Dual-wavelength real-time simultaneous phase imaging based on off-axis interferometry

Dual-wavelength interferometry is widely used in optical measurement, including the of great significance phase imaging of transparent samples. Here, we present a dual wavelength real-time phase imaging system based on off-axis interferometry with two cameras for recording complex fields transmitted through transparent samples in a wide-field and non-intrusive manner. The method of phase unwrapping based on combing dual wavelength with Fourier transform was derived in detail. The advantage of the proposed system is, compared with single-shot dual wavelength holograms methods, that it can easily extract the complex fields at both wavelengths without consideration of spectrum overlap or needing extra optic device to create lateral shearing. For phase noise, we calculated and removed the phase signal without sample in Fourier domain, which can also ensure the measured phase accurately. Experimental results on standard sample (polystyrene microspheres) demonstrated the efficiency of this imaging system. Implementation in quantitative imaging of living cells showed the time of single-shot acquisition of samples was only 0.025s, which indicated that the system can be applied to real-time and label-free identification of phase objects.