Time‐stretch Chromatic Confocal Microscopy for Multi‐Depth Imaging

Abstract Chromatic confocal technology has enabled multispectral information detection without any axial mechanical scanning. Especially, the chromatic confocal sensor is well applied in industry, such as device defect detection and ranging. However, for 3D imaging, chromatic confocal microscopy (CCM) still suffers from insufficient speed due to the slow refresh rate of a traditional spectrometer. To address this problem, a time‐stretch chromatic confocal microscopy (TSCCM) is presented for multi‐depth imaging. A supercontinuum laser is stretched and then focused on the sample using a home‐built chromatic lens, which disperses the laser to a different depth. The time‐of‐flight signal is collected by a high‐speed photodiode and is recorded and analyzed by a 3 GHz digitizer. A novel approach is achieved to significantly improve the speed of multi‐depth imaging with an up to 1 MHz A‐scan rate and 5 Hz volumetric imaging speed, which is an order faster compared with previous work of spectrometer‐based chromatic confocal microscopy. Multi‐depth volumetric imaging of nude‐mouse skin is performed to show the potential for biomedical applications. In this method, with its high A‐scan rate and multi‐depth imaging capability, a virtual tissue “light detection and ranging (LIDAR)” may be achieved.