Multi-channel overlay metrology

An overlay metrology system includes a multi-channel energy unit that selectively operates in a first mode to deliver first photons having a first wavelength to an object under test, and a second mode to deliver second photons to the object under test. The second photons have a second wavelength different from the first wavelength. The overlay metrology system further includes an electronic controller that selectively activates either the first mode or the second mode based at least in part on at least one characteristic of an object under test, and that generates the first protons or the second photons to detect at least one buried structure included in the object under test.