partially reflective surfaces) of the first partially reflective surface group 51 are as follows. The reflectances of S-polarized light and P-polarized light satisfy the above-mentioned conditional expressions (5) and (6), so that the balance between the reflected light and the transmitted light in the first partially reflective surface group 51 can be appropriately set to uniformize the intensity distribution of the light flux at the eye box position, thereby preventing unevenness in the image. In addition, since an appropriate amount of light from the outside is reflected in the first partially reflective surface group 51, visibility can be improved. [Reflectance of S-polarized light and P-polarized light of the seven partial reflecting surfaces (first partial reflecting surfaces) of the first partial reflecting surface group 51] S polarized light P polarized light 88% 22% 65% 19% 88% 22% 65% 19% 88% 22% 65% 19% 88% 22%

[0108] Furthermore, the spacing (spacing between adjacent first partial reflecting surfaces) D of the seven partial reflecting surfaces (first partial reflecting surfaces) of the first partial reflecting surface group 51 is as follows. The seven partial reflecting surfaces (first partial reflecting surfaces) are arranged from the positive side to the negative side in the ax axis direction. Since the spacing (spacing between adjacent first partial reflecting surfaces) D of the seven partial reflecting surfaces (first partial reflecting surfaces) of the first partial reflecting surface group 51 satisfies the above-mentioned conditional expressions (2) and (2'), it is possible to increase the efficiency of use of image light and increase the amount of light directed toward the eye box to display a bright image. [Spacing between the seven partial reflecting surfaces (first partial reflecting surfaces) of the first partial reflecting surface group 51] 2.3mm 2.5mm 2.7mm 2.9mm 3.2mm 4.5mm

[0109] In Numerical Example 3, the light utilization efficiency was defined and calculated by the following formula, and as a result, the light utilization efficiency was 58%, which means that good light utilization efficiency was achieved. Light utilization efficiency (%)=(light intensity in the eye box when the first partial reflective surface group 51 is present) / (light intensity in the eye box when the first partial reflective surface group 51 is not present)×100

[0110] Fig. 12 is a diagram showing an example of the illuminance distribution on the retina of a wearer by the optical system for a virtual image display device of Numerical Example 3. Fig. 12 shows the illuminance distribution assuming an eye with a pupil diameter of 2.5 mm, the eye being placed 15 mm away from the lower surface of the optical unit, and light of 35° x 20° (horizontal x vertical) is projected.

[0111] <Numerical Example 4> Fig. 13 is a cross-sectional view showing an optical system for a virtual image display device according to Numerical Example 4. Fig. 13 (fourth embodiment) shows an xy cross section (cross section including the optical axis) of the image display element 10 and the optical system for a virtual image display device. Regarding components (constituent requirements) and conditional expressions common to Numerical Examples 1-3, duplicated explanations will be omitted. From Fig. 13, it can be seen that the intervals A in the optical axis direction between the seven partial reflection surfaces (first partial reflection surfaces) of the first partial reflection surface group 51 of the light guide member 50 are different in order from the front side (the side closer to the partial reflection surface 31 of the optical member 30) (2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm, 3.2 mm, 4.5 mm).

[0112] In Numerical Example 4, the reflectance of the seven partially reflective surfaces (first partially reflective surfaces) of the first partially reflective surface group 51 of the light-guiding member 50 is 60%, which satisfies the above-mentioned conditional expressions (1) and (4). This makes it possible to reduce luminance unevenness and form a high-quality eye box with high visibility. In addition, by appropriately setting the balance between the reflected light and the transmitted light in the first partially reflective surface group 51, the intensity distribution of the light flux at the eye box position can be made uniform, thereby preventing image unevenness.

[0113] In Numerical Example 4, the light utilization efficiency was defined and calculated by the following formula, and as a result, the light utilization efficiency was 61%, and good light utilization efficiency was achieved. Light utilization efficiency (%)=(light intensity in the eye box when the first partial reflective surface group 51 is present) / (light intensity in the eye box when the first partial reflective surface group 51 is not present)×100

[0114] Fig. 14 is a diagram showing an example of the illuminance distribution on the retina of a wearer by the optical system for a virtual image display device of Numerical Example 4. Fig. 14 shows the illuminance distribution assuming an eye with a pupil diameter of 2.5 mm, the eye being placed 15 mm away from the lower surface of the optical unit, and light of 35° x 20° (horizontal x vertical) is projected.

[0115] 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 idea of ​​the present invention. For example, the embodiments of the present application also include appropriate combinations of the embodiments, etc., which are exemplified in the specification, or obvious embodiments, etc.

[0116] The invention as described in the claims of the original application is set forth below. [Appendix 1] A light guiding member that guides incident light, The light guide member includes a plurality of first partially reflecting surfaces that transmit a first light flux that is a part of the light flux included in the light and reflect a second light flux that is the other part of the light, When a direction in which the light is incident on the light guiding member is defined as a first direction, the plurality of first partially reflective surfaces are arranged in a second direction perpendicular to the first direction to constitute a first partially reflective surface group, When the light is incident on the first group of partially reflective surfaces, the light is simultaneously incident on the plurality of first partially reflective surfaces. A light guiding member comprising: [Appendix 2] a second group of partial reflection surfaces on which the light having passed through the first group of partial reflection surfaces is incident within the light guide member, the second partially reflective surface group is composed of a plurality of second partially reflective surfaces arranged side by side in the first direction; 2. The light-guiding member according to claim 1 . [Appendix 3] When n is a positive integer, the first light flux having been transmitted through a first partially reflecting surface n, which is one of the plurality of first partially reflecting surfaces, is incident on the second group of partially reflecting surfaces; the second light flux reflected by the first partially reflective surface n is further reflected by a first partially reflective surface n+1 adjacent to the first partially reflective surface n, and is incident on the second group of partially reflective surfaces; 3. The light-guiding member according to claim 2, [Appendix 4] The first group of partially reflective surfaces satisfies the following conditional expression (1): 4. The light-guiding member according to claim 1, wherein the light-guiding member is a light-guiding member having a thickness of 100 nm or less. (1) 0%≦Rd<40% however, Rd: the difference in reflectance between any two of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%). [Appendix 5] The following condition (2) is satisfied: 5. The light-guiding member according to claim 1, (2) 1 mm <D<7mm however, D: The spacing between adjacent first partially reflective surfaces among the plurality of first partially reflective surfaces that constitute the first partially reflective surface group. [Appendix 6] The following condition (3) is satisfied: 6. The light-guiding member according to claim 1, (3) 40°<θ1<50° however, θ1: the angle of incidence of light with respect to the first group of partially reflective surfaces. [Appendix 7] The following condition (4) is satisfied: 7. The light-guiding member according to claim 1, (4) T1×0.5 <R1×R1<T1×7 however, T1: transmittance of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%), R1: reflectance of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%). [Appendix 8] The following condition (5) is satisfied: 8. The light-guiding member according to claim 1, (5) Ts × 0.5 <Rs×Rs<Ts×7 however, Ts: transmittance of S-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%), Rs: reflectance of S-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%). [Appendix 9] The following condition (6) is satisfied: 9. The light-guiding member according to claim 1, (6) 0%≦Rp<40% however, Rp: reflectance of P-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%). [Appendix 10] A light guiding member according to any one of Supplementary Note 1 to Supplementary Note 9; a first optical system that transmits image light from an image display element that displays an image; an optical member having a partially reflective surface having a function of transmitting and reflecting the image light; a second optical system that passes through the first optical system, transmits the image light that has passed through or been reflected by the partially reflecting surface of the optical member, and then reflects the image light on the optical member; having The image light reflected by the second optical system and reflected or transmitted by the partially reflecting surface of the optical member is incident on the light guiding member as the light. An optical system characterized by: [Appendix 11] The following condition (7) is satisfied: 11. The optical system according to claim 10, (7) 40% <R0≦60% however, R0: reflectance of the partially reflecting surface of the optical member (incident angle 45°, light absorption 0%). [Appendix 12] The following conditional expressions (8) and (9) are satisfied. 12. The optical system according to claim 10 or 11. (8)60% <Rs0≦100% (9) 0%≦Rp0<30% however, Rs0: reflectance of S-polarized light of the partially reflective surface of the optical member (incident angle 45°, light absorption 0%), Rp0: reflectance of P-polarized light on the partially reflecting surface of the optical member (incident angle 45°, light absorption 0%). [Appendix 13] A light guiding member according to any one of Supplementary Note 1 to Supplementary Note 9; a first optical system that transmits image light from an image display element that displays an image; an optical member having a partially reflective surface having a function of transmitting and reflecting the image light; a second optical system that passes through the first optical system, transmits the image light that has passed through or been reflected by the partially reflecting surface of the optical member, and then reflects the image light on the optical member; having the image light reflected by the second optical system and then reflected or transmitted by the partially reflecting surface of the optical member is incident on the light guiding member as the light, Further comprising a wave plate that switches the polarization of the image light and is positioned between the first partially reflective surface group and the second partially reflective surface group and / or between the optical member and the light guiding member. An optical system characterized by: [Appendix 14] The following condition (10) is satisfied: 10. The light-guiding member according to claim 1, (10) Ts' × 0.5 <Rs’×Rs’<Ts’×7 however, Ts': transmittance of any one of the second partially reflective surfaces for S-polarized light (incident angle 45°, light absorption 0%). Rs': reflectance of any one of the second partial reflecting surfaces for S-polarized light (incident angle 45°, light absorption 0%). [Appendix 15] the optical system forms an intermediate image of the image light from the image display element and includes an optical element having an anamorphic surface; 14. The optical system according to claim 10, [Appendix 16] The image display element; An optical system according to any one of Supplementary Note 10 to Supplementary Note 13; A display device comprising: [Explanation of symbols]

[0117] 1 Head-mounted display (virtual image display device, display device) 2 Frame section 3 Lens section 10 Image display element 20 1st optical system 30 Optical Components 31 Partially reflective surface 40 Second optical system 50 Light guide member 51 First group of partially reflecting surfaces 52 Second group of partially reflecting surfaces 60 1 / 2 wave plate 70 1 / 2 wave plate

Claims

1. A light guiding member that guides incident light, The light guide member includes a plurality of first partially reflecting surfaces that transmit a first light flux that is a part of the light flux included in the light and reflect a second light flux that is the other part of the light, When a direction in which the light is incident on the light guiding member is defined as a first direction, the plurality of first partially reflective surfaces are arranged in a second direction perpendicular to the first direction to constitute a first partially reflective surface group, When the light is incident on the first group of partially reflective surfaces, the light is simultaneously incident on the plurality of first partially reflective surfaces. A light guiding member comprising:

2. a second group of partial reflection surfaces on which the light having passed through the first group of partial reflection surfaces is incident within the light guide member, the second partially reflective surface group is composed of a plurality of second partially reflective surfaces arranged side by side in the first direction; The light guide member according to claim 1 .

3. When n is a positive integer, the first light flux having been transmitted through a first partially reflecting surface n, which is one of the plurality of first partially reflecting surfaces, is incident on the second group of partially reflecting surfaces; the second light flux reflected by the first partially reflective surface n is further reflected by a first partially reflective surface n+1 adjacent to the first partially reflective surface n, and is incident on the second group of partially reflective surfaces; The light guide member according to claim 2 .

4. The first group of partially reflective surfaces satisfies the following conditional expression (1):

3. The light guide member according to claim 1 or 2. (1) 0%≦Rd<40% however, Rd: the difference in reflectance between any two of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%).

5. The following condition (2) is satisfied:

3. The light guide member according to claim 1 or 2. (2) 1mm<D<7mm however, D: The distance between adjacent first partially reflective surfaces among the plurality of first partially reflective surfaces constituting the first partially reflective surface group.

6. The following condition (3) is satisfied:

3. The light guide member according to claim 1 or 2. (3) 40°<θ1<50° however, θ1: the angle of incidence of light with respect to the first group of partially reflective surfaces.

7. The following condition (4) is satisfied: The light guide member according to claim 1 or 2. (4) T1×0.5<R1×R1<T1×7 however, T1: transmittance of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%), R1: reflectance of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%).

8. The following condition (5) is satisfied: The light guide member according to claim 1 or 2. (5) Ts×0.5<Rs×Rs<Ts×7 however, Ts: transmittance of S-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%), Rs: reflectance of S-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%).

9. The following condition (6) is satisfied: The light guide member according to claim 1 or 2. (6) 0%≦Rp<40% however, Rp: reflectance of P-polarized light of any one of the plurality of first partially reflective surfaces constituting the first partially reflective surface group (incident angle 45°, light absorption 0%).

10. The light guiding member according to claim 1 ; a first optical system that transmits image light from an image display element that displays an image; an optical member having a partially reflective surface having a function of transmitting and reflecting the image light; a second optical system that passes through the first optical system and is transmitted or reflected by the partially reflecting surface of the optical member, and then reflects the image light to the optical member; having The image light reflected by the second optical system and then reflected or transmitted by the partially reflecting surface of the optical member is incident on the light guiding member as the light. An optical system characterized by:

11. The following condition (7) is satisfied: The optical system according to claim 10 . (7) 40% < R0 ≦ 60% however, R0: reflectance of the partially reflective surface of the optical member (incident angle 45°, light absorption 0%).

12. The following conditional expressions (8) and (9) are satisfied: The optical system according to claim 10 . (8) 60%<Rs0≦100% (9) 0%≦Rp0<30% however, Rs0: reflectance of S-polarized light of the partially reflective surface of the optical member (incident angle 45°, light absorption 0%), Rp0: reflectance of P-polarized light of the partially reflecting surface of the optical member (incident angle 45°, light absorption 0%).

13. The light guiding member according to claim 1 ; a first optical system that transmits image light from an image display element that displays an image; an optical member having a partially reflective surface having a function of transmitting and reflecting the image light; a second optical system that passes through the first optical system and is transmitted or reflected by the partially reflecting surface of the optical member, and then reflects the image light to the optical member; having the image light reflected by the second optical system and then reflected or transmitted by the partially reflecting surface of the optical member is incident on the light guiding member as the light, Further comprising a wave plate positioned between the first partially reflective surface group and the second partially reflective surface group and / or between the optical member and the light guiding member to switch the polarization of the image light. An optical system characterized by:

14. The following condition (10) is satisfied: The light guide member according to claim 2 . (10) Ts'×0.5<Rs'×Rs'<Ts'×7 however, Ts': transmittance of any one of the second partially reflective surfaces for S-polarized light (incident angle 45°, light absorption 0%). Rs': reflectance of any one of the second partially reflective surfaces for S-polarized light (incident angle 45°, light absorption 0%).

15. the optical system forms an intermediate image of the image light from the image display element and includes an optical element having an anamorphic surface; The optical system according to claim 10 .

16. The image display element; An optical system according to claim 10 or 13; A display device comprising:

Images