Low-Cost, Near-Infrared, Scan-Less Portable Confocal Microscope

Abstract

Reflectance confocal microscope (RCM) is a diagnostic tool for various skin diseases, but the application of that is hampered by its high cost. In this thesis, we developed two versions of the low-cost, near-infrared scan-less portable confocal microscope. 1) High- speed RCM. We have used 840 nm central wavelength superluminescent LED as the light source. A confocal detection optics has been developed to maintain high lateral resolution even when a relatively large slit width was used. The material cost of the NIR RCM device was low as $5,200. The lateral resolution was 1.1 μm and 1.3 μm, along with the vertical and horizontal directions, respectively. Axial resolution was measured as 11.2 μm. In vivo confocal images of human forearm skin obtained at the imaging speed of 203 frames/sec clearly visualized characteristic epidermal and dermal cellular features of the human skin. 2) Speckle-free RCM. We have developed a portable confocal microscope (PCM) that uses a near-infrared (NIR) LED as the light source, and the speckle noise on the image was reduced due to the used of the spatially incoherent light source. The material cost of it is still low as ~$5,000 and weighed 1kg. The lateral resolution was measured as 1.6 μm, and axial resolution as 6.0 μm. The PCM device could visualize characteristic cellular features of human skin in vivo in a range from the stratum corneum to the superficial dermis. This capability is expected to facilitate the evaluation and clinical adoption of this low-cost diagnostic imaging tool. Dynamic imaging of blood flow in vivo was also demonstrated.