Laser scanning confocal microscope was developed into a practical instrument in the late 1980s, where beam scanning was controlled by two galvanometer mirrors that are imaged onto the entrance pupil of an objective lens. Thus, only the direction of the incident excitation light rays is deviated at the entrance plane, while the pupil remains fully illuminated throughout the scanning. Accordingly, the focus spot of the laser beam out of the objective scans across the sample to be imaged. The beam scanning with the galvanometer mirrors has much higher scanning rates, and samples are not disturbed by vibrations, because there is no movement of sample stage. However, the beam scanning also has its own shortcomings. Because the incident angle of the laser beam on the entrance pupil of an objective lens has to vary in a certain range, associated aberrations are inevitable even with an expensive high quality objective lens. Although the invention of multiphoton confocal microscopes enhanced the detection efficiency by omitting the exit pinholes, the basic scanning mechanism remains the same as previous confocal microscopes.
Researchers at University of Michigan have developed a novel double-clad fiber based scanning confocal microscope, which possesses the advantages of both stage- and beam-scanning configurations. In contrast to conventional beam scanning, which includes changing the angle of an incident beam at an objective lens, the beam scanning of the present invention can be achieved by moving an optical fiber, which delivers a laser beam for excitation and collects signals back along the same fiber.
Low cost Simple structure Flexible Large scanning range Fast Scanning