Abstract

Confocal laser scanning microscopes have been widely used in the 3-D measurement of surfaces and internal structures of samples. The absorption (transmission)-mode confocal microscope, however, has difficulty in the tomographic observation, because its 3-D optical transfer function is angularly band-limited, called the missing cone problem. In this paper, we propose a confocal transient absorption microscope that makes it possible to measure 3-D absorption distributions. This microscope is composed of the excitation and absorption distributions. The microscope is composed of the excitation and absorption monitoring optics, and these construct the confocal optical system. A sample is excited by the focused laser beam, and new absorption caused by excited-states and/or negative absorption due to depletion of a groundstate are observed by the confocal monitoring laser. We derived a 3-D OTF of the present microscope, based on the first Born approximation, and showed that the spatial frequency cutoff has no missing cone and that this characteristic is independent of the detector size. In addition, this microscope can be extended to the time-resolved measurement which is applicable to the dynamics analyses of photophysical and photochemical materials in small volumes.

© 1991 Optical Society of America