Use of conjugate focal plane to generate target information in a LIDAR system

A method in a light detection and ranging (LIDAR) system, comprising:

• focusing an optical beam at a first focal plane;
• generating a local oscillator (LO) signal by partially reflecting a portion of the optical beam from a partially reflecting surface proximate to the first focal plane and reflecting the LO signal back through a first lens system, wherein a transmitted portion of the optical beam is directed toward a scanned target environment;
• focusing the LO signal and a target return signal at a second focal plane conjugate to the first focal plane;
• and
• mixing the LO signal with the target return signal in a photodetector proximate to the second focal plane to generate target information.

A non-transitory computer-readable medium storing instructions, that when executed by a processor of a light detection and ranging (LIDAR) system, cause the LIDAR system to:

• focus an optical beam at a first focal plane;
• generate a local oscillator (LO) signal by partially reflecting a portion of the optical beam from a partially reflecting surface proximate to the first focal plane and reflecting the LO signal back through a first lens system, wherein a transmitted portion of the optical beam is directed toward a scanned target environment;
• focus the LO signal and a target return signal at a second focal plane conjugate to the first focal plane;
• and
• mix the LO signal with the target return signal in a photodetector proximate to the second focal plane to generate target information.