Light guide member, optical system, and display device

Abstract

To provide a light guide member, an optical system, and a display device that can improve the light use efficiency for forming an eye-box.SOLUTION: A light guide member to guide image light from an image display element that displays images includes: a pair of plane parts parallel to each other where the image light propagates through total reflection; a first partial reflection surface existing between the pair of plane parts, extending in parallel to the pair of plane parts, and duplicating the image light by reflecting a part of the image light and transmitting the other part; and a second partial reflection surface group existing between the pair of plane parts and emitting the light from an emission surface, which is one of the pair of plane parts, by reflecting a part of the image light duplicated by the first partial reflection surface.SELECTED DRAWING: Figure 5

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 increasingly popular as display devices, and small, see-through HMDs similar to eyeglasses have been developed. A technology for miniaturizing eyeglasses by placing an image display element near the eyeglasses is also known. Furthermore, there are known head-mounted displays (HMDs) and glass devices such as smart glasses that allow the viewer to observe a virtual image superimposed on a scene, and an increasing number of types are available that can accommodate the wearer's eye movements and differences in interpupillary distance.

[0003] Patent Document 1 describes an optical device for guiding image light waves to a given field-of-view. This optical device delivers light to the wearer's eyes by repeatedly total-reflecting the image light on two major surfaces of a light-transmitting substrate and partially reflecting the light on multiple selectively reflecting surfaces.

[0004] Patent Document 2 describes a light guide element adapted to guide a light beam. The light guide element includes a first light guide plate having two flat surfaces (first surface and second surface) and a second light guide plate disposed outside a portion of one of the flat surfaces of the first light guide plate. A light splitting film is disposed between (at the boundary between) the first and second light guide plates. The light beam is repeatedly reflected by the light splitting film and the second light guide plate, thereby increasing (splitting) the luminous flux of the light beam in the first light guide plate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2005 / 0180687 [Patent Document 2] US Patent Application Publication No. 2018 / 0059306 Summary of the Invention [Problem to be solved by the invention]

[0006] However, according to the inventor's intensive research, the conventional technologies including the optical device of Patent Document 1 and the light-guiding element of Patent Document 2 have room for improvement in terms of improving the efficiency of light utilization for forming the eye box.

[0007] 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 improve the efficiency of light utilization for forming an eye box. [Means for solving the problem]

[0008] The light-guiding member of the present invention is a light-guiding member that guides image light from an image display element that displays an image, and is characterized by having a pair of parallel planar portions that propagate the image light while totally reflecting it, a first partially reflective surface located between the pair of planar portions and extending parallel to the pair of planar portions, and duplicating the image light by reflecting a portion of the image light and transmitting the other portion, and a second group of partially reflective surfaces located between the pair of planar portions and reflecting a portion of the image light duplicated by the first partially reflective surface, causing the image light to exit from an exit surface that is one of the pair of planar portions. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a light guide member, an optical system, and a display device that can improve the efficiency of use of light for forming an eye box. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a head-mounted display according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating a first example of a conventional technical problem. [Figure 3] FIG. 10 is a diagram illustrating a second example of a conventional technical problem. [Figure 4] 1 is a conceptual diagram showing a light path inside a light-guiding member of the present invention. [Figure 5] FIG. 2 is a conceptual diagram showing optical paths in the optical system and display device of the present invention. [Figure 6] 10 is a diagram showing an example of an optical path of image light due to a pair of flat surfaces and a second group of partially reflecting surfaces of the light-guiding member. FIG. [Figure 7] FIG. 2 is a cross-sectional view showing an optical system and a display device according to Numerical Example 1. [Figure 8] 10 is a conceptual diagram showing how image light is replicated by a first partially reflecting surface. FIG. [Figure 9] 10 is an illuminance distribution diagram showing the superiority of eye box formation in Numerical Example 1. FIG. [Figure 10]FIG. 10 is a first cross-sectional view showing an optical system and a display device according to Numerical Example 2. [Figure 11] FIG. 10 is a second cross-sectional view showing the optical system and the display device of Numerical Example 2. [Figure 12] 10 is an illuminance distribution diagram showing the superiority of eye box formation in Numerical Example 2. FIG. [Figure 13] FIG. 11 is a first cross-sectional view showing an optical system and a display device according to Numerical Example 3. [Figure 14] FIG. 10 is a second cross-sectional view showing the optical system and the display device of Numerical Example 3. [Figure 15] FIG. 10 is an illuminance distribution diagram showing the superiority of eye box formation in Numerical Example 3. [Figure 16] FIG. 11 is a first cross-sectional view showing an optical system and a display device according to Numerical Example 4. [Figure 17] FIG. 10 is a second cross-sectional view showing the optical system and the display device of Numerical Example 4. [Figure 18] FIG. 10 is an illuminance distribution diagram showing the superiority of eye box formation in Numerical Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0011] An optical system for a virtual image display device according to one embodiment of the present invention and a head-mounted display, which is an example of a virtual image display device, will be described below with reference to the drawings. In the following description, common or corresponding elements will be denoted by the same or similar reference numerals, and duplicated descriptions will be appropriately simplified or omitted. Here, "optical system for a virtual image display device" may be read as "optical system," and "virtual image display device" and "head-mounted display" may be read as "display device." Furthermore, "light-guiding member" may be read as "optical member."

[0012] 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 related to a virtual image) is referred to as "image light." However, the image light may also be read as "light" guided by the light-guiding member 50.

[0013] 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 propagates inside the light-guiding member 50 is defined as the "first direction," and the direction in which the image light (light) is emitted from the light-guiding member 50, which is perpendicular to the "first direction," is defined as the "second direction." The "first direction" corresponds to, for example, the horizontal direction (direction from left to right) in Figures 4 and 5 described later. The "second direction" corresponds to, for example, the vertical direction (direction from top to bottom) in Figures 4 and 5 described later.

[0014] <Outline of head-mounted display configuration> FIG. 1 is a schematic diagram of a head-mounted display 1, which is an example of a virtual image display device according to an embodiment of the present invention. The head-mounted display 1 is a virtual image display device that can be worn on the head of a wearer. In this embodiment, the head-mounted display 1 is, for example, smart glasses, which are eyeglass-type wearable devices. Smart glasses may also be called a glass device or a glass display.

[0015] 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.

[0016] In the example of Fig. 1, the head mounted display 1 is a binocular type head mounted display. In another embodiment, the head mounted display 1 may be a monocular type head mounted display corresponding to one of the left and right eyes. The head mounted display 1 includes an image display element 10 and a lens unit 3. The lens unit 3 includes a light guiding member 50 used in the head mounted display.

[0017] 1, a head mounted display 1 includes a frame unit 2 and a lens unit 3. The lens unit 3 is fitted into the frame unit 2. A pair of lens units 3 are provided corresponding to the left and right eyes of the wearer.

[0018] An image display element 10 that displays an image is built into the frame unit 2. In the example of FIG. 1, the image display element 10 is embedded in a portion of the frame unit 2 that covers the upper edge of the lens unit 3. The installation position of the image display element 10 is not limited to the position exemplified in FIG. 1. For example, the image display element 10 may be embedded in a portion of the frame unit 2 that covers the lower edge, right edge, or left edge of the lens unit 3. The image display element 10 may also be used in a manner that includes a control board that drives and controls the image display element 10. In this case, the control board may be embedded in the temple portion of the frame unit 2 (the portion that hangs over the wearer's ears) instead of the portion depicted by reference numeral 10 in FIG. 1.

[0019] The image display element 10 is an element that emits an image to be observed as a virtual image (image light to be displayed to the user), and examples thereof include an OLED (organic light emitting diode) array, an LD (laser diode) array, an LED (light emitting diode) array, a MEMS (micro electro mechanical systems), and a DMD (digital micromirror device). The image display element 10 may also be a micro LED, a micro OLED, or an LCOS (liquid crystal on silicon). The image display element 10 is positioned and fixed (embedded) at a predetermined position in the lens unit 3 so that the image light enters the light guiding member 50. Note that instead of directly causing the image light to enter the light guiding member 50 from the image display element 10, another optical system may be interposed between the image display element 10 and the light guiding member 50, so that the image light may indirectly enter the light guiding member 50 from the image display element 10.

[0020] 1, the first horizontal direction from the lens unit 3 toward the wearer's eye is referred to as the z direction, the second horizontal direction perpendicular to the z direction is referred to as the x direction, and the vertical direction perpendicular to both the x direction and the z direction is referred to as the y direction. The mutually perpendicular x direction, y direction, and z direction form a left-handed system.

[0021] Note that the names of directions are used for convenience to explain the relative positional relationships of the components, and do not indicate absolute directions. Depending on the posture of the wearer wearing the head mounted display 1, for example, the z direction is not necessarily horizontal, and may be vertical.

[0022] Light emitted from each pixel of the image display element 10 (i.e., image light (light related to a virtual image)) is emitted from the image display element 10 toward the negative y-direction, enters the lens unit 3, is guided through the lens unit 3, and is emitted toward the positive z-direction (i.e., toward each eye of the wearer) to display a virtual image. That is, each of the pair of left and right lens units 3 forms an eyebox in an area including the corresponding eye. More specifically, a light-guiding member 50 is provided within the lens unit 3, and the image light from the image display element 10 is guided by the light-guiding member 50 and propagates in a first direction. The light-guiding member 50 has a first partially reflective surface 51 formed therein. This first partially reflective surface 51 reflects a portion of the image light propagating through the light-guiding member 50 in the first direction and transmits the other portion, thereby replicating the image light. In this sense, the first partially reflective surface 51 may be called an "optical branching unit." The light-guiding member 50 is formed with a second group of partially reflective surfaces 52, which reflect a part of the image light replicated by the first partially reflective surfaces 51, thereby causing the light to be emitted to the outside from a second direction of the light-guiding member 50 (forming an eye box). When the user wears the head-mounted display 1, the light-guiding member 50 is positioned so as to be in front of the user's eyes.

[0023] <Conventional technical issues> FIG. 2 illustrates a first example of a conventional technical problem. As shown in FIG. 2, image light entering a light-guiding member through the left-side incident surface propagates to the right while being reflected by a pair of upper and lower flat surfaces. A plurality of partially reflective surfaces are provided inside the light-guiding member, and components of the image light reflected by the plurality of partially reflective surfaces are emitted from the lower flat surface, which serves as an exit surface, and reach the wearer's eye. The total reflection condition of the pair of flat surfaces is determined according to the angle of incidence of the image light on the plurality of partially reflective surfaces. When the total reflection condition is not satisfied, as in the region indicated by symbol X in FIG. 2, the image light reflected by the plurality of partially reflective surfaces is emitted from the lower flat surface, which serves as an exit surface. When the total reflection condition is satisfied, as in the region indicated by symbol Y in FIG. 2, the image light does not pass through the plurality of partially reflective surfaces and is not emitted to the outside. This results in image light leakage, and if the image light leakage is larger than the pupil, this can cause the image to be missing.

[0024] 3A and 3B are diagrams showing a second example of the conventional technical problem. In the above-mentioned Patent Document 2, as shown in Fig. 3A and 3B, in order to reduce the image chipping that is a problem in Fig. 2, a second light guide plate is arranged outside a part of one plane of a first light guide plate, and a light dividing film is arranged between (at the boundary between) the first and second light guide plates, and the light beam is repeatedly reflected by the light dividing film and the second light guide plate, thereby increasing the luminous flux of the light beam in the first light guide plate (dividing it into many).

[0025] However, when the light beam is repeatedly reflected by the light dividing film and the second light guide plate, some loss of light intensity is unavoidable. As shown in FIG. 3A, thinning the second light guide plate reduces the loss of light intensity of the light beam. However, the light beam split by the light dividing film and the second light guide plate becomes too large, which makes it more likely that the light intensity of the light beam emitted to the eye box will be uneven. As shown in FIG. 3B, thickening the second light guide plate to reduce the number of reflections of the light beam by the light dividing film and the second light guide plate increases the loss of light intensity of the light beam. Thus, there is room for improvement in terms of enlarging the eye box while simultaneously suppressing the unevenness of the light intensity of the light beam emitted to the eye box and the loss of light intensity of the light beam. Furthermore, because the second light guide plate is installed outside the first light guide plate, there is also room for improvement in terms of miniaturizing (thinning) the light guide element.

[0026] <Technical Concept of the Invention> The light guide member, optical system, and display device of the present invention solve the above-mentioned technical problems and have the constituent features for improving the light utilization efficiency for forming an eye box. For example, the eye box can be enlarged while simultaneously suppressing unevenness in the amount of light emitted to the eye box and suppressing loss of the amount of image light. Furthermore, for example, even if the light beam of image light entering the light guide member is thin, image chipping can be reduced. Furthermore, for example, the light guide member can be made smaller (thinner and thinner).

[0027] FIG. 4 is a conceptual diagram showing the optical path inside a light-guiding member of the present invention. The light-guiding member of the present invention guides image light from an image display element that displays an image. The light-guiding member has a pair of parallel flat surfaces, a first partially reflective surface, and a group of second partially reflective surfaces (plurality of second partially reflective surfaces). The pair of flat surfaces totally reflects the image light incident from the left side of FIG. 4 while propagating it to the right side of FIG. 4 (propagating in a first direction). The first partially reflective surface is located between the pair of flat surfaces (inside the light-guiding member) and extends parallel to the pair of flat surfaces (in the left-right direction of FIG. 4), and replicates the image light by reflecting a portion of the image light and transmitting the other portion. For example, the first partially reflective surface replicates one (one) beam of image light into two (two) beams of image light, one reflected and one transmitted (for example, the shape and size are optimally set to satisfy the conditional expressions described below). The second group of partially reflective surfaces is located between the pair of flat surfaces (inside the light-guiding member) and reflects a portion of the image light (for example, two (2) lines of image light) replicated by the first partially reflective surface, causing it to exit from the exit surface which is one of the pair of flat surfaces (causing it to exit in a second direction from the exit surface which is the lower flat surface in Figure 4).

[0028] This improves the efficiency of light utilization for forming the eyebox. More specifically, the eyebox can be enlarged while simultaneously suppressing unevenness in the amount of light emitted to the eyebox and suppressing loss of the amount of image light. By disposing the first partially reflective surface between the pair of flat portions (inside the light-guiding member), loss of the amount of light in the image light can be suppressed. Furthermore, suppressing loss of light can make it possible to appropriately determine the position of the first partially reflective surface, making it easier to suppress unevenness in the amount of light. Furthermore, even if the light beam of image light entering the light-guiding member is thin, image chipping can be reduced. Furthermore, the light-guiding member can be made smaller (thinner and thinner).

[0029] Fig. 5 is a conceptual diagram showing the optical path in the optical system and display device of the present invention. In addition to the light-guiding member described in Fig. 4, Fig. 5 also shows an image display element that emits image light and an optical element (optical element) that guides the image light from the image display element to the light-guiding member. Although Fig. 5 shows the optical element as a single component, the optical element may include multiple components.

[0030] In Fig. 5, image light emitted from the image display element enters the optical element and is collimated. After entering the light-guiding member, it is duplicated into image light of a first optical path that is transmitted through the first partially reflective surface and image light of a second optical path that is reflected by the first partially reflective surface. The image light of the first and second optical paths is each reflected by the second partially reflective surface group and emitted from the exit surface of the light-guiding member. In this way, the luminous flux of the image light can be duplicated by the first and second optical paths. Because the first and second optical paths are different optical paths that are clearly separated by transmission and reflection at the first partially reflective surface, it is possible to easily uniform the luminous flux of the image light that reaches the wearer's eyes.

[0031] Furthermore, since the width of the light beam incident on the light-guiding member is narrow and the incident optical system has a large F-number, aberration correction is easy for the incident optical system, the number of lenses can be reduced, and miniaturization can be achieved in both the optical axis direction and the radial direction.

[0032] In Figure 5, the thickness of the light-guiding member (the distance between the pair of flat surfaces) is denoted by the symbol t, the distance between the first partially reflective surface and the exit surface is denoted by the symbol D, and the length of the first partially reflective surface in the propagation direction (the length in the direction parallel to the pair of flat surfaces) is denoted by the symbol L.

[0033] The light guide member of the present invention preferably satisfies the following conditional formula (1), and more preferably satisfies the following conditional formula (1'). (1)0.3 <D / t<0.7 (1')0.35 <D / t<0.65 however, D: the distance between the first partially reflecting surface and the exit surface (unit: mm, for example), t: thickness of the light guide member (the distance between the pair of flat portions) (unit: mm, for example).

[0034] By satisfying conditional expression (1), the number of reflections of the image light on the first partially reflective surface can be appropriately set (for example, set to one reflection), thereby making it possible to achieve a uniform amount of light. Furthermore, even if there is an inclination between the first partially reflective surface and the light-guiding member, the effect of this inclination can be reduced, thereby improving image quality. This effect is more pronounced when the following conditional expression (1') is satisfied: If the upper or lower limit of conditional expression (1) is exceeded, the number of times the image light is reflected by the first partially reflective surface becomes too large, leading to unevenness in the amount of light and deterioration of image quality due to the strong influence of the inclination of the first partially reflective surface and the light-guiding member.

[0035] It is preferable that the light guide member of the present invention satisfies the following conditional expression (2). (2) 3mm <L<20mm however, L: the length in the propagation direction of the first partially reflecting surface (the length in the direction parallel to the pair of flat surfaces).

[0036] By satisfying conditional expression (2), the number of reflections of the image light on the first partially reflective surface can be appropriately set (for example, set to one reflection), making it possible to achieve a uniform amount of light. Furthermore, even if there is an inclination between the first partially reflective surface and the light-guiding member, the influence of this inclination can be reduced, thereby improving image quality. If the upper limit of conditional expression (2) is exceeded, the number of times that the image light is reflected by the first partially reflective surface becomes too large, leading to unevenness in the amount of light, and the image quality is also degraded due to the strong influence of the tilt of the first partially reflective surface and the light-guiding member caused by manufacturing variations. If the lower limit of conditional expression (2) is exceeded, some image light will not be incident on the first partially reflecting surface, and the optical path will not be sufficiently replicated, resulting in some light flux being lost.

[0037] It is preferable that the light guide member of the present invention satisfies the following conditional expression (3). (3) 40% <R1<60% however, R1: reflectance of the first partially reflective surface (incident angle 45°, light absorption 0%).

[0038] By satisfying conditional expression (3), the amount of light beam duplicated by the first partially reflecting surface can be appropriately set, and a balance can be achieved between the duplicated light beam (light beam due to reflected light) and the normal light beam (light beam due to transmitted light), thereby improving image quality. If the upper limit of conditional expression (3) is exceeded, the amount of light beam duplicated by the first partially reflecting surface becomes too large, reducing the amount of normal light beam, resulting in a difference between the duplicated light beam and the normal light beam, which leads to deterioration of image quality. If the lower limit of conditional expression (3) is exceeded, the amount of light beam duplicated by the first partially reflecting surface will be too small, and the amount of normal light beam will be too large, resulting in a difference between the duplicated light beam and the normal light beam, which will lead to deterioration of image quality.

[0039] It is preferable that the light guide member of the present invention satisfies the following conditional expression (4). (4) 40% <R1s<60% however, R1s: reflectance of S-polarized light from the first partially reflective surface (incident angle 45°, light absorption 0%).

[0040] By satisfying conditional expression (4), the amount of light beam duplicated by the first partially reflecting surface can be appropriately set, and a balance can be achieved between the duplicated light beam (light beam due to reflected light) and the normal light beam (light beam due to transmitted light), thereby improving image quality. If the upper limit of conditional expression (4) is exceeded, the amount of light beam duplicated by the first partially reflecting surface becomes too large, reducing the amount of normal light beam, resulting in a difference between the duplicated light beam and the normal light beam, which leads to deterioration of image quality. If the lower limit of conditional expression (4) is exceeded, the amount of light beam duplicated by the first partially reflecting surface will be too small, and the amount of normal light beam will be too large, resulting in a difference between the duplicated light beam and the normal light beam, which will lead to deterioration of image quality.

[0041] The light guide member of the present invention preferably has an incident surface that allows image light to be incident from the light guide member toward the first partially reflecting surface, and satisfies the following conditional expression (5). (5) 40°<θ1<80° however, θ1: the angle between the incident surface and the exit surface.

[0042] By satisfying conditional expression (5), the image light can be made to preferably enter the first partially reflecting surface, and the image light can be preferably replicated on the first partially reflecting surface. If the upper limit of conditional expression (5) is exceeded, the angle between the incident image light and the first partially reflective surface becomes too small, making it difficult for the image light to be incident on the first partially reflective surface, and the optical path cannot be sufficiently replicated, resulting in leakage of the light beam. If the lower limit of conditional expression (5) is exceeded, the angle of incidence of the incident image light on the plane of the light-guiding member becomes too small, the total reflection condition is not satisfied, and the image light cannot be taken into the light-guiding member.

[0043] The light guide member of the present invention preferably has an incident-side reflecting surface that reflects image light incident on the light guide member toward the first partially reflecting surface, and satisfies the following conditional expression (6). (6) 25°<θ2<40° however, θ2: the angle formed between the incident-side reflecting surface and the exit surface.

[0044] By satisfying conditional expression (6), the image light can be made to preferably enter the first partially reflective surface, and the image light can be preferably replicated on the first partially reflective surface. If the upper limit of conditional expression (6) is exceeded, the angle between the incident image light and the first partially reflective surface becomes too small, making it difficult for the image light to be incident on the first partially reflective surface, and the optical path cannot be sufficiently replicated, resulting in leakage of the light beam. If the lower limit of conditional expression (6) is exceeded, the angle of incidence of the incident image light on the plane of the light-guiding member becomes too small, the total reflection condition is not satisfied, and the image light cannot be taken into the light-guiding member.

[0045] The light guide member of the present invention preferably has an incident-side reflecting surface that reflects image light incident on the light guide member toward the first partially reflecting surface, and satisfies the following conditional expressions (7) and (8). (7) 60% <R0s<100% (8) 0% <R0p<30% however, R0s: Reflectance of S-polarized light from the incident-side reflecting surface (incident angle 45°, light absorption 0%). R0p: reflectance of P-polarized light from the incident-side reflecting surface (incident angle 45°, light absorption 0%).

[0046] By simultaneously satisfying conditional expressions (7) and (8), it is possible to ensure a sufficient amount of image light that reaches the light guide member, thereby improving the utilization efficiency of the image light. If at least one of conditional expressions (7) and (8) is not satisfied, for example, if the lower limit of conditional expression (7) is exceeded or the upper limit of conditional expression (8) is exceeded, the amount of image light reaching the light-guiding member becomes insufficient, and the utilization efficiency of the image light decreases.

[0047] It is preferable that the light guide member of the present invention satisfy the following conditional expression (9). (9) 50°<θ3<70° however, θ3: the angle formed between the second group of partially reflecting surfaces and the exit surface.

[0048] By satisfying conditional expression (9), image light incident on the second partially reflective surface group of the light guiding member at an obtuse angle is delivered to the wearer's eye, thereby reducing ghost flare. Image light incident on the second partially reflective surface group of the light guiding member at an acute angle causes ghost flare, but since the reflectance tends to be higher for incident light at an obtuse angle, the reflectance at an acute angle that causes ghost flare can be reduced. If the upper limit of conditional expression (9) is exceeded, the angle formed by the second group of partially reflecting surfaces and the exit surface of the light-guiding member becomes too large, making it difficult for the image light to satisfy the condition for total reflection with respect to the exit surface of the light-guiding member. If the lower limit of conditional expression (9) is exceeded, the angle between the second partially reflective surface group and the exit surface in the light-guiding member becomes too small, the interval between the image light reflected by the second partially reflective surface group of the light-guiding member and exiting to the outside becomes wide, and the difference in the amount of light depending on the position of the wearer's eye becomes large. In addition, when the light-guiding member is made of resin, it becomes impossible to control the angle dependency of reflectance, and ghost flare occurs.

[0049] Fig. 6 is a diagram showing an example of the optical path of the image light caused by the pair of flat surfaces and the second partially reflecting surface group of the light-guiding member, where the left side of Fig. 6 shows the optical path that delivers the image light to the eye, and the right side of Fig. 6 shows the optical path that results in ghost flare.

[0050] The optical paths that the image light on the left side of Figure 6 takes to reach the eye include an optical path (Configuration 1) in which the image light is totally reflected on the lower side of the pair of flat surfaces, then reflected by the second group of partially reflective surfaces, and emitted to the outside (bottom in Figure 6), resulting in the image light reaching the eye; and an optical path (Configuration 2) in which the image light is totally reflected on the upper side of the pair of flat surfaces, then reflected by the second group of partially reflective surfaces, and emitted to the outside (bottom in Figure 6), resulting in the image light reaching the eye.

[0051] The optical paths that result in ghost flare on the right side of Figure 6 include an optical path (configuration 1) in which the image light is totally reflected on the upper side of the pair of flat sections and then reflected by the second partially reflective surface group, but does not exit to the outside and results in ghost flare inside the light-guiding member, and an optical path (configuration 2) in which the image light is totally reflected on the lower side of the pair of flat sections and then reflected by the second partially reflective surface group, but does not exit to the outside and results in ghost flare inside the light-guiding member.

[0052] In the optical path that delivers image light to the eye on the left side of Figure 6, Configuration 1 has a smaller angle of incidence to the second group of partially reflective surfaces than Configuration 2, and in the optical path that results in ghost flare on the right side of Figure 6, Configuration 1 has a larger angle of incidence to the second group of partially reflective surfaces than Configuration 2.

[0053] The reflectivity of the second partially reflective surface group tends to increase as the angle of incidence of image light increases, so the above configuration 1 tends to result in large ghost flare, and therefore the above configuration 2 is preferable. In particular, when resin is selected for the light-guiding member to reduce weight, the vapor deposition materials that can be selected are limited, making it difficult to control the reflectivity characteristics. The above configuration 1 has the advantage that the number of surfaces of the second partially reflective surface group (the number of individual partially reflective surfaces) can be reduced.

[0054] It is preferable that the light guide member of the present invention satisfies the following conditional expression (10). (10) R2(n-1)≦R2(n) (n is an integer of 2 or greater) however, R2(n-1): reflectance of the n-1th partially reflective surface included in the second group of partially reflective surfaces and counted from the side closest to the first partially reflective surface (incident angle 45°, light absorption 0%), R2(n): reflectance of the nth partially reflective surface included in the second group of partially reflective surfaces and counted from the side closest to the first partially reflective surface (incident angle 45°, light absorption 0%).

[0055] Conditional formula (10) stipulates that when any of the front and rear partially reflective surfaces in the second group of partially reflective surfaces are extracted, the reflectance of the front partially reflective surface must be greater than or equal to the reflectance of the rear partially reflective surface. Since the amount of light decreases according to the reflectance of each partially reflective surface as it passes through each of the second group of partially reflective surfaces, by making the reflectance of each partially reflective surface the same as or greater than the reflectance of the preceding partially reflective surface, the efficiency of use of the image light that reaches the wearer's eyes can be improved (for example, by achieving both suppression of unevenness in the amount of light and suppression of light loss), thereby achieving excellent image quality.

[0056] The light-guiding member of the present invention has a third partially reflective surface group located between the first partially reflective surface and the second partially reflective surface group, and which reflects a portion of the image light replicated by the first partially reflective surface toward the second partially reflective surface group. By incorporating a pupil expander using the third partially reflective surface group, a bright optical system with a large F-number can be achieved, which makes it easier to correct aberrations in the incident optical system, enables the number of lenses to be reduced, and is advantageous for miniaturization in the optical axis direction and radial direction.

[0057] The optical system of the present invention includes the above-described light-guiding member and an optical element that causes image light from an image display element to enter the light-guiding member. In this case, the optical element includes an anamorphic surface and forms an intermediate image of the image light from the image display element. By adopting this anamorphic optical system with an intermediate image, the exit pupil position of the incident optical system can be set at different positions across the horizontal and vertical directions of the image display element, and image light can be delivered to the eye efficiently despite its compact size.

[0058] <Numerical Example 1> Fig. 7 is a cross-sectional view showing the optical system and display device of Numerical Example 1. Fig. 7 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. In Fig. 7, a three-dimensional space is defined by the ax-axis, ay-axis, and az-axis, which are orthogonal 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 Fig. 1 (each is defined as a separate three-dimensional space).

[0059] In this embodiment, the "optical axis" is defined as the optical path of a ray emitted from the center of the effective pixel area of ​​the image display element 10 in a direction perpendicular to the pixel array surface. The optical axis is also the optical axis of the optical system for a virtual image display device (optical system), and also the optical axis of each optical element included in the optical system for a virtual image display device (optical system) (for example, the first optical system 20, the second optical system 30, the polarizing optical element 40, and the light-guiding member 50).

[0060] 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, a second optical system 30, a polarizing optical element 40, and a light-guiding 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-guiding member 50 is provided in the lens unit 3. Furthermore, the first optical system 20, the second optical system 30, and the polarizing optical element 40 may be embedded in the center portion of the frame unit 2 (the portion that rests on the wearer's nose).

[0061] The image display element 10 emits image light toward the positive side of the az axis (upper side in the drawing).

[0062] The first optical system 20 passes image light from the image display element 10. The first optical system 20 is composed of a negative lens, a positive lens, a positive lens, an aperture stop, a negative lens, a positive lens, and two reflecting surfaces (mirrors). Each lens constituting the first optical system 20 is an aspherical lens having aspherical surfaces on both sides (an optical element having an anamorphic surface (aspheric)). Each lens constituting the first optical system 20 forms and focuses an intermediate image while passing image light from the image display element 10 toward the positive side of the az axis (upper side in the figure), and the image light is reflected (folded) toward the negative side of the az axis (lower side in the figure) by the two reflecting surfaces (mirrors). The two reflecting surfaces (mirrors) may be regarded as components of the first optical system 20 or as components separate from the first optical system 20.

[0063] The light-guiding member 50 has an incident-side partially reflective surface (incident-side reflective surface) 53, which has the function of transmitting and reflecting image light, located before the first partially reflective surface 51 and the second group of partially reflective surfaces 52. This incident-side partially reflective surface 53 functions as an "incident-side reflective surface" that reflects the image light incident on the light-guiding member 50 toward the first partially reflective surface 51. The incident-side partially reflective surface 53 is implemented by, for example, a half mirror, a PBS (Polarizing Beam Splitter), a coating, or the like. The incident-side partially reflective surface 53 transmits the image light from the two reflective surfaces (mirrors) of the first optical system 20 toward the negative side of the az axis (the lower side in the figure).

[0064] The second optical system 30 collimates (converts into parallel light) the intermediate image formed (focused) by the first optical system 20 by passing the image light from the incident-side partial reflecting surface 53 of the light-guiding member 50, and then reflects the image light toward the positive side of the az axis (upper side in the drawing). The second optical system 30 has an optical element with an anamorphic surface (aspheric surface), and has a reflecting surface that is also an anamorphic surface (aspheric surface).

[0065] Between the light guide member 50 and the second optical system 30, a polarizing optical element (quarter wave plate) 40 that switches the polarization of the image light before and after it is reflected from the second optical system 30 to the light guide member 50 is disposed.

[0066] The incident-side partial reflecting surface 53 of the light-guiding member 50 reflects the image light from the second optical system 30 toward the positive side of the ay axis and the negative side of the az axis (diagonally downward to the right in the figure), causing the image light to be incident on the first partial reflecting surface 51.

[0067] The light-guiding member 50 has a pair of flat surfaces 54 that are spaced apart in the az-axis direction and extend in the ay-axis direction. The pair of flat surfaces 54 are parallel to each other, and guide (propagate) the image light that has been reflected by the incident-side partial reflection surface 53 of the light-guiding member 50 and entered from diagonally above left, to the right in the drawing while totally reflecting it.

[0068] The first partially reflective surface 51 is located between the pair of flat surfaces 54 (inside the light-guiding member 50), extends parallel to the pair of flat surfaces 54 (in the left-right direction in FIG. 7), and duplicates the image light by reflecting a part of the image light and transmitting the other part. For example, the first partially reflective surface 51 duplicates one (one) beam of image light into two (two) beams of image light, one reflected and one transmitted (its shape and size are optimally set to do so).

[0069] The second group of partially reflective surfaces 52 is located between the pair of flat surfaces 54 (inside the light-guiding member 50) and reflects a portion of the image light (for example, two (two) image light beams) replicated by the first partially reflective surface 51, causing the image light to exit from the exit surface serving as one of the pair of flat surfaces 54 (exiting from the exit surface that is the lower flat surface in FIG. 7). By configuring the second group of partially reflective surfaces 52 from a plurality of partially reflective surfaces, it is possible to ensure a wide angle of view and a wide eyebox while making the light-guiding member 50 thin. The first and second group of partially reflective surfaces 51 and 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.

[0070] When the image light guided to the light-guiding member 50 satisfies the total reflection condition, it is guided while repeatedly undergoing total reflection between the pair of flat surfaces 54, and when the total reflection condition is not satisfied, it is reflected by the second partially reflective surface group 52 and emitted to the outside of the light-guiding member 50, reaches the wearer's eyes, and forms an eyebox. The image light reflected by the second partially reflective surface group 52 does not satisfy the total reflection condition with respect to the pair of flat surfaces 54, and is therefore emitted to the outside of the light-guiding member 50.

[0071] For example, the total reflection condition means whether or not sin θx ≧ 1 / N is satisfied, where θx is defined as the angle of incidence (°) of image light onto second partially reflecting surface group 52 and N is defined as the refractive index of light guiding member 50. When sin θx ≧ 1 / N is satisfied, the total reflection condition is satisfied, and when sin θx ≧ 1 / N is not satisfied, the total reflection condition is not satisfied.

[0072] Additionally or alternatively, the total reflection condition may include at least one of the above-mentioned conditional expressions (5), (6), and (9). For example, the total reflection condition may be satisfied when all of the conditional expressions (5), (6), and (9) are satisfied, and the total reflection condition may not be satisfied when all of the conditional expressions (5), (6), and (9) are not satisfied. (5) 40°<θ1<80° (6) 25°<θ2<40° (9) 50°<θ3<70° however, θ1: the angle between the incident surface and the exit surface, θ2: the angle between the incident-side reflecting surface and the exit surface, θ3: the angle formed between the second group of partially reflecting surfaces and the exit surface.

[0073] Fig. 8 is a conceptual diagram showing the state of duplication of image light by the first partially reflecting surface. In Fig. 8, in addition to the above-mentioned D, t, and L, d and θ are specified (defined). The units of D, t, L, and d are mm, and the unit of θ is °. D: the distance between the first partially reflecting surface and the exit surface, t: thickness of the light guide member (the distance between the pair of flat portions), L: length of the first partially reflecting surface in the propagation direction (length in the direction parallel to the pair of flat surfaces), d: width of the incident luminous flux of the image light incident on the first partially reflective surface, θ: the angle of the incident beam of image light incident on the first partially reflective surface.

[0074] In Numerical Example 1, the distance D between the first partially reflective surface and the exit surface is 1.5 mm, the thickness t of the light-guiding member is 3.0 mm, and the length L of the first partially reflective surface in the propagation direction is 14 mm. Furthermore, the relationship between L, d, and θ is L=d / cosθ (maximum value). cosθ (maximum value) is the maximum value of the angle of the incident light beam of image light incident on the first partially reflective surface, and d is the width of the incident light beam at that time. In Numerical Example 1, cosθ (maximum value) is 80°, and d at that time is 2.5 mm. Furthermore, in Numerical Example 1, the reflectivity R1p (incident angle 45°, light absorption 0%) of the first partially reflective surface for P-polarized light is 18%, and the reflectivity R1s (incident angle 45°, light absorption 0%) of the first partially reflective surface for S-polarized light is 90%.

[0075] In Numerical Example 1, the angle θ2 formed between the incident-side reflecting surface (incident-side partial reflecting surface 53) and the exit surface (the exit surface which is the lower of the pair of flat portions 54) is 36°. The angle θ3 formed between the second partially reflecting surface group 52 and the exit surface (the exit surface which is the lower of the pair of flat portions 54) is 54°. Furthermore, the reflectance R0s of the incident-side reflecting surface (incident-side partial reflecting surface 53) for S-polarized light (incident angle 45°, light absorption 0%) is 90%, and the reflectance R0p of the incident-side reflecting surface (incident-side partial reflecting surface 53) for P-polarized light (incident angle 45°, light absorption 0%) is 18%.

[0076] The second group of partially reflective surfaces 52 is composed of seven partially reflective surfaces, which are arranged at 1.8 mm intervals (predetermined intervals) in the y direction. The reflectivities of the seven partially reflective surfaces of the second group of partially reflective surfaces 52 for S-polarized light and P-polarized light are as follows. The reflectivities are arranged in order from top to bottom, starting from the incident side of the image light (the side closer to the first partially reflective surface 51). The reflectivities of the second group of partially reflective surfaces 52 satisfy the above-mentioned conditional expression (10), and can improve the efficiency of use of the image light that reaches the wearer's eyes (for example, by achieving both suppression of unevenness in the amount of light and suppression of light loss), thereby achieving excellent image quality. [Reflectance of second partial reflecting surface group 52] S polarized light (%) P polarized light (%) 12 1 12 1 19 2 29 3 29 3 42 19 42 19

[0077] 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]

[0078] 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 optical elements, Nd indicates the refractive index of the d-line (wavelength 587.562 nm), and νd indicates the Abbe number for the d-line. The column to the right of the Abbe number lists the trade name and manufacturer of the material of the optical element.

[0079] The numbers in Table 1 are assigned 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 the 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 second optical system 30, the polarizing optical element 40, and the light-guiding member 50.

[0080] The vertical, horizontal, and diagonal angles of the displayed image (virtual image) are 35°, 20°, and 40°, respectively. The virtual image distance is infinity.

[0081] In Table 1, surfaces marked with an "*" are aspherical. More specifically, these aspherical surfaces are anamorphic aspherical surfaces with anamorphic power. Table 2 shows the data for each aspherical surface. [Table 2]

[0082] 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 Cx is the paraxial curvature on the x-axis (1 / Rx), Cy is the paraxial curvature on the y-axis (1 / Ry), X (unit: mm) is the height on the x-axis from the optical axis, Y (unit: mm) is the height on the y-axis from the optical axis, Kx is the conic coefficient on the x-axis, Ky is the conic coefficient on the y-axis, AR4, AR6, ... are rotationally symmetric coefficients of even order or higher, and AP4, AP6, ... are rotationally asymmetric coefficients of even order or higher. Z=(CxX 2 + CyY 2 ) / {1+√(1-(1+Kx)Cx 2 X 2 -(1+Ky)Cy 2 Y 2 )} +AR4·((1-AP4)X 2 +(1+AP4)Y 2 ) 2 +AR6·((1-AP6)X 2 +(1+AP6)Y 2 ) 3 +AR8·((1-AP8)X 2 +(1+AP8)Y 2 ) 4 +AR 10 ·((1-AP 10 )X 2 +(1+AP 10 )Y 2 ) 5

[0083] 9A and 9B are illuminance distribution diagrams showing the advantages of the eyebox formation in Numerical Example 1. FIGS. 9A and 9B show the illuminance distribution on the eyebox when the eye is positioned 15 mm away from the lens configuration of FIG. 7 in the case where the first partially reflective surface is omitted, and FIG. 9B is the illuminance distribution diagram for the lens configuration of FIG. 7 in which the first partially reflective surface is provided. As shown in FIGS. 9A and 9B, by using the first partially reflective surface, the light beam in an area of ​​approximately 4 × 8 mm can be replicated at intervals wider than 0.5 mm without any loss (FIG. 9B is superior to FIG. 9A).

[0084] <Numerical Example 2> 10 and 11 are first and second cross-sectional views showing an optical system and a display device according to Numerical Example 2. In Numerical Example 2, the components other than the light-guiding member 50, i.e., the first optical system 20, the second optical system 30, and the polarizing optical element 40 of Numerical Example 1, are replaced with an incident optical system 60, which is an ideal lens. Image light from the image display element 10 is incident on the light-guiding member 50 via the incident optical system 60. The diameter of the incident beam of image light is 1 mm.

[0085] Numerical Example 2 omits the incident-side partial reflecting surface (incident-side reflecting surface) 53 inside the light-guiding member 50, and instead has an incident surface 55 that causes the image light that has passed through the incident optical system 60 to be incident from the light-guiding member 50 toward the first partially reflecting surface 51. In addition, the light-guiding member 50 further has a third partially reflecting surface group 56 that is located between the first partially reflecting surface 51 and the second partially reflecting surface group 52, and that reflects a portion of the image light replicated by the first partially reflecting surface 51 toward the second partially reflecting surface group 52.

[0086] In Numerical Example 2, the distance D between the first partially reflective surface and the exit surface is 2.5 mm, the thickness t of the light-guiding member is 4.0 mm, and the length L of the first partially reflective surface in the propagation direction is 11.5 mm. Also, referring to FIG. 8 described above, the relationship between L, d, and θ is L=d / cosθ (maximum value). cosθ (maximum value) is the maximum value of the angle of the incident light beam of image light incident on the first partially reflective surface, and d is the width of the incident light beam at that time. In Numerical Example 2, cosθ (maximum value) is 82°, and d at that time is 1.0 mm. Furthermore, in Numerical Example 2, the reflectance R1 (incident angle 45°, light absorption 0%) of the first partially reflective surface is 50%, and the reflectance R1s of S-polarized light of the first partially reflective surface (incident angle 45°, light absorption 0%) is 50%.

[0087] In Numerical Example 2, the angle θ1 formed between incident surface 55 and the exit surface (the exit surface serving as the lower of the pair of flat surfaces 54) is 70°. The angle θ3 formed between second partially reflecting surface group 52 and the exit surface (the exit surface serving as the lower of the pair of flat surfaces 54) is 36°.

[0088] The second group of partially reflective surfaces 52 is made up of 11 partially reflective surfaces, which are arranged at 2.5 mm intervals (predetermined intervals) in the y direction. The third group of partially reflective surfaces 56 is made up of 9 partially reflective surfaces, which are arranged at 2.5 mm intervals (predetermined intervals) in the x direction.

[0089] The reflectances of the 11 partially reflective surfaces in the second partially reflective surface group 52 and the 9 partially reflective surfaces in the third partially reflective surface group 56 are as follows: The reflectances are listed in order from top to bottom, starting from the incident side of the image light (the side closest to the first partially reflective surface 51). [Reflectance of second partial reflecting surface group 52] 9% 9% 12% 12% 19% 19% twenty one% twenty one% 29% 29% 32% [Reflectance of third partial reflecting surface group 56] 90% 12% 19% twenty one% 29% 29% 32% 42% 90%

[0090] 12A and 12B are illuminance distribution diagrams showing the advantages of the eyebox formation in Numerical Example 2. FIGS. 12A and 12B show the illuminance distribution on the eyebox when the eye is positioned 15 mm away from the center of the angle of view when light is projected. FIG. 12A is an illuminance distribution diagram when the first partially reflective surface is omitted from the lens configuration of FIG. 10 , and FIG. 12B is an illuminance distribution diagram for the lens configuration of FIG. 10 with the first partially reflective surface. As shown in FIGS. 12A and 12B, by using the first partially reflective surface, the light beam in an area of ​​approximately 4 × 8 mm can be replicated at intervals wider than 2.0 mm without any loss (FIG. 12B is superior to FIG. 12A).

[0091] <Numerical Example 3> 13 and 14 are first and second cross-sectional views showing an optical system and a display device according to Numerical Example 3. In Numerical Example 3, the components other than the light-guiding member 50, i.e., the first optical system 20, the second optical system 30, and the polarizing optical element 40 of Numerical Example 1, are replaced with an incident optical system 60, which is an ideal lens. Image light from the image display element 10 is incident on the light-guiding member 50 via the incident optical system 60. The diameter of the incident beam of image light is 1 mm.

[0092] Numerical Example 3 further includes a third group of partially reflecting surfaces 56 located between the first and second groups of partially reflecting surfaces 51 and 52, which reflects a portion of the image light replicated by the first and second groups of partially reflecting surfaces 51 toward the second group of partially reflecting surfaces 52. Also included is a wave plate (half wave plate) 57 located between the third and second groups of partially reflecting surfaces 56 and 52, which appropriately switches the polarization of the image light incident from the third group of partially reflecting surfaces 56 to the second group of partially reflecting surfaces 52. Also included is an incident-side reflecting surface 53X instead of the incident-side partially reflecting surface 53. This incident-side reflecting surface 53X is made of, for example, a mirror, and functions as an "incident-side reflecting surface."

[0093] In Numerical Example 3, the distance D between the first partially reflective surface and the exit surface is 1.25 mm, the thickness t of the light-guiding member is 3.0 mm, and the length L of the first partially reflective surface in the propagation direction is 3.6 mm. Also, referring to FIG. 8 described above, the relationship between L, d, and θ is L=d / cosθ (maximum value). cosθ (maximum value) is the maximum value of the angle of the incident light beam of image light incident on the first partially reflective surface, and d is the width of the incident light beam at that time. In Numerical Example 3, cosθ (maximum value) is 74°, and d at that time is 1.0 mm. Furthermore, in Numerical Example 3, the reflectance R1 (incident angle 45°, light absorption 0%) of the first partially reflective surface is 50%, and the reflectance R1s of S-polarized light of the first partially reflective surface (incident angle 45°, light absorption 0%) is 50%.

[0094] In Numerical Example 3, the angle θ2 formed between the incident-side reflecting surface (incident-side reflecting surface 53X) and the exit surface (the exit surface serving as the lower of the pair of flat surfaces 54) is 30°. The angle θ3 formed between the second partially reflecting surface group 52 and the exit surface (the exit surface serving as the lower of the pair of flat surfaces 54) is 60°.

[0095] The second group of partially reflective surfaces 52 is made up of 11 partially reflective surfaces, which are arranged at intervals of 2.0 mm (predetermined intervals) in the y direction. The third group of partially reflective surfaces 56 is made up of 9 partially reflective surfaces, which are arranged at intervals of 2.5 mm (predetermined intervals) in the x direction.

[0096] The reflectivities for S-polarized light and P-polarized light of the 11 partially reflective surfaces in the second partially reflective surface group 52 and the 9 partially reflective surfaces in the third partially reflective surface group 56 are as follows: The reflectivities are listed in order from top to bottom, starting from the incident side of the image light (the side closest to the first partially reflective surface 51). [Reflectance of second partial reflecting surface group 52] S polarized light (%) P polarized light (%) 9 1 9 1 12 2 12 2 19 3 19 3 21 3 21 3 29 3 29 3 32 19 [Reflectance of third partial reflecting surface group 56] 90 90 12 2 19 3 21 3 29 3 29 3 32 19 42 20 90 40

[0097] 15A and 15B are illuminance distribution diagrams showing the advantages of the eye box formation in Numerical Example 3. FIGS. 15A and 15B show the illuminance distribution on the eye box when the eye is positioned 15 mm away from the lens configuration of FIG. 13 , where light is projected from the center of the angle of view. FIG. 15A is an illuminance distribution diagram when the first partially reflective surface is omitted from the lens configuration of FIG. 13 , and FIG. 15B is an illuminance distribution diagram for the lens configuration of FIG. 13 with the first partially reflective surface. As shown in FIGS. 15A and 15B , by using the first partially reflective surface, the light beam in an area of ​​approximately 4 × 8 mm can be replicated at intervals wider than 2.5 mm without any loss (FIG. 15B is superior to FIG. 15A).

[0098] <Numerical Example 4> 16 and 17 are first and second cross-sectional views showing an optical system and a display device according to Numerical Example 4. In Numerical Example 4, the components other than the light-guiding member 50, i.e., the first optical system 20, the second optical system 30, and the polarizing optical element 40 of Numerical Example 1, are replaced with an incident optical system 60, which is an ideal lens. Image light from the image display element 10 is incident on the light-guiding member 50 via the incident optical system 60. The diameter of the incident beam of image light is 1 mm.

[0099] Numerical Example 4 omits the incident-side partial reflecting surface (incident-side reflecting surface) 53 inside the light-guiding member 50, and instead has an incident surface 55 that causes the image light that has passed through the incident optical system 60 to be incident from the light-guiding member 50 toward the first partially reflecting surface 51. In addition, the light-guiding member 50 further has a third partially reflecting surface group 56 that is located between the first partially reflecting surface 51 and the second partially reflecting surface group 52, and that reflects a portion of the image light replicated by the first partially reflecting surface 51 toward the second partially reflecting surface group 52.

[0100] In Numerical Example 4, the distance D between the first partially reflective surface and the exit surface is 2.0 mm, the thickness t of the light-guiding member is 4.0 mm, and the length L of the first partially reflective surface in the propagation direction is 7.2 mm. Also, referring to FIG. 8 described above, the relationship between L, d, and θ is L=d / cosθ (maximum value). cosθ (maximum value) is the maximum value of the angle of the incident light beam of image light incident on the first partially reflective surface, and d is the width of the incident light beam at that time. In Numerical Example 4, cosθ (maximum value) is 74°, and d at that time is 2.0 mm. Furthermore, in Numerical Example 4, the reflectance R1p (incident angle 45°, light absorption 0%) of the first partially reflective surface for S-polarized light is 50%, and the reflectance R1s (incident angle 45°, light absorption 0%) of the first partially reflective surface for P-polarized light is 20%.

[0101] In Numerical Example 4, the angle θ1 formed between the incident surface 55 and the exit surface (the exit surface serving as the lower of the pair of flat surfaces 54) is 60°. Also, the angle θ3 formed between the second partially reflecting surface group 52 and the exit surface (the exit surface serving as the lower of the pair of flat surfaces 54) is 60°.

[0102] The second group of partially reflective surfaces 52 is made up of 11 partially reflective surfaces, which are arranged at 2.5 mm intervals (predetermined intervals) in the y direction. The third group of partially reflective surfaces 56 is made up of 9 partially reflective surfaces, which are arranged at 2.5 mm intervals (predetermined intervals) in the x direction.

[0103] The reflectivities for S-polarized light and P-polarized light of the 11 partially reflective surfaces in the second partially reflective surface group 52 and the 9 partially reflective surfaces in the third partially reflective surface group 56 are as follows: The reflectivities are listed in order from top to bottom, starting from the incident side of the image light (the side closest to the first partially reflective surface 51). [Reflectance of second partial reflecting surface group 52] S polarized light (%) P polarized light (%) 9 1 9 1 12 2 12 2 19 3 19 3 21 3 21 3 29 3 29 3 32 19 [Reflectance of third partial reflecting surface group 56] 90 90 12 2 19 3 21 3 29 3 29 3 32 19 42 20 90 40

[0104] 18A and 18B are illuminance distribution diagrams showing the advantages of the eye box formation in Numerical Example 4. FIGS. 18A and 18B show the illuminance distribution on the eye box when the eye is positioned 15 mm away from the lens configuration of FIG. 16 in which the first partially reflective surface is omitted, and FIG. 18B shows the illuminance distribution in the lens configuration of FIG. 16 in which the first partially reflective surface is provided. As shown in FIGS. 18A and 18B, by using the first partially reflective surface, the light beam in an area of ​​approximately 4 × 8 mm can be replicated at intervals wider than 2.0 mm without any loss (FIG. 18B is superior to FIG. 18A).

[0105] Regarding the conditional expressions (1), (2), (5), (6), and (9) of this embodiment, the corresponding numerical values ​​of Numerical Examples 1 to 4 are shown below. Numerical Example 1 Numerical Example 2 Numerical Example 3 Numerical Example 4 (1)D / t 0.5 0.63 0.42 0.5 (2)L 14 11.5 3.6 7.2 (5) θ1 - 70 - 60 (6)θ2 36 - 30 - (9)θ3 54 36 60 60

[0106] The above is a description of exemplary embodiments of the present invention. The embodiments of the present invention are not limited to those described above, and various modifications are possible within the scope of the technical concept of the present invention. For example, the embodiments of the present application also include appropriate combinations of embodiments explicitly shown in the specification or obvious embodiments.

[0107] The inventions described in the claims of the present application as originally filed are as follows: [Appendix 1] A light guide member that guides image light from an image display element that displays an image, a pair of parallel flat surfaces that transmit the image light while totally reflecting the image light; a first partially reflective surface located between the pair of flat surfaces and extending parallel to the pair of flat surfaces, the first partially reflective surface reflecting a portion of the image light and transmitting another portion of the image light to replicate the image light; a second group of partially reflecting surfaces positioned between the pair of planar portions and configured to reflect a portion of the image light replicated by the first partially reflecting surfaces, thereby causing the image light to exit from an exit surface serving as one of the pair of planar portions; A light-guiding member comprising: [Appendix 2] The following condition (1) is satisfied: 2. The light-guiding member according to claim 1, (1)0.3 <D / t<0.7 however, D: the distance between the first partially reflective surface and the exit surface, t: the thickness of the light-guiding member (the distance between the pair of flat portions). [Appendix 3] The following condition (2) is satisfied: 3. The light-guiding member according to claim 1 or 2, (2) 3mm <L<20mm however, L: the length in the propagation direction of the first partially reflecting surface (the length in the direction parallel to the pair of flat surfaces). [Appendix 4] The following condition (3) is satisfied: 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. (3) 40% <R1<60% however, R1: reflectance of the first partially reflective surface (incident angle 45°, light absorption 0%). [Appendix 5] The following condition (4) is satisfied: 5. 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. (4) 40% <R1s<60% however, R1s: reflectance of S-polarized light from the first partially reflective surface (incident angle 45°, light absorption 0%). [Appendix 6] an incident surface through which the image light is incident from the light guiding member toward the first partially reflective surface; The following condition (5) is satisfied: 6. The light-guiding member according to any one of claims 1 to 5, wherein: (5) 40°<θ1<80° however, θ1: the angle between the incident surface and the exit surface. [Appendix 7] an incident-side reflective surface that reflects the image light incident on the light-guiding member toward the first partially reflective surface, The following condition (6) is satisfied: 7. 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. (6) 25°<θ2<40° however, θ2: the angle formed between the incident-side reflecting surface and the exit surface. [Appendix 8] an incident-side reflective surface that reflects the image light incident on the light-guiding member toward the first partially reflective surface, The following conditional expressions (7) and (8) are satisfied: 8. 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. (7) 60% <R0s<100% (8) 0% <R0p<30% however, R0s: Reflectance of S-polarized light from the incident-side reflecting surface (incident angle 45°, light absorption 0%). R0p: reflectance of P-polarized light from the incident-side reflecting surface (incident angle 45°, light absorption 0%). [Appendix 9] The following condition (9) is satisfied: 9. The light-guiding member according to any one of Supplementary Note 1 to Supplementary Note 8, (9) 50°<θ3<70° however, θ3: the angle formed between the second group of partially reflecting surfaces and the exit surface. [Appendix 10] The following condition (10) is satisfied: 10. The light-guiding member according to any one of Supplementary Note 1 to Supplementary Note 9, (10) R2(n-1)≦R2(n) (n is an integer of 2 or greater) however, R2(n-1): reflectance of the n-1th partially reflective surface included in the second group of partially reflective surfaces and counted from the side closest to the first partially reflective surface (incident angle 45°, light absorption 0%), R2(n): reflectance of the nth partially reflective surface included in the second group of partially reflective surfaces and counted from the side closest to the first partially reflective surface (incident angle 45°, light absorption 0%). [Appendix 11] a third group of partially reflective surfaces located between the first and second groups of partially reflective surfaces, and which reflect a portion of the image light replicated by the first partially reflective surfaces toward the second group of partially reflective surfaces; 11. 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. [Appendix 12] A light guiding member according to any one of Supplementary Note 1 to Supplementary Note 11; an optical element that causes the image light from the image display element to be incident on the light guide member; An optical system comprising: [Appendix 13] the optical element includes an anamorphic surface and forms an intermediate image of the image light from the image display element. 13. The optical system according to claim 12, [Appendix 14] the image display element; an optical system according to Supplementary Note 12 or Supplementary Note 13; A display device comprising: [Explanation of symbols]

[0108] 1. Head-mounted display (virtual image display, display device) 2 Frame section 3 Lens section 10 Image display element 20 1st optical system 30 Second optical system 40 Polarizing optical element (1 / 4 wave plate) 50 Light guide member (optical member) 51 First partially reflecting surface (optical branching section) 52 second partially reflective surface group (plurality of second partially reflective surfaces) 53 Partial reflection surface on the input side (reflection surface on the input side) 53X Reflection surface of entrance part (reflection surface of entrance side) 54 Pair of flat surfaces 55 Incidence plane 56 Third group of partially reflecting surfaces 57 Wave plate (1 / 2 wave plate) 60 Input optical system

Claims

1. A light guide member that guides image light from an image display element that displays an image, a pair of parallel flat surfaces that transmit the image light while totally reflecting the image light; a first partially reflective surface located between the pair of flat surfaces and extending parallel to the pair of flat surfaces, the first partially reflective surface reflecting a portion of the image light and transmitting another portion of the image light to replicate the image light; a second group of partially reflecting surfaces positioned between the pair of planar portions and configured to reflect a portion of the image light replicated by the first partially reflecting surfaces, thereby causing the image light to exit from an exit surface serving as one of the pair of planar portions; A light-guiding member comprising:

2. The following conditional expression (1) is satisfied: The light guide member according to claim 1 . (1) 0.3<D / t<0.7 however, D: the distance between the first partially reflecting surface and the exit surface, t: thickness of the light guide member.

3. The following conditional expression (2) is satisfied: The light guide member according to claim 1 . (2) 3mm<L<20mm however, L: the length of the first partially reflecting surface in the propagation direction.

4. The following condition (3) is satisfied: The light guide member according to claim 1 . (3) 40%<R1<60% however, R1: reflectance of the first partially reflective surface.

5. The following conditional expression (4) is satisfied: The light guide member according to claim 1 . (4) 40%<R1s<60% however, R1s: reflectance of the first partially reflective surface for S-polarized light.

6. an incident surface through which the image light is incident from the light guiding member toward the first partially reflective surface; The following condition (5) is satisfied: The light guide member according to claim 1 . (5) 40°<θ1<80° however, θ1: the angle between the incident surface and the exit surface.

7. an incident-side reflective surface that reflects the image light incident on the light-guiding member toward the first partially reflective surface, The following condition (6) is satisfied: The light guide member according to claim 1 . (6) 25°<θ2<40° however, θ2: the angle formed between the incident-side reflecting surface and the exit surface.

8. an incident-side reflective surface that reflects the image light incident on the light-guiding member toward the first partially reflective surface, The following conditional expressions (7) and (8) are satisfied: The light guide member according to claim 1 . (7) 60%<R0s<100% (8) 0%<R0p<30% however, R0s: reflectance of the incident side reflecting surface for S-polarized light. R0p: reflectance of the incident side reflecting surface for P-polarized light.

9. The following condition (9) is satisfied: The light guide member according to claim 1 . (9) 50°<θ3<70° however, θ3: Angle formed between the second group of partially reflecting surfaces and the exit surface.

10. The following condition (10) is satisfied: The light guide member according to claim 1 . (10) R2(n-1)≦R2(n) (n is an integer of 2 or more) however, R2(n-1): reflectance of the (n-1)th partially reflective surface, included in the second group of partially reflective surfaces, from the side closest to the first partially reflective surface, R2(n): reflectance of the nth partially reflective surface, included in the second group of partially reflective surfaces, from the side closest to the first partially reflective surface.

11. a third group of partially reflective surfaces located between the first and second groups of partially reflective surfaces, and which reflect a portion of the image light replicated by the first partially reflective surfaces toward the second group of partially reflective surfaces; The light guide member according to claim 1 .

12. The light guide member according to claim 1 ; an optical element that causes the image light from the image display element to be incident on the light guide member; An optical system comprising:

13. the optical element includes an anamorphic surface and forms an intermediate image of the image light from the image display element.

13. The optical system according to claim 12.

14. the image display element; an optical system according to claim 12 or 13; A display device comprising:

Images