1. A light detection and ranging system comprising: an emitter which produces an outgoing pulse sequence of coherent collimated light; a mirror system having a scanning mirror that is positioned to deflect the outgoing pulse sequence; a compensation mirror positioned to further deflect the outgoing pulse sequence after it is deflected by the scanning mirror, the compensation mirror having a surface with a first curvature at an edge of the compensation mirror that is different from a second curvature at a center of the compensation mirror; a detector collocated with the emitter and aimed to detect an incoming pulse sequence that is a reflection of the outgoing pulse sequence; and electronic circuitry that is coupled to communicate with the emitter and the detector and to control the scanning mirror, so that the outgoing pulse sequence scans a scene and the electronic circuitry computes a radial distance for each pair of outgoing and incoming pulses and uses the computed radial distance to provide a scanned 3D depth map of objects in the scene.