双波长离轴数字全息成像技术研究

Digital holographic microscopy (DHM) is a commonly used technique to obtain quantitative information by measuring the phase shifts in light and changes in the refractive index of the sample. In view of the small measurement depth of the single-wavelength holographic microscopic imaging system and the phase ambiguity of the phase unwrapping algorithm, a reflective mode dual-wavelength digital holographic microscopy utilizing dichroic mirror for quantitative phase imaging of 3D structures with extended thickness range is presented, which is based on dual-wavelength off-axis interference technology. This is done by simultaneous acquisition of two off-axis interferograms, each at a different wavelength, and generation of a synthetic wavelength, allowing for an extension of the measurement range. This method is explored by numerical simulation, and then a dual-wavelength digital holographic experimental setup is constructed for imaging the polishing spots obtained by magnetorheological polishing technology and USAF target. In conclusion, the effectiveness and feasibility of the system are preliminarily verified.