Abstract

Confocal laser scanning microscopy is a valuable tool for biological and biomedical imaging because of its depth discrimination. Its applicability is limited if imaging deep into scattering samples is required. Depending on the particular property of the sample, the unscattered (ballistic) light component is attenuated so much that it cannot overcome the detector noise and/or the scattered light that falls within the confocal window. Heterodyne microscopy¹ in combination with broad-bandwidth light² was used recently to improve the performance of scanning micro-scopes^3-5 in this respect. It is based on three gating mechanisms to discriminate the ballistic light from the scattered light - (i) a spatial gate, (ii) a time gate, and (iii) a coherence gate. The experimental setup consists of a Michel- son interferometer that contains the a scanning microscope in one arm. The reference arm is modulated by a piezoelectric transducer, and the signal at the Doppler frequency is detected at the interferometer output. A Ti:sapphire laser at 800 nm (cw or pulse mode) served as illumination source.

© 1995 Optical Society of America