Anyone who has ever used a microscope knows that it takes time to bring a sample into sharp focus. Each time you move the slide, the image blurs, and you have to stop and carefully turn a knob to bring everything back into clear view. For scientists and clinicians, even if the motion is semi-automated, that time quickly adds up as they work with dozens or hundreds of samples. Now a team of scientists at Caltech has developed an inexpensive robust fix for this problem that involves little more than a couple of LED lights and some physics-based processing. They describe the new autofocus technique, which they call Digital Defocus Aberration Interference (DAbI), in a paper published online on April 24 in the journal Nature Communications . The lead authors of the paper are graduate students Haowen Zhou (MS '24, PhD '26) and Shi "Josh" Zhao (MS '25), who completed the work in the lab of Changhuei Yang , the Thomas G.…