WO2016075540A1

WO2016075540A1 - Methods and apparatus for super anaglyph stereoscopic vision

Info

Publication number: WO2016075540A1
Application number: PCT/IB2015/002274
Authority: WO
Inventors: Jean-Louis De Bougrenet; Philippe Grosso; Andrej Tomeljak
Original assignee: Neoopti Xpand Limited; Eyes Triple Shut S.A.
Priority date: 2014-11-12
Filing date: 2015-11-12
Publication date: 2016-05-19

Abstract

Polarization-insensitive, trichromatic resonant waveguide (RWG) optical filters can be used for super anaglyph stereoscopic vision. An RWG filter can be centered on three wavelengths (e.g., red, green, and blue wavelengths) and formed of a grating disposed on a waveguide that supports at least one propagation mode. The grating can be formed in or on the surface of the first waveguide with one- or two-dimensional periodicity. For example, the grating may have 2D tiling that is triangular, with each leg of the triangle having a length to a different wavelength. The RWG filter may be stacked on a second RWG filter with another grating formed in or on the surface of the second waveguide, with the second grating have a periodicity identical to that of the first grating, but rotated about the optical axis to filter both transverse electric (TE) and transverse magnetic (TM) polarizations.

Description

METHODS AND APPARATUS FOR SUPER ANAGLYPH STEREOSCOPIC VISION

CROSS-REFERENCE

[0001] This application claims the benefit of U.S. Provisional Application No.

62/078,879, filed November 12, 2014 [Attorney Docket No. 6XLI-001/00US], the full disclosures of which are incorporated herein by reference.

BACKGROUND

[0002] Stereoscopy is a technique for creating or enhancing the illusion of depth in a two- dimensional (2D) image by means of stereopsis for binocular vision. Most stereoscopic techniques involve projecting separate, offset 2D left and right images of a scene to the viewer's left and right eyes, respectively. The viewer's brain combines these offset 2D images to give the perception of a three-dimensional (3D) image.

[0003] In anaglyph stereoscopy, the left and right images are encoded by color. When viewed through the color-coded "anaglyph glasses," each image reaches the eye that it's intended for, leading the viewer to perceive a three-dimensional scene or composition. In some of the first 3D movies, for example, the viewer wore low-cost paper frames or plastic- framed glasses with red and blue filters. The current norm is red and cyan, with red being used for the left channel, for full-color 3D viewing. 3D viewing can also be used for video games, viewing astronomical and other data, geological illustrations, museum objects, and medical imaging.

[0004] More recent anaglyph stereoscopic viewing systems produce full-color images by projecting images with specific wavelengths of red, green, and blue for the right eye, and different wavelengths of red, green, and blue for the left eye. The human eye is largely insensitive to such fine spectral differences so this technique is able to generate full-color 3D images with only slight color differences between the two eyes. Eyeglasses which filter out the very specific wavelengths allow the wearer to see a full color 3D image. This technique is also known as spectral comb filtering, wavelength multiplex visualization, or "super- anaglyph" viewing because it uses spectral multiplexing. It does not require an expensive silver screen like those used in polarized systems such as RealD. To date, however, super- anaglyph systems have used glasses with thin-film interference filters, which are more expensive than the polarizers in the glass for polarized systems.

SUMMARY

[0005] Embodiments of the present invention include an optical filter that is insensitive to polarization and rejects (e.g., reflects and/or attenuates) or transmits light for six wavelength bands (Rl, Gl, Bl and R2, G2, B2) for super anaglyph stereoscopic vision. This optical filter may include: a first waveguide and a second waveguide, each supporting at least one respective propagation mode; a first grating formed in or on the surface of the first waveguide, the first grating being periodic at least along a first axis θ_χ and defining a first orthonormal base θ_χγζ; and a second grating formed in or on the surface of the second waveguide, the second grating being periodic at least along a second axis 9_xy- and defining a second orthonormal base Q_xy_z. The first and the second gratings may be arranged above each other such that the first axis θ_χ and the second axis θ_χ· form an angle of π/2 radians.

[0006] In at least one example of this optical filter, the first and second gratings are identical. Each comprises a series of identical patterns or grooves of three periods a, b, and c whose values depend on the desired reflected/transmitted wavelength bands and on the choice of materials used to construct the optical filter. For instance, each grating may be tiled in 2D by unitary triangles whose interior angles are given by the following relationships: a = arcos[(£² + c² - a²)/2bc]; β = arcos[(a² + c² - b²)/2ac]; and γ = arcos[(a² + b² - c²)/2ab]. The gratings may be formed of a series of patterns either in the form of an air-pillar matrix (columnar holes) or in the form of (identical) grooves. The depth and duty cycle of the structure are determined by the reflected/attenuated wavelength bands and the choice of materials. The air-pillars may have elliptical cross sections and may be the same for all gratings.

[0007] The first optical filter may be etched in Ta₂0₅ on Si₃N₄ with grooves of periods a = 497 nm, b = 367 nm, and c = 283 nm; a duty cycle of 35% (corresponding to the amount of missing matter); the modulation depth D = 70 nm and the first triangle angles: al = βΐ = γ\ = 60°. The second optical filter may have respectively grooves of period a = 521 nm, b = 391 nm, c = 303 nm, the modulation depth D = 70 nm and the second triangle angles: a2 = β2 = γ2 = 60°.

[0008] Alternatively, the optical filters may include a Ta₂0₅ on Si₃N₄ grating defining elliptical air pillars and disposed on a Si0₂ waveguide. The first optical filter may have grooves of periods a = 446 nm, b = 333 nm, and c = 262 nm; a duty cycle of 75%; and a modulation depth D = 40 nm. The second optical filter may the gratings have respectively grooves of period a = 460 nm, b = 358 nm, and c = 282 nm, and a modulation depth D = 40 nm. The second filter may have gratings with grooves of period a = 514 nm, b = 385 nm, and c = 298 and a modulation depth D = 55 nm.

[0009] The optical filter according to claim 1 , in which the first waveguide and the second waveguide are identical and are each constituted by a plurality of layers made of material transparent to the wavelength of interest. The optical filter according to claim 5, in which the first waveguide and the second waveguide are each constituted by two or more layers of dielectric or other materials of different refractive indexes. The optical filter may comprise of a glass substrate arranged between the first waveguide and the second waveguide and/or between the first grating and the second grating.

[0010] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements).

[0012] FIG. 1 illustrates a full-color anaglyph stereoscopic viewing system with different resonant waveguide (RWG) filters to encode left and right images.

[0013] FIG. 2A is a plot of a reflection spectrum of a band-reject RWG filter suitable for use in the eyewear of FIG. 1.

[0014] FIG. 2B is a plot of a transmission spectrum of a bandpass RWG filter suitable for use in the eyewear of FIG. 1.

[0015] FIG. 3A illustrates an air pillar matrix-type, polarization-insensitive, single- wavelength band RWG filter suitable for use in the eyewear of FIG. 1.

[0016] FIG. 3B illustrates a 2D tiling triangle for the air pillar matrix-type trichromatic RWG filter of FIG. 3 A.

[0017] FIG. 3C shows a groove-type, polarization-sensitive trichromatic RWG filter with a duty cycle of about 35% (i.e., 35% of the Ta₂0₅ layer has been etched away).

[0018] FIG. 3D shows a side view of the groove -type, polarization-sensitive trichromatic RWG filter shown in FIG. 3C.

[0019] FIG. 3E shows a top view of the groove-type, polarization-sensitive trichromatic RWG filter shown in FIGS. 3C and 3D. [0020] FIG. 4A illustrates stack of an air pillar matrix-type, polarization-insensitive trichromatic air-pillar RWG filters suitable for use in the eyewear of FIG. 1.

[0021] FIG. 4B illustrates another polarization-insensitive trichromatic RWG rectangular grating filters suitable for use in the eyewear of FIG. 1.

[0022] FIG. 4C is a side view of a groove-type trichromatic polarization-insensitive RWG filter.

[0023] FIG. 5 illustrates a lift-off process for making a RWG filter that comprises a Ta₂0₅ grating on an Si0₂ structure.

[0024] FIG. 6 is a plot of the refractive index (left axis) and absorption coefficient (right axis) versus wavelength for S1₃N₄.

[0025] FIG. 7 is a plot of a numerical simulation of the zero-order diffraction efficiency of a Ta203 grating patterned with rectangular grooves having a depth of 50 nm, periods of 261 nm, 323 nm, and 415 nm, and a duty cycle (DC) of 50% on a Si₃N₄ waveguide layer.

DETAILED DESCRIPTION

[0026] Embodiments of the present invention include trichromatic resonant waveguide (RWG) filters, which are also referred to as resonance filters and Fano resonance filters, for stereovision using "6-Primary" (6P) laser projectors. The left eye image is typically illuminated by three laser source clusters, one for each primary color. The right eye image is also typically illuminated by three laser source clusters, one for each primary color, where the central wavelength of each primary color in the first and second laser clusters is separated slightly, e.g., by about 15 nm to about 25 nm. This makes it possible to resolve the left and right image separately by using RWG filters whose depth and duty cycle are determined by the primary color wavelength bands (defined by the central wavelength and bandwidth). The filter full-width half-maxima (FWHM) can be chosen based on the desired RWG filter extinction ratio and may be better than 30 dB.

[0027] Unlike in conventional full-color anaglyph stereoscopic vision systems, where filters are either spatially multiplexed using adjacent gratings, with a resulting penalty in terms of efficiency, or stacked with a resulting penalty in terms of manufacturing cost, the RWG filters can be implemented as polychromatic multiplexed filters based on a non- orthogonal 2D tiling as explained in greater detail below. This provides several advantages, including being able to use just one filter for each set of red, green, and blue (RGB) primary colors. RWG filters offer other advantages as well, including simple and inexpensive manufacturing, robustness, and less crosstalk.

[0028] However, since the source of light may be non-polarized, the RWG filters should also be polarization insensitive. As explained in greater detail below, the 2D tiling of the planar grating structure can be used to implement a polarization-sensitive trichromatic filter or a polarization-insensitive monochromatic filter. In order to achieve a polarization insensitive RGB filter structure, the filters may be stacked as follows: (1) one polarization-insensitive filter for each RGB wavelength (three filters total), or (2) two trichromatic filters for each polarization state. In the second case, the 2D triangular tiling of the grating (discussed below) is used to implement the three filters. Polarisation independence is obtained by stacking two orthogonal trichromatic filters, one for the transverse electric (TE) polarization state and the other for the transverse magnetic (TM) polarization state. Therefore the final filter cluster is polarisation insensitive.

[0029] Anaglyph Stereoscopic Vision Using RWG Filters

[0030] FIG. 1 shows an anaglyph stereoscopic vision system 100 that uses RWG filters 132a and 132b to resolve spectrally encoded left and right images to create the perception of full-color 3D images for a viewer 100. The system 100 includes two laser-based projectors: a first projector 110a that includes a first red laser (or a laser cluster) 112a, a first green laser (or a laser cluster) 114a, a first blue laser (or a laser cluster) 116a, and a first spatial light modulator (SLM) 118a; and a second projector 110b that includes a second red laser (or a laser cluster) 112b, a second green laser (or a laser cluster) 114b, a second blue laser (or a laser cluster) 116b, and a second spatial light modulator (SLM) 118b. The first and second projectors 110 may also include additional optical and optomechanical components, including but not limited to lens, dichroic filters and beam combiners, mounts, etc.

[0031] In other cases, the system 100 may include a single projector with a stack of six laser clusters (rather than six lasers) that show the left and right images time sequentially. The laser wavelengths within each cluster are similar, but not identical. The use of laser clusters of different wavelengths reduces the speckle observed by the viewer. If desired, the bandwidths of the respective passbands of the RWG filters 132 may be selected to pass all of the wavelengths in the corresponding laser cluster. For example, if a first red laser cluster includes lasers that emit light over a span of about 5 nm, then the red passband of the first RWG filter 132a may be at least 5 nm wide in order to transmit the light emitted by the lasers in the first red laser cluster.

[0032] The system 100 also includes a screen 120 and eyewear 130, which includes a frame 134 that holds a first resonant waveguide (RWG) filter 132a in front of the viewer's left eye and a second RWG filter 132b in front of the viewer's right eye. Depending on the embodiment, the RWG filters 132a and 132b may be band-pass or band-reject filters with transmission spectra like those plotted in FIGS. 2A and 2B, respectively. (Each plot shows two spectra: a first spectrum plotted with a solid line for the first RWG filter 132a and a second spectrum plotted with a dashed line for the second RWG 132b.) Or one filter can be a band-pass filter, and the other filter can be a band-reject filter. In any case, the first RWG 132a transmits light at wavelengths Rl, Gl, and Bl and rejects (e.g., reflects or attenuates) light at wavelengths R2, G2, and B2, and the second RWG 132b transmits light at

wavelengths R2, G2, and B2 and rejects (e.g., reflects or attenuates) light at wavelengths Rl, Gl, and Bl .

[0033] In operation, the laser light source in the first projector 110a generates light at wavelengths Rl, Gl, and Bl in the red, green, and blue portions of the visible electromagnetic spectrum. The first SLM 118a spatially modulates the emitted light to produce a first image 1 la that is projected onto the screen 120. Similarly, the lasers in the second projector 110b generate light at wavelengths R2, G2, and B2 in the red, green, and blue portions of the visible electromagnetic spectrum. The wavelengths R2, G2, and B2 are slightly detuned from the wavelengths Rl, Gl, and Bl, e.g., by about 10-30 nm each. And the second SLM 118b spatially modulates the emitted light to produce a second image l ib that is also projected onto the screen 120. The second image 1 lb is an offset view of the same scene shown in the first image 11a.

[0034] The first RWG filter 132a reflects and/or attenuates light at wavelengths R2, G2, and B2 and transmits light at wavelengths Rl, Gl, and Bl, so the left eye detects the first image 11a but not the second image 1 lb. Similarly, the second RWG filter 132a reflects and/or attenuates light at wavelengths Rl, Gl, and Bl and transmits light at wavelengths R2, G2, and B2, so the right eye detects the second image 1 lb but not the first image 11a. The viewer's brain synthesizes the first image 11a with the second image l ib such that the viewer 1 perceives a 3D image of the scene.

[0035] Resonant Waveguide (RWG) Filters

[0036] Each RWG filter 132 shown in FIG. 1 can be implemented as a structure comprised of a sub-wavelength grating etched onto a multi-layer waveguide structure. The grating couples incident light at certain wavelengths and/or polarizations into one or more optical modes supported by the waveguide structure via evanescent diffraction. The optical modes can be characterized by their electromagnetic fields and their dispersion relations (between the wavelength of the mode and the direction of propagation of the incident wave). The grating enables uncoupling from the optical mode to the free space in a direction corresponding to the specular reflection on the surface.

[0037] An RWG filter can be designed to operate in reflection or transmission.

Depending on its design, it can be highly selective in wavelength as well. For example, an RWG-based transmission filter may have a very narrow passband (e.g., a few nanometers) and a high extinction ratio (e.g., >30 dB). A RWG filter's optical properties can be modified by adjusting several parameters of the structure, including but not limited to: the refractive indices of the materials, the thicknesses of layers, the number of layers, the number of grating(s), the periodicities (in ID and 2D) of the gratings, the orientation(s) of the grating vector(s), the period(s) of the grating(s), the modulation depth(s) (e.g., hole depth) of the grating(s), the grating duty cycle (DC), etc. as described in greater detail below.

[0038] An RWG filter can be polarization sensitive; i.e., it may diffract incident light in only certain polarization states. Polarization-sensitive RWG filters can be stacked or otherwise combined to form polarization-insensitive RWG filter structures that can diffract incident light regardless of the polarization state. For example, polarization insensitivity can be achieved by simultaneous excitation by the incident s ("senkrecht," or perpendicular) and p (parallel) waves via two different diffraction orders of the grating or via two orthogonal modes degenerated for a single wavelength. The two orthogonal modes are characterized by fields that are symmetric/asymmetric relative to the incidence plane, which can be a plane of symmetry of the structure.

[0039] Degeneration occurs when combining the modes is cancelled, e.g., either (1) by selecting the pattern of the grating such that there is zero coupling between the diffraction orders of the grating for exciting each mode, while maintaining non-zero coupling between the incident wave and each mode (this condition is easily practicable with a grating that is periodic in a single direction, but may involve more complex patterns for a grating that is periodic in two directions); or (2) by selecting the angle of polar incidence (the angle of incidence azimuth per se is fixed such that the plane of incidence is a plane of symmetry of the structure) such that the angle between the directions of propagation of the two modes is close to π/2 radians. This second condition can be satisfied by a 2D grating with wave vectors that are orthogonal or form an angle of π/3 radians.

[0040] Polarization-Sensitive, Trichromatic RWG Structure

[0041] FIGS. 3A and 3B illustrate a polarization-sensitive, trichromatic RWG structure 300 that can be used as part of a stereoscopic vision system, e.g., in the eyewear of FIG. 1. The structure 300 comprises a first layer 310 of relatively low-index dielectric material, such as Si02, that is patterned with a 2D periodic array of pillars or air holes 312 and deposited on a first layer 320 of relatively high-index dielectric material, such as Si3N4. The first layer 320 of relatively high- refractive index dielectric (or non dielectric) material is disposed on one side of a glass substrate 330. The opposite side of the glass substrate 330 is coated with a second layer 340 of relatively high-index dielectric material and a second layer 350 of relatively low-refractive index material, such as air or a dielectric material, as shown in FIG. 3A.

[0042] One benefit of a hole (or air-pillar) matrix is that little to no matter disappears after the successive etchings. Waveguides are formed for instance by varying the effective index between the successive layers: vacuum, Si0₂, and Si₃N₄. Gratings are formed by modulating the refractive index (for instance, between Ta₂0₅ and air) transversely with respect to the wave propagation direction. The RWG filter 300 may also include one or more anti- Reflection (AR) layers, buffer layers, and/or protective films (not shown). The fill factor is adjusted by the hole or air-pillar diameters.

[0043] FIG. 3B illustrates the periodicity of the air holes 312 patterned in the first layer 310 of relatively low-index dielectric material. The air holes are arranged in a non-orthogonal tiling to form a periodic array of triangles, with each triangle side being proportional to one of the wavelengths filtered by the RWG structure. FIG. 3B shows the tiling triangle angles for a red-green-blue (RGB) filter that reflects light at wavelengths of 637 nm, 525 nm, and 445 nm according to the Al-Kashi rule, or law of cosines. The value of the grating wave vector k depends on the grating period, which is itself a function of the technology choice (Si₃N₄ or Ag on Si0₃ for instance). Here, the respective wavelengths (RGB) are in a given ratio, so that the resulting angles are implementable easily using an air-pillar matrix, which improves the filter selectivity. In this case, the air holes have cross sections that are elliptical because of the non equilateral triangular geometry in order to maintain the same duty cycle for each grating period.

[0044] FIG. 3B shows that each wavelength has an associated grating vector in only one direction, which means that the RWG filter reflects light at that wavelength in the transverse electric (TE) polarization. Stacking two orthogonally oriented trichromatic RWG filters yields a polarization-insensitive filter structure with a first trichromatic RWG filter that reflects TE light at three wavelengths Rl, Gl, and Bl and a second trichromatic RWG filter that reflects light at the same three wavelengths Rl, Gl, and Bl in the transverse magnetic (TM) polarization. TABLE 1 (below) gives some sample wavelength ranges beyond which grating wavelengths and grating periods for a trichromatic RWG filter can be chosen for use in a stereoscopic vision system: TABLE 1

[0045] Because 3D filter glasses may resolve images formed using separate, but very close wavelength combs (see, e.g., TABLE 1 above), manufacturing inaccuracies may affect filter performance— in particular, the efficiency and the selectivity of the filter. For a polarisation-dependent trichromatic RWG filter layer with triangular tiling realised in S1₃N₄ by reactive ion etching (RIE), the grating duty cycle tolerance is about ± 5%. (The absorption coefficient of S1₃N₄ can be neglected in the visible range as shown in FIG. 5, which is a plot of the refractive index (left axis) and absorption coefficient (right axis) of S1₃N₄ at visible and near-infrared wavelengths.) The tolerance for modulation depth, which affects the FWHM, is less stringent. In the example above (430 nm grating period), if the depth varies from 50 nm to 70 nm, the FWHM of the RWG's resonance peak increases by about 4 nm.

[0046] FIGS. 3C-3E illustrate another polarization-sensitive, trichromatic RWG structure 301 that can be used as part of a stereoscopic vision system, e.g., in the eyewear of FIG. 1. The structure 301 comprises a first layer 311 of material, such as Ta₂0₅, that is patterned with a 2D array of grooves 313a, 313b, and 313c (collectively, grooves 313). The grooves 313 have different widths— in this case, grooves 313a are the widest and grooves 313c are the narrowest— and arranged to form a series of non-equilateral triangles. The angles can be chosen with the above-mentioned Al-Kashi rule. The duty cycle (or width) and modulation depth of each groove can be first determined numerically by means of simulation and later by making samples and optimizing the optical properties.

[0047] The grooves 313 can be formed by etching or other removing Ta₂Os and to create air gaps. The grooves 313 may have a modulation depth of between 25 nm and 150 nm (e.g.,

50 nm, 90 nm, or 70 nm as shown in FIG. 3D) and a duty cycle between 20% and 70% (e.g.,

35%) as shown in FIGS. 3D and 3E), where the duty cycle represents the amount of matter removed during the etching process. The groove periods may range between about 200 nm and about 500 nm (e.g., 283 nm, 367 nm, and 497 nm as shown in FIGS. 3D and 3E). The first layer 311 is deposited on a second layer 321 of material with a similar refractive index, such as S1₃N₄, which in turn is disposed on one side of a glass substrate 351. In general, the trichromatic RWG filter structure 301 can be made of a combination of high-low refractive index materials that are relatively transparent at visible wavelengths.

[0048] Polarization-Insensitive, Monochromatic RWG Filters

[0049] Alternatively, the RWG filter structure may comprise stacks of polarization- insensitive, monochromatic RWG filters— one RWG filter for each wavelength being filtered (reflected) by the RWG filter structure. To achieve this aim, each RWG filter may include first and second waveguides (for each polarization state) each supporting a propagation mode; are formed in or on the surface of the first waveguide, the first grating being bi-periodic at least along a first axis θ_χ defining a first orthonormal base θ_χγζ; the second grating being bi- periodic at least along a second axis 9_xy' defining a second orthonormal base θ_χγ_ζ. The combination of two waveguides each supporting a propagation mode with the cascading of two 2D resonant gratings arranged relative to each other provides independence of polarization. The waveguides are constituted of two or more layers of dielectric or non dielectric materials of different refractive index. By way of advantage, the materials used to form the waveguides can be selected such that at least one of them has a refractive index greater than the refractive index of the substrate arranged between the two waveguides.

[0050] FIG. 4A illustrates a full-color RWG filter structure 400 that includes three different polarization-insensitive, monochromatic RWG filters 410a-410c (collectively, polarization-insensitive, monochromatic RWG filters 410). Each RWG 410 filter includes a respective bi-periodic grating 412 that is disposed on a respective waveguide core layer 414 and a respective waveguide cladding 416. As shown in FIG. 4A, each bi-periodic grating 412 is periodic in a pair of orthogonal dimensions in order to diffract incident TE and incident TM waves. The grating period is determined by the wavelength being filtered and the refractive indices of the grating, waveguide core, and waveguide cladding materials. In this example, the monochromatic RWGs 410 are made of the same materials but have a different grating periods, so each diffract incident light of different wavelength (e.g., corresponding to the wavelengths emitted by one of the laser projectors in the stereoscopic vision system of FIG. 1).

[0051] FIG. 4B shows an alternative polarization-insensitive, RGB RWG filter structure 450 based on the filter(s) disclosed in U.S. Patent Application Publication No. 2013/0301988 Al to Monmayrant et al., which is incorporated herein by reference in its entirety. In this case, the filter structure includes six stacked filters 460a-460f, each of which comprises a respective rectangular grating 462 disposed on a respective waveguide core layer 464, which in turn is disposed on a respective waveguide cladding layer 466. The gratings 462 are interleaved such that alternating gratings have grating vectors pointing in different directions (e.g., orthogonal directions as shown in FIG. 4B). And the grating periods are selected such that each pair of gratings diffract light at different wavelengths (e.g., at wavelengths Rl, Gl, and Bl or at wavelengths R2, G2, and B2 as in FIG. 1).

[0052] FIG. 4C shows a polarization-insensitive, trichromatic RWG filter structure 499 based on the polarization-sensitive filter 301 shown in FIGS. 3C-3E. This polarization- insensitive RWG filter structure 499 comprises a first polarization-sensitive filter 401a disposed opposite a transparent spacer (glass layer 498) from another second polarization- sensitive filter 401b (collectively, polarization-sensitive filters 401). The first filter 401a is oriented to transmit light in a first set of polarization states (e.g., TE states) and the second filter 401b is oriented to transmit light in a second set of orthogonal polarization states (e.g., TM states) as described above with respect to FIGS. 4 A and 4B. And as described above with respect to FIGS. 3C-3E, each filter 401 includes a respective patterned layer 411a, 411b that is formed by cutting grooves of different widths arrayed in three directions in a relatively high-index medium, such as Ta₂0₅, e.g., as shown in FIG. 3E. These patterned layers 411a, 411b are disposed on respective layers 421a, 421b of high-index material, such as S1₃N₄, which in turn are disposed on respective transparent substrates 45 la, 45 lb.

[0053] As disclosed below, stacking of the different layers that constitute the optical filter can be achieved via Low-Pressure Chemical Vapor Deposition (LPCVD) or any other suitable technique. The gratings can be formed, for instance, by optical lithography followed by wet etching. They call also be formed using nano-imprint techniques as explained below, e.g., with the following parameters: a grating period A = 360 nm, a duty cycle = 70%, and a modulation depth D = 55 nm. Waveguides are formed by varying the refractive index between the successive layers: Ta₂0₅ Si0₂ and S1₃N₄. Gratings are formed by varying the refractive index modulation between Ta₂Os or S1₃N₄ and the air. The filter structure may also include one or more anti-reflection or protective (anti-scratch) layers (not shown). For bi- periodic gratings, the fill factor can be adjusted by varying the hole diameters.

[0054] Processes for Making RWG Filters for Anaglyph Stereoscopic Vision

[0055] RWG filters for anaglyph stereoscopic vision can be manufactured using any suitable technique. A first suitable technique involves direct photolithography into a photoresist layer followed by a lift-off technique. The resolution of current photo-lithographic steppers used for mass production in the micro-electronics industry is fine enough to produce gratings at the desired periodicities. A second suitable approach uses a nano-imprint master (made by e-beam lithography, for instance), which could be replicated into a layer of photoresist material. This material is then etched using reactive ion etching (RIE) to remove the residual layer and a lift-off process is performed as indicated above. A third suitable technique involves high-speed, two-photon polymerisation technology (2PP), which enables the writing of the photo-resist structures or nano-imprint masters directly.

[0056] FIG. 5 illustrates a lift-off process 500 for making an RWG filter. In step 501, photoresist 512 on a surface of a substrate 510, which may comprise a waveguide core layer and a cladding layer that are transparent at visible wavelengths, is exposed to a light field via a patterned reticle 514 to define holes or rules for the grating. The unexposed photoresist is removed to yield a substrate 520 selectively covered with photoresist in step 502. Next, a grating layer 530, which may be formed of tantalum oxide (e.g., Ta₂0₃ or Ta₂0₅), is deposited on the partially exposed substrate 520 in step 503. In step 504, the remaining photoresist is dissolved (lifted off) in a solvent to yield an RWG filter 540 with a grating layer. This process 500 of photolithography into a photo-resist layer followed by a lift-off of a grating layer may be simpler and less expensive than the technique(s) currently used to manufacture the interference filters. Moreover, this process 500 can be used to achieve fine spatial resolution (e.g., a feature size of about 200 nm) over relatively large areas (e.g., hundreds of square millimeters or larger).

[0057] Other techniques for making RWG structures include but are not limited to electron-beam lithography and direct laser writing. In electron-beam lithography, for example, a focused beam of electrons is scanning across a substrate coated with a layer of photoresist to form a grating pattern, such as a tri-periodic grating pattern formed of three separate rectangular gratings with different grating periods and orientations as shown in FIG. 3E or a triangular lattice of air pillars as shown in FIG. 3B. Immersing the patterned photoresist in a solvent selectively removes the photoresist to form the grating pattern for etching as understood in the art. In direct laser writing, a laser beam is scanned across a layer of tantalum oxide or another suitable transparent grating material disposed on a substrate. The laser beam ablates the layer of tantalum oxide form the grating pattern, which may be a tri-periodic grating pattern formed of three separate rectangular gratings with different grating periods and orientations as shown in FIG. 3E or a triangular lattice of air pillars as shown in FIG. 3B.

[0058] The parameters can also be tuned to offer certain performance advantages. For example, the full-width half-maximum (FWHM) of the diffraction peak can be increased by (a) decreasing the duty cycle of the patterned structure (i.e., the ratio of matter vs air in each of the three directions that are perpendicular to the grooves); (b) increasing the modulation depth (i.e., the thickness of the patterned layer); and (c) increasing the refractive index ratio of the patterned structure to the surrounding media (e.g., the refractive index ratio of Ta₂Os and air as presented in FIG 3D). Generally, a lower duty cycle (less matter) increases the FWHM.

[0059] Simulated Performance of RWG Filters

[0060] The performance of an RWG filter structure can be estimated through modeling and simulation. This modeling and simulation can also include an assessment of the manufacturing tolerance of selected grating parameters (modulation depth, duty cycle, grating period(s), etc.). The RWG filter structure can then be made according to grating parameters and manufacturing option(s) selected based on the results of the modeling and simulation. The manufactured RWG filter structure can be characterized experimentally to determine how closely its performance agrees with the simulated performance. The experimental

characterization can be used to revise the models and perform additional simulations in an iterative fashion.

[0061] A preliminary analysis based on Magnusson theory confirms the utility of reflective RWG filters for anaglyph stereoscopic vision. (For a detailed description of Magnusson theory, see, e.g., S. Tibuleac and R. Magnusson, "Reflection transmission guided- mode resonance filters," JOSAA, Vol. 14, pp. 1617-1626, (1997), which is incorporated herein by reference in its entirety.) For anaglyph stereoscopic vision, the RWG should reflect both polarization states (TE & TM) and three color bands (RGB). This is achieved by using a specific 2D tiling of the planar structure, either by a 2D grating to implement alternatively the trichromatic filter or the polarization insensitivity as disclosed above. This results in a filter stack in both cases: three polarization insensitive filters for each wavelength, or two trichromatic filters for each polarization state.

[0062] FIG. 7 is a plot of simulated diffraction efficiency versus wavelength for a rectangular, tri-periodic grating like the one shown in FIGS. 3C-3E. The tri-periodic grating can be thought of as three superimposed monochromatic RWG filters. The tri-periodic grating is simulated to be a layer of Ta₂0₅, which is deposited on a S1₃N₄ waveguide, etched with a pattern of rectangular grooves like the pattern shown in FIG. 3E. The simulated grating used to generate the plot in FIG. 7 has a duty cycle of 50%, a modulation depth of 50 nm, and groove periods of 261 nm, 323 nm, and 415 nm. The depth and duty cycle are chosen the same for all three sides of the matrix triangle. As explained above, the gratings' modulation depth(s), duty cycle(s), grating period(s), and matrix triangle angles can be tuned to change the filter properties (e.g., the bandwidth(s) and center wavelength(s) of the passbands).

[0063] FIG. 7 shows that, together, the grooves transmit light in red, green, and blue passbands with a peak efficiency of about 100% transmission and a FWHM transmission of about 20 nm in each band. The out-of-band diffraction efficiency, or out-of-band rejection, is greater than 80% for each set of grooves.

[0064] The simulated light source for FIG. 7 is a polarized plane wave at normal incidence. The polarization dependence can be reduced or eliminated by stacking two orthogonal filters, e.g., as shown in FIG. 4C. For example, the filter structure may include two identical filters that are stacked one on top of each other (as shown in FIG. 4C), where the relative angle between the two 2D patterns of the two respective filters is 90°. In other words, the filter structure may have a first grating layer that defines a first copy of a 2D array of grooves in optical communication with a second grating layer that defines a second copy of the 2D array of grooves that is rotated (e.g., by 90°) about an optical axis of the filter structure with respect to the first copy of the 2D array of grooves.

[0065] In addition, a bi-color multiplexed air-pillar filter has been simulated along one direction (blue and red) to confirm the expected performance. The simulations show that the filters are very selective, with narrow linewidths at center wavelengths of about 445 nm for the blue and about 637 nm for the red. The figures have been split, because filters are very narrow and both wavelengths are far from each other. The simulations show the good narrowness, for instance, for the considered blue here (right eye at 445 nm), the second blue (left eye at 465 nm) is rejected around 20 dB. Simulations confirm the theoretical good efficiency of the RWG filter (more than 95%) as mentioned in the literature and summarized in TABLE 2 (below).

[0066] TABLE 2 shows that the resonance filter has a lower sideband transmission and a slightly higher peak transmission than multi-layer interference (Fabry-Perot) filters.

Fortunately, manufacturing should make the RWG filter FWHM even narrower, making the RWG filter suitable for resolving anaglyph images projected by current laser diodes used in movies projectors, which typically have emission bandwidths of about 10 nm.

TABLE 2

i^: i ··¾«··.¾

; w- .2 sis [0067] Simulations based on air-pillar gratings (hole matrix) show that the selectivity is significantly improved (when compared to the selectivity of the rectangular gratings design), making both this technology and diffractive structure (i.e., an elliptical air-pillar matrix) very appropriate for the manufacturing of 6P 3D glasses. In other words, simulations suggests that air-pillar gratings can achieve more narrow FWHM than rectangular gratings. As with the rectangular grating designs, the filter FWHM of air-pillar gratings can be adjusted efficiently by appropriately choosing the duty cycle, the modulation depth, and the grating refractive index modulation. Because air-pillar matrix designs can be made highly selective, they are suitable for use with 6-laser source projectors (instead of a 6 laser cluster projector) because one could fine tune the narrow peaks to the laser peaks. This way, the overlap between the filter bands would decrease, thus decreasing the crosstalk. It could also potentially mean an increase in transparency since fewer compromises would need to be made when choosing (e.g., optimizing ) the optical properties (with other designs, there may be some compromises between crosstalk and transparency because of possible overlap of the filter passbands).

[0068] Conclusion

[0069] While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. [0070] The above-described embodiments can be implemented in any of numerous ways. For example, embodiments of designing and making the coupling structures and diffractive optical elements disclosed herein may be implemented using hardware, software or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed among multiple computers.

[0071] Further, it should be appreciated that a computer may be embodied in any of a number of forms, such as a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. Additionally, a computer may be embedded in a device not generally regarded as a computer but with suitable processing capabilities, including a Personal Digital Assistant (PDA), a smart phone or any other suitable portable or fixed electronic device.

[0072] Also, a computer may have one or more input and output devices. These devices can be used, among other things, to present a user interface. Examples of output devices that can be used to provide a user interface include printers or display screens for visual presentation of output and speakers or other sound generating devices for audible presentation of output. Examples of input devices that can be used for a user interface include keyboards, and pointing devices, such as mice, touch pads, and digitizing tablets. As another example, a computer may receive input information through speech recognition or in other audible format.

[0073] Such computers may be interconnected by one or more networks in any suitable form, including a local area network or a wide area network, such as an enterprise network, and intelligent network (IN) or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol and may include wireless networks, wired networks or fiber optic networks.

[0074] The various methods or processes (e.g., of designing and making the coupling structures and diffractive optical elements disclosed above) outlined herein may be coded as software that is executable on one or more processors that employ any one of a variety of operating systems or platforms. Additionally, such software may be written using any of a number of suitable programming languages and/or programming or scripting tools, and also may be compiled as executable machine language code or intermediate code that is executed on a framework or virtual machine.

[0075] In this respect, various inventive concepts may be embodied as a computer readable storage medium (or multiple computer readable storage media) (e.g., a computer memory, one or more floppy discs, compact discs, optical discs, magnetic tapes, flash memories, circuit configurations in Field Programmable Gate Arrays or other semiconductor devices, or other non-transitory medium or tangible computer storage medium) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments of the invention discussed above. The computer readable medium or media can be transportable, such that the program or programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the present invention as discussed above.

[0076] The terms "program" or "software" are used herein in a generic sense to refer to any type of computer code or set of computer-executable instructions that can be employed to program a computer or other processor to implement various aspects of embodiments as discussed above. Additionally, it should be appreciated that according to one aspect, one or more computer programs that when executed perform methods of the present invention need not reside on a single computer or processor, but may be distributed in a modular fashion amongst a number of different computers or processors to implement various aspects of the present invention.

[0077] Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0078] Also, data structures may be stored in computer-readable media in any suitable form. For simplicity of illustration, data structures may be shown to have fields that are related through location in the data structure. Such relationships may likewise be achieved by assigning storage for the fields with locations in a computer-readable medium that convey relationship between the fields. However, any suitable mechanism may be used to establish a relationship between information in fields of a data structure, including through the use of pointers, tags or other mechanisms that establish relationship between data elements.

[0079] Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0080] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. [0081] The indefinite articles "a" and "an," as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean "at least one."

[0082] The phrase "and/or," as used herein in the specification and in the claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with "and/or" should be construed in the same fashion, i.e., "one or more" of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the "and/or" clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to "A and/or B", when used in conjunction with open-ended language such as "comprising" can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0083] As used herein in the specification and in the claims, "or" should be understood to have the same meaning as "and/or" as defined above. For example, when separating items in a list, "or" or "and/or" shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as "only one of or "exactly one of," or, when used in the claims, "consisting of," will refer to the inclusion of exactly one element of a number or list of elements. In general, the term "or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e. "one or the other but not both") when preceded by terms of exclusivity, such as "either," "one of," "only one of," or "exactly one of." "Consisting essentially of," when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0084] As used herein in the specification and in the claims, the phrase "at least one," in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently "at least one of A and/or B") can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0085] In the claims, as well as in the specification above, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "composed of," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of and "consisting essentially of shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

1. Eyewear for viewing a full-color stereoscopic image, the eyewear comprising:

a first resonant waveguide filter to reject light at a first wavelength less than about 495 nm, a second wavelength between about 495 nm and 570 nm, and a third wavelength greater than about 570 nm and to transmit light at a fourth wavelength less then about 495 nm, a fifth wavelength between about 495 nm and 570 nm, and a sixth wavelength greater than about 570 nm;

a second resonant waveguide filter to transmit light at the first wavelength, the second wavelength, and the third wavelength and to reject light at the fourth wavelength, the fifth wavelength, and the sixth wavelength; and

a frame, mechanically coupled to the first resonant waveguide filter and the second resonant waveguide filter, to hold the first resonant waveguide filter in front of a first eye of a user and to hold the second resonant waveguide filter in front of a second eye of the user.

2. The eyewear of claim 1 , wherein the first resonant waveguide filter comprises:

a first polarization-insensitive filter to filter light at the fourth wavelength;

a second polarization-insensitive filter, in optical communication with the first polarization-insensitive filter, to filter light at the fifth wavelength; and

a third polarization-insensitive filter, in optical communication with the first polarization-insensitive filter and the first polarization-insensitive filter, to filter light at the sixth wavelength.

3. The eyewear of claim 2, wherein the first polarization-insensitive filter comprises: a cladding layer having a first refractive index;

a core layer, disposed on the cladding layer, having a second refractive index greater than the first refractive index; and

a tri-periodic grating, disposed on the core layer, to couple light at the fourth wavelength into the core layer.

4. The eyewear of claim 1 , wherein the first resonant waveguide filter comprises:

a first trichromatic filter to reject light in a first polarization state at the first wavelength, light in a second polarization state at the second wavelength, and light in a third polarization state at the third wavelength; and

a second trichromatic filter, in optical communication with the first trichromatic filter,

5. The eyewear of claim 4, wherein the first trichromatic filter comprises:

a transparent substrate having a first refractive index; and a dielectric layer disposed on a surface of the transparent substrate, having a second refractive index greater than the first refractive index, and patterned with at least one of a two- dimensional array of grooves or a two-dimensional array of holes.

6. The eyewear of claim 5, wherein the two-dimensional array of grooves comprises: at least one first groove having a first width;

at least one second groove having a second width different than the first width; and at least one third groove having a third width different than the first width and the second width.

7. The eyewear of claim 5, wherein the two-dimensional array of holes comprises at least one hole having an elliptical cross section.

8. The eyewear of claim 5, wherein the at least one of the two-dimensional array of holes or the two-dimensional array of grooves has a first period a in a first direction in a plane parallel to the surface of the transparent substrate, a second period b in a second direction in the plane parallel to the surface of the transparent substrate, and a third period c in a third direction in the plane parallel to the surface of the transparent substrate.

9. The eyewear of claim 8, wherein the first period a, the second period b, and the third period c define a unitary triangle having interior angles given by:

a = arcos[(b² + c² - a²)/2bc]

β = arcos[(a² + c² - b²)/2ca], and

γ = arcos[(a² + b² - c²)/2ab].

10. The eyewear of claim 1, wherein:

the first wavelength is between about 430 nm and 470 nm;

the second wavelength is between about 505 nm and about 545 nm;

the third wavelength is between about 630 nm and about 670 nm;

the fourth wavelength is between about 440 nm and about 480 nm;

the fifth wavelength is between about 515 nm and about 555 nm; and

the sixth wavelength is between about 640 nm and about 680 nm.

11. Eyewear for resolving (i) a left-hand anaglyph image formed of light at a first wavelength less than about 495 nm, a second wavelength between about 495 nm and about 570 nm, a third wavelength greater than about 570 nm and (ii) a right-hand anaglyph image formed of light at a fourth wavelength less than about 495 nm, a fifth wavelength between about 495 nm and about 570 nm, and a sixth wavelength greater than about 570 nm, the eyewear comprising:

a first resonant waveguide filter to transmit the left-hand image and to reject the right- hand image; a second resonant waveguide filter to reject the left-hand image and to transmit the right-hand image; and

a frame, mechanically coupled to the first resonant waveguide filter and to the second resonant waveguide filter, to hold the first resonant waveguide filter in front of a left eye of a viewer and to hold the second resonant waveguide filter in front of a right eye of the viewer.

12. The eyewear of claim 11, wherein the first resonant waveguide filter comprises:

a second trichromatic filter, in optical communication with the first trichromatic filter, to reject light in a fourth polarization state orthogonal to the first polarization state at the first wavelength, light in a fifth polarization state orthogonal to the second polarization state at the second wavelength, and light in a sixth polarization state orthogonal to the third polarization state at the third wavelength.

13. The eyewear of claim 12, wherein the first trichromatic filter comprises:

a transparent substrate having a first refractive index; and

a transparent layer disposed on a surface of the transparent substrate, having a second refractive index greater than the first refractive index, and patterned with at least one of a two- dimensional array of grooves or a two-dimensional array of holes.

14. The eyewear of claim 13, wherein the two-dimensional array of grooves comprises: at least one first groove having a first width;

15. The eyewear of claim 13, wherein the two-dimensional array of holes comprises at least three holes arranged in a triangle having a first side whose length is proportional to the first wavelength, a second side whose length is proportional to the second wavelength, and a third side whose length is proportional to the third wavelength.

16. The eyewear of claim 15, wherein the at least three holes have respective elliptical cross sections.

17. A method of resolving (i) a left-hand anaglyph image formed of light at a first wavelength less than about 495 nm, a second wavelength between about 495 nm and about 570 nm, a third wavelength greater than about 570 nm and (ii) a right-hand anaglyph image formed of light at a fourth wavelength less than about 495 nm, a fifth wavelength between about 495 nm and about 570 nm, and a sixth wavelength greater than about 570 nm, the method comprising:

(A) transmitting the left-hand image through a first resonant waveguide filter disposed over a left eye of a viewer; and

(B) transmitting the right-hand image through a second resonant waveguide filter disposed over a left eye of a viewer.

18. A method of making eyewear for anaglyph stereoscopic vision, the method

comprising:

(A) providing a substrate that transmit light at visible wavelengths, the substrate comprising a core layer and a cladding layer;

(B) depositing a resist on a surface of the core layer;

(C) patterning the resist to selectively expose portions of the core layer;

(D) depositing a grating material onto the selectively exposed portions of the substrate;

(E) removing the resist to form a resonant waveguide guide comprising a grating on the core layer; and

(F) mechanically coupling the resonant waveguide guide to an eyewear frame.

19. The method of claim 18, wherein (C) comprises defining at least one of a plurality of grooves or a plurality of holes arrayed on a triangular lattice, the triangular lattice having a first period proportional to a first wavelength less than about 495 nm, a second period proportional to a second wavelength between about 495 nm and about 570 nm, and a third period proportional to a third wavelength greater than about 570 nm.

20. The method of claim 19, wherein (C) comprises defining:

at least one first groove having a first width;

21. The method of claim 19, wherein (C) comprises defining at least one in the plurality of holes to have an elliptical cross section.

22. The method of claim 18, wherein (C) comprises photo lithographically patterning the resist.

23. The method of claim 18, wherein (C) comprises patterning the resist via nano-imprint lithography.

24. An anaglyph stereoscopic vision system, the system comprising

at least one light source to emit light at a first wavelength less than about 495 nm, a second wavelength between about 495 nm and about 570 nm, a third wavelength greater than about 570 nm, a fourth wavelength less than about 495 nm, a fifth wavelength between about 495 nm and about 570 nm, and a sixth wavelength greater than about 570 nm;

at least one spatial light modulator (SLM), in optical communication with the at least one light source, to spatially modulate the light emitted by the at least one light source so as to form a left-hand image comprising light at the first wavelength, the second wavelength, and third wavelength and a right-hand image comprising light at the fourth wavelength, the fifth wavelength, and sixth wavelength; and

eyewear, in optical communication with the at least one SLM, to resolve the into a left-hand image from the right-hand image, the eyewear comprising:

a first resonant waveguide filter to transmit the left-hand image and to reject the right-hand image;

a second resonant waveguide filter to reject the left-hand image and to transmit the right-hand image; and

25. The system of claim 24, wherein the first resonant waveguide filter comprises:

26. The system of claim 25, wherein the first trichromatic filter comprises:

a transparent substrate having a first refractive index; and

a transparent layer disposed on a surface of the transparent substrate, having a second refractive index greater than the first refractive index, and patterned with the two-dimensional array of grooves or the two-dimensional array of holes.

27. The system of claim 26, wherein the two-dimensional array of grooves comprises: at least one first groove having a first width;

28. The system of claim 26, wherein the two-dimensional array of holes comprises at least three holes arranged in a triangle having a first side whose length is proportional to the first wavelength, a second side whose length is proportional to the second wavelength, and a third side whose length is proportional to the third wavelength.

29. The system of claim 28, wherein the at least three holes have respective elliptical cross sections.

30. Eyewear for viewing a full-color stereoscopic image, the eyewear comprising:

a first polarization-insensitive resonant waveguide filter to pass light at a first plurality of visible wavelengths and to reject light at a second plurality of visible wavelengths, the first polarization-insensitive resonant waveguide filter comprising:

a first grating layer defining a first copy of a first two-dimensional array of grooves; and

a second grating layer, in optical communication with the first grating layer, defining a second copy of the first two-dimensional array of grooves rotated about an optical axis of the first polarization-insensitive resonant waveguide filter with respect to the first copy of the first two-dimensional array of grooves;

a second polarization-insensitive resonant waveguide filter to pass light at the first plurality of visible wavelengths and to reject light at the second plurality of visible wavelengths, the second polarization-insensitive resonant waveguide filter comprising:

a third grating layer defining a first copy of a second two-dimensional array of grooves different from the first two-dimensional array of grooves; and

a fourth grating layer, in optical communication with the third grating layer, defining a second copy of the second two-dimensional array of grooves rotated about an optical axis of the second polarization-insensitive resonant waveguide filter with respect to the first copy of the second two-dimensional array of grooves;

a frame, mechanically coupled to the first polarization-insensitive resonant waveguide filter and the second polarization-insensitive resonant waveguide filter, to hold the first polarization-insensitive resonant waveguide filter in front of a first eye of a user and to hold the second polarization-insensitive resonant waveguide filter in front of a second eye of the user.

31. The system of claim 30, wherein the first two-dimensional array of grooves comprises:

a plurality of first grooves, each first groove in the plurality of first grooves having a first width;

a plurality of second grooves, each second groove in the plurality of second grooves having a second width different than the first width; and

a plurality of third grooves, each third groove in the plurality of third grooves having a third width different than the first width and the second width.

32. The eyewear of claim 30, wherein:

the first polarization-insensitive resonant waveguide filter is configured to reject incident light in a first band with a maximum wavelength of less than about 495 nm, a second band between about 495 nm and about 570 nm, and a third band having a minimum wavelength greater than about 570 nm and to pass incident light in a fourth band with a maximum wavelength of less than a minimum wavelength of the first band, a fifth band between the maximum wavelength of the first band and a minimum wavelength of the second band or between a maximum wavelength of the second band and the minimum wavelength of the third band, and a sixth band having a minimum wavelength greater than a maximum wavelength of the third band, and

the second polarization-insensitive resonant waveguide filter is configured to pass incident light in the first band, the second band, and the third band and to reject incident light in the fourth band, the fifth band, and the sixth band.