Single shot cross-correlation system for longitudinal imaging in biological tissues

摘要

In this communication, we propose a non-invasive imaging setup which does not require any lateral and longitudinal scanning over the sample. The idea is to image a line over the sample surface with a laser and to collect the photons backscattered by the sample surface and the internal structures. As a result, a single shot 2D image of the sample can be obtained, one axis representing a lateral coordinate and the other one the longitudinal coordinate, e.g. the depth of the sample. To collect the backscattered light from the sample, we use a femtosecond laser source and the potential of a classical single-shot autocorrelator to make a time-to-space conversion by use of non-collinear sum frequency generation in a nonlinear crystal. With this technique, we performed single shot longitudinal imaging of an ex vivo mouse ear and in vivo human skin with a 35 μm lateral and 15 μm depth resolution in tissues. Inside the mouse ear, the epidermis, dermis and cartilage have been observed. In the in vivo human skin, the stratum corneum, the epidermis and the dermis have been observed. Especially, the epidermal-dermal junction has been clearly revealed and the thickness of the epidermis has been measured.