Imaging through a weakly scattering medium by spectral-domain optical coherence microscopy with a digital phase conjugation

Abstract

A spectral-domain optical coherence microscope (SD-OCM) embedded by a digital phase conjugation is presented for high-resolution imaging of objects behind a weakly scattering medium. For high-resolution SD-OCM, keeping a narrow focusing spot even in a scattering medium is important. To compensate for the degradation of the focused spot due to the scattering, digital phase conjugation with a low-coherent light is introduced by measuring the distorted wavefront of coherent light and making wavelength conversion due to the difference between the coherent and low-coherent light beams. Experiments using a weakly scattering sheet with a scattering angle of 30 degrees showed us to improve the focused spot property and enhance the reflected intensity signal. We also demonstrate the feasibility of the system for the imaging of objects with periodic reflectance structures of 10 µm width.