Phase Noise Suppression by Dual-wavelength Digital Image-plane Holographic Microscopy
Y-N. Zeng, X-Y. Chang, H. LEI, X-D. Hu and X-T. Hu
The phase noise is significantly amplified in the dual-wavelength digital holographic microscopy (DDHM) with the expansion of measuring range in single-wavelength digital holographic microscopy, resulting in the reduction of reconstructed image quality and a loss of axial resolution. The application of mathematic methods like dual-wavelength unwrapping algorithms to solve the problem above is limited because that error points may appear. We propose dual-wavelength digital image-plane holographic microscopy (DDIPHM) to suppress the phase noise in the measurement. Differently from the dual-wavelength unwrapping algorithm, DDIPHM cuts down a noise source by avoiding diffraction calculation so that the calculation error need not to be considered and the noise is decreased. The experimental results concerning a micro-step proved that the DDIPHM is an excellent method in processing noises especially in the measuring environment with relatively high noise level. The noise level in DDIPHM is about one third of that in DDHM.
Keywords: Digital holographic microscopy (DHM), image-plane holography, dual-wavelength digital image-plane holographic microscopy (DDIPHM), noise suppression, diode laser, diode pumped laser, profile measurement