LIDAR systems and methods

1. A LIDAR system comprising:

an emitter configured to emit at least one light beam;

a detector configured for receiving light reflected from surrounding objects; and

a rotatable scanning element configured for receiving the at least one light beam and scanning the at least one light beam out of the system by rotating about an axis of rotation, the rotatable scanning element comprising:

a reflective prism having at least four faces inclined relative to the axis of rotation, and

a transmission element fixedly connected to the reflective prism,

the transmission element having an exterior edge portion extending around the axis of rotation generally in a plane orthogonal to the axis of rotation, the edge portion having a variable thickness about the axis of rotation,

the emitter, the detector, and the rotatable scanning element being arranged such that:

the at least one light beam is incident on and refracted by the transmission element and subsequently incident on one face of the at least four faces of the reflective prism, an angle of incidence of the at least one beam on the face depending on the variable thickness of the transmission element, and

light reflected from surrounding objects being reflected by one of the at least four faces of the reflective prism into the detector.

2. The LIDAR system of claim 1 , wherein the transmission element is described by at least two planes of symmetry, each plane of symmetry transecting the axis of rotation of the reflective prism.

3. The LIDAR system of claim 1 , wherein the transmission element has:

at least two parallel edge portions where a first surface of the transmission element is substantially parallel to a second surface of the transmission element, the first and second surfaces being generally perpendicular to the axis of rotation; and

at least two wedge portions, where at least a portion of the first surface is angled relative to the second surface, the at least two wedge portions being thicker than the at least two parallel portions.

4. The LIDAR system of claim 3 , wherein:

the edge of the transmission element alternates between the parallel edge portions and the wedge portions as the transmission element extends around the axis of rotation; and

the edge smoothly varies in transitions between a given parallel edge portion and an adjacent angled wedge portion.

5. The LIDAR system of claim 1 , wherein the transmission element is selectively rotatable relative to the reflective prism such that the angle of incidence of the at least one beam on the reflective prism is adjustable according to a relative angular orientation between the transmission element and the reflective prism.

6. The LIDAR system of claim 1 , wherein the transmission element is disposed generally between the emitter and the reflective prism along a direction defined by the axis of rotation.

7. The LIDAR system of claim 1 , wherein the system is configured to perform a peripheral scan.

8. The LIDAR system of claim 7 , wherein the system is configured for connecting to a self-driving vehicle on a lateral side thereof.

9. The LIDAR system of claim 1 , wherein the reflective prism has a generally pyramidal form.

10. The LIDAR system of claim 1 , wherein the at least four faces of the reflective prism are skewed relative to the axis of rotation.

11. The LIDAR system of claim 1 , wherein the emitter is arranged to emit the at least one light beam at an angle skewed relative to the axis of rotation of the scanning element.