In digital holographic microscopy, wavefront aberrations suppressions techniques are very matured from the perspective of the reference wave, i.e. aberrations was suppressed by numerically manipulating the reference wave. There are techniques that deal with the noises that arise from the object arm, but were mostly numerical procedure in the reconstruction stage. We found out that a better approach would be suppressing the noises, particular scattering noise from the object arm, prior to the recording stage via phase conjugation technique. By using phase conjugation technique, it is possible to trace back to the object plane where scattering is minimum; hence, achieving optical noise suppression prior to the recording stage.
In digital holography, techniques of noise suppression from the perspective of reference arm have been maturely developed. The object counterpart, however, is still in its infancy. Self-pumped phase conjugation technique which involves a BaTiO3 crystal was introduced unto reflective-type digital holographic microscopy to suppress scattering noise derived from the object arm, prior to recording stage. A phase distorter was introduced as scattering source, and signal-to-noise ratio was calculated. Furthermore, induced method was proposed to speed up the response time.
In this work, we propose an innovative method for digital holographic microscopy named as photorefractive phaseconjugation digital holographic microscopy (PPCDHM) technique based on the phase conjugation dynamic holographic process in photorefractive BaTiO3 crystal and the retrieval of phase and amplitude of the object wave were performed by a reflection-type digital holographic method. Both amplitude and phase reconstruction benefit from the prior amplification by self-pumped conjugation (SPPC) as they have an increased SNR. The interest of the PPCDHM is great, because its hologram is created by interfered the amplified phase-conjugate wave field generated from a photorefractive phase conjugator (PPC) correcting the phase aberration of the imaging system and the reference wave onto the digital CCD camera. Therefore, a precise three-dimensional description of the object with high SNR can be obtained digitally with only one hologram acquisition. The method requires the acquisition of a single hologram from which the phase distribution can be obtained simultaneously with distribution of intensity at the surface of the object.