Wavelength scanning-based dual-plane lens-free phase retrieval method

High-speed imaging of large numbers of biological samples is critical in numerous biomedical applications. Conventional methods can usually only image a single sample, and for a large number of samples, they can only be imaged sequentially. Here, we propose a dual-plane phase retrieval (DPR) method in the lens-free on-chip microscopy system (LFOCM) based on partially coherent light-emitting diode (LED) illumination. Unlike previous methods, we stack two samples in the axial direction and image both layers simultaneously. Using only five coaxial holograms recorded by the sensor, the phase information of the two layers of stacked samples (including a phase resolution target and a HeLa cell sample) illuminated by LEDs, can be accurately recovered in a large field of view of 19.53 <i>mm</i>² without compromising their resolution. We quantitatively verified the effectiveness and accuracy of the method in simulations and experiments. The proposed method provides a solution for efficient sample handling in lens-free on-chip microscopy.