  Confocal imaging and phase imaging are powerful tools in life science
research and industrial inspection. To coherently link the two techniques with
different depth resolutions, we introduce an optical frequency comb (OFC) to
microscopy. Two-dimensional (2D) image pixels of a sample were encoded onto OFC
modes via 2D spectral encoding, in which OFC acted as an optical carrier with a
vast number of discrete frequency channels. Then, a scan-less full-field
confocal image with a depth resolution of 62.4 um was decoded from a
mode-resolved OFC amplitude spectrum obtained by dual-comb spectroscopy.
Furthermore, a phase image with a depth resolution of 13.7 nm was decoded from
a mode-resolved OFC phase spectrum under the above confocality. The phase
wrapping ambiguity can be removed by the match between the confocal depth
resolution and the phase wrapping period. The proposed hybrid microscopy
approach will be a powerful tool for a variety of applications.
