Tunable Optical High-Order Differential Microscopy for Cell Structure Detection

Abstract

Optical differential microscopy is an important tool for the detection and recognition of transparent biological objects. Among it, the first-order optical differentiation is commonly utilized to aid in fast, label-free, and contactless detection. However, the characterization of detailed contours for some smooth object areas may be limited, and a higher order operation needs to be executed. A tunable optical high-order differential microscopy is proposed and implemented, in virtue of electric-driven liquid crystal (LC). By electrically switching the working state of LC, the differential operation can be flexibly tuned in desired order, such as from zero-order to first-order and second-order differentiations. Using this scheme, clear edge-enhanced images of different-contrast objects even transparent biological cells are experimentally acquired under multi-wavelength cases. Specifically, based on the connection between high-order differential results and edge features, further gained in-depth information in the size of light spot and structure of plant cells. The beam waist radius of a laser is determined as 0.35 ± 0.002 mm, and the cell wall thickness is estimated about 3 to 5 microns. These results may open the avenue for biological imaging and microscopic measurement.