Optical object detection system

Abstract

A method and apparatus for detecting an object. A first optical signal having a first frequency is transmitted to a location on a surface of a ground. A second optical signal having a second frequency is transmitted to the location on the surface of the ground such that the first optical signal and the second optical signal overlap each other at the location on the surface of the ground. The overlap of the first optical signal and the second optical signal at the location generates a third optical signal having a difference frequency that is a difference between the first frequency and the second frequency. The third optical signal is configured to travel into the ground. A response to the third optical signal is detected. A determination is made as to whether an object is present in the ground using the response to the third optical signal.

Dependencies are inferred from the claim text.