Large - field - of - view , multi - perspective Talbot microscopy

Common microscope objectives have fields of view (FOVs) of less than a few millimeters because of limits imposed by optical aberrations. To scale up the FOVs, additional lens elements and heroic design efforts are required to compensate for the aberrations, leading to reduced transmissions and higher system costs. Such FOV limitations have thus become amajor bottleneck in microscopy for large-scale imaging applications (e.g., phenotype screening and semiconductor wafer inspection). In stateof-the-art commercialized systems, for instance, the samples are transported under a conventional microscope to increase the effective FOV, but this involves extended imaging times. For our previous development of a compact microscopic imaging system,1 we did not follow a single-aperture optical design approach. Instead, we used the self-imaging effect to project a grid of excitation light spots onto a sample. This self-imaging effect—also known as the Talbot effect—was first explained by Lord Rayleigh using diffraction theory. In conventional high-throughput scanning microscope setups, the sample is directly scanned by the focal spots of a microlens array. Our Talbot microscope, which uses Talbot images of the focal spots, however, has a longer working distance and a higher phase sensitivity. A slight gradient of the global incident wavefront on the microlens array can therefore shift the Talbot focal spots by a significant distance, without introducing much off-axis aberration. In addition, the self-imaging has a self-healing effect, which generates an improved uniformity among the focal spots. By scanning the grid of focal spots across the sample in our Talbot microscope setup, we can collect a sequence of local images and thus reconstruct a high-resolution imagewith a large FOV.1 In contrast to conventional microscopes, the resolution and the FOV of our system are not coupled to each other. Using a Figure 1. Large-field-of-view, multi-perspective microscope that is based on the Talbot effect. A microlens array (white) generates a grid of Talbot focal spots for parallel scanning. Local wavefront (red) engineering enables multi-perspective imaging.