Phase correction using programmable phase modulator (PPM) in optical coherence tomography

Purpose: Adaptive optics is used in optical coherence tomography (OCT) in order to improve lateral resolution based on aberration correction. Methods: Experiments were performed to compensate higher order aberrations based on wavefront sensing and correction scheme using adaptive optics. The device utilized for compensation is parallel-aligned nematic liquid crystal spatial light modulator (PAL-SLM), PPM X7550 series. Wavefront of light at the sample path was measured by using OCT for aberration correction. Since the phase information can be obtained from interferogram therefore no additional optics is used. The performance of this device is evaluated for the correction of linear tilt aberration. Further experiments were performed to correct cylindrical aberration for reflective and scattering surfaces using a simplistic method which construct phase map using OCT. This method incorporates the PAL-SLM's transfer function for the compensation of higher order aberration. Results: The RMS of phase variation of cylindrical aberration without and with adaptive optics for reflective and scattering surface is reduced from 4.1 to 0.8 and 3.46 to 2.44, respectively. Metal grid sample is used to verify the lateral resolution improvement with adaptive optics. Conclusions: Arbitrary aberration can be corrected by using PPM. Purely reflective and scattering samples indicate the performance of OCT with adaptive optics. 25 mm separation of metal lines became distinguishable after correcting aberration by adaptive optics.