Scanning laser imagers with large working distances

The confocal Scanning Laser Ophthalmoscope exemplifies the new and exciting images available with scanning techniques, and particularly with a confocal arrangement. An ophthalmoscope might be considered a microscope whose objective is the cornea and lens of the eye. As such, it has a working distance of about 23 mm , a spherical object surface, and a resolution of 10 μm . With an external lens, the instrument can be configured as a general microscope of long working distance. We have made this change to facilitate viewing the convex surface of the eye's conjunctiva, benefitting from the great depth of focus available in a scanning system, and for observing melanotic skin lesions with the extreme rejection of scattered light available in a confocal arrangement.Scanning microscopes illuminate only one resolution element of the object at a time. Thus they encode the image information temporally - as a sequence of voltage pulses from an electro-optical detector.