LIDAR scanning with expanded scan angle
In described examples of a system for outputting a patterned light beam, the system includes: an illumination source; a positive optical element positioned to receive light from the illumination source and to output converging light; a reflective element positioned to receive the converging light from the positive optical element, the reflective element configured to reflect the converging light to form a scan beam; and a negative optical element to receive the scan beam from the reflective element, the negative optical element configured to output the scan beam to a field of view.
1. A method comprising:
obtaining, by at least one processor, an image pattern sequence;
computing, by the at least one processor, a sequence of diffractive images corresponding to the image pattern sequence;
correcting, by the at least one processor, the sequence of diffractive images to compensate for distortion by a spatial light modulator, to produce a sequence of corrected diffractive images;
mapping, by the at least one processor, the sequence of corrected diffractive images to produce a mapped sequence of diffraction patterns;
setting, by the spatial light modulator, elements of the spatial light modulator to the mapped sequence of diffraction patterns; and
for the mapped sequence of quantized diffraction patterns displayed using the spatial light modulator, illuminating, by a light source, the spatial light modulator to produce the image pattern sequence.
2. The method of claim 1 , wherein computing the sequence of diffractive images corresponding to the image pattern sequence comprises applying an inverse Fourier transform to image patterns in the image pattern sequence.
3. The method of claim 1 , further comprising:
storing the sequence of corrected diffractive images in a memory.
4. The method of claim 3 , further comprising:
retrieving the sequence of corrected diffractive images from the memory; and
using the spatial light modulator, displaying the retrieved sequence of corrected diffractive images.
5. The method of claim 1 , wherein correcting the sequence of diffractive images further comprises computing a two dimensional polynomial including a correction factor.
6. The method of claim 5 , wherein computing the two dimensional polynomial includes computing:
H ( x,y )= A exp( j φ( x,y )),
where H(x, y) is the corrected diffractive images in two dimensions, and
jφ(x, y) is a correction factor in two dimensions for each element of the spatial light modulator at a position x, y.
7. The method of claim 1 , wherein the spatial light modulator is a digital micromirror device, a phase light modulator, or a liquid crystal on silicon device.
8. The method of claim 1 , further comprising quantizing the sequence of corrected diffractive images.
9. A method comprising:
determining, by at least one processor, an image pattern sequence;
computing, by the at least one processor, a sequence of diffractive images corresponding to the image pattern sequence;
correcting, by the at least one processor, the sequence of diffractive images to compensate for distortion by a spatial light modulator, to produce a sequence of corrected diffractive images;
mapping, by the at least one processor, the sequence of corrected diffractive images to produce a mapped sequence of diffraction patterns; and
storing, in memory, the mapped sequence of diffraction images.
10. The method of claim 9 , wherein computing the sequence of diffractive images corresponding to the image pattern sequence comprises applying an inverse Fourier transform to image patterns in the image pattern sequence.
11. The method of claim 9 , further comprising quantizing the sequence of corrected diffractive images.
12. The method of claim 9 , wherein correcting the sequence of diffractive images further comprises computing a two dimensional polynomial including a correction factor.
13. The method of claim 12 , wherein computing the two dimensional polynomial includes computing:
H ( x,y )= A exp( j φ( x,y )),
where H(x, y) is the corrected diffractive images in two dimensions, and
jφ(x, y) is a correction factor in two dimensions for each element of the spatial light modulator at a position x, y.
14. A system comprising:
a spatial light modulator;
a light source optically coupled to the spatial light modulator; and
at least one processor coupled to the spatial light modulator, the at least one processor configured to:
obtain an image pattern sequence;
compute a sequence of diffractive images corresponding to the image pattern sequence;
correct the sequence of diffractive images to compensate for distortion by a spatial light modulator, to produce a sequence of corrected diffractive images;
map the sequence of corrected diffractive images to produce a mapped sequence of diffraction patterns; and
instruct the spatial light modulator to display the mapped sequence of diffraction patterns;
wherein the spatial light modulator is configured to set elements based on the mapped sequence of diffraction patterns; and
wherein the light source is configured to illuminate the spatial light modulator to produce the image pattern sequence.
15. The system of claim 14 , wherein computing the sequence of diffractive images corresponding to the image pattern sequence comprises applying an inverse Fourier transform to image patterns in the image pattern sequence.
16. The system of claim 14 , wherein correcting the sequence of diffractive images further comprises computing a two dimensional polynomial including a correction factor.
17. The system of claim 16 , wherein computing the two dimensional polynomial includes computing:
H ( x,y )= A exp( j φ( x,y )),
where H(x, y) is the corrected diffractive images in two dimensions, and
jφ(x, y) is a correction factor in two dimensions for each element of the spatial light modulator at a position x, y.
18. The system of claim 14 , wherein the spatial light modulator is a digital micromirror device, a phase light modulator, or a liquid crystal on silicon device.
19. The system of claim 14 , wherein the at least one processor is further configured to quantize the sequence of corrected diffractive images.
20. The system of claim 14 , further comprising memory coupled to the at least one processor, wherein obtaining the image pattern sequence comprises retrieving the image pattern sequence from the memory.