Design of a Laser Heterodyne Interferometer for 2-D Nanometer Scale Measurement

The design of a 2-D laser heterody ne interferometer w ith 2nm uncertainty
and 0. 5nm r esolutio n w ithin 50Lm measuring range is proposed in the paper. The acousto-optic modulator and frequency-stabilizing He-Ne laser will be used to obtain an orthogonal polarized frequency laser beam with less than 200 kHz frequency difference. Both polarization interfero-meters at X and Y axes are differential interferometer. Phase demodulation technology will be used for heterodyne interference signal processing.