Techniques for alignment of target and local oscillator beams to photodiode detector

A light detection and ranging (LiDAR) system, comprising:

• a processor;
• and
• a memory to store instructions that, when executed by the processor, cause the LiDAR system to:
• emit an optical beam by an optical source;
• generate a local oscillator (LO) signal based on the optical beam;
• place an optical lens in front of a photodetector at a first predetermined position;
• move the optical lens to a plurality of Z-positions along a direction of an optical axis, the plurality of Z-positions corresponding to a plurality of parameter values of the LO signal,
• for each of the plurality of Z-positions,
• move the optical lens perpendicular to the direction of the optical axis to a set of lateral positions for a Z-position;
• receive a set of values of the LO signal at the set of lateral positions by the photodetector;
• generate a fitting function based on the set of values of the LO signal;
• and
• determine a parameter value of the LO signal for the Z-position;
• determine an initial Z-axis position of the optical lens by selecting a Z-position from the plurality of Z-positions based on the plurality of parameter values;
• determine a final Z-position of the optical lens by adding an offset to the initial Z-axis position;
• and
• align the optical lens based on the final Z-position to improve an accuracy of at least one of range or velocity information of a target.

A light detection and ranging (LiDAR) system, comprising:

• an optical source to emit an optical beam;
• a local oscillator (LO) to generate an LO signal based on the optical beam;
• a photodetector to receive the LO signal and a target return signal;
• a circuitry;
• and
• a memory to store instructions that, when executed by the circuitry, cause the LiDAR system to:
• place an optical lens in front of the photodetector at a first predetermined position;
• move the optical lens to a plurality of Z-positions along a direction of an optical axis, the plurality of Z-positions corresponding to a plurality of parameter values of the LO signal,
• for each of the plurality of Z-positions,
• move the optical lens perpendicular to the direction of the optical axis to a set of lateral positions for a Z-position;
• receive a set of values of the LO signal at the set of lateral positions by the photodetector;
• generate a fitting function based on the set of values of the LO signal;
• and
• determine a parameter value of the LO signal for the Z-position;
• determine an initial Z-axis position of the optical lens by selecting a Z-position from the plurality of Z-positions based on the plurality of parameter values;
• determine a final Z-position of the optical lens by adding an offset to the initial Z-axis position;
• and
• align the optical lens based on the final Z-position to improve an accuracy of at least one of range or velocity information of a target.