Label-free 3D optical angiography via time-frequency domain analysis of focal modulated dynamic blood flow

Accurate three-dimensional (3D) blood flow imaging with high spatiotemporal resolution and significant detection depth is essential for studying vascular structure-related diseases. In this Letter, we introduce a label-free 3D optical angiography technique via time-frequency domain analysis (TFDA) of focal modulated dynamic blood flow. First, a low-magnification telecentric lens is used for sparse axial sampling within a large depth-of-field range to obtain a coarse estimate of vascular depth. Then, based on the frequency-depth characteristics of dynamic blood flow signals, a TFDA-based focusing evaluation function is established in combination with Lambert–Beer's law, achieving a mean absolute percentage error of 2.06%. Finally, validation on a 3-day-old chicken embryo demonstrated a lateral spatial resolution of 2.95 μm and imaging time of 11.5 s for a 4.95 × 4.95 × 0.7 mm3 sample. Our method provides effective blood flow depth localization by assessing focal modulation intensity relative to focal plane and blood flow position, offering promising support for vascular disease research.