Optical spread spectrum detection and ranging
Example implementations may relate to an obstacle detection system. In particular, an example device may include a light emitter, a line-image sensor, and a controller that are mounted on a rotatable component. In an example embodiment, the line-image sensor may receive light signals emitted from the light emitter. The controller may be communicatively coupled to the light emitter and line-image sensor and configured to determine a multipath signal based on the time of flight of the light signal and the position along the line-image sensor at which the line-image sensor received the given reflected light signal.
1. A system comprising:
a light emitter configured to emit a light signal;
a line-image sensor configured to receive reflected light signals at a plurality of positions along the line-image sensor; and
a controller communicatively coupled to the light emitter and the line-image sensor, the controller being configured to determine whether a given reflected light signal received at the line-image sensor is a multi-path signal based on (i) an amount of time between emission of the light signal from the light emitter and reception at the line-image sensor of the given reflected light signal, and (ii) a position along the line-image sensor at which the line-image sensor received the given reflected light signal;
wherein the controller is configured to determine that the given reflected light signal is a multi-path signal by:
determining the amount of time between emission of the given light signal from the light emitter and reception at the line-image sensor of the given reflected light signal;
based on the determined amount of time, identifying a target window of positions along the line-image sensor;
determining that the line-image sensor received the given reflected light signal at a position outside of the target window of positions;
wherein the line-image sensor has a proximate end and a distal end, the light emitter being positioned nearer to the proximate end than the distal end, and
wherein the target window of positions is located along the line-image sensor at a distance from the proximate end, the distance being proportionate to the determined amount of time.
2. The system of claim 1 ,
wherein the target window of time is a length of time subsequent to emission of the light signal, the length of time being proportionate to a distance from the proximate end of the line-image sensor to the determined position along the line-image sensor at which the line-image sensor received the given reflected light signal.
3. A method comprising:
emitting a light signal from a light emitter;
receiving a reflection of the emitted light signal, wherein the reflection of the emitted light signal is received at a position along a line-image sensor; and
determining whether the reflection of the emitted light signal received at the line-image sensor is a multi-path signal based on (i) an amount of time between emission of the light signal and reception at the line-image sensor of the reflection of the emitted light signal, and (ii) the position along the line-image sensor at which the line-image sensor received the reflection of the emitted light signal
wherein the light signal comprises a plurality of light signals that reflect off of an obstacle and return to the line-image sensor as reflected light signals; and further comprising:
estimating a distance from the line-image sensor to the obstacle based on a set of reflected light signals, wherein signals determined to be multi path signals are excluded from the set
rotating the light emitter;
wherein the light emitter is further configured to emit light signals in accordance with a particular pseudo-noise (PN) code, and wherein the method further comprises:
correlating a received plurality of lights signals to the particular PN code,
and
controlling a shutter to filter out reflected light signals emitted in accordance with a PN code other than the particular PN code.
4. A collision avoidance system, comprising:
an inertial measurement unit configured to measure rotation and acceleration of a vehicle about one or more axes of the vehicle;
an obstacle detection unit comprising:
a light emitter configured to emit a light signal;
a line-image sensor configured to receive reflected light signals at a plurality of positions along the line-image sensor; and
a controller communicatively coupled to the light emitter and the line-image sensor, the controller being configured to determine whether a given reflected light signal received at the line-image sensor is a multi-path signal based on (i) an amount of time between emission of the light signal from the light emitter and reception at the line-image sensor of the given reflected light signal, and (ii) a position along the line-image sensor at which the line-image sensor received the given reflected light signal; and
a control system, wherein the control system is communicatively coupled with the inertial measurement unit and the obstacle detection unit, and wherein the control system is configured to control the vehicle to avoid detected objects by sending control outputs to the vehicle based on information received from the inertial measurement unit and the obstacle detection unit;
wherein the light emitter is further configured to emit a plurality of light signals that reflect off of an obstacle and return to the line-image sensor as the reflected light signals, and wherein the controller is further configured to estimate a distance from the line-image sensor to the obstacle based on a set of reflected light signals, wherein signals determined to be multi path signals are excluded from the set.