Patent ID: 7330657

Claim:
A lithography system for use in optical measurement and/or inspection of sub-surface features in layered media, the system comprising: an optical multiplexer arranged to project a first optical signal onto a surface; an output optics unit arranged to receive a second optical signal, the second optical signal resulting from the first optical signal being projected onto the surface; and one or more optical demultiplexers coupled to receive the second optical signal from the output optics unit, wherein each of the one or more optical demultiplexers includes: an optical-to-electrical (OE) circuit configured to convert the second optical signal into a first electrical signal, wherein the optical signal includes a plurality of wavelengths; and a demodulating circuit, wherein the demodulating circuit is coupled to receive the first electrical signal from the OE circuit and a demodulating signal, and wherein the demodulating circuit is further configured to provide as an output a second electrical signal, wherein the demodulating signal and the second electrical signal each correspond to one of the plurality of wavelengths.