Optical system, optical waveguide, and light extracting mirror

Abstract

An optical waveguide includes an optical core, a light extracting mirror, and a partial reflector. The optical core and the partial reflector are configured to propagate an image light along a first direction. The partial reflector extends between a first end and a second end and is configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror and reflect at least a portion of the received propagating image light toward the optical core. The image light propagating along the first direction enters the optical core proximal to the first end and propagates along the first direction toward the second end. For an incident light having the at least the first visible wavelength, an optical reflectance of the partial reflector decreases along the first direction from the first end to the second end.

Description

PA102846W002OPTICAL SYSTEM, OPTICAL WAVEGUIDE, AND LIGHT EXTRACTING MIRRORTechnical Field

[0001] The present disclosure relates to an optical system, an optical waveguide, and a light extracting mirror.Background

[0002] Nowadays, optical waveguides are a promising and space-efficient way to reproduce and project an image across a large area. Optical waveguides may be used in augmented reality (AR) and mixed reality (MR) applications because they can be designed to be fairly transparent to a viewer, allowing the projected image to augment an external environment. Further, optical waveguides may also be used for automotive head up displays (HUDs) to enable a larger field of view (FOV) and a longer virtual image distance (VID) AR HUDs.Summary

[0003] In a first aspect, the present disclosure provides an optical waveguide. The optical waveguide includes an optical core including first and opposing second major surfaces. The first major surface is configured to reflect an image light by total internal reflection. The optical waveguide further includes a light extracting mirror including a plurality of spaced apart substantially parallel at least partially reflective facets. For a substantially collimated substantially normally incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, each of at least a majority of the at least partially reflective facets reflects at least 10% of the incident light. The optical waveguide further includes a partial reflector disposed between the optical core and the light extracting mirror. The first major surface of the optical core and the partial reflector are configured to propagate the image light along a first direction. The partial reflector extends between a first end and a second end. The partial reflector is substantially co-extensive in length and width with the light extracting mirror and has a partial reflector length extending from the first end to the second end. The partial reflector is configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror and reflect at least a portion of the received propagating image light toward the optical core. The image light propagating along the first direction enters the optical core proximal to the first end and propagates along the first direction toward the second end. For an incident light having the at least the first visible wavelength, an optical reflectance of the partial reflector decreases along the first direction from the first end to the second end.

[0004] In a second aspect, the present disclosure provides an optical system. The optical system includes an image forming device configured to form and emit an image. The image includes a central image ray. The optical system further includes the optical waveguide of the first aspect. Thecentral image ray is optically coupled to the optical core and propagates along the optical core as the image light.

[0005] In a third aspect, the present disclosure provides an optical waveguide. The optical waveguide includes an optical core including first and opposing second major surfaces. The first major surface is configured to reflect an image light by total internal reflection. The optical waveguide further includes a light extracting mirror including a plurality of spaced apart substantially parallel at least partially reflective facets. For a substantially collimated substantially normally incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, each of at least a majority of the at least partially reflective facets reflects at least 10% of the incident light. The optical waveguide further includes a partial reflector disposed between the optical core and the light extracting mirror. The first major surface of the optical core and the partial reflector are configured to propagate the image light along a first direction. The partial reflector extends between a first end and a second end. The partial reflector is substantially co-extensive in length and width with the light extracting mirror and has a partial reflector length extending from the first end to the second end. The partial reflector includes a plurality of reflecting sections arranged along the first direction. Each reflecting section of the partial reflector is configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror and reflect at least a portion of the received propagating image light toward the optical core. The image light propagating along the first direction enters the optical core proximal to the first end and propagates along the first direction toward the second end. For an incident light having the at least the first visible wavelength, the reflecting sections in the plurality of reflecting sections have different optical reflectances along the first direction, such that an optical reflectance of a first reflecting section is greater than an optical reflectance of a second reflecting section disposed between the first reflecting section and the second end.

[0006] In a fourth aspect, the present disclosure provides an optical waveguide. The optical waveguide includes an optical core including first and opposing second major surfaces. The first major surface is configured to reflect an image light by total internal reflection. The optical waveguide further includes a light extracting mirror including a plurality of spaced apart substantially parallel at least partially reflective facets. For a substantially collimated substantially normally incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, each of at least a majority of the at least partially reflective facets reflects at least 10% of the incident light. The optical waveguide further includes a partial reflector disposed between the optical core and the light extracting mirror. The first major surface of the optical core and the partial reflector are configured to propagate the image light along a first direction. The partial reflector extends between a first end and a second end. The partial reflector is substantially co-extensive in length and width with the light extracting mirror and has a partialreflector length extending from the first end to the second end. The partial reflector includes a plurality alternating first and second sections arranged along the first direction. Each of the first sections of the partial reflector is configured to receive the propagating image light and reflect at least a portion of the received propagating image light toward the optical core and each of the second sections of the partial reflector is configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror. A first section length of the first sections decreases along the first direction from the first end to the second end and a second section length of the second sections increases along the first direction from the first end to the second end.

[0007] In a fifth aspect, the present disclosure provides a light extracting mirror. The light extracting mirror includes a plurality of spaced apart substantially parallel at least partially reflective facets. Each of the plurality of spaced apart substantially parallel at least partially reflective facets includes a plurality of polymeric layers numbering at least 10 in total. Each of the polymeric layers having an average thickness of less than about 500 nanometers (nm). For a substantially collimated incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, the plurality of polymeric layers reflects at least about 50% of the light incident at an incident angle of greater than about 20 degrees.

[0008] In a sixth aspect, the present disclosure provides an optical waveguide. The optical waveguide includes an optical core configured to propagate an image light therealong primarily by total internal reflection. The optical waveguide further includes the light extracting mirror of the fifth aspect disposed on the optical core. The light extracting mirror is configured to receive the propagating image light and extract, primarily by geometrical reflection, at least portions of the received propagating portions as a plurality of exiting image lights toward a viewer.

[0009] In a seventh aspect, the present disclosure provides an optical waveguide. The optical waveguide includes an optical core including first and opposing second major surfaces. The first major surface is configured to reflect an image light by total internal reflection. The optical waveguide further includes the light extracting mirror of the fifth aspect disposed on the optical core. The optical waveguide further includes a partial reflector disposed between the optical core and the light extracting mirror. The first major surface of the optical core and the partial reflector are configured to propagate the image light along a first direction. The partial reflector extends between a first end and a second end. The partial reflector is substantially co-extensive in length and width with the light extracting mirror and has a partial reflector length extending from the first end to the second end. The partial reflector is configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror and reflect at least a portion of the received propagating image light toward the optical core. For an incident light having the at least the first visible wavelength, the optical reflectance of the partial reflector decreases along the first direction from the first end to the second end.

[0010] In an eighth aspect, the present disclosure provides an optical waveguide. The optical waveguide includes an optical core including first and opposing second major surfaces. The first major surface is configured to reflect an image light by total internal reflection. The optical waveguide further includes a light extracting mirror including a plurality of spaced apart substantially parallel at least partially reflective facets. For a substantially collimated substantially normally incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, each of at least a majority of the at least partially reflective facets reflects at least 10% of the incident light. The optical waveguide further includes a plurality of spacers spaced apart from each other and disposed between the optical core and the light extracting mirror. Each of the plurality of spacers has a different spacer height and define an air gap between the optical core and the light extracting mirror. The first major surface of the optical core and the air gap are configured to propagate the image light along a first direction. The air gap extends between a first end and a second end, is substantially co-extensive in length and width with the light extracting mirror, and has an air gap length extending from the first end to the second end. The air gap is configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror and reflect at least a portion of the received propagating image light toward the optical core. The image light propagating along the first direction enters the optical core proximal to the first end and propagates along the first direction toward the second end. For an incident light having the at least the first visible wavelength, the optical reflectance of the air gap decreases along the first direction from the first end to the second end.

[0011] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.Brief Description of the Drawings

[0012] Exemplary embodiments disclosed herein may be more completely understood in consideration of the following detailed description in connection with the following figures. The figures are not necessarily drawn to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

[0013] FIG. 1 A shows a schematic sectional view of an optical system including an optical waveguide, according to an embodiment of the present disclosure;

[0014] FIG. IB shows a schematic sectional view of an optical system including the optical waveguide, according to another embodiment of the present disclosure;

[0015] FIG. 2 shows a schematic sectional view of a light extracting mirror, according to an embodiment of the present disclosure;

[0016] FIG. 3 shows a schematic sectional view of one of a plurality of spaced apart substantially parallel at least partially reflective facets, according to an embodiment of the present disclosure;

[0017] FIG. 4A shows a schematic view of a partial reflector, according to an embodiment of the present disclosure;

[0018] FIG. 4B shows a schematic sectional view of the partial reflector, according to another embodiment of the present disclosure;

[0019] FIG. 5 shows a schematic view of the optical waveguide, according to another embodiment of the present disclosure;

[0020] FIG. 6A shows a graph depicting an optical reflectivity of the partial reflector, an energy density of the optical waveguide, and an output percent per bounce of the optical waveguide versus a location of the optical waveguide when an average optical absorbance of the partial reflector is about 0%, according to an embodiment of the present disclosure;

[0021] FIG. 6B shows a graph depicting the optical reflectivity, the energy density, and the output percent per bounce versus the location when the average optical absorbance of the partial reflector is about 2%, according to an embodiment of the present disclosure;

[0022] FIG. 6C shows a graph depicting the optical reflectivity, the energy density, and the output percent per bounce versus the location when the average optical absorbance of the partial reflector is about 4%, according to an embodiment of the present disclosure;

[0023] FIG. 6D shows a graph depicting the optical reflectivity, the energy density, and the output percent per bounce versus the location when the average optical absorbance of the partial reflector is about 6%, according to an embodiment of the present disclosure;

[0024] FIG. 7 shows a schematic sectional view of the optical waveguide, according to another embodiment of the present disclosure;

[0025] FIG. 8 shows a schematic sectional view of the optical waveguide, according to another embodiment of the present disclosure;

[0026] FIG. 9 shows a schematic view of the optical waveguide including the light extracting mirror, according to another embodiment of the present disclosure;

[0027] FIG. 10 shows a detailed schematic sectional view of the partially reflective facets of the light extracting mirror of FIG. 9, according to another embodiment of the present disclosure;

[0028] FIG. 11A shows a schematic side view of the optical waveguide disposed in a dashboard, according to an embodiment of the present disclosure; and

[0029] FIG. 11B shows a schematic side view of the optical waveguide disposed in smart glasses, according to an embodiment of the present disclosure.Detailed Description

[0030] In the following description, reference is made to the accompanying figures that form a part thereof and in which various embodiments are shown by way of illustration. It is to beunderstood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

[0031] In the following disclosure, the following definitions are adopted.

[0032] As used herein, all numbers should be considered modified by the term “about”. As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably.

[0033] As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / - 20 % for quantifiable properties).

[0034] The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0035] The term “about”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 5% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0036] As used herein, the terms “first” and “second” are used as identifiers. Therefore, such terms should not be construed as limiting of this disclosure. The terms “first” and “second” when used in conjunction with a feature or an element can be interchanged throughout the embodiments of this disclosure.

[0037] As used herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0038] Nowadays, optical waveguides are a promising and space-efficient way to reproduce and project an image across a large area. Optical waveguides may be used in augmented reality (AR) and mixed reality (MR) applications because they can be designed to be fairly transparent to a viewer, allowing the projected image to augment an external environment. Further, optical waveguides may also be used for automotive head up displays (HUDs) to enable a larger field of view (FOV) and a longer virtual image distance (VID) AR HUDs.

[0039] Waveguide systems generally use a diffractive waveguide or a reflective waveguide. The diffractive waveguide uses a surface grating or a volume hologram technology. This approach may pose some challenges such as low efficiency, requiring special high-index glass, struggling to attain a color and a uniformity of an image displayed for viewing by a viewer, and susceptibility to undesirable rainbow type effects due to bright external lights. The reflective waveguide may allow better performance in several of these metrics and may be designed without the high index glass. The reflective waveguide is manufactured by stacking and bonding layers of glass coated with multilayer reflective coatings and then skiving the stack at appropriate angle and polishing to form a waveguidewith successive angle-dependent reflective mirrors. Therefore, a manufacturing process of the reflective waveguide may be complex, time consuming, and expensive.

[0040] The present disclosure relates to an optical waveguide. The optical waveguide includes an optical core including first and opposing second major surfaces. The first major surface is configured to reflect an image light by total internal reflection. The optical waveguide further includes a light extracting mirror including a plurality of spaced apart substantially parallel at least partially reflective facets. For a substantially collimated substantially normally incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nanometers (nm) to about 680 nm, each of at least a majority of the at least partially reflective facets reflects at least 10% of the incident light. The optical waveguide further includes a partial reflector disposed between the optical core and the light extracting mirror. The first major surface of the optical core and the partial reflector are configured to propagate the image light along a first direction. The partial reflector extends between a first end and a second end. The partial reflector is substantially coextensive in length and width with the light extracting mirror and has a partial reflector length extending from the first end to the second end. The partial reflector is configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror and reflect at least a portion of the received propagating image light toward the optical core. The image light propagates along the first direction, enters the optical core proximal to the first end, and propagates along the first direction toward the second end. For an incident light having the at least the first visible wavelength, the optical reflectance of the partial reflector decreases along the first direction from the first end to the second end.

[0041] The present disclosure separates waveguiding and extraction functions of the optical waveguide into separate layers. Specifically, the partial reflector of the optical waveguide may uniformly transmit the image light spatially along a length of the optical waveguide from the optical core into the light extracting mirror. This may eliminate a need for complex multilayer coatings on the partially reflective facets of the light extracting mirror which may be otherwise required to allow the image light to substantially transmit at one angle of incidence and substantially reflect at other angles of incidence with a spectral uniformity to avoid color changes along the length of the optical waveguide. The optical waveguide of the present disclosure may further eliminate a need for spatially varying the partially reflective facets of the light extracting mirror to enable a uniform luminance profile along the length of the optical waveguide, which typically requires a change in an optical reflectivity of the partially reflective facets or a pitch of the partially reflective facets.

[0042] Therefore, the optical waveguide of the present disclosure including the partial reflector, may include the light extracting mirror which may instead be manufactured with a uniform pitch and any high-reflectivity coating, such as aluminum or silver, or alternately with a uniform series of multilayer optical film based mirrors. Further, the optical waveguide may provide a spatially uniform light output without deficiencies of conventional diffractive waveguides, such as requiring specialhigh-index glass, struggling to attain a color and a uniformity of an image displayed for viewing, and susceptibility to undesirable rainbow type effects due to bright external lights while being easier and cheaper to manufacture than conventional reflective waveguides.

[0043] Referring now to figures, FIG. 1 A shows a schematic sectional view of an optical system 200 including an optical waveguide 100, according to an embodiment of the present disclosure.

[0044] In some embodiments, the optical system 200 includes an image forming device 90 configured to form and emit an image. In some embodiments, the image includes a central image ray.

[0045] The optical waveguide 100 includes an optical core 10. The central image ray is optically coupled to the optical core 10 and propagates along the optical core 10 as an image light 20.

[0046] The optical core 10 includes first and opposing second major surfaces 11, 12. The first major surface 11 is configured to reflect the image light 20 by total internal reflection. In some embodiments, the image light 20 is a polarized image light. In some embodiments, the optical core 10 includes one or more of a glass, a dielectric, and a polymer.

[0047] The optical waveguide 100 further includes a light extracting mirror 40. In some embodiments, the light extracting mirror 40 is disposed on the optical core 10.

[0048] The optical waveguide 100 further includes a partial reflector 30 disposed between the optical core 10 and the light extracting mirror 40. The first major surface 11 of the optical core 10 and the partial reflector 30 are configured to propagate the image light 20 along a first direction FD.

[0049] The partial reflector 30 extends between a first end 14 and a second end 16. The partial reflector 30 is substantially co-extensive in length and width with the light extracting mirror 40 and has a partial reflector length 33 extending from the first end 14 to the second end 16. In some embodiments, an electrical conductivity of the partial reflector 30 decreases along the first direction FD from the first end 14 to the second end 16.

[0050] The partial reflector 30 is configured to receive the propagating image light 20 and transmit at least a portion of the received propagating image light 20 toward the light extracting mirror 40 and reflect at least a portion of the received propagating image light 20 toward the optical core 10.

[0051] Specifically, the partial reflector 30 is configured to transmit at least the portion of the received propagating image light 20 toward the light extracting mirror 40 as a transmitted portion 24. Further, the partial reflector 30 is configured to reflect at least the portion of the received propagating image light 20 toward optical core 10 as a reflected portion 26. In some embodiments, the image light 20 may be interchangeably referred to as “the propagating image light 20”.

[0052] The image light 20 propagating (i.e., the propagating image light 20) along the first direction FD enters the optical core 10 proximal to the first end 14 and propagates along the first direction FD toward the second end 16.

[0053] In some embodiments, the light extracting mirror 40 is configured to receive the transmitted portions (i.e., the transmitted portion 24) of the received propagating image light 20 andextract, primarily by geometrical reflection, at least portions of the received transmitted portions as a plurality of exiting image lights 25.

[0054] In some embodiments, the image light 20 propagating along the optical core 10 enters the optical core 10 via an optical prism 81 disposed on a major surface of the optical core 10. In some embodiments, the major surface of the optical core 10 is the first major surface 11.

[0055] FIG. IB shows a schematic sectional view of an optical system 300 including the optical waveguide 100, according to another embodiment of the present disclosure.

[0056] The optical system 300 is substantially similar to the optical system 200 shown in FIG.1A, with like elements designated by like reference characters. However, the optical system 300 does not include the optical prism 81 as shown in the optical system 200 of FIG. 1A.

[0057] In the illustrated embodiment of FIG. IB, the image light 20 propagating along the optical core 10 enters the optical core 10 via a reflector 80. In some embodiments, the reflector 80 is at least partially embedded in the optical core 10.

[0058] Referring to FIGS. 1 A and IB, in some embodiments, the central image ray is optically coupled to the optical core 10 via the optical prism 81 or the reflector 80 and propagates along the optical core 10 as the image light 20.

[0059] FIG. 2 shows a schematic sectional view of the light extracting mirror 40, according to an embodiment of the present disclosure. The light extracting mirror 40 includes a plurality of spaced apart substantially parallel at least partially reflective facets 41.

[0060] FIG. 3 shows a schematic sectional view of one of the plurality of spaced apart substantially parallel at least partially reflective facets 41, according to an embodiment of the present disclosure. FIG. 3 further illustrates a substantially collimated substantially normally incident light 50.

[0061] Referring to FIGS. 2 and 3, for the substantially collimated substantially normally incident light 50 having at least a first visible wavelength in a visible wavelength range extending from about 420 nanometers (nm) to about 680 nm, each of at least a majority of the at least partially reflective facets 41 reflects at least 10% of the incident light 50.

[0062] In some embodiments, the at least the first visible wavelength includes at least one blue wavelength in a blue wavelength range extending from about 420 nm to about 470 nm, at least one green wavelength in a green wavelength range extending from about 500 nm to about 560 nm, and at least one red wavelength in a red wavelength range extending from about 620 nm to about 680 nm.

[0063] In some embodiments, each of at least the majority of the at least partially reflective facets 41 reflects at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the incident light 50. In some embodiments, each of at least the majority of the at least partially reflective facets 41 reflects about 100% of the incident light 50.

[0064] In some embodiments, each of at least the majority of the at least partially reflective facets 41 transmits at least 10% of the incident light 50. In some embodiments, each of at least themajority of the at least partially reflective facets 41 transmits at least 20%, at least 30%, at least 40%, or at least 50% of the incident light 50.

[0065] FIG. 4A shows a schematic view of the partial reflector 30, according to an embodiment of the present disclosure.

[0066] In some embodiments, the partial reflector 30 includes a metal coating MC. In some embodiments, a metal coating thickness mt of the metal coating MC decreases along the first direction FD from the first end 14 to the second end 16.

[0067] In some embodiments, the metal coating MC is disposed on a substrate 13. In such embodiments, a thickness tl of the partial reflector 30 decreases along the first direction FD from the first end 14 to the second end 16. In some embodiments, the substrate 13 is substantially planer.

[0068] FIG. 4B shows a schematic sectional view of the partial reflector 30, according to another embodiment of the present disclosure.

[0069] Referring to FIGS. 1 A and 4B, in some embodiments, the partial reflector 30 includes a plurality of reflecting sections 31 arranged along the first direction FD. Each reflecting section 31 of the partial reflector 30 is configured to receive the propagating image light 20 and transmit at least a portion (i.e., the transmitted portion 24 shown in FIGS. 1A and IB) of the received propagating image light 20 toward the light extracting mirror 40 and reflect at least a portion (i.e., the reflected portion 26) of the received propagating image light 20 toward the optical core 10.

[0070] For an incident light having the at least the first visible wavelength, the reflecting sections 31 in the plurality of reflecting sections 31 have different optical reflectances along the first direction FD, such that an optical reflectance of a first reflecting section 28a is greater than an optical reflectance of a second reflecting section 28b is disposed between the first reflecting section 28a and the second end 16. In some embodiments, the different optical reflectances are different by at least 0.5%. In some embodiments, the different optical reflectances are different by at least 0.2%, at least 0.3%, at least 0.4%, at least 0.5%, at least 1%, at least 1.5%, at least 2%, at least 02.5%, at least 3%, at least 3.5%, at least 4%, at least 4.5%, or at least 5%.

[0071] In some embodiments, the reflecting sections 31 in the plurality of reflecting sections 31 have different average thicknesses, such that an average thickness ATI of the first reflecting section 28a is greater than an average thickness AT2 of the second reflecting section 28b disposed between the first reflecting section 28a and the second end 16.

[0072] In some embodiments, the reflecting sections 31 in the plurality of reflecting sections 31 includes different materials. In some embodiments, a material of the first reflecting section 28a has a greater electrical conductivity than an electrical conductivity of a material of the second reflecting section 28b disposed between the first reflecting section 28a and the second end 16.

[0073] In some embodiments, the reflecting sections 31 include the metal coating MC. In some embodiments, the metal coating MC is disposed on the substrate 13.

[0074] In some embodiments, the partial reflector 30 may be manufactured via different manufacturing methods, such as by a sputtering method or by an evaporation method.

[0075] The sputtering method may be include developing the partial reflector 30 on a roll-to-roll substrate (e.g., the substrate 13). The partial reflector 30 may be a cross web and done such that a thickness varies from one side of the web to the other. In such cases, a shield may be placed between a sputter cathode and the substrate. The amount of sputtering flux may vary by changing a position of the shield relative to the flux that is being sputtered.

[0076] The position of the shield or a shape of the shield to block more or less of the sputtering flux may be allowed to be changed to match a desired partial reflector 30. For example, if one end of the shield effectively covering the cathode and the opposite side of the cathode is fully open, then the partial reflector 30 will have a linear gradient across the web in the linear portion of a magnetron. Further, the turnarounds may typically be outside of the web path or may be shielded from the web, so they may have little influence on the desired partial reflector 30.

[0077] The evaporation method may use a single evaporation source depositing at one end of a coater which may give a variation in the thickness based off a cosine squared distribution from a thickness variation of the evaporation point source. However, this coating may not be linear gradient, so it may require shielding to block some of the flux. This may be done with either thermal or electron beam evaporation.

[0078] The evaporation method may include centering vapor sources to achieve a thickest coating in the center. This may result, each direction to be mirror images of reduced thickness. Furthermore, a shield could be put in place between the source and the substrate to make the coating linear in each direction if desired for example, thicker in the middle and thinner to each edge.

[0079] The evaporation method may provide the partial reflector 30 from material properties such as conductivity using two different materials, deposited from two different sources at each side of a coating drum. One source may be a highly conductive material, like nickel. And the other source may be a much less conductive material, like silicon monoxide and blend them across the face of the coating drum, so the thicknesses may be relatively similar, but the conductivity will vary dramatically across a width of the web. Further, the thickness may then be tailored with shielding to get linear or specific curve to the conductivity. This may be done so that the metal coating is not so thin as to be unstable when very thin. Instead, there may be a thick metal film on one edge, a relatively thick cermet in the middle and a thick ceramic film on the other edge of the web which may make a stable varied conductive thin film across the width of the web.

[0080] FIG. 5 shows a schematic sectional view of the optical waveguide 100, according to another embodiment of the present disclosure.

[0081] In the illustrated embodiment of FIG. 5, the partial reflector 30 includes a plurality of alternating first and second sections 32a, 32b arranged along the first direction FD.

[0082] Referring to FIGS. 1 A and 5, each of the first sections 32a of the partial reflector 30 is configured to receive the propagating image light 20 and reflect at least the portion (i.e., the reflected portion 26) of the received propagating image light 20 toward the optical core 10 and each of the second sections 32b of the partial reflector 30 is configured to receive the propagating image light 20 and transmit at least the portion (i.e., the transmitted portion 24) of the received propagating image light 20 toward the light extracting mirror 40.

[0083] A first section length LI of the first sections 32a decreases along the first direction FD from the first end 14 to the second end 16 and a second section length L2 of the second sections 32b increases along the first direction FD from the first end 14 to the second end 16.

[0084] In some embodiments, each of the first sections 32a includes a metal or a metal coating (e.g., the metal coating MC shown in FIGS. 4A and 4B). In some other embodiments, each of the first sections 32a includes an opening. In some embodiments, the opening includes air. In some embodiments, each of the second sections 32b includes a material same as of the optical core 10.

[0085] In some embodiments, the optical waveguide 100 includes a bonding layer 35 disposed between the partial reflector 30 and the optical core 10. In some embodiments, the bonding layer 35 includes an optically clear adhesive (OCA).

[0086] In some embodiments, an interface 37 between adjacent first and second sections 32a, 32b includes a light absorptive material 38. The light absorptive material 38 may be coated or otherwise provided on the interface 37. Exemplary light absorptive materials include a black or other light absorbing colorant (such as carbon black or another pigment or dye, or combinations thereof). Other light absorbing materials can include particles or other scattering elements that can function to block light (e.g., the image light 20) from being transmitted through the interface 37.

[0087] FIGS. 6A-6D show graphs 800, 810, 820, 830 depicting an optical reflectivity of the partial reflector 30, an energy density of the optical waveguide 100, and an output percent per bounce of the optical waveguide 100 versus a location of the optical waveguide 100, according to an embodiment of the present disclosure.

[0088] Specifically, the graph 800 depicts the optical reflectivity, the energy density, and the output percent per bounce versus the location when an average optical absorbance of the partial reflector 30 is about 0%.

[0089] The graph 810 depicts the optical reflectivity, the energy density, and the output percent per bounce versus the location when the average optical absorbance of the partial reflector 30 is about 2%.

[0090] The graph 820 depicts the optical reflectivity, the energy density, and the output percent per bounce versus the location when the average optical absorbance of the partial reflector 30 is about 4%.

[0091] The graph 830 depicts the optical reflectivity, the energy density, and the output percent per bounce versus the location when the average optical absorbance of the partial reflector 30 is about 6%.

[0092] The location is provided in abscissa in inches. The optical reflectivity and the energy density is expressed in percentage (%) in the left ordinate, while the output percent per bounce is also expressed in percentage (%) in the right ordinate.

[0093] The graphs 800, 810, 820, 830 include a curve OR depicting the optical reflectivity of the partial reflector 30. The graphs 800, 810, 820, 830 further include a curve OE depicting the energy density of the optical waveguide 100. Further, the graphs 800, 810, 820, 830 further include a curve OI depicting the output percent per bounce of the optical waveguide 100.

[0094] Referring to FIGS. 1 A and 6A-6D, for an incident light having the at least the first visible wavelength, an optical reflectance (indicated by the curve OR) of the partial reflector 30 decreases along the first direction FD from the first end 14 to the second end 16.

[0095] In some embodiments, an optical reflectance of the partial reflector 30 at the first end 14 and an optical reflectance of the partial reflector 30 at the second end 16 are different by at least 5%. In some embodiments, the optical reflectance of the partial reflector 30 at the first end 14 and the optical reflectance of the partial reflector 30 at the second end 16 are different by at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, or at least 85%.

[0096] As is apparent from the graphs 800, 810, 820, 830, the optical reflectance of the partial reflector 30 at the first end 14 and the optical reflectance of the partial reflector 30 at the second end 16 are different by about 90%.

[0097] In some embodiments, an average optical reflectance of a first portion 34 (also shown in FIG. 1A) of the partial reflector 30 extending from the first end 14 to about 70% of the partial reflector length 33 is at least 5% greater than an average optical reflectance of a second portion 36 (also shown in FIG. 1A) of the partial reflector 30 extending from the first portion 34 to the second end 16.

[0098] As is apparent from the graph 800, an optical energy (indicated by the curve OE) of the image light 20 propagating along the optical core 10 decreases linearly along the first direction FD from the first end 14 to the second end 16 when the average optical absorbance of the partial reflector 30 is less than about 1%.

[0099] Further, as is apparent from the graphs 810, 820, 830, the optical energy of the image light 20 propagating along the optical core 10 decreases non-linearly along the first direction FD from the first end 14 to the second end 16 when the average optical absorbance of the partial reflector 30 is equal or greater than about 2%.

[0100] As is apparent from the graphs 800, 810, 820, 830, the energy density of the image light 20 at entrance of the optical core 10 is high. At every interaction with the partial reflector 30, aportion of the image light 20 is transmitted into the light extracting mirror 40 while remainder, minus any absorption in the partial reflector 30, continues to propagate down the optical core 10. Therefore, the energy density in the optical core 10 drops along the first direction FD.

[0101] As is apparent from the graphs 800, 810, 820, 830, an optical intensity (i.e., indicated by the curve OI) of an exiting image light (i.e., the plurality of exiting image lights 25 shown in FIG. 1A) at the first end 14 is substantially equal to an optical intensity of an exiting image light at the second end 16. Therefore, in some embodiments, the optical intensity of the exiting image lights 25 remains substantially constant along the first direction FD from the first end 14 to the second end 16.

[0102] Therefore, the optical reflectivity of the partial reflector 30 may be designed to drop along the length of the optical waveguide 100 in such a way that the light transmitted (i.e., the transmitted portion 24) through it into the light extracting mirror 40 may be constant.

[0103] For the graphs 800 to 830, the image light 20 bounces about 29 times off the partial reflector 30. Since the output percent per bounce (shown by the curve OI) decreases as the average optical absorbance of the partial reflector 30 increases, a total efficiency of the optical waveguide 100 may also decrease. Specifically, a loss of the optical energy may multiply with an increase in the average optical absorbance of the partial reflector 30. Therefore, the optical waveguide 100 having a lesser average optical absorbance of the partial reflector 30 may have a better total efficiency. In some embodiments, the average optical absorbance of the partial reflector 30 is less than about 10%.

[0104] In the illustrated example of FIG. 6A, the output percent per bounce is about 3.1%. Therefore, the total efficiency of the optical waveguide 100 is about 90%. In the illustrated example of FIG. 6B, the output percent per bounce is about 2.24%. Therefore, the total efficiency of the optical waveguide 100 is about 65%. In the illustrated example of FIG. 6C, the output percent per bounce is about 1.5%. Therefore, the total efficiency of the optical waveguide 100 is about 44%. In the illustrated example of FIG. 6D, the output percent per bounce is about 0.96%. Therefore, the total efficiency of the optical waveguide 100 is about 28%.

[0105] FIG. 7 shows a schematic view of the optical waveguide 100, according to another embodiment of the present disclosure.

[0106] In the illustrated embodiment of FIG. 7, the partial reflector 30 includes a low index layer 39 having a refractive index less than a refractive index of each of the optical core 10 and the light extracting mirror 40. In some embodiments, the refractive index of the low index layer 39 is less than the refractive index of each of the optical core 10 and the light extracting mirror 40 by at least a factor of 1.1. In some embodiments, a thickness t2 of the low index layer 39 decreases along the first direction FD from the first end 14 to the second end 16.

[0107] In some embodiments, the thickness t2 may be less than 1 micrometer (pm) down to 100 nm, depending on the refractive index of the low index layer 39.

[0108] Since the partial reflector 30 including the low index layer 39 does not include any metal layer (e.g., the metal coating MC shown in FIGS. 4A-4B), the partial reflector 30 of FIG. 7 may havea very low average optical absorbance. Therefore, the optical energy of the image light 20 propagating along the optical core 10 decreases linearly along the first direction FD from the first end 14 to the second end 16.

[0109] FIG. 8 shows a schematic sectional view of an optical waveguide 101, according to another embodiment of the present disclosure.

[0110] In the illustrated embodiment of FIG. 8, the optical waveguide 101 is substantially similar to the optical waveguide 100 shown in FIG. 1A, with like elements designated by like reference characters.

[0111] The optical waveguide 101 includes the optical core 10 and the light extracting mirror 40. However, the optical waveguide 100 does not include the partial reflector 30 (shown in FIG. 1A). Instead, the optical waveguide 101 includes a plurality of spacers 60.

[0112] The plurality of spacers 60 are spaced apart from each other and disposed between the optical core 10 and the light extracting mirror 40. Each of the plurality of spacers 60 has a different spacer height SHI, SH2 and define an air gap 46 between the optical core 10 and the light extracting mirror 40.

[0113] The first major surface 11 of the optical core 10 and the air gap 46 are configured to propagate the image light 20 (shown in FIG. 1A) along a first direction FD’. The air gap 46 extends between a first end 54 and a second end 56 and is substantially co-extensive in length and width with the light extracting mirror 40 and has an air gap length 44 extending from the first end 54 to the second end 56. The image light 20 propagating (i.e., the propagating image light 20) along the first direction FD’ enters the optical core 10 proximal to the first end 54 and propagates along the first direction FD’ toward the second end 56.

[0114] The air gap 46 is configured to receive the propagating image light 20 and transmit at least the portion (i.e., the transmitted portion 24 shown in FIG. 1A) of the received propagating image light 20 toward the light extracting mirror 40 and reflect at least the portion (i.e., the reflected portion 26 shown in FIG. 1A) of the received propagating image light 20 toward the optical core 10. For an incident light having the at least the first visible wavelength, an optical reflectance of the air gap 46 decreases along the first direction FD’ from the first end 54 to the second end 56.

[0115] In some embodiments, the spacer height SHI of a first spacer 62 in the plurality of spacers 60 is greater than the spacer height SH2 of a second spacer 64 in the plurality of spacers 60 disposed between the first spacer 62 and the second end 56.

[0116] Since the air gap 46 may have a very low average optical absorbance, the optical energy of the image light 20 propagating along the optical core 10 decreases linearly along the first direction FD’ from the first end 54 to the second end 56.

[0117] FIG. 9 shows a schematic view of the optical waveguide 100 including the light extracting mirror 40, according to another embodiment of the present disclosure. FIG. 10 shows adetailed schematic sectional view of the at least partially reflective facets 41 of the light extracting mirror 40 of FIG. 9, according to another embodiment of the present disclosure.

[0118] Referring to FIGS. 9 and 10, in some embodiments, each of the plurality of spaced apart substantially parallel at least partially reflective facets 41 includes a plurality of polymeric layers 150 numbering at least 10 in total. Each of the polymeric layers 150 has an average thickness T of less than about 500 nm.

[0119] For a substantially collimated incident light (e.g., the image light 20) having the at least first visible wavelength in the visible wavelength range, the plurality of polymeric layers 150 reflects at least about 50% of the incident light incident at an incident angle of greater than about 20 degrees.

[0120] In some embodiments, the plurality of polymeric layers 150 includes a plurality of alternating first and second polymeric layers 152, 154. In some embodiments, each of the plurality of spaced apart substantially parallel at least partially reflective facets 41 further includes at least one skin layer 156 having an average thickness ST of greater than about 500 nm.

[0121] In the illustrated embodiment of FIG. 10, the at least one skin layer 156 includes a pair of skin layers 156, and the plurality of polymeric layers 150 is disposed between the pair of skin layers 156. The at least one skin layer 156 may protect the plurality of polymeric layers 150 and may also provide mechanical stability to the at least partially reflective facets 41. In some cases, the at least one skin layer 156 may act as a protective boundary layer (PBL).

[0122] Referring to FIGS. 9 and 10, in some embodiments, the light extracting mirror 40 is configured to receive the propagating image light 20 and extract, primarily by geometrical reflection, at least portions of the received propagating portions as the plurality of exiting image lights 25 toward a viewer 70.

[0123] In some embodiments, the light extracting mirror 40 is configured to receive the transmitted portions 24 of the received propagating image light 20 and extract, primarily by geometrical reflection, at least portions of the received transmitted portions 24 as the plurality of exiting image lights 25 toward the viewer 70. As discussed above, in some embodiments, the image light 20 may be a polarized image light.

[0124] Further, the plurality of polymeric layers 150 may transmit at least about 30% of an incident light 142 from a real-world scene 140 toward the viewer 70. Therefore, the viewer 70 may view an object (not shown) in the real-world scene 140 through the optical waveguide 100. In other words, the viewer 70 may view the object in the real-world scene 140 through the light extracting mirror 40, the partial reflector 30, and the optical core 10. Therefore, in some cases, the optical waveguide 100 may be fairly transparent.

[0125] FIG. 11A shows a schematic side view of the optical waveguide 100, according to another embodiment of the present disclosure.

[0126] The optical waveguide 100 of FIG. 11A is disposed in a dashboard 125. In some embodiments, the optical waveguide 100 may be disposed in the dashboard 125 of a vehicle. Theoptical waveguide 100 may therefore be used in a heads up display (HUD) system. In the illustrated embodiment of FIG. 11 A, the vehicle may further include a windshield 120 and a reflective polarizer 110. Referring to FIGS. 1 and 11 A, the reflective polarizer 110 is configured to reflect at least a portion of the exiting image lights 25 toward the viewer 70.

[0127] FIG. 11B shows a schematic side view of the optical waveguide 100, according to an embodiment of the present disclosure.

[0128] The optical waveguide 100 of FIG. 11B is disposed in smart glasses 130. The optical waveguide 100 may therefore be used in the smart glasses 130 for augmented reality (AR) applications.

[0129] In the illustrated embodiment of FIG. 11B, the smart glasses 130 may also include the reflective polarizer 110 to reflect at least a portion of the exiting image lights 25 toward the viewer 70. Referring to FIGS. 1 and 11B, the smart glasses 130 may include lenses 135. In some embodiments, the lenses 135 may include the reflective polarizer 110.

[0130] Referring to FIGS. lAto 11B, the optical waveguide 100, 101 separates waveguiding and extraction functions of the optical waveguide 100, 101 into separate layers. Specifically, the partial reflector 30 or the air gap 46 of the optical waveguide 100, 101 may uniformly transmit the image light 20 spatially along a length of the optical waveguide 100, 101 from the optical core 10 into the light extracting mirror 40. This may eliminate a need for complex multilayer coatings on the partially reflective facets 41 of the light extracting mirror 40 which may be otherwise required to allow the image light 20 to substantially transmit at one angle of incidence and substantially reflect at other angles of incidence with a spectral uniformity to avoid color changes along the length of the optical waveguide 100, 101. The optical waveguide 100, 101 may further eliminate a need for spatially varying the partially reflective facets 41 of the light extracting mirror 40 to enable a uniform luminance profile along the length of the optical waveguide 100, 101, which typically requires a change in an optical reflectivity of the partially reflective facets 41 or a pitch of the partially reflective facets 41.

[0131] Therefore, the optical waveguide 100, 101 including the partial reflector 30 or the air gap 46, may include the light extracting mirror 40 which may instead be manufactured with a uniform pitch and any high-reflectivity coating, such as aluminum or silver, or alternately with a uniform series of multilayer optical film based mirrors. Further, the optical waveguide 100, 101 may provide a spatially uniform light output without deficiencies of conventional diffractive waveguides, such as requiring special high-index glass, struggling to attain a color and a uniformity of an image displayed for viewing, and susceptibility to undesirable rainbow type effects due to bright external lights while being easier and cheaper to manufacture than conventional reflective waveguides.

[0132] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in theforegoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0133] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

CLAIMS1. An optical waveguide comprising:an optical core comprising first and opposing second major surfaces, the first major surface configured to reflect an image light by total internal reflection;a light extracting mirror comprising a plurality of spaced apart substantially parallel at least partially reflective facets, such that for a substantially collimated substantially normally incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, each of at least a majority of the at least partially reflective facets reflects at least 10% of the incident light; anda partial reflector disposed between the optical core and the light extracting mirror, the first major surface of the optical core and the partial reflector configured to propagate the image light along a first direction, the partial reflector extending between a first end and a second end, the partial reflector substantially co-extensive in length and width with the light extracting mirror and having a partial reflector length extending from the first end to the second end, the partial reflector configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror and reflect at least a portion of the received propagating image light toward the optical core,the image light propagating along the first direction enters the optical core proximal to the first end and propagates along the first direction toward the second end,for an incident light having the at least the first visible wavelength, an optical reflectance of the partial reflector decreases along the first direction from the first end to the second end.

2. The optical waveguide of claim 1, wherein an average optical reflectance of a first portion of the partial reflector extending from the first end to about 70% of the partial reflector length is at least 5% greater than an average optical reflectance of a second portion of the partial reflector extending from the first portion to the second end.

3. The optical waveguide of claim 1, wherein an optical energy of the image light propagating along the optical core decreases non-linearly along the first direction from the first end to the second end when an average optical absorbance of the partial reflector is equal or greater than about 2%.

4. The optical waveguide of claim 1, wherein the light extracting mirror is configured to receive the transmitted portions of the received propagating image light and extract, primarily by geometrical reflection, at least portions of the received transmitted portions as a plurality of exiting image lights toward a reflective polarizer.

5. The optical waveguide of claim 1, wherein a thickness of the partial reflector decreases along the first direction from the first end to the second end.

6. The optical waveguide of claim 1, wherein an electrical conductivity of the partial reflector decreases along the first direction from the first end to the second end.

7. The optical waveguide of claim 1, wherein the at least the first visible wavelength comprises at least one blue wavelength in a blue wavelength range extending from about 420 nm to about 470 nm, at least one green wavelength in a green wavelength range extending from about 500 nm to about 560 nm, and at least one red wavelength in a red wavelength range extending from about 620 nm to about 680 nm.

8. The optical waveguide of claim 1, wherein the image light propagating along the optical core enters the optical core via a reflector at least partially embedded in the optical core.

9. An optical system comprising:an image forming device configured to form and emit an image, the image comprising a central image ray; andthe optical waveguide of claim 1, wherein the central image ray is optically coupled to the optical core and propagates along the optical core as the image light.

10. An optical waveguide comprising:an optical core comprising first and opposing second major surfaces, the first major surface configured to reflect an image light by total internal reflection;a light extracting mirror comprising a plurality of spaced apart substantially parallel at least partially reflective facets, such that for a substantially collimated substantially normally incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, each of at least a majority of the at least partially reflective facets reflects at least 10% of the incident light; anda partial reflector disposed between the optical core and the light extracting mirror, the first major surface of the optical core and the partial reflector configured to propagate the image light along a first direction, the partial reflector extending between a first end and a second end, the partial reflector substantially co-extensive in length and width with the light extracting mirror and having a partial reflector length extending from the first end to the second end, the partial reflector comprising a plurality of reflecting sections arranged along the first direction, each reflecting section of the partial reflector configured to receive the propagating image light and transmit at least a portion of the receivedpropagating image light toward the light extracting mirror and reflect at least a portion of the received propagating image light toward the optical core,the image light propagating along the first direction enters the optical core proximal to the first end and propagates along the first direction toward the second end,for an incident light having the at least the first visible wavelength, the reflecting sections in the plurality of reflecting sections have different optical reflectances along the first direction, such that an optical reflectance of a first reflecting section is greater than an optical reflectance of a second reflecting section disposed between the first reflecting section and the second end.

11. The optical waveguide of claim 10, wherein the different optical reflectances are different by at least 0.5%.

12. An optical waveguide comprising:an optical core comprising first and opposing second major surfaces, the first major surface configured to reflect an image light by total internal reflection;a light extracting mirror comprising a plurality of spaced apart substantially parallel at least partially reflective facets, such that for a substantially collimated substantially normally incident light having at least a first visible wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, each of at least a majority of the at least partially reflective facets reflects at least 10% of the incident light; anda partial reflector disposed between the optical core and the light extracting mirror, the first major surface of the optical core and the partial reflector configured to propagate the image light along a first direction, the partial reflector extending between a first end and a second end, the partial reflector substantially co-extensive in length and width with the light extracting mirror and having a partial reflector length extending from the first end to the second end, the partial reflector comprising a plurality of alternating first and second sections arranged along the first direction, each of the first sections of the partial reflector configured to receive the propagating image light and reflect at least a portion of the received propagating image light toward the optical core and each of the second sections of the partial reflector configured to receive the propagating image light and transmit at least a portion of the received propagating image light toward the light extracting mirror,a first section length of the first sections decreases along the first direction from the first end to the second end and a second section length of the second sections increases along the first direction from the first end to the second end.

13. The optical waveguide of claim 12, wherein each of the first sections comprise an opening.

14. The optical waveguide of claim 12, wherein each of the second sections comprise a material same as of the optical core.

15. The optical waveguide of claim 12, wherein an interface between adjacent first and second sections comprises a light absorptive material.

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