A method is presented for in situ resolution calibration of multiple feedback interferometers(MFIs) using two lasers with di?erent feedback levels simultaneously. The laser with weak optical feedback level generates half-wavelength optical fringes, whereas the laser with strong multiple feedback level generates optical nanofringes. By using this method, the number of displaced optical nano-fringes can be easily counted, and the resolution of the MFIs can be accurately determined. The integrated MFIs can be used to measure displacements and calibrate other displacement sensors.
Self-mixing interferometry （SMI） based on nanometer fringes and polarization flipping is realized. The in- terferometer comprises a single-mode He-Ne laser and a high-amplitude reflectivity feedback nfirror. The nanometer fringes are obtained by tilting the external feedback mirror. The fringe density is 35 times higher than that derived with conventional two-beam interference, and each fringe corresponds to a λ/70 displacement in external cavity length. Moreover, polarization flipping occurs when the external feedback mirror moves in the opposite direction. Such movement can be used to easily distinguish displacement direction. Experimental results show an optical resolution of displacement measurement of 9.04 nm with a range of 100 μm. The proposed placement and calibrating other SMI presents pronfising application micro-displacement sensors because prospects in precisely measuring dis- of its optical wavelength traceability.
