Display structure and display device

Abstract

A display structure (1000) and a display device are disclosed. The display structure (1000) comprises a waveguide (1100) having a first surface (1110) and a second surface (1120), and an output coupling grating (1200) disposed on the first surface (1110) and configured to couple light (1101) out via the second surface (1120). The output coupling grating (1200) comprises a primary ridge (1210) having a first end (1211) facing a secondary lateral direction (1202), a first ridge portion (1213) extending from the first end (1211) towards the primary lateral direction (1201) opposite the secondary lateral direction (1202), a second end (1212) facing the primary lateral direction (1201), and a second ridge portion (1215) extending from the second end (1212) towards the secondary lateral direction (1202). The first ridge portion (1213) has a first height h1 and the second ridge portion (1215) has a second height h2 less than the first height h1.

Description

[Technical field]

[0001] The present disclosure relates to display devices, and in particular to waveguide-based display devices with diffractive out-coupling gratings and structures thereof. [Background technology]

[0002] Out-coupling gratings in waveguide-based display devices typically couple light from the waveguide both towards and away from the user's eyes. In many applications, such as head-mounted see-through display devices (e.g., smart glasses), coupling light away from the user's eye or eyes, i.e. towards the outside world, may be undesirable for a variety of reasons, including energy efficiency, information security, and aesthetics.

[0003] Conventionally, the out-coupling of light to the world side by different out-coupling gratings is reduced by the use of various thin film stacks placed below or above the out-coupling grating. While such approaches can provide display devices with acceptable out-coupling efficiency characteristics, conventional solutions exhibit light leakage that can be excessive, especially for TM-polarized input light. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above, it may be desirable to develop new solutions related to out-coupling gratings for waveguide-based display devices. [Means for solving the problem]

[0005] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0006] According to a first aspect, a display structure is provided. The display structure comprises a waveguide having a first surface and a second surface for confining light in the waveguide by total internal reflection. The second surface is disposed in a thickness direction from the first surface. The display structure further comprises a diffractive out-coupling grating disposed on the first surface. The out-coupling grating is configured to couple light from the waveguide via the second surface. The out-coupling grating comprises a primary ridge and a secondary ridge parallel to the primary ridge. The secondary ridge is disposed in a primary lateral direction from the primary ridge. The primary ridge comprises a first end facing in a secondary lateral direction opposite the primary lateral direction, a first ridge portion extending from the first end in the primary lateral direction, a second end facing in the primary lateral direction, and a second ridge portion extending from the second end in the secondary lateral direction. The first ridge portion has a first height measured along the thickness direction and the second ridge portion has a second height measured along the thickness direction, the second height being less than the first height.

[0007] According to a second aspect there is provided a display device comprising a display structure according to the first aspect.

[0008] The present disclosure will be better understood from the following detailed description read in light of the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1] 1 shows a cross-sectional view of a display structure. [Diagram 2] 1 shows a cross-sectional view of another display structure. [Diagram 3] Indicates a display device.

[0010] Unless specifically noted to the contrary, any of the foregoing drawings may not be drawn to scale, such that elements of any of the drawings may be drawn in inaccurate proportions relative to other elements of the drawings, in order to emphasize particular structural aspects of the embodiments of the drawings.

[0011] Furthermore, corresponding elements in the embodiments of any two of the aforementioned drawings may be out of proportion to each other in the two drawings in order to highlight particular structural aspects of the embodiments of the two drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] FIG. 1 illustrates a partial cross-sectional view of a display structure 1000 according to one embodiment, and an expanded view of a portion of the display structure 1000.

[0013] As used herein, a "display device" may refer to an operable output device, e.g., an electronic device, for visually displaying images and / or data. A display device may generally include any parts or elements necessary or useful for visually displaying images and / or data, such as a power supply unit, an optical engine, a combiner optical unit (e.g., a waveguide-based combiner optical unit), an eye-tracking unit, a head-tracking unit, a gesture sensing unit, and / or a depth mapping unit. A display device may or may not be a portable display device (e.g., a head-mounted display device and / or a see-through display device).

[0014] As used herein, a "head mounted display device" may refer to a display device configured to be worn on the head as part of a piece of headgear and / or worn on or over the eyes.

[0015] Additionally, a "see-through display device" or "transparent display device" can refer to a display device that allows a user to see images and / or data displayed on the display device rather than just looking through the display device.

[0016] Throughout this disclosure, a "display structure" can refer to at least a portion of an operational display device. Additionally or alternatively, a display structure can refer to a structure suitable for use in a display device.

[0017] In the embodiment of FIG. 1, the display structure 1000 comprises a waveguide 1100 .

[0018] In this disclosure, a "waveguide" can refer to an optical waveguide. Additionally or alternatively, a waveguide can refer to a two-dimensional waveguide, where light is confined along the thickness of the waveguide.

[0019] 1 comprises a first surface 1110 and a second surface 1120 for confining light 1101 within the waveguide 1100 by total internal reflection. The second surface is disposed opposite the first surface 1110 and in a thickness direction 1102 therefrom.

[0020] In this disclosure, a "face" of a waveguide may refer to a portion of the surface of the waveguide that is visible from or faces a particular line of sight. Additionally or alternatively, a face of a waveguide may refer to a surface that is suitable or configured to confine light within the waveguide by total internal reflection.

[0021] In the embodiment of FIG. 1, the display structure 1000 also includes a diffractive out-coupling grating 1200 disposed on the first surface 1110 .

[0022] As used herein, a "diffraction grating" can refer to an optical grating whose operation is based on the diffraction of visible light. Generally, a diffraction grating can comprise one or more structural features having at least one dimension on the order of the wavelength of visible light (e.g., at least one dimension less than 1 micrometer). Generally, a diffraction grating can be implemented as a single-domain diffraction grating or as a multi-domain diffraction grating. A diffraction grating can generally be implemented as at least a surface relief diffraction grating or a volume holographic diffraction grating, and can be configured to function as a transmission and / or reflection type diffraction grating. Of course, a "diffractive output coupling grating" can refer to a diffraction grating configured to couple light from a waveguide. Generally, a diffractive output coupling grating can be further configured to perform exit pupil expansion by pupil duplication.

[0023] As used herein, "exit pupil expansion" can refer to a process of distributing light within a waveguide in a controlled manner to expand the portion of that waveguide where out-coupling of light occurs. Additionally, "pupil duplication" can refer to an exit pupil expansion process where multiple exit sub-pupils are formed within an imaging system.

[0024] The output coupling grating 1200 is configured to couple the light 1101 out of the waveguide 1100 via the second surface 1120. The output coupling grating 1200 is thus configured to function as a reflective grating.

[0025] The output coupling grating 1200 of the embodiment of Figure 1 comprises a primary ridge 1210 and a secondary ridge 1220 parallel to the primary ridge 1210. In Figure 1, each of the primary ridges 1210 and the secondary ridges 1220 extend longitudinally perpendicular to the plane of the drawing, and the secondary ridges 1220 are disposed in a primary lateral direction 1201 from the primary ridge 1210.

[0026] 1, the primary ridge 1210 comprises a first end 1211 facing in a secondary transverse direction 1202 opposite the primary transverse direction 1201, and a first ridge portion 1213 extending from the first end 1211 towards the primary transverse direction 1201. The primary ridge 1210 also comprises a second end 1212 facing in the primary transverse direction 1201, and a second ridge portion 1215 extending from the second end 1212 towards the secondary transverse direction 1202.

[0027] In the embodiment of FIG. 1, the first ridge portion 1213 has a first height (h1) measured along the thickness direction 1102, and the second ridge portion 1215 has a second height (h2) measured along the thickness direction 1102, the second height (h2) being less than h1. In general, the first ridge portion having a first height and the second ridge portion having a second height less than the first height may enable an increase in the out-coupling efficiency of light to one or both eyes of a user and / or an increase in the ratio of the out-coupling efficiency of light to one or both eyes of a user to the out-coupling efficiency to the world side. The out-coupling efficiency of light to one or both eyes of a user may be significantly larger for both TE polarized input light and TM polarized input light. Compared to conventional solutions, such an increase in out-coupling efficiency may be observed especially for TM polarized input light.

[0028] As used herein, the "height" of a ridge portion may refer to a measure of the extent of the ridge portion along the thickness direction of the waveguide. Where an out-coupling grating comprises a primary ridge and a secondary ridge, the out-coupling grating may comprise a gap between the primary ridge and the secondary ridge, and the height of the ridge portion of the primary ridge may be measured from the lowest point of the gap to the highest point of the ridge portion.

[0029] In the embodiment of FIG. 1, the out-coupling grating 1200 is specifically configured to out-couple light 1101, which is confined within the waveguide 1100 by total internal reflection and directed towards the first transverse direction 1201. In other embodiments, the out-coupling grating may or may not be configured to couple light directed from the waveguide in the first transverse direction through its second surface. For example, in some embodiments, the out-coupling grating can be configured to couple light directed in any suitable direction, e.g., perpendicular to the thickness direction and forming an acute angle with the first transverse direction (e.g., an angle of 45° or less, or 30° or less, or 20° or less, or 15° or less, or 10° or less, or 5° or less).

[0030] The out-coupling grating 1200 of the embodiment of Figure 1 is configured to perform exit pupil expansion by pupil replication along a first order transverse direction 1201. In other embodiments, the out-coupling grating may or may not be configured to perform exit pupil expansion by pupil replication at least along the first order transverse direction, i.e., along the first order transverse direction and optionally along one or more other directions perpendicular to the thickness direction.

[0031] In the embodiment of FIG. 1, the height ratio between h2 and h1 (r h ) can be about 0.7. In other embodiments, any suitable height ratio (e.g., a height ratio of 0.45 or more, or 0.5 or more, or 0.55 or more, or 0.6 or more, and / or 0.9 or less, or 0.85 or less, or 0.8 or less, or 0.75 or less) can be used.

[0032] 1, h1 may be about 65 nm. In other embodiments, the first ridge portion may have any suitable first height (e.g., a first height of 40 nm or more, or 45 nm or more, or 50 nm or more, and / or 200 nm or less, or 180 nm or less, or 160 nm or less).

[0033] 1, h2 may be about 45 nm. In other embodiments, the second ridge portion may have any suitable second height (e.g., a second height of 20 nm or more, or 25 nm or more, or 30 nm or more, and / or 150 nm or less, or 140 nm or less, or 120 nm or less).

[0034] The display structure 1000 of the embodiment of FIG. 1 includes a coating 1300 on the first surface 1110, with the out-coupling grating 1200 formed within the coating 1300. In general, an out-coupling grating formed within the coating can facilitate manufacturing of the display structure and / or facilitate tuning of the diffraction efficiency of the out-coupling grating without changing the refractive index of the waveguide. In other embodiments, the display structure may or may not include a coating on the first surface of the waveguide. In embodiments in which the display structure includes a coating on the first surface of the waveguide, the out-coupling grating may or may not be formed within the coating. In some embodiments, the out-coupling grating may be at least partially (i.e., partially or entirely) formed within the waveguide.

[0035] The waveguide 1100 of the embodiment of FIG. VIS ), and the coating 1300 includes a first material having a first refractive index (n1) at λ VISIn some embodiments, the coating comprises a second material having a second refractive index (n2) higher than n1 at visible wavelengths. Typically, a coating comprising a second material having a second refractive index higher than the first refractive index allows for a reduction in the first height of the first ridge portion and the second height of the second ridge portion, which in turn may facilitate manufacturing of the display structure and / or increase the ratio of the output coupling efficiency to one or both eyes of a user to the output coupling efficiency to the world. In other embodiments in which the waveguide comprises, consists essentially of, or consists of a first material having a first refractive index at visible wavelengths, the coating may comprise, consist essentially of, or consist of, or may not comprise, consist essentially of, or consist of a second material having a second refractive index higher than the first refractive index at visible wavelengths.

[0036] In the embodiment of FIG. VIS The refractive index difference (Δn) between n2 and n1 in the embodiment may be about 0.7. In general, a higher refractive index difference may further increase the efficiency of light out-coupling to the user's eye or eyes and / or increase the ratio of the efficiency of out-coupling to the user's eye or eyes to the efficiency of out-coupling to the world. In other embodiments, any suitable refractive index difference between the second refractive index and the first refractive index may be used. For example, in some embodiments, a refractive index difference of 0.3 or more, or 0.4 or more, or 0.5 or more, or 0.6 or more, or 0.7 or more may be used.

[0037] In the embodiment of FIG. VIS n2 can be approximately 2 at λ VIS In other embodiments, any suitable refractive index can be used. For example, in some embodiments, n1 can be about 2.7 at λ VIS In such embodiments, n2 can be, for example, 2.2 or more, or 2.3 or more, and / or 3 or less, or 2.8 or less.

[0038] For the embodiment of FIG. 1, the values ​​of n1, n2, and Δn are set to λ 500 nm. VIS In other embodiments, the values ​​of n1, n2, and Δn can be considered at any suitable visible wavelength (i.e., any wavelength within the spectral range spanning 380 nm to 760 nm). For example, in some embodiments, the relevant visible wavelengths can be selected from the group consisting of 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, and 650 nm.

[0039] 1 embodiment may be, for example, a high index glass, and the second material of the coating 1300 may be, for example, titanium dioxide (TiO2). In other embodiments, any suitable material(s) may be used as the first material and / or the second material, for example, glass(s), inorganic material(s) such as oxide material(s), and / or nitride material(s), or organic polymer(s).

[0040] In the embodiment of FIG. 1, as shown in FIG. 1, the output coupling grating 1200 has a period (d) and an inter-ridge distance (d) measured along the primary lateral direction 1201 between the primary ridges 1210 and the secondary ridges 1220. ir The output coupling grating 1200 has a d ir The distance ratio between and d (r d ). In general, a lower distance ratio may increase the efficiency of light being out-coupled into the user's eye or eyes and / or increase the ratio of the efficiency of light being out-coupled into the user's eye or eyes to the efficiency of light being out-coupled into the world. In other embodiments, any suitable distance ratio may be used (e.g., a distance ratio of 0.25 or less, or 0.2 or less, or 0.15 or less, or 0.1 or less).

[0041] For the embodiment of Figure 1, d can be about 340 nm. In other embodiments, any suitable periodicity can be used (e.g., a periodicity of 300 nm or more, or 310 nm or more, or 320 nm or more, or 325 nm or more, and / or 470 nm or less, or 460 nm or less, or 450 nm or less, or 440 nm or less).

[0042] In the embodiment of FIG. ir can be about 30 nm. In other embodiments, any suitable inter-ridge distance can be used (e.g., an inter-ridge distance of 15 nm or more, or 20 nm or more, or 25 nm or more, or 30 nm or more, and / or 100 nm or less, or 80 nm or less, or 60 nm or less, or 50 nm or less).

[0043] The first ridge portion 1213 of the embodiment of FIG. 1 is adjacent to the second ridge portion 1215, and the primary ridge 1210 includes a stair structure 1217 disposed between the first ridge portion 1213 and the second ridge portion 1215. Thus, the out-coupling grating 1200 of the embodiment of FIG. 1 is realized as a three-level (i.e., two-step) stair grating. In general, the use of a stair grating, such as a three-level stair grating, in a display structure may facilitate the manufacture of the display structure. In other embodiments, the first ridge portion of the primary ridge may or may not be adjacent to the second ridge portion of the primary ridge, and the primary ridge may or may not include a stair structure disposed between the first ridge portion and the second ridge portion.

[0044] 1, the first ridge portion 1213 includes a first lateral outer surface 1214 extending from the first end wall 1211, and the second ridge portion 1215 includes a second lateral outer surface 1216 extending from the second end wall. In other embodiments, the first ridge portion may or may not include such a first lateral outer surface and / or the second ridge portion may or may not include such a second lateral outer surface.

[0045] 1, the first ridge portion 1213 has a first width (w1) measured along the primary lateral direction 1201, and the second ridge portion 1215 has a second width (w2) measured along the primary lateral direction 1201 that is greater than w1. In other embodiments where the first ridge portion is adjacent to the second ridge portion, the second width of the second ridge portion may or may not be greater than the first width of the first ridge portion. In some embodiments, the second ridge portion can have a second width that is less than or equal to the first width of the first ridge portion.

[0046] In the embodiment of FIG. 1, the width ratio of w2 to w1 (r w ) can be about 1.4. In other embodiments in which a first ridge portion is adjacent to a second ridge portion, any suitable width ratio can be used. In other embodiments in which the second width of the second ridge portion is greater than the first width of the first ridge portion, width ratios of, for example, 1.1 or more, or 1.2 or more, or 1.3 or more, or 1.4 or more, and / or 3 or less, or 2.8 or less, or 2.6 or less, or 2.5 or less, or 2.4 or less can be used.

[0047] 1, w1 can be about 130 nm. In other embodiments in which a first ridge portion is adjacent to a second ridge portion, the first ridge portion can have any suitable first width (e.g., a first width of 80 nm or more, or 100 nm or more, or 120 nm or more, and / or 300 nm or less, 280 nm or less, or 260 nm or less).

[0048] 1, w2 can be about 180 nm. In other embodiments in which a first ridge portion is adjacent to a second ridge portion, the second ridge portion can have any suitable second width (e.g., a second width of 100 nm or more, or 120 nm or more, or 140 nm or more, and / or 300 nm or less, 280 nm or less, or 260 nm or less).

[0049] In the embodiment of FIG. 1, the output coupling grating 1200 is configured to minimize the coupling of light 1101 out of the waveguide 1100 via the first face 1110. In particular, r h , h1, h2, r w , w1, w2, r d , d, and d ir each of the ridges is selected to minimize coupling of light 1101 from the waveguide 1100 towards the world. In other embodiments, the output coupling grating may or may not be configured to minimize coupling of light from the waveguide through the first face. In embodiments in which the output coupling grating is configured to minimize coupling of light from the waveguide through the first face, one or more of the height ratio, first height, second height, width ratio, first width, second width, distance ratio, period, and inter-ridge distance may be selected to minimize coupling of light from the waveguide through the first face.

[0050] The display structure 1000 of the embodiment of Figure 1 may have been formed at least in part using nanoimprint lithography. In other embodiments, any suitable method or methods (e.g., nanoimprint lithography and / or grayscale electron beam lithography) may be used.

[0051] 1 embodiment, the out-coupling grating 1200 comprises a plurality of ridges having the same cross-sectional shape as the primary ridges 1210. In particular, the secondary ridges 1220 have the same shape as the primary ridges 1210. In other embodiments, the out-coupling grating may or may not comprise a plurality (i.e., two or more, three or more, four or more, etc.) of ridges having the same cross-sectional shape as the primary ridges of the out-coupling grating. In embodiments where the out-coupling grating comprises a plurality of ridges having the same cross-sectional shape as the primary ridges of the out-coupling grating, the secondary ridges may or may not have the same shape as the primary ridges.

[0052] Figure 2 illustrates a display structure 2000 according to one embodiment. The embodiment of Figure 2 may follow any of the embodiments disclosed with reference to and / or in conjunction with Figure 1. Additionally or alternatively, although not explicitly shown in Figure 2, the embodiment of Figure 2 or any portion thereof may generally comprise any configuration and / or element of the embodiment of Figure 1 that is omitted in Figure 2.

[0053] Similar to the display structure 1000 of the embodiment of Figure 1, the display structure 2000 of the embodiment of Figure 2 comprises a diffractive out-coupling grating 2200 disposed on the first surface 1110 of the waveguide 1100 and configured to couple light 1101 from the waveguide 1100 via the second surface 1120 of the waveguide 1100. However, the cross-sectional shapes of the primary ridges 2210 and secondary ridges 2220 of the out-coupling grating 2200 are different from the cross-sectional shapes of the primary ridges 1210 and secondary ridges 1220 of the out-coupling grating 1200 of the embodiment of Figure 1.

[0054] In a manner similar to the primary ridge 1210 of the embodiment of Figure 1, the primary ridge 2210 of the embodiment of Figure 2 comprises a first end 2211 facing in a secondary transverse direction 1202 opposite the primary transverse direction 1201, a first ridge portion 2213 extending from the first end 2211 towards the primary transverse direction 1201, a second end 2212 facing in the primary transverse direction 1201, and a second ridge portion 2215 extending from the second end 2212 towards the secondary transverse direction 1202. The first ridge portion 2213 has a first height (h1) measured along the thickness direction 1102. The second ridge portion 2215 has a second height (h2) measured along the thickness direction 1102, the second height (h2) being less than h1.

[0055] 1 embodiment, the first ridge portion 2213 comprises a lateral first outer surface 2214 extending from the first end 2211, the second ridge portion 2215 comprises a lateral second outer surface 2216 extending from the second end 2212, and the primary ridge 2210 comprises an intermediate ridge portion 2218 comprising an inclined intermediate outer surface 2219 extending from the first ridge portion 2213 to the second ridge portion 2215 and connecting the first outer surface 2214 and the second outer surface 2216. In general, such an intermediate ridge portion may further increase the efficiency of light out-coupling into the user's eye or eyes and / or increase the ratio of the efficiency of out-coupling into the user's eye or eyes to the efficiency of out-coupling into the world.

[0056] In the embodiment of FIG. 2, r between h2 and h1 h For example, h1 may be about 90 nm, while h2 may be about 55 nm.

[0057] The output coupling grating 2200 of the embodiment of FIG. ir r between and d d For example, d can be about 370 nm, and d ir can be about 40 nm.

[0058] In the embodiment of FIG. 2, r between w2 and w1 w can be about 0.9. In other embodiments in which the primary ridge comprises an intermediate ridge portion with a sloping intermediate outer surface, any suitable width ratio can be used (e.g., a width ratio of 0.8 or more, or 0.9 or more, or 1.0 or more, or 1.1 or more, and / or 2 or less, or 1.8 or less, or 1.6 or less, or 1.4 or less).

[0059] For the embodiment of Figure 2, w1 can be about 110 nm. In other embodiments in which the primary ridge includes an intermediate ridge portion with a sloping intermediate outer surface, the first ridge portion can have any suitable first width (e.g., a first width of 60 nm or more, or 80 nm or more, or 100 nm or more, and / or 300 nm or less, or 280 nm or less, or 260 nm or less).

[0060] In the embodiment of Figure 2, w2 can be about 100 nm. In other embodiments in which the primary ridge comprises an intermediate ridge portion with a sloping intermediate outer surface, the second ridge portion can have any suitable second width (e.g., a second width of 60 nm or more, or 80 nm or more, or 100 nm or more, and / or 300 nm or less, or 280 nm or less, or 260 nm or less).

[0061] 2, the intermediate ridge portion 2218 has a third width (w3) measured along the primary lateral direction 1201, the third width (w3) being greater than both of w1 and w2. In other embodiments in which the primary ridge includes an intermediate ridge portion with a sloped intermediate outer surface, the intermediate ridge portion may or may not have a third width greater than w1 and / or w2. In some embodiments, the intermediate ridge portion may have a third width less than or equal to w1 and / or w2.

[0062] In the embodiment of Figure 2, w3 can be about 120 nm. In other embodiments in which the primary ridge includes an intermediate ridge portion with a sloping intermediate outer surface, the intermediate ridge portion can have any suitable third width (e.g., a third width of 60 nm or more, or 80 nm or more, or 100 nm or more, and / or 300 nm or less, or 280 nm or less, or 260 nm or less).

[0063] The above mainly describes the structural and material related features of the display structure. The following focuses on the features related to the display device. The above-mentioned implementation methods, definitions, details and advantages apply mutatis mutandis to the display device aspects described below, and vice versa.

[0064] Figure 3 illustrates a display device 3000 according to one embodiment. The embodiment of Figure 3 may follow any of the embodiments disclosed with reference to and / or in conjunction with any of Figures 1 and 2. Additionally or alternatively, although not explicitly shown in Figure 3, the embodiment of Figure 3 or any portion thereof may generally comprise any configuration and / or element of any of the embodiments of Figures 1 and 2 that are omitted in Figure 3.

[0065] 3, the display device 3000 is implemented as a see-through head-mounted display device, and more specifically, as glasses with a see-through display. In other embodiments, the display device may be implemented in any suitable manner, for example, as a see-through display device and / or a head-mounted display device.

[0066] In the embodiment of Figure 3, the display device 3000 comprises a frame 3100 and a display structure 3200 according to the first aspect supported by the frame 3100. In other embodiments, the display device may or may not comprise such a frame.

[0067] 3 embodiment, the display structure 3200 comprises a waveguide 3210, an input coupling grating 3220 for coupling light 3201 into the waveguide 3210, an intermediate pupil extension structure 3230 configured to receive the light 3201 from the input coupling grating 3220, and a reflective output coupling grating 3240 configured to receive the light 3201 from the intermediate pupil extension structure 3230. In other embodiments, the display structure may or may not comprise such an input coupling grating and / or such an intermediate pupil extension structure.

[0068] 5, the display device 3000 further comprises an optical engine 3250 configured to guide the light 3201 into the waveguide 3210 for propagation therein by total internal reflection. In other embodiments, the display device may or may not comprise such an optical engine.

[0069] Some examples are described below.

[0070] In a first example, the first example display structure, the first reference display structure, and the second reference display structure provide a λ of about 520 nm in a display device that provides a 15° field of view (FOV). VIS The three display structures were designed and optimized for monochromatic illumination of 1000 nm. After optimizing these three display structures, their output coupling efficiency characteristics were calculated and compared.

[0071] The first example display structure included a waveguide, an input coupling grating, and a diffractive three-level stepped output coupling grating. The reference display structure was substantially identical to the example display structure. However, instead of the stepped output coupling grating, the first and second reference display structures were provided with a binary output coupling grating and a tilted output coupling grating, respectively. Each of these output coupling gratings was configured for one-dimensional exit pupil expansion with pupil replication along the first-order lateral direction, and received light directly from the input coupling grating in the absence of an intermediate pupil expansion structure.

[0072] The results show that the eye-to-world outcoupling efficiency ratio (

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[0073] For the first example display structure,

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[0074] Furthermore, the results show that the eye-side outcoupling efficiency (

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[0075] For the first example display structure,

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[0076] In a second example, the display structure of the second example provides a luminance of approximately 520 nm in a display device providing a 15° FOV.

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[0077] The display structure of the second example included the same waveguides and in-coupling gratings as those of the display structure of the first example. However, the display structure of the second example included a diffractive out-coupling grating with a ridge, where an intermediate ridge portion with a sloping intermediate outer surface extends from a first ridge portion with a lateral first outer surface to a second ridge portion with a lateral second outer surface, with the intermediate outer surface connecting the first outer surface and the second outer surface. In other words, the ridges of the out-coupling grating of the display structure of the second example had a shape similar to that of the out-coupling grating 2200 of the embodiment of FIG. 2.

[0078] According to the results, the display structure of the second example

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[0079] Further, the display structure of the second example

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[0080] In the first and second examples above, the display structures of the first and second examples, as well as the first and second reference display structures, were designed and optimized for use with both TE and TM polarized input light. Of course, a display structure optimized to use only one of the TE and TM polarized input light would have a higher value of

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[0081] It is obvious to those skilled in the art that with the advancement of technology, the basic idea of ​​the present invention can be implemented in various ways. Therefore, the present invention and its embodiments are not limited to the above examples, but can be modified within the scope of the claims.

[0082] It will be understood that any of the above benefits and advantages may relate to one or several embodiments, and the embodiments are not limited to those that solve some or all of the described problems or have any or all of the described benefits and advantages.

[0083] The term "comprising" is used herein to mean including the subsequent structure(s) or activity(ies) without excluding the presence of one or more additional structures or activities. Further, reference to "an" or "an" item will be understood to refer to one or more of those items. [Explanation of symbols]

[0084] h1 First height h2 Second height r h = h2 / h1 height ratio d period d ir Ridge Distance r d =d ir / d distance ratio w1 First width w2 Second width w3 Third width r w =w2 / w1 width ratio n1 first refractive index n2 Second refractive index λ VIS visible wavelength Δn=n2-n1 refractive index difference

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Claims

1. A display structure (1000) comprising a waveguide (1100) and a diffractive output coupling grating (1200), wherein the waveguide (1100) comprises a first surface (1110) and a second surface (1120) for confining light (1101) within the waveguide (1100) by total internal reflection, and the second surface (1120) is arranged in a thickness direction (1102) from the first surface (1110), the output coupling grating (1200) is arranged on the first surface (1110) and is configured to couple the light (1101) from the waveguide (1100) through the second surface (1120), the output coupling grating (1200) comprises a primary ridge (1210) and a secondary ridge (1220) parallel to the primary ridge (1210), and the secondary ridge (1220) is arranged in a primary lateral direction (1201) from the primary ridge (1210), the primary ridge (1210) comprises a first end portion (1211) facing a secondary lateral direction (1202) opposite to the primary lateral direction (1201), a first ridge portion (1213) extending in the primary lateral direction (1201) from the first end portion (1211), a second end portion (1212) facing the primary lateral direction (1201), and a second ridge portion (1215) extending in the secondary lateral direction (1202) from the second end portion (1212), The first ridge portion (1213) has a first height h measured along the thickness direction (1102). １ The second ridge portion (1215) has a second height h measured along the thickness direction (1102), which is smaller than the first height h. １ The height ratio r between the second height h ２ and the first height h ２ is 0.45 or more, and the display structure (1000). １ ｈ ​​

2. the second height h ２ and the first height h １ the height ratio r therebetween ｈ is 0.5 or more, or 0.55 or more, or 0.6 or more, and / or 0.9 or less, or 0.85 or less, or 0.8 or less, or 0.75 or less, the display structure (1000) according to claim 1.

3. The display structure (1000) comprises a coating (1300) on the first surface (1110), and the output coupling grating (1200) is formed within the coating (1300). The display structure (1000) according to claim 1 or 2.

4. The waveguide (1100) has a first refractive index n ＶＩＳ at a visible wavelength λ １ and includes a first material, and the coating (1300) has a second refractive index n ＶＩＳ higher than the first refractive index n １ at the visible wavelength λ ２ and includes a second material. The display structure (1000) according to claim 3.

5. the visible wavelength λ ＶＩＳ of the second refractive index n ２ and the first refractive index n １ and the refractive index difference Δn therebetween is 0.3 or more, or 0.4 or more, or 0.5 or more, or 0.6 or more, or 0.7 or more, the display structure (1000) according to claim 4.

6. The visible wavelength λ ＶＩＳ is selected from the group consisting of 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, and 650 nm, the display structure (1000) according to claim 4.

7. The output coupling diffraction grating (1200) has a period d and a ridge-to-ridge distance d measured along the primary lateral direction (1201) between the primary ridge (1210) and the secondary ridge (1220). ｉｒ and has the ridge-to-ridge distance d ｉｒ and a distance ratio r between the ridge-to-ridge distance d ｄ and the period d is 0.25 or less, or 0.2 or less, or 0.15 or less, or 0.1 or less. The display structure (1000) according to claim 1 or 2.

8. The first ridge portion (1213) is adjacent to the second ridge portion (1215), and the primary ridge (1210) comprises a stepped structure (1217) arranged between the first ridge portion (1213) and the second ridge portion (1215). The display structure (1000) according to claim 1 or 2.

9. The first ridge portion (1213) has a first width w measured along the primary lateral direction (1201). １ The second ridge portion (1215) has a second width w, which is larger than the first width w and is measured along the primary lateral direction (1201). １ The display structure (1000) according to claim 8, having the above features. ２ ​

10. the first width w １ and the second width w ２ and the width ratio r ｗ is 1.1 or more, or 1.2 or more, or 1.3 or more, or 1.4 or more, and / or 3 or less, or 2.8 or less, or 2.6 or less, or 2.5 or less, or 2.4 or less, the display structure (1000) according to claim 9.

11. The first ridge portion (2213) includes a first outer surface (2214) in the lateral direction extending from the first end portion (2211), the second ridge portion (2215) includes a second outer surface (2216) in the lateral direction extending from the second end portion (2212), the primary ridge (2210) includes an intermediate ridge portion (2218), the intermediate ridge portion (2218) extends from the first ridge portion (2213) to the second ridge portion (2215), and includes an inclined intermediate outer surface (2219) connecting the first outer surface (2214) and the second outer surface (2216). The display structure (1000) according to claim 1 or 2.

12. The output coupling diffraction grating (1200) is configured to perform exit pupil expansion by pupil replication at least along the primary lateral direction (1201). The display structure (1000) according to claim 1 or 2.

13. The output coupling diffraction grating (1200) is configured to minimize the coupling of light (1101) from the waveguide (1100) through the first surface (1110). The display structure (1000) according to claim 1 or 2.

14. A display device (3000) comprising the display structure (3200) according to claim 1 or 2.

15. The display device (3000) according to claim 14, realized as a see-through display device.

16. The display device (3000) according to claim 14, realized as a head-mounted display device.

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