ABSTRACT
In 1957, Marvin Minsky submitted a patent for a confocal microscope, which he had developed for imaging in brain tissue. The microscope images a thin optical slice in thick tissues without the need for physical sectioning. This is achieved by placing a pinhole in front of the detector to accept only that light that is emitted from the focus of the objective lens while rejecting light from the out-of-focus plane. A schematic for the confocal microscope is shown in Figure 1.1. The confocal microscope is by design a scanning microscope, meaning only a single point is imaged at a time, and the focus is scanned across the sample, usually in a raster scan pattern, to build up an image. In Minsky’s original design, the sample was placed on a vibrating sample holder. Other early confocal microscopes made use of white light sources and spinning pinhole disks to scan the light across the sample. Lasers now provide an inexpensive and bright monochromatic light source, and spinning disks have been replaced by scanning mirrors in many applications to steer the beam across the sample.1,2
Confocal microscopy was quickly adopted for use as a research tool in imaging biological samples, and the technique was then adapted for use in human skin, first using white light sources3-6 and then adapting the technique with laser light sources.7,8 In the 1990s, Noran Inc. (Madison, Wisconsin) made available a series of video-rate confocal microscopes. The first was based on a broadband light source and tandem spinning disk technology, which was later redesigned to better reach more parts of the skin for in vivo imaging. Later, Noran introduced an acousto-optical scanning microscope with laser illumination that provided both reflectance and fluorescent imaging. In
1997, Lucid Inc. (Rochester, New York, now Caliber ID, Andover, Massachusetts) produced a confocal microscope using a laser light source and rotating polygon mirror. Lucid introduced a microscope design, the VivaScope 1000, that could increase the field-of-view of the microscope by stitching 500 µm square images together into a mosaic. The VivaScope 1000 produced 1.5 mm mosaics of skin in vivo.
