Optical system and image display device

Abstract

Provided is an optical system comprising: an incidence part on which image light from a display part is incident, and which changes the traveling direction of the incident image light; and an expansion part which divides and duplicates the image light traveling from the incidence part. The expansion part has a first expansion part disposed on a first surface, and a second expansion part disposed on a second surface different from the first surface. The first expansion part has a first diffraction structure part and a second diffraction structure part which have a diffraction structure for dividing and duplicating the image light along a first direction, and a non-diffraction structure part which is disposed between the first diffraction structure part and the second diffraction structure part and does not have a diffraction structure. The second expansion part has a third diffraction structure part for dividing and duplicating the image light along the first direction, and the third diffraction structure part is disposed so as to overlap the non-diffraction structure part of the first expansion part in the vertical direction of a pupil expansion part.

Description

Optical system and image display device

[0001] The present disclosure relates to an optical system used to display an image and an image display device including the same.

[0002] As an image display device, Patent Document 1 describes an optical system equipped with a waveguide (light guide) for expanding the exit pupil in two directions. The optical system can expand the exit pupil by utilizing a diffractive optical element. Furthermore, Document 2 describes a head-mounted display that keeps the amount of light diffracted from a diffraction grating constant by modulating the height and duty ratio of the diffraction grating.

[0003] US Patent No. 10,429,645 US Patent Application Publication No. 2009 / 0097122

[0004] To achieve a wide viewing angle, it is necessary to increase the area of ​​the extension section that expands the exit pupil. However, the extension section has a highly accurate diffractive structure, and increasing the area of ​​the extension section has been difficult from a manufacturing perspective. Furthermore, when multiple extension sections are joined together to increase the area of ​​the extension section, discontinuity in the diffractive structure at the joints can cause distortion in the displayed image.

[0005] The present disclosure provides an optical system and an image display device in which the area of ​​the extension portion is increased and image distortion is reduced.

[0006] The optical system disclosed herein includes an incident section that receives image light from a display section and changes the traveling direction of the incident image light, and a pupil extension section that divides and replicates the image light traveling from the incident section. The pupil extension section includes a first extension section disposed on a first surface and a second extension section disposed on a second surface different from the first surface. The first extension section includes a first diffractive structure section and a second diffractive structure section having a diffractive structure that divides and replicates the image light along a first direction, and a non-diffractive structure section disposed between the first diffractive structure section and the second diffractive structure section and not having a diffractive structure. The second extension section includes a third diffractive structure section that divides and replicates the image light along the first direction. The third diffractive structure section is disposed so as to overlap the non-diffractive structure section of the first extension section in the vertical direction of the pupil extension section.

[0007] An image display device according to the present disclosure includes the above-described optical system and a display unit that emits image light.

[0008] According to the optical system and image display device of the present disclosure, it is possible to provide an optical system and an image display device in which the area of ​​the extension portion is increased and image distortion is reduced.

[0009] Schematic perspective view showing the configuration of the optical system of embodiment 1 Longitudinal cross-sectional view of the light guide of embodiment 1 Front view of the first main surface of the light guide of embodiment 1 Front view of the second main surface of the light guide of embodiment 1 Explanatory diagram explaining the optical path of diffracted light from the third diffractive structure section of embodiment 1 Explanatory diagram showing the configuration of each diffractive structure section of embodiment 1 Longitudinal cross-sectional view showing modulation of the diffractive structure of each diffractive structure section Explanatory diagram showing the relationship between the diffraction efficiency of each diffractive structure and an image Explanatory diagram showing the relationship between the diffraction efficiency of each diffractive structure and an image Longitudinal cross-sectional view of a light guide of embodiment 2 in a modified example of embodiment 1 Schematic perspective view showing the configuration of the optical system of embodiment 2 Longitudinal cross-sectional view of a light guide of embodiment 2 Schematic perspective view showing the configuration of the optical system of embodiment 2 Explanatory diagram showing the configuration of each diffractive structure section of the modified example of embodiment Explanatory diagram showing the configuration of each diffractive structure section of the modified example of embodiment Explanatory diagram showing the configuration of each diffractive structure section of the modified example of embodiment Explanatory diagram showing the configuration of each diffractive structure section of the modified example of embodiment

[0010] (Embodiment 1) [1-1. Configuration] [1-1-1. Overall Configuration of Optical System] A specific embodiment of an image display device 1 according to the present disclosure will be described with reference to Figs. 1 to 4. Fig. 1 is a schematic perspective view showing the configuration of the image display device 1. Fig. 2 is a vertical cross-sectional view of a light guide according to the first embodiment. Fig. 3 is a front view of a first main surface of the light guide according to the first embodiment. Fig. 4 is a front view of a second main surface of the light guide according to the first embodiment. In the first embodiment, the first direction corresponds to the vertical direction of the viewing area Ac, and the second direction corresponds to the horizontal direction of the viewing area Ac in which an image can be viewed.

[0011] The image display device 1 is used in an electronic mirror, a head-up display system (hereinafter referred to as an HUD system), a head-mounted display (hereinafter referred to as an HMD), etc. The image display device 1 includes a display unit 11 and a so-called pupil-widening light guide 13. The image display device 1 may include a projection optical system between the display unit 11 and the light guide 13, which collimates a beam L1 of image light from the display unit 11 and causes the beam L1 to enter the combining unit 21. The projection optical system 7 is, for example, a biconvex lens.

[0012] The display unit 11 displays an image under control of an external control unit. For example, a backlit liquid crystal display, an organic light-emitting diode (OLED) display, or a plasma display can be used as the display unit 11. Alternatively, the display unit 11 may generate an image using a screen that diffuses or reflects light, a projector, or a scanning laser. The display unit 11 can display image content including various types of information, and emits a light beam L1 including the image content that is visually recognized by the observer D.

[0013] The light guide 13 divides and replicates the light beam L1 emitted from the display unit 11 and guides the replicated light beam L4 to the viewing area Ac. The light guide 13 includes a combining unit 21 that receives the image light from the display unit 11 and changes its traveling direction, and a pupil expansion unit 22 that divides and replicates the incident image light. The pupil expansion unit 22 includes a third expansion unit 23 that expands the entrance pupil in a second direction (X-axis direction), and a first expansion unit 25 and a second expansion unit 26 that expand the entrance pupil in a first direction (Y-axis direction). The first direction and the second direction may intersect each other and, for example, be perpendicular to each other.

[0014] [1-1-2. Configuration of Light Guide] The coupling section 21, the third extension section 23, the first extension section 25, and the second extension section 26 each have a diffraction power for diffracting the image light, and each has, for example, an embossed hologram formed as a diffraction grating. The coupling section 21, the third extension section 23, and the first extension section 25 each diffract the image light at different angles.

[0015] The diffractive structure disposed in the coupling portion 21 is, for example, a transmissive surface relief diffraction grating, and has periodic concave and convex portions, but the concave and convex portions do not have to be perfectly periodic. The coupling portion 21 changes the propagation direction of the image light incident from the outside to head toward the third extension portion 23 by using diffraction power, and emits the image light as a light beam L2. In the first embodiment, coupling refers to a state in which the light propagates within the light guide 13 under total reflection conditions.

[0016] The light guide 13 is configured to totally reflect the incident light beam therein. The light guide 13 has an incident section 20 onto which the light beam of image light from the display unit 11 is incident, and an exit section 29 from which the light beam split and replicated within the light guide 13 is emitted. The light guide 13 has a first main surface 14 and a second main surface 15 facing each other. In the first embodiment, as shown in FIG. 3 , the incident section 20, the third extension section 23, the first extension section 25, and the exit section 29 are arranged on the first main surface 14, which is the front surface, and a coupling section 21 is arranged on the incident section 20. The first main surface 14 and the second main surface 15 are parallel to each other. Furthermore, as shown in FIG. 4 , the third extension section 23 and the second extension section 26 are arranged on the second main surface 15, which is the back surface.

[0017] The first main surface 14 also faces the viewer D. In the first embodiment, the incident section 20 is included in the coupling section 21, but the coupling section 21 may be arranged on the second main surface 15 separately from the incident section 20. Furthermore, the exit section 29 may also be arranged on the second main surface 15 separate from the first main surface 14 on which the incident section 20 is arranged. In this case, the viewer D faces the second main surface opposite to the first main surface into which light is incident.

[0018] 1 , the third extension section 23 is, for example, provided with a transmissive relief-type diffraction grating, and replicates the image light by splitting the incident image light into image light traveling in a second direction (X-axis direction) and image light traveling in a first direction (Y-axis direction), i.e., toward the first extension section 25, using diffraction power. The third extension section 23 expands the light beam L2 in a second direction corresponding to the horizontal direction of the viewing area Ac and emits it to the first extension section 25 in the first direction (Y-axis direction) intersecting with the second direction. The third extension section 23 functions as a bending section that bends the light beam L2 toward the area from which the image light is extracted.

[0019] For example, in FIG. 1 , diffraction gratings are arranged at four points 23p in the third extension section 23, aligned in the direction in which the image light travels while repeatedly undergoing total reflection. The diffraction grating splits the image light at each point 23p, and the split image light travels to the first extension section 25. The incident image light beam is expanded by being duplicated into four image light beams in the second direction. In this way, the light beam L2 propagating from the coupling section 21 propagates in the second direction while repeatedly undergoing total reflection at the first principal surface 14 and the second principal surface 15. The light beam L2 is duplicated and emitted in the first direction by the diffractive structures of the third extension section 23 formed on the first principal surface 14 and the second principal surface 15, respectively. The first extension section 25 and the second extension section 26 are arranged in a first direction of the third extension section 23, and the image light divided and replicated in the first direction from the third extension section 23 is guided to the first extension section 25 and the second extension section 26 by the first main surface 14 and the second main surface 15.

[0020] The first extension section 25 has a first diffractive structure section 25a and a second diffractive structure section 25b. The first extension section 25 replicates the image light by splitting the incident image light into image light propagating in a first direction (Y-axis direction) using diffractive power and image light exiting the first extension section 25 to the outside. The first diffractive structure section 25a and the second diffractive structure section 25b are, for example, relief-type diffraction gratings with periodic concave and convex portions, but they do not have to be perfectly periodic. A non-diffractive structure section 27 is disposed between the first diffractive structure section 25a and the second diffractive structure section 25b. The non-diffractive structure section 27 is a section that mainly follows the shape of the light guide 13 and is a region where transmission, refraction, and total reflection, rather than diffraction, occur primarily for the light beam propagating inside the light guide 13.

[0021] The second extension section 26 has a third diffractive structure section 26a, which splits the incident image light into image light traveling in a first direction (Y-axis direction) using diffractive power and image light that passes through the non-diffractive structure section 27 from the second extension section 26 and exits to the outside, thereby replicating the image light. The third diffractive structure section 26a is, for example, a reflective relief-type diffraction grating, with periodic unevenness formed thereon, but the unevenness does not have to be perfectly periodic. The light beam L3 guided in the Y-axis direction from the third extension section 23 propagates in the first direction while repeatedly undergoing total reflection at the first principal surface 14 and the second principal surface 15. The light beam L3 is replicated by the diffractive structures of the first extension section 25 arranged on the first principal surface 14 and the second extension section 26 arranged on the second principal surface 15, and is then emitted to the outside of the light guide 13 via the exit section 29.

[0022] In Figure 1, for example, the first expansion section 25 and the second expansion section 26 arrange divided and duplicated points 25p arranged in the first direction in three rows on the light guide 13, for a total of 12 points 25p arranged in four rows.

[0023] The image light is split at each point 25p, and the split image light is emitted to the outside. As a result, each of the four columns of incident image light beams is duplicated into three image light beams in the first direction, thereby expanding the field of view. In this way, the light guide 13 can duplicate twelve image light beams (pupils) from one incident image light beam, and duplicate the beams in both the first and second directions, thereby expanding the field of view.

[0024] Therefore, from the viewpoint of observer D, light guide 13 expands light beam L1, which has been incident on entrance portion 20 and has its direction of travel changed, in the horizontal direction of the image viewed by observer D, and then further expands it in the vertical direction of the image to emit light beam L4 from exit portion 29. Here, "duplicating the image in the horizontal direction" is not limited to "duplicating in the completely horizontal direction" but also includes "duplicating in the approximately horizontal direction." Furthermore, "duplicating the image in the vertical direction" is not limited to "duplicating in the completely vertical direction" but also includes "duplicating in the approximately vertical direction." The observer can view each of the twelve light beams of image light as an image, and the viewing area Ac in which observer D can view the image light can be widened.

[0025] [1-1-3. First extension section and second extension section] By combining the first diffractive structure section 25 a, the second diffractive structure section 25 b, and the third diffractive structure section 26 a, which are smaller than the area of ​​the exit section 29, it is possible to realize a large-area field of view area Ac without requiring a device for manufacturing a large-area diffractive structure section.

[0026] In the first direction, the non-diffractive structure portion 27 is disposed between the first diffractive structure portion 25 a and the second diffractive structure portion 25 b. From a viewpoint directly facing the light beam L4 emitted from the emission portion 29, the non-diffractive structure portion 27 is disposed to overlap the third diffractive structure portion 26 a, the lower portion of the first diffractive structure portion 25 a overlaps with the upper portion of the third diffractive structure portion 26 a, and the upper portion of the second diffractive structure portion 25 b overlaps with the lower portion of the third diffractive structure portion 26 a.

[0027] Next, the length Lg of the non-diffractive structure portion 27 in the first direction will be described with reference to Fig. 5. When the first diffractive structure portion 25a, the second diffractive structure portion 25b, and the third diffractive structure portion 26a are each arranged along the first direction, if the length Lg of the non-diffractive structure portion 27 is short, the light beam L3 propagating in the first direction may be diffracted at the lower end of the first diffractive structure portion 25a and the upper end of the second diffractive structure portion 25b, causing interference and resulting in a deterioration in image quality.

[0028] When the relationship between the length Lg of the non-diffractive structure 27, the wavelength λ of the light beam L1 emitted from the display unit 11, and the wavelength width Δλ of the light beam L1 satisfies the following formula (1), the length Lg of the non-diffractive structure 27 becomes greater than the coherence length, and interference can be reduced: (λ×λ / Δλ)−Lg>0 (Formula (1))

[0029] For example, if the length Lg of the non-diffractive structure 27 is 10 times or more the wavelength of the light beam L1, degradation of the image quality can be prevented. The length Lg of the non-diffractive structure 27 is, for example, 5 to 20 μm or more.

[0030] Furthermore, the relationship between the length Lg1 of overlap between the second diffractive structure portion 25b and the third diffractive structure portion 26a in the first direction, the thickness t of the light guide 13 perpendicular to the first direction, and the angle of incidence θ1 of the light beam reflected at the lower end of the third diffractive structure portion 26a onto the upper end of the second diffractive structure portion 25b satisfies the following formula (2). This makes it possible to prevent the pupil of the secondary ray L13 of the light beam L1 having the smallest angle of incidence (propagation angle) with respect to the incident portion 20 from being missing: Lg1>t×tanθ1 (2)

[0031] Furthermore, the relationship between the length Lg2 of overlap between the first diffractive structure 25a and the third diffractive structure 26a in the first direction, the thickness t of the light guide 13, and the angle of incidence θ2 of the light beam reflected at the upper end of the third diffractive structure 26a onto the lower end of the first diffractive structure 25a satisfies the following formula (3). This makes it possible to prevent the pupil of the secondary ray L12 of the light beam L1 having the maximum propagation angle, which is the maximum angle of incidence (propagation angle) with respect to the incident portion 20, from being missing: Lg2>t×tanθ2 (3)

[0032] The angle range in which the extracted image light can be seen even if the user's viewpoint moves is between the angle θ1a at which the secondary ray L13 propagating through the light guide 13 at the minimum propagation angle is visible and the angle θ2a at which the secondary ray L12 propagating through the light guide 13 at the maximum propagation angle is visible.

[0033] [1-1-4. Diffractive Structure] Next, the diffractive structure of each of the first extension section 25 and the second extension section 26 will be described with reference to Fig. 6. Figs. 6(a) to 6(d) are explanatory diagrams showing the configuration of each diffractive structure.

[0034] The first diffractive structure portion 25a, the second diffractive structure portion 25b, and the third diffractive structure portion 26a each have a structure of a diffraction grating 31a that is periodically formed at a pitch P. As shown in FIG. 6A, the diffraction grating 31a has structural characteristics determined by a height h from the surface, a width W, a pitch P, and a duty ratio Dr (Dr=W / P). The diffraction grating 31a is, for example, a transparent resin layer, and is formed by nanoimprinting. In addition to nanoimprinting, it can also be formed by, for example, imprinting SiO ２ Alternatively, the diffraction grating 31a may be formed by laminating these layers and then dry etching them.

[0035] Furthermore, the heights of the convex portions of the first diffractive structure portion 25a, the second diffractive structure portion 25b, and the third diffractive structure portion 26a, which are formed periodically at a pitch P, may be gradually modulated. As shown in Fig. 6(b) , the heights of the convex portions of the diffraction grating 31b may be gradually decreased or gradually increased.

[0036] As shown in FIG. 6C, the diffraction gratings 31c of the first diffractive structure portion 25a, the second diffractive structure portion 25b, and the third diffractive structure portion 26a may have a slant angle θ3.

[0037] The slant angles of the diffraction gratings of the first diffractive structure portion 25 a, the second diffractive structure portion 25 b, and the third diffractive structure portion 26 a may be gradually modulated. As shown in Fig. 6(d), the slant angles may be gradually decreased or increased from the diffraction grating 31 d on the left side of the drawing to the diffraction grating 31 d on the right side of the drawing.

[0038] At least one set of the multiple diffractive structures may have different slant angles. For example, the slant angle of the first diffractive structure 25 a may be larger than the slant angle of the second diffractive structure 25 b. The slant angles of the first diffractive structure 25 a and the second diffractive structure 25 b may be different from the slant angle of the third diffractive structure 26 a, and the first diffractive structure 25 a and the second diffractive structure 25 b may have shapes such that the directions in which the propagating light enters are different and the direction in which the image light exits is the same.

[0039] At least a part of the first diffractive structure portion 25a and the second diffractive structure portion 25b constituting the second extension portion may have a diffraction efficiency that decreases toward the non-diffractive structure portion 27. The lower the height of the diffraction grating, the lower the diffraction efficiency. This configuration will be described with reference to Fig. 7. Fig. 7 is an explanatory diagram illustrating modulation of the height of each diffractive structure portion.

[0040] The diffraction efficiency of the first diffractive structure portion 25a decreases along the first direction toward the non-diffractive structure portion 27. To achieve this, for example, the height of the diffractive structure, i.e., the height h of the diffraction grating, decreases as the distance increases in the first direction (Y-axis direction). Furthermore, the diffraction efficiency of the third diffractive structure portion 26a gradually increases and then decreases along the first direction from the first diffractive structure portion 25a toward the second diffractive structure portion 25b. To achieve this, for example, the height of the diffractive structure, i.e., the height h of the diffraction grating, decreases as the distance increases in the first direction (Y-axis direction). Furthermore, the diffraction efficiency of the second diffractive structure portion 25b decreases along the negative first direction toward the non-diffractive structure portion 27. To achieve this, for example, the height of the diffractive structure, i.e., the height h of the diffraction grating, decreases as the distance increases in the negative first direction.

[0041] 8A and 8B are explanatory diagrams showing the relationship between the diffraction efficiency of the diffractive structure and the image. Fig. 8A shows the diffraction efficiency of the first extension portion 25, Fig. 8B shows the diffraction efficiency of the second extension portion 26, and Fig. 8C shows the image visually recognized by the observer. In Fig. 8A and 8B, the darker parts of the first extension portion 25 and the second extension portion 26 indicate areas with high diffraction efficiency, and the lighter parts indicate areas with low diffraction efficiency.

[0042] 7, the diffraction efficiency of the first extension portion 25 and the second extension portion 26 is reduced in the overlapping regions as seen by the viewer, i.e., the overlapping region between the first diffractive structure portion 25a and the third diffractive structure portion 26a and the overlapping region between the second diffractive structure portion 25b and the third diffractive structure portion 26a. This reduces the difference in light intensity between the light beam L4 diffracted and emitted from each overlapping region and the light beam L4 diffracted and emitted from regions other than the overlapping regions. This reduces the occurrence of color unevenness in the image Iv, as shown in FIG. 8C.

[0043] In contrast, as shown in Figures 9(a) and 9(b), if the first extension section 25 and the second extension section 26 are diffraction gratings 31a with uniform diffraction efficiency as shown in Figure 6(a), a difference in light intensity occurs between the light beam L4 diffracted and emitted from the overlapping region and the light beam L4 diffracted and emitted from a region other than the overlapping region. This may result in color unevenness in the image Iv, as shown in Figure 9(c). However, even in this case, image distortion, blur, and the like can be reduced.

[0044] Next, a modification of the first embodiment will be described with reference to Fig. 10. Fig. 10 is a longitudinal cross-sectional view of a light guide according to the modification of the first embodiment. In this modification of the first embodiment, the first extension section 25A has three or more diffractive structure sections, and the second extension section 26A has two or more diffractive structure sections. This allows the viewing area Ac to be enlarged.

[0045] [1-2. Effects, etc.] The light guide 13 as an optical system of the present disclosure includes an incident section 20 that receives a light beam L1 of image light from the display section 11 and changes the traveling direction of the incident light beam L1, and an extension section that divides and replicates the image light traveling from the incident section 20. The extension section includes a first extension section 25 disposed on the first main surface 14 and a second extension section 26 disposed on a second main surface 15 different from the first main surface 14. The first extension section 25 includes a first diffractive structure section 25a and a second diffractive structure section 25b that divide and replicate the image light along a first direction, and a non-diffractive structure section 27 disposed between the first diffractive structure section 25a and the second diffractive structure section 25b. The second extension section 26 includes a third diffractive structure section 26a that divides and replicates the image light along a second direction. The third diffractive structure section 26a is positioned to overlap the non-diffractive structure section 27 of the first extension section 25 from the user's perspective.

[0046] The non-diffractive structure portion 27 arranged between the first diffractive structure portion 25a and the second diffractive structure portion 25b is arranged so as to overlap with the third diffractive structure portion 26a of the second extension portion 26, thereby compensating for image light traveling toward the user between the first diffractive structure portion 25a and the second diffractive structure portion 25b.

[0047] 11 and 12, an image display device 1B according to a second embodiment will be described. In the first embodiment, the first extension section 25 and the second extension section 26 are arranged on the same light guide 13, but in the second embodiment, they are arranged on different light guides 13. Apart from this point and the points described below, the image display device 1 according to the first embodiment and the image display device 1B according to the second embodiment have the same configuration.

[0048] The image display device 1B of the second embodiment includes a display unit 11 and a light guide group 12. The light guide group 12 includes a light guide 13Ba and a light guide 13Bb. A first extension portion 25 is disposed on the first main surface 14Ba of the light guide 13Ba, and a second extension portion 26 is disposed on the second main surface 15Bb of the light guide 13Bb. A portion of the light beam L1 incident on the incident portion 20 of the light guide 13Ba passes through the incident portion 20 and enters the incident portion 20 of the light guide 13Bb, where a portion of the light beam L1 is diffracted and propagates within the light guide 13Bb. Furthermore, a portion of the light beam L1 incident on the incident portion 20 of the light guide 13Ba is diffracted and propagates within the light guide 13Ba. The light beam L1 incident on the incident portion 20 of the light guide 13Bb is diffracted by the third extension portion 23 of the light guide 13Bb and further diffracted to the second extension portion 26. The incident portion 20 and the coupling portion 21 and the third extension portion 23 may be arranged in reverse left-right.

[0049] The third diffractive structure portion 26a of the second extension portion 26 of the light guide 13Bb is arranged to overlap with the non-diffractive structure portion 27 of the first extension portion 25 of the light guide 13Ba when viewed from the user's perspective. Therefore, similar to the first embodiment, it is possible to compensate for the image light traveling toward the user between the first diffractive structure portion 25a and the second diffractive structure portion 25b.

[0050] (Other Embodiments) As described above, the above-mentioned embodiments have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Therefore, other embodiments will be described below as examples.

[0051] In the above embodiment, the diffractive structure portion is divided and arranged in the first direction, but this is not limiting. As shown in Fig. 13, the diffractive structure portion may be divided and arranged in the second direction.

[0052] The arrangement pattern and overlap pattern of each diffractive structure portion can be modified in various ways. As shown in Fig. 14, diffractive structures 25Da, 25Db, and 25Dc of the first extension portion are arranged along the first direction, with non-diffractive structures 27 sandwiched between them. Diffractive structures 26Da and 26Db of the second extension portion may be arranged along the first direction so as to overlap with the respective non-diffractive structures 27. The non-diffractive structures 27 are arranged in a direction perpendicular to the propagation direction of the image light.

[0053] 15 , diffractive structure portions 25Ea and 25Eb of the first extension portion may be arranged along the second direction with a non-diffractive structure portion 27 sandwiched therebetween, and diffractive structure portions 26Ea, 26Eb, and 26Ec of the second extension portion may be arranged along the second direction. The diffractive structure portion 26Eb of the second extension portion is arranged to overlap with the non-diffractive structure portion 27. The non-diffractive structure portion 27 is arranged in a direction parallel to the propagation direction of the image light.

[0054] 16 , diffractive structure portions 25Fa, 25Fb, and 25Fc of the first extension portion may be arranged along the first direction with non-diffractive structure portions 27 sandwiched therebetween, and diffractive structure portions 26Fa, 26Fb, 26Fc, 26Fd, 26Fe, and 26Ff of the second extension portion may be arranged along the second direction. Diffractive structure portions 26Fa to 26Ff of the second extension portion are arranged so as to overlap with portions of the respective non-diffractive structure portions 27. The non-diffractive structure portions 27 arranged on the first main surface 14 and the non-diffractive structure portions 27 arranged on the second main surface 15 extend in different directions.

[0055] 17, the diffractive structure portions of the first extension portion and the second extension portion are not limited to rectangles, but may be triangles, other quadrilaterals, or polygons. For example, the diffractive structure portions 25Ga and 26Gd of the first extension portion are triangles, and the diffractive structure portions 25Gb and 25Gc of the first extension portion are parallelograms. A non-diffractive structure portion 27 is disposed between the hypotenuses of each diffractive structure portion. The diffractive structure portions 26Ga to 26Gd of the second extension portion are disposed so as to overlap with a portion of each non-diffractive structure portion 27. For example, the diffractive structure portions 26Ga and 26Gd of the second extension portion are triangles, and the diffractive structure portions 26Gb and 26Gc of the second extension portion are parallelograms.

[0056] In the above embodiment, one extension section is formed by the plurality of diffractive structure sections of the first extension section 25 and the second extension section 26. However, this is not limiting. In the third extension section 23, one extension section may be formed by a plurality of diffractive structure sections divided into regions.

[0057] (Summary of Embodiments) (1) An optical system disclosed herein includes an incident section that receives image light from a display section and changes the traveling direction of the incident image light, and an extension section that divides and replicates the image light traveling from the incident section. The extension section includes a first extension section disposed on a first surface and a second extension section disposed on a second surface different from the first surface. The first extension section includes a first diffractive structure section and a second diffractive structure section having a diffractive structure that divides and replicates the image light along a first direction, and a non-diffractive structure section that is disposed between the first diffractive structure section and the second diffractive structure section and does not have a diffractive structure. The second extension section includes a third diffractive structure section that divides and replicates the image light along the first direction. The third diffractive structure section is disposed so as to overlap the non-diffractive structure section of the first extension section in the vertical direction of the pupil extension section.

[0058] Since the non-diffractive structure portion disposed between the first diffractive structure portion and the second diffractive structure portion is disposed so as to overlap with the non-diffractive structure portion of the first extension portion, it is possible to compensate for image light traveling toward the user between the first diffractive structure portion and the second diffractive structure portion, thereby enabling an increase in the size of the extension portion.

[0059] (2) In the optical system of (1), the optical system includes a light-guiding member that guides image light output from the display unit to the user's field of view as an image, and the light-guiding member has an incident portion, a pupil expansion portion, a first surface, and a second surface, and the first surface and the second surface are opposite to each other.

[0060] (3) In the optical system of (1), a first light-guiding member and a second light-guiding member are provided to guide image light output from the display unit to the user's field of view as an image, the first light-guiding member having an incident portion and a first extension portion, and the second light-guiding member having an incident portion and a second extension portion.

[0061] (4) In the optical system of any one of (1) to (3), the length of the non-diffractive structure portion in the direction perpendicular to the first direction is 10 times or more the wavelength of the image light.

[0062] (5) In the optical system according to any one of (1) to (4), the wavelength λ of the image light, the wavelength width Δλ of the image light, and the length Lg of the non-diffractive structure portion in the direction perpendicular to the first direction satisfy the following conditional expression: (λ×λ / Δλ)−Lg>0.

[0063] (6) In the optical system of (2), the relationship between the length Lg1 of overlap between the second diffractive structure section and the third diffractive structure section in the first direction, the thickness t of the light guide member perpendicular to the first direction, and the angle of incidence θ1 of the light beam reflected at the end of the third diffractive structure section on the first direction side to the end of the second diffractive structure section opposite to the first direction satisfies the following conditional expression: Lg1>t×tan θ1

[0064] (7) In the optical system of (2), the relationship between the length Lg2 of the overlap between the first diffractive structure and the third diffractive structure in the first direction, the thickness t of the light guide member perpendicular to the first direction, and the angle of incidence θ2 of the light beam reflected at the end of the third diffractive structure opposite to the first direction, on the end of the first diffractive structure on the first direction side, satisfies the following conditional expression: Lg2>t×tan θ2

[0065] (8) In the optical system of any one of (1) to (7), at least a part of the diffractive structure constituting the pupil expansion portion has a diffraction efficiency that decreases toward the non-diffractive structure portion.

[0066] (9) In the optical system of (1), the first, second, and third diffractive structure portions each have a plurality of diffraction gratings, and the heights of the diffraction gratings in at least two of the first, second, and third diffractive structure portions are different from each other.

[0067] (10) In the optical system of (9), the height of the diffraction grating of the second diffractive structure is greater than the height of the diffraction grating of the third diffractive structure, and the height of the diffraction grating of the third diffractive structure is greater than the height of the diffraction grating of the first diffractive structure. Image light propagates through the first diffractive structure, the third diffractive structure, and the second diffractive structure in that order, and the image light is extracted by each diffractive structure. At this time, the height of the diffractive structure in each diffractive structure is proportional to the amount of extracted light. Therefore, since the remaining amount of light decreases each time image light is extracted, increasing the height of the diffractive structure and increasing the amount of extracted light makes it possible to extract uniform light throughout the entire field of view.

[0068] (11) In the optical system of (1), at least two of the first, second, and third diffractive structure sections have diffraction gratings with different slant angles.

[0069] (12) In the optical system of (11), the slant angle of the diffraction grating of the first diffractive structure is larger than the slant angle of the diffraction grating of the second diffractive structure. This allows the angle of the first diffractive structure to be closer to the propagating light and the angle of the second diffractive structure to be deeper to the propagating light, thereby increasing the efficiency of light when viewed from above and below the viewing area.

[0070] (13) In the optical system of (11), the slant angles of the first diffractive structure and the second diffractive structure are shaped such that the direction in which the propagating light enters is different from the slant angle of the third diffractive structure, but the direction in which the image light exits is the same. This makes the first diffractive structure and the second diffractive structure function as transmission-type diffraction gratings that extract image light toward the user, and the third diffractive structure function as a reflection-type diffraction grating that extracts an image toward the user, making it possible to extract uniform image light without any defects.

[0071] (14) In the optical system of any one of (1) to (13), the first diffractive structure portion and the second diffractive structure portion of the first extension portion and the third diffractive structure portion of the second extension portion have a relief shape.

[0072] (15) In any one of the optical systems (1) to (14), the pupil extension section has a third extension section that splits and replicates the image light traveling from the entrance section into image light traveling in a second direction intersecting the first direction and image light traveling in the first direction, the first extension section and the second extension section are arranged in the first direction of the third extension section, and the light-guiding member has an exit section through which the image light further split and replicated along the first direction by the first extension section and the second extension section exits from the pupil extension section.

[0073] (16) In the optical system according to any one of (1) to (15), the non-diffractive structure is arranged in a direction perpendicular to the propagation direction of the image light.

[0074] (17) In the optical system of any one of (1) to (15), the non-diffractive structure is arranged in a direction parallel to the propagation direction of the image light.

[0075] (18) In the optical system of any one of (1) to (15), the non-diffractive structure portion arranged on the first principal surface and the non-diffractive structure portion arranged on the second principal surface extend in different directions.

[0076] (19) An image display device according to the present disclosure includes the optical system according to any one of (1) to (18) and a display unit that emits image light.

[0077] The present disclosure is applicable to an optical system and an image display device that divides and replicates an image.

[0078] REFERENCE SIGNS LIST 1, 1B Image display device 11 Display section 12 Light guide group 13, 13Ba, 13Bb Light guide 14 First main surface 15 Second main surface 20 Incident section 21 Coupling section 22 Pupil extension section 23 Third extension section 25, 25A First extension section 25a First diffractive structure section 25b Second diffractive structure section 25p Point 26 Second extension section 26a Third diffractive structure section 27 Non-diffractive structure section 29 Exit section 31a Diffraction grating Ac Field of view area D Observer Iv Image L1, L2, L3, L4 Light beam

Claims

1. an incident section to which image light from a display section is incident and which changes the traveling direction of the incident image light; a pupil expansion unit that divides and replicates the image light traveling from the incident unit, The pupil dilation unit is a first extension disposed on the first surface; a second extension portion disposed on a second surface different from the first surface, The first extension portion is a first diffractive structure portion and a second diffractive structure portion each having a diffractive structure that divides and replicates the image light along a first direction; a non-diffractive structure portion that is disposed between the first diffractive structure portion and the second diffractive structure portion and does not have the diffractive structure, the second extension portion has a third diffractive structure portion that divides and replicates image light along the first direction, the third diffractive structure portion is arranged to overlap the non-diffractive structure portion of the first extension portion in a vertical direction of the pupil extension portion, optical system.

2. the optical system includes a light guide member that guides image light output from the display unit to a visual field of the user as an image; the light guiding member has the entrance portion, the pupil extension portion, the first surface, and the second surface, The first surface and the second surface are opposed to each other. The optical system of claim 1 .

3. a first light guiding member and a second light guiding member that guide image light output from the display unit to a visual field of a user as an image; the first light guide member has the incident portion and the first extension portion, the second light guide member has the incident portion and the second extension portion; The optical system of claim 1 .

4. a length of the non-diffractive structure portion in a direction perpendicular to the first direction is 20 times or more the wavelength of the image light; The optical system of claim 1 .

5. The wavelength λ of the image light, the wavelength width Δλ of the image light, and the length Lg of the non-diffractive structure portion in a direction perpendicular to the first direction satisfy the following conditional formula: The optical system of claim 1 . (λ×λ / Δλ)-Lg>0

6. a length Lg1 of overlap between the second diffractive structure portion and the third diffractive structure portion in the first direction, a thickness t of the light guiding member perpendicular to the first direction, and an incident angle θ1 of a light beam reflected at an end of the third diffractive structure portion on the first direction side to an end of the second diffractive structure portion opposite to the first direction satisfy the following conditional formula: The optical system according to claim 2 . Lg1>t×tanθ1

7. a length Lg2 of overlap between the first diffractive structure portion and the third diffractive structure portion in the first direction, a thickness t of the light guiding member perpendicular to the first direction, and an incident angle θ2 of a light beam reflected at an end of the third diffractive structure portion opposite to the first direction, on an end of the first diffractive structure portion on the first direction side, satisfy the following conditional formula: The optical system according to claim 2 . Lg2>t×tanθ2

8. At least a part of the diffractive structure constituting the pupil expansion portion has a diffraction efficiency that decreases toward a non-diffractive structure portion. The optical system of claim 1 .

9. the first, second, and third diffractive structure portions each have a plurality of diffraction gratings; At least two of the first, second, and third diffractive structure units have diffraction gratings with different heights. The optical system of claim 1 .

10. a height of the diffraction grating of the second diffraction structure portion is greater than a height of the diffraction grating of the third diffraction structure portion; a height of the diffraction grating of the third diffraction structure portion is greater than a height of the diffraction grating of the first diffraction structure portion; The optical system of claim 9.

11. At least two of the first, second, and third diffraction structure units have diffraction gratings with different slant angles. The optical system of claim 1 .

12. a slant angle of the diffraction grating of the first diffraction structure portion is larger than a slant angle of the diffraction grating of the second diffraction structure portion; The optical system of claim 11.

13. a slant angle of the first diffractive structure portion and a slant angle of the second diffractive structure portion are shaped such that the direction in which the propagation light is incident is different from the slant angle of the third diffractive structure portion, and the direction in which the image light is emitted is the same; The optical system of claim 11.

14. the first diffractive structure portion and the second diffractive structure portion of the first extension portion and the third diffractive structure portion of the second extension portion have a relief shape; The optical system of claim 1 .

15. the pupil expansion unit has a third expansion unit that divides and replicates the image light traveling from the incident unit into image light traveling in a second direction intersecting the first direction and image light traveling in the first direction, the first extension portion and the second extension portion are arranged in the first direction of the third extension portion, the light guiding member includes an exit portion through which the image light further divided and replicated along the first direction by the first extension portion and the second extension portion is emitted from the pupil extension portion. The optical system according to claim 2 .

16. The non-diffractive structure portion is arranged in a direction perpendicular to the propagation direction of the image light. The optical system of claim 1 .

17. The non-diffractive structure portion is arranged in a direction parallel to the propagation direction of the image light. The optical system of claim 1 .

18. the longitudinal direction of the non-diffractive structure portion arranged on the first surface is different from that of the non-diffractive structure portion arranged on the second surface; The optical system of claim 1 .

19. The optical system of any one of claims 1 to 18; a display unit that emits the image light, Image display device.