Thin waveguide imager
A device for providing a 1D line of an image is disclosed. The device is based on a thin slab waveguide coupled to a beam redirecting device such as a tiltable mirror MEMS scanner, a waveguide-based phased array, or a waveguide-based optical switch switching image light between waveguides of a waveguide array coupled to a collimating element formed in the low-mode slab waveguide. The image may be formed by scanning a collimated beam propagating in the slab waveguide, or by forming the 1D singular distribution of brightness at a same time. The device may be used in a near-eye display for forming a 2D image in angular domain.
1. A device for providing a line of an image in angular domain, the device comprising a low-mode waveguide comprising:
an in-coupler for coupling image light into the low-mode waveguide;
a 1×N splitter for splitting the image light coupled by the in-coupler into N linear waveguides;
N phase shifters each coupled to a particular one of the N linear waveguides for delaying image light portions propagating therein by a controllable amount;
an array of N linear waveguide emitters each coupled to a particular one of the N phase shifters for emitting the image light portions delayed thereby; and
a slab waveguide portion coupled to the array of N linear waveguide emitters for propagating therein the delayed image light portions emitted by corresponding emitters of the array of N linear waveguide emitters, wherein N is an integer.
2. The device of claim 1 , wherein the slab waveguide portion comprises a singlemode slab waveguide.
3. The device of claim 1 , wherein the slab waveguide portion comprises a few-mode slab waveguide supporting no more than 10 lateral modes of propagation.
4. The device of claim 1 , wherein the 1×N splitter comprises a binary tree of tunable Mach-Zehnder interferometers for providing a controllable distribution of optical power of the image light between the N linear waveguides.
5. The device of claim 1 , wherein the slab waveguide portion further comprises a field of view (FOV) expander in the slab waveguide portion, the FOV expander comprising a tunable cladding portion evanescently coupled to a core of the slab waveguide portion and shaped to deviate light propagated in the core of the slab waveguide portion by a controllable amount.
6. The device of claim 5 , wherein the tunable cladding portion comprises an array of triangular-shaped liquid crystal cladding portions, the array extending laterally w.r.t. an optical path of the image light in the core of the slab waveguide portion, wherein at least some triangular-shaped liquid crystal cladding portions have a side extending at an acute angle w.r.t. the optical path.
7. The device of claim 1 , wherein the slab waveguide portion further comprises a hologram configured to reflect a collimated beam portion of the image light at a plurality of locations along an optical path of the collimated beam portion in the hologram, such that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impinging onto the hologram.
8. A device for providing a line of an image in angular domain, the device comprising a low-mode waveguide comprising:
an in-coupler for coupling image light into the low-mode waveguide;
a tunable 1×N splitter for distributing optical power of the image light coupled by the in-coupler between linear waveguides of an array of N linear waveguides; and
a slab waveguide portion comprising:
a collimating element for converting a lateral position of a linear waveguide of the array of n linear waveguides into a beam angle of an image light portion propagated in the linear waveguide of the array of n linear waveguides, wherein Nis an integer; and
a field of view (FOV) expander comprising a tunable cladding portion evanescently coupled to a core of the slab waveguide portion and shaped to deviate light propagated in the core of the slab waveguide portion by a controllable amount.
9. The device of claim 8 , wherein the slab waveguide portion comprises a singlemode slab waveguide.
10. The device of claim 8 , wherein the slab waveguide portion comprises a few-mode slab waveguide supporting no more than 10 lateral modes of propagation.
11. The device of claim 8 , wherein the 1×N splitter comprises a binary tree of Mach-Zehnder switches for switching the image light between the n linear waveguides.
12. The device of claim 8 , wherein the tunable cladding portion comprises an array of triangular-shaped liquid crystal cladding portions, the array extending laterally w.r.t. an optical path of the image light in the core of the slab waveguide portion, wherein at least some triangular-shaped liquid crystal cladding portions have a side extending at an acute angle w.r.t. the optical path.
13. A device for providing a line of an image in angular domain, the device comprising a low-mode waveguide comprising:
an in-coupler for coupling image light into the low-mode waveguide;
a tunable 1×N splitter for distributing optical power of the image light coupled by the in-coupler between linear waveguides of an array of N linear waveguides; and
a slab waveguide portion comprising:
a collimating element for converting a lateral position of a linear waveguide of the array of n linear waveguides into a beam angle of an image light portion propagated in the linear waveguide of the array of n linear waveguides, wherein Nis an integer; and
a hologram configured to reflect a collimated beam portion of the image light at a plurality of locations along an optical path of the collimated beam portion in the hologram, such that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impinging onto the hologram.
14. A device for providing a line of an image in angular domain, the device comprising:
a microelectromechanical system (MEMS) beam scanner comprising a tiltable reflector for scanning image light in a first plane;
a low-mode slab waveguide in the first plane, for propagating the image light scanned by the MEMS beam scanner; and
a coupler for receiving the image light scanned by the MEMS beam scanner and coupling the image light to an edge of the low-mode slab waveguide.
15. The device of claim 14 , wherein the low-mode slab waveguide is a singlemode slab waveguide.
16. The device of claim 14 , wherein the low-mode slab waveguide is a few-mode slab waveguide supporting no more than 10 lateral modes of propagation.
17. The device of claim 14 , wherein the low-mode slab waveguide further comprises a field of view (FOV) expander in the slab waveguide portion, the FOV expander comprising a tunable cladding portion evanescently coupled to a core of the low-mode slab waveguide and shaped to deviate light propagated in the core of the slab waveguide portion by a controllable amount.
18. The device of claim 17 , wherein the tunable cladding portion comprises an array of triangular-shaped liquid crystal cladding portions, the array extending laterally w.r.t. an optical path of the image light in the core of the low-mode slab waveguide, wherein at least some triangular-shaped liquid crystal cladding portions have a side extending at an acute angle w.r.t. the optical path.
19. The device of claim 14 , wherein the low-mode slab waveguide further comprises a hologram configured to reflect a collimated beam portion of the image light at a plurality of locations along an optical path of the collimated beam portion in the hologram, such that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impinging onto the hologram.