Scan-less confocal phase imaging of biological samples using dual-comb microscopy

Abstract

Since confocal laser microscopy (CLM) can acquire a high-contrast three-dimensional image, it is widely used in the field of bio-imaging. However, CLM is based on point measurement, it is necessary to mechanically scan the focal spot while keeping the conjugate relation between confocal pinhole and focal spot on the sample. Since such a mechanical scanning is vulnerable to environmental disturbance such as vibration, it needs a stable measurement environment like the active anti-vibration table. Also, for imaging of living samples, CLM cannot visualize clear image because of motion blur due to the difference in scanning time, thus it is limited to get only fixed sample images. We here propose a dual optical comb microscope combining dual optical comb spectroscopy (DCS) and two-dimensional spectral encoding (2D-SE). This combination enables one-to-one correspondence between optical frequency comb (OFC) modes and image pixels. Image information is superimposed on the mode-resolved OFC spectrum waveform by 2D-SE. Simultaneously, the confocality of all the pixels is given in parallel by a single confocal pinhole. The frame rate is limited by the data acquisition time of the interferogram, imaging rate over 1000 frames/s is possible. In this paper, we demonstrate the fast confocal phase imaging of a living paramecium.