Light extracting mirror and method of manufacturing light extracting mirror

Abstract

A light extracting mirror includes a plurality of alternating partially reflective facets and interlayers. Each of the plurality of partially reflective facets includes a plurality of polymeric layers and at least one skin layer. For a substantially collimated incident light from within a medium and having at least a first visible wavelength in a visible wavelength range, each of at least a majority of the partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees. For the substantially collimated incident light, each of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle.

Description

PA103774W002LIGHT EXTRACTING MIRROR AND METHOD OF MANUFACTURING LIGHT EXTRACTING MIRRORTechnical Field

[0001] The present disclosure relates to a light extracting mirror and a method of manufacturing the light extracting mirror.Background

[0002] Currently, several types of lightguides in augmented reality (AR) systems are in development, each of them having own manufacturing and performance challenges. Lightguides made with partial reflectors immersed in a transparent material are known in the display industry. These lightguides may produce very good image quality but can be expensive and difficult to manufacture. Typically, these lightguides in the AR systems are made with borosilicate glass plates and vapor deposited thin film coatings, which can be very difficult to assemble into a multilayer reflective lightguide.

[0003] Therefore, a reflective lightguide for augmented reality system which has a good optical performance while having a simple manufacturing process at low cost is desired.Summary

[0004] In a first aspect, the present disclosure provides a light extracting mirror. The light extracting mirror includes a plurality of alternating partially reflective facets and interlayers. Each of the plurality of partially reflective facets includes a plurality of polymeric layers and at least one skin layer disposed on the plurality of polymeric layers. The at least one skin layer has an average thickness of greater than about 500 nanometers (nm). Each of the plurality of polymeric layers has an average thickness of less than about 500 nm. For a substantially collimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees. For the substantially collimated incident light from within the medium and having the at least first visible wavelength in the visible wavelength range, each of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle.

[0005] In a second aspect, the present disclosure provides a light extracting mirror. The light extracting mirror includes a plurality of alternating partially reflective facets and interlayers. Each of the plurality of partially reflective facets includes a plurality of polymeric layers and at least one skinlayer disposed on the plurality of polymeric layers. The at least one skin layer includes polyethylene terephthalate (PET) and has an average thickness of greater than about 500 nanometers (nm). Each of the plurality of polymeric layers has an average thickness of less than about 500 nm. The plurality of interlayers includes polymethyl methacrylate (PMMA). The light extracting mirror further includes a coating layer disposed between the at least one skin layer and an adjacent interlayer from the plurality of interlayers. For a substantially collimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees. For the substantially collimated incident light from within the medium and having the at least first visible wavelength in the visible wavelength range, each of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle.

[0006] In a third aspect, the present disclosure provides a light extracting mirror. The light extracting mirror includes a plurality of alternating partially reflective facets and interlayers. Each of the plurality of partially reflective facets includes a plurality of polymeric layers and at least one skin layer disposed on the plurality of polymeric layers. The at least one skin layer has an average thickness of greater than about 500 nanometers (nm). The plurality of polymeric layers has an average thickness of less than about 500 nm. For a substantially collimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees. For the substantially collimated incident light from within the medium and having the at least first visible wavelength in the visible wavelength range, each of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle. At least one of an Sa roughness, an Sq roughness, and an Svk roughness of at least one of opposing first and second major surfaces of the light extracting mirror is less than about 0.06 microns.

[0007] In a fourth aspect, the present disclosure provides a light extracting mirror. The light extracting mirror includes a plurality of alternating partially reflective facets and interlayers. Each of the plurality of partially reflective facets includes a plurality of polymeric layers. The plurality of polymeric layers and at least one skin layer disposed on the plurality of polymeric layers. The at least one skin layer has an average thickness of greater than about 500 nanometers (nm). Each of the plurality of polymeric layers has an average thickness of less than about 500 nm. For a substantiallycollimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees. For the substantially collimated incident light from within the medium and having the at least first visible wavelength in the visible wavelength range, each of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle. An adhesion between the partially reflective facet and an adjacent interlayer from the interlayers is at least 20 Newtons.

[0008] In a fifth aspect, the present disclosure provides a method of manufacturing a light extracting mirror. The method includes providing a plurality of partially reflective facets. Each of the plurality of partially reflective facets includes a plurality of polymeric layers and at least one skin layer disposed on the plurality of polymeric layers. The at least one skin layer has an average thickness of greater than about 500 nanometers (nm). Each of the plurality of polymeric layers has an average thickness of less than about 500 nm. The method further includes providing a plurality of interlayers. Further, the method includes stacking the plurality of partially reflective facets and the interlayers in an alternating manner. Further, the method includes applying heat and pressure on the stack of the plurality of alternating partially reflective facets and interlayers to obtain a slab.Furthermore, the method includes cutting a portion of the slab at a cutting angle to obtain a mirror portion. The method further includes polishing at least one of opposing first and second major surfaces of the mirror portion to obtain the light extracting mirror. For a substantially collimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees. For the substantially collimated incident light from within the medium and having the at least first visible wavelength in the visible wavelength range, each of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle. Further, an adhesion between the partially reflective facet and an adjacent interlayer from the interlayers is at least 20 Newtons.

[0009] 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

[0010] 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.

[0011] FIG. 1 A shows a schematic sectional view of an optical waveguide and a light extracting mirror, according to an embodiment of the present disclosure;

[0012] FIG. IB shows a schematic sectional view of the optical waveguide and the light extracting mirror, according to another embodiment of the present disclosure;

[0013] FIG. 2 shows a detailed sectional view of a partially reflective facet, according to an embodiment of the present disclosure;

[0014] FIG. 3 shows a flowchart of a method of manufacturing the light extracting mirror shown in FIGS. 1 A and IB, according to an embodiment of the present disclosure;

[0015] FIG. 4 shows schematic steps of the method, according to an embodiment of the present disclosure;

[0016] FIG. 5 shows an exemplary bar graph depicting Sa and Sq roughness for a conventional light extracting mirror and the light extracting mirror;

[0017] FIG. 6 shows an exemplary bar graph depicting Svk roughness for the conventional light extracting mirror and the light extracting mirror;

[0018] FIG. 7 shows an exemplary bar graph depicting X and Y slope sigmas for the conventional light extracting mirror and the light extracting mirror; and

[0019] FIG. 8 shows an exemplary graph depicting adhesion properties for exemplary samples of the light extracting mirror and a comparative sample.Detailed Description

[0020] 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 be understood 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.

[0021] In the following disclosure, the following definitions are adopted.

[0022] 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.

[0023] 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 aperson of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / -20% for quantifiable properties).

[0024] 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.

[0025] 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.

[0026] 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.

[0027] As used herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0028] Currently, several types of lightguides in augmented reality (AR) systems are in development, each of them having own manufacturing and performance challenges. Lightguides made with partial reflectors immersed in a transparent material are known in the display industry. These lightguides may produce very good image quality but can be expensive and difficult to manufacture. Typically, these lightguides in the AR systems are made with borosilicate glass plates and vapor deposited thin film coatings, which can be very difficult to assemble into a multilayer reflective lightguide.

[0029] Therefore, a reflective lightguide for augmented reality system which has a good optical performance while having a simple manufacturing process at low cost is desired.

[0030] The present disclosure relates to a light extracting mirror. The light extracting mirror includes a plurality of alternating partially reflective facets and interlayers. Each of the plurality of partially reflective facets includes a plurality of polymeric layers and at least one skin layer disposed on the plurality of polymeric layers. The at least one skin layer has an average thickness of greater than about 500 nanometers (nm). Each of the plurality of polymeric layers has an average thickness of less than about 500 nm. For a substantially collimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees. For the substantially collimated incident light from within the medium and having the at least first visible wavelength in the visible wavelength range, each of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle.

[0031] The light extracting mirror of the present disclosure includes the plurality of alternating partially reflective facets and interlayers instead of glass plates and vapor deposited thin film coatings as used in conventional light extracting mirrors. Therefore, the light extracting mirror of the present disclosure may be lightweight, low-cost, and may have a simpler manufacturing process. Further, the light extracting mirror of the present disclosure may have a comparable or even better optical performance as compared to the conventional light extracting mirrors

[0032] Referring now to figures, FIG. 1 A shows a schematic sectional view of an optical waveguide 200 and a light extracting mirror 100, according to an embodiment of the present disclosure.

[0033] In the illustrated embodiment of FIG. 1 A, the optical waveguide 200 includes an optical core 50 configured to propagate an image light 10 therealong primarily by total internal reflection. Further, as shown in FIG. 1A, the optical waveguide 200 includes the light extracting mirror 100 disposed on the optical core 50.

[0034] In some embodiments, the light extracting mirror 100 is configured to receive the propagating image light 10 and extract, primarily by geometrical reflection, at least portions of the received propagating portions as a plurality of exiting image lights 12 towards a viewer 20.

[0035] In some embodiments, the light extracting mirror 100 is configured to receive the image light 10 from a first end 110 of the light extracting mirror 100 and propagate the image light 10 along a first direction dl toward a second end 112 of the light extracting mirror 100.

[0036] The light extracting mirror 100 includes a plurality of alternating partially reflective facets and interlayers 90, 80.

[0037] In some embodiments, the partially reflective facets 90 are inclined at an inclination angle al of between about 30 degrees and about 60 degrees. In some embodiments, the partially reflective facets 90 are inclined at the inclination angle al of between about 35 degrees and about 55 degrees, or between about 40 degrees and about 50 degrees. In some embodiments, the partially reflective facets 90 are inclined at the inclination angle al of about 45 degrees.

[0038] In the illustrated embodiment of FIG. 1 A, the plurality of partially reflective facets 90 includes first and second partially reflective facets 90a, 90b. As shown in FIG. 1 A, the first partially reflective facet 90a is disposed between the first end 110 and the second partially reflective facet 90b.

[0039] In some embodiments, the plurality of interlayers 80 includes polymethyl methacrylate (PMMA). In some embodiments, the plurality of interlayers 80 includes polycarbonate (PC).

[0040] In some embodiments, the light extracting mirror 100 further includes a coating layer 60. In some embodiments, the coating layer 60 includes at least one polymer with an acid functionality. In some embodiments, the coating layer 60 further includes a high glass transition temperature (Tg) polymer with a glass transition temperature greater than 20° Celsius (°C). Furthermore, in some embodiments, the coating layer 60 includes a crosslinker. In some embodiments, the coating layer 60is applied to the interlayers 80. In some embodiments, the coating layer 60 is applied to the interlayer 80 before stacking of the alternating partially reflective facets and interlayers 90, 80.

[0041] As shown in FIG. 1A, the light extracting mirror 100 has opposing first and second major surfaces 102, 104. In some embodiments, the partially reflective facets 90 are disposed between the first and second major surfaces 102, 104 and are spaced apart and substantially parallel.

[0042] In the illustrated embodiment of FIG. 1 A, the partially reflective facets 90 are equally spaced apart.

[0043] FIG. IB shows a schematic sectional view of the optical waveguide 200 and the light extracting mirror 100, according to another embodiment of the present disclosure.

[0044] The light extracting mirror 100 of FIG. IB is substantially similar to the light extracting mirror 100 of FIG. 1 A, with like elements designated by like reference characters.

[0045] However, in the illustrated embodiment of FIG. IB, the light extracting mirror 100 has a different configuration. Specifically, the light extracting mirror 100 of FIG. IB has a different spacing 85 between pairs of adjacent partially reflective facets 90 in the plurality of partially reflective facets 90. In other words, the spacing 85 between the pairs of adjacent partially reflective facets 90 in the plurality of partially reflective facets 90 is different. Specifically, the spacing 85 between the pairs of adjacent partially reflective facets 90 in the plurality of partially reflective facets 90 decreases from the first end 110 to the second end 112.

[0046] FIG. 2 shows a detailed sectional view of one of the partially reflective facets 90, according to an embodiment of the present disclosure.

[0047] As shown in FIG. 2, each of the plurality of partially reflective facets 90 includes a plurality of polymeric layers 96. Further, each of the plurality of polymeric layers 96 has an average thickness t of less than about 500 nanometers (nm). The term “average thickness t”, as used herein, refers to an average of thicknesses measured at multiple points across a plane of each of the plurality of polymeric layers 96.

[0048] In some embodiments, the plurality of polymeric layers 96 includes a plurality of alternating first and second polymeric layers 92, 94.

[0049] Each of the plurality of partially reflective facets 90 further includes at least one skin layer 98 disposed on the plurality of polymeric layers 96. In some embodiments, the at least one skin layer 98 includes polyethylene terephthalate (PET). In some embodiments, the at least one skin layer 98 may include any suitable material as per desired application attributes.

[0050] The at least one skin layer 98 has an average thickness st of greater than about 500 nm. The term “average thickness st”, as used herein, refers to an average of thicknesses measured at multiple points across a plane of each of the at least one skin layer 98.

[0051] In the illustrated embodiment of FIG. 2, the at least one skin layer 98 includes two skin layers 98 and the plurality of polymeric layers 96 are disposed between the two skin layers 98. The at least one skin layer 98 may protect the plurality of polymeric layers 96 and may also providemechanical stability to the plurality of partially reflective facets 90. In some cases, the at least one skin layer 98 may act as a protective boundary layer (PBL).

[0052] With reference to FIGS. 1A and IB, in some embodiments, the coating layer 60 is disposed between the at least one skin layer 98 and an adjacent interlayer 80 from the plurality of interlayers 80.

[0053] FIG. 2 further illustrates a substantially collimated incident light 70 incident on the partially reflective facet 90 at a first incident angle al of less than about 5 degrees and a substantially collimated incident light 71 incident on the partially reflective facet 90 at a second incident angle a2 of between about 30 degrees and about 60 degrees.

[0054] In some embodiments, the first incident angle al is less than about 4 degrees, less than about 3 degrees, less than about 2 degrees, or less than about 1 degree. In some embodiments, the first incident angle al is about 0 degree.

[0055] In some embodiments, the second incident angle a2 is between about 35 degrees and about 55 degrees, or between about 40 degrees and about 50 degrees.

[0056] For the substantially collimated incident light 70 from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets 90 has an optical reflectance of less than about 15% for the incident light 70 incident at the first incident angle al of less than about 5 degrees. In some embodiments, the medium has the index of refraction of greater than about 1.35, greater than about 1.4, or greater than about 1.45. In some embodiments, the medium has the index of refraction of about 1.5.

[0057] In some embodiments, for the substantially collimated incident light 70 from within the medium and having the at least first visible wavelength in the visible wavelength range, each of the at least majority of the partially reflective facets 90 has the optical reflectance of less than about 12%, less than about 10%, less than about 8%, less than about 6%, less than about 5%, or less than about 1% for the incident light 70 incident at the first incident angle al.

[0058] In some embodiments, for the substantially collimated incident light 70 from within the medium and having the at least first visible wavelength in the visible wavelength range, for the first incident angle al, each of the partially reflective facets 90 reflects less than about 15% of the incident light 70 having a first polarization state and transmits at least about 50% of the incident light 70 having a second polarization state.

[0059] In some embodiments, for the substantially collimated incident light 70 from within the medium and having the at least first visible wavelength in the visible wavelength range, for the first incident angle al, each of the partially reflective facets 90 reflects less than about 12%, less than about 10%, less than about 8%, less than about 6%, or less than about 5% of the incident light 70 having the first polarization state and transmits at least about 55%, at least about 60%, at least about65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, or at least about 90% of the incident light 70 having the second polarization state.

[0060] In some embodiments, the first polarization state is an s-polarization state and the second polarization state is a p-polarization state. In some other embodiments, the first polarization state is the p-polarization state and the second polarization state is the s-polarization state.

[0061] In some embodiments, for the substantially collimated incident light 71 from within the medium and having the at least first visible wavelength in the visible wavelength range, each of the at least majority of the partially reflective facets 90 has an optical reflectance of at least 10% for the incident light 71 incident at the second incident angle a2 of between about 30 degrees and about 60 degrees.

[0062] Further, for the substantially collimated incident light 71 from within the medium and having the at least first visible wavelength in the visible wavelength range, each of the at least majority of the partially reflective facets 90 has the optical reflectance of at least 12%, 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%, at least 85%, or at least 90% for the incident light 71 incident at the second incident angle a2.

[0063] In some embodiments, for the substantially collimated incident light 71 from within the medium and having the at least first visible wavelength in the visible wavelength range, for the second incident angle a2, each of the partially reflective facets 90 reflects at least about 10% of the incident light 71 having the first polarization state and transmits at least about 50% of the incident light 71 having the second polarization state.

[0064] In some embodiments, for the substantially collimated incident light 71 from within the medium and having the at least first visible wavelength in the visible wavelength range, for the second incident angle a2, each of the partially reflective facets 90 reflects at least 12%, 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%, at least 85%, or at least 90% of the incident light 71 having the first polarization state and transmits at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% of the incident light 71 having the second polarization state.

[0065] Referring to FIGS. 1 A and 2, in some embodiments, for the substantially collimated incident light 71 from within the medium and having the at least first visible wavelength, the at least first and second partially reflective facets 90a, 90b in the plurality of partially reflective facets 90 have different optical reflectances for the incident light 71 incident at the second incident angle a2.Further, in some embodiments, the different optical reflectances are different by at least 2%. In some embodiments, the different optical reflectances are different by at least 4%, at least 6%, at least 8%, at least 10%, at least 12%, at least 14%, at least 16%, at least 18%, or at least 20%.

[0066] In some embodiments, the optical reflectance of the first partially reflective facet 90a is lower than the optical reflectance of the second partially reflective facet 90b for the second incident angle a2.

[0067] For the substantially collimated incident light 70 from within the medium and having the at least first visible wavelength in the visible wavelength range, each of at least a majority of the interlayers 80 transmits greater than about 80% of the incident light 70 incident at the first incident angle al. In some embodiments, for the substantially collimated incident light 70 from within the medium and having the at least first visible wavelength in the visible wavelength range, each of the at least majority of the interlayers 80 transmits greater than about 85%, greater than about 90%, greater than about 95%, or greater than about 99% of the incident light 70 incident at the first incident angle al. Therefore, the majority of the interlayers 80 are substantially transparent for the first incident angle al.

[0068] In some embodiments, the at least first visible wavelength includes at least one blue wavelength in a blue wavelength range extending from about 420 nm to about 470 nm. In some embodiments, the at least first visible wavelength further includes at least one green wavelength in a green wavelength range extending from about 500 nm to about 560 nm. Further, in some embodiments, the at least first visible wavelength includes at least one red wavelength in a red wavelength range extending from about 620 nm to about 680 nm.

[0069] FIG. 3 shows a flowchart of a method 300 of manufacturing the light extracting mirror 100 shown in FIGS. 1 A and IB, according to an embodiment of the present disclosure. FIG. 4 shows schematic steps of the method 300, according to an embodiment of the present disclosure.

[0070] Referring to FIGS. 3 and 4, at step 302, the method 300 includes providing a plurality of partially reflective facets (e.g., the plurality of partially reflective facets 90). Each of the plurality of partially reflective facets includes a plurality of polymeric layers (e.g., the plurality of polymeric layers 96 shown in FIG. 2) and at least one skin layer (e.g., the at least one skin layer 98 shown in FIG. 2) disposed on the plurality of polymeric layers. Each of the plurality of polymeric layers has an average thickness of less than about 500 nm. The at least one skin layer has an average thickness of greater than about 500 nm.

[0071] At step 304, the method 300 includes providing a plurality of interlayers (e.g., the plurality of interlayers 80).

[0072] At step 306, the method 300 includes stacking the plurality of partially reflective facets and the interlayers in an alternating manner. Specifically, the stacking of the plurality of partially reflective facets and the interlayers in the alternating manner forms a stack 40.

[0073] In some embodiments, the method 300 further includes providing a coating layer (e.g., the coating layer 60) on the at least one skin layer prior to stacking the plurality of partially reflective facets and the interlayers in the alternating manner. In some embodiments, the coating layer includesat least one polymer with an acid functionality, a high Tg polymer with a glass transition temperature greater than 20° C, and a crosslinker.

[0074] At step 308, the method 300 includes applying heat H and pressure P on the stack 40 of the plurality of alternating partially reflective facets and interlayers to obtain a slab 30. In some embodiments, the method 300 further includes removing air from the stack 40 of the plurality of alternating partially reflective facets and interlayers prior to applying the heat H and the pressure P on the stack 40. In some embodiments, applying the heat H and the pressure P includes applying the heat H of from about 110° C to about 150° C and the pressure P of from about 5 psi to about 50 psi. In some embodiments, applying the heat H and the pressure P includes applying the heat H from about 130° C to about 140° C and the pressure P of about 25 psi.

[0075] At step 310, the method 300 includes cutting a portion of the slab 30 at a cutting angle cl to obtain a mirror portion 35. In some cases, the cutting angle cl may be at about 60 degrees. In some cases, the cutting angle cl may be between about 30 degrees and about 60 degrees. In some cases, the cutting angle cl may be between about 35 degrees and about 55 degrees, or between about 40 degrees and about 50 degrees. In some cases, the mirror portion 35 may be from about 1 mm to about 5 mm thick.

[0076] At step 312, the method 300 includes polishing at least one of opposing first and second major surfaces of the mirror portion 35 to obtain the light extracting mirror 100.

[0077] FIG. 5 shows an exemplary bar graph 500 depicting Sa and Sq roughness for a conventional light extracting mirror and the light extracting mirror 100.

[0078] The Sa roughness is an arithmetical mean height of an outer surface. The Sq roughness is a squared mean height of the outer surface. The Sq roughness may be equivalent to a standard deviation of height distribution of the outer surface.

[0079] The bar graph 500 includes a bar 502-1 depicting the Sa roughness of a bottom surface of the conventional light extracting mirror at a first location away from the partially reflective facets 90 (shown in FIGS. 1A, IB).

[0080] The bar graph 500 includes a bar 502-2 depicting the Sq roughness of the bottom surface of the conventional light extracting mirror at the first location.

[0081] The bar graph 500 includes a bar 504-1 depicting the Sa roughness of the bottom surface of the conventional light extracting mirror at a second location away from the partially reflective facets 90.

[0082] The bar graph 500 includes a bar 504-2 depicting the Sq roughness of the bottom surface of the conventional light extracting mirror at the second location.

[0083] The bar graph 500 includes a bar 506-1 depicting the Sa roughness of a top surface of the conventional light extracting mirror at the first location.

[0084] The bar graph 500 includes a bar 506-2 depicting the Sq roughness of the top surface of the conventional light extracting mirror at the first location.

[0085] The bar graph 500 includes a bar 508-1 depicting the Sa roughness of the top surface of the conventional light extracting mirror at the second location.

[0086] The bar graph 500 includes a bar 508-2 depicting the Sq roughness of the top surface of the conventional light extracting mirror at the second location.

[0087] The bar graph 500 includes a bar 510-1 depicting the Sa roughness of a bottom surface of the light extracting mirror 100 at the first location.

[0088] The bar graph 500 includes a bar 510-2 depicting the Sq roughness of the bottom surface of the light extracting mirror 100 at the first location.

[0089] The bar graph 500 includes a bar 512-1 depicting the Sa roughness of the bottom surface of the light extracting mirror 100 at the second location.

[0090] The bar graph 500 includes a bar 512-2 depicting the Sq roughness of the bottom surface of the light extracting mirror 100 at the second location.

[0091] The bar graph 500 includes a bar 514-1 depicting the Sa roughness of a top surface of the light extracting mirror 100 at the first location.

[0092] The bar graph 500 includes a bar 514-2 depicting the Sq roughness of the top surface of the light extracting mirror 100 at the first location.

[0093] The bar graph 500 includes a bar 516-1 depicting the Sa roughness of the top surface of the light extracting mirror 100 at the second location.

[0094] The bar graph 500 includes a bar 516-2 depicting the Sq roughness of the top surface of the light extracting mirror 100 at the second location.

[0095] As is apparent from the bars 510-1, 512-1, 514-1, 516-1, in some embodiments, the Sa roughness of at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 is less than about 0.02 microns.

[0096] As is apparent from the bars 510-2, 512-2, 514-2, 516-2, in some embodiments, the Sq roughness of at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 is less than about 0.04 microns. In some embodiments, the Sq roughness of at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 is less than about 0.035 microns, less than about 0.03 microns, or less than about 0.025 microns.

[0097] FIG. 6 shows an exemplary bar graph 600 depicting Svk roughness for the conventional light extracting mirror and the light extracting mirror 100. The Svk roughness is a reduced valley depth of the outer surface.

[0098] The bar graph 600 includes a bar 602 depicting the Svk roughness of the bottom surface of the conventional light extracting mirror at the first location.

[0099] The bar graph 600 includes a bar 604 depicting the Svk roughness of the bottom surface of the conventional light extracting mirror at the second location.

[0100] The bar graph 600 includes a bar 606 depicting the Svk roughness of the top surface of the conventional light extracting mirror at the first location.

[0101] The bar graph 600 includes a bar 608 depicting the Svk roughness of the top surface of the conventional light extracting mirror at the second location.

[0102] The bar graph 600 includes a bar 610 depicting the Svk roughness of the bottom surface of the light extracting mirror 100 at the first location.

[0103] The bar graph 600 includes a bar 612 depicting the Svk roughness of the bottom surface of the light extracting mirror 100 at the second location.

[0104] The bar graph 600 includes a bar 614 depicting the Svk roughness of the top surface of the light extracting mirror 100 at the first location.

[0105] The bar graph 600 includes a bar 616 depicting the Svk roughness of the top surface of the light extracting mirror 100 at the second location.

[0106] As is apparent from the bars 610, 612, 614, 616, in some embodiments, the Svk roughness of at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 is less than about 0.06 microns. In some embodiments, the Svk roughness of at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 is less than about 0.055 microns, less than about 0.05 microns, less than about 0.045 microns, or less than about 0.04 microns.

[0107] Referring to FIGS. 5 and 6, in some embodiments, the at least one of the Sa roughness, the Sq roughness, and the Svk roughness of at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 is less than about 0.06 microns. As is apparent from the bar graphs 500, 600, in some embodiments, each of the Sa roughness, the Sq roughness, and the Svk roughness of the at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 is less than about 0.06 microns.

[0108] FIG. 7 shows an exemplary bar graph 700 depicting X and Y slope sigmas for the conventional light extracting mirror and the light extracting mirror 100.

[0109] X slope sigma is a standard deviation of x-slope OX values and Y slope sigma is a standard deviation of y- slope OY values.

[0110] The x-slope and x-slope maps are calculated by expressing the slopes as an angle in degrees using the arc tangent function.

[0111] The x-slope OX values and the y-slope OX values are obtained using the equations provided below:

[0114] Where, r is an integer that determines the interval size that the slope is calculated.

[0115] The equations give the average x and y slopes over an interval size 2r Ax and 2rAy, respectively.

[0116] The bar graph 700 includes a bar 702-1 depicting the X slope sigma of the bottom surface of the conventional light extracting mirror at the first location.

[0117] The bar graph 700 includes a bar 702-2 depicting the Y slope sigma of the bottom surface of the conventional light extracting mirror at the first location.

[0118] The bar graph 700 includes a bar 704-1 depicting the X slope sigma of the bottom surface of the conventional light extracting mirror at the second location.

[0119] The bar graph 700 includes a bar 704-2 depicting the Y slope sigma of the bottom surface of the conventional light extracting mirror at the second location.

[0120] The bar graph 700 includes a bar 706-1 depicting the X slope sigma of the top surface of the conventional light extracting mirror at the first location.

[0121] The bar graph 700 includes a bar 706-2 depicting the Y slope sigma of the top surface of the conventional light extracting mirror at the first location.

[0122] The bar graph 700 includes a bar 708-1 depicting the X slope sigma of the top surface of the conventional light extracting mirror at the second location.

[0123] The bar graph 700 includes a bar 708-2 depicting the Y slope sigma of the top surface of the conventional light extracting mirror at the second location.

[0124] The bar graph 700 includes a bar 710-1 depicting the X slope sigma of the bottom surface of the light extracting mirror 100 at the first location.

[0125] The bar graph 700 includes a bar 710-2 depicting the Y slope sigma of the bottom surface of the light extracting mirror 100 at the first location.

[0126] The bar graph 700 includes a bar 712-1 depicting the X slope sigma of the bottom surface of the light extracting mirror 100 at the second location.

[0127] The bar graph 700 includes a bar 712-2 depicting the Y slope sigma of the bottom surface of the light extracting mirror 100 at the second location.

[0128] The bar graph 700 includes a bar 714-1 depicting the X slope sigma of the top surface of the light extracting mirror 100 at the first location.

[0129] The bar graph 700 includes a bar 714-2 depicting the Y slope sigma of the top surface of the light extracting mirror 100 at the first location.

[0130] The bar graph 700 includes a bar 716-1 depicting the X slope sigma of the top surface of the light extracting mirror 100 at the second location.

[0131] The bar graph 700 includes a bar 716-2 depicting the Y slope sigma of the top surface of the light extracting mirror 100 at the second location.

[0132] As is apparent from the bars 710-1, 712-1, 714-1, 716-1, 710-2, 712-2, 714-2, 716-2, in some embodiments, a standard deviation of slopes on the at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 for an interval of ±10 pixels is less than about 0.8. The interval of +10 pixel corresponds to +1.75 times a wavelength of light (e.g., 550 nm)rounded to a nearest pixel. 1.75 times the wavelength is equal to about 963 nm which rounds to about ten 93.75 nm pixels.

[0133] In some embodiments, the standard deviation of slopes on the at least one of the opposing first and second major surfaces 102, 104 of the light extracting mirror 100 for the interval of ±10 pixels is less than about 0.75, less than about 0.7, less than about 0.65, less than about 0.6, less than about 0.55, less than about 0.5, less than about 0.45, or less than about 0.4.

[0134] FIG. 8 shows an exemplary graph 800 depicting adhesion properties for exemplary samples 802, 804 of the light extracting mirror 100 and a comparative sample 806. Specifically, the exemplary graph 800 depicts the adhesion properties between the partially reflective facets (e.g., the plurality of partially reflective facets 90 shown in FIGS. 1A, IB) and the interlayers (e.g., the plurality of interlayers 80 shown in FIGS. 1A, IB) for the exemplary samples 802, 804 of the light extracting mirror 100 and the comparative sample 806.

[0135] The exemplary sample 802 includes cellulose acetate butyrate (CAB) and windshield combiner film (WCF) with NEA-H (e.g., the coating layer 60).

[0136] The WCF is available from THE 3M COMPANY and is made by extruding and uniaxially orienting 275 alternating polymer layers plus two outermost skin layers as generally described in U.S. Patent 6,827,886 (Neavin et al.). The alternating polymer layers were oriented PET as higher index layers and crystalline PETg as lower index layers. The NEA-H is an acrylate heat activated optically clear adhesive (OCA) with high Tg polymer.

[0137] The exemplary sample 804 includes polymethyl methacrylate (PMMA) and the WCF with the NEA-H.

[0138] The comparative sample 806 includes PMMA and HPWF 150°C / 10hr / 25psi. The comparative sample 806 does not include the NEA-H.

[0139] The HPWF is available from THE 3M COMPANY includes alternating polymer layers of PET as higher index layers and co-PMMA as lower index layers.

[0140] With reference to FIGS. 1A-1B and 8, in some embodiments, the adhesion between the partially reflective facet 90 and the adjacent interlayer 80 from the interlayers 80 is at least 20 Newtons. In some embodiments, the adhesion between the partially reflective facet 90 and the adjacent interlayer 80 from the interlayers 80 is at least 30 Newtons, at least 40 Newtons, at least 50 Newtons, at least 60 Newtons, at least 70 Newtons, at least 80 Newtons, at least 90 Newtons, at least 100 Newtons, at least 150 Newtons, or at least 200 Newtons.

[0141] Table 1 provided below includes peak load values from the adhesion test conducted on different samples.Table 1

[0142] Referring to FIGS. 1A-1B to 8, the light extracting mirror 100 includes the plurality of alternating partially reflective facets and interlayers 90, 80 instead of glass plates and vapor deposited thin film coatings as used in typical light extracting mirrors. Therefore, the light extracting mirror 100 may be lightweight, low-cost, and may have a simpler manufacturing process. Further, the light extracting mirror 100 may have a comparable or even better optical performance as compared to the typical light extracting mirrors.

[0143] Furthermore, the light extracting mirror 100 may have a good interlayer adhesion, i.e., the adhesion between the partially reflective facet 90 and the adjacent interlayer 80 from the interlayers 80. Moreover, the light extracting mirror 100 may have a smooth surface finish after polishing.

[0144] 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 the foregoing 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.

[0145] 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 anyadaptations 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. A light extracting mirror comprising:a plurality of alternating partially reflective facets and interlayers, each of the plurality of partially reflective facets comprises a plurality of polymeric layers and at least one skin layer disposed on the plurality of polymeric layers and having an average thickness of greater than about 500 nanometers (nm), each of the plurality of polymeric layers having an average thickness of less than about 500 nm,such that for a substantially collimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees, andeach of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle.

2. The light extracting mirror of claim 1, further comprising a coating layer disposed between the at least one skin layer and an adjacent interlayer from the plurality of interlayers.

3. The light extracting mirror of claim 2, wherein the coating layer comprises:at least one polymer with an acid functionality;a high Tg polymer with a glass transition temperature greater than 20° C; anda crosslinker.

4. The light extracting mirror of claim 1, wherein for the substantially collimated incident light from within the medium and having the at least first visible wavelength in the visible wavelength range:for the first incident angle, each of the partially reflective facets reflects less than about 15% of the incident light having a first polarization state and transmits at least about 50% of the incident light having a second polarization state; andfor the second incident angle, each of the partially reflective facets reflects at least about 10% of the incident light having the first polarization state and transmits at least about 50% of the incident light having the second polarization state.

5. The light extracting mirror of claim 1, wherein the light extracting mirror has opposing first and second major surfaces, the partially reflective facets disposed between the first and second major surfaces and are spaced apart and substantially parallel.

6. The light extracting mirror of claim 1, wherein the at least 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.

7. An optical waveguide comprising:an optical core configured to propagate an image light therealong primarily by total internal reflection; andthe light extracting mirror of claim 1 disposed on the optical core, the light extracting mirror configured to receive the propagating image lights and extract, primarily by geometrical reflection, at least portions of the received propagating portions as a plurality of exiting image lights towards a viewer.

8. A light extracting mirror comprising:a plurality of alternating partially reflective facets and interlayers, each of the plurality of partially reflective facets comprises a plurality of polymeric layers and at least one skin layer disposed on the plurality of polymeric layers, the at least one skin layer comprising polyethylene terephthalate (PET) and having an average thickness of greater than about 500 nanometers (nm), each of the plurality of polymeric layers having an average thickness of less than about 500 nm, and the plurality of interlayers comprising polymethyl methacrylate (PMMA); anda coating layer disposed between the at least one skin layer and an adjacent interlayer from the plurality of interlayers,such that for a substantially collimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees, andeach of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle.

9. The light extracting mirror of claim 8, wherein the coating layer comprises:at least one polymer with an acid functionality;a high Tg polymer with a glass transition temperature greater than 20° C; anda crosslinker.

10. The light extracting mirror of claim 8, wherein an adhesion between the partially reflective facet and an adjacent interlayer from the interlayers is at least 20 Newtons.

11. A light extracting mirror comprising:a plurality of alternating partially reflective facets and interlayers, each of the plurality of partially reflective facets comprises a plurality of polymeric layers and at least one skin layer disposed on the plurality of polymeric layers and having an average thickness of greater than about 500 nanometers (nm), each of the polymeric layers having an average thickness of less than about 500 nm;such that for a substantially collimated incident light from within a medium having an index of refraction of greater than about 1.3 and 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 partially reflective facets has an optical reflectance of less than about 15% for the incident light incident at a first incident angle of less than about 5 degrees and an optical reflectance of at least 10% for the incident light incident at a second incident angle of between about 30 degrees and about 60 degrees, andeach of at least a majority of the interlayers transmits greater than about 80% of the incident light incident at the first incident angle, andwherein at least one of an Sa roughness, an Sq roughness, and an Svk roughness of at least one of opposing first and second major surfaces of the light extracting mirror is less than about 0.06 microns.

12. The light extracting mirror of claim 11, wherein each of the Sa roughness, the Sq roughness, and the Svk roughness of the at least one of the opposing first and second major surfaces of the light extracting mirror is less than about 0.06 microns.

13. The light extracting mirror of claim 11, wherein an adhesion between the partially reflective facet and an adjacent interlayer from the interlayers is at least 20 Newtons.

14. The light extracting mirror of claim 11, further comprising a coating layer disposed between the at least one skin layer and an adjacent interlayer from the plurality of interlayers.

15. The light extracting mirror of claim 14, wherein the coating layer comprises:at least one polymer with an acid functionality;a high Tg polymer with a glass transition temperature greater than 20° C; anda crosslinker.

Images