An Electrically Tunable Lens Implementing Axial Scan of Optical Sectioning in Three-Dimensional Structured Illumination Microscopy

Abstract

Structured illumination of optical sectioning has a wide-filed surface scan compared with point-based or line-based scanning. However, axial scan based on mechanical work-stage sacrifices the measuring time to improves the axial accuracy. Herein, an electrically tunable lens (ETL) is introduced to replace the mechanical scan in three-dimensional structured illumination microscopy (3D-SIM). The spatial light modulator (SLM), for amplitude modulation of transmitted light, generates sinusoidal grating fringes and high-precision phase shift. The ETL with focal length varying along the input current, adjusts the axial position of focusing spot on the surface of measured object. Thus, the mechanical displacement platform is not required and the five-step phase shift algorithm is modified to meet the synchronous surface and axial scan. Experimental results demonstrated that synchronous scan has a half measuring time with the same precision, and the inconsistent step length of scanning compared with calibration doesn’t affect the measurement accuracy.

Keywords: Electrically tunable lens, Optical sectioning, Structured illumination microscopy