MIT researchers have created a silicon-based LED that is less than one micron across. This is less than one thousandth of a millimeter (mm) across. Despite the tiny size, the new LED has a high intensity, which allowed the researchers to create a holographic microscope. This advance could allow a smartphone camera to become a portable, high-resolution, lensless microscope.
Lensless microscopes are smaller than regular microscopes and less expensive because they don’t require complex, precise lens systems. They use a light source to illuminate a sample; the light is then scattered onto a CMOS digital image sensor, creating a digital hologram that a computer processes to produce an image. So, instead of a lens collecting light to form an image of an object, a sensor sends raw light data to software that reconstructs the image of the object based on the geometry of the setup.
Usually, an accurate reconstruction requires detailed knowledge of the aperture and wavelength of the source light, and sample-to-sensor distance. To avoid this difficulty, the researchers used a neural networking algorithm to reconstruct objects viewed by the holographic microscope. Neural networks are machine learning systems that rely on training data to learn and improve their accuracy over time.
The researchers found that their holographic lens provided more accurate high-resolution images than a regular optical microscope. They calculated that its resolution was approximately 20 micrometers (microns). A human skin cell is 20 to 40 microns across. The researchers say their technology can be used in existing smartphone cameras simply by modifying the phone’s silicone chip and software, converting the phone into a high-resolution microscope.
The full research report is available here.