Cost-effective, DIY, and open-source digital lensless holographic microscope with distortion correction

Digital lensless holographic microscopy (DLHM) allows the design of cost-effective systems using off-the-shelf materials, making this type of lensless microscope accessible to many users worldwide. However, these materials may have a limited optomechanical performance that is aggravated due to the sought compactness and the intended cost-effective manufacturing process. This problem particularly affects the illumination source, which is of critical importance for DLHM, as it defines the optical performance of the microscope. While recent reports show that the required point source can be built from a low-cost laser diode coupled to an also low-cost aspheric lens, the resulting illumination has a distorted wavefront that limits the performance of the microscope. A simple homemade setup to correct the distortion of such illumination source and its integration into a compact, cost-effective, DIY, and open-source-certifiable digital lensless holographic microscope, is presented. The distortion-corrected DLHM is validated by imaging calibrated test targets and biological samples, achieving a 12-fold extension on the distortion-free magnification range of previous designs and a doubling of the effective spatial resolution without significant increments in its overall cost.