Switchable vertical/horizontal section imaging with line-field confocal optical coherence tomography

Abstract

Line-field confocal optical coherence tomography (LC-OCT) is an imaging method based on dynamically-focused line-field time-domain OCT to generate vertical section images of biological tissues with cellular spatial resolution. We demonstrate here an improvement in the LC-OCT technology that makes it possible to also generate horizontal (en face) section images, as in conventional optical coherence microscopy (OCM) or reflectance confocal microscopy (RCM). This improvement is based on the implementation of a lateral scanning device using a mirror galvanometer to scan the laser beam laterally at a given depth. The reference mirror of the interferometer is mounted on a piezoelectric transducer to generate a sinusoidal phase modulation during lateral scanning in order to extract the tomographic signal. The LC-OCT device is capable of generating either a horizontal section image at an adjustable depth in the sample, or a vertical section image at an adjustable lateral position in the sample. For both operating modes, images are acquired in real-time (8 frames per second), with real-time control of the depth/lateral position. The user can switch between the two operating modes by clicking on a button. Using a supercontinuum laser as a light source and 0.5 NA microscope objectives, the image resolution is 0.9 × 0.9 × 1.1 μm3 (x × y × z), with fields of view of 1.2 × 0.5 mm2 (x × y, horizontal) and 1.2 × 0.4 mm2 (x × z, vertical). In vivo cellular-level imaging of human skin is demonstrated for both modes of operation.