Dispersion compensation in diffractive augmented reality systems

Abstract

The invention relates to an augmented reality device and a related method. In one or more embodiments, an augmented reality device includes a projection system and a waveguide. The projection system comprises a projector and a prism. The projector projects an image along a projector axis. The prism refracts an image having a first spectrum, a second spectrum, and a third spectrum. The waveguide is disposed at a wrap angle with a plane formed by the main axis of the projector. The waveguide includes an input coupler and an output coupler. The input coupler includes input structures in an input period and an input orientation, and the input coupler is configured to receive the spectrum at different corresponding input angles. The output coupler includes an output structure in an output period and an output orientation, and the output coupler out-couples the respective spectra at substantially equal output angles.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to waveguides and augmented reality devices having a projection system and a waveguide. BACKGROUND

[0002] Virtual reality is generally considered to be a computer-generated simulated environment in which a user has apparent physical presence. Virtual reality can be generated in 3D form and viewed using a head-mounted display (HMD), such as glasses or other wearable display devices having a near-eye display panel as a lens, to display a virtual reality environment that replaces the actual environment. However, augmented reality enables an experience in which a user can still see the surrounding environment through the display lens of the glasses or other HMD devices, while also seeing images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as audio and haptic input, as well as virtual images, graphics, and video that enhance or augment the environment experienced by the user. As an emerging technology, augmented reality presents many challenges and design constraints. Therefore, there is a need in the art for augmented reality devices having a projection system and a waveguide. SUMMARY

[0003] Embodiments of the present disclosure relate to augmented reality devices and related methods. In one or more embodiments, an augmented reality device includes a projection system and a waveguide. The projection system includes a projector and a prism. The projector projects an image along a principal axis of the projector. The prism refracts the image having a first spectrum, a second spectrum, and a third spectrum. The waveguide is disposed at an included angle to a plane formed by the principal axis of the projector. The waveguide includes an input coupler and an output coupler. The input coupler includes input structures at an input period and an input orientation, and the input coupler is configured to receive the spectra at different corresponding input angles. The output coupler includes output structures at an output period and an output orientation, and the output coupler out-couples the respective spectra at substantially equal output angles.

[0004] In one or more embodiments, an augmented reality device is provided. The augmented reality device includes a frame arm coupled to a frame, a projection system, and a waveguide. The projection system is disposed in the frame arm. The projection system includes a projector having a principal axis and configured to project an image along the principal axis. The projection system also includes a prism configured to refract the image. The image includes a first spectrum, a second spectrum, and a third spectrum. The waveguide is coupled to the frame arm and disposed at an included angle to a plane formed by the principal axis of the projector. The waveguide includes an input coupler having input structures disposed at an input period and an input orientation, and an output coupler having output structures disposed at an output period and an output orientation.

[0005] In one or more embodiments, an augmented reality device is provided. The augmented reality device includes a projection system and a waveguide. The projection system includes a projector and a prism. The projector has a main axis and is configured to project an image along the main axis. The prism is configured to refract the image. The image includes a first spectrum, a second spectrum, and a third spectrum. The waveguide is disposed at an angle to the plane formed by the main axis of the projector. The waveguide includes: an input coupler having an input structure configured with an input period and an input orientation; a pupil expander having a pupil structure configured with a pupil period and a pupil orientation; and an output coupler having an output structure configured with an output period and an output orientation. Attached Figure Description

[0006] To gain a more detailed understanding of the features described above, reference can be made to embodiments that are briefly outlined above, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings only illustrate exemplary embodiments of the disclosure and should not be considered as limiting its scope, allowing for other equivalent embodiments. To gain a more detailed understanding of the features described above, a more specific description of the disclosure, briefly outlined above, can be obtained with reference to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings only illustrate exemplary embodiments of the disclosure and should not be considered as limiting its scope, but rather allow for other equally effective embodiments.

[0007] Figure 1A This is a schematic top view of an augmented reality device according to embodiments described herein.

[0008] Figure 1B According to the embodiments described herein Figure 1A A schematic cross-sectional view of a portion of the augmented reality device.

[0009] Figure 2A This is a schematic top view of a waveguide according to an embodiment described herein.

[0010] Figure 2B According to the embodiments described herein Figure 2A k-space diagram of waveguides in the image.

[0011] Figure 3A This is a schematic top view of a waveguide according to an embodiment described herein.

[0012] Figure 3B It is according to the embodiments described herein, corresponding to Figure 3A k-space diagram of waveguides in the image.

[0013] Figure 3C According to some embodiments Figure 3A A schematic top view of the waveguide input coupler in the diagram.

[0014] For ease of understanding, the same element symbols have been used, where possible, to designate the same element common to the various figures. It is contemplated that elements and features of one embodiment can be beneficially incorporated into other embodiments without further recitation. DETAILED DESCRIPTION

[0015] Embodiments of the present disclosure generally relate to waveguides for augmented reality, mixed reality, or virtual reality. In particular, embodiments described herein provide an optical system for augmented reality (AR) in which a user can see through display lenses of glasses or other head-mounted display devices to the surrounding environment and see images of virtual objects generated for display and appearing as part of the environment. A prism can be placed along the optical path between the projector and the waveguide. Adjusting the angle of the projector at a tilt angle of the projector can cause the optical system to lose ergonomic properties. Likewise, using the prism alone can cause light to refract along the optical path, reducing image quality. Complex prisms can minimize chromatic dispersion but increase manufacturing cost. Embodiments of the present disclosure relate to a combination of a prism and a diffractive waveguide to minimize image blur, maintain ergonomic design, and reduce manufacturing cost.

[0016] Figure 1A is a schematic top view of an augmented reality device 100. Figure 1B is a schematic cross-sectional view of a portion of the augmented reality device 100 in operation. The device 100 includes a projection system 101 and a waveguide 300a. The projection system 101 includes a projector 102 and a prism 103. The projector 102 is coupled to a frame arm 104. The frame arm 104 is coupled to a frame 106. The frame 106 holds the waveguide 300a and couples the waveguide 300a to the frame arm 104. The waveguide 300a is disposed at a wrap angle 109. A plane 111 is perpendicular to a principal axis 112 of the projector 102. The plane 111 is formed to have the principal axis 112 as a normal vector of the plane 111. The device 100 includes the wrap angle 109 between the plane 111 and the waveguide 300a. The wrap angle 109 is about -10° to about 30°. For example, the wrap angle 109 is about 1° to about 10°. In some embodiments, the principal axis 112 of the projector 102 is substantially parallel to an eye axis 107 of a user’s eye 105. In some embodiments, the principal axis 112 of the projector 102 is at an angle of about -10° to about 30° to the eye axis 107 of the user’s eye 105.

[0017] To improve ergonomics, reduce weight, and reduce the size of the device 100, it is desirable to align the projector 102 within the frame arm 104 when the waveguide 300a is disposed at the wrap angle 109. The projector 102 and the prism 103 are disposed in the frame arm 104 such that the principal axis 112 of the projector 102 is aligned with the frame arm 104. The prism 103 is configured to refract the image 117 from the projector 102 toward the waveguide 300a. The prism 103 allows the projector 102 to be disposed in the frame arm 104 without being tilted inward toward the user’s temple, while still accounting for the wrap angle 109. This orientation allows the width of the frame arm 104 of the frame 106 to be reduced, thereby enhancing the ergonomics. The projector 102 and the prism 103 in combination with the waveguide 300a operate to enable lower complexity of manufacture of the prism 103 due to the waveguide 300a mitigating the dispersion of the prism 103.

[0018] The projector 102 is operable to project the image 117 comprising a first spectrum 117a, a second spectrum 117b, and a third spectrum 117c of light. In some embodiments, the first spectrum 117a corresponds to blue light, the second spectrum 117b corresponds to green light, and the third spectrum 117c corresponds to red light. The prism 103 of the projection system 101 enables the in-coupling of the image 117 through the waveguide 300a. In operation, the first spectrum 117a, the second spectrum 117b, and the third spectrum 117c (hereinafter referred to as “spectra 117a, 117b, 117c”) are refracted by the prism 103 before entering the input coupler 301 disposed at the wrap angle 109. As shown, the first spectrum 117a, the second spectrum 117b, and the third spectrum 117c enter the input coupler 301 at corresponding first, second, and third input angles 118a, 118b, and 118c (hereinafter referred to as “input angles 118a, 118b, 118c”). When the image 117 passes through the prism 103, different wavelengths of light bend and change speed as they travel between media with different refractive indices. For example, when light travels from a lower refractive index to a higher refractive index, the light deviates from the normal vector at an angle. The wavelength of the light determines the degree to which the light deviates from the normal vector. Figure 1B

[0019] ​The prism 103 bends the image 117 from the projector 102 towards the input coupler 301 to accommodate the wrap angle 109. The prism 103 refracts the image 117 so that each of the spectra 117a, 117b, 117c travels through the prism 103 at a different rate and exits the prism 103 at a different angle. The variation between the spectra 117a, 117b, 117c results in the spectra 117a, 117b, 117c entering the input coupler at different input angles 118a, 118b, 118c. In some embodiments, the prism 103 is a three- prism of a single material. In some embodiments, the prism 103 is a two-prism of two materials, but other higher order prisms are also contemplated.

[0020] In a head mounted display (HMD) incorporating the apparatus 100, the waveguide 300a is set at the wrap angle 109 and aligned along the frame arm 104 to the principal axis 112 of the projector 102, improving the usability of the apparatus 100. The usability is improved by increasing comfort and reducing the size of the HMD while maintaining a clear image 117 received by the eye 105. The apparatus 100 incorporates the prism 103 so that the projector 102 is parallel to the frame arm 104. The waveguide 300a compensates for any dispersion and refraction of the prism 103 so that the k-vector of the waveguide 300a corresponds to the k-vector of the prism 103. The waveguide 300a compensates for the prism 103 by diffracting the first spectrum 117a, the second spectrum 117b, and the third spectrum 117c so that the first spectrum 117a, the second spectrum 117b, and the third spectrum 117c travel to the user’s eye 105 at the same angle from the output coupler 305.

[0021] Figure 2A is a schematic top view of a waveguide 200a. The waveguide 200a is an uncompensated waveguide. That is, the waveguide 200a does not compensate for the refractive dispersion of the prism 103 so that the k-vector change through the waveguide 200a is 0. Figure 2B is a k-space map 200b of the waveguide 200a. The waveguide 200a includes an input coupler 201, a pupil expander 203, and an output coupler 205 disposed on a substrate 115.

[0022] The input coupler 201 includes an input structure 221. The input structure 221 has an input period 222 and an input orientation 232. The input period 222 is the distance between the midpoints of adjacent input structures 221. In some embodiments, the input period 222 is defined as the distance between the leading edges of adjacent input structures 221. The input period 222 is the same when measured between the midpoints or the leading edges of adjacent input structures 221. The input period 222 is about 10 nanometers (nm) to about 200 nm. As Figure 2AAs shown, the input orientation 232 of the input coupler 201 of the waveguide 200a is defined by the angle between the x-axis and the normal vector 231 of the input structure 221. Without compensation, the normal vector 231 is aligned with the input orientation 232 in the waveguide 200a. As shown, the input orientation 232 is along the x-axis, with an input orientation of 0°.

[0023] The pupil expander 203 includes pupil structures 223. The pupil structures 223 have a pupil period 224 and a pupil orientation 234. The pupil period 224 is the distance between the midpoints of adjacent pupil structures 223. In some embodiments, the pupil period 224 is defined as the distance between the leading edges of adjacent pupil structures 223. The pupil period 224 is the same when measured between the midpoints or the leading edges of adjacent pupil structures 223. The pupil period 224 is about 10 nanometers (nm) to about 200 nm. As shown, the pupil structures 223 are arranged in a periodic pattern. Figure 2A As shown, the pupil orientation 234 of the pupil expander 203 of the waveguide 200a is defined by the angle between the x-axis and the normal vector 233 of the pupil structures 223. The pupil orientation 234 is about 90°.

[0024] The output coupler 205 includes output structures 225. The output structures 225 have an output period 226 and an output orientation 236. The output period 226 is the distance between the midpoints of adjacent output structures 225. In some embodiments, the output period 226 is defined as the distance between the leading edges of adjacent output structures 225. The output period 226 is the same when measured between the midpoints or the leading edges of adjacent output structures 225. The output period 226 is about 10 nanometers (nm) to about 200 nm. As shown, the output structures 225 are arranged in a periodic pattern. Figure 2A As shown, the output orientation 236 of the output coupler 205 of the waveguide 200a is defined by the angle between the x-axis and the normal vector 235 of the output structures 225.

[0025] When the first, second, and third light spectra 117a, 117b, 117c enter the input coupler 201 at corresponding first, second, and third input angles 118a, 118b, 118c (input angles 118a, 118b, 118c), the light spectra 117a, 117b, 117c experience total internal reflection (TIR) within the waveguide 200a. As shown, the input angles 118a, 118b, 118c are the same as the input orientation 232 of the input coupler 201. Figure 2BThe projector 102 projects an image 117 having a first spectrum 117a, a second spectrum 117b, and a third spectrum 117c (hereinafter referred to as "spectra 117a, 117b, 117c"). The image 117 is diffracted by the prism 103 such that the input angles 118a, 118b, 118c of the spectra 117a, 117b, 117c at the input coupler 201 are different from one another. That is, the spectra 117a, 117b, 117c have corresponding input angles 118a, 118b, 118c that spread the spectra 117a, 117b, 117c across the input coupler 201.

[0026] The first spectrum 117a, the second spectrum 117b, and the third spectrum 117c exit the output coupler 205 at corresponding first, second, and third output angles 218a, 218b, 218c. The first, second, and third output angles 218a, 218b, 218c (output angles 218a, 218b, 218c) are different from one another. Because the spectra 117a, 117b, 117c exit the output coupler 205 at different output angles 218a, 218b, 218c, the image 117 is blurred and lacks sharpness. That is, the output angles 218a, 218b, 218c spread the spectra 117a, 117b, 117c across the user's eye 105. The waveguide 200a has minimal variation in k- vectors of the image passing through the waveguide. Thus, the image 117, which is dispersed into the first spectrum 117a, the second spectrum 117b, and the third spectrum 117c, enters and exits the waveguide 200a as a dispersed image that appears blurred and lacks sharpness.

[0027] Figure 3A is a schematic top view of a waveguide 300a. The waveguide 300a is a compensating waveguide. The waveguide 300a compensates for the refractive dispersion of the prism 103 such that the k-vector variation through the waveguide 300a is non-zero. That is, the k-vector variation is greater than or less than zero. Figure 3Bis a k-space map 300b of the waveguide 300a. The waveguide 300a further described herein includes an architecture of an input coupler 301, a pupil expander 303, and an output coupler 305 such that the first, second, and third light spectra 117a, 117b, 117c exit the output coupler 305 at corresponding first, second, and third output angles 318a, 318b, 318c. The first, second, and third output angles 318a, 318b, 318c (output angles 318a, 318b, 318c) are approximately the same as one another, while the input angles 118a, 118b, 118c are different. The waveguide 300a compensates for the different input angles 118a, 118b, 118c to produce an image 350 at approximately uniform angles that is very clear when viewed by the eye 105. The waveguide 300a includes k-vectors. The k-vectors of the waveguide 300a are non-zero vectors and are the inverse of the k-vectors of the prism 103 Figure 1A The waveguide 300a compensates for the prism 103 by diffracting the image 117 corresponding to the refractive dispersion of the prism 103.

[0028] The input coupler 301, the pupil expander 303, and the output coupler 305 are each disposed on a substrate 115. The substrate 115 can include a substrate of any appropriate material, including but not limited to amorphous dielectrics, crystalline dielectrics, polycrystalline dielectrics, silicon-containing materials, polymers, and combinations thereof. In one embodiment, which can be combined with other embodiments described herein, the substrate 115 includes one or more of silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), fused quartz, diamond, or a quartz material. In some embodiments, which can be combined with other embodiments described herein, the substrate 115 includes one or more of a nitrogen-, titanium-, niobium-, lanthanum-, zirconium-, or yttrium-containing material. The substrate 115 can include an optical material having a refractive index of about 2, such as about 1.7 to 2.3, about 1.8 to 2.2, about 1.9 to 2.1, or about 2.0 to 2.1.

[0029] The input coupler 301 includes an input structure 321. The input structure 321 has an input period 322 and an input orientation 332. The input period 322 is the distance between the midpoints of adjacent input structures 321. In some embodiments, the input period 322 is defined as the distance between leading edges of adjacent input structures 321. The input period 322 is the same when measured between the midpoints or leading edges of adjacent input structures 321. The input period 322 is about 10 nanometers (nm) to about 300 nm. The input period 322 is different than the input period 222. As Figure 3AAs shown, the input orientation 332 of the input coupler 301 of the waveguide 300a is defined by the angle between the x-axis and the normal vector 331 of the input structure 321. The input orientation 332 is greater than 0°. In some embodiments, the input coupler 301 component of the k-vector of the waveguide 300a is compensated for the dispersion of the prism 103 by adjusting the input period 322 and the input orientation 332. That is, the prism 103 refracts the image 117 by a first k-vector, and the k-vector component corresponding to the input coupler 301 is configured to diffract the image 117, the k-vector component of the input coupler 301 being the inverse of the k-vector of the prism 103.

[0030] The pupil expander 303 includes pupil structures 323. The pupil structures 323 have a pupil period 324 and a pupil orientation 334. The pupil period 324 is the distance between the midpoints of adjacent pupil structures 323. In some embodiments, the pupil period 324 is defined as the distance between the leading edges of adjacent pupil structures 323. The pupil period 324 is the same when measured between the midpoints or the leading edges of adjacent pupil structures 323. The pupil period 324 is from about 10 nanometers (nm) to about 300 nm. As shown, the pupil orientation 334 of the pupil expander 303 of the waveguide 300a is defined by the angle between the x-axis and the normal vector 333 of the input structure 323. The pupil orientation 334 is greater than or less than 45°. Figure 3A

[0031] The output coupler 305 includes output structures 325. The output structures 325 have an output period 326 and an output orientation 336. The output period 326 is the distance between the midpoints of adjacent output structures 325. In some embodiments, the output period 326 is defined as the distance between the leading edges of adjacent output structures 325. The output period 326 is the same when measured between the midpoints or the leading edges of adjacent output structures 325. The output period 326 is from about 10 nanometers (nm) to about 300 nm. The output orientation 336 is defined as the angle between the x-axis and the normal vector 335 of the output structure 325. The output orientation 336 is greater than or less than 90°.

[0032] When the first, second, and third light spectra 117a, 117b, and 117c enter the input coupler 301 at corresponding first, second, and third input angles 118a, 118b, and 118c (input angles 118a, 118b, 118c), the light spectra 117a, 117b, 117c experience total internal reflection (TIR) within the waveguide 300a. As shown, the first, second, and third light spectra 117a, 117b, and 117c are diffracted by the input coupler 301 and the pupil expander 303, and the output coupler 305 outputs the first, second, and third light spectra 117a, 117b, and 117c as first, second, and third output angles 119a, 119b, and 119c (output angles 119a, 119b, 119c). Figure 3B ​The projector 102 is configured to project an image 117 having a first spectrum 117a, a second spectrum 117b, and a third spectrum 117c into the input coupler 301 at different input angles 118a, 118b, 118c, as shown in the k-space diagram 300b. The first spectrum 117a, the second spectrum 117b, and the third spectrum 117c exit the output coupler 305 at corresponding first, second, and third output angles 318a, 318b, 318c (output angles 318a, 318b, 318c). In comparison to the k-space diagram 200b, the output angles 318a, 318b, 318c are approximately the same, and the resulting image 350 is also clear.

[0033] In some embodiments, different wavelengths of the first spectrum 117a enter the input coupler 301 as a first incident cone at the first input angle 118a, the different wavelengths of the first spectrum 117a forming an apex angle of the first incident cone. Different wavelengths of the second spectrum 117b enter the input coupler 301 as a second incident cone at the second input angle 118b, the different wavelengths of the second spectrum 117b forming an apex angle of the second incident cone. Different wavelengths of the third spectrum 117c enter the input coupler 301 as a third incident cone at the third input angle 118c, the different wavelengths forming an apex angle of the third incident cone. The waveguide 300a aligns centers of the cones of different input angles 118a, 118b, 118c to approximately the same angle and further reduces the apex angle of each of the first incident cone of the first spectrum 117a, the second incident cone of the second spectrum 117b, and the third incident cone of the third spectrum 117c, thereby tightly aligning wavelengths within each spectrum with their respective output angles 318a, 318b, 318c.

[0034] The waveguide 300a compensates for the prism 103 by adjusting at least one or more of the input period 322, the input orientation 332, the pupil period 324, the pupil orientation 334, the output period 326, and the output orientation 336, such that the k-space diagram 300b has a non-zero k-vector. That is, the k-vector of the waveguide 300a is the inverse k-vector of the prism 103. The k-vector of the prism 103 is a normalized k-vector across multiple wavelengths of light. The k-vector of the waveguide 300a is the inverse of the normalized k-vector of the prism 103. The waveguide 300a uses diffractive gratings to counteract the refractive dispersion of the prism 103. Compensating for the prism 103 using the waveguide 300a can enhance the quality of the final image and reduce costs associated with more complex prisms.

[0035] Figure 3CThis is a schematic top view of the input coupler 301 of waveguide 300a according to some embodiments. The input period 322 and input orientation 332 of the input coupler 301 are different from those of waveguide 200a. The input coupler 301 has diffraction spectra 117a, 117b, and 117c to compensate for the refractive dispersion of prism 103.

[0036] In waveguide 200a ( Figure 2A In the input coupler 201, the input orientation 332 of the input structure 321 has been changed from the input orientation 232 of the input structure 221. The input orientation 332 has been changed by a compensation angle 371. The compensation angle 371 is the change from the normal vector 231 of waveguide 200a to the normal vector 331 of waveguide 300a. The compensation angle 371 is approximately 1 arcsecond to approximately 5°.

[0037] Although a compensation angle of 371 is shown for the input coupler 301, it is different from that for waveguide 200a ( Figure 2A In comparison, the changes shown by the new normal vector 333 of the pupil expander 303 and the new normal vector 335 of the output coupler 305 are also expressed in compensation angles of approximately 1 arcsecond to approximately 5°.

[0038] k-vector( Use the following equation to calculate:

[0039]

[0040] Where θ0 is the orientation of the input coupler 201 in the waveguide 200a, and The input cycle is 222.

[0041] k-vector of waveguide 300a ( Including compensation .compensate Including grating periodicity compared to uncompensated waveguide 200a and orientation Changes ( The k-vector of waveguide 300a ( Use the following equation to calculate:

[0042]

[0043] Regarding input coupler 201 and input coupler 301, in the above equation, the compensation angle 371 is Δθ, and the input orientation 232 is... And the input orientation 332 is θ0 + Δθ. The compensation angle 371 is approximately 0.002° to approximately 0.005°, for example, approximately 0.003°. The change in input orientation 332 causes the light to pass through waveguide 300a towards pupil expander 303 ( Figure 3AThe diffraction spectra during travel are 117a, 117b, and 117c. To compensate for the refraction of prism 103, the input orientation 232 is adjusted by the compensation angle 371.

[0044] The periodicity of grating structure 321 has been improved from waveguide 200a ( Figure 2A The input period 222 of the input coupler 201 is... ) becomes waveguide 300a ( Figure 3A The input period 322 of the input coupler 301 varies by a compensation increment 373. The compensation increment 373 is defined as the change in the input period 222 of waveguide 200a and the input period 322 of waveguide 300a. The input period 322 is the input period 222 plus the compensation increment 373. The input period 322 corresponds to ( ) in the above equation. The compensation increment 373 is approximately 0.001 nanometers to approximately 1 nanometer (nm). Although the figure shows the input coupler 301 of waveguide 300a, the compensation increment 373 can also be applied to the pupil expander 303, the output coupler 305, or a combination of the input coupler 301, the pupil expander 303, and the output coupler 305.

[0045] The device 100 described herein improves usability by enhancing comfort and reducing the size of the HMD while maintaining the clarity of the image seen by the user's eye. The device 100 incorporates a prism 103, allowing the projector 102 to be aligned within the frame arm 104, and the combination of the prism 103 and waveguide 300a further reduces weight. The waveguide 300a compensates for the dispersion and refraction caused by the prism 103, allowing the image to enter the waveguide 300a as different spectra at different input angles, but exiting the waveguide 300a at approximately the same output angle. Compensation for dispersion via the waveguide 300a reduces the cost of expensive and complex prisms.

[0046] While the foregoing describes embodiments of this disclosure, other and further embodiments may be designed without departing from the basic scope of this disclosure, and the scope of this disclosure is defined by the appended claims.

Claims

1. An augmented reality device, comprising: Projection system, including: A projector, including a main axis, the projector being configured to project an image along the main axis; and A prism, configured to refract the image, the image including a first spectrum, a second spectrum, and a third spectrum; and A waveguide, configured at an angle to the plane formed by the main axis of the projector, the waveguide comprising: An input coupler having an input structure set with an input period and an input orientation, the input coupler being configured to receive a first spectrum, a second spectrum, and a third spectrum at different angles; and An output coupler having an output structure configured with an output period and an output orientation, the output coupler being operable to couple a first spectrum at a first output angle, couple a second spectrum at a second output angle, and couple a third spectrum at a third output angle, wherein the first output angle is approximately equal to the second output angle, and the second output angle is approximately equal to the third output angle.

2. The apparatus of claim 1, wherein the prism is a chromatic aberration prism.

3. The apparatus of claim 1, wherein the input coupler is disposed along the main axis.

4. The apparatus of claim 1, wherein the prism refracts the image with a first k-vector, and the input coupler is configured to diffract the image with a second k-vector, the second k-vector being the reciprocal of the first k-vector.

5. The apparatus of claim 1, wherein the k-vector of the waveguide is greater than 0.

6. The apparatus of claim 1, wherein the k-vector of the waveguide corresponds to the k-vector of the prism.

7. The apparatus of claim 1, wherein the prism is disposed along the main axis and located between the projector and the waveguide.

8. The apparatus of claim 1, wherein the input coupler is configured to receive the first spectrum at a first input angle, receive the second spectrum at a second input angle, and receive the third spectrum at a third input angle, wherein the first input angle is different from the second input angle and the third input angle, and the second input angle is different from the third input angle.

9. The apparatus of claim 1, wherein the input orientation is greater than 0°.

10. The apparatus of claim 1, wherein the output orientation is greater than or less than 90°.

11. An augmented reality device, comprising: Frame arm, coupled to the frame; A projection system, disposed within the frame arm, the projection system comprising: A projector, including a main axis, the projector being configured to project an image along the main axis; and A prism, configured to refract the image, the image including a first spectrum, a second spectrum, and a third spectrum; and A waveguide, coupled to the frame arm, is configured at an angle to the plane formed by the main axis of the projector, the waveguide comprising: An input coupler having an input structure configured with input period and input orientation; and An output coupler has an output structure configured with output period and output orientation.

12. The apparatus of claim 11, wherein the frame arm is aligned along the main axis.

13. The apparatus of claim 11, wherein the projector is disposed within the frame arm.

14. The apparatus of claim 11, wherein the waveguide has a non-zero k-vector.

15. The apparatus of claim 14, wherein the k-vector of the waveguide corresponds to the k-vector of the prism.

16. An augmented reality device, comprising: Projection system, including: A projector, including a main axis, the projector being configured to project an image along the main axis; and A prism, configured to refract the image, the image including a first spectrum, a second spectrum, and a third spectrum; and A waveguide, configured at an angle to the plane formed by the main axis of the projector, the waveguide comprising: An input coupler having an input structure configured with input period and input orientation; A pupil expander having a pupil structure configured with pupil period and pupil orientation; and An output coupler has an output structure configured with output period and output orientation.

17. The apparatus of claim 16, wherein the input orientation is greater than 0°, the pupil orientation is greater than 45°, or the output orientation is greater than 90°.

18. The apparatus of claim 16, wherein the k-vector of the input coupler corresponds to the k-vector of the prism.

19. The apparatus of claim 16, wherein the k-vector of the prism corresponds to the wrap angle.

20. The apparatus of claim 16, wherein the prism is a triangular prism made of a single material.

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