Lidar system with high-resolution scan pattern
In one embodiment, a lidar system includes a light source configured to emit pulses of light and a scanner configured to scan the emitted pulses of light along a high-resolution scan pattern located within a field of regard of the lidar system. The scanner includes one or more scan mirrors configured to (i) scan the emitted pulses of light along a first scan axis to produce multiple scan lines of the high-resolution scan pattern, where each scan line is associated with multiple pixels, each pixel corresponding to one of the emitted pulses of light and (ii) distribute the scan lines of the high-resolution scan pattern along a second scan axis. The high-resolution scan pattern includes one or more of: interlaced scan lines and interlaced pixels.
1. A high-resolution lidar system configured to scan pulses of light along a high-resolution scan pattern with N-fold interlaced scan lines, the lidar system comprising:
a light source configured to emit pulses of light;
a scanner configured to scan the emitted pulses of light along a high-resolution scan pattern located within a field of regard of the lidar system, wherein the scanner comprises one or more scan mirrors configured to:
scan the emitted pulses of light along a first scan axis to produce a plurality of scan lines of the high-resolution scan pattern, wherein each scan line is associated with a plurality of pixels, each pixel corresponding to one of the emitted pulses of light; and
distribute the scan lines of the high-resolution scan pattern along a second scan axis,
wherein the high-resolution scan pattern comprises interlaced scan with N-fold interlacing, wherein:
the scan lines of the high-resolution scan pattern comprise N sets of scan lines, wherein N is a positive integer greater than or equal to 2;
the N sets of scan lines are scanned in sequence from a first set of scan lines to a N-th set of scan lines;
an adjacent pair of scan lines from the first set of scan lines comprises a first scan line and a subsequent scan line separated by a scan-line separation angle ΔΦ along the second scan axis, wherein (N−1) other scan lines are located between the first and the subsequent scan lines, the (N−1) other scan lines comprising one scan line from each of the N sets of scan lines, excluding the first set of scan lines; and
a k-th scan line of the (N−1) other scan lines is offset from the first scan line along the second scan axis by an angular amount [((k−1)×n/N) mod 1]×ΔΦ, wherein k is an integer incremented from 2 to N, n is a fixed integer from 1 to (N−1), the k-th scan line is part of a k-th set of scan lines, and the k-th set of scan lines is scanned after a (k−1)-th set of scan lines; and
a receiver configured to detect a received pulse of light, the received pulse of light comprising a portion of one of the emitted pulses of light scattered by a target located a distance from the lidar system.
2. The lidar system of claim 1 , wherein the lidar system further comprises a processor configured to produce a partial point cloud comprising pixels associated with from 1 to (N−1) most recently scanned sets of scan lines of the N sets of scan lines.
3. The lidar system of claim 1 , wherein the lidar system further comprises a processor configured to produce point clouds at a frame rate of N×F/r, wherein:
each point cloud comprises pixels associated with each of the N sets of scan lines;
F is a full frame rate, wherein a reciprocal of the full frame rate, 1/F, corresponds to a time interval to scan the N sets of scan lines; and
r is an integer from 1 to N.
4. The lidar system of claim 3 , wherein:
the N sets of scan lines comprise (i) r sets of scan lines and (ii) (N−r) sets of scan lines;
a previous point cloud comprises (i) older pixels associated with the r sets of scan lines and (ii) more recent pixels associated with the (N−r) sets of scan lines, the more recent pixels captured after the older pixels; and
a subsequent point cloud produced after the previous point cloud comprises (i) newer pixels associated with the r sets of scan lines and (ii) the more recent pixels associated with the (N−r) sets of scan lines, the newer pixels captured after the more recent pixels.
5. The lidar system of claim 1 , wherein:
N equals 8 so that the interlaced scan lines are 8-fold interlaced;
n equals 5; and
the (N−1) other scan lines comprise seven scan lines, the seven scan lines comprising:
a second scan line from a second set of scan lines, the second scan line scanned after the first set of scan lines and offset from the first scan line along the second scan axis by an angular amount (⅝)×ΔΦ;
a third scan line from a third set of scan lines, the third scan line scanned after the second set of scan lines and offset from the first scan line along the second scan axis by an angular amount (¼)×ΔΦ;
a fourth scan line from a fourth set of scan lines, the fourth scan line scanned after the third set of scan lines and offset from the first scan line along the second scan axis by an angular amount (⅞)×ΔΦ;
a fifth scan line from a fifth set of scan lines, the fifth scan line scanned after the fourth set of scan lines and offset from the first scan line along the second scan axis by an angular amount (½)×ΔΦ;
a sixth scan line from a sixth set of scan lines, the sixth scan line scanned after the fifth set of scan lines and offset from the first scan line along the second scan axis by an angular amount (⅛)×ΔΦ;
a seventh scan line from a seventh set of scan lines, the seventh scan line scanned after the sixth set of scan lines and offset from the first scan line along the second scan axis by an angular amount (¾)×ΔΦ; and
an eighth scan line from an eighth set of scan lines, the eighth scan line scanned after the seventh set of scan lines and offset from the first scan line along the second scan axis by an angular amount (⅜)×ΔΦ.
6. The lidar system of claim 1 , wherein distributing the scan lines along the second scan axis comprises applying one of N different temporal offsets to each set of scan lines.
7. The lidar system of claim 1 , wherein distributing the scan lines along the second scan axis comprises applying one of N different angular offsets along the second scan axis to each set of scan lines.
8. The lidar system of claim 1 , wherein the high-resolution scan pattern comprises interlaced scan lines that are interlaced using a V-scan wherein:
the first set of scan lines is distributed along the second scan axis in a first direction; and
a second set of scan lines of the N sets of scan lines is distributed along the second scan axis in a second direction opposite the first direction, wherein the second set of scan lines is distributed after the first set of scan lines.
9. The lidar system of claim 8 , wherein each of the first set of scan lines has a negative incline angle, and each of the second set of scan lines has a positive incline angle.
10. The lidar system of claim 1 , wherein the high-resolution scan pattern further comprises interlaced pixels, wherein:
adjacent pixels associated with each scan line of the plurality of scan lines are separated from one another along the first scan axis by a pixel-spacing angle ΔΘ; and
pixels associated with two adjacent scan lines are offset along the first scan axis with respect to one another by a pixel-offset angle d×ΔΘ, wherein d is a number between 0 and 1.
11. The lidar system of claim 1 , wherein the high-resolution scan pattern further comprises interlaced pixels with M-fold sequential interlacing, wherein:
M is a positive integer greater than or equal to 2;
adjacent pixels associated with each scan line of the plurality of scan lines are separated from one another along the first scan axis by a pixel-spacing angle ΔΘ; and
pixels associated with two adjacent scan lines are offset along the first scan axis with respect to one another by a pixel-offset angle ΔΘ/M.
12. The lidar system of claim 1 , wherein the high-resolution scan pattern further comprises interlaced pixels with non-sequential interlacing, wherein:
adjacent pixels associated with each scan line of the plurality of scan lines are separated from one another along the first scan axis by a pixel-spacing angle ΔΘ;
the scan lines of the high-resolution scan pattern comprise a m-th scan line, a (m+1)-th scan line adjacent to the m-th scan line, and a (m+2)-th scan line adjacent to the (m+1)-th scan line, wherein the (m+1)-th scan line is located between the m-th and (m+2)-th scan lines, wherein m is a positive integer;
pixels associated with the second (m+1)-th scan line are offset along the first scan axis with respect to pixels associated with the m-th scan line by a pixel-offset angle d 1 ×ΔΦ, wherein d 1 is a number between 0 and 1; and
pixels associated with the (m+2)-th scan line are offset along the first scan axis with respect to the pixels associated with the m-th scan line by a pixel-offset angle d 2 ×ΔΦ, wherein d 2 is a number between 0 and d 1 .
13. The lidar system of claim 1 , wherein the high-resolution scan pattern further comprises interlaced pixels with M-fold interlacing, wherein:
M is a positive integer greater than or equal to 2; and
the light source is further configured to apply a temporal offset of M different temporal offsets to a portion of the emitted pulses of light at a beginning of each scan line.
14. The lidar system of claim 1 , wherein the high-resolution scan pattern further comprises interlaced pixels with M-fold interlacing, wherein:
M is a positive integer greater than or equal to 2; and
scanning the emitted pulses of light along the first scan axis to produce the plurality of scan lines comprises applying one of M different angular offsets along the first scan axis to each scan line.
15. The lidar system of claim 1 , wherein the lidar system is a first lidar system that is part of a sensor system that further comprises a second lidar system, wherein the first and second lidar systems are configured to scan synchronously, wherein a plurality of the scan lines or pixels produced by the first lidar system is interlaced with a plurality of scan lines or pixels produced by the second lidar system.
16. The lidar system of claim 1 , wherein the lidar system further comprises a processor configured to:
determine the distance from the lidar system to the target based at least in part on a round-trip time for the portion of the emitted pulse of light to travel to the target and back to the lidar system; and
increase, in response to determining that the distance to the target exceeds a particular threshold distance, a density of scan lines or pixels in a region of the field of regard associated with the target.
17. The lidar system of claim 1 , wherein:
each scan line is oriented substantially parallel to the first scan axis; and
the second scan axis is substantially orthogonal to the first scan axis.
18. The lidar system of claim 1 , wherein the scanner comprises:
a first scan mirror comprising a polygon mirror, the polygon mirror configured to scan the emitted pulses of light along the first scan axis to produce the plurality of scan lines; and
a second scan mirror configured to distribute the scan lines along the second scan axis.
19. The lidar system of claim 1 , wherein each of the one or more scan mirrors is mechanically driven by a galvanometer scanner, a synchronous electric motor, a microelectromechanical systems (MEMS) device, a resonant scanner, or a voice coil motor.
20. The lidar system of claim 1 , further comprising a processor configured to determine the distance from the lidar system to the target based at least in part on a round-trip time for the portion of the emitted pulse of light to travel to the target and back to the lidar system.
21. The lidar system of claim 1 , wherein the emitted pulses of light have optical characteristics comprising:
a wavelength between 900 nanometers and 1700 nanometers;
a pulse energy between 0.1 μJ and 100 μJ;
a pulse repetition frequency between 80 kHz and 10 MHz; and
a pulse duration between 1 ns and 100 ns.
22. The lidar system of claim 1 , wherein the light source comprises a direct-emitter laser diode configured to produce the emitted pulses of light.
23. The lidar system of claim 1 , wherein the light source comprises:
a seed laser diode configured to produce seed light; and
a semiconductor optical amplifier (SOA) configured to amplify the seed light to produce the emitted pulses of light.
24. The lidar system of claim 1 , wherein the lidar system is part of a vehicle comprising an advanced driver assistance system (ADAS) configured to assist a driver of the vehicle in operating the vehicle, wherein the lidar system is configured to provide information about a surrounding environment of the vehicle to the ADAS.
25. The lidar system of claim 1 , wherein the lidar system is part of an autonomous vehicle comprising an autonomous-vehicle driving system configured to guide the autonomous vehicle through a surrounding environment toward a destination, wherein the lidar system is configured to provide information about the surrounding environment to the autonomous-vehicle driving system.
26. A method for scanning pulses of light along a high-resolution scan pattern with N-fold interlaced scan lines, the method comprising:
emitting, by a light source of a lidar system, pulses of light;
scanning, by a scanner of the lidar system, the emitted pulses of light along a high-resolution scan pattern located within a field of regard of the lidar system, comprising:
scanning the emitted pulses of light along a first scan axis to produce a plurality of scan lines of the high-resolution scan pattern, wherein each scan line is associated with a plurality of pixels, each pixel corresponding to one of the emitted pulses of light; and
distributing the scan lines of the high-resolution scan pattern along a second scan axis,
wherein the high-resolution scan pattern comprises interlaced scan lines and with N-fold interlacing, wherein:
the scan lines of the high-resolution scan pattern comprise N sets of scan lines, wherein N is a positive integer greater than or equal to 2;
the N sets of scan lines are scanned in sequence from a first set of scan lines to a N-th set of scan lines;
an adjacent pair of scan lines from the first set of scan lines comprises a first scan line and a subsequent scan line separated by a scan-line separation angle ΔΦ along the second scan axis, wherein (N−1) other scan lines are located between the first and the subsequent scan lines, the (N−1) other scan lines comprising one scan line from each of the N sets of scan lines, excluding the first set of scan lines; and
a k-th scan line of the (N−1) other scan lines is offset from the first scan line along the second scan axis by an angular amount [((k−1)×n/N) mod 1]×ΔΦ, wherein k is an integer incremented from 2 to N, n is a fixed integer from 1 to (N−1), the k-th scan line is part of a k-th set of scan lines, and the k-th set of scan lines is scanned after a (k−1)-th set of scan lines; and
detecting, by a receiver of the lidar system, a received pulse of light, the received pulse of light comprising a portion of one of the emitted pulses of light scattered by a target located a distance from the lidar system.