Microendoscopes are designed to examine neurons as they fire in the brain and accordingly must be minuscule in scale yet powerful enough to produce a clear image. Most standard microendoscopes are about half a millimeter to a few millimeters in diameter and require larger, more invasive lenses to achieve high-quality imaging. While lensless microendoscopes exist, the optical fiber that scans an area of the brain pixel-by-pixel frequently bends and loses imaging ability when moved.
A new lens-free, ultra-miniaturized endoscope — the width of only a few human hairs — was developed that, when compared to a conventional lensbased microendoscope, increases the amount researchers can see and improves image quality.
To test the device, researchers examined beads in different patterns on a slide using a coded aperture — a flat grid that randomly blocks light, creating a projection in a known pattern, akin to randomly poking a piece of aluminum foil and letting light through all of the small holes. This creates a messy image but one that provides a bounty of information about where the light originates, and that information can be computationally reconstructed into a clearer image.
Additionally, the microendoscope doesn’t require movement to focus on objects at different depths; computational refocusing is used to determine where the light originated from in three dimensions. This allows the endoscope to be much smaller than traditional versions.
Looking forward, researchers will test the microendoscope with fluorescent labeling procedures in which active brain neurons are tagged and illuminated to determine the endoscope’s accuracy in imaging neural activity.