Ultrasonic vibrations on a window in a lidar system
To clear the line-of-sight (LOS) on a window in a lidar system within a vehicle, ultrasonic transducers are physically attached to the interior surface of the window to remove debris. When debris is detected at the window, the ultrasonic transducers are directed to vibrate at an ultrasonic frequency thereby generating an ultrasonic wave which causes the debris to bounce off the window. In some scenarios, the ultrasonic transducers vibrate with a particular phase shift to generate a travelling wave that causes the debris to sweep across the window. Additionally, windshield wipers, spray from a nozzle, and/or a hydrophobic or oleophobic coating may be used in combination with the ultrasonic transducers to remove the debris from the window.
1. A lidar system comprising:
a light source configured to emit light pulses;
a scanner configured to scan the emitted light pulses across a field of regard of the lidar system;
a receiver configured to detect light from some of the emitted light pulses scattered by one or more remote targets to generate respective pixels;
a window having an exterior-facing surface, the window arranged in front of the light source, the scanner, and the receiver, wherein the emitted light pulses are transmitted through the window toward the one or more remote targets, and the light from the emitted light pulses that is scattered by the one or more remote targets is transmitted through the window and detected at the receiver;
one or more ultrasonic transducers attached to the window and configured to cause vibration at the window to remove debris from the exterior-facing surface of the window; and
a controller configured to detect the debris on the window and transmit a control signal to the one or more ultrasonic transducers to vibrate, wherein to detect the debris on the window the controller is configured to:
receive an indication from the receiver of at least a portion of a duration of a return light pulse;
compare the indication of the at least a portion of the duration to a threshold duration; and
in response to determining that the at least a portion of the duration exceeds the threshold duration, identify debris on the window.
2. The lidar system of claim 1 , wherein the controller is further configured to detect the debris on the window by receiving an indication of debris from a rain sensor within a vehicle in which the lidar system operates.
3. The lidar system of claim 1 , wherein to detect the debris on the window the controller is further configured to:
receive, from a positioning sensor, an indication of the geolocation of a vehicle in which the lidar system operates;
transmit a request to a weather data service for current weather data for the received geolocation;
receive, from the weather data service, a response to the request indicating rain; and
detect debris on the window based on the indication of rain.
4. The lidar system of claim 1 , wherein the exterior-facing surface of the window is provided with a hydrophobic or oleophobic layer.
5. The lidar system of claim 1 , wherein the one or more ultrasonic transducers include a plurality of ultrasonic transducers configured to vibrate with a particular phase shift to generate a travelling ultrasonic wave, thereby causing the debris to sweep across the exterior-facing surface of the window.
6. The lidar system of claim 1 , wherein:
the window is an external window; and
the lidar system further comprises an internal window arranged between the external window and the light source, scanner, and receiver.
7. The lidar system of claim 6 , wherein the internal window is configured to provide an airtight or watertight seal for the lidar system.
8. The lidar system of claim 1 , wherein the debris comprises one or more of water, fog, and dirt.
9. The lidar system of claim 1 , further comprising a windshield wiper and a nozzle configured to spray water or cleaner, wherein the wiper and nozzle are configured, in combination with the one or more ultrasonic transducers, to remove the debris from the exterior-facing surface of the window.
10. The lidar system of claim 1 , wherein the controller is further configured to generate an alert in response to the debris remaining on the window, the alert indicating that the debris remains on the surface of the window.
11. The lidar system of claim 1 , wherein the controller is further configured to activate the one or more ultrasonic transducers according to a particular schedule.
12. A lidar system comprising:
a light source configured to emit light pulses;
a scanner configured to scan the emitted light pulses across a field of regard of the lidar system;
a receiver configured to detect light from some of the emitted light pulses scattered by one or more remote targets to generate respective pixels;
a window having an exterior-facing surface, the window arranged in front of the light source, the scanner, and the receiver, wherein the emitted light pulses are transmitted through the window toward the one or more remote targets, and the light from the emitted light pulses that is scattered by the one or more remote targets is transmitted through the window and detected at the receiver; and
one or more ultrasonic transducers attached to the window and configured to cause vibration at the window to remove debris from the exterior-facing surface of the window; and
a controller configured to detect the debris on the window and transmit a control signal to the one or more ultrasonic transducers to vibrate, wherein the controller is further configured to:
detect a size or amount of the debris on the window; and
transmit a control signal to the one or more ultrasonic transducers indicating an intensity at which to vibrate, wherein the intensity is selected based on the size or amount of the debris.
13. A method for removing debris from a window of a lidar system, the method comprising:
emitting light pulses by a light source of a lidar system;
scanning, by a scanner of the lidar system the emitted light pulses across a field of regard of the lidar system;
detecting, by a receiver of the lidar system, light from some of the emitted light pulses scattered by one or more remote targets to generate respective pixels;
detecting debris on a window having an exterior-facing surface arranged in front of the light source, the scanner, and the receiver, wherein the emitted light pulses are transmitted through the window toward the one or more remote targets and the light from the emitted light pulses that is scattered by the one or more remote targets is transmitted through the window and detected at the receiver, and wherein detecting the debris on the window includes:
receiving an indication from the receiver of at least a portion of a duration of a return light pulse;
comparing the indication of the at least a portion of the duration to a threshold duration; and
in response to determining that the at least a portion of the duration exceeds the threshold duration, identifying debris on the window; and
causing one or more ultrasonic transducers attached to the window to vibrate in response to detecting the debris on the window to remove the debris from the exterior-facing surface of the window.
14. A method for removing debris from a window of a lidar system, the method comprising:
emitting light pulses by a light source of a lidar system;
scanning, by a scanner of the lidar system the emitted light pulses across a field of regard of the lidar system;
detecting, by a receiver of the lidar system, light from some of the emitted light pulses scattered by one or more remote targets to generate respective pixels;
detecting debris on a window having an exterior-facing surface arranged in front of the light source, the scanner, and the receiver, wherein the emitted light pulses are transmitted through the window toward the one or more remote targets and the light from the emitted light pulses that is scattered by the one or more remote targets is transmitted through the window and detected at the receiver, wherein detecting the debris on the window includes:
not receiving an indication from the receiver of a return light pulse corresponding to a same angle relative to a forward-facing direction of a vehicle in which the lidar system operates for more than a threshold number of frames while the vehicle is moving; and
detecting debris on the window at the angle relative to the forward-facing direction of the vehicle; and
causing one or more ultrasonic transducers attached to the window to vibrate in response to detecting the debris on the window to remove the debris from the exterior-facing surface of the window.
15. The lidar system of claim 12 , wherein the exterior-facing surface of the window is provided with a hydrophobic or oleophobic layer.
16. The lidar system of claim 12 , wherein the one or more ultrasonic transducers include a plurality of ultrasonic transducers configured to vibrate with a particular phase shift to generate a travelling ultrasonic wave, thereby causing the debris to sweep across the exterior-facing surface of the window.
17. The lidar system of claim 12 , wherein:
the window is an external window; and
the lidar system further comprises an internal window arranged between the external window and the light source, scanner, and receiver.
18. The lidar system of claim 12 , wherein the debris comprises one or more of water, fog, and dirt.
19. The method of claim 13 , wherein the debris comprises one or more of water, fog, and dirt.