Synthetic aperture-based on-chip microscopy

Abstract

Wide field-of-view (FOV) and high-resolution imaging requires microscopy modalities to have large space-bandwidth products. Lensfree on-chip microscopy decouples resolution from FOV and can achieve a space-bandwidth product greater than one billion under unit magnification using state-of-the-art opto-electronic sensor chips and pixel super-resolution techniques. However, using vertical illumination, the effective numerical aperture (NA) that can be achieved with an on-chip microscope is limited by a poor signal-to-noise ratio (SNR) at high spatial frequencies and imaging artifacts that arise as a result of the relatively narrow acceptance angles of the sensor's pixels. Here, we report, for the first time, a synthetic aperture-based on-chip microscope in which the illumination angle is scanned across the surface of a dome to increase the effective NA of the reconstructed lensfree image to 1.4, achieving e.g., ,250-nm resolution at 700-nm wavelength under unit magnification. This synthetic aperture approach not only represents the largest NA achieved to date using an on-chip microscope but also enables color imaging of connected tissue samples, such as pathology slides, by achieving robust phase recovery without the need for multi-height scanning or any prior information about the sample. To validate the effectiveness of this synthetic aperture-based, partially coherent, holographic on-chip microscope, we have successfully imaged color-stained cancer tissue slides as well as unstained Papanicolaou smears across a very large FOV of 20.5 mm 2 . This compact on-chip microscope based on a synthetic aperture approach could be useful for various applications in medicine, physical sciences and engineering that demand high-resolution wide-field imaging.