Figure | Configuration and working principle of the FP-CSI system. (IMAGE)
Caption
Figure | Configuration and working principle of the FP-CSI system. a Optical schematic of the FP-CSI framework based on a transmissive Linnik interferometer. A near-infrared superluminescent diode (SLD) provides quasi-point illumination at various positions to generate angularly diverse illumination. The reference and test arms are symmetrically configured in a Linnik arrangement with Köhler illumination (L1, L2, L5, L6), near-infrared objectives (OBJ1–4), and relay lenses (L3, L4, L7, L8). In the test arm, a pinhole is conjugated with the objective pupil. In the reference arm, a piezoelectric transducer (PZT) modulates the optical path during axial scanning. Additionally, a compensating plate (CP) with the same thickness and material as the sample is positioned in the parfocal plane of OBJ3 and OBJ4. Interferograms are relayed by a tube lens (L9) and captured by a near-infrared InGaAs camera (Cam), which functions as the detection module. SLD, superluminescent diode; BS, beam splitter; L, lens; M, mirror; OBJ, objective lens; CP, compensation plate; Cam, near-infrared camera; PZT, piezoelectric transducer. b Setup of the experimental FP-CSI system corresponding to the schematic in a. c Conceptual illustration of angularly varying quasi-parallel illumination generated by translation of the fiber source. Larger source displacements correspond to increased incident angles and the sampling of higher spatial frequency components within the sample’s angular spectrum
Credit
Zhishan Gao et al.
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