Confocal Microscopy

Confocal microscopy, first introduced to the scientific community in 1957, is an optical technique that produces “optical sections” of an object under observation. The images of tissue produced by in vivo confocal microscopy have similar resolution to images seen using traditional visible light microscopes. The VivaScope® family of medical confocal microscopes provides cellular resolution images of living skin for use in clinical procedures. Using this technique, skin and other tissues can be imaged noninvasively, in vivo, prior to biopsy, without pain or scarring.

A schematic illustration of a confocal microscope is shown in Figure 1. In operation, a virtual point source of light, derived from a laser, passes through beam-shaping optics into a beamsplitter. The beamsplitter reflects the laser beam to a scanning optics assembly that scans the beam in two orthogonal directions. The scanned beam is next directed toward the entrance pupil of an objective lens that focuses the beam to a point within the sample. Due to either natural index of refraction variations or fluorescence in the tissue, a portion of the light at the focal point propagates back toward the objective lens and is collected. This returning collected light passes back through the system and the beamsplitter to be imaged via a pinhole aperture preceding the photodetector. The pinhole aperture is matched in size to the illuminated spot. As a result, the detector receives light only from a thin, in-focus plane in the sample. Light from out-of-focus planes is rejected at the pinhole. The point source of light, the illuminated spot in the sample, and the pinhole aperture lie in optically conjugate focal planes — hence the name “confocal.”

Schematic of a Confocal Microscope

Reflectance confocal microscopy has been developed by Lucid from a scientific laboratory tool into a practical in vivo, subsurface cellular medical imaging modality. The use of this technology in clinical applications has been validated by over 100 case studies and clinical studies published in refereed scientific and medical journals. As a consequence, confocal microscopy is today becoming an accepted medical tool for routine clinical use.